Hyperthermia

Question 1

What is the continuum leading to hyperthermia

Answer 1

1. heat stress
2. heat exhaustion
3. heat stroke
4. multi-organ dysfunction and cardiac arrest

Question 2

What causes malignant hyperthermia?

Answer 2

Exposure of genetically predisposed indivuduals to halogenated anaesthetics and depolarising muscle relaxants

Question 3

What is malignant hyperthermia?

Answer 3

A rare disorder of skeletal muscle calcium homeostasis characterised by
* muscle contracture
* life threatening hyper-metabolic crisis

Question 4

What is normothermia?

Answer 4

36.5-37.5

Question 5

What is the mortality from heat stroke?

Answer 5

10-30%

Question 6

What are the two characteristic forms of heat stroke?

Answer 6

1. non-exertional heat stroke
2. exertional heat stroke

Question 7

What is the key risk factor associated with heat stroke?

Answer 7

An impaired ability to sweat

Question 8

What may patients with milder forms of hyperthermia present with?

Answer 8

intense thirst, weakness, syncope, dizziness

Question 9

What is the triad of heat stroke?

Answer 9

1. severe hyperthermia (core body temp >40)
2. neurological symptoms (coma, confusion, seizure)
3. exposure to high environmental temperatures (classic heat stroke) or recent strenuous activity (exertional heat stroke)

Question 10

What other causes of increased core temperature must be considered?

Answer 10

• drug toxicity
• drug withdrawal
• serotonin syndrome
• neuroleptic malignant syndrome
• sepsis
• CNS infectoin
• endocrine disorders (thyroid storm, phaeochromocytoma)

Question 11

What are the key treatments of hyperthermia?

Answer 11

• lay the patient flat
• move to a cool environment
• immediately start cooling
• move to hospital
• cooled to <39 (ideally 38-38.5)
• rapid cooling is safe (cooling rates of 0.2-0.35c per min)

Question 12

How is rapid cooling achieved?

Answer 12

Cold-water immersion or full-body conductive cooling systems

fanning/cool IV fluids/extracorporeal circuits/intravascular cooling

Question 13

What temperature reduces chances of favourable neurological outcome

Answer 13

> 37

Question 14

What is the treatment for malignant hyperthermia?

Answer 14

• stop triggering agents immediately
• give oxygen
• correct acidosis and electrolyte abnormalities
• start active cooling
• give dantrolene