Heat related illness

Heat related illness

1. Heat related illness SCGH ED CME 04/02/16 Leesa Equid

2. Overview Statistics Heat Illness Historical context Current practice Hypothermia Historical context Current practice Take-home points

3. Statistics Death from heat stroke – elderly, adults with comorbidities and young children restrained in cars Heat stroke mortality 10 -63 % (correlates with the temperature increase, time to cooling, number of organs involved) Exertional heat stroke the 3 rd leading cause of death in young athletes each year (1 st and 2 nd traumatic and cardiac) – increased BMI linked with h i gher risk as well as amphetamines for ADHD and dietary supplements Death from hypothermia – ethanol use, homelessness, psychiatric conditions, older age Only 10-33% of people survive if core temp <28 C

4. Heat Illness

5. Heat illness Definitions… Heat cramps Heat syncope Heat exhaustion Heat stroke Classic (non-exertional) heat stroke – CHS Exertional heat stroke – EHS

6. Heat illness Exercise-associated collapse – due to impaired compensation for ↓BP from cessatio n of muscle pumping and drop of venous return at cessation of exercise – a failure of prompt baroreceptors not haemodynamically significant dehydrations Heat stroke is rare and has distinct defining characteristics – altered neurological state with a core temperature > 41.5 C

7. Historical context – Heat Illness 1927 Vitalogy – an encyclopaedia of health and home Sunstroke – “most cases are preceded by pain in the head; wandering of the thoughts, or an inability to think at all; disturbed vision; irritability of temper; sense of pain or weight at the pit of the stomach” To avoid heat stroke “ 1. live in the country during the summer; 2 . never drink any whisky, wine or beer; 3. not to use severe exertion when the thermometer is over 90 in the shade” Treatment: lay in the cool, give ½ tsp ammonia by mouth or whisky/brandy/wine, repeat each 30 min

8. Heat illness Heat shock protein production Uncoupling of oxidative phosphorylation Blood shunting from splanchnic circulation to skin and muscle  gut ischaemia Multi-organ failure and DIC EVAPORATION RADIATION CONDUCTION CONVECTION  

9. Heat illness Heat shock protein production Uncoupling of oxidative phosphorylation Blood shunting from splanchnic circulation to skin and muscle  gut ischaemia Multi-organ failure and DIC EVAPORATION  main route, ineffective if humidity >75% RADIATION CONDUCTION  Ineffective if environment temp > body CONVECTION  

10. Heat illness Elderly D ecreased ability to deliver heat to skin D ecreased epidermal area for heat transfer Impaired vasodilation of skin Children Produce more metabolic heat per kg due to higher basal metabolic rate than adults Body surface area higher – absorb more heat Blood circulation – smaller blood volume Sweat production – lower rate of sweating Fluid replenishment – unlikely to replace fluid during exercise

11. Heat illness Classic (non-exertional) heat stroke Affects people with underlying medical conditions or impaired thermoregulation Exertional heat stroke Affects those undertaking heavy exercise in heat and humidity. Evidence to suggest these people are likely susceptible to malignant hyperthermia

12. Heat illness Signs Symptoms Febrile (rectal temp) Weakness Tachycardia Lethargy Tachypnoea Nausea, vomiting Wide pulse pressure Dizziness Orthostatic hypotension Altered mental state, coma Lung creps (non-cardiogenic pul monary oedema) CNS - i rritability, agitation, slurred speech, inappropriate behaviour, agitation, ataxia, poor coordination Seizure Delirium

13. Heat illness – heat stroke HR Postural BP RECTAL temperature Pulse oximetry Investigations… FBC, UEC, glucose, LFTs, CK, VBG (for lactate and metabolic status), coag profile, calcium, phosphate ECG CT head LP if altered mental state unexplainable

14. Heat illness – exercise-associated collapse Investigations: UEC CK To exclude exercise-associated hyponatraemia and rhabdomyolysis Lay supine, rest, give PO fluids If mental state doesn’t rapidly normalise when lay them supine check glucose and ECG for another cause Do NOT give IV fluids routinely – worsens hyponatraemia where there is persistent, inappropriate ADH levels

15. Heat illness - complications Complications Acute respiratory distress syndrome / aspiration / bronchospasm / non-cardiogenic pulmonary oedema / pneumonitis / pulmonary infarcts and haemorrhage Arrhythmias / cardiac dysfunction – stress-induced cardiomyopathy, DON’T CARDIOVERT UNTIL COOLED (unless VF or pulseless VT) Disseminated intravascular coagulation – monitor coag profile for 3 days Acute kidney injury – give fluids Hepatic injury – often self-limiting, may progress Hypoglycaemia – give sugar Rhabdomyolysis – treat as per rhabdo management (sodium bicarcarbonate and mannitol 20%) Seizures – give benzos and cool Hypotension – don’t give alpha-blockers, give fluids

16. Heat illness - diagnosis Diagnosis requires… Increased core body temperature CNS dysfunction Exposure to severe environmental heat Differential diagnosis – infection, endocrine, CNS, status epilepticus, neuroleptic malignant syndrome, thyroid storm, malignant hyperthermia, oncological, toxicological (ETOH, amphetamines, cocaine, salicylates, hallucinogens, lithium)

17. Heat illness - treatment Treat hypotension and volume depletion with IV crystalloid Cool until temp 38-39 C Evaporative cooling – mist of lukewarm water, fans Ice packs to axilla, groin, neck, towels soaked in bowls of iced water, applied to the skin and changed regularly Ice water/immersion for younger patients with exertional heat stroke **used in the field IV benzodiazepines to suppress shivering Cooled oxygen, IV fluids and blankets Don’t give antipyretics – they don’t work!

18. Heat illness – exertional specific… On scene… ABCs, finger glucose, rectal temperature, serum sodium If altered mental state – rapid cooling needed asap “Cool first, transport second” (to 38.9 C) Ice water immersion 15-20 min decreases core temp by 3-4 C, assuming cooling rate 0.21 per minute Secondary survey Assess mental state Check muscle compartments for compartment syndrome Check all orifices for bleeding

19. Heat illness – exertional specific… Investigations – FBC/UEC/Ca/urinalysis/CK/LFTs/ coags / ECG/VBG/CXR/CT Head Supportive care Cooling Fluid resuscitation (be aware of volume status, urine output, cardiac function) Correct electrolyte abnormalities Diagnose and treat complications (CNS dysfunction, rhabdomyolysis, AKI, acute liver failure, DIC)

20. Heat illness – exertional specific… Return to play Not until asymptomatic and all blood tests normal No exercise for 7 days, then repeat bloods Then “common sense” approach – gradual, cautious reintroduction to exercise

21. Time is brain The primary goal in heat stroke is rapid and aggressive cooling The maximum core temp and duration of high temp are predictors of morbidity and mortality

22. Hypothermia

23. Historical context 1927 Vitalogy – an encyclopaedia of health and home Freezing – treatment: rub with snow or ice-cold water in a room without a fire, after time wipe them dry and apply flannels, give a little weak warm wine/brandy from time to time. Do not apply heat or have a fire in the room, it is dangerous to your patient” If breathing has ceased the case may be hopeless, or treat as per drowning…

24. Historical context Expelling water from body: lay face down, press on the back for 1 minute T o produce breathing – pull the tongue to the side, lift the patients arms above their head, squeeze the stomach as the arms are lowered to the side. Repeat 12-15 times per minute, imitating the natural motions of breathing

25. Hypothermia Mild hypothermia – poor judgement, lethargy, ataxia, shivering, tachypnoea (core temp 32-35 C) Moderate hypothermia – bradycardia, hypotension, bradypnoea, confusion, no shivering (core tem 28-32 C) Severe hypothermia – comatose, may appear dead with no pulse, absent reflexes, unrecordable BP and fixed pupils (core temp<28 C) Stages are more important than boundaries of recorded temperature, except level of consciousness should be consistent with core temperature

26. Hypothermia Swiss Staging System I – clearly conscious and shivering II – impaired consciousness without shivering III – unconscious IV – not breathing V – death due to irreversible hypothermia

27. Hypothermia EVAPORATION – vaporisation of water via insensible losses and sweat RADIATION – emission of infrared electromagnetic energy CONDUCTION – direct transfer of heat to an adjacent, cooler object CONVECTION – direct transfer of heat to convective currents of air/water Essentially… Increased heat loss Decreased thermogenesis Impaired thermogenesis

28. Hypothermia Central and peripheral thermal receptors  hypothalamus  shivering and increased thyroid, catecholamine and adrenal activity, vasoconstriction of peripheral tissues and blood vessels Vital signs inconsistent with degree of hypothermia suggests an alternate diagnosis

29. Hypothermia Elderly Decreased physiological reserve Chronic diseases Medications Social isolation BEWARE of sepsis presenting as hypothermia, if unexplained hypothermia treat with empirical antibiotics

30. Hypothermia - resuscitation Move gently, may trigger VF if temp <32 C Use Doppler if unable to palpate a central pulse No adrenaline or other drugs until core temp >30 C Double drug dose times with temp 30-35 C Shock VF up to 3 times then nil further until temp >30 C Prolonged CPR may be indicated – as hypothermia is neuroprotective “Not dead until warm and dead”

31. Hypothermia - consequences CVS – bradycardia, arrhythmias Resp – decreased CO2 prod, increased dead space, met acidosis, pulmonary HTN CNS – neuroprotective, fixed dilated pupils if temp <30 GIT – decreased hepatic metabolism, decreased splanchnic circulation Renal – reduced GFR, cold-induced diuresis Metabolic – shivering, left shift oxy-HB dissociation curve, ↑ glucose, decreased drug metabolism Haem – increased PT and APTT, VTE risk, ↓plt and WCC

32. Hypothermia - ECG ECG changes from slowed impulse conduction through K channels  prolongation of all ECG intervals Elevation of J wave – J/Osborn wave, size related to degree of hypothermia Bradyarrhythmias (sinus, AF, junctional, 1 st -3 rd AV block) Shivering artefact Ventricular ectopics Cardiac arrest due to VT, VF or asystole

33. Hypothermia Assessment –Use a rectal or bladder probe for diagnosis, however they lag behind core temp during rewarming, use oesophageal Ix Glucose ECG UEC Calcium FBC VBG (incl lactate)* Fibrinogen CK TFTs C onsider tox screen Serum cortisol Lipase CXR Hyperglycaemia in rewarming – suggests pancreatitis or DKA (NOTE: insulin is ineffective at temp below 30 C) *VBG – temperature uncorrected values

34. Hypothermia - warming Passive warming (If patient can shiver) Peripheral active warming Central active warming Warm environment Heat pads Warmed humidified inspired gases Blankets (aluminium) and hat Forced air warming blankets Warm IV fluids Let them mobilise Warm baths Body cavity lavage Warm blankets ECMO/bypass Shivering 1.5 C/hr Warming blanket 2 C/hr Warm O2 w mask 1 C/hr Warm O2 w ETT 1.5 C/hr Warm IV fluids NAD Peritoneal lavage 3 C/hr Cardiac bypass 9-18 C/hr Thoracic lavage 3-6 C/hr

35. Hypothermia - cases

36. Recommendations HEAT STROKE - Think of an alternate diagnosis, but don’t wait – time to cooling affects mortality. “Cool quickly, time is brain” HYPOTHERMIA – Remember the effect on resuscitation. Cold is neuroprotective “Not dead until warm and dead”

37. References A Brown, M Cadogan . Emergency Medicine 6 th Edition LifeInTheFastLane – Hypothermia ECGs I Rogers. Heat related illness in: Textbook of Adult Emergency Medicine 2015. C Craford Mechem . Severe nonexertional hyperthermia (classic heat stroke) in adults. UpToDate . Dec 2015 FG O’Connor, DJ Casa. Exertional heat illness in adolescents and adults: Management and prevention. UpToDate . 2016 P Ishimine , DF Danzl . Heat stroke in children. UpToDate . Dec 2015. HM Corneli , RG Bolte . Hypothermia in children: clinical manifestations and diagnosis. UpToDate . Dec 2015 K Zafren , C Crwaford Mechem . Accidental hypothermia in adults. UpToDate . Dec 2015

38. Questions?