• Hypothermia usually occurs with other acute or chronic illness
• occurs at any time of year
• suspect an underlying illness
• older person may be unable to recognise and respond both physiologically and practically to cold

Symptoms and signs

• In mild cases, patient may complain of cold
• this is not reliable
• Symptoms of a precipitating condition
• Shivering may be present in mild cases but is usually absent in severe cases
• Skin (abdomen, inner thigh, axilla) cold, mottled and feels like marble
• Face may appear puffy and myxoedematous
• Muscle rigidity, absent deep reflexes and extensor plantars may be found
• Depressed respiration
• Bradycardia with underlying sinus rhythm or atrial fibrillation
• Hypotension
• Confusional state (delirium)
• Apathy
• Coma when temperature <32°C

Core body temperature

• Measure with tympanic thermometer

Severity

• Mild 35–32°C
• Moderate 31.9–30°C
• Severe <29.9°C

Investigations

Blood

• FBC, U&E, INR, Troponin I
• venous blood pools and may give erroneous results
• Blood glucose
• may be high but falls during rewarming
• Thyroid function tests
• Blood culture. See Collection of blood culture specimens guideline
• Arterial blood gases
• remember to enter core temperature into analyser

Other

• Urinalysis
• ECG
• may show characteristic J wave on the down stroke of the R wave, best seen in leads II and V6, or QT_c prolongation
• Chest X-ray
• look for pneumonia, aspiration, pulmonary oedema

Consider associated/causative conditions

• Hypothyroidism
• Hypopituitarism
• Hypoadrenalism
• Stroke
• Epilepsy
• Parkinson's disease
• Fractures
• Drug overdose
• Dementia
• Pneumonia
• Myocardial infarction
• Over-sedation
• Drug-induced
• alcohol, barbiturates, phenothiazines, lithium, tricyclics, opioids
• Heart failure
• Head injury

Supportive treatment

• Special mattress (to prevent pressure sores)
• If hypoxaemic, give controlled oxygen therapy. See Oxygen therapy in acutely hypoxaemic patients guideline
• If pneumonia suspected, see Community-acquired pneumonia guideline

Warming

• Nurse at room temperature of 25–30°C
• Warm with blankets (remember to cover head and neck)
• if available, use Bair Hugger™ (forced air re-warming) blanket

Intensive care unit (ITU)

• Discuss transfer to ITU
• if not responding to re-warming, discuss with ITU consultant on-call as to whether transfer is required

• Most patients will improve spontaneously without further active treatment
• Avoid unnecessary interventions and movement
• these can precipitate cardiac arrhythmia
• Identify and treat other predisposing factors

Patient fails to warm

• Prognosis poor
• If core temperature <30°C, high risk of death
• In moderate-severe hypothermia (<32°C), consultant to consider use of warm IV fluids
• give by IV fluid warmer or a heated infusion pump
• Never warm IV fluids in microwave
• Observe temperature, pulse, BP every 15 min and with continuous cardiac monitoring
• if profound bradycardia persists, contact on-call cardiology SPR to discuss temporary pacing

Cardiac arrest

• Continue cardiac arrest procedures for longer than usual
• hypothermia protects against cerebral hypoxia

Multidisciplinary team assessment

• Once re-warming started in A&E, ensure patient admitted, if aged >65 yr, straight to an elderly care bed
• Assessment by full multidisciplinary team
• If the paramedics have raised a vulnerable adult referral, confirm investigated before discharge

Hourly (if patient requires active re-warming, every 15 min)

• Core temperature with tympanic thermometer
• for mild hypothermia, aim to raise by 0.5–1°C/hr
• for moderate to severe hypothermia, aim to re-warm at 1°C/hr
• if temperature rises by >1°C/hr, cool by removing blankets to maintain peripheral vasoconstriction
• pyrexia after re-warming does not necessarily indicate infection
• Heart rate and rhythm (continuous cardiac monitoring)
• bradycardia and AV block can occur and may require temporary pacing
• ventricular ectopics are suppressed by cold and may appear during warming
• BP
• Respiration
• Glucose
• treat hypoglycaemia with glucose infusion. See Acute hypoglycaemia guideline
• do not treat hyperglycaemia with insulin unless blood glucose persistently >30 mmol/L
• insulin is ineffective in the hypothermic state. Do not use unless re-warming is very slow

2-hrly

• pH (until core temperature >35°C)
• If hypoxaemic or acidotic, PaCO₂

• Paralytic ileus
• Gastric dilatation
• Respiratory failure
• Cardiovascular collapse
• Oliguria
• Gastric ulceration
• Pancreatitis
• Aspiration pneumonia

• Assess cognitive state immediately before discharge by doing a 6 CIT score
• if cognitive impairment is noted, consider referral to mental health liaison team while patient still in hospital or
• advise GP in the discharge summary to refer to memory clinic
• If the paramedics have raised a vulnerable adult referral, confirm investigated before discharge
• If patient lives alone, ensure they can summon help by telephone or Care Line
• Ensure home is adequately heated
• Ensure patient and family are aware of risks of hypothermia