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Home , Heat illness, Heat stroke, Heat syncope

Heat Related Illnesses

Refresher Course for the Family Physician 4/3/20 Brooks J. Obr MD MME University of Iowa Hospitals and Clinics Department of What we’ll cover…

• Basics of heat related illnesses • Risk factors/etiology • Heat cramps • Prickly heat • Heat edema • Heat • • • Workups, treatments/cooling measures, dispositions Let’s start with the basics…

• Wide range of progressively more severe illnesses • Increasingly overwhelming heat stress • Basic   Thermoregulatory dysfunction/organ failure • Normally, body temperature is maintained by balancing heat production with heat loss/dissipation Etiology

• Pre-existing conditions hindering the body’s ability to dissipate heat predispose for heat-related illness • Age extremes • Dehydration (gastroenteritis, inadequate fluid intake, etc.) • Cardiovascular disease (CHF, CAD, etc.) • Obesity • Diabetes mellitus, hyperthyroidism, pheochromocytoma • Febrile illness • Skin diseases that hinder sweating (psoriasis, eczema, cystic fibrosis, scleroderma, etc.) Etiology

• Pharmacologic contributors • Sympathomimetics • LSD, PCP, Cocaine • MAO inhibitors, antipsychotics, anxiolytics • Anticholinergics • Antihistamines • Beta-blockers • Diuretics • Laxatives • Drug/ETOH withdrawal Etiology

• Environmental factors • Excessive heat/ • Prolonged exertion • Lack of mobility • Lack of • Lack of acclimatization • Occlusive, nonporous clothing Pediatrics

• A special note on pediatric patients: Children are at increased risk of due to increased body surface area to mass ratio, lower sweat production Heat cramps Heat cramps

• Cramps in heavily worked muscles • Profuse sweating  rehydration with hypotonic fluid (e.g. water) • • Hypochloremia • Without or renal damage Heat cramps

• Treatment • Oral salt solutions if minor • NS IV if severe Prickly heat

• Pruritic maculopapular/vesicular rash over clothed areas • From profuse sweating in tight clothing • Due to blockage of pores/secondary staphylococcus infection • Treatment: Usually clears up when sweating is avoided • Keep skin cool and dry • Chlorhexidine cream/lotion Heat edema

• Nonacclimatized people • Swelling of feet/ankles from environmental heat • Due to vasodilation, orthostatic pooling, and increased aldosterone Heat edema

• Treatment • Elevation • Compression stockings • Acclimatization

• Unexplained syncope in setting of heat exposure with prolonged standing • Especially in elderly • Cutaneous vessels dilate to dissipate heat • Decreased central blood volume  syncope • Tx: Self-limited • Lay patient flat Heat exhaustion

• Core temperature moderately elevated, usually <40 C. • Not > 40.5 C. • Fluid/salt depletion occurs as a result of heat stress • CNS function is preserved • Variable nonspecific symptoms • Thermoregulatory function maintained • If left untreated, will progress to heat stroke Heat exhaustion

• CNS • Frontal headache • /malaise • Impaired judgement • Vertigo • Agitation • No severe CNS dysfunction Heat exhaustion

• Cardiovascular • Mild tachycardia • Dehydration • Pulmonary • Tachypnea • GI • • Vomiting • Skin • is PRESENT, usually profuse Heat stroke

• Core body temp >40.5 C • Failure of thermoregulatory function  Severe CNS dysfunction and multisystem organ failure. • Two types • Classic (nonexertional) • Exertional Heat stroke

• Classic heat stroke (nonexertional) • Occurs in patients with compromised /inability to remove themselves from a hot environment • Extremes of age, debilitated, etc. • Exertional heat stroke • Younger, athletic patients • Combined environmental and exertional heat stress (e.g. military recruits) • Develops over the course of hours • Internal heat production overwhelms dissipating mechanisms Heat stroke

• Classic triad • • CNS dysfunction • Hot skin • Usually anhidrotic, no sweating, but can sometimes still sweat Heat stroke

• Core temperature >40.5 C • CNS • Severe / • Lethargy / • • Ataxia • CV • Tachycardia • Hypotension • Conduction disturbances Heat stroke

• Pulmonary • Tachypnea • Rales due to non-cardiac pulmonary edema • Respiratory alkalosis (can lead to ) • Hypoxemia (aspiration, pneumonitis, pulmonary edema, high metabolic demand) • GI • Nausea • Vomiting • Diarrhea Heat stroke

• Skin • Cutaneous vasodilation (hot skin) • USUALLY dry, but sweating may be present if not dehydrated • Acute oliguric renal failure due to dehydration/rhabdomyolysis • Hepatic failure • Elevation of transaminases to tens of thousands • Coagulopathy, including DIC (poor prognosis) • Purpura, melena, hematochezia, hematuria, CNS hemorrhage Workup- Heat exhaustion/stroke

• Accurate core temperature • History of heat exposure • Heat exhaustion/stroke is a diagnosis of exclusion • Core temperature > 40.5 C and CNS dysfunction required to make diagnosis of heat stroke Workup- Heat exhaustion/stroke

• CBC • Leukocytosis • Hemoconcentration • CMP • Hypernatremia with severe dehydration • Hyponatremia if drinking copious free water • Acute renal failure? Workup- Heat exhaustion/stroke

• UA • Myoglobin present in rhabdomyolysis • Blood/Urine cultures to rule out septic etiology • Toxicology screen • Serum creatinine kinase (to rule out rhabdomyolysis) • Lactate elevation? • ABG • Acidosis common with exertional heat stroke Workup- Heat stroke (more specifically)

• PT/PTT/DIC panel • Poor prognosis if DIC present • Liver panel • Troponin I • Poor prognosis if elevated • Consider lumbar puncture to distinguish from /encephalitis Workup- Imaging

• EKG in elderly / patients at cardiac risk • CT head for altered mental status • CXR for ARDS, aspiration pneumonia, and to evaluate for septic etiology

• Febrile illness/ • Thyroid storm • Pheochromocytoma • Cocaine/PCP • Anticholinergics • MAO Inhibitors • Meningitis/Encephalitis • Cerebral falciparum • Delirium Tremens • Neuroleptic Malignant Syndrome • Malignant Hyperthermia • • Etc. Treatment

• Initial stabilization/therapy • ABCs • Obtain continuous core temperature monitoring (rectal or esophageal probe) • Rapid cooling if temperature >40 C (more on this in a second) • IV fluids if hypotensive • If altered mental status… • Check glucose/administer D50 if needed • Thiamine? • Naloxone? Treatment- Cooling measures

• Initiate for temp >40 C • Evaporative cooling • Extremely effective! • .05 - .3 C/min • Spray disrobed patient with fine mist of warm water (prevents shivering) • Airflow with fans blowing over patient • Advantages • Practical, well tolerated • Readily available • Disadvantages • Can cause shivering • Less effective in humid environments • Can make it difficult to maintain electrode positions Treatment- Cooling measures Treatment- Cooling measures

• Conductive cooling • Ice packs to groin/axilla/neck • Advantages • Practical • Can be added to other cooling methods • Disadvantages • Cooling times longer than other modalities • Not always well tolerated • Iced/cold water immersion • Advantages • Effective • Disadvantages • Impractical • Poorly tolerated • Can cause shivering Treatment- Cooling measures

• Cooling blankets • Advantages • Easy to apply • Disadvantages • Limited cooling efficacy • Impede use of other cooling methods Treatment- Cooling measures

• Refractory cases • Cardiopulmonary bypass • Advantages • Fast • Effective cooling • Disadvantages • Invasive • Not readily available • Setup extremely labor intensive Treatment- Cooling measures

• Stop cooling therapy at 39 C • Avoid overshooting and causing • Antipyretics • Not helpful • Underlying mechanism doesn’t involve change in hypothalamus set point Supportive measures

• Rehydration for heat stroke/heat exhaustion • Initial rehydration with .9% NS • Aggressive fluid resuscitation until BP >90/60 • Avoid overhydration (pulmonary edema, ARDS) • Peds: 20 cc/kg bolus initially • Place foley to monitor urine output Supportive measures

• Benzodiazepines • Seizure • Agitation • Stops shivering • Tachyarrhythmias can develop • Usually resolves with cooling Further cares

• Monitor serum electrolytes every hour initially • Treat hyperkalemia and DIC with standard regimens • Treat rhabdomyolysis with IV hydration Admission criteria

• Heat stroke- admit to ICU • Heat exhaustion- admit to general or monitored floor if: • Severe electrolyte abnormalities • Renal failure/evidence of rhabdomyolysis • Elderly / significant comorbidities • Patients other than those with heat stroke/severe heat exhaustion likely can discharge depending on clinical scenario. PEARLS

• Can’t make diagnosis of heat stroke without temp >40.5 and severe CNS dysfunction • Management of heat stroke requires management of ABCs and rapid cooling • Continuous core monitoring with rectal/esophageal probe • Evaporative cooling is the cooling method of choice Thank you!