hypothermia hyperthermia

1. The Trip to 37°C
Abdalmohsen Ababtain
CCM fellow
Dec 8 2017
Environmental injuries from Critical care prospective

2. Disclosures
• None

6. By the end of this talk
• Accidental hypothermia and Heat stroke
• Classifications
• Thermoregulation
• Approach Diagnosis
• Management

7. Hypothermia
Mild Moderate Severe
35°C - 32°C 32°C - 28°C <28°C

8. Primary Hypothermia
• Heat Production overcome by excessive cold.

9. Secondary

10. Thermoregulation

11. Hypothalamus

12. How will you measure it?
• Special low grade thermometers.
• Esophageal Probe in intubated patient at the distal third of
the esophagus (Heart temp).
• Rectal (15 cm length)
• No oral or IR thermometers
• Changes in rectal and bladder temperatures significantly
lag behind core temperature changes during rewarming.
Danzl D. Accidental hypothermia. In: Wilderness Medicine, 6th ed, Auerbach PS (Ed), Elsevier, Philadelphia 2012. p.115.

13. Swiss staging system

14. • Fixed dilated Pupils
• Loss of brainstem reflexes
• Stiff.
• Cardiac arrhythmias
• Respiratory arrest
Can mimic Death

15. Predisposing factors
• Hypoglycemia.
• Malnutrition.
• ETOH.
• Addison’s.
• Infection.
• Myxedema Coma.

16. Hypothermia effects
• Bradycardia refractory to Atropine
• A.Fib <32°C
• Asystole and VF <25°C
Cardiac
• EEG silence @ 20°C
• Loss of autoregulation < 25°C
CNS
• Cold diuresis then decrease renal flow.
Renal

17. • Hemoconcentration
• Coagulopathy
Hematological
• Muscular rigidity
MSK
• Hypoglycemia
• Hypokalemia
Metabolic

18. Hypothermia effect on brain
• Hypothermia increases ischemic brain tolerance, as it
slows metabolic processes and reduces oxygen
consumption.
• At a core temperature of 20°C cardiac arrest is tolerated
for up to 30 minutes without clinically significant
neurologic or neuropsychological deficits.
Acta Neurochir Suppl (Wien) 1964;13:11-22.
Contin Ed Anaesth Crit Care Pain 10: 138, 2010.

19. Hypothermia effects on labs
• Blood gases are affected with temperature, as gas
tensions and hydrogen ion concentration decline as
temperature drops.
• Still use the 37C non-adjusted parameters.
Respir Care Clin N Am. 1995;1(1):69.
Clin Chest Med. 1989;10(2):227.

20. Management
• Same indications for intubation
• Humidified warm air 42-46°C
Airway
• Pulse oximeter unreliable
Breathing
• IVF through 2 large bores 40-42°C
• Femoral central line (Sensitive heart)
• Avoid Ringers (Nonfunctioning liver)
Circulation

21. Special considerations
• Hypervolemia
• Irritable myocardium
• Temperature gradient between the core and periphery
• Check pulse with doppler.
• Check heart activity by echo

22. Rescue collapse
• Cardiac arrest that can occur during extrication, transport,
or treatment of a deeply hypothermic patient.
• Hypovolemia!
• Cardiac arrhythmias triggered by moving patient.

23. After-drop
• Further decline in an individual’s core temperature after
removal from cold
• Redistribution of body heat to improperly warmed
peripheral tissues, and the rapid shunt of cold blood from
the periphery to the core as the direct result of
vasodilatation.
• Countercurrent cooling of the blood, which is perfusing
cold tissues, results in a temperature decline until the
gradient is eliminated.
Emerg Med J 2006;23:e56

24. Best Pressor
• No Human studies found
• Dopamine and Dobutamine were safe on animal studies
J Trauma. 1992;33(5):671

25. Medications and pressors
Resuscitation (2008) 78, 21—29

26. • Arrhythmias.
• Unresponsiveness to medications!
Circulation. 2010 Nov 2;122
Resuscitation. 2006 Jun;69(3):509-16. Epub 2006 Apr 4

27. When to stop resuscitating?

28. Prognostic factors
• Unwitnessed cardiac arrest
• Underlying medical illness
• Cold exposure duration
• Initial core temperature
• Arterial Po2
• Potassium Level
• Ammonia Level
• Asphyxia sings
• Avalanche burial time >35 min
J Trauma. 1987 Oct;27(10):1107-12
JAMA. 1990;264:1842-1845
Resuscitation. 2015;93:118. Epub 2015 Jun 19.

29. When to stop resuscitating?

31. Till they are Warm and dead, Except!
• Arrest before cooling
• Hypothermia >32
• Potassium> 12 mmol/l
• Rigid chest or blocked nose and mouth with ice.
Circulation. 2005;112(24 Suppl):IV1.
Resuscitation 1996;31:11–6.

32. Hyperkalemia
APrognostic Factor During Acute Severe Hypothermia
JAMA. 1990;264:1842-1845

33. JAMA. 1990;264:1842-1845

34. Ann Thorac Surg 2017;103:920–5

36. Asphyxia

37. Look for Associations
• Drowning
• Trauma
• Intoxication

38. Trauma and hypothermia
Crit Care Med. 2005 Jun;33(6):1296-301.

39. Trauma and hypothermia
• Hypothermia was independently associated with threefold
increased odds of death odds ratio 3.03
Crit Care Med. 2005 Jun;33(6):1296-301.

40. Ethanol
• Ethanol is the most common cause of excessive heat loss
in urban settings.
• Paradoxical undressing (Lack of adaptive behavior)
• Slow metabolization in hypothermic patient

41. Rewarming
Passive Active
Stage I & II Stage ≥

42. Passive
• Remove wet clothes
• Wrap in warm blankets or insulating material
• Warm environment
• 0.5 and 2.0° C/ hr.

43. Active rewarming
• Cardiovascular instability
• Moderate or severe hypothermia (≤32.2° C)
• Inadequate rate of rewarming or failure to rewarm
• Endocrinologic insufficiency
• Traumatic or toxicologic peripheral vasodilation
• Secondary hypothermia impairing thermoregulation
• DKA for the insulin to work.

44. Active External
• Heating pads
• Radiant sources.
• Bair hugger
• Warm humidified air
• Thermal injury to vasoconstricted hypoperfused skin is a
common hazard with local heat application!
• Arteriovenous anastomosis (immersion in 44 to 45°C
water).

45. Active core rewarming
• Heated humidified oxygen 42-45°C (1 and 2.5°C/hr)
• Peritoneal dialysis.
• Heated Irrigation
• Gastric/colonic! Thoracic
• Mediastinal and cardiac lavage
• Endovascular rewarming.

46. Active core rewarming
• Extracorporeal Blood Rewarming.
• Venovenous rewarming.
• Hemodialysis
• Continuous arteriovenous rewarming
• Cardiopulmonary bypass

48. Failure of rewarming
• Adrenal insufficiency.
• Thyroid insufficiency.
• Sepsis.

49. Endovascular rewarming
Am J Emerg Med. 2017 Nov;35(11):1624-1629.

50. ECMO ?

52. ECC Vs. ECMO
J Thorac Cardiovasc Surg 2007;134:594-600
34.0% vs 75.0%, P .02

53. When to start CPR?

54. When to Start ECMO/CBP?
≈50% Survival

55. Patients with vitals but unconscious

56. Heat Stroke

59. Heatstroke
• Core body temperature > 40ºC (104ºF) with associated
CNS dysfunction in the setting of a large environmental
heat load that cannot be dissipated.

60. Heat Dissipation

62. Classifications
Classical Exertional
Elderly and non-
acclimatized
individuals
Young

64. People at high risk
• Extremes of age
• Dehydration
• Obesity
• Poor physical condition
• Lack of acclimatization
• Lack of air-conditioning
• Social isolation.
• Comorbidities
• Patients already on medications

66. Pathophysiology
• Direct cytotoxicity of heat and release of cytokines
• Endothelial injury
• Coagulation responses of the host

67. Heat effects on your body
Metabolic
Increase in
oxygen
consumption and
metabolic rate
Uncoupled
oxidative
phosphorylation
Cardiac
Sinus tachycardia
and volume
depletion!
Arrhythmias
Respiratory Tachypnea
Non-cardiogenic
pulmonary edema

68. MSK Rhabdomyolysis
Hematology DIC
Liver Acute liver injury
CNS Cerebellar
signs
Irritability Confusion

70. Incidence and Mortality
• United States, the incidence of heat stroke varied from
17.6 to 26.5 cases per 100,000 population.
• In Saudi Arabia, the incidence varies seasonally, from 22
to 250 cases per 100,000 population
• Mortality 21-63%
Ann Intern Med. 1998;129(3):173.
Arch Intern Med. 2007;167(20):2177.
Crit Care Med. 2006;34(4):1087.
JAMA. 1982 Jun 25;247(24):3327-31.
Ann Saudi Med 1987;7:323-6.

71. Diagnosis
• High core temperature
• CNS dysfunction
• Exposure to severe environmental heat
N Engl J Med. 2002;346(25):1978.

72. Physical exam
• Tachycardia
• Tachypnea
• A widened pulse pressure
• Hypotension
• Flushing
• Altered mental status
• Moist or dry skin

73. Max temperature!
• Observations in selected groups, including marathon
runners, normal volunteers, and patients with cancer who
are treated with whole-body hyperthermia, suggest that
the critical thermal maximum in humans is a body
temperature of 41.6°C to 42°C for 45 minutes to 8 hours.
Am J Physiol. 1978 Nov;235(5):R228-36.

74. Brain morbidity and mortality

75. Factors affecting mortality
• High Core Temperature.
• Time to initiate cooling.
• Number of organ dysfunction.
Intensive Care Med. 2009;35(8):1454

76. Management
• Airway protection
• Immediate cooling and support of organ-system
• Volume repletion! CVP and Right heart failure
• Continuous temperature monitoring

77. Are they volume depleted?
34 patient
22
Normal CVP
12
< 0 CVP
6
>10cmH2O
Resuscitation. 1991 Feb;21(1):33-9.

78. Volume resuscitation
• 4C IVF
• Insufficient alone

79. Classic heat stroke
• Evaporation and convective cooling

80. Methods of cooling

81. Makkah Cooling unit

82. Korey Stringer Institute: ksi.uconn.edu

83. Evaporation

84. Evaporation cooling downsides
• Shivering
• Difficulty sticking cardiac leads

85. Exertional heatstroke
• Conduction (immersion in iced water) was effective
among young people, military personnel, and athletes
• Ice water cooling has been shown to be twice as rapid to
reduce core temperature as spraying water over the body
to enhance evaporative cooling
Crit Care. 2007;11(3):R54.
Am J Emerg Med. 1996 Jul;14(4):355-8.
Medicine (Baltimore) 1982, 61:189-197.

86. Conduction
Crit Care. 2007;11(3):R54.

88. Chemical!
Crit Care. 2007;11(3):R54.

89. Antipyretics?
J Appl Physiol. 1962; 17:323–325.
Sports Med. 1985;2:1–7.
Wilderness Environ Med. 2014 Dec;

90. Stop cooling at 38-39ºC
• To avoid iatrogenic hypothermia
Emerg Med Clin North Am. 1992;10(2):299.