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.
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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.