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Nitrous oxide, also known as dinitrogen monoxide, laughing gas or nitrous, is an inhaled anesthetic that produces insensibility to pain preceded by mild laughing.¹ Because inhalation of small amounts of the drug provides a euphoric effect, nitrous oxide is also sometimes used as a recreational drug.¹ Nitrous oxide was discovered in 1772 by the English chemist Joseph Priestley, and it was later named by another English chemist, Humphry Davy.¹ Nitrous oxide can be used in a variety of ways, including as an anesthetic, a propellant in food aerosols and an additive to fuels to increase available oxygen in combustion.² Because it is a commonly used anesthetic, especially in dentistry,³ anesthesia providers should be familiar with its biological mechanisms, surgical applications and side effects.

Nitrous oxide is a small and simple inorganic chemical with a scientific abbreviation of N₂O.⁴ Though nitrous oxide is notably effective in analgesia, anxiolysis and anesthesia, its mechanisms of action are not well understood.² However, it is clear that nitrous oxide works through actions on neurotransmitters and their receptors. Recent research has shown that opioid receptors are involved in the analgesic effects of nitrous oxide.⁴ Actions at the γ-aminobutyric acid type A (GABA_A), which resemble actions of benzodiazepines, may be responsible for the anti-anxiety effects of nitrous oxide.⁴ When given at higher doses, it is posited that antagonism of the N-Methyl-d-aspartic acid (NMDA) receptor contributes to its anesthetic mechanism.² Nitrous oxide is eliminated from the body essentially unchanged, almost entirely through the lungs.⁵ Therefore, it undergoes almost no metabolism and has low risk for hepatic injury.⁶

Because nitrous oxide can be used for analgesia, anxiolysis and anesthesia, it has many therapeutic applications. At 20 percent concentrations, it provides analgesia that is below the anesthetic threshold.² It can be used for labor pain, in cancer patients and to relieve pain associated with a variety of medical procedures, including drug injections, colonoscopy, ophthalmologic surgeries and biopsies.⁴ A 50/50 percent nitrous oxide and oxygen mixture is used in emergency medical care for accidents and ambulance transportation.⁴ Nitrous oxide has unique effects on the physiological systems, including increased cerebral blood flow, cerebral metabolism and intracranial pressure; reduced myocardial action; and increased sympathetic nervous system activity.⁵ Unlike other volatile anesthetics, it causes a quicker respiratory rate and more skeletomuscular activity.⁵ Nitrous oxide has a short induction time, but its effects wear off rapidly.⁷ It cannot be used for long-term periods of time or in large doses due to risk of overdose.⁷ Overall, the dose-dependent effects of nitrous oxide allow anesthesia providers to use it in many contexts.

Like all general anesthetics, nitrous oxide has several side effects. Postoperative nausea and vomiting, excessive sweating, shivering, dizziness and fatigue are all common short-term side effects of nitrous oxide.^5,7 Patients who may be contraindicated to receive nitrous oxide have a history of respiratory disease, vitamin B12 deficiency, mental health conditions or substance use disorders.⁷ When used by pregnant women in the first trimester, nitrous oxide can cause damage to the embryo or fetus.⁵ Additionally, nitrous oxide can cause rapid expansion of nitrogen-containing body spaces, which can lead to organ damage.⁵ Despite its potential side effects, nitrous oxide is a safe and effective analgesic, anxiolytic and anesthetic drug.⁴

Nitrous oxide is used to reduce anxiety and pain, or to produce anesthesia at higher doses. The drug is thought to act at opioid, GABA and NMDA receptors in the brain to affect the cardiovascular, cerebral, nervous, respiratory and skeletomuscular systems. Nitrous oxide can be used in many contexts ranging from cancer pain management to general anesthesia during surgery. Despite some unpleasant side effects, nitrous oxide is safe, easy to administer, effective and rapidly reversible.⁴ Future research should focus on reducing the environmental effects of nitrous oxide, as it is a greenhouse gas that plays a role in climate change.⁵

1.         The Editors of Encyclopaedia Britannica. Nitrous oxide. In: Gregersen E, ed. Encyclopædia Britannica. Web: Encyclopædia Britannica, Inc.; 2020.

2.         Nitrous oxide. PubChem Database. Web: National Center for Biotechnology Information; 2020.

3.         American Dental Association. Nitrous Oxide. Oral Health Topics May 1, 2019; https://www.ada.org/en/member-center/oral-health-topics/nitrous-oxide.

4.         Emmanouil DE, Quock RM. Advances in understanding the actions of nitrous oxide. Anesthesia Progress. 2007;54(1):9–18.

5.         Banks A, Hardman JG. Nitrous oxide. Continuing Education in Anaesthesia Critical Care & Pain. 2005;5(5):145–148.

6.         Alai AN. Nitrous Oxide Administration. In: Burgess J, ed. Medscape. Web: WebMD LLC; June 14, 2017. 7.         Higuera V. Potential Side Effects of Nitrous Oxide. Healthline. Web: Healthline Media; August 28, 2018.

Herbal and dietary factors can affect the metabolism and transport of a wide variety of drugs.¹ For example, grapefruit has well-known interactions with more than 85 medications, which result in impaired drug metabolism and higher drug concentrations.² Fasting before anesthesia administration is a common way to avoid pulmonary aspiration, with an added benefit of avoiding the possibility of dietary interactions with anesthetic drugs.³ However, research dating back more than 20 years indicates that meals consumed days before surgery may affect anesthesia.⁴ Data show that even trace amounts of solanaceous glycoalkaloids (SGAs) found in foods such as tomatoes, potatoes and eggplants can inhibit metabolism of many common anesthetics and muscle relaxants.⁵ Knowledge of SGAs’ mechanisms of action and their effect on anesthesia is crucial to an anesthesia provider’s practice. 

Glycoalkaloids are nitrogen-containing compounds containing steroids and monosaccharaides.⁶ They are biologically active secondary metabolites, meaning that they are produced by organisms but not necessary for their growth, development and reproduction.⁷ SGAs, such as solanine⁸ and tomatine,⁹ are glycoalkaloids that are naturally produced in the Solanaceae plant family. Solenaceous vegetables and fruits include Solanum (potato and eggplant), Lycopersicon (tomato), and Capsicum (pepper),¹⁰ as well as cherries and beets.⁸ Though the SGAs in these vegetables and fruits are said to have anticarcinogenic effects,¹¹ high concentrations of SGAs are unsafe for human consumption.¹² SGA toxicity leads to inhibition of acetylcholinesterase, the enzyme that normally breaks down acetylcholine.¹³ Too much acetylcholine affects the parasympathetic nervous system (used for the “rest and digest” function), causing symptoms such as increased secretions, burning in the throat, bronchoconstriction (airway constriction), bradycardia (slow heart rate), vomiting, diarrhea and abdominal cramping.^8,14 Severe cases are even associated with muscle spasms, paralysis, confusion, headache, drowsiness, hallucinations, loss of sensation, fever, jaundice, dilated pupils and hypothermia.^8,14 While SGA doses of 200 to 400 milligrams for adults and 20 to 40 milligrams for children are necessary for toxic symptoms, it is estimated that commercial potatoes have a solanine concentration of only 0.2 milligrams per gram.⁸ However, potatoes that have been exposed to light and turned green contain high amounts of solanine, and cooking them does not reduce this amount.¹⁵ It is important to keep in mind the role of SGAs in acetylcholine poisoning before consuming SGA-containing foods. 

Not only can SGAs cause parasympathetic nervous system issues when consumed in excess, but they can also affect the pharmacokinetics of anesthetic drugs.⁴ In fact, this can occur when SGAs are consumed in moderate amounts, days before surgery.⁴ The effects of preoperative SGA consumption on anesthesia were first discovered in 1998 by researchers and anesthesiologists at the University of Chicago.¹⁶ This effect is due to SGAs’ inhibitory effects on acetylcholinesterase and another enzyme, butyrylcholinesterase.¹⁷ While acetylcholinesterase maintains healthy nerve and muscle function, butyrylcholinesterase is found in the blood and is responsible for the breakdown of a variety of anesthetic drugs.¹⁶ The scientists found SGA-induced enzymatic inhibition, and subsequent reduced metabolism of common anesthetics and muscle relaxants, due to moderate potato consumption days before surgery.⁵ According to Jonathan Moss, the principal investigator, the study helped explain why dosing models based on weight and height were off by 50 to 100 percent in some patients.¹⁶ A study by McGehee et al. used in vitro samples in the laboratory and rabbit models to show that potato SGAs slowed metabolism of mivacurium, which is a muscle relaxant and neuromuscular blocking agent metabolized by butyrylcholinesterase.¹⁸ In a more recent review, Krasowski et al. found that SGAs may cause atypical genetic variation in butyrylcholinesterase in humans and influence anesthetic drug metabolism.¹⁷ Finally, findings from Bestas et al.’s human study suggested that potatoes eaten the meal before preoperative fasting could prolong the duration of succinylcholine-induced neuromuscular block and delay recovery from anesthesia.¹⁹ Evidently, SGAs may interfere with metabolism of anesthetic drugs through enzymatic inhibition. 

It is well known that herbal and dietary factors beyond age, weight, height and sex may affect drug metabolism. Glycoalkaloids from the Solanaceae plant family, which includes potatoes, tomatoes and peppers, can inhibit enzymes in the human body and cause toxicity of certain biological transmitters. Through their enzymatic blockade, SGAs can also interfere with the metabolism of anesthetic drugs and muscle relaxants. Anesthesiology professionals should be sure to consider a patient’s preoperative diet when choosing dosages. However, given a lack of human studies, more research is needed to assess the exact effects of dietary SGAs on anesthesia and necessary dosing adjustments. 

1. Harris RZ, Jang GR, Tsunoda S. Dietary effects on drug metabolism and transport. Clinical Pharmacokinetics. 2003;42(13):1071–1088. 

2. Bailey DG, Dresser G, Arnold JMO. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? Canadian Medical Association Journal. 2013;185(4):309–316. 

3. American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration. Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures. Anesthesiology: The Journal of the American Society of Anesthesiologists. 2017;126(3):376–393. 

4. Meals days before surgery may affect anesthesia: Potatoes prolong anesthetic action. The Forefront Magazine. Web: The University of Chicago Medical Center; October 20, 1998. 

5. Voelker R. No Potatoes Before Surgery. JAMA. 1998;280(20):1735. 

6. Glycoalkaloid. ScienceDirect. Web: Elsevier B.V.; 2020. 

7. Monfil VO, Casas-Flores S. Chapter 32—Molecular Mechanisms of Biocontrol in Trichoderma spp. and Their Applications in Agriculture. In: Gupta VK, Schmoll M, Herrera-Estrella A, Upadhyay RS, Druzhinina I, Tuohy MG, eds. Biotechnology and Biology of Trichoderma. Amsterdam: Elsevier; 2014:429–453. 

8. Izawa K, Amino Y, Kohmura M, Ueda Y, Kuroda M. 4.16: Human–Environment Interactions—Taste. In: Liu H-W, Mander L, eds. Comprehensive Natural Products II. Oxford: Elsevier; 2010:631–671. 

9. Osman SF. Glycoalkaloids of the Solanaceae. In: Swain T, Kleiman R, eds. The Resource Potential in Phytochemistry. Boston, MA: Springer US; 1980:75–96. 

10. Rubatzky VE, Yamaguchi M. Tomatoes, Peppers, Eggplants, and Other Solanaceous Vegetables. In: Rubatzky VE, Yamaguchi M, eds. World Vegetables: Principles, Production, and Nutritive Values. Boston, MA: Springer US; 1997:532–576. 

11. Friedman M. Chemistry and anticarcinogenic mechanisms of glycoalkaloids produced by eggplants, potatoes, and tomatoes. Journal of Agricultural and Food Chemistry. 2015;63(13):3323–3337. 

12. Kuete V. Health Effects of Alkaloids from African Medicinal Plants. In: Kuete V, ed. Toxicological Survey of African Medicinal Plants: Elsevier; 2014:611–633. 

13. Bushway RJ, Savage SA, Ferguson BS. Inhibition of acetyl cholinesterase by solanaceous glycoalkaloids and alkaloids. American Potato Journal. 1987;64(8):409–413. 

14. Lott EL, Jones EB. Cholinergic Toxicity. StatPearls. Treasure Island, Florida: StatPearls Publishing; June 4, 2019. 

15. Cantwell M. A review of important facts about potato glycoalkaloids. Perishables Handling Newsletter. 1996;87:26–27. 

16. Moss JR. Research Uncovers First Known Link Between Diet and Anesthesia. ASA Annual Meeting,. Web: American Society of Anesthesiologists; October 19, 1998. 

17. Krasowski MD, McGehee DS, Moss J. Natural inhibitors of cholinesterases: Implications for adverse drug reactions. Canadian Journal of Anesthesia. 1997;44(5 Pt 1):525–534. 

18. McGehee Daniel S, Krasowski Matthew D, Fung Dennis L, Wilson B, Gronert Gerald A, Moss J. Cholinesterase Inhibition by Potato Glycoalkaloids Slows Mivacurium Metabolism. Anesthesiology: The Journal of the American Society of Anesthesiologists. 2000;93(2):510–519. 

19. Bestas A, Goksu H, Erhan OL. The effect of preoperative consumption of potatoes on succinylcholine-induced block and recovery from anesthesia. Journal of Clinical Monitoring and Computing. 2013;27(6):609–612.

The electronic medical record (EMR) has the potential to improve patient care through electronic documentation and viewing, prescription and test ordering, care management reminders and clinician-patient messaging.¹ EMRs allow health care providers to collect data on patients’ health conditions and quality of care and share these data with other clinicians.² Some researchers also argue that EMR systems may provide better security for patients’ health information than do paper records.³ Individual EMRs provide the basis for electronic health record (EHR) systems, which allow patients’ health information to follow them through various geographic areas and medical specialties.⁴ Not only do EMRs serve as an electronic version of the patient’s health history, but they can also be used to enhance patient safety through tools that help providers monitor care.⁵ EMR systems are becoming increasingly relevant to anesthesiology, with uses such as data collection, prevention of medical errors and crisis resource management.⁵ Anesthesia providers should be aware of the myriad capabilities of EMR in anesthesiology and data on EMR efficacy in the field.

EMR has become commonplace in anesthesiology due to technological advances, economic circumstances and complex clinical care needs.⁶ For example, EMR helps providers keep thorough records, report on patient care and record clinical outcomes in order to support value-based payment strategies.⁶ Many EMR systems include training and education resources that allow anesthesia providers to learn more about contemporary technologies.⁷ Additionally, the automation of EMR services frees up staff’s time and gives patients autonomy through online scheduling, electronic intake forms and digital refill requests.⁷ Patients can also engage in their own health care through interactive apps and patient portals.⁷ Specifically in anesthesiology, alerts associated with EMR can remind practitioners to avoid certain drugs due to patient contraindications (e.g., high risk for nausea and vomiting) or to respond to events (e.g., blood transfusion) with medications.⁵ Because anesthesia providers have various intraoperative events and tasks to balance, EMR can be a helpful resource for reducing their cognitive load and potential for error.⁵ The centralization of helpful information, checklists and cognitive aids can be especially important during intraoperative crises.⁵ Furthermore, real-time, objective data collection allows anesthesia providers to evaluate their practices and make evidence-based improvements.⁸ The variety of capabilities of EMR, ranging from education to crisis management to data collection, offer many advantages to the anesthesia provider.

Given that more than 75 percent of physicians in the United States use EMR⁹ and federal mandates require electronic medical charting,¹⁰ paperless charting is not likely to return.⁷ When integrating EMR into their practices, anesthesia providers should evaluate the efficacy and best uses of EMR systems for anesthesiology. A study by Goudra et al. found that use of Epic, a widely-used EMR system, led to significant intraoperative time saving and reduced medical costs.¹⁰ However, the same study showed that pressure to input data in real time—usually to avoid litigation—was a distraction from patient care, ironically leading to compromises in patient safety.¹⁰ A case study by Baier et al. found that the EMR system used in their facility did not have straightforward documentation options.¹¹ Redundancies, omissions, inconsistent format of medical record fields and a lack of hard stops interfered with documentation of airway management data.¹¹ On the other hand, Hincker et al. found that EMR alerts led to improvements in the intraoperative administration of repeated doses of cefazolin, a multidose antibiotic.¹² In another study, Jang et al. showed that electronic anesthesia records were more complete than paper records, likely due to automatic transfer of items from past records.¹³ Evidence on the usefulness of EMR in anesthesiology is inconsistent, and often depends on the clinician’s knowledge¹¹ or proper utilization of EMR technologies.⁷

EMR systems are here to stay, and anesthesia providers will need to incorporate these new technologies into their practices. EMR reduces anesthesia providers’ cognitive loads during surgery, helps them prepare for crises and allows them to interact easily with their patients. While the automated functions of EMR may improve an anesthesiology practitioner’s work, electronic records can also distract from the patient. Future research should directly assess the effects of EMR on patient care and outcomes in anesthesiology. Additionally, engineers should collaborate with anesthesia providers to tailor EMR systems to the field of anesthesiology.

1.         Balas EA, Austin SM, Mitchell JA, Ewigman BG, Bopp KD, Brown GD. The clinical value of computerized information services. A review of 98 randomized clinical trials. Archives of Family Medicine. 1996;5(5):271–278.

2.         Terry AL, Ryan BL, McKay S, et al. Towards optimal electronic medical record use: Perspectives of advanced users. Family Practice. 2018;35(5):607–611.

3.         Barrows RC, Jr., Clayton PD. Privacy, Confidentiality, and Electronic Medical Records. Journal of the American Medical Informatics Association. 1996;3(2):139–148.

4.         Garets D, Davis M. Electronic medical records vs. electronic health records: Yes, there is a difference. HIMSS Analytics. January 26, 2006:1–14.

5.         Tanoubi I. The electronic medical record in anesthesiology: A standard of quality healthcare and patient safety. Canadian Journal of Anesthesia/Journal canadien d’anesthésie. 2017;64(7):693–697.

6.         Cohen NH. Electronic Health Records: Understanding the Implications for Anesthesia Practice. ASA Newsletter. 2015;79(5):36–39.

7.         Parvus-Teichmann C, Ranasinghe CT. Electronic Medical Records: Promises, Pitfalls, and Pearls for Pain Physicians. ASRA News. February 2017;17(1):19–21.

8.         Rozental O, White RS. Anesthesia Information Management Systems: Evolution of the Paper Anesthetic Record to a Multisystem Electronic Medical Record Network That Streamlines Perioperative Care. Journal of Anesthesia History. 2019;5(3):93–98.

9.         Hsiao CJ, Hing E. Use and characteristics of electronic health record systems among office-based physician practices: United States, 2001–2012. NCHS Data Brief. December 2012(111):1–8.

10.       Goudra B, Singh PM, Borle A, Gouda G. Effect of introduction of a new electronic anesthesia record (Epic) system on the safety and efficiency of patient care in a gastrointestinal endoscopy suite-comparison with historical cohort. Saudi Journal of Anaesthesia. 2016;10(2):127–131.

11.       Baier AW, Snyder DJ, Leahy IC, Patak LS, Brustowicz RM. A Shared Opportunity for Improving Electronic Medical Record Data. Anesthesia & Analgesia. 2017;125(3):952–957.

12.       Hincker A, Ben Abdallah A, Avidan M, Candelario P, Helsten D. Electronic medical record interventions and recurrent perioperative antibiotic administration: A before-and-after study. Canadian Journal of Anesthesia. 2017;64(7):716–723. 13.       Jang J, Yu SH, Kim C-B, Moon Y, Kim S. The effects of an electronic medical record on the completeness of documentation in the anesthesia record. International Journal of Medical Informatics. 2013;82(8):702–707.

Nonpharmacologic treatments provide alternatives to medication for issues ranging from chronic insomnia¹ to hypertension.² Among nonpharmacologic treatments are those involving electrical stimulation, which is administered to treat soft-tissue injuries,³ cardiac arrest⁴ and a variety of other health conditions. The field of anesthesiology includes such electrical stimulation in the form of electroanalgesia for acute and chronic pain relief.⁵ Articles from the 1970s cite electrical stimulation to treat chronic⁶ or postoperative⁷ pain, but the use of electroanalgesia began centuries ago.⁵ Renewed interest in electrical stimulation for analgesia is due to interest in understanding the physiological bases of pain perception and transmission, as well as in finding alternatives to traditional analgesic drugs.⁵ Anesthesia providers should familiarize themselves with the history, mechanisms and usefulness of electroanalgesia in order to provide their patients with a nonpharmacologic alternative.

In 1965, Melzack and Wall proposed the Gate Control Theory, which states that pain perception is due to large-diameter afferent (i.e., sensory) fibers in the dorsal column of the spinal cord, and analgesia is considered “closing the gate.”⁸ Based on this theory, Shealy et al.’s 1967 study first reported use of an implantable device for direct spinal cord stimulation (SCS) to provide analgesia.⁹ The efficacy of SCS, which is posited to modulate pain perception, is controversial to this day.⁵ However, it is currently used to treat a variety of chronic pain syndromes.⁵ Throughout the years, research has approached pain management techniques such as deep brain stimulation (DBS), peripheral nerve stimulation (PNS), percutaneous electrical nerve stimulation (PENS), percutaneous neuromodulation therapy (PNT), transcutaneous electrical nerve stimulation (TENS), transcutaneous acupoint electrical stimulation (TAES), H-wave therapy (HWT), interferential current therapy (ICT), Piezo-electric current therapy (PECT) and electroacupuncture (EA), all with varying degrees of success.⁵ The history of electroanalgesia is long and complex, and it has contributed to the numerous electroanalgesic techniques used today.

Because there are so many kinds of electroanalgesia, the mechanisms of each type are varied. Some electroanalgesics, such as SCS, DBS and transcranial magnetic stimulation target pain perception in the central nervous system.⁵ For example, DBS is administered to the periventricular and periaqueductal gray matter in the mesencephalic-diencephalic transition zone, ventroposterolateral-medial nucleus of the thalamus, internal capsule and motor cortex of the brain.⁵ The supposed mechanism of action of DBS, like SCS, is decreasing pain transmission along sensory pathways, and it is also believed to release endogenous endorphins.⁵ Other electroanalgesia techniques, including PNS, PENS, PNT, TENS, TAES, HWT, ICT, PECT and EA, target the peripheral nervous system and localized pain areas to electrically “massage” nerves and tissues and reduce pain at the site.⁵ Anesthesia providers may use electroanalgesia that either changes the patient’s pain perception or targets painful areas directly depending on type of pain and length of treatment.

The most important issue for an anesthesiology practitioner considering electroanalgesia is its clinical efficacy. For one, a widely used nonpharmacologic treatment for chronic pain, radiofrequency ablation therapy, was recently reported to have no clinical benefit.¹⁰ On the other hand, some evidence shows that ultrasound-guided PENS may serve as useful alternatives to nerve block medications, without the limited duration of action, potential for infection or risk of dislodgement.¹¹ EA has also been reported to effectively trigger neuronal firing, as well as the release of neurotransmitters and endogenous opioids within the central nervous system.¹⁰ The concrete pain-reducing effects of EA and TENS was found in a clinical study by Eriksson and Sjölund.¹² Yet this study was published in 1976, and most recent studies on EA use animal models such as rats^13,14 and horses.¹⁵ Clearly, the literature on the usefulness of electroanalgesia is lacking.

In the throes of the opioid epidemic, nonmedication, nonaddictive alternatives for pain management are appealing to anesthesia providers.¹⁶ Electroanalgesia has been used and studied for centuries, and it can affect a patient’s pain perception or provide relief to a painful area. However, data are limited on the effectiveness of various electroanalgesia techniques. More high-powered human studies are needed to warrant the integration of electroanalgesia into the practice of anesthesiology.

1.         Morin CM, Hauri PJ, Espie CA, Spielman AJ, Buysse DJ, Bootzin RR. Nonpharmacologic Treatment of Chronic Insomnia. Sleep. 1999;22(8):1134–1156.

2.         Meles E, Giannattasio C, Failla M, Gentile G, Capra A, Mancia G. Nonpharmacologic treatment of hypertension by respiratory exercise in the home setting. American Journal of Hypertension. 2004;17(4):370–374.

3.         Wilson DH. Treatment of Soft-tissue Injuries by Pulsed Electrical Energy. British Medical Journal. 1972;2(5808):269–270.

4.         Hopps JA, Bigelow WG. Electrical treatment of cardiac arrest: A cardiac stimulator-defibrillator. Surgery. 1954;36(4):833–849.

5.         White PF, Li S, Chiu JW. Electroanalgesia: Its Role in Acute and Chronic Pain Management. Anesthesia & Analgesia. 2001;92(2):505–513.

6.         Long DM. External electrical stimulation as a treatment of chronic pain. Minnesota Medicine. 1974;57(3):195–198.

7.         VanderArk GD, McGrath KA. Transcutaneous electrical stimulation in treatment of postoperative pain. The American Journal of Surgery. 1975;130(3):338–340.

8.         Melzack R, Wall PD. Pain mechanisms: A new theory. Science (New York, N.Y.). 1965;150(3699):971–979.

9.         Shealy CN, Mortimer JT, Reswick JB. Electrical Inhibition of Pain by Stimulation of the Dorsal Columns: Preliminary Clinical Report. Anesthesia & Analgesia. 1967;46(4):489–491.

10.       White PF, Elvir Lazo OL, Galeas L, Cao X. Use of electroanalgesia and laser therapies as alternatives to opioids for acute and chronic pain management. F1000Res. 2017;6:2161.

11.       Gabriel RA, Ilfeld BM. Percutaneous peripheral nerve stimulation and other alternatives for perineural catheters for postoperative analgesia. Best Practice & Research Clinical Anaesthesiology. 2019;33(1):37–46.

12.       Eriksson M, Sjölund B. Acupuncturelike Electroanalgesia in TNS-Resistant Chronic Pain. In: Zotterman Y, ed. Sensory Functions of the Skin in Primates: Pergamon; 1976:575-581.

13.       Qi D, Wu S, Zhang Y, Li W. Electroacupuncture analgesia with different frequencies is mediated via different opioid pathways in acute visceral hyperalgesia rats. Life Sciences. 2016;160:64–71.

14.       Wang J, Gao Y, Chen S, et al. The Effect of Repeated Electroacupuncture Analgesia on Neurotrophic and Cytokine Factors in Neuropathic Pain Rats. Evidence-Based Complementary and Alternative Medicine. 2016;2016:11.

15.       Sheta E, Ragab S, Farghali H, El-Sherif A. Successful Practice of Electroacupuncture Analgesia in Equine Surgery. Journal of Acupuncture and Meridian Studies. 2015;8(1):30–39.

16.       White PF. An Alternative Approach to Solving the Opioid Epidemic: Expanding the Use of Non-Pharmacologic Techniques for Acute and Chronic Pain Management. Journal of Molecular Biology and Methods. 2018;1(1).

General anesthesia can be crucial to easing a patient’s pain and anxiety during a procedure.¹ However, general anesthesia often comes with an extensive recovery time and unpleasant side effects.¹ Depending on the type of procedure and anesthetic agent, a patient may have postoperative sleepiness, nausea, chills, vomiting and throat soreness.¹ The rebound effects of anesthesia and sedation can be strong, impacting a patient’s ability to drive, to ride public transportation alone and to make judgments.¹ Usually, clinicians recommend that patients who have undergone general anesthesia refrain from driving or doing activities alone for 24 hours after a procedure.² Anesthesiology researchers have investigated the effects of different types of anesthesia on recovery, and developed strategies that can help alleviate postoperative side effects.

Some studies have compared the quality of recovery from various types of anesthetic agents. For example, a study by Moro et al. found that for 130 patients undergoing otorhinolaryngological surgery, the quality of recovery from a remifentanil-sevoflurane combination was not significantly different from recovery from a remifentanil-propofol combination.³ That is, there were no group differences in incidence of hypothermia, nausea, vomiting, pain intensity or postoperative morphine use.³ Another study found that desflurane was associated with a decreased rate of postoperative respiratory depression when compared to isoflurane.⁴ Meanwhile, a study by Jung et al. compared different dosages of sevoflurane to determine optimal anesthetic depth for interventional radiology.⁵ Though a lower dose of sevoflurane led to faster recovery and better hemodynamic rebound after anesthesia, it was also associated with more patient movement during the procedure.⁵ Finally, a review by Patel et al. showed no evidence suggesting that anesthesia types influence postoperative delirium in older patients, but the literature was lacking.⁶ More research is needed to compare the differences between various anesthetic drugs’ postoperative side effects.

Other researchers have approached using perioperative strategies to reduce postoperative side effects. For one, Viitanen et al. found that premedication with midazolam caused children treated with sevoflurane to have fewer sleep disruptions the night after surgery.⁷ However, another study showed that side effects of propofol were not different for patients pretreated with midazolam versus control patients, suggesting that midazolam exhibits different effects depending on the type of anesthesia used.⁸ Some more conclusive studies involved the use of dexmedetomidine, a drug used frequently in anesthesiology and intensive care settings.⁹ One study found that dexmedetomidine administered through continuous infusion (compared to placebo) prevented postoperative nausea and vomiting (PONV), as well as reduced side effects such as bradycardia and hypotension.⁹ Another showed that, though efficacy of dexmedetomidine differed depending on dosage, it was effective in controlling cough, agitation, hypertension, tachycardia and shivering upon recovery from anesthesia.¹⁰ Yet another study found that compared to placebo, dexmedetomidine reduced incidence of PONV and postoperative analgesic use.¹¹ Weingarten et al. found that introduction of a new anesthetic protocol—including triple antiemetic prophylaxis and less midazolam use—was associated with decreased postoperative respiratory depression and decreased PONV.⁴ In a study of a nonmedication solution to unpleasant anesthesia recovery, Grech et al. found that intraoperative electroacupuncture reduced postoperative hyperglycemia and lowered postoperative stress hormones.¹² A study by Jungquist et al. identified a preventive solution to postoperative side effects with electronic monitoring devices, which used machine learning to predict patients’ postoperative opioid-induced respiratory depression (OIRD).¹³ Taken together, these studies show that medication, alternative treatments and monitoring can help reduce postoperative side effects.

Rebound from general anesthesia can be unpleasant, often including PONV and immune and stress responses. While more research is needed to assess how different anesthetic drug affect quality of recovery, some preventive and intraoperative solutions may make recovery easier. Future studies should further explore optimizing anesthetic drug dosing and providing nonmedication strategies to alleviate postoperative discomfort.

1.         American Society of Anesthesiologists. Preparing for surgery: Recovery. When Seconds Count… 2019; https://www.asahq.org/whensecondscount/preparing-for-surgery/recovery/.

2.         Chung F, Kayumov L, Sinclair David R, Edward R, Moller Henry J, Shapiro Colin M. What Is the Driving Performance of Ambulatory Surgical Patients after General Anesthesia? Anesthesiology: The Journal of the American Society of Anesthesiologists. 2005;103(5):951–956.

3.         Moro ET, Leme FCO, Noronha BR, Saraiva GFP, de Matos Leite NV, Navarro LHC. Quality of recovery from anesthesia of patients undergoing balanced or total intravenous general anesthesia. Prospective randomized clinical trial. Journal of Clinical Anesthesia. 2016;35:369–375.

4.         Weingarten TN, Bergan TS, Narr BJ, Schroeder DR, Sprung J. Effects of changes in intraoperative management on recovery from anesthesia: A review of practice improvement initiative. BMC Anesthesiology. 2015;15(1):54.

5.         Jung YS, Han Y-R, Choi E-S, et al. The optimal anesthetic depth for interventional neuroradiology: Comparisons between light anesthesia and deep anesthesia. Korean Journal of Anesthesiology. 2015;68(2):148–152.

6.         Patel V, Champaneria R, Dretzke J, Yeung J. Effect of regional versus general anaesthesia on postoperative delirium in elderly patients undergoing surgery for hip fracture: A systematic review. BMJ Open. 2018;8(12):e020757.

7.         Viitanen H, Annila P, Viitanen M, Tarkkila P. Premedication with Midazolam Delays Recovery After Ambulatory Sevoflurane Anesthesia in Children. Anesthesia & Analgesia. 1999;89(1):75–79.

8.         Bevan JC, Veall GRO, Macnab AJ, Ries CR, Marsland C. Midazolam Premedication Delays Recovery After Propofol Without Modifying Involuntary Movements. Anesthesia & Analgesia. 1997;85(1):50–54.

9.         Jin S, Liang DD, Chen C, Zhang M, Wang J. Dexmedetomidine prevent postoperative nausea and vomiting on patients during general anesthesia: A PRISMA-compliant meta analysis of randomized controlled trials. Medicine (Baltimore). 2017;96(1):e5770.

10.       Aouad MT, Zeeni C, Al Nawwar R, et al. Dexmedetomidine for Improved Quality of Emergence From General Anesthesia: A Dose-Finding Study. Anesthesia & Analgesia. 2019;129(6):1504–1511.

11.       Zhu M, Wang H, Zhu A, Niu K, Wang G. Meta-Analysis of Dexmedetomidine on Emergence Agitation and Recovery Profiles in Children after Sevoflurane Anesthesia: Different Administration and Different Dosage. PLoS One. 2015;10(4):e0123728.

12.       Grech D, Li Z, Morcillo P, et al. Intraoperative Low-frequency Electroacupuncture under General Anesthesia Improves Postoperative Recovery in a Randomized Trial. Journal of Acupuncture and Meridian Studies. 2016;9(5):234–241.

13.       Jungquist CR, Chandola V, Spulecki C, et al. Identifying Patients Experiencing Opioid-Induced Respiratory Depression During Recovery From Anesthesia: The Application of Electronic Monitoring Devices. Worldviews on Evidence-Based Nursing. 2019;16(3):186–194.

Breastfeeding can have long-lasting effects on a child and maternal health. Benefits of breastfeeding include prevention of child infections and malocclusion (i.e., imperfect teeth positioning), increases in intelligence and probable reduction in the incidence of diabetes.¹ Making breastfeeding universal could prevent an estimated 823,000 annual deaths in children younger than five years old and 20,000 annual deaths from breast cancer.¹ That said, there are many substances that can affect a mother’s ability to breastfeed and/or can be transmitted to the infant with dangerous effects.² Thus, it is important for medical providers to assess a new mother’s breastfeeding status before prescribing medications. Specifically, anesthesia providers should account for the effects of anesthetic drugs on a mother and child before, during and after a procedure. 

Anesthesia can affect a mother’s ability to breastfeed in a variety of ways. Generally, a mother can resume breastfeeding once she is awake, stable and alert after anesthesia induction.³ However, anesthetic agents used during and after labor can have adverse effects on breastfeeding initiation.⁴ Research shows that longer labors, instrumented deliveries, Cesarean section and separation of mother and infant after birth may increase risk of difficulty with breastfeeding initiation.^5-7 Anesthesia used during labor may influence any one of these factors,⁸ and some anesthetic drugs can directly make breastfeeding more difficult.⁵ A study by Zuppa et al., for example, found that epidural anesthesia in labor reduced likelihood of successful breastfeeding initiation in mothers who received hands-off care after delivery.⁹ However, the same study found that a good start to lactation was guaranteed by hands-on care after delivery, regardless of whether or not anesthesia was administered during labor.⁹ This indicates that proper pre- and postpartum care may outweigh any deleterious effects intraoperative anesthesia may have on breastfeeding.^4,9 Indeed, pain and suffering during labor can inhibit proper initiation of breastfeeding, suggesting that the reduction in pain caused by anesthesia could ultimately balance out the effects of the drug itself.⁴ Overall, the effects of anesthesia on initiation of breastfeeding are often conflicting and not well studied.⁴ 

The effects of anesthetic drugs on a newborn, however, are more concrete. If anesthesia is administered neuraxially (i.e., injected into fatty tissue or cerebrospinal fluid surrounding spinal nerve roots), it will not affect the infant.³ Thus, even opioids such as fentanyl and morphine can be used safely for labor or Cesarean section in patients who intend to breastfeed, as long as they are administered as intrathecal or epidural anesthetics.³ However, anesthesiologists are still responsible for understanding pharmacokinetics, limiting dosage and monitoring vital signs in mothers and infants.³ For general anesthesia and postpartum pain management, anesthesiology practitioners should avoid codeine and meperidine and should use hydromorphone with caution.³ Low-dose morphine can be used safely postpartum,³ but all opioids used for labor can affect the newborn’s normal reflex to suckle at the breast after birth.⁴ The ability to cross the blood-milk duct membranes differs among anesthetic agents, and an anesthesia provider should ensure that infants will not be affected before administering medication to a breastfeeding mother.² Though data on drug transfer to breast milk are limited¹⁰ and special precautions are rarely warranted for routine anesthetic drugs,¹¹ anesthesiologists must be aware of the potential harm of postoperative medications.³ 

Initiation and continuation of breastfeeding are important to maternal and child health. Anesthesia providers should be aware of the effects anesthetic drugs can have on a mother’s ability to breastfeed and on a child’s development. That said, the literature on anesthesia in breastfeeding is profoundly lacking. Future studies should assess the effects of various types of local and general anesthesia on breastfeeding initiation and breast milk concentrations. Without information on anesthesia’s relationship to breastfeeding, it could be difficult for an anesthesiologist to make decisions about a breastfeeding mother’s perioperative care. 

1. Victora CG, Bahl R, Barros AJD, et al. Breastfeeding in the 21st century: Epidemiology, mechanisms, and lifelong effect. The Lancet. 2016;387(10017):475–490. 

2. National Institutes of Health. Drugs and Lactation Database (LactMed). Bethesda, MD: National Library of Medicine (US); 2006–2019. 

3. Cobb B, Liu R, Valentine E, Onuoha O. Breastfeeding after Anesthesia: A Review for Anesthesia Providers Regarding the Transfer of Medications into Breast Milk. Translational Perioperative and Pain Medicine. 2015;1(2):1–7. 

4. Montgomery A, Hale TW, The Academy of Breastfeeding Medicine. ABM Clinical Protocol #15: Analgesia and Anesthesia for the Breastfeeding Mother, Revised 2012. Breastfeeding Medicine. 2012;7(6):547–553. 

5. Rajan L. The impact of obstetric procedures and analgesia/anaesthesia during labour and delivery on breast feeding. Midwifery. 1994;10(2):87–103. 

6. Tamminen T, Verronen P, Saarikoski S, Goransson A, Tuomiranta H. The influence of perinatal factors on breast feeding. Acta Paediatrica Scandinavica. 1983;72(1):9–12. 

7. Patel RR, Liebling RE, Murphy DJ. Effect of operative delivery in the second stage of labor on breastfeeding success. Birth (Berkeley, Calif.). 2003;30(4):255–260. 

8. Howell CJ. Epidural versus non-epidural analgesia for pain relief in labour. The Cochrane Database of Systematic Reviews. 2000(2):Cd000331. 

9. Zuppa AA, Alighieri G, Riccardi R, et al. Epidural analgesia, neonatal care and breastfeeding. Italian Journal of Pediatrics. 2014;40(1):82. 

10. Nitsun M, Szokol JW, Saleh HJ, et al. Pharmacokinetics of midazolam, propofol, and fentanyl transfer to human breast milk. Clinical Pharmacology and Therapeutics. 2006;79(6):549–557. 

11. Chu TC, McCallum J, Yii MF. Breastfeeding after Anaesthesia: A Review of the Pharmacological Impact on Children. Anaesthesia and Intensive Care. 2013;41(1):35–40. 

Regional anesthesia has enjoyed many advancements in its practice worldwide, but the most revolutionary advancement within the field has been the use of ultrasound.  Ultrasound has been shown to lead to more successful regional blocks over stimulation-based or paresthesia-based techniques^1,2.  The use of ultrasound is able to provide safer regional anesthesia by helping providers avoid potential complications such as intravascular injection, nerve injury, or damage to local structures.   Since the adoption of ultrasound as the gold standard for regional anesthesia during the past few decades, performing nerve blocks has become significantly safer and increasingly useful for a wide variety of procedures.

A significant progression in ultrasound-guided regional anesthesia has been improved needle technology.  More echogenic needles can provide better visualization of the nerve with respect to the injection site, giving a greater chance for block success³.  This is accomplished by either creating dimples in the needle, forming a rough needle surface, or adjusting the polymeric makeup of the needle coating to reflect ultrasound beams better⁴.  These changes to the needle tip may work better for certain types of blocks, but they may prove disadvantageous for others.  For example, a needle reflective for a specific frequency range of ultrasound required for deep blocks may not be so advantageous when a different frequency is utilized for superficial blocks.  To this end, some needle manufacturers have introduced the ability to perform electromagnetic-guided needle-tip tracking in conjunction with ultrasound⁵.  While needle tip tracking has been found to improve provider confidence in an adequate block, this technology is very new and still has yet to gain widespread regulatory approval. 

In addition to improved needle quality for imaging, ultrasound technology itself has advanced far enough to significantly facilitate the ease and efficacy of regional anesthesia.  Over the past several years, transducer quality, improved image resolution, and better beam formation have all drastically increased the utility of ultrasound in providing accurate sonoanatomy for safe and effective blocks⁴.  In addition, ultrasound technology has ventured into newer modalities that may provide additional ease to performing regional anesthesia; three-dimensional ultrasound imaging can help elucidate anatomic structures easier, facilitate more precise needle movements, and map the spread of local anesthetic around the target area.

The use of ultrasound guidance of regional anesthesia has come a long way, and many more helpful advances are coming into widespread use.  Machine learning may play a key role in imaging processing, with nearly complete minimization of artifact and shadowing in order to provide better visualization of structures.  In addition, machine learning may eventually become advanced enough to automatically identify specific anatomic structures in real-time to aid the provider in reaching the intended target.  Through improvement of beam formation and image resolution to better penetrate structures with poor acoustic transmission, even neuraxial anesthesia can receive immense benefit from ultrasound guidance.  The use of automation may also be a key development in the advancement of regional anesthesia, helping providers maneuver the ultrasound probe or needle in order to administer the most precise block possible.  The practice of ultrasound-guided regional anesthesia has come so far since its first reported use in 1994¹; it is extremely likely that in another 25 years, the field will see immense improvements in patient safety, success rates, and utility for numerous clinical situations.

1.         Gray AT. Ultrasound-guided regional anesthesia: current state of the art. Anesthesiology. 2006;104(2):368-373, discussion 365A.

2.         Kapral S, Greher M, Huber G, et al. Ultrasonographic guidance improves the success rate of interscalene brachial plexus blockade. Reg Anesth Pain Med. 2008;33(3):253-258.

3.         Hebard S, Hocking G. Echogenic technology can improve needle visibility during ultrasound-guided regional anesthesia. Reg Anesth Pain Med. 2011;36(2):185-189.

4.         Henderson M, Dolan J. Challenges, solutions, and advances in ultrasound-guided regional anaesthesia. BJA Education. 2016;16(11):374-380.

5.         Kåsine T, Romundstad L, Rosseland LA, et al. Needle tip tracking for ultrasound-guided peripheral nerve block procedures-An observer blinded, randomised, controlled, crossover study on a phantom model. Acta Anaesthesiol Scand. 2019.

6.         Clendenen NJ, Robards CB, Clendenen SR. A standardized method for 4D ultrasound-guided peripheral nerve blockade and catheter placement. Biomed Res Int. 2014;2014:920538.

While it is possible to place catheters at various anatomic locations, they are not equivalent in terms of analgesic benefit. Likewise, analgesia during the infusion has been demonstrated in several high-quality studies, however positive effect on chronic postoperative pain is lacking in evidence. Interscalene and sciatic catheters provide very potent and satisfactory analgesia, whereas supraclavicular, axillary, and transversus abdominus plane catheters have not shown the same level of effect. Placing an infraclavicular catheter has shown promise from an analgesia standpoint, however the dose required often causes complete anesthesia and motor block of the limb. Femoral and lumbar plexus infusions have shown similar effect, causing weakness that may interfere with the recovery process. Studies have reported a fall risk as high as 5 times that of controls when continuous femoral block is placed.^4,5 That is not to say these blocks should not be performed, however the patient should be counseled regarding the possible result of placing a PNC in these locations.

As with any invasive procedure, the risks and benefits must be considered, weighed, and disclosed to the patient. Due to the dependence of results of any procedure on provider technique, it is difficult make overarching statements regarding the incidence and prevalence, but severe complications are very rarely reported. Minor complications are reported at a rate similar to that of single-shot peripheral nerve blocks.^2,4 Infusion failure has been reported anywhere from 0.5% to 26%, however it must again be noted that these studies exhibit significant heterogeneity in terms of technique, equipment, catheter location, and infusate regimen. If it difficult to generalize based on these limitations however it should be noted that the adoption of ultrasound guidance has significantly decreased the rate of reported block failure.

Nerve damage is a potential complication that may be anxiety provoking for the patient, however studying the true incidence of neuropathy attributable to use of regional anesthesia is difficult. This is partly due the fact that the surgery itself, tourniquet time, and the prolonged positioning without protective reflexes serve as risk factors for nerve damage. What is known from currently available evidence is that the rate of neuropathy is generally low and symptoms in most cases resolve within a year without treatment.⁵ Prior nerve injury in the planned location or history of neuropathy are relative contraindications due to the increased risk of recurrence or worsening of neuropathy.³ Professional athletes are not at increased risk, however it may be prudent to forego regional techniques given their dependence on reliable return of neuromuscular function and coordination for their occupation.

A relatively common complication of any perineural catheter is dislodgement or malpositioning leading to block failure, which often leads the provider to take extra measures to secure the catheter at the insertion point, and at the skin, either coiled, glued, anchored, or tunneled to prevent tension on the catheter being transmitted to the tip. There has also been a single report of leakage from the catheter site, causing contamination of the surgical field intraoperatively, but skin adhesives like 2-Octyl cyanoacrylate have been found to decrease the incidence of leakage.⁵ Extremely rare, however potentially fatal, is migration of the catheter into an intravascular, epidural, intrathecal, or intrapleural location.

Another potentially devastating complication of the use of an indwelling catheter of any type is infection, although the reported incidence is less than 1%. Patients at significant risk include those who are immunosuppressed or otherwise immunocompromised, male gender, diabetics, obese patients, victims of trauma, and those being treated in the ICU. Maintenance of a perineural catheter for more than 48hrs is a modifiable risk factor, while other factors such as aseptic drawing of medication, catheter tunneling, and use of aseptic dressings have not shown significance.⁹ Axillary, femoral, and even interscalene catheters have been reported to have higher risk of infection. Peri-catheter hematoma is also of concern, specifically in patients maintained on anticoagulants at the time of placement, manipulation, or removal of a neuraxial or “deep” perineural catheter, however there is conflicting evidence regarding this risk in most peripheral blocks. Some researchers have recommended substituting erector spinae, paravertebral, or transversus abdominis plane catheters for an epidural when concern for coagulopathy exists.

Finally, there are alternatives to a perineural catheter ranging from opioid-based analgesia, wound infiltration, cryoanalgesia, acupuncture, percutaneous nerve stimulation, single shot peripheral block with liposomal bupivacaine, or single shot neuraxial, each with its own unique set of risks and benefits.⁵ Careful selection of appropriate patients for peripheral nerve catheter has shown great success in minimizing the consumption of opioids, an emerging priority in healthcare policy as efforts are increased to eradicate the opioid epidemic. Moreover, research and innovation continue to expand the list of approved indications for placement of peripheral nerve catheter. There are still many questions which remain unanswered, heralding a need for on-going experimentation to expand our collective understanding of continuous regional anesthesia.

References

1. Ansbro FP. A method of continuous brachial plexus block. The American Journal of Surgery. 1946;71(6):716-722. https://www.sciencedirect.com/science/article/pii/000296104690219X. doi: 10.1016/0002-9610(46)90219-X.

2. Borgeat A, Ekatodramis G, Kalberer F, Benz C. Acute and nonacute complications associated with interscalene block and shoulder Surgery: A prospective study. Anesthes. 2001;95(4):875-880. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1944139. Accessed Dec 5, 2019.

3. Chang A, White BA. Peripheral nerve blocks. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2019. http://www.ncbi.nlm.nih.gov/books/NBK459210/. Accessed Dec 10, 2019.

4. Ilfeld B. Continuous peripheral nerve blocks: A review of the published evidence. Anesthesia & Analgesia. 2011;113(4):904-925. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0b013e3182285e01.

5. Ilfeld B. Continuous peripheral nerve blocks: An update of the published evidence and comparison with novel, alternative analgesic modalities. Anesthesia & Analgesia. 2017;124(1):308-335. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0000000000001581.

6. Joshi G, Gandhi K, Shah N, Gadsden JC, Corman SL. Peripheral nerve blocks in the management of postoperative pain: Challenges and opportunities. Journal of Clinical Anesthesia. 2016;35:524-529. http://www.ncbi.nlm.nih.gov/pubmed/27871587. Accessed Nov 25, 2019.

7. Luyet C, Seiler R, Herrmann G, Hatch GM, Ross S, Eichenberger U. Newly designed, self-coiling catheters for regional anesthesia-an imaging study. Reg Anesth Pain Med. 2011;36(2):171-176. https://rapm.bmj.com/content/36/2/171-176. Accessed Dec 12, 2019. doi: 10.1097/AAP.0b013e31820d431a.

8. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth. 2005;94(1):7-17. https://academic.oup.com/bja/article/94/1/7/379332. Accessed Dec 2, 2019. doi: 10.1093/bja/aei002.

9. Nicolotti D, Iotti E, Fanelli G, Compagnone C. Perineural catheter infection: A systematic review of the literature. J Clin Anesth. 2016;35:123-128. Accessed Nov 25, 2019. doi: 10.1016/j.jclinane.2016.07.025.

10. Schnabel A, Meyer-Frießem CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: A meta-analysis of randomized controlled trials. British Journal of Anaesthesia. 2013;111(4):564-572. https://www.sciencedirect.com/science/article/pii/S0007091217323486. doi: 10.1093/bja/aet196. 11. Toledano RD, Tsen LC. Epidural catheter DesignHistory,innovations,and clinical implications. Anesthes. 2014;121(1):9-17. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1917668. Accessed Nov 25, 2019. doi: 10.1097/ALN.0000000000000239.

The technique for placement of nerve catheters has evolved over time, initially being done using anatomic landmarks and either subjective paresthesia, fascial “click” or fluoroscopic visualization. By the 1970s, the use of nerve stimulation was popularized and by 1978 the first use of ultrasound guidance for nerve block was reported by LaGrange et al.⁸ Unfortunately, the adequacy of analgesia obtained using either technique is operator and situation dependent. Whether the nerve is localized using a stimulating needle, stimulating catheter, or sonographically there remains the possibility of inadequate pain control in spite of adequate muscle stimulation or nerve visualization.

The location of the catheter tip is also of concern when placing and evaluating PNCs. The catheter tip may easily be mispositioned or become dislodged too far from the nerve to provide adequate effect postoperatively. However, if a large initial bolus was given through the catheter or via needle prior to advancing the catheter, mispositioning may not be noticed until the bolus clears and the infusion is started postoperatively. No studies have elucidated an optimal distance to thread the catheter past the tip, however increased coiling and knotting has been reported with catheters >5cm beyond the needle tip, thus the current recommendation is not to exceed 5cm distance beyond the needle.⁴ In 2011, there was a report of self-coiling catheters being developed to maintain close proximity of the catheter to the nerve, however these were not approved for human use.

After numerous studies comparing the effectiveness of nerve stimulation and ultrasound in placement of nerve catheters, meta-analysis was performed in 2013 demonstrating clear superiority for ultrasound guidance in terms of success rate and avoidance of vascular puncture. Time required to place a catheter and procedural pain were also found to be decreased.¹⁰

The local anesthetic most commonly infused through PNCs is either bupivacaine or ropivacaine, which are long-acting amide local anesthetics, however any of the available local anesthetics can be used, as long as an appropriate dosing regimen is followed. Opiates are also added frequently to the infusate to supplement a neuraxial blockade given the decreased likelihood of adverse side effects when the opioid Mu receptors are modulated directly at the level of the dorsal horn. Delivery regimens are based on a set bolus dose, continuous rate, or combination of the two. Bolus-only regimens will clearly decrease the total consumption of anesthetic, however there is evidence of superior analgesia when sciatic catheters are maintained on a basal infusion. Regarding the infusion system, electronic pumps are reported to be very consistent in terms of delivery of the selected basal rate (5% error), whereas elastomeric systems are found to over-infuse during the first 8 hours and the final hours of infusion.⁴ In addition, elastomeric devices cannot be refilled outside of a pharmacy, lack the option for bolus dosing, and lack any alarm mechanism. The major upside to an elastomeric pump is that is simplifies ambulatory dosing of a PNC in the postoperative period.

First reported in 1997, ambulatory continuous perineural catheters, have become much more common in recent years with the push to decrease healthcare cost and length of stay. Because local anesthetic is being administered in a non-monitored setting, care must be taken with patient selection to avoid those at high risk of poor drug clearance, infection, or misuse. It should be noted that young age is not a contraindication, as studies have found no increase in rate of complications among pediatric patients. Fall risk must also be considered as patients receiving ropivacaine via PNC have been found to have increased incidence of falls. There has also been report of PNC masking pain from a new metatarsal fracture after a fall. Patients receiving ambulatory infusions via perineural catheter should be followed closely, however there is currently no standard recommendation regarding a method or frequency.⁴ It is common practice to call patients daily while the catheter is in place to monitor analgesia, site appearance, remaining local anesthetic, and pump function. Patients are also given instructions on how to remove the catheter at home and are commonly instructed via telephone during the removal process.

References

1. Ansbro FP. A method of continuous brachial plexus block. The American Journal of Surgery. 1946;71(6):716-722. https://www.sciencedirect.com/science/article/pii/000296104690219X. doi: 10.1016/0002-9610(46)90219-X.

2. Borgeat A, Ekatodramis G, Kalberer F, Benz C. Acute and nonacute complications associated with interscalene block and shoulder Surgery: A prospective study. Anesthes. 2001;95(4):875-880. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1944139. Accessed Dec 5, 2019.

3. Chang A, White BA. Peripheral nerve blocks. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2019. http://www.ncbi.nlm.nih.gov/books/NBK459210/. Accessed Dec 10, 2019.

4. Ilfeld B. Continuous peripheral nerve blocks: A review of the published evidence. Anesthesia & Analgesia. 2011;113(4):904-925. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0b013e3182285e01.

5. Ilfeld B. Continuous peripheral nerve blocks: An update of the published evidence and comparison with novel, alternative analgesic modalities. Anesthesia & Analgesia. 2017;124(1):308-335. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0000000000001581.

6. Joshi G, Gandhi K, Shah N, Gadsden JC, Corman SL. Peripheral nerve blocks in the management of postoperative pain: Challenges and opportunities. Journal of Clinical Anesthesia. 2016;35:524-529. http://www.ncbi.nlm.nih.gov/pubmed/27871587. Accessed Nov 25, 2019.

7. Luyet C, Seiler R, Herrmann G, Hatch GM, Ross S, Eichenberger U. Newly designed, self-coiling catheters for regional anesthesia-an imaging study. Reg Anesth Pain Med. 2011;36(2):171-176. https://rapm.bmj.com/content/36/2/171-176. Accessed Dec 12, 2019. doi: 10.1097/AAP.0b013e31820d431a.

8. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth. 2005;94(1):7-17. https://academic.oup.com/bja/article/94/1/7/379332. Accessed Dec 2, 2019. doi: 10.1093/bja/aei002.

9. Nicolotti D, Iotti E, Fanelli G, Compagnone C. Perineural catheter infection: A systematic review of the literature. J Clin Anesth. 2016;35:123-128. Accessed Nov 25, 2019. doi: 10.1016/j.jclinane.2016.07.025.

10. Schnabel A, Meyer-Frießem CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: A meta-analysis of randomized controlled trials. British Journal of Anaesthesia. 2013;111(4):564-572. https://www.sciencedirect.com/science/article/pii/S0007091217323486. doi: 10.1093/bja/aet196.

11. Toledano RD, Tsen LC. Epidural catheter DesignHistory,innovations,and clinical implications. Anesthes. 2014;121(1):9-17. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1917668. Accessed Nov 25, 2019. doi: 10.1097/ALN.0000000000000239.

A continuous peripheral nerve block (CPNB) or peripheral nerve catheter (PNC) is essentially an indwelling tubular device inserted via a needle through the skin, with orifices at each end for injection and delivery of local anesthetic around nerve or within a fascial plane known to contain traversing neural elements. Since its development, there has been a multitude of iterations and modifications, creating what is now an essential device in the prevention and treatment of postoperative pain after major surgery. The use of catheters for the infusion of local anesthetic extends back to 1931, when Dr. Eugen Aubrel, a Romanian professor of obstetrics and gynecology, used a silk ureteral catheter to deliver a continuous lumboaortic plexus block for the first stage of labor. Subsequently, the indwelling Lemmon needle was developed by Dr. William Lemmon and later modified by Drs. Robert Hingson and Waldo Edwards to provide a method of delivering continuous caudal anesthesia via a malleable stainless-steel needle attached to a syringe via long tubing.

After reports of the limitations associated with the modified Lemmon needle were published, including migration and breakage of the needle, Dr. Edward Tuohy applied the ureteral catheter to continuous spinal anesthesia in the 1940s. At the time, the catheter was delivered via a 15-gauge Barker needle, which upon removal was sequentially sterilized but not reused more than ten times per Dr. Tuohy’s recommendation. He subsequently developed the Tuohy needle, which is still in use today. Nylon catheters later replaced their silk predecessors after a case of meningitis was reported by Dr. Samuel Manalan in that same decade.

Several modifications to needle size, type, and technique were made over the following years until Dr. Manuel Curbelo, a Cuban anesthesiologist who had visited the Mayo Clinic three years prior, described an adaptation of the Tuohy needle to achieve peridural passage of an indwelling catheter in 1949 to provide anesthesia for surgeries below the neck. Drs. Charles Flowers, Louis Hellman, and Robert Hingson collaborated later that year to describe the use of a continuous epidural catheter, threaded through a 16-gauge Tuohy needle into the second lumbar interspace, for vaginal and cesarean deliveries, another technique which remains in use today, with minor modifications. The continuous peripheral nerve block was first described in 1946 by F. Paul Ansbro for upper extremity surgeries¹. By 1951, Sarnoff and Sarnoff reported using a continuous nerve block to treat intractable hiccups, demonstrating the diversity of experimentation with regional anesthesia during that fruitful period in the history of anesthesia.⁴

Regarding the current practice in management of perineural catheters, there are several considerations and potential complications which must be accounted for in addition to the standard principles used to guide management of all nerve blocks. The indications for use of PNCs are essentially the same regarding surgical anesthesia, with the addition that the catheter allows for continuous delivery of dilute local anesthetic for extended postoperative analgesia. This is useful for cases where postoperative pain is expected to be persistently high and will be inadequately controlled on intravenous and/or oral analgesics. PNCs are also useful in situations where standard dosing of opioid analgesics is contraindicated or poorly tolerated (e.g. opioid tolerant or active substance abuse, severe PONV, severe OSA). In addition, continuous regional techniques have been used to treat vasospasm (Raynaud’s phenomenon, digital injury/reimplantation), CRPS, phantom limb pain, terminal cancer pain, and trigeminal neuralgia. While there are several useful clinical applications for CPNB, the most rigorously tested of these is for perioperative pain control. There remains a paucity of level-I studies evaluating the effectiveness of PNCs in these other applications, however there are several trials underway to this effect. Given the increased risk for potential complications from an indwelling device, PNCs are typically preserved for cases when single-shot nerve blocks along with other non-invasive analgesics will be inadequate and the benefit of placing a catheter outweighs the potential risks. Absolute contraindications to placement of a PNC are few and include patient refusal, allergy to local anesthetic, or inability to cooperate with procedure. Relative contraindications include active infection or preexisting nerve deficit in the intended site or distribution, and coagulopathy, especially when the planned block is in a non-compressible location.

References

1. Ansbro FP. A method of continuous brachial plexus block. The American Journal of Surgery. 1946;71(6):716-722. https://www.sciencedirect.com/science/article/pii/000296104690219X. doi: 10.1016/0002-9610(46)90219-X.

2. Borgeat A, Ekatodramis G, Kalberer F, Benz C. Acute and nonacute complications associated with interscalene block and shoulder Surgery: A prospective study. Anesthes. 2001;95(4):875-880. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1944139. Accessed Dec 5, 2019.

3. Chang A, White BA. Peripheral nerve blocks. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2019. http://www.ncbi.nlm.nih.gov/books/NBK459210/. Accessed Dec 10, 2019.

4. Ilfeld B. Continuous peripheral nerve blocks: A review of the published evidence. Anesthesia & Analgesia. 2011;113(4):904-925. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0b013e3182285e01.

5. Ilfeld B. Continuous peripheral nerve blocks: An update of the published evidence and comparison with novel, alternative analgesic modalities. Anesthesia & Analgesia. 2017;124(1):308-335. insights.ovid.com. Accessed Nov 25, 2019. doi: 10.1213/ANE.0000000000001581.

6. Joshi G, Gandhi K, Shah N, Gadsden JC, Corman SL. Peripheral nerve blocks in the management of postoperative pain: Challenges and opportunities. Journal of Clinical Anesthesia. 2016;35:524-529. http://www.ncbi.nlm.nih.gov/pubmed/27871587. Accessed Nov 25, 2019.

7. Luyet C, Seiler R, Herrmann G, Hatch GM, Ross S, Eichenberger U. Newly designed, self-coiling catheters for regional anesthesia-an imaging study. Reg Anesth Pain Med. 2011;36(2):171-176. https://rapm.bmj.com/content/36/2/171-176. Accessed Dec 12, 2019. doi: 10.1097/AAP.0b013e31820d431a.

8. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth. 2005;94(1):7-17. https://academic.oup.com/bja/article/94/1/7/379332. Accessed Dec 2, 2019. doi: 10.1093/bja/aei002.

9. Nicolotti D, Iotti E, Fanelli G, Compagnone C. Perineural catheter infection: A systematic review of the literature. J Clin Anesth. 2016;35:123-128. Accessed Nov 25, 2019. doi: 10.1016/j.jclinane.2016.07.025.

10. Schnabel A, Meyer-Frießem CH, Zahn PK, Pogatzki-Zahn EM. Ultrasound compared with nerve stimulation guidance for peripheral nerve catheter placement: A meta-analysis of randomized controlled trials. British Journal of Anaesthesia. 2013;111(4):564-572. https://www.sciencedirect.com/science/article/pii/S0007091217323486. doi: 10.1093/bja/aet196. 11. Toledano RD, Tsen LC. Epidural catheter DesignHistory,innovations,and clinical implications. Anesthes. 2014;121(1):9-17. https://anesthesiology.pubs.asahq.org/article.aspx?articleid=1917668. Accessed Nov 25, 2019. doi: 10.1097/ALN.0000000000000239.