Heat emergencies represent a continuum of disorders from heat cramps to heat stress that, when severes, culminate into heat stroke.

1. HEAT EMERGENCIES
Dr. Ashutosh Kumar Singh

2. Introduction
• Heat emergencies represent a continuum of disorders
from heat cramps to heat stress that, when severes,
culminate into heat stroke.
• The incidence of heat-related emergencies varies with
the weather.
• Heat stroke is likely seen less among persons who live
in warmer climates than travellers to these areas
because of physiologic acclimatization and cultural
adaptation of the former to heat.

3. Pathophysiology
1. Mechanism of Heat Transfer
2. Response to heat stress
3. Acclimatization
4. Path to heat injury

4. Mechanism of Heat Transfer
1. Radiation- transfer of heat by electromagnetic waves
from a warmer object to a colder object.
2. Conduction—heat exchange between two surfaces in
direct contact.
3. Convection—heat transfer by air or liquid moving
across the surface of an object.
4. Evaporation—heat loss by vaporization of water
(sweat).

5. • The body tends to maintain its core temperature between
36°C and 38°C(96.8°F and 100.4°F).
• dilatation of blood vessels particularly in the skin;
 increased sweat production.
 decreased heat production.
• cardiac output increases about 3 L/min for each 1°C
(1.8°F) elevation of core temperature.
• The heart rate increases to compensate for the decrease
in stroke volume.
Response to heat stress

7. Acclimatization
• Acclimatization is the adaptation of the body’s heat stress
mechanisms to increase the efficiency of heat loss in a hot
climate.
• primary methods of acclimatization is sweating,
improvement in cutaneous vascular flow and overall
cardiovascular function.
• In most individuals, acclimatization can be achieved over
7 days to several weeks.
• Once removed from the hot environment, the body will de-

8. Path to Heat Injury
• Heat production rapidly increases during physical
activity due to skeletal muscle contraction.
• Excessive heat is directly toxic to cells, causes an
acute-phase reaction with release of inflammatory
cytokines, and damages vascular endothelium
• Dehydration and hyperpyrexia.

9. HEAT EDEMA
• self-limited process manifested by mild swelling of the
feet, ankles, and hands that appears within the first few
day.
• cutaneous vasodilatation and orthostatic pooling of
interstitial fluid in gravity-dependent extremities
• increase in the secretion of
aldosterone and antidiuretic
hormone in response to the
heat stress also contributes to
the mild edema.

10. PRICKLY HEAT
• Prickly heat is a pruritic, maculopapular, erythematous
rash over normally clothed areas of the body.
• Also known as lichen tropicus, miliaria rubra or heat
rash.
• acute inflammation of the sweat ducts caused by
blockage of the sweat pores by macerated stratum
corneum.
• C/F: Itching.
• Tx: Chlorhexidine is a light cream or lotion
antihistamines.

11. HEAT CRAMPS
• Heat cramps are painful, involuntary, spasmodic
contractions of skeletal muscles, usually those of the
calves, although they may involve the thighs and
shoulders.
• individuals who are sweating profusely and replace fluid
losses with water or other hypotonic solutions.
• occur during exercise or more commonly, during a rest
period after several hours of vigorous physical activity.

12. Contd…
• Hyponatremia and Hypochloremia can be seen.
• Treatment consists of fluid and salt replacement (PO or
IV) and rest in a cool environment.

13. HEAT TETANY
• Heat tetany consists of typical hyperventilation resulting in
respiratory alkalosis, paraesthesia of the extremities,
circumoral paresthesia and carpopedal spasm.
• Heat tetany can be differentiated from heat cramps -little
pain or cramping in the muscle compartments, and
paresthesia of the extremities and perioral region are
more prominent.

14. HEAT SYNCOPE
• Heat syncope is a variant of postural hypotension
resulting from the cumulative effect of relative volume
depletion, peripheral vasodilatation and decreased
vasomotor tone.
• It occurs most commonly in non-acclimatized individuals
during the early stages of heat exposure.
• Highest incidence – elderly.
• Evaluation of patients requires exclusion of metabolic,
cardiovascular, and neurologic disorders .
• Treatment : removal from the heat source, rehydration and
rest.

15. HEAT EXHAUSTION
• Water depletion & Sodium depletion.
• Water depletion heat exhaustion tends to occur in the
elderly and in persons working in hot environments with
inadequate water replacement.
• Salt depletion , heat exhaustion tends to occur in
unacclimatized individuals who replace fluid losses with
large amounts of hypotonic solutions.
• C/F: headache, nausea, vomiting, malaise, dizziness, and
muscle cramps as well as signs of dehydration, such as
tachycardia and orthostatic hypotension.

16. Contd…
• Heat exhaustion is treated with volume and electrolyte
replacement and rest.
• patients with heat exhaustion who do not respond to 30
minutes of fluid replacement and removal from the heat-
stressed environment be aggressively cooled until their
core temperatures drop to 39°C (102°F)

17. HEAT STROKE
• Heat stroke is an acute life-threatening emergency with
mortality rates as high as 30% to 80% and is universally
fatal if left untreated.
• The cardinal features of heat stroke are hyperthermia
[>40°C />104°F)] and altered mental status.
• neurologic abnormality-ataxia can be an early neurologic
finding, irritability, confusion, hallucinations, plantar
responses, decorticate and decerebrate posturing,
hemiplegia, status Epilepticus, and coma.

18. • Seizures are quite common, especially during cooling.
• A delay in cooling increases the mortality rate.
• Laboratory Evaluation- CBG,ABG, CBC , coagulation
profile, creatine, phosphokinase level, myoglobin level,
urine analysis, ECG, and chest radiograph.

19. HEAT STROKE DIFFERENTIAL DIAG.

20. TREATMENT
The goals of therapy are immediate cooling and
support of organ system function.
1. Pre-hospital Care
2. E D Management

21. Pre-hospital Care
• Immediately patient must be removed from the
environment.
• Cooling should be initiated by removing Clothing and
placing wet towels or sheets over the patient’s body, or
placing ice packs over the neck, groin, and axilla.
• transported by air-conditioned vehicle to the closest
hospital.

22. ED Management
• Initial Resuscitation
 Standard resuscitation measures
 Cooling Techniques

23. Initial Resuscitation
• administration of high-flow oxygen;
• continuous cardiac monitoring and pulse oxymetry
• establishment of IV access- IV fluids at a rate that
ensures adequate urine output, begin with 250 ml/h.
• Glucose levels should be evaluated on arrival.
• In elderly patients, fluid therapy should be monitored
using a central venous pressure line or pulmonary artery
catheter, if possible.

24. Cooling Technique

25. Complication of Heat Stroke

26. Disposition & Follow up
• Patients with minor heat emergency syndromes require
only ED treatment along with clear discharge
instructions.
• congestive heart failure , renal failure or patients with
severe electrolyte imbalance may require hospital
admission.
• Heat stroke is a true medical emergency and all patients
require admission.