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 Emergency Medicine What we’ll cover… • Basics of heat related illnesses • Risk factors/etiology • Heat cramps • Prickly heat • Heat edema • Heat syncope • Heat exhaustion • Heat stroke • Workups, treatments/cooling measures, dispositions Let’s start with the basics… • Wide range of progressively more severe illnesses • Increasingly overwhelming heat stress • Basic dehydration 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/humidity • Prolonged exertion • Lack of mobility • Lack of air conditioning • Lack of acclimatization • Occlusive, nonporous clothing Pediatrics • A special note on pediatric patients: Children are at increased risk of heat illness 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) • Hyponatremia • Hypochloremia • Without rhabdomyolysis 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 Heat syncope • 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 • Fatigue/malaise • Impaired judgement • Vertigo • Agitation • No severe CNS dysfunction Heat exhaustion • Cardiovascular • Mild tachycardia • Dehydration • Pulmonary • Tachypnea • GI • Nausea • Vomiting • Skin • Perspiration 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 thermoregulation/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 • Hyperthermia • CNS dysfunction • Hot skin • Usually anhidrotic, no sweating, but can sometimes still sweat Heat stroke • Core temperature >40.5 C • CNS • Severe confusion / delirium • Lethargy / coma • Seizure • Ataxia • CV • Tachycardia • Hypotension • Conduction disturbances Heat stroke • Pulmonary • Tachypnea • Rales due to non-cardiac pulmonary edema • Respiratory alkalosis (can lead to tetany) • 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 meningitis/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 Differential Diagnosis • Febrile illness/sepsis • Thyroid storm • Pheochromocytoma • Cocaine/PCP • Anticholinergics • MAO Inhibitors • Meningitis/Encephalitis • Cerebral falciparum malaria • Delirium Tremens • Neuroleptic Malignant Syndrome • Malignant Hyperthermia • Serotonin syndrome • 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 hypothermia • 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! .