Mixed Delirium

Mixed delirium is delirium in which hyperactive and hypoactive states alternate during the same episode. It is common and can be missed when only one phase is observed at assessment.

Mixed delirium is the commonest motor subtype in many ward series, and it is frequent in intensive care and after surgery.

Pathophysiology. It reflects the same disruption of attention networks as other delirium subtypes, with shifting balance between arousal and inhibitory systems. The fluctuation follows the circadian cycle, drug effects and the course of the underlying illness.

Periods of agitation, hallucinations or restlessness, often in the evening and at night, alternate with drowsiness, apathy and withdrawal, often in the day. Attention, orientation and sleep wake cycle are disturbed throughout. Staff may observe only one pattern on a given shift.

Assess at different times of day and gather collateral history from nursing staff and family. Screen with a validated tool, and check attention directly. Look for the cause with history, medicine review, observations and tests for any acute confusion (infection, metabolic disturbance, hypoxia, retention, constipation, pain, withdrawal).

Differential diagnosis.

• Dementia with fluctuating cognition (Lewy body dementia).
• Sundowning in dementia.
• Non-convulsive seizures and withdrawal states.
• Bipolar disorder and primary psychosis.

Treat the precipitants and use non-drug measures that support sleep and orientation. Reserve sedatives for dangerous distress. Choose the lowest effective dose of haloperidol (0.25 to 0.5 mg) for hyperactive periods, and avoid sedation during hypoactive periods. Keep the sleep wake cycle intact: daylight, activity by day, quiet and darkness at night, and no unnecessary overnight observations.

Monitoring. Repeat attention assessment each shift, as the dominant phase changes.