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),