Heat related illnesses simply explained, spectrum of hyper and hypothermia related clinical scenarios with symptoms, diagnosis, management and prognosis.

1. Heat Related Illness
By:
Dima Lotfie

2. Hyperthermia
• Elevated body temperature due to failed thermoregulation that
occurs when a body produces or absorbs more heat than it dissipates.
• hyperthermia is defined as a temperature greater than 37.5–38.3 °C
(99.5–100.9 °F) that occurs without a change in the body’s
temperature set point.

3. Precipitating factors
• Strenuous activities outside on a hot day
• Working in a hot room with no air circulation
• Not enough fluid intake while working
• Working in a building where cooling system fails
• Humid conditions combined with hot temperatures

4. Spectrum of heat illness
Heat edema/rash Heat cramps Heat syncope Heat exhaustion Heat stroke

5. Heat Edema/Rash
• Pitting edema
• Most commonly in hands and feet
• Can last from days to weeks
• Bed ridden elderly are more prone
• High temperature → vasodilation → pitting edema
Ø Treatment:
• Self limited
• Reassurance, limb elevation, bandages
• Avoid high temperatures and adequate rehydration.

6. Heat Cramps
• Localized, painful, involuntary spasms of skeletal muscles.
Ø Causes:
• Sodium and/or chloride depletion
• Dehydration
• Impaired circulation in working muscles
• Alterations in spinal neural reflex activity increased by fatigue
Ø Most commonly affected muscles are:
Calf, quadriceps, hamstrings, abdominal muscles.

8. Heat Cramps
Ø Treatment:
• Slow, passive stretching of involved muscle.
• Massage
• Ice
• Fluids replacement
Ø May return to activity when symptoms subside.

9. Heat Syncope
• Occurs as a result of insufficient blood
supply to the brain due to vasodilation of
the skin vessels → decreased venous return
→ less CO2 → low perfusion to the brain →
fainting.
• Or due to drop in blood pressure as a result
of vasodilation.

10. Heat Syncope
Ø Symptoms:
1. Light headedness
2. Dizziness
3. Fainting
Ø Treatment:
• Put the patient in a cool place and elevate the legs
• If regained consciousness: rest and adequate rehydration.
• If remained unconscious: treat as shock.

11. Heat Exhaustion
• Most common form of heat illness
• Caused by heat exposure + ↑ activity + decreased fluids intake.
Ø Symptoms:
• Headache
• Weakness
• Fatigue
• Skin is moist (heavy sweating), cold and pale.
• Hyperventilation
• Low BP and fast weak pulse
• Anxiety/confusion

12. Heat Exhaustion
Ø Management:
• Move to a cooler location
• Lie down and loosen the clothes
• Apply wet cold towels/ice
• Use fans
• Adequate oral or IV fluid replacement.

13. Heat Stroke
• A life threatening clinical syndrome characterized by loss of
temperature regulation capabilities.
• The third most common cause of death in athletes in the US.
Ø Diagnosis:
• An individual who collapses after exposure to a hot environment
• Rectal temperature is ≥ 41.1 °C (106 °F).
• Neurological dysfunction.

14. Heat Stroke: Types
1. Classic (non-exertional):
• Sedentary, elderly, chronically ill individuals
• Young individuals exposed to hot environment for long periods.
2. Exertional:
• In young individuals involved in heavy exercise for a prolonged period
of time in a hot environment.

15. Heat Stroke
Ø Clinical features:
• Classical triad:
1. Hyperpyrexia
2. Anhydrosis
3. Mental status alteration (CNS dysfunction):
• Delirium
• Ataxia
• Seizures
• Coma

16. Heat Stroke Management
Ø Lab evaluation
• ECG
• CXR
• CBC, electrolytes, renal function test, liver function test, urine analysis.
Ø Treatment:
• ABC
• Cooling methods.

17. Heat Stroke Management
Ø Ice water immersion:
• The best method, gives the highest rates of
survival.
• Caution with unconscious people →
aspiration risk
• Caution with alert people → might be
uncomfortable

18. Heat Stroke Management
Ø Other cooling methods:
• Evaporative cooling (fans and water): second best method
• Ice packs: to groin/axilla/neck → longer time than evaporating but
good together.
• Ice water blankets/wet towels
• Fans
• Peritoneal, thoracic, rectal and gastric lavage with ice water
• Cold IV fluids
• Cold humidified oxygen

20. Heat Stroke: Prognosis
• Depends on the duration and the severity.
• With early recognition and treatment, survival rate
is 90-100%.

21. Serotonin Syndrome
• A toxic state caused by an increase in brain serotonin activity.
Ø Causes:
• Most often with combination or consecutive treatment with SSRIs,
tricyclics, MAOIs, Narcotics, Tryptophan..etc.
• High doses of narcotics can cause it within 6 hours
Ø Symptoms:
• General restlessness/agitation
• Sweating
• Hyperthermia
• Hyper-reflexia
• Tachycardia, insomnia, nausea, diarrhea, cramps, delirium and coma.

22. Serotonin Syndrome Treatment
1. Stop the drugs
2. Cyproheptadine
3. Symptomatic measures
Ø Prevention:
• Caution when combining antidepressants.

23. Hypothermia
• A medical emergency that occurs when the body loses heat faster
than it can produce, causing a dangerously low body temperature
below 35 °C (95 °F).
• Hypothermia is most often caused by exposure to cold weather or
immersion in cold water.

24. Hypothermia: types
• Primary hypothermia is used when the ability of an otherwise
healthy person to maintain their core body temperature is
overwhelmed by excessive cold temperatures, particularly when
energy stores within the body have been depleted.
• Secondary hypothermia is applied when hypothermia is associated
with acute events or illness, such as cerebrovascular accident (CVA),
subarachnoid hemorrhage (SAH), diabetic ketoacidosis (DKA) or
burns.
• Secondary hypothermia can occur even where the environment is
warm

27. Hypothermia: first aid
• Remove wet clothing, use dry blankets or sleeping
bags.
• Initiate external rewarming with heat packs
(hot water bottles, chemical packs) placed in the
axillae, groin, and on the abdomen.
• In dire circumstances, when heat packs are
unavailable, rescuers can provide skin-to-skin
contact with patients.

28. Hypothermia: Management
• Prehospital management: prevent further heat loss and rewarm the
body core temperature.
• Bretylium (5 mg/kg initially) is recommended for any hypothermic
patient manifesting significant new ventricular ectopy or frank
dysrhythmia.
• Warmed, humidified oxygen; heated intravenous saline; warmed
blankets or heat lamps around a hypothermic patient.
• Cardiothoracic bypass has been successful for treating cases of
accidental hypothermia with prolonged cardiac arrest.
• Bypass must be performed rapidly for a higher success rate.

29. Hypothermia: ECG findings

30. References
• Davidson’s
• Harrison’s textbook of medicine
• Seto CK, et al. Environmental illness in athletes. Clin Sports Med 21
(2005) p695-718.
• Wexler Randall, Evaluation and Treatment of Heat Illness, American
Family Physician. June 1, 2002.