2-8. Peri-operative hyperthermia

If prolonged or ≥ 39^oC this is a clinical emergency: permanent organ dysfunction and death can result.

Treatment depends on the aetiology. Distinguish early between:

·       Excessive heating (most common)

·       Inadequate dissipation of metabolic heat

·       Excessive heat production

·       Actively maintained fever

START

❶ Call for help. Inform theatre team of problem. Measure and record core temperature.

❷ Remove cause of hyperthermia including any insulation and heating devices.

❸ Make an initial diagnosis of the cause as this affects further management (Box A):

• Actively maintained fever (typically cold peripheries, vasoconstricted) OR
• Non-febrile hyperthermia (typically warm peripheries, vasodilated)
• Suspect malignant hyperthermia crisis or neuroleptic malignant syndrome? (→ 3-8)

❹ Start active cooling WITH CAUTION if core temp ≥ 39^oC (stop once below):

• Reduce the operating room ambient temperature.
• Cooling jackets or blankets.
• Ice packing in groin, axillae and anterior neck.
• Bladder, gastric or peritoneal lavage with boluses 10 ml.kg^-1 iced water.

❺ Give benzodiazepines to treat shivering and consider tracheal intubation and muscle paralysis if core temperature ≥ 40^oC

❻ If fever, give antipyretics such as paracetamol and treat underlying cause if known.

❼ Give chlorpromazine if serotonin syndrome is suspected (Box B)

❽ Monitor and manage life-threatening complications especially:

• Hyperkalaemia, hypoglycaemia, acidosis
• Hypotension (→ 2-4), malignant hypertension
• Altered conscious level, convulsions
• Coagulopathy and disseminated intravascular coagulation

Box A: CAUSES OF HYPERTHERMIA

COMMON

• Excessive insulation, high ambient temperature, external warming devices, especially infants and children (most common)
• Surgical devices, e.g. HIFU, diathermy, radiotherapy
• Prolonged epidural anaesthesia
• Sepsis (→ 3-14) e.g. during manipulation of a urological device
• Blood transfusion
• Allergic reaction/anaphylaxis(→ 3-1)

Drug Induced:

• Neuroleptic malignant syndrome (e.g. haloperidol and other antipsychotics)
• Malignant hyperthermia crisis (late sign) (→ 3-8)
• Serotonin syndrome (cocaine, amphetamine, phencyclidine, MDMA)
• Anticholinergic syndrome (tricyclic antidepressants, antipsychotics, antihistamines)
• Sympathomimetic syndrome (cocaine, MDMA, amphetamines)

Toxic:

• Radiologic contrast neurotoxicity
• Alcohol withdrawal

Endocrine:

• Thyrotoxicosis
• Phaeochromocytoma

Neurologic:

• Meningitis
• Intracranial blood
• Hypoxic encephalopathy
• Traumatic brain injury

Box B: CHLORPROMAZINE DOSE

Chlorpromazine (Largactil) 25-50 mg i.m. 6-8 hourly. Caution in elderly.