Signs and Symptoms of Postoperative Delirium
Postoperative delirium presents in three distinct motoric subtypes that vary dramatically in clinical presentation: hypoactive (withdrawn, decreased motor activity), hyperactive (agitation, heightened arousal, aggression), and mixed (fluctuating between both), with hypoactive delirium being the most commonly missed because it is frequently misattributed to dementia. 1, 2
Core Clinical Features
The cardinal features that define postoperative delirium include:
- Acute onset with fluctuating course - symptoms wax and wane throughout the day, distinguishing it from stable dementia 3
- Inattention - inability to focus, maintain, or shift attention; this is the hallmark feature and must be present for diagnosis 3, 4
- Altered level of consciousness - ranging from hyperalert to stuporous 1
- Disorganized thinking - rambling, irrelevant conversation, unclear or illogical flow of ideas 1
Motoric Subtype Presentations
Hypoactive Delirium (Most Commonly Missed)
- Lethargy and decreased responsiveness - patient appears withdrawn or sedated 2
- Reduced motor activity - minimal movement, appears to be "sleeping more" 1
- Quiet confusion - subtle disorientation that nursing staff may not recognize 1
Critical pitfall: Hypoactive delirium remains undiagnosed in more than half of clinical cases because it mimics depression or is wrongly attributed to baseline dementia. 1, 5
Hyperactive Delirium
- Agitation and restlessness - patient cannot stay still, attempts to remove lines/tubes 1
- Heightened arousal - hypervigilance, easily startled 1
- Aggression - verbal or physical combativeness, particularly during care activities 1
- Hallucinations or delusions - visual hallucinations are particularly common 2
Mixed Delirium
- Alternating between hypoactive and hyperactive symptoms throughout the day or from day to day 1
Temporal Patterns and Risk Stratification
In elderly patients with pre-existing cognitive impairment or dementia, the risk of developing postoperative delirium increases 2.4 to 4.5-fold compared to cognitively intact patients. 1
Specific risk thresholds include:
- Mini-Cog scores ≤3 confer 2.4-4.5 times increased risk 1
- MMSE scores <24 result in 54% incidence versus 26% in those with higher scores 1
- Patients with established MCI/dementia experience POD in 8.7% of cases versus 2.6% in cognitively normal patients 4
Timing of Onset
- Emergence delirium occurs during or immediately after emergence from anesthesia 6, 5
- Postoperative delirium can occur up to 1 week post-procedure or until discharge 6
- No lucid interval is required between emergence delirium and postoperative delirium, though it should be documented when present 6, 5
Associated Behavioral Disturbances
- Sleep-wake cycle disruption - reversal of day-night patterns, nocturnal worsening ("sundowning") 2
- Disorientation - to time, place, or person; may not recognize family members 2
- Memory impairment - particularly short-term memory deficits 2
- Perceptual disturbances - misinterpretations of environmental stimuli 2
Long-Term Cognitive Consequences
Postoperative delirium is the strongest factor associated with development of dementia in the year following major surgery, with a 13.9-fold increased odds of new dementia diagnosis. 7
Additional long-term outcomes include:
- 33.3% of patients with POD subsequently meet criteria for MCI/dementia versus 9.0% without POD 4
- Cognitive changes may persist up to 7.5 years after surgery 6, 5
- Increased mortality risk with 3.1-fold increased odds at 1 year 7
Detection Strategy for High-Risk Patients
Screen all patients over 65 years with cognitive screening tools (Mini-Cog or MMSE) preoperatively to establish baseline, then use validated delirium detection tools (CAM or short-CAM) starting in the recovery area and continuing at least once per nursing shift. 8, 5, 2
The American Geriatrics Society emphasizes that delirium is preventable in up to 40% of cases when systematic screening and multicomponent interventions are implemented. 1, 8