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The management of temperature during hypothermic cardiopulmonary bypass: I — Canadian survey

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Abstract

During hypothermic cardiopulmonary. bypass (CPB) patients are cooled, usually to between 30–32° C, and, after myocardial blood flow is restored, they are rewarmed with blood heated in the pump-oxygenator. We audited our local practice by recording tympanic and nasopharyngeal temperatures in 11 patients undergoing hypothermie CPB. We found that, during rewarming, nasopharyngeal and tympanic temperatures commonly exceeded 35° C although temperature measured in the bladder was <37° C. A survey of cardiac surgery centres in Canada suggested that most centres induce hyperthermia in highly perfused tissues during rewarming, sometimes inadvertently. This may be of some importance because it has become widely appreciated by neuroscientists that mild degrees of brain cooling (2–5° C) are capable, of conferring dramatic protection from ischaemic brain injury and, conversely, mild temperature elevation may be markedly deleterious. If control of brain temperature is considered desirable then we would suggest that nasopharyngeal temperature be monitored during rewarming on CPB.

Résumé

Pendant la circulation extracorporelle (CEC) hypothermique, les patients sont ordinairement refroidis à 30°–32°C et, une fois le débit coronarien rétabli, réchauffés avec le sang du circuit de CEC. Nous avons contrôlé notre pratique usuelle en enregistrant les températures tympanique et oropharyngée chez 11 patients opérés pour revascularisation myocardique. Nous avons trouvé que, pendant le réchauffement, les températures nasopharyngée et tympanique dépassaient généralement 38° quoique la température mesurée dans la vessie ait été inférieure à 37° C. Une enquête réalisée sur la chirurgie cardiaque au Canada montre que dans la plupart des centres, l’hyperthermie est induite dans les tissus à perfusion élevée pendant le réchauffement et, cela, parfois par mégarde. Ce facteur a son importance parce qu’il est maintenant reconnu que le refroidissement cérébral, même sïl est minime (2–5° C), peut protéger efficacement du dommage cérébral ischémique et qu’au contraire, une augmentation de la température, même légère, peut être très nuisible. Comme il est désirable que la température cérébrale soit contrôlée, nous suggérons le monitorage de la température nasopharyngée pendant le réchauffement sous CEC.

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Author information

Correspondence to Howard J. Nathan.

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Nathan, H.J., Lavallée, G. The management of temperature during hypothermic cardiopulmonary bypass: I — Canadian survey. Can J Anaesth 42, 669–671 (1995). https://doi.org/10.1007/BF03012662

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Key words

  • temperature: hypothermia, hypothermie
  • surgery: cardiac, cardiopulmonary bypass
  • Complications: neurological