2/13/2014 Lori Weichenthal, MD, FACEP Associate Professor of - PDF document

2/13/2014 Lori Weichenthal, MD, FACEP Associate Professor of Clinical Emergency Medicine UCSF Fresno 1

2/13/2014 INTRODUCTION • Th Thermoregulat lation on • Acclimatization Acclimatization • Field Managem Field Management nt of Heat Illness of Heat Illness • Solar Injur Solar Injury • Questions and Conclusion Questions and Conclusion THERMOREGULATION • The The body regulat body regulates t s temperature lik erature like a a furnace furnace • The h The hypo pothalamus is the thermostat thalamus is the thermostat • It responds It responds to v variou rious recept receptors s • Adjust t just to keep eep core t core temperature betw erature between 36.5 een 36.5 and 3 and 37.5 .5 degrees degrees Celsius Celsius 2

2/13/2014 THERMOREGULATION Reactions at a actions at a cellular le cellular level are l are • mainly e mainly exothermi rmic At rest, rest, a a human generat human generates es • about 1 about 100 kcal/hr 00 kcal/hr. Moderat Moderate activity adds activity adds an an • additional 300-600 kcal/hr additional 300-600 kcal/hr. Solar radiation adds 150 Solar radiation adds 50 • kcal/hr kcal/hr. THERMOREGULATION Heat can be lost Heat can be lost • and gained fr and gained from om the body b the body by:  Ev Evaporation aporation  Radiation Radiation  Conduction Conduction Con Convection ection  3

2/13/2014 EVAPORATION Most ef Most efficient cooling mechanism cient cooling mechanism • Respirat spirator ory loss and y loss and sw sweat eat • Acco counts f unts for 30 % of heat dissipation at r 30 % of heat dissipation at • average e erage external t rnal temperatures eratures Major cooling mechanism at Major cooling mechanism at temperatures eratures • great greater that 35 degrees Celsius r that 35 degrees Celsius 4

2/13/2014 RADIATION Transf ansfer of heat betw er of heat between the body and een the body and the the • en envir vironment via electr nment via electromagnetic w omagnetic waves Ov Over 50 % of cooling when ambient er 50 % of cooling when ambient • temperature is erature is less than body t less than body temperature erature Why Wh y it is im it is impor portant ant to co cover up when it is cold r up when it is cold • CONDUCTION Transf ansfer of heat betw er of heat between tw een two objects that are o objects that are • in direct contact in direct contact Heat loss is Heat loss is minimal e minimal except with: cept with: •  Water immersio r immersion  Lying on cold gr ing on cold ground ound 5

2/13/2014 CONVECTION Heat transf Heat transfer betw er between the body and een the body and a a mo moving ving • gas or liq gas or liquid id Rat Rate of heat transf of heat transfer is er is dependent on: dependent on: •  Speed of air Speed of air or w or water  Temperature of each substance erature of each substance In still air, 25 In still air 25 % of heat % of heat loss is loss is via con via convection tion • As wind speeds up, becomes As wind speeds up, becomes great greater • 6

2/13/2014 HEAT ACCLIMATIZATION • Re Requ quires u up to to 1 14 d days • Ear Early • Reduced heart rate • Expanded plasma volume • Autonomic nervous system habituation • Lat Late • Increased sweat rate/production • Conservation of sodium HEAT ILLNESS Ph Physiologi ysiologic R c Response sponse • Pat Pathoph ophysiology siology • Presentation Presentation • Management Management • Pre Prevention ention • 7

2/13/2014 PHYSIOLOGIC RESPONSE TO HEAT Hypo pothalamus at thalamus attempts t ts to maintain id maintain ideal eal bod body • te temp mperature Shun Shunts bloo ts blood • Vasodilation, es dilation, especially o cially of s skin  Splanchnic v lanchnic vasoconstriction constriction  Increases cardia Increases ca iac out c output ut • Increased cat Increased catecholam cholamines ines activ activate sw sweat glan eat glands ds • Ad Adaptive ve r responses • PATHOPHYSIOLOGY OF HEAT ILLNESS Ph Physiologi ysiologic response de c response deteriorat riorates as es as car cardiac iac • outpu output and and vasodilatatio sodilatation reach their limits reach their limits Electr Electrolyt olyte losses and e losses and deh dehydration contribut dration contribute • to pr progr ogression ssion Serious heat illness o Serious heat illness occur ccurs when when normal body normal body • temperature can erature can no not be t be maintained maintained Is a spectrum Is a spectrum • 8

2/13/2014 RISK FACTORS FOR HEAT ILLNESS Elderly Elderly Hyperthyroidism Hyper idism • • Neonat Neonates es Medicatio Medications • • Obesity Obesity Drugs of abuse Drugs of abuse • • Alcoho Alco holis lism Socioeconomic Socioeconomic • • Deh Dehydratio dration Conf Confinement inement • • Extreme activ Extre e activities ties • TYPES OF HEAT ILLNESS Heat edema Heat edema • Heat rash Heat rash • Heat cram Heat cramps ps Mild to • severe Heat synco Heat syncope • Heat e Heat exhaus haustio tion • Heat str Heat stroke • 9

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2/13/2014 CASE SCENARIO You u are ser are serving ing as a medical as a medical volunt lunteer eer for the Badw r the Badwat ater Ultra maratho er Ultra marathon at at an an aid aid station at station at St Stovepipe W epipe Wells, at lls, at the 42 mile point f the 42 mile point for the race, when a r the race, when a bystander appr stander approaches y oaches you concerned u concerned that she has increased lo that she has increased lower r extremity edema since arriving t tremity edema since arriving to Deat ath V Valley f y from Ont om Ontario, Canada o, Canada . 11

2/13/2014 HEAT EDEMA-PRESENTATION Sw Swelling of e elling of extremities associat tremities associated with high ed with high • temperatures eratures Occurs during heat w Occurs during heat waves or when a s or when a per person on • fr from a om a cool climat cool climate tra e travels t els to a a warm one rm one Body retains w Body retains water and r and has tr has trouble e ouble excre creting ing • salt salt Due t Due to an an increase in increase in aldost aldoster erone one • HEAT EDEMA-TREATMENT Move t Mo to a a cool space cool space • Provide cool fluids Pr ide cool fluids • Ele Elevat ate sw e swollen e ollen extremities tremities • Allow time f Allo w time for acclimatization r acclimatization • 12

2/13/2014 CASE SCENARIO Still at Still at your post at ur post at St Stovepipe W epipe Wells, a lls, a staf staff f memb member f er for the race a r the race appr pproaches oaches y you with the u with the com complaint of a laint of a red red itch itchy rash. y rash. She is She is extremely tremely uncomfor uncomf ortable table and and is asking y is asking you what u what to do. do. HEAT RASH-PRESENTATION Also kno Also know as prickly heat or milaria as prickly heat or milaria • De Develops when sw lops when sweat du eat ducts beco cts become me blo blocked • Presentation ranges fr Presentation ranges from om super superficial blist ial blisters • to deep, deep, red bum red bumps Usually in folds of skin or where clo Usually in lds of skin or where clothing hing • causes friction with skin causes friction with skin Symp mptoms ms r range f from a om asymptoma omatic r ic rash t to • se severe itch re itchy/prick y/prickly rash y rash 13

2/13/2014 HEAT RASH-MANAGEMENT Usually g goes aw away ay o on its o own • Keeping skin eeping skin cool cool and pre and preventing enting sw sweat eat is is • helpfu helpful  Dress in Dress in loose, lightw loose, lightweight clo eight clothing hing  Sta Stay in in air air conditioning conditioning Af After bathing, let y r bathing, let your skin ur skin air air dr dry   Use calamine lo Use calamine lotio tion or coo or cool com compresses In se In severe cases, st re cases, ster eroids ma oids may be y be req require ired • CASE SCENARIO As the runner As the runners star s start t t to reach y reach your aid ur aid station, a station, a 45 y 45 year old male par ar old male participant presents with icipant presents with se severe right calf cra re right calf cramping that ping that mak makes him him unable t unable to w walk or run. lk or run. 14