Environmental heat diagnoses: Difference between revisions

Latest revision as of 17:09, 25 January 2023

Background

Heat related illnesses includes a wide range diagnoses from benign heat rash to heat stroke.
Dehydration and salt depletion affect thermoregulation by reducing the body's ability to increase the cardiac output needed to dissipate the heated blood
Cardiovascular disease and use of drugs that impair cardiac function can result in increased susceptibility to heat illness

Types of heat dissipation

Conduction: heat exchange between two surfaces in contact (placing ice pack in axilla)
Convection: heat exchange between a surface and a fluid (fanning)
Radiation: transfer of heat between body and environment through electromagnetic waves (reliant on temperature gradient)

Heat Illness Etiology

All types are due to inadequate thermoregulation

Classic Heat Illness
- Occurs without physical exertion
Exertional
- Preceded by physical activity

Clinical Features

Miliaria

Man with signs of heat exhaustion, including copious sweating.

Heat Illness Types

Heat cramps
- Muscle cramps due to electrolyte depletion
Heat syncope
- Prolonged standing +vasodilation + volume loss → decreased central venous return → decreased CO→ decreased cerebral perfusion pressure
Heat exhaustion (temperature usually < 40°C)
- headache, n/v, weakness, vertigo, no CNS dysfunction
- Water depletion: inadequate fluid replacement to match fluid loss (sweat)
- Salt depletion: large volume of fluid loss is replaced with water (with inadequate salt)
Heat stroke (temperature usually > 40°C)
- Similar to heat exhaustion plus CNS dysfunction (seizure, AMS), transaminitis, DIC, rhabdomyolysis

Differential Diagnosis

Environmental heat diagnoses

See also hyperthermia

Evaluation

Clinical diagnosis
Evaluate for alternate etiologies of hyperthermia if no clear exposure

Management

Heat cramps
- Mild: oral electrolyte solution
- Severe: IV NSS
Heat syncope
- Supine position
Heat exhaustion
- Mild: oral fluid replacement
- Severe: IV fluid replacement and replete electrolytes as needed
Heat stroke
- ABCs
- Rapid cooling
- IVF, replete electrolytes
- Benzos: for seizures and shivering

Disposition

Heat stroke requires admission
Other conditions can be discharged after improvement with treatment
Do not use antipyretic agents (their use in heat illness has not been evaluated)

References

Authors:

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-==Heat Edema==
+==Background==
-#Self-limited, mild edema of feet, ankles, and hands
+*Heat related illnesses includes a wide range diagnoses from benign [[heat rash]] to [[heat stroke]].
-#Appears w/in first few days of exposure to a hot environment
+*Dehydration and salt depletion affect thermoregulation by reducing the body's ability to increase the cardiac output needed to dissipate the heated blood
-##Commonly seen in travelers just arriving from a colder climate
+*Cardiovascular disease and use of drugs that impair cardiac function can result in increased susceptibility to heat illness
-#Resolves spontaneously in days to weeks
+===Types of heat dissipation===
-#Treatment
+*Conduction: heat exchange between two surfaces in contact (placing ice pack in axilla)
-##Elevation of legs
+*Convection: heat exchange between a surface and a fluid (fanning)
-##Use of support hose
+*Radiation: transfer of heat between body and environment through electromagnetic waves (reliant on temperature gradient)
-##Diuretics are contraindicated
-==Miliaria (Heat Rash)==
+===Heat Illness Etiology===
-#Pruritic, maculopapular, erythematous rash over normally clothed areas of body
+''All types are due to inadequate thermoregulation''
-##See [[Media:Miliaria.jpg]]
+#Classic Heat Illness
-#Pathophysiology
+#*Occurs without physical exertion
-##Acute inflammation of sweat ducts caused by blockage of pores by macerated skin
+#Exertional
-###Ducts become dilated under pressure and ultimately rupture
+#*Preceded by physical activity
-####This produces superficial vesicles in malpighian layer of skin on a red base
-#####May progress to miliaria profunda (white papules) if duct ruptures a second time
-#Treatment
-##Antihistamines
-##Dicloxacillin or erythromycin if appears superinfected
-==Heat Cramps==
+==Clinical Features==
-#Painful, involuntary, spasmodic contractions of skeletal muscles
+[[Image:Miliaria.jpg|thumbnail|[[Miliaria]]]]
-##Usually affects calves, thighs and shoulders
+[[File:PMC3040629 ehp-119-a81f1 2.png|thumb|Man with signs of [[heat exhaustion]], including copious sweating.]]
-#Occurs to pts who are sweating profusely and replace fluid losses with water
+===Heat Illness Types===
-##May occur during exercise or during a rest period several hrs later
+#[[Heat cramps]]
-#Treatment
+#*Muscle cramps due to electrolyte depletion
-##Self-limited
+#[[Heat syncope]]
-##Pain is difficult to tx; often does not respond to opiates alone
+#*Prolonged standing +vasodilation + volume loss → decreased central venous return → decreased CO→ decreased cerebral perfusion pressure
-##Gatorade or NS IV
+#[[Heat exhaustion]] (temperature usually < 40°C)
+#*headache, n/v, weakness, vertigo, no CNS dysfunction
+#*Water depletion: inadequate fluid replacement to match fluid loss (sweat)
+#*Salt depletion: large volume of fluid loss is replaced with water (with inadequate salt)
+#[[Heat stroke]] (temperature usually > 40°C)
+#*Similar to heat exhaustion plus CNS dysfunction (seizure, AMS), transaminitis, DIC, rhabdomyolysis
-==Heat Tetany==
+==Differential Diagnosis==
-#Hyperventilation > respiratory alk > extremity/circumoral paresthesia, carpopedal spasm
+{{Heat Emergencies}}
-#Differentiate from heat cramps based on little pain, no cramping in muscle compartments
-#Treatment
-##Remove from heat, decrease resp rate
-==Heat Syncope==
+''See also [[hyperthermia]]''
-#Variant of postural hypotension
-##Results from combination of volume depletion and peripheral vasodilatation
-##Occurs in nonacclimatized during early stages of heat exposure (esp elderly)
-#Management
-##Diagnosis of exclusion
-##Remove pt from heat source, give PO or IV rehydration
-##Hospitalization usually is not necessary
-==Source==
+==Evaluation==
-Tintinalli
+*Clinical diagnosis
+*Evaluate for alternate etiologies of [[hyperthermia]] if no clear exposure
+==Management==
+#[[Heat cramps]]
+#*Mild: oral electrolyte solution
+#*Severe: IV NSS
+#[[Heat syncope]]
+#*Supine position
+#[[Heat exhaustion]]
+#*Mild: oral fluid replacement
+#*Severe: IV fluid replacement and replete electrolytes as needed
+#[[Heat stroke]]
+#*ABCs
+#*Rapid cooling
+#*IVF, replete electrolytes
+#*Benzos: for seizures and shivering
-[[Category:Environ]]
+==Disposition==
+*[[Heat stroke]] requires admission
+*Other conditions can be discharged after improvement with treatment
+*Do not use antipyretic agents (their use in heat illness has not been evaluated)
+==See Also==
+*[[Hyperthermia]]
+*[[Celsius Fahrenheit Temperature Conversion]]
+==References==
+<references/>
+[[Category:Environmental]]