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Autoregulation and the CO2 responsiveness of cerebral blood flow after cardiopulmonary bypass

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Cerebral blood flow (CBF) was measured by133Xe clearance to determine whether there were any residual effects of cardiopulmonary bypass (CPB) on the CBF response to changes in arterial PCO2 or blood pressure in the early (3–8 hr) post-CPB period. During CPB, the nine patients studied were managed according to alpha-stat, temperature uncorrected, pH management. The mean ± SD increase in CBF resulting from an increase in PaCO2 (1.35 ± 0.5 ml · 100 g−1 · min−1 · mmHg−1 PaCO2) was within the normal range, indicating appropriate CBF response to a change in PaCO2. There were no significant differences in CBF, being 25.7 ml · 100 g−1 · min−1 at a mean arterial blood pressure of 70 mmHg and 26.5 ml. 100 g−1 · min−1 at 110 mmHg, demonstrating intact cerebral autoregulation over this pressure range. We conclude that cerebral autoregulation and CO2 responsiveness are preserved in the immediate postoperative period after CPB using alpha-stat pH management.


Le flot sanguin cérébral (CBF) a été mesuré par Xe133 afin de déterminer les effets résiduels de la circulation extracorporelle (CPB) sur les réponses due CBF aux changements de la PCO2 ou de la pression artérielle dans la période précoce en post CPB (3–8 hres). Durant le CPB, les neuf patients étudiés et chez qui le pH ne fut pas corrigé selon la température, l’augmentation moyenne ± SD de la CBF après une augmentation de la PaCO2 (1,35 ± 0,5 ml · 100 gm−1 · min−1 mmHg−1 PaCO2) était à l’intérieur des normes indiquant une réponse appropriée du CBF au changement de la PaCO2. Il n’y avail aucune différence significative dans le CBF, étant 25,7 ml · 100 g−1 · min−1 pour des pressions artérielles moyennes de 70 mmHg et 26,5 ml · 100 g−1min−1 à 110 mmHg, démontrant une autorégulation cérébrale intacte pour cet écart de pression. On conclut que l’autorégulation cérébrale et la réponse au CO2 est préservée dans la période postopératoire immédiate après CPB utilisant la conduite alpha-stat du pH.


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Correspondence to J. M. Murkin.

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McNeill, B.R., Murkin, J.M., Farrar, J.K. et al. Autoregulation and the CO2 responsiveness of cerebral blood flow after cardiopulmonary bypass. Can J Anaesth 37, 313–317 (1990).

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Key words

  • anaesthesia: cardiovascular
  • brain: blood flow, autoregulation
  • surgery: cardiovascular, cardiopulmonary bypass