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Accidental Hypothermia

Accidental Hypothermia. Cass Djurfors May 8, 2003. Case. Three avalanche workers caught in an avalanche One partially buried called on radio repeater immediately to mobilize rescue team and local paramedics by helicopter

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Accidental Hypothermia

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  1. Accidental Hypothermia Cass Djurfors May 8, 2003

  2. Case • Three avalanche workers caught in an avalanche • One partially buried called on radio repeater immediately to mobilize rescue team and local paramedics by helicopter • Plan to fly direct to local ED (Scene beyond range of STARS without refuel and nearby fuel cache buried in winter snow) • Other two completely buried

  3. Case • Partially buried victim pulls shovel from rucksack on back and digs self out, performs transceiver search to locate first buried who comes up breathing • Continues search and digs up second buried who is VSA and so begins CPR • Burial time 40 minutes.

  4. Case • Paramedics land and apply monitor pads to show sinus bradycardia, confirm VSA, continue CPR • Endotracheal intubation, bundle and fly to nearby regional ED • Sinus bradycardia deteriorates en route to ventricular fibrillation • Pilot does not allow defibrillation in flight

  5. Case • Local ED prepared with 2 EP’s, 1 anaesthetist, 1 GP surgeon, 7 nurses, various support personnel • Patient arrives asystolic • Initial esophageal temp probe 27.5oC

  6. Case • Management as follows: • Confirm ETT placement • Humidified O2 • 1L NS at 41C by Level One Infuser • Switch Level One Infuser to 3l NS irrigation bags for pleural lavage via 36F tube left 2nd intercostal space and second  tube 5th intercostal space • Peritoneal lavage • Bladder irrigation • Alternating all three active internal rewarming modalities between two Infuser chambers allowing dwell time for all 3 modes • Maximum outflow temp from Infuser approx 41C

  7. Case • Meanwhile… • Team leader calls Trauma Centre intensivist re: transfer for CPB • Intensivist unclear as to whether CPB warranted in this case and states “will call back” • Aggressive rewarming continues to produce a rise to 28.5C after 30 minutes • Intensivist calls back to recommend rapid transport for CP bypass • Patient transported by ground (now dark outside) to nearest Trauma Centre

  8. Case • CPB initiated • Patient rapidly warms with return of spontaneous circulation • Proceeds to develop MODS that results in death shortly after

  9. Issues from Case • Resuscitation of hypothermic patient: • CPR • ACLS • Defibrillation • Medications • Core temperature measurement • Rewarming methods, rates, logistics and their indications • Prognostic markers of death in hypothermia

  10. Definitions • Temperature < 35 C • Mild 32-35 C • Moderate 28-32 C • Severe < 28 C • Primary (cold exposure) • Secondary (disease process, eg. Myxedema) • Acute (rural, outdoor hypothermia) • Chronic (urban, indoor, elderly hypothermia) • Immersion vs. non-immersion (degree of rapidity)

  11. Epidemiology • 723 deaths per year US 1979-1995 • 50% older than 65 • Male:female 3:1 • Socioeconomic factors • Mentally ill 5 times greater risk

  12. Mechanism Approximate % of Heat Loss Radiation 50 Convection 30 Evaporation 15 Conduction 5 Mechanisms of Heat Loss

  13. Physiology: Mild • 37.6 normal rectal temperature • 37.0 normal oral temperature • 36.0 ↑ metabolic rate, bp, and muscle tone • 35.0 maximum shivering • 34.0 amnesia, poor judgment • 33.3 Ataxia, apathy; cold diuresis Danzl DF. Accidental hypothermia. Wilderness Medicine

  14. Physiology: Moderate • 32.0 stupor • 31.0 shivering stops • 30.0 poikilothermia; arrhythmias develop • 29.0 ↓ LOC, HR and RR; dilated pupils Danzl DF. Accidental hypothermia. Wilderness Medicine

  15. Physiology: Severe • 28.0 ↓ VF threshold; hypoventilation • 26.0 no response to pain • 25.0 cerebral autoregulation fails, spontaneous VF and asystole • 24.0 hypotension and bradycardia • 23.0 areflexic (incl. corneal and doll’s eye) • 22.0 max VF risk Danzl DF. Accidental hypothermia. Wilderness Medicine

  16. Physiology: Profound • 20.0 lowest resumption of cardiac activity • 19.0 EEG silent • 13.7 lowest adult accidental hypothermia survivor Gilbert et al. Resuscitation from accidental hypothermia of 13.7oC with circulatory arrest. Lancet 355: 375, 2000. • 9.0 lowest therapeutic hypothermia survivor Niazi et al. Profound hypothermia in Man: Report of a case. Annals of surgery. 147(2): 26466, 1958. Danzl DF. Accidental hypothermia. Wilderness Medicine

  17. Decreased Heat Production Neuromuscular inefficiency Impaired shivering Age Immobility / inactivity Endocrine failure Hypopit Hypothyroid Adrenal insuff Nutritional Hypoglycemia Anorexia Malnutrition Increased Heat Loss Exposure / Immersion Dermatologic Erythroderma Burns / TENS Psoriasis) Vasodilation ETOH Toxins Iatrogenic Emergent deliveries Cold infusion Hanania, NA et al. Accidental Hypothermia. Critical Care Clinics. 15(2): 236-49, 1999 Causes of Hypothermia

  18. Impaired Thermoregulation Drugs Sedatives Barbiturates EtOH TCA Peripheral neuropathy SCI DM CNS bleed / trauma Parkinson's Anorexia nervosa Miscellaneous Sepsis Pancreatitis Carcinomatosis Uremia Vascular insufficiency Hanania, NA et al. Accidental Hypothermia. Critical Care Clinics. 15(2): 236-49, 1999 Causes of Hypothermia

  19. Diagnosis • High index of suspicion • Low reading thermometer

  20. Temperature measurement • Need an accurate approximation of core temperature • Traditionally rectal (at least 10-15cm) • Rectal temperature lags behind core: especially during rapid change, cooling to warming transition (Terndrup TE. An appraisal of temperature assessment by infrared emission detection tympanic thermometry. Ann Emerg Med 21:1483-1492, 1992)

  21. Temperature measurement • Direct tympanic thermometry is research standard, but not convenient for ER use • Indirect infrared tympanic thermometry: • often doesn’t read below 34oC • Susceptible to cerumen or water in the canal

  22. Temperature measurement • Esophageal • Falsely elevated with heated inhalation • Bladder • Falsely elevated with peritoneal lavage • Falsely low with cold diuresis • Oral • Found to be comparable to tympanic probe in “hypothermic” trauma patients 35.2-35.6 Kober A et al. Effectiveness of resistive heating compared with passive warming in treating hypothermia associated with minor trauma: a randomized trial. Mayo Clin Proc;. 76:369-75, 2001.

  23. Diagnosis: Lab • ABG’s: • Controversy of historical interest only • Curve shifts left with colder temps causing pH to be reported lower and O2, CO2 to be reported as higher than actual • Blood gas analyzer runs samples at 37oC • Current consensus is that use of uncorrected values provides better outcomes Corneli HM. Environmental Emergencies. Clinical Pediatric Emergency Medicine. 2(3):179-91, 2001.

  24. Lab • Coags may be reported as normal if run at 37oC despite obvious clinical coagulopathy • Electrolyte abnormalities are common and should be addressed • Hypoglycemia should be treated

  25. ECG

  26. The J or Osborne Wave • Deflection of the J point: the junction of the QRS complex and ST segment • Most common in leads II and V6 • Diagnostic but not prognostic • Not pathognomonic: can also occur in CNS lesions, focal cardiac ischemia and sepsis • Magnitude of J wave inversely correlates with temperature Susi U et al. A prospective evaluation of the electrocardiographic manifestations of hypothermia. Academic Emergency Medicine: 6(11); 1121-26, 1999.

  27. Other ECG findingsMattu A et al. Electrocardiographic Manifestations of Hypothermia. American Journal of Emergency Medicine. 20(4); 314-26 • Artifact produced by clinically invisible preshivering muscle tone may obscure P waves • Any arrhythmia (atrial or ventricular) is possible • Bradycardia, Afib, VF asystole common • Treatment of Afib with anticoagulants has not been studied and should not be undertaken • ECG changes resembling ischemia can occur and should only be treated with rewarming

  28. Basic Management: ABC’s • A/B: • Supplemental O2, consider ETT • Neuromuscular blocks ineffective < 30 C • May have to use nasotracheal approach if rigid • Unlikely to induce arrhythmias with ETT • C: • Continuous monitoring; usually volume depleted • Peripheral lines ideal; Central may precipitate dysrythmias • Avoid PA catheters under 32 C • Bolus in 250-500 cc increments with glucose checks and 5% dextrose if necessary • Theoretically avoid ringers lactate due to impaired liver • <32 C all fluids warmed to 40 to 42 C

  29. Basic Management: ABC’s • Remove wet clothing • Avoid rough movement as this may precipitate VF • Nasogastric tube to relieve distension • Foley for monitoring

  30. ACLS in Hypothermia2000 AHA Guidelines • For absent pulse or respirations • Start CPR • Defibrillate VF/Pulseless VT with MAXIMUM of 3 shocks 200, 300, 360 • Secure airway, ventilate with warm humidified oxygen, start IV with warmed NS

  31. ACLS in Hypothermia2000 AHA Guidelines • For core temperature>30oC • CPR • IV meds as per ACLS but with extended dosing intervals • Repeats defibrillation attempts as temp rises

  32. ACLS in Hypothermia2000 AHA Guidelines • For core temperature<30oC • CPR • Withhold IV meds • No further shocks • Proceed with active rewarming

  33. CPR • Can be difficult due to chest wall inelasticity • Optimal rate unknown • Tissue decomposition, rigor mortis, fixed and dilated pupils are NOT indications to withhold CPR

  34. Defibrillation • Hypothermia is known to alter ion channel function and hence alter defibrillation efficacy • Several case reports suggest hypothermia impairs defibrillation leading to traditional belief that defibrillation is largely ineffective below 28oC

  35. Defibrillation • Case reports of hypothermic VF responsive to defibrillation do exist: • Thomas et al. Successful defibrillation in profound hypothermia. Resuscitation. 47(3): 317-20, 2000. • Successful defibrillation of hypothermic patient with core body temperature of 25.6oC • Cortes et al. Severe accidental hypothermia: rewarming by total cardiopulmonary bypass. Revista Espanola de Anestesiologia y Reanimacion. 41(2):109-12, 1994. • 20-year-old male with profound hypothermia (26oC presented in deep coma with recurring ventricular fibrillation that yielded to electrical defibrillation once a core temperature of 27.4oC was reached

  36. DefibrillationUjhelyi et al. Defibrillation energy requirements and electrical heterogeneity during total body hypothermia. Critical Care Medicine: 29(5), 2001. • Animal study • Compared normothermia with hypothermia of 30oC • Induced brief VF • No change in defibrillation energy requirements in hypothermia • Fibrillatory threshold noted to be reduced

  37. Defibrillation • Bottom Line: • Attempt a maximum of three shocks at standard energy settings (200J, 300J, 360J) in the hypothermic VF or pulseless VT patient with core body temperature below 30oC

  38. Pacing?Dixon et al. Transcutaneous pacing in a hypothermic dog model. Annals of Emergency Medicine. 29(5): 602-6, 1997. • 20 mongrel dogs core temperature of 27oC • TCP restored and maintained hemodynamic stability and allowed the hypothermic animals to rewarm in half the time required by their nonpaced counterparts • No human studies

  39. Medications in Hypothermic Arrest • Generally reported to be ineffective and possibly even harmful Corneli HM. Environmental Emergencies. Clinical Pediatric Emergency Medicine. 2(3):179-91, 2001. • Bretylium, lidocaine, vasopressors all studied with no consensus • Kornberger et al. Effects of epinephrine in a pig model of hypothermic cardiac arrest and closed-chest cardiopulmonary resuscitation combined with active rewarming. Resuscitation. 50(3):301-8, 2001. • Epinephrine did not improve time to spontaneous perfusion, and even worsened mixed venous hypercarbic acidosis.

  40. Medications in Hypothermic Arrest • Bottom line: • Avoid in core temp <30oC

  41. Rewarming Methods: Issues • Severe hypothermia is uncommon • No RCT’s exist in accidental hypothermia • Evidence is primarily from case reports • Rapid rewarming, while intuitive, has never been proven to improve outcomes • Human experimental model unethical below 35oC • Risky to blindly generalize results of animal studies to humans

  42. Rewarming Methods: Issues • Rigid treatment protocols are inherently hazardous • Clinical circumstances and availability of resources have to be taken into account

  43. Core Temperature Afterdrop • The continued decline in a hypothermic patient’s temperature after removal from the cold • Cause is temperature equilibration between the warmer core and cooler periphery and countercurrent cooling of blood perfusing the cold extremities • Ideally, rewarming strategies would avoid significant afterdrop

  44. Rewarming Methods • Passive external rewarming • Active rewarming • Active external rewarming • Active core rewarming

  45. Passive External Rewarming • Involves covering patient with insulating material to prevent further heat loss • Indicated mainly for mild hypothermia or as an adjunct in moderate to severe hypothermia • Patient must have endogenous thermogenesis • Humans are poikilothermic below 30oC • Shivering stops below 32oC • Rewarming rates in mild hypothermia with PER range from 0.5-2.0oC/hr Hanania et al. Accidental Hypothermia. Critical Care Clinics. 15(2):236-48, 1999

  46. Active Rewarming • Direct transfer of exogenous heat to the patient • Internal or external techniques • Indications: • Poikilothermia (T< 32oC) • Cardiovascular instability • Inadequate rate or failure to rewarm • Endocrine insufficiency • Traumatic or toxicologic peripheral vasodilation • Secondary hypothermia impairing thermoregulation • Neonatal or infant patients

  47. Active External Rewarming • Exogenous heat is delivered directly to the skin • Forced air rewarming • Warming blankets or heating pads • Immersion • Arteriovenous anastomoses rewarming

  48. Forced Air Rewarming • e.g. Bair Hugger • Theoretical concern: vasodilation in extremities could transport cooler blood back to core causing afterdrop and rewarming shock • Advantages: easy to use, readily available, low cost, noninvasive

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