Heat Illness in Children

Transcription

1 Heat Illness in Children Charles G. Macias MD, MPH Baylor College of Medicine Attending Physician, Texas Children s Hospital Emergency Department Houston, Texas

2 Scope of the problem Heat stroke mortality defined as 17-70% Age dependent outcomes Bytomski JR, Curr Sports Med Rep 2003

3 Hyperthermia Temperature Normal temp 36 C-37.5 C (96.8 F-99.5 F) Hyperthermia defined by a core temperature 41 C (105.8 F) Hyperthermia from heat illness implies a temp above normal secondary to failure of thermoregulation

4 Thermoregulation Lee-Chiong TL; 1995; Pulmonary and Critical Care Medicine

5 Heat loss Radiation 60% of heat loss Evaporation sweating 25% Conduction bathing Convection air currents over the skin

6

7 Children vs adults Less than 2y/o suboptimal thermoregulatory control Increased body surface area to mass ratio Immature development of ability to sweat Higher metabolic rate than adults Slower rate of acclimitization Children at risk with decreased ability to sweat Congenital anhidrosis, CF, quadriplegia Infants cannot remove themselves from hot environments

8 Differential diagnoses for hyperthermia Drugs Amphetamines Cocaine Phencyclidine (PCP) Lysergic acid diethylamide (LSD) Antihistamines Phenothiazines Anticholinergics Beta blockers Salicylates Tricyclic antidepressants Endocrine Hyperthyroidism Pheochromocytoma Thyrotoxicosis Neuroleptic malignant syndrome Malignant hyperthermia Environmental Heat exposure Infectious Bacterial Viral Protozoan Specific diseases: meningitis, Rocky Mountain Spotted Fever, septic shock Malignancies Collagen vascular diseases

9 Hydration status determines risk for heat illness Sawka MN, US Army Institute of Envir Med 1996

10 Hydration status determines risk for heat illness Sawka MN, US Army Institute of Envir Med 1996

11 Hydration and hyperthermia Hypohydration resultant body water deficit when sweat output exceeds water intake Increased heat storage for a given core temp lower sweating rate (evaporative heat loss) reduced skin blood flow (dry heat loss) Reduced ability to tolerate heat strain reduces gastric emptying rate by 20-25%

12 Heat excess syndromes Excessive metabolic production of heat Excessive environmental heat Impaired heat dissipation

13 Heat excess syndromes Most cases occur during heat waves 3 consecutive days>90 F 1700 in 1980, 556 in 1983, 454 in 1988 Mass gatherings increase the risk Mass gathering hydration unit in Toronto Evoked at 450,000 to tx 3:10,000 Lukins JL, Prehosp Emerg Care 2004

14 2 day lag in heat waves: National Oceanic and Atmospheric Administration 1996

15 Heat excess syndromes Heat cramps Heat exhaustion Heat stroke

16 Drugs that worsen hyperthermia Cocaine Tranquilizers Alcohol Anticholinergic drugs Beta blockers Diuretics

17 Heat cramps Muscle cramps caused by sodium and/or potassium depletion Differential diagnosis Hypokalemia Diuretic abuse Black widow spider envenomation Management principles Rest the patient in a cool environment Replace salt with a salt containing oral rehydration solution

18 Heat exhaustion Caused by excessive sweating and inadequate fluid intake Management Assess ABC s and administer 100% oxygen Rectal temperatures with a hyperthermic thermometer for core body temperature Intravascular volume repletion CBC, serum electrolytes and urinalysis considered but generally not needed

19 Heat stroke Life threatening medical emergency Types Nonexertional: impaired heat dissipation Exertional: excessive heat production Death and permanent neurologic sequelae are possible with both types

20 Heat stroke: Non-exertional Also referred to as classic heat stroke Occurs from impaired heat dissipation More common in infants Develops slowly over a period of days Symptoms: Altered mental status Hyperventilation and tachycardia Nausea and vomiting Severe dehydration

21 Heat stroke: Exertional From excessive heat production More common in adolescent athletes who exercise vigorously on a hot day Develops rapidly Symptoms: Severe headache/altered mental status are common Syncope and hypotension Lactic acidosis, rhabdomyolysis, and disseminated intravascular coagulation Cardiovascular collapse with shock, seizures, delirium and coma

22 Evaluation Core body temperature by rectal hyperthermic thermometer Findings:

23 Sequelae Cardiac Cardiovascular collapse Fatty degeneration Muscle fiber rupture and necrosis Related laboratory analysis 12 lead EKG Non-specific ST segment and T wave changes

24 Sequelae Endocrine Hypoglycemia Increased levels of growth hormone and aldosterone Related laboratory analysis Glucose level

25 Sequelae Gastrointestinal Hepatic dysfunction Intestinal ulcerations, erosions, and hemorrhages Related laboratory analysis Aspartate aminotransferase

26 Sequelae Hematologic Disseminated intravascular coagulation Modest leukocytosis Thrombocytopenia Related laboratory analysis Prothrombin time Partial thromboplastin time

27 Sequelae Muscular Muscle swelling and pain Rhabdomyolysis Related laboratory analysis Creatinine phosphokinase Calcium (hypocalcemia)

28 Sequelae Nervous Cerebellar dysfunction Cerebral edema, hemorrhage, infection Related laboratory analysis Computerized tomography of head Serum sodium concentration (electrolytes)

29 Sequelae Pulmonary Pulmonary edema Related laboratory analysis Chest radiograph Pulse oximetry

30 Sequelae Renal Acute tubular necrosis Prerenal azotemia Proteinuria Related laboratory analysis Degree of acidosis: arterial blood gas ph decreases 0.05 per 1 C increase >37 C Respiratory alkalosis Renal function BUN and creatinine (elevated) Electrolytes (hypo/hyperkalemia, hypo/hypernatremia) Active sediment with erthrocytes and casts

31 Management: Initial Prehospital: remove patient from heat source to cool environment ED: Immediate recognition/treatment limits morbidity and mortality Stabilization of airway, breathing and circulation (ABC s) Intubate for extreme severity: comatose or seizure, profuse bronchorrhea, or inadequate ventilation Establish intrvenous access

32 Management: ED Rapid cooling Remove clothing Ice packs to the groin and axilla Water sprayed on the body and cool air blown across the patient Control shivering: 0.2 to 0.3 mg/kg of diazepam IV (neuroleptics; chlorpromazine) Aggressive cooling methods until rectal temperature is 38.5 C (gradual withdrawl at 39 C)

33 Management: ED Some children not responsive to traditional techniques Weiner and Khogali: Atomized shower 15 C (59 F) with warmed air 45 C (113 F) Internal cooling Cold water irrigation of stomach or rectum Peritoneal lavage Cardiopulmonary bypass Hydration with attention to renal function (diuretics)

34 Management: ED Caveats Must have continuous temperature monitoring or repeated measures to assess efficacy of treatment Cold induced cutaneous vasoconstriction should be minimized Water immersion can interfere with monitoring Vigorous skin massage decreases vasoconstriction Antipyretic measures not helpful

35 Management: ED Laboratory analysis if indicated Evaluate for presence of dehydration: bolus of 20cc/kg normal saline Foley catheter to monitor urine output PICU: continued monitoring of cardiovascular status, renal function, and electrolyte status if true heat stroke

36 Heat stroke Classic Chronic, incapacitating illness/ associated with intoxicants and meds Anhidrosis typical Rhabdomyolisis NOT common Worse prognosis Exertional Typically young and healthy Strenuous physical activity typical Rhabdomyolysis, renal failure, coagulopathy and hypoglycemia common Good prognosis

37 Conclusion Children at particular risk for heat illness Differentiate between: Heat cramps Heat exhaustion Heat stroke Cooling and rehydration critical Be aware of multi-system involvement

38 Prevention advice Avoid environmental risks Encourage comfortable clothing Keep hydrated Don t take on new activity until well acclimitized During exercise/sports, don t rely on thirst, schedule drinks

39 Preguntas?