Postoperative Delirium (POD)

POD, emergence delirium, and POCD are three different things - Emergence delirium is confined to the emergence period, is most prevalent in healthy children and younger adults, and is triggered by endotracheal tubes, catheters, noise, light, and pain. POD comes after initial recovery from anesthesia, hours to days out, and primarily affects older patients with multiple comorbidities. Postoperative cognitive dysfunction (POCD) is a subtle decline in higher-level processing and memory found on neuropsychological testing weeks to months later. They form a continuum, but prevention and treatment differ for each, so the distinction is not academic.

Screen with a tool, in the right order - Establish arousability first; the Richmond Agitation-Sedation Scale is the standard instrument for level of arousal, and a deeply sedated or unarousable patient cannot be assessed for delirium at all. Once arousal is established, assess the content with a validated instrument - the CAM-ICU is the one in common use. Without routine screening, hypoactive delirium simply goes undiagnosed.

Know the predisposing profile before you start - Age over 70, dementia that is often clinically unrecognized, prior delirium, functional disability and preoperative functional limitation, mild cognitive impairment, poor vision and hearing, and alcohol use disorder. Male sex and abnormal baseline laboratory values also carry increased risk.

And the precipitants you control - Medication side effects account for up to 39% of delirium cases. Anticholinergic drugs and benzodiazepines are the repeat offenders; the 2019 Updated AGS Beers Criteria lists agents with harmful effects in older adults including those likely to cause delirium, and cumulative anticholinergic burden can be totaled rather than eyeballed. Untreated pain, hypoxia, hypercapnia or hypocapnia, inadequate perfusion, dehydration, metabolic derangement, infection, sleep deficit, indwelling catheters, and an unfamiliar environment fill out the list.

Do not run deep - Episodes of deep anesthesia at BIS below 20 were associated with delirium in a randomized trial of 1,155 patients, and the incidence of delirium is lower with light sedation than with deep sedation.

Dexmedetomidine, with real dosing - Low-dose is described as an infusion of 0.1 to 0.4 mcg/kg/hr or a bolus under 0.5 mcg/kg; high-dose as 0.5 to 0.7 mcg/kg/hr or a bolus over 0.5 mcg/kg. Both ranges reduce POD and POCD, and the evidence favors an infusion, or infusion plus bolus, over bolus alone. It works by damping the inflammatory response, mimicking non-REM stage 3 sleep, and cutting opioid requirement.

Dose dexmedetomidine down in older adults - The FDA recommends reducing the loading dose and infusion in this population because of hypotension risk; for procedural sedation, 0.5 mcg/kg over 10 minutes rather than 1 mcg/kg. There is no FDA guidance for continuous infusion rates or adjunct dosing in older adults. Avoid it entirely in atrioventricular block, sick sinus syndrome, or refractory bradycardia.

Treat the pain, spare the opioid - The AGS guideline names pain as a known cause of delirium and says inadequate pain control alone is a risk factor, but opioids also contribute to neurocognitive dysfunction. Optimize with nonopioid analgesics rather than choosing between the two.

Prevention beats treatment, and the AGS says so explicitly - Pharmacologic treatment of POD can worsen and prolong outcomes, so the AGS Expert Panel puts prevention first. Orient the patient to the perioperative area, let them keep hearing aids and glasses until surgery and get them back promptly, and reorient them on emergence.

Withdrawal is on the differential - Alcohol and benzodiazepine withdrawal both cause POD. Get the actual intake history preoperatively, not a yes-or-no.

Work the differential before you medicate - Rule out the physiologic causes first: hypoxia, inadequate reversal of neuromuscular blockade, pain, and metabolic derangement. Then anticholinergic toxicity, identified by anhidrosis, mydriasis, constipation, and bladder fullness, treated with physostigmine. Then serotonin toxicity by the Hunter criteria - diaphoresis, muscle rigidity, clonus, ocular clonus, hyperreflexia, tremor, shivering, vomiting, diarrhea - treated by removing the offending drug plus supportive care, benzodiazepines, and cyproheptadine. The wrong treatment makes the presenting condition worse. Delirium that persists beyond the usual recovery window does respond to antipsychotics.

The cost is not small - POD carries a 7% to 10% increased risk of 30-day mortality and adds 2 to 3 hospital days, with up to three times higher morbidity and mortality at 6 months. Average cost is $2,947 per affected patient. The 2017 Mayo Clinic Study of Aging found older adults who develop POD or POCD are three times more likely to end up with permanent cognitive impairment or dementia.

Postoperative delirium (POD) is an acute disturbance of attention, cognition, and awareness that develops over a short period, fluctuates, and differs from the patient's baseline. DSM-5 frames it as reversible neuronal dysfunction driven by a systemic insult. It appears anywhere from 10 minutes after anesthesia through the first postoperative week, and it is the most common postoperative complication in patients 65 and older.

Three subtypes exist: hyperactive, hypoactive, and mixed. Hypoactive delirium - lethargy and decreased responsiveness - is the most common and the one that gets missed, written off as residual anesthetic. Incidence runs from 5% in low-risk patients having low-risk surgery to 50% in high-risk patients and procedures, and 70% to 80% across an ICU stay. Surgical trauma releases interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha, which act through dopaminergic, GABAergic, and cholinergic pathways on a brain with increased blood-brain barrier permeability, neuronal inflammation, apoptosis, and reduced plasticity.