Response of cerebral blood flow to phenylephrine infusion during hypothermic cardiopulmonary bypass: Influence of Pa(CO2) management

A. T. Rogers, D. A. Stump, G. P. Gravlee, D. S. Prough, K. C. Angert, S. L. Wallenhaupt, R. C. Roy, J. Phipps

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79 Scopus citations


Twenty-eight adult patients anesthetized with fentanyl, then subjected to hypothermic cardiopulmonary bypass (CPB), were studied to determine the effect of phenylephrine-induced changes in mean arterial pressure (MAP) on cerebral blood flow (CBF). During CPB patients managed at 28°C with either alpha-stat (temperature-uncorrected Pa(CO2) = 41 ± 4 mmHg) or pH-stat (temperature-uncorrected Pa(CO2) = 54 ± 8 mmHg) Pa(CO2) for blood gas maintenance received phenylephrine to increase MAP ≥ 25% (group A, n = 10; group B, n = 6). To correct for a spontaneous, time-related decline in CBF observed during CPB, two additional groups of patients undergoing CPB were either managed with the alpha-stat or pH-stat approach, but neither group received phenylephrine and MAP remained unchanged in both groups (group C, n = 6; group D, n = 6). For all patients controlled variables (nasopharyngeal temperature, Pa(CO2), pump flow, and hematocrit) remained unchanged between measurements. Phenylephrine data were corrected based on the data from groups C and D for the effect of diminishing CBF over time during CPB. In patients in group A CBF was unchanged as MAP rose from 56 ± 7 to 84 ± 8 mmHg. In patients in group B CBF increased 41% as MAP rose from 53 ± 8 to 77 ± 9 mmHg (P < 0.001). During hypothermic CPB normocarbia maintained via the alpha-stat approach at a temperature-uncorrected Pa(CO2) of ≃40 mmHg preserves cerebral autoregulation; pH-stat management (Pa(CO2) ≃57 mmHg uncorrected for temperature, or 40 mmHg when corrected to 28°C) causes cerebrovascular changes (i.e., impaired autoregulation) similar to those changes produced by hypercarbia in awake, normothermic patients.

Original languageEnglish (US)
Pages (from-to)547-551
Number of pages5
Issue number4
StatePublished - 1988
Externally publishedYes

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine


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