Disclaimer: This article is intended solely for informational and educational purposes only. It does not constitute medical advice.
Postoperative delirium is an acute disturbance in attention, awareness, and cognition that develops over hours to days after surgery and can fluctuate over time. It is more common among older adults and patients undergoing major or prolonged procedures. Clinically, delirium is categorized as hyperactive, hypoactive, or mixed. Although hyperactive delirium is more conspicuous, hypoactive postoperative delirium is frequently missed, making recognition of both phenotypes an important component of perioperative care.
Hyperactive delirium is characterized by agitation, restlessness, increased motor activity, emotional lability, hallucinations, and combative behavior. Patients may repeatedly attempt to remove intravenous lines or surgical drains, climb out of bed, or interfere with postoperative treatment. Autonomic activation, including tachycardia, hypertension, and diaphoresis, may also occur. Because these behaviors are readily apparent, hyperactive delirium is more likely to trigger immediate evaluation. However, clinicians should distinguish delirium from other causes of postoperative agitation, including inadequately treated pain, hypoxemia, urinary retention, medication effects, alcohol or benzodiazepine withdrawal, and emergence phenomena.
Hypoactive delirium is characterized by decreased psychomotor activity, lethargy, reduced spontaneous speech, withdrawal, and diminished interaction with the environment. Patients may appear sleepy, depressed, or simply fatigued following anesthesia. Subtle inattention or disorientation may be the only noticeable manifestations. Consequently, hypoactive delirium can remain unrecognized unless clinicians actively screen for it, which is particularly relevant in older postoperative patients, in whom sedation and expected postoperative fatigue can mask clinically significant cognitive changes.
Mixed postoperative delirium, characterized by alternating periods of hyperactivity and hypoactivity, is another possible outcome. A patient may be agitated and confused overnight but somnolent and minimally interactive the following morning. This fluctuation highlights the importance of repeated postoperative assessments rather than relying on a single examination.
Risk factors for postoperative delirium include advanced age, baseline cognitive impairment, frailty, multiple comorbidities, sensory impairment, and emergency or major surgery. Perioperative contributors include poorly controlled pain, hypoxemia, hypotension, infection, metabolic abnormalities, sleep disruption, dehydration, and exposure to psychoactive medications. Benzodiazepines and medications with anticholinergic properties are particularly important modifiable contributors, while excessive opioid exposure may further increase risk in susceptible patients.
Diagnosis should incorporate a validated screening tool rather than clinical impression alone. The Confusion Assessment Method (CAM) and CAM-ICU are commonly used and assess acute or fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. For anesthesiologists, routine postoperative screening is particularly important for patients with multiple risk factors or prolonged ICU and hospital stays.
Management focuses first on identifying and correcting reversible precipitants. Oxygenation, hemodynamics, pain control, hydration, electrolyte abnormalities, infection, urinary retention, and medication exposure should be systematically assessed. Nonpharmacologic interventions—including frequent reorientation, early mobilization, preservation of nighttime sleep, use of hearing aids and glasses, adequate hydration and nutrition, and minimizing unnecessary lines and restraints—are foundational. Antipsychotics or other sedating medications should not be used routinely to treat delirium and are generally reserved for severe agitation that threatens patient or staff safety or prevents essential medical therapy.
For the perioperative clinician, a key distinction between hypoactive and hyperactive postoperative delirium is visibility rather than pathophysiology. Hyperactive delirium demands attention because of disruptive behavior, whereas hypoactive delirium requires active surveillance to detect. Recognizing both phenotypes early allows anesthesiologists and surgical teams to identify reversible precipitants, minimize iatrogenic contributors, and implement supportive measures before delirium leads to prolonged hospitalization, functional decline, or other adverse outcomes.
References
- Marcantonio ER. Delirium in hospitalized older adults. N Engl J Med. 2017;377(15):1456-1466. DOI: 10.1056/NEJMcp1605501
- Inouye SK, Westendorp RGJ, Saczynski JS. Delirium in elderly people. Lancet. 2014;383(9920):911-922. DOI: 10.1016/S0140-6736(13)60688-1
- Aldecoa C, Bettelli G, Bilotta F, et al. European Society of Anaesthesiology evidence-based and consensus-based guideline on postoperative delirium. Eur J Anaesthesiol. 2017;34(4):192-214. DOI: 10.1097/EJA.0000000000000594
- American Geriatrics Society Expert Panel on Postoperative Delirium in Older Adults. American Geriatrics Society abstracted clinical practice guideline for postoperative delirium in older adults. J Am Geriatr Soc. 2015;63(1):142-150. DOI: 10.1111/jgs.13281
- Evered L, Scott DA, Silbert B, Maruff P. Postoperative cognitive dysfunction is difficult to define, measure, and prevent: the emperor’s new clothes or wisest choice? Br J Anaesth. 2011;106(suppl 1):i41-i50. DOI: 10.1213/ANE.0b013e318215217e