열손상

Abstract

Heat Injury

한양대학교 구리병원 응급의학과 강보승

평소 건강하던 45세 남자환자, 9월경 마라톤 도중 발생한 실신과 경련을 주소로 본원 응급센터에 내원.

내원당시 생체징후는 혈압 120/75mmHg, 맥박수 110회/분, 체온 38.9도(섭씨)

의식은 혼수상태, 간헐적인, 30초 정도 지속하는 경련을 보였고 사지 근육의 tone은 rigidity를 보이는 것 같았다. 사지와 몸통의 피부는 뜨끈뜨끈했다.

Diagnostic work-up ?

혈액검사 상 CBC; 17,000-14.0-170,000 e’ ; 145-5.8-109 BUN/Cr; 60/2.7 AST/ALT; 460/390 T.Bil; 2.5 ALP/GGT (normal) CK 2300 뇨 검사상 blood 3+, ketone 2+

종류 Heat cramps Heat syncope Heat exhaustion Heat stroke - exertional & nonexertional who Major environmental risk factor - heat stress on a constant basis without air conditioning breaks during the night Death & weather ‘ heat waves’ ? 3 or more consecutive days of sustained temp. above 32.2oC How ? Body’s heat loss-mechanism Radiation Conduction Convection Evaporation How ; heat loss-mechanism Radiation - 1o heat loss mech. In lower temp. by infrared radiation flowing 외부 온도 < 체온

Evaporation : 1o heat loss mech. In higher temp. accounts for virtually 100% at high temp. - by sweating (dehydration / humidity) How ; heat loss-mechanism Conduction -kinetic energy of moving molecule of surface (warmed ? cooler) -[water >> air] 32 times efficient at same temp. Convection -removing warmed air next to the skin and replacing it with cooler air ? conductive heat loss -limits: 32.2도 & 35% 습도 (fan alone ?) Types: non-exertional Classic heat injury - during periods of high environmental temp. - “heat waves” Confinement hyperpyrexia - children left inside cars - 54-60도 - illegal immigrants (U.S. border-Mexico) Types: Exertional heat injury - athletic event, military circumstances - heat production + heat gain > removal proc. - core temp. increase: 0.3도/min - dehydration - heat index chart( 기온, 습도 ) How ; heat loss-mechanism Acclimatization - increase efficiency of heat loss in a hot climate - onset and volume of sweat Diagnosis Core temp. > 40도 CNS dysfunction (seizure, coma, irri., any) Anhydrosis ? Diagnosis of exclusion - CNS infection, status epilepticus, cbr. hemorrhage, NMS Neurologic injury - lower temp. for longer period : worse Management Initial resuscitative measure(OTI,,,) Crystalloid sol. Infusion Monitoring of rectal temp. Routine blood test / cranial CT Cooling technique - core temp. < 40도 (primary goal) - antipyretics ? - evaporative cooling/cold-water immersion

Management - complication Rhabdomyolysis ARDS Acute renal failure Hepatic necrosis DIC Thrombocytopenia

Hypothermia Who, Why ? Core temp. < 35도 In U.S., 700 die per yr. (half: > 65 yr.) “accidental” (most common) - immersion / non-immersion - water colder than 16-21도 : severe hypo. ? ‘intoxicated’ ( alcohol: most common )

Who, Why ? 32-35도 : mild hypothermia - attempts to retain and generate heat Below 32도 : slowdown of metabolism - shivering cease(major sourse-H. production) How ? Osborn (J) wave: not pathgnomonic Risk for dysrhythmia: below 30도 Typical sequence of dysrhthmia - s. bradycardia ? AF-SVR ? VF ? asystole Kidney -concentrating power 감소 ; cold diuresis DIC / embolic Cx. - hemoconcentration / poor circulation - release of tissue TP during rewarming Management General supportive / specific rewarming Gentle handling - VF in irritable hypothermic myocardium Chest compression ? VF (be careful !) Most dysrhythmia - require no therapy - revert spontaneosly with rewarming - hypothermic heart resistant to atropine, counter shock, pacing - Management VF - refractory to therapy until pt. rewarmed Guideline 2000: - initial defibrillation attempts(up to 3 shocks) - defib. should be reattempted when core temp. reaches 30oC.

Management Rewarming - passive rewarming - active external rewarming : warm water immersion, heating blankets - active core rewarming at 40oC : heated IV fluid, GI tract-bladder-peritoneal lavage Rapid rewarming - dysrythmia, unstable cardiovascular status - rarely needed at temp. above 30oC