Heat Stroke

Question 1

what produces most body heat?

Answer 1

muscular activity

Question 2

which structures in the body control body temperature?

Answer 2

central and peripheral thermoreceptors

Question 3

what acts as the thermoregulation centre in the brain?

Answer 3

anterior hypothalamus

Question 4

what is the role of the thermoreceptors?

Answer 4

indicate when temperature is above or below the ideal set point

Question 5

what does the body do if the temperature is above the set point?

Answer 5

heat dissipation

Question 6

what does the body do if the temperature is below the set point?

Answer 6

heat conservation and production

Question 7

what temperature is classed as hyperthermia?

Answer 7

> 39.2 C

Question 8

what are some of the causes of hyperthermia?

Answer 8

pyrexia

increased heat production due to increased muscular activity

heat stroke

Question 9

what are the 2 types of heat stroke?

Answer 9

classic heat stroke (reduced heat loss)

exertional heat stroke - overheating due to over-exercise in high temps

Question 10

what causes heat stroke?

Answer 10

failure of heat dissipation

Question 11

what may lead to failure of heat dissipation?

Answer 11

upper respiratory obstruction

increased environmental temperature/humidity

poor environmental ventilation

circulatory compromise

obesity

breed disposition

Question 12

what body temperature carries risk of organ damage/failure?

Answer 12

> 41.6 C

Question 13

why does a temperature of >41.6 C risk permanent organ damage/failure?

Answer 13

caused by cell death due to large increase in oxygen demand and DIC

Question 14

what are the major clinical signs of heat stroke?

Answer 14

stress

hyperthermia

tachycardia

hypovolaemia

hyperdynamic pulses

peripheral vasodilation

collapse

hyperaemic mm (bright red) with rapid CRT

Question 15

when might heat stroke patients appear normothermic?

Answer 15

due to impaired peripheral perfusion - widespread vasodilation

Question 16

what are the symptoms of advanced stage heat stroke?

Answer 16

hypovolaemia

increased intestinal mucosal permeability and impaired GI perfusion

tachypnoea

secondary respiratory complications

Question 17

why might a patient in advance stage heat stroke be hypovolaemic?

Answer 17

GI losses

vasodilation - relative hypovolaemia due to systemic compromise

Question 18

why are patients in heat stroke at higher risk of sepsis?

Answer 18

increase intestinal mucosal permeability and impaired GI perfusion –> endotoxin translocation –> sepsis

Question 19

how can risk of sepsis due to gut translocation be reduced in the heat stroke patient?

Answer 19

patients with severe GI compromise may require mucosal protectants (omeprazole) and IV antibiotics

Question 20

which secondary respiratory complications can occur as a result of heat stroke?

Answer 20

aspiration pneumonia
pulmonary oedema
pulmonary haemorrhage (DIC)

Question 21

what are some of the secondary complications of heat stroke?

Answer 21

impaired renal perfusion

CNS compromise

disseminated intravascular coagulation

Question 22

why is impaired renal perfusion occur as a secondary complication to heat stroke?

Answer 22

due to peripheral shunt of blood - peripheral vasodilation results in reduced blood pressure

Question 23

why does CNS compromise occur as a secondary complication of heat stroke?

Answer 23

direct thermal damage
or
secondary effects (hypoglycaemia)

Question 24

what blood abnormalities may be seen as a result of heat stroke?

Answer 24

hypoglycaemia

hyperbilirubinaemia

electrolyte derangements

thrombosis

Question 25

what may occur to the muscles as a result of heat stroke?

Answer 25

myopathy

Question 26

where is most heat lost in cases of increased body temperature?

Answer 26

through the body surface

Question 27

what is the cardiac effect of increased peripheral circulation?

Answer 27

increased cardiac output to compensate

Question 28

why do many of the secondary complications of heat stroke occur?

Answer 28

due to decreased perfusion of vital organs

Question 29

what is the initial patient response to an increase in environmental temperature?

Answer 29

as environmental temperature exceeds body temperature, patient relies on panting to compensate

Question 30

what is involved in emergency management of heat stroke?

Answer 30

active cooling oxygen supplementation and monitoring oxygenation maintain a patent airway - assess for obstruction IVFT bloods monitor for increased ICP

Question 31

at what body temperature should we start actively cooling a patient?

Answer 31

>41 C

Question 32

why should cold water not be used for active cooling?

Answer 32

using water that is too cold will cause peripheral vasoconstriction and impair heat loss further

Question 33

at what body temperature should we stop actively cooling a patient?

Answer 33

< 39.4 C to prevent hypothermia

Question 34

how often should we measure a patients temperature during active cooling>

Answer 34

every 5 mins minimum

Question 35

why is it important to supplement oxygen in heat stroke patients?

Answer 35

will have very elevated RR (fast panting)

Question 36

how can we monitor oxygenation in heat stroke patients?

Answer 36

SpO2 or arterial blood gas

Question 37

why is it important to give heat stroke patients IVFT?

Answer 37

isotonic crystalloids to support circulation to replace deficits (requires continuous re-assessment)

Question 38

what blood values are valuable to obtain in a heat stroke patient?

Answer 38

PCV total solids glucose electrolytes coagulation factors

Question 39

why is it important to look for abnormal coagulation factors in heat stroke patients?

Answer 39

looking for evidence of coagulopathies - clotting disorders caused by hyperthermia

Question 40

why might patients with heat stroke have increased ICP?

Answer 40

cerebral vasodilation due to peripheral vasodilation

Question 41

is pyrexia beneficial to the patient?

Answer 41

yes

Question 42

why is pyrexia beneficial to the patient?

Answer 42

decreases replication of pathogens and increases function of WBCs

Question 43

should we actively cool patients with pyrexia?

Answer 43

no - beneficial to the body

Question 44

when is it appropriate to administer antipyretic drugs?

Answer 44

patients with cancer and immune compromise

Question 45

what is an antipyretic drug?

Answer 45

a drug used to prevent/reduce fever e.g. paracetamol, NSAIDs

Question 46

what are some of the causes of pyrexia?

Answer 46

inflammatory disease - infectious, immune-mediated neoplastic disease other causes - opioids, hepatic encephalopathy blood transfusion (esp xenotransfusion)