Delirium / acute behavioural change EMS Clinical Reference

Clinical snapshot

Twenty-second review

Delirium is acute fluctuating brain dysfunction with impaired attention, commonly triggered by infection, medication, pain, retention, dehydration, hypoxia, or metabolic disturbance.
New inattention with abnormal physiology, focal deficit, meningism, trauma, severe agitation, or inability to maintain safety requires urgent assessment.
Keep dementia or psychiatric illness in the differential; overlapping or concurrent illness remains possible.
For delirium / acute behavioural change, trends and combinations of findings are more informative than one isolated vital sign.

Differentials

Compare the clinical patterns

The repeated material is grouped inside each possibility. Open only the condition you need.

Serious4 conditions

SepsisTime-sensitive high-risk possibility

HPI

Clarify last known normal and baseline cognition; fluctuating course; bgl, oxygenation and temperature.

Signs & symptoms

Physiological compromise, focal findings, headache, or rapid progression.

Focused exam

Record GCS components, pupils, speech, gaze, motor symmetry, sensation, coordination, and gait when safe; Compare findings with baseline and collateral history.

Brief pathophysiology

Sepsis may cause delirium / acute behavioural change through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

No single vital sign diagnoses sepsis. New tachypnea, abnormal temperature, tachycardia, or falling pressure—especially with altered mentation or poor perfusion—supports organ dysfunction and urgency.

Respiratory rate (breaths/min)

May rise early

Tachypnea is included in NEWS2 and can precede overt hypotension.

Temperature (°C)

High or low

Absence of fever does not exclude sepsis; hypothermia is concerning.

Heart rate (bpm)

Often rises

Tachycardia is common but may be blunted by age or medication.

Blood pressure (mmHg)

May fall

Relative hypotension and trend matter; profound hypotension can be late.

Front-load in the triage report

Sepsis: Physiological compromise, focal findings, headache, or rapid progression.
Last known normal and baseline cognition?
Fluctuating course?

StrokeTime-sensitive high-risk possibility

HPI

Clarify fluctuating course; bgl, oxygenation and temperature; infection, trauma, pain or retention.

Signs & symptoms

Physiological compromise, focal findings, headache, or rapid progression.

Focused exam

Compare findings with baseline and collateral history; Test attention and fluctuation, compare baseline cognition, and assess infection, hydration, pain, retention, constipation, medications, and environment.

Brief pathophysiology

Stroke may cause delirium / acute behavioural change through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

Stroke is a clinical diagnosis supported by time course and neurologic findings. Blood pressure and glucose affect eligibility and mimics; normal vitals do not exclude stroke.

Blood pressure (mmHg)

Often elevated

Hypertension is common in acute stroke; hypotension suggests another cause or poor perfusion.

Blood glucose (mmol/L)

Check every patient

Hypoglycemia can mimic focal deficit; hyperglycemia may accompany stress or diabetes.

Heart rate (bpm)

Assess rate / rhythm

An irregular rhythm may suggest atrial fibrillation but is not required.

Oxygen saturation (SpO₂)

Usually preserved

Hypoxemia requires correction and may indicate aspiration or another process.

Front-load in the triage report

Stroke: Physiological compromise, focal findings, headache, or rapid progression.
Fluctuating course?
BGL, oxygenation and temperature?

HypoxiaTime-sensitive high-risk possibility

HPI

Clarify bgl, oxygenation and temperature; infection, trauma, pain or retention; medication or substance change.

Signs & symptoms

Physiological compromise, focal findings, headache, or rapid progression.

Focused exam

Compare findings with baseline and collateral history; Test attention and fluctuation, compare baseline cognition, and assess infection, hydration, pain, retention, constipation, medications, and environment.

Brief pathophysiology

Hypoxia may cause delirium / acute behavioural change through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Hypoxia: Physiological compromise, focal findings, headache, or rapid progression.
BGL, oxygenation and temperature?
Infection, trauma, pain or retention?

Intracranial diseaseTime-sensitive high-risk possibility

HPI

Clarify infection, trauma, pain or retention; medication or substance change; collateral history and safety risks.

Signs & symptoms

Physiological compromise, focal findings, headache, or rapid progression.

Focused exam

Compare findings with baseline and collateral history; Test attention and fluctuation, compare baseline cognition, and assess infection, hydration, pain, retention, constipation, medications, and environment.

Brief pathophysiology

Intracranial disease may cause delirium / acute behavioural change through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Intracranial disease: Physiological compromise, focal findings, headache, or rapid progression.
Infection, trauma, pain or retention?
Medication or substance change?

Common2 conditions

MedicalCommon presentation pattern

HPI

Clarify last known normal and baseline cognition; fluctuating course; bgl, oxygenation and temperature.

Signs & symptoms

Acute fluctuation and inattention with a plausible precipitant are typical.

Focused exam

Record GCS components, pupils, speech, gaze, motor symmetry, sensation, coordination, and gait when safe; Compare findings with baseline and collateral history.

Brief pathophysiology

Medical may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Acute fluctuation and inattention with a plausible precipitant are typical.
Last known normal and baseline cognition?
Fluctuating course?

Medication-triggered deliriumCommon presentation pattern

HPI

Clarify fluctuating course; bgl, oxygenation and temperature; infection, trauma, pain or retention.

Signs & symptoms

Acute fluctuation and inattention with a plausible precipitant are typical.

Focused exam

Compare findings with baseline and collateral history; Test attention and fluctuation, compare baseline cognition, and assess infection, hydration, pain, retention, constipation, medications, and environment.

Brief pathophysiology

Medication-triggered delirium may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Acute fluctuation and inattention with a plausible precipitant are typical.
Fluctuating course?
BGL, oxygenation and temperature?

Mimics2 conditions

DementiaImportant alternative presentation

HPI

Clarify last known normal and baseline cognition; fluctuating course; bgl, oxygenation and temperature.

Signs & symptoms

Chronic impairment lacks the acute fluctuating attention change of delirium.

Focused exam

Record GCS components, pupils, speech, gaze, motor symmetry, sensation, coordination, and gait when safe; Compare findings with baseline and collateral history.

Brief pathophysiology

Dementia can resemble delirium / acute behavioural change through overlapping symptoms or referred physiology despite a different primary mechanism.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Chronic impairment lacks the acute fluctuating attention change of delirium.
Last known normal and baseline cognition?
Fluctuating course?

Psychiatric illnessImportant alternative presentation

HPI

Clarify fluctuating course; bgl, oxygenation and temperature; infection, trauma, pain or retention.

Signs & symptoms

Chronic impairment lacks the acute fluctuating attention change of delirium.

Focused exam

Compare findings with baseline and collateral history; Test attention and fluctuation, compare baseline cognition, and assess infection, hydration, pain, retention, constipation, medications, and environment.

Brief pathophysiology

Psychiatric illness can resemble delirium / acute behavioural change through overlapping symptoms or referred physiology despite a different primary mechanism.

Vital-sign pattern

What the trend may show

Possible pattern

There is no diagnostic vital-sign pattern for a behavioural, functional, or social presentation. Abnormal physiology should be explained and may indicate delirium, toxicity, infection, trauma, or another medical cause.

Temperature (°C)

Screen for medical cause

Fever or hypothermia suggests infection, exposure, or toxicity.

Blood glucose (mmol/L)

Check when indicated

Glucose disturbance can cause altered behaviour or weakness.

Heart rate (bpm)

Explain abnormalities

Tachycardia may reflect distress but should not be dismissed.

Blood pressure (mmHg)

Compare with baseline

Hypotension or severe hypertension warrants medical evaluation.

Front-load in the triage report

Chronic impairment lacks the acute fluctuating attention change of delirium.
Fluctuating course?
BGL, oxygenation and temperature?

Red flags

Findings that should escalate concern

New inattention with abnormal physiology, focal deficit, meningism, trauma, severe agitation, or inability to maintain safety requires urgent assessment.
Sepsis, stroke, hypoxia, or intracranial disease: Physiological compromise, focal findings, headache, or rapid progression.

Related medications

Medication recognition

Amoxicillin Cephalexin Doxycycline

Continue the clinical pathway

References

Clinical and academic sources

Curated clinical guidance and peer-reviewed evidence supporting this presentation. Current BCEHS guidance, medical direction, and local policy remain authoritative for practice.