Critical Care Conference - Severe Hypothermia
Transcript of Critical Care Conference - Severe Hypothermia
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Critical Care Conference -
Severe Hypothermia
Mark Byrne, MDDept of Emergency Medicine
Boston Medical CenterSeptember 10, 2008
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Definition
• Degrees of hypothermia
Mild 90° - 95° F
Moderate 82° - 90° F
Severe <82° F
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Mild hypothermia
• Mild hypothermia (90° - 95° F)– “Excitation” phase
• Shivering (max ~95°F)• Tachypnea (hyper-ventilation)• Tachycardia
– Early CNS depression (92°F)• Ataxia/Dysarthria• Impaired judgement/Apathy
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Moderate hypothermia
• Moderate hypothermia (82° - 90° F)– “Slowing” phase
• Hypo-ventilation• Bradycardia• Loss of shivering (88°F)
– Further CNS depression• Hyporeflexia• Lethargy/Stupor (90°F)• Dilated pupils (86°F)
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Moderate hypothermia
• Moderate hypothermia (82° - 90° F)– Cardiac arrhythmias (87-88°F)
• Sinus bradycardia• Atrial fibrillation (slow)
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Severe hypothermia
• Severe hypothermia (<82° F)– Cardiopulmonary failure
• Hypotension• Pulmonary edema• Apnea• Ventricular fibrillation (82°F)
– Profound CNS depression• Areflexia• Dilated, unreactive pupils (80°F)• Coma
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Trivia
• What temperature goal is used with therapeutic hypothermia?
• 90-93°F
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Definition
• Degrees of hypothermia
Mild 90° - 95° F
Moderate 82° - 90° F
Severe <82° F
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Cardiac arrhythmias
• EKG changes– Prolongation of all intervals– Osborn (“J waves”)
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Cardiac arrhythmias
• Sinus bradycardia– NOT responsive to atropine or pacing
• Slow atrial fibrillation (i.e. without RVR)
• Resolve spontaneously with rewarming
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Cardiac arrhythmias
• Hypothermic myocardium irritable– Handle patients gently!– Rough movement may precipitate Vfib– Femoral central lines preferably
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Cardiac arrhythmias
• Ventricular fibrillation– Lidocaine ineffective in severe hypothermia– Prophylactic Bretyllium (from animal studies)– May be refractory until rewarmed (86-90°F)
• Trial of defibrillation• If unsuccessful, CPR and aggressive rewarming
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Coagulation disorders
• Bleeding diasthesis– Coagulation enzymes non-functional– Manifests as a clinical phenemona
• Lab values may be deceptively “normal”• PT/PTT performed at 98.6° F
– Giving clotting factors ineffective
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Trivia
• What is “paradoxical undressing”?
• “Profoundly hypothermic victims sometimes rip off their clothes prior to death.”
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Treatment
• Passive rewarming
• Active external rewarming
• Active internal (core) rewarming
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Principles of rewarming
• Extremities and trunk should NOT be warmed simultaneously*– Core temp “afterdrop”
• Cold, acidemic blood thaws in extremities• Returns to core causing drop in temp + pH
– “Rewarming shock”• Warming extremities --> peripheral vasodilation• May cause precipitous hypotension
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Passive rewarming
• Supportive care– Remove wet clothing– Cover with blankets– Room temp 75° F
• Body self-corrects– Shivering 1.5°C/hr– Increased metabolic rate
• Reserved for early “excitation” phase
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Active external rewarming
• Warm blankets
• Heat lamps
• Forced warm air (“Bair Hugger”) 1°C/hr
• Used in mild hypothermia
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Active core rewarming
• Non-invasive– Warm, humidified oxygen 41°C 0.5°C/hr– Warmed IV crystalloid 42°C 0.3°C/L
• Only significant with large volumes
– Used in mild hypothermia
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Active core rewarming
• Mildy invasive– Bladder irrigation– Gastric lavage 42°C 1.5°C/hr
• 250mL NS aliquots q10-15min
– Used in mild-moderate hypothermia
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Active core rewarming
• Moderately invasive– Peritoneal irrigation 42°C 1-2°C/hr
• 1-2L NS aliquots q20-30mins
– Pleural irrigation 42°C 3°C/hr• 500mL/min* NS infusions
– Reserved for – CV instability
– Profound CNS dysfunction
– Temp <30°C(86°F)
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Active core rewarming
• Most invasive– Hemodialysis 2-3°C/hr– Cardiopulmonary bypass >9°C/hr
– Reserved for cardiac arrest
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New therapies
• Endovascular warming– Catheter advanced into IVC– Balloon circulates warmed fluids
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“No one is dead until they are warm and dead.”
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Resuscitation
• Contraindications– Pulseless– Apneic– Fixed, dilated pupils
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Resuscitation
• Contraindications– Pulseless– Apneic– Fixed, dilated pupils
– Chest wall frozen making CPR impossible– Nose or mouth blocked with ice
X
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Resuscitation
• Neuroprotection from hypothermia may allow recovery despite prolonged arrest
• Endpoint of resuscitation is temperature of at least 90°F
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Trivia
• What is the lowest temperature from which someone has been successfully resuscitated?
• Recovery has been documented with temps as low as 61°F in an adult and 57°F in a child.
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Summary
• “No one’s dead until they’re warm and dead”
• Sinus brady, Afib resolve with rewarming
• Vfib may be refractory to defib, meds
• Handle severely hypothermic patients gently!
• Bair hugger, warmed O2 + IVF minimal effect
• Cavity lavage for CV or CNS instability
• CPB reserved for cardiac arrest
• Endovascular warming is a new option
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Thank You