Heat Illness/Hyperthermia

1
Heat Illness/Hyperthermia

• Victor Politi, M.D., FACP
• Medical Director - SVCMC Physician Assistant
  Program

2
(No Transcript)
3
Risk factors for heat illness ObesityFatigueD
rugsAlcoholSunburnUnacclimatizedFluid
deficitPrevious history of heat injuryMany
medical conditionsFebrile illnessCystic
fibrosisDiabetesMalnutrition
4
Heat Illness Classification

• Heat Rash
• Heat syncope
• Heat tetany
• Heat edema
• Heat cramps
• Heat exhaustion
• Heat stroke

5
(No Transcript)
6
Minor Heat Illness - Heat Cramps

• Brief, intermittent, often severe muscular cramps
  typically occurring in muscles that are fatigued
  by heavy work
• Usually occur after exertion
• Copious hypotonic fluid replacement during
  exertion
• Hyperventilatoin not present in cool environment

7
Minor Heat Illness - Heat Cramps

• Related to salt deficiency
• Victims exhibit -hyponatremia, hypochloremia, low
  urinary sodium and chloride levels
• Usually rapidly relieved by salt solutions

8
Minor Heat Illness - Heat Edema

• Minimal edema - feet/ankles
• Not accompanied by any other significant
  impairment in function
• Often resolves after several days of
  acclimatization
• Brief diagnostic evaluation to rule out
  thrombophlebitis, lymphedema or CHF is appropriate

9
Minor Heat IllnessHeat Syncope

• Individuals at risk should be warned to move
  frequently, flex leg muscles repeatedly whenever
  standing
• Scintillating scotomata, tunnel vision, vertigo,
  nausea, diaphoresis, and weakness are prodromal
  symptoms of syncope
• Adequate oral volume replacement may prevent some
  conditions

10
Minor Heat Illness - Prickly Heat AKA miliaria
rubra, lichen tropicus, heat rash

• Acute phase -
• Produces intensely pruritic vesicles onan
  erythematous base
• Rash confined to clothed areas
• Effected area completely anhydrotic
• produnda stage-
• may persist for weeks
• chronic dermatitis -frequent complication

11
Heat Exhaustion - two types classically described

• Water depletion heat exhaustion
• inadequate fluid replacement by persons in heat
  voluntary dehydration
• weakness, fatigue, frontal headache, impaired
  judgement, vertigo, nausea/vomiting, occasional
  muscle cramps,sweating, body temperature near
  normal
• orthostatic dizziness/syncope may occur
• results in progressive hypovolemia
• Untreated can progress to heat stroke

12
Heat Exhaustion - two types classically described

• Salt depletion heat exhaustion
• takes longer to develop than water depletion form
• systemic symptoms occur
• hyponatremia, hypochloremia, low urinary sodium
  and chloride concentrations
• Symptoms similar to water depletion type, body
  temperature remains near normal

13
(No Transcript)
14
Heat Exhaustion Diagnosis

• Vague malaise, fatigue, headache
• Core temperature often normal if elevated less
  than 1040F
• Mental function essentially intact no coma or
  seizures
• Tachycardia, orthostatic hypotension, clinical
  dehydration (may occur)
• Other major illness ruled out
• If in doubt, --- treat as heat stroke !!

15
Heat Exhaustion - Treatment

• Rest
• cool environment
• Assess volume status (orthostatic changes, BUN,
  hematocrit, serum sodium)
• Fluid replacement
• Consider admission if patient is elderly, has
  significant electolyte abnormalities or would be
  at risk of recurrence if d/c

16

• A catastrophic life-threatening medical emergency
  ---
• HEAT STROKE

17
(No Transcript)
18
Heat Stroke Diagnosis

• Exposure to heat stress, endogenous or exogenous
• Signs of severe CNS dysfunction (coma, seizures,
  delirium
• Core temperature usually 410C (105.80F) or more,
  but may be lower
• Dry, hot skin frequent, but sweating may persist
• Marked elevation of hepatic transaminases

19

• In 80 of cases - sudden onset
• Patient becomes delirious or comatose
• Nonspecific Prodromal symptoms lasting minutes to
  hours occur in approximately 20 of cases -
  (reminiscent of heat stoke symptoms)

20

• There are two types of heat stroke -
• classic and exertional
• Both types characterized by
• extreme hyperthermia
• and multiple metabolic, hemodynamic abnormalities
  
• but arise in very different clinical settings

21
Hyperthermia

• A patient presents to the ED with elevated body
  temperature -
• 1st thought ??
• ? Infectious etiologies/severe infection
• but some patients with elevated temperature,
  including some with extreme pyrexia, do not have
  fever at all, they have hyperthermia !

22
Fever versus Hyperthermia

• Body temperature can become elevated through
  either of two very different processes
• In fever, thermoregulation remains intact while
  hyperthermia represents thermoregulation failure

23
(No Transcript)
24
Causes of Hyperthermia- Disorders of excessive
heat production

• Exertional hyperthermia
• Heatstroke (exertional)
• Malignant hyperthermia of anesthesia
• Neuroleptic malignant syndrome
• Lethal catatonia
• Thyrotoxicosis / Pheochromocytoma
• Salicylate intoxication / Delirium tremens
• Cocaine, amphetamines, other drugs of abuse
• Status epilepticus /Generalized tetanus

25
Causes of Hyperthermia- Disorders of diminished
heat production

• Heatstroke (classic)
• Occlusive dressings
• Dehydration
• Autonomic dysfunction
• Anticholinergics
• Neuroleptic malignant syndrome

26
Causes of Hyperthermia- Disorders of
Hypothalamic Function

• Neuroleptic malignant syndrome
• Cerebrovascular accidents
• Encephalitis
• Sarcoidosis and granulomatous infections
• Trauma

27
Hyperthermia
Splanchnic vasoconstriction
Thermal injury
Rhabdomyolysis
Disseminated intravascular coagulation
Diminished renal blood flow
Glomerular damage
Myoglobinuria
Hyperuricemia urinary acidification
Renal Failure
28
Classic Heatstroke

• Occurs primarily in epidemics during summer heat
  waves
• Most likely to effect the elderly and patients
  with serious underlying illnesses
• Infants also at risk
• Typical victim confined at home w/no fan or A/C
• Dehydration - predisposing factor

29
Classic Heatstroke

• Other risk factors - obesity, neurologic or
  cardiovascular disease, use of diuretics,
  neuroleptics, or medications with anticholinergic
  properties that interfere with sweating
• Alcohol use may be a risk factor

30
Exertional Heat Stroke

• Like classic heat stroke- occurs during hot,humid
  weather
• Occurs sporadically - effecting young, healthy
  persons engaged in strenuous physical activity

31
Exertional Heat Stroke

• Predisposing factors include acclimatization to
  the heat, lack of cardiovascular conditioning,
  heavy clothing and dehydration

32
(No Transcript)
33
Initial Treatment of Heat Stroke

• Immediate cooling
• Protect airway (intubate if comatose or seizing)
• IV line with 0.9 NaCl or Ringers lactate
• CVP or Swan Ganz catheter in hypotensive patients
• Foley catheter monitor output

34
Initial Treatment of Heat Stroke

• Rectal probe - monitor temperature
• Oxygen, 5-10L/min
• ABGs
• Labs - CBC, electrolytes, BUN, glucose, SGOT,
  LDH, CPK, calcium phosphate, lactate, PT/PTT,
  fibrin degradation products
• Check glucose by dextrostix method treate-
  administer D50 if hypoglycemia present

35
Cooling Modalities to lower body temperature in
heat stroke

• Ice-water immersion
• Evaporative cooling using large circulating fans
  and skin wetting
• Ice packs
• Peritoneal lavage
• Rectal lavage
• Gastric lavage
• Cardiopulmonary bypass
• Alcohol sponge baths (caution)
• Phenothiazines (caution)

36
Treatment of early complications of Heat Stroke

• Shivering
• Convulsions
• Myoglobinuria
• Acidosis
• Hypokalemia
• Hypocalcemia

37
(No Transcript)
38
Heat Illness Prevention

• A Crucial issue
• Counsel persons with any risk factors regarding
  symptoms of heat stroke
• Elderly persons
• persons with chronic diseases
• those on medications predisposing them to heat
  illness

39
Heat Illness Prevention

• Exertional heat stroke is most likely to strike
  young, healthy persons involved in strenuous
  physical activity
• many of these people have risk factors for heat
  illness -commonly obesity,diarrhea,febrile
  illness
• other variables to consider- hydration,salt
  intake, clothing, and climatic conditions

40
Heat Illness Prevention

• Fluid intake is the most critical variable

41
(No Transcript)
42
Questions ?