critical care conference - severe hypothermia

1. Critical Care Conference -Severe Hypothermia Mark Byrne, MD Dept of Emergency Medicine Boston Medical Center September 10, 2008 My focus is on clinical manifestations and treatment Who here has seen a case of hypothermia?My focus is on clinical manifestations and treatment Who here has seen a case of hypothermia?

2. Definition Degrees of hypothermia Dealing with pretty low temps, all the way down to 90�F is considered mild hypothermia Who here has seen a case of moderate-severe hypothermia? Arbitrary cut-off points that give a general idea, but still lots of clinical overlapDealing with pretty low temps, all the way down to 90�F is considered mild hypothermia Who here has seen a case of moderate-severe hypothermia? Arbitrary cut-off points that give a general idea, but still lots of clinical overlap

3. 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 Catecholamine surge Hyperventilation e.g. cold shower Neuro effects put you at further risk i.e. as an outdoor enthusiast At these temps, may not be the hypothermia directly that kills youCatecholamine surge Hyperventilation e.g. cold shower Neuro effects put you at further risk i.e. as an outdoor enthusiast At these temps, may not be the hypothermia directly that kills you

4. 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) Breakdown of compensatory mechanisms Dilate pupils but still sluggishly reactiveBreakdown of compensatory mechanisms Dilate pupils but still sluggishly reactive

5. Moderate hypothermia Moderate hypothermia (82� - 90� F) Cardiac arrhythmias (87-88�F) Sinus bradycardia Atrial fibrillation (slow)

6. 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 Organ system failure Hypotension � cardiac out put dropsOrgan system failure Hypotension � cardiac out put drops

7. Trivia What temperature goal is used with therapeutic hypothermia? 90-93�F

8. Definition Degrees of hypothermia Therapeutic hypothermic fits into �mild� hypothermia category Maybe to avoid cardiac arrhythmias? Don�t get a flat-line EEG until 66�FTherapeutic hypothermic fits into �mild� hypothermia category Maybe to avoid cardiac arrhythmias? Don�t get a flat-line EEG until 66�F

9. Cardiac arrhythmias EKG changes Prolongation of all intervals Osborn (�J waves�) Slowing of pacemaker cells and cardiac conductionSlowing of pacemaker cells and cardiac conduction

10. NOT pathognomonic, NOT useful clinically or diagnostically EKG curiosityNOT pathognomonic, NOT useful clinically or diagnostically EKG curiosity

11. Cardiac arrhythmias Sinus bradycardia NOT responsive to atropine or pacing Slow atrial fibrillation (i.e. without RVR) Resolve spontaneously with rewarming Decrease in depolarization of pacemaker cells Sinus bradycardia may be physiologic Generally advised against CPR if pulse is present Atrial irritability results in Afib Slowed conduction results in slow AfibDecrease in depolarization of pacemaker cells Sinus bradycardia may be physiologic Generally advised against CPR if pulse is present Atrial irritability results in Afib Slowed conduction results in slow Afib

12. Cardiac arrhythmias Hypothermic myocardium irritable Handle patients gently! Rough movement may precipitate Vfib Femoral central lines preferably

13. 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 Based on 4 animal trials and 2 human case reports Manufacture of Bretyllium discontinued in late 90sBased on 4 animal trials and 2 human case reports Manufacture of Bretyllium discontinued in late 90s

14. 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

15. Trivia What is �paradoxical undressing�? �Profoundly hypothermic victims sometimes rip off their clothes prior to death.�

16. Make note of �Into the Wild� 1996 - 12 people died trying to reach the summit of Mt Everest 2 references to paradoxical undressing Scott Fisher, one of the best climbers in the world, acting as a guide leading climbers to the summit, was found without mittens and with his down suit unzipped and pulled offMake note of �Into the Wild� 1996 - 12 people died trying to reach the summit of Mt Everest 2 references to paradoxical undressing Scott Fisher, one of the best climbers in the world, acting as a guide leading climbers to the summit, was found without mittens and with his down suit unzipped and pulled off

17. Treatment Passive rewarming Active external rewarming Active internal (core) rewarming

18. 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 Afterdrop concept is controversial Another theory is that continued conduction of heat from relatively warmer core to colder peripheral tissues is still occurring Rewarming shock recognized phenomena in rewarming therapeutic hypothermia patientsAfterdrop concept is controversial Another theory is that continued conduction of heat from relatively warmer core to colder peripheral tissues is still occurring Rewarming shock recognized phenomena in rewarming therapeutic hypothermia patients

19. 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 With heat loss to environment, actual rewarming rate more in range of 0.5�C/hr Give food of IV dextrose to provide energy Probably not aggressive enough for even mild hypothermiaWith heat loss to environment, actual rewarming rate more in range of 0.5�C/hr Give food of IV dextrose to provide energy Probably not aggressive enough for even mild hypothermia

20. Active external rewarming Warm blankets Heat lamps Forced warm air (�Bair Hugger�) 1�C/hr Used in mild hypothermia Forced warm air on order of 1-2�C/hrForced warm air on order of 1-2�C/hr

21. 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 Minimal effect on core temp, mostly prevent further heat loss 1L IVF at 42�C in 70kg person increases temp by 0.3�C Minimal effect on core temp, mostly prevent further heat loss 1L IVF at 42�C in 70kg person increases temp by 0.3�C

22. IVF heated via Level One (classically up to 45�C/110�F, but studied as high as 65�C/150�F) Temperature set on Level One reflects temp of circulating fluid, NOT temp delivered to the patient If no Level One, can heat a bag of NS (no Dextrose) in a microwave IVF heated via Level One (classically up to 45�C/110�F, but studied as high as 65�C/150�F) Temperature set on Level One reflects temp of circulating fluid, NOT temp delivered to the patient If no Level One, can heat a bag of NS (no Dextrose) in a microwave

23. 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

24. 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) Who here has done peritoneal lavage? 2 chest tubes, one for instillation (3rd intercostal, midclavicular line), one for drainage (6th intercostal, anterior axillary line) Left CT may rewarm the heart directly Left CT may also irritate myocardium Who here has done peritoneal lavage? 2 chest tubes, one for instillation (3rd intercostal, midclavicular line), one for drainage (6th intercostal, anterior axillary line) Left CT may rewarm the heart directly Left CT may also irritate myocardium

25. Level One operates akin to �pressure bag� (up to 300mm Hg), not on a pump ? Level One provides up to 500mL/min at 35�CLevel One operates akin to �pressure bag� (up to 300mm Hg), not on a pump ? Level One provides up to 500mL/min at 35�C

26. Active core rewarming Most invasive Hemodialysis 2-3�C/hr Cardiopulmonary bypass >9�C/hr Reserved for cardiac arrest Reserved for completely frozen extremities, severe rhabdo with hyperkalemia, or cardiac arrestReserved for completely frozen extremities, severe rhabdo with hyperkalemia, or cardiac arrest

27. New therapies Endovascular warming Catheter advanced into IVC Balloon circulates warmed fluids

31. �No one is dead until they are warm and dead.�

33. Resuscitation Contraindications Pulseless Apneic Fixed, dilated pupils

34. Resuscitation Contraindications Pulseless Apneic Fixed, dilated pupils Chest wall frozen making CPR impossible Nose or mouth blocked with ice

35. Resuscitation Neuroprotection from hypothermia may allow recovery despite prolonged arrest Endpoint of resuscitation is temperature of at least 90�F Due to decreased oxygen requirement May survive prolonged cardiac arrest without neurologic deficits Due to decreased oxygen requirement May survive prolonged cardiac arrest without neurologic deficits

36. 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. Recovery has been documented with temps as low as 61�F (adult), 57�F (child), cardiac arrest for 6.5hrsRecovery has been documented with temps as low as 61�F (adult), 57�F (child), cardiac arrest for 6.5hrs

37. 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

38. Thank You