1. LTC Don Spaner MD TF 325th FH Bagram Afghanistan
HEAT ILLNESS
LTC Don Spaner MD
TF 325th FH
Bagram Afghanistan

2. Heat Emergencies ABOUT 390 DEATHS/YEAR USA MAYBE >4000/YEAR
#2 CAUSE OF DEATH IN YOUNG ATHLETES
>RISK= EXTREMES OF AGE

3. HEAT BALANCE
Body Heat=metabolism+[conduction+radiation+convection-evaporation]
BH=M+[+K+R+C-E]

4. RADIATION
Primary heat loss when the environment is cooler than body temperature.
Simply the transfer of electromagnetic waves.
65% of heat loss.

5. CONVECTION Heat exchange between a surface and a medium.
10-15% heat loss.
Heat gain in a humid environment.
Greatly affected by the winds.

6. CONDUCTION Heat exchange between 2 surfaces in direct contact.
2% of heat loss normally.
>25% heat loss in cold water.

7. EVAPORATION (insensible or wet)
Can only result in heat loss.
Primarily through sweating.
Sensible heat loss fails in a hot environment.
Evaporation becomes the primary loss of heat.
This also fails in high humidity.

8. Physiologic Response to Heat
Core temp. rises
Hypothalamus stimulates ANS
Decrease VMT=Increase blood flow peripherally.
Parasympathetic stimulates sweating&recruits sweat glands.0.5L/D to 10-15L/D

9. Sweating 1L of sweating consumes 600 Kcal Heat
Better Hydration=Better cooling!

10. Vasodilation Results Increase in radiation loss.
Increase CO 3L/min for each 1degree of C(1.8F)
Thus increase in heart rate.

11. Acclimatization Sweating earlier High sweat rate >Peri.Blood flow
Decrease[NaCl] in sweat/urine. Due to increase aldosterone.
Decrease HR
Decrease core body temp.
Increase plasma volume.
Increase exercise tolerance
1-4Hrs/Day for 14 days.

12. Predisposing Factors to Heat Injury:
1)Increased internal heat production.
2)Increased external heat gain.
3)Decreased ability to disperse heat.

13. Increased Internal Heat Production:
1)Physical activity!
2)Febrile illnesses: Much different.
3)Pharmacologic agents: cocaine, LSD, PCP, Amphetamines.

14. Increased External Heat Gain:
1)Exposures to high ambient temps&high humidity. This can lead to rapid exogenous heat gain.
2)No AC risk of heat stroke increases 49X.

15. Wet-Bulb Globe Temperature(WBGT)i
Measures air temp. via dry bulb
Humidity via wet bulb.
Radiant heat with a black globe.
WBGT=0.7Twb+0.2Tbg+0.1Tdb
>33C(91.4F) increase incidence of heat injury.

16. Risk Factors Heat Illness
Dehydration
Obesity
Heavy clothing
Poor fitness
Not acclimated
Cardiac disease
Skin disease
Extremes of age
Lack of mobility
Febrile illness
Hyperthyroidism
ETOH
Drugs
Poor
Exertion
Meds

17. Heat Edema Mild swelling of hands and feet. Cutaneous vasodilation.
Not past ankles
No Tx required may elevate.
Resolves in days to weeks.
Do not use diuretics.

18. Prickly Heat lichens tropicus/miliaria rubra/heat rash
Puritic, maculopapular, erythematous rash over clothed areas of the body.
Acute inflammation of the sweat ducts caused by blockage of sweat glands.
Prevented by wearing clean light clothing.

19. Prickly Heat Treatment
Antihistamines
Chlorhexidine cream or lotion.
Treat any underlying infection.

20. Heat Syncope Variant of postural hypotension.
Common in non-acclimatized folks.
TX: Remove from heat, IVF, Rest, R/O other causes.

21. Heat Cramps
Painful involuntary spasmodic contractions of skeletal muscle. Usually calves.
Happens with liberal sweating & replacement with hypotonic solutions.
Common in non acclimatized folks

22. Heat Cramp Treatment Commercial Electrolytes beverages. IVF N/S
No salt tabs
Pain Management.

23. Heat Tetany
Hyperventilation to respiratory alkalosis to paresthesia and carpal pedal spasm.
Tx: Removal from heat and decrease respiratory rate.

24. Heat Exhaustion : Dizziness Weakness Malaise Light Headed Fatigue N/V
Myalgias
Syncope
Orthostatic
Sinus Tach
Tachypnea
Diaphoresis
Hyperthermia
Hemoconc.
Normal neuro!

25. Heat Stroke Core Temp>40.5C(104.9F) CNS dysfunction
Anhidrosis (not an absolute)
Due to high mortality rate the patient requires immediate intervention.

26. CNS Irritability Bizarre behavior Combativeness Hallucinations
Seizures
Coma
Ataxia

27. Ddx Heat Stroke ETOH withdraw. NMS MH Anticholinergics Salicylate tox.
PCP, Cocaine Amphetamines
Tetanus/Sepsis/Encephalitis
Meningitis
Brain Abscess
Malaria
Typhoid
Status Epilep.
Cerebral hemorrhage
DKA/Thyroid Storm

28. Treatment of Heat Stroke
ABCs,O2,Monitoring,Pox
IVF consider CVP
Foley core temp.
CBC,CMP,HFP,COAGS,CK,U/A, Tox
EKG, CXR
LP as indicated.

29. Cooling Techniques Evaporation Immersion Ice packing
Cold Gastric Lavage
Cold peritoneal lavage.
Cardiac Bypass (Most rapid)

30. Initial Heat Stroke Complications
Hypotension
Shivering
Seizures
Coma
Hypothermia
Rebound Hyper.
EKG changes
. CHF
. Pulmonary Edema
Hypokalemia
Rhabdomyolosis
Diarrhea

31. Delayed Complications of Heat Stroke
Hyperkalemia
Hypocalcemia
Hyperuricemia
Renal failure
Cerebral edema
Hyperosmolar coma
Persistent CNS deficit
Thrombocytopnea
DIC
Hepatic failure
ARDS
GI hemorrhage

32. Thank You
Questions?