Contributions to the Correspondence section are welcomed and if considered suitable wili be published as space permits. They should be typewritten double spaced and, except for case reports, should not exceed 1½ pages in length.
can produce heated humidified oxygen, and in the endotracheal tube the physician has a "royal road" to core rewarming. Lloyd also pointed out that the use of intermittent positive-pressure breathing prevents the development of cerebral edema, which would appear to have supervened in Bristow and colleagues' patient in view of his tardy recovery of cerebral function after normothermia had been restored. Ledingham and Mone9 reported 30 patients treated by a combination of external and core rewarming. Normothermia was achieved in 90% of the patients and the overall survival rate was 70%. This difference represented the severity of the condition producing hypothermia. Their treatment regimen was as follows: 1. Heated and moisturized oxygen delivered by intermittent positive-pressure breathing (a) to achieve core heating (b) to re-expand collapsed and edematous alveoli - (c) to prevent cerebral edema 2. Central venous pressure line (a) to deliver heated intravenous fluids to a central vein in order to achieve core heating (b) to measure central venous pressure 3. Arterial line to measure blood gases continuously (a) to correct hypoxemia (Po2 measured at 37 0C, corrected to prevailing body temperature with a Radiometer [Copenhagen] blood gas calculator) (b) to correct acidosis 4. Rapid external heating by means of a heating cradle or heating blanket aiming at an increase of 0.5 to 1 0C per hour 5. Rewarming as fast as is compatible with oxygenation and tissue perfusion. J.M. DAVIDSON, MB, CH B, FRC5 (EDIN)
University of Alberta Hospital Edmonton, Alta.
To the editor: I am surprised that Davidson believes we were able to achieve a conversion from asystole to ventricular fibrillation to junctional tachycardia at a temperature of 280C. Obviously this temperature must have been above the "intractable" fibrillation temperature. The temperature at which the human heart fibrillates during progressive hypothermia is not fixed but probably has a wide range depending on biologic variation and, in some instances, drugs.10'11 Indeed, one case has been reported where a viable cardiac rhythm was maintained at 18 0C.1' Obviously the correction of the acidosis in this patient probably facilitated the conversion of the dysrhythmias. This, however, is not significantly different from
controlling dysrhythmias at normoIt is our practice to rewarm all nonthermia. arrested hypothermic patients as rapidAlthough our patient exhibited some ly as possible using the shell method of early postcardiac arrest encephalopathy circulating hot water blankets if their it was minimal considering his long core temperature is greater than 300C, period of cardiac arrest (possibly 15 and using peritoneal lavage if their minutes) without the benefit of cardio- temperature is 300C or less. The rapulmonary resuscitation. Intermittent tionale is that the chance of producing positive-pressure breathing, and parti- a fatal afterfall in core temperature cularly the hypocarbia produced by its with shell rewarming is greater at temuse, has been suggested in the early peratures of 300C or less. In patients management of postcardiac arrest vic- suffering from cardiorespiratory rrest tims to minimize encephalopathy. It due to hypothermia I now believe that was used in our patient from the time peritoneal lavage represents the most rapid, safe and probably universally of his arrival at the hospital. Although we share Davidson's en- available, at least in hospitals, method thusiasm for rapid rewarming, parti- of core rewarming. cularly by the core method, we do not G. Bius'row, MD 353 Evelin St. think that passive rewarming by relySelkirk, Man. ing on the endogenous heat production of the hypothermic victim is "merely wishful thinking". Laufman1' described References 1. ALEXANDER L: Combined intelligence Objeca severely hypothermic individual, with tives Committee, US Army, item no 24, file 1945'H.. 1-27 probably the lowest recorded tempera- 2. 26, DUGUID SIMPSON RG, STOWER JM: Acciture from accidental hypothermia, who dental hypothermia. Lancet 2: 1213, 1961 3. TOLMAN KG, COHEN A: Accidental hyporecovered at a rate of approximately thermia. Can Med Assoc J 103: 1357, 1970 CV, ANDERSON MN: Ventricular 0.5 to 1.00C per hour merely by being 4. MOURITZEN fibrillation during hypothermia. J Thorac covered by a blanket in a warm room. Cardiovasc Surg 49: 937, 1965 5. MCLEAN D, GRIFFITHS PD, EMSLIE-SMITH D: I have had experience with at least Serum-enzymes in relation to electrocardiographic changes in accidental hypothermia. three other nonarrested, modestly hyLancet 2: 1266, 1968 pothermic patients (recorded tempera- 6. McNICoL MW, SMITH R: Accidental hypothermia. Br Med J 1: 19, 1964 tures of 25 to 300C) where simply cov7. LLOYD ELI: Accidental hypothermia treated by central rewarming through the airway ering them with warm blankets in a Br J Anaesth 45: 41, 1973 warm room and leaving them otherwise 8. LLOYD ELI, FRANKLAND IC: Accidental hypothermia: central rewarming in the field (C). undisturbed resulted in an uneventful Br Med / 4: 717, 1974 9. LEDINGHAM IM. MONE IG: Treatment after recovery. exposure to cold (C). Lancet 1: 534, 1972 DC, ARMOUR IA, GOLDMAN BS, There is no doubt that in most cases 10. etMACGREGOR al: The effects of ether, ethanol, propanol active, rapid rewarming by a core and butanol on tolerance to deep hyperthermia. Dis Chest 50: 523, 1966 method is preferable to the passive apWHITE DC, NOWELL NW: The effect of alproach. We do not agree, however, 11. cohol on the cardiac arrest temperature in rats. Clin Sci 28: 395, 1965 that the heat gain of the body through 12. hypothermic LAUFMAN H: Profound accidental hypotherinspiration of water-saturated gases, as mia. JAMA 147: 1201, 1965 LLOYD ELI, CONLIFFE 0, ORGEL H, et al: suggested by Davidson, is the answer. 13. Accidental hypothermia: an apparatus for Although this method has been used central re-warming as a first aid measure. Scott Med 1 17: 83, 1972 for nearly S years,1317 Pavlin, Hornbein 14. SHANKS CA: Heat gain in the treatment of and Chaney'8 showed that the heat gain accidental hypothermia. Med I Aust 2: 346, 1975 during ventilation with humidified 15. SHANKS CA, MARSH HM: Simple core reheated oxygen, at least in animals, rewarming in accidental hypothermia. A case treated with heated infusion, endotracheal sults in a temperature increase of only intubation and humidification. Br J Anaesth 45: 522, 1973 0.5 to 1.00C per hour. This is not signiSHANKS CA, SARA CA: Temperature monitorficantly different from the spontaneous 16. ing of the humidifier during treatment of hypothermia. Med I Aust 2: 1351, 1972 rewarming in a warm room when a HAYWARD IS, STEINMAN AM: Accidental hyvictim is covered with a warm blanket. 17. pothermia: an experimental study of inhalation rewarming. Aviat Space Environ Med Furthermore, it was found that the 46: 1236, 1975 transfer of heat occurred not across the 18. PAYLIN E, HORNBEIN TF, CHANEY R: Rewarming of hypothermic dogs by the use alveolar capillary membrane but in the of heated nebulized ventilation, in Abstracts more proximal large airways through the of Scientific Papers, 1976 Annual Meeting, American Society of Anaesthesiologists, 1976, bronchial vessels. When using heated p 105 humidified gases to produce core re- 19. HUDSON MC, ROBINSON GIB: Treatment of accidental hypothermia. Med I Aust 1: warming one must remember that, be410, 1973 cause the specific heat of gas is low, it 20. PICKERING BI, BRISTOW GK, CRAIG DB: Case history no. 97 - core rewarming by penis only the water vapour that carries toneal irrigation in accidental hypothermia with cardiac arrest. Anesth Anaig (Cleve) 56: much heat. Hudson and Robinson19 ex574, 1977 plained logically why this form of core 21. GROSSHEIM RL: Hypothermia and frostbite treated with peritoneal dialysis. Alaska Med rewarming has been found to be so 15: 53, 1973 slow. We have described, and not, I 22. LASH RF, BURDETIE IA, OZDIL T: Accidental profound hypothermia and barbiturate inmight add, originally, a method of core toxication. JAMA 201: 123, 1967 rewarming that is equally as accessible 23. PKrrON IF, DOOLITTLE WH: Core rewarming by peritoneal dialysis following induced hypoin all hospitals and that can result in thermia in the dog. I Appi Physiol 33: 800, very rapid and safe core rewarming.2'23 1972
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