That’s Hot!Dr. Kelly Kasteel

Case Study-hyperthermia

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.

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 37-39 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

Case Study-History

PMHx1.  Hepatitis C.2.  BAD

Meds– 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

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

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

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

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

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

Case study- Course in Hospital

Treated presumptively as sepsis nyd- piptazo, flagyl Negative workups – no identifiable septic or

obstetrical causes for DIC. July 23-24- 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

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?

Basic principles of Heat

4 mechanisms that allow the body to maintain a constant core temperature– Radiation – Convection – Conduction– Evaporation

Fever vs. Hyperthermia

Fever– 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

Diff Dx - Hi temp with altered mental state

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

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)

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

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

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 useTreatment

– Cooling, hydration, benzodiazepines– Bromocriptine, amantadine, dantrolene

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

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

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.

Overdose

Anticholinergics, sympathomimetics Distinguishing features

– Hx of ingestion– Toxidromes

Treatment– Cooling, hydration– Benzodiazepine, Decontamination

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

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

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

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

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

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

Initial management

Treatment summary

The Basics…– 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

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

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

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 0.1-0.2 degrees/min

In the ER ….Cooling Methods

Immersion

Evaporation

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 10-40 min

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

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

Evaporative Cooling-Advantages

Easier patient access No induced peripheral vasoconstriction Less induced shivering More comfortable for the patient

Methods of Cooling

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

Cooling Goal

Keep rectal temperature <39.4ºC and skin temperature 30ºC-33ºC.

Cooling should be discontinued when rectal temp hits 39-40 degrees

– to avoid “overshoot” hypothermia

Avoid:– antipyretic agents– Alcohol sponge baths – Alpha-adrenergic agonists

Main Predictors of Outcome

Duration and degree of hyperthermia Time to cooling Indicators of organ dysfunction, such as

transaminases, LDH and CK

Cooling methods cont’d

To counteract shivering…– Benzodiazepines– Phenothiazines – advocated in the past, however

may potentially lower seizure threshold– If severe- non-depolarizing paralytic

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

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

Circulation-Approach to hypotension

1st line – cooling– Will redistribute volume from periphery to core

2nd line – judicious hydration– Most sources suggest 250-500 cc/h– Titrate to hemodynamic response, urine output,

age and PMHx of patient etc.– Invasive monitoring may be indicated for

complicated cases

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

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!

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

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

Take Home Points

Altered mental state + hyperthermia = heat stroke until proven otherwise

ABC’s = Airway, Breathing, Circulation, Cooling

Treat hyperthermia early or patient dies

References

Rosen’s 5th edition, pages 1997-2009 Tintinalli’s 5th edition, pages 1235-1242 Khosla et al, “Heat-Related Illnesses”, Critical Care

Clinics, 15(2), 251-263 Tek et al, “Heat Illness”, Emergency Medicine Clinics

of North America, 10(2), 299-309 Wexler, Randall K, “Evaluation and Treatment of

Heat-Related Illnesses”, American Family Physician, 65(11), 2307-2313