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That’s Hot! Dr. Kelly Kasteel

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1 That’s Hot! Dr. Kelly Kasteel
Case Study-hyperthermia

2 Hyperthermia: Epidemiology
4,000 heat related deaths yearly (US) 80% of the fatalities are elderly Occurs in 5 per million over age 85 compared to 1 per million in the 5-44 age group 2nd leading cause of death among young athletes Very young (<4yo) also at increased risk Occurs in 0.3 per million compared to 0.05 per million in patients > 4yo.

3 Case Study-History 36 y.o female
Admitted-RCH 2011 (73 previous visits) Vancouver is experiencing a rare heat wave where outside temperatures have ranged between degrees Brought in via EHS agitated, spitting, naked and running into traffic at the scene. Hx of ? 45 second seizure en route to the hospital which is not clearly documented. Remote history of foul stools over the previous week before admission Without complaint at arrival, but…had precipitous decrease in LOC and was intubated for airway protection

4 Case Study-History PMHx Meds Allergies SHx 1. Hepatitis C. 2. BAD
None. Previously (1/12) on Risperidone-2mg qhs via pharmanet Allergies None SHx Prostitution – multiple STD’s in past Polysubstance abuse (cocaine/heroine IVDU). Last used this am

5 Case Study-On Examination
HR-144 reg/ RR-22/ Temp-41 C/ BP-90/40/ Pressure support 15, PEEP of 5, FiO2 of 0.5, CPP was 11, mixed venous 81% and a MAP of 75 with no pressor support.  Spent 8 hrs in ED before transfer to ICU

6 Case Study-On Examination
CVS-s1s2 no murmur no s3s4 Resp- eae no wheeze no crackles Abdo-soft non-tender GU – ++discharge, no FB Neuro- Initially the ED, the pt was confused and combative with a GCS E3M5V2 = 10. Moving all 4. Pupils 3 reactive. MSK- Injection marks over antecubital space Derm- Warm and Dry

7 Case Study- Labs Glucose-6.8 Sodium-142 Potassium-5.4 Chloride104
Bicarb 11 Urea 6.3 Creatinine 147 Total Bili 8 Osmolality 319 Anion Gap-27 CK -405 Troponin0.19 Amylase-1018 TSH -0.52 B-HCG- weakly positive Ethalene glycol/methanol- cancelled Tox serum screen (asa- weakly positive 0.2, acetaminophen, etoh)-negative

8 Case Study- Labs Infectious workup
Genital C/S- Normal flora Stool C/S – Negative Sputum-Negative Urine –Negative Blood C/S- 1 bottle gram positive cocci in clusters-coag negative staphlococcus Hypoglycemia- Glucose-0.7 (24 hrs after admission) Hyponatremia-Sodium-128 ARF-Creatinine-600 APTT-189 INR >9 (july 12) Fibrinogen-1.0 D- dimmer >4000 Hepatitis-AST 1000, ALT 5573, GGT 66, BR 666(total)) Blood smear-schistocytes, burr cells

9 Case Study-Imaging CT head- July 24th
There is severe compression of structures in the fourth ventricle.   Fluid around the brainstem has been effaced and the fourth ventricle is compressed.  The patient is at risk for developing transtentorial or tonsillar herniation. Severe cerebral edema.  CXR: small lung volumes, no obvious airspace disease

10 Case study- Course in Hospital
Treated presumptively as sepsis nyd- piptazo, flagyl Negative workups – no identifiable septic or obstetrical causes for DIC. July Patient briefly extubated before re-intubation and markedly decreased LOC. Brain Death Comfort care initiated July 24th, patient deceased within the hour. Autopsy- Non-contributory to date-MOS

11 Now That’s HOT What is your differential diagnosis for this pt?
What are the potential complications that can occur in heat stroke? What investigations should you order? What other therapies should be considered?

12 Basic principles of Heat
4 mechanisms that allow the body to maintain a constant core temperature Radiation Convection Conduction Evaporation Radiation Transfer of heat by electromagnetic waves The primary mechanism of heat loss in a cool environment Convection Heat exchange between the skin and the air molecules around the body Affected by wind wind = convective heat loss Conduction Heat exchange between 2 surfaces in direct physical contact with one another Individual mediums differ in their ability to conduct heat Air/Fat = poor heat conductors Water = good heat conductor Evaporation Conversion of a liquid to a gas at the expense of energy For humans, the liquid being converted is sweat Affected by humidity humidity = evaporation

13 Fever vs. Hyperthermia Fever Hyperthermia
Elevation of body temp due to the “resetting” of the hypothalamic set point in response to endogenous or exogenous pyrogens Hyperthermia Elevation of body temp above the hypothalamic set point due to the failure of the body’s heat dispersing mechanisms

14 Diff Dx - Hi temp with altered mental state

15 Heat Stroke Total breakdown of body’s thermoregulatory system
Leads to multiorgan damage if left untreated A true medical emergency 2 forms described Exertional Non-exertional/Classical

16 Exertional Heat Stroke
Occurs in young, healthy individuals engaged in heavy exercise during periods of high ambient temperature and humidity One series of 58 patients with heat stroke found an acute mortality rate of 21 percent (Ann Intern Med 1998 Aug 1;129(3):173-81)

17 Non-exertional heat stroke
Affects individuals with underlying chronic medical conditions that either impair thermoregulation or prevent removal from a hot environment. Conditions include: Cardiovascular disease Neurologic or psychiatric disorders Obesity Anhidrosis Extremes of age Anticholinergic agents or diuretics

18 Diff Dx - Hi temp with altered mental state
INFECTIOUS Sepsis, Meningitis/Encephalitis, Falciparum malaria DRUG/TOXIN INDUCED Overdose – anticholinergic, sympathomimetic Withdrawal – benzodiazepene, alcohol – delirium tremens Neuroleptic malignant syndrome malignant hyperthermia Serotonin syndrome ENDOCRINE Thyroid storm, Pheochromocytoma CNS Hypothalamic hemorrhage, status epilepticus esp nonconvulsive

19 Neuroleptic Malignant Syndrome
Impaired thermoregulation in hypothalamus due to relative lack of dopamine Caused by antipsychotic meds/neuroleptics Distinguishing features hyperthermia, altered mental status "lead pipe" muscle rigidity,choreoathetosis, tremors autonomic dysfunction- diaphoresis, labile blood pressure, and dysrhythmias Hx of psychotic disorder/neuroleptic medication use Treatment Cooling, hydration, benzodiazepines Bromocriptine, amantadine, dantrolene

20 Malignant Hyperthermia
Rare (autosomal dominant) Genetic instability of sarcoplasmic reticulum causing massive calcium release Onset: 1 to 10 hours after exposure Triggered by inhalational anaesthetic or succinylcholine Distinguishing features History of succinylcholine use Muscular rigidity Treatment Cooling, hydration Dantrolene

21 Serotonin syndrome Excess serotonin and dopamine levels in CNS
Triggered by any med that increases serotonin levels (eg. SSRI’s, demerol, dextromethorphan, lithium etc.) Distinguishing features Appropriate medication history Muscular rigidity Treatment Cooling, Hydration Cyproheptadine

22 Thyroid storm Hypermetabolic state from extreme thyrotoxicosis
Distinguishing features History of thyroid disease Goiter Ophtho clues  lid retraction/lag, exophthalmos, EOM palsy Treatment Cooling, Hydration PTU, iodide solution, propranolol etc.

23 Overdose Anticholinergics, sympathomimetics Distinguishing features
Hx of ingestion Toxidromes Treatment Cooling, hydration Benzodiazepine, Decontamination

24 Diff Dx cont’d The differential for heat stroke contains many potentially life threatening illnesses It all comes down to your ABC Cooling Hemodynamic support

25 Heat Stroke – Complications
CNS Cerebral edema Permanent neuro damage eg. cerebellar deficits, hemiplegia, or dementia is possible after severe cases Renal Myoglobinuric renal failure-rhabdomyolysis Cardiopulmonary Heart failure Pulmonary edema

26 Heat Stroke - Complications
Electrolyte Hypo or Hyperkalemia Hypernatremia Hypocalcemia, hypomagnesemia Hematologic Thrombocytopenia DIC Hepatic Centrilobular necrosis – not permanent However, can be a useful diagnostic adjunct

27 Heat Stroke – Hepatic Damage
“ Hepatic damage is such a consistent feature of heat stroke that its absence should cast doubt on the diagnosis “ From Rosen’s 5th edition p2003

28 Heat Stroke - Diagnostic Criteria
Classic triad Markedly elevated temp ( >40.5 degrees ) CNS dysfunction Anhidrosis Caveats Sweating seen 50% of the time esp. in exertional heat stroke

29 Investigations CBC+diff , blood culture Infection, thrombocytopenia
Electrolytes, ABG Electrolyte derangement, acidosis Chemstrip/Glucose DKA BUN, Cr Renal failure U/A, urine for myoglobin Rhabdomyolysis Hepatic panel Liver damage INR, PTT, Fibrinogen etc DIC CT Head Intracranial event, pre-LP LP Meningitis/encephalitis Thyroid panel Thyrotoxicosis CXR Pulmonary Edema EKG Secondary ischemia

30 Initial management

31 Treatment summary The Basics… The ABC’s…
Resusc room, oxygen, iv, monitors Vitals-including continuous rectal temp monitoring The ABC’s… Airway, Breathing Cooling Evaporative/Immersive +/- adjuncts Circulation Cautious rehydration Pressor support as needed

32 Treatment summary cont’d
More ABCDE’s…. +/- Antibiotics ? Sepsis, meningitis +/- Benzodiazepines ? Withdrawal syndrome +/- Cyproheptadine ? Serotonin syndrome +/- Dantrolene ? Malignant Hyperthermia ? Neuroleptic Malig Syndrome +/- Decontamination ? Ingestion +/- Endocrinopathy tx ? Thyroid storm

33 What about antipyretics?
Acetaminophen and ASA are not indicated in heat stroke These drugs counteract fever caused by an elevated hypothalamic set point In heat stroke, the increased temperature is due to an entirely different mechanism ASA --> may worsen coagulopathy Acetaminophen --> may exacerbate hepatic damage

34 Cooling The key to successful outcome in heat stroke
Prognosis in heat stroke is directly related to how quickly the body can be cooled down Goal is to cool by degrees/min

35 In the ER ….Cooling Methods
Immersion Evaporation

36 Ice Water Immersion Primary cooling mech = conduction
Pt is undressed and placed into a tub of ice water deep enough to cover the trunk and extremities Can achieve cooling rates of 0.13 degrees/min Can decrease core temp to 39 degrees in min

37 Ice Water Bath-Disadvantages
Can’t perform defibrillation or resuscitative procedures while immersed Vasoconstriction  Shunting of blood from the skin  ? Heat exchange Induced shivering  endogenous heat production Uncomfortable

38 Evaporative Cooling Fans positioned beside an undressed pt while warm water is sprayed/sponged on Pt kept continually wet for continued cooling Can achieve cooling rates comparable to immersive techniques

39 Evaporative Cooling-Advantages
Easier patient access No induced peripheral vasoconstriction Less induced shivering More comfortable for the patient

40 Methods of Cooling Review of 17 journal articles.
Br J Sports Med 2005 Aug;39(8):503-7 Review of 17 journal articles. Modalities of reducing body core temperature in patients with exertional heatstroke The most effective method is immersion in iced water The practicalities of this treatment may limit its use

41 Cooling Goal Keep rectal temperature <39.4ºC and skin temperature 30ºC-33ºC. Cooling should be discontinued when rectal temp hits degrees to avoid “overshoot” hypothermia Avoid: antipyretic agents Alcohol sponge baths Alpha-adrenergic agonists

42 Main Predictors of Outcome
Duration and degree of hyperthermia Time to cooling Indicators of organ dysfunction, such as transaminases, LDH and CK

43 Cooling methods cont’d
To counteract shivering… Benzodiazepines Phenothiazines – advocated in the past, however may potentially lower seizure threshold If severe- non-depolarizing paralytic

44 Circulation – Main Issues
Hypotension and dehydration are the main issues for heat stroke patients Usually, more than one cause for hypotension Hypovolemia Increased peripheral vasodilatation

45 Circulation – Complicating factors
Heat stroke patients are at high risk of developing pulmonary edema and renal failure Cooling a patient will redistribute peripheral blood flow back to the core Need careful balance between hydration and preventing fluid overload

46 Circulation-Approach to hypotension
1st line – cooling Will redistribute volume from periphery to core 2nd line – judicious hydration Most sources suggest cc/h Titrate to hemodynamic response, urine output, age and PMHx of patient etc. Invasive monitoring may be indicated for complicated cases

47 Circulation-Approach to hypotension
3rd line – pressors Be cautious with primarily alpha blocking agents (eg. Levophed) Will cause further vasoconstriction and could potentially decrease heat exchange No definitive evidence on which pressor is the “best” to use

48 Heat exhaustion vs Heat stroke
Important to think of heat exhaustion and heat stroke as two ends of a spectrum The point at which heat exhaustion becomes heat stroke --> when thermoregulatory mechanisms fail or are overwhelmed Heat exhaustion can easily progress to heat stroke if not adequately treated Thus early recognition and treatment essential!

49 Heat exhaustion vs. Heat stroke - Differentiation
Vital signs In general, heat exhaustion < 40 deg, heat stroke > 40 deg Remember though that prehospital cooling may have occurred in the heat stroke patient Clinical exam Heat stroke implies significant CNS dysfunction – seizures, coma, very altered mental state Pts with heat exhaustion have less florid CNS dysfunction- eg. mild disorientation, clumsiness

50 Heat exhaustion vs. Heat stroke-Bottom line
If the possibility of heat stroke is entering your mind, initiate immediate tx (ie Airway, Breathing, Cooling, Diff Dx) Hepatic transaminases may be a useful differentiating factor – but you must initiate immediate cooling while you wait for results

51 Take Home Points Altered mental state + hyperthermia = heat stroke until proven otherwise ABC’s = Airway, Breathing, Circulation, Cooling Treat hyperthermia early or patient dies

52 References Rosen’s 5th edition, pages 1997-2009
Tintinalli’s 5th edition, pages Khosla et al, “Heat-Related Illnesses”, Critical Care Clinics, 15(2), Tek et al, “Heat Illness”, Emergency Medicine Clinics of North America, 10(2), Wexler, Randall K, “Evaluation and Treatment of Heat-Related Illnesses”, American Family Physician, 65(11),

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