Cerebral Blood Flow Does Not Change Following Sodium Nitroprusside Infusion During Hypothermic Cardiopulmonary Bypass

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Abstract
Seline and then again following SNP-induced reduction of MAP. Two groups were studied. In Group I (n = 9), PaCO2 was maintained near 42 mm Hg uncorrected for nasopharyngeal temperature (NPT). In Group II (n = 8), PaCO2 was maintained near 60 mm Hg, uncorrected for NPT. Nasopharyngeal temperature, MAP, pump oxygenator flow, PaO2, and hematocrit were maintained within a narrow range in each patient during both studies. Since the baseline CBF determinations were conducted at the higher MAP in all subjects, we corrected post-SNP CBF data for the spontaneous decline that occurs over time during CPB. In Group I, a reduction in MAP from 76 ± 9 mm Hg (mean ± SD) to 50 ± 6 mm Hg was associated with a reduction in CBF from 17 ± 5 to 13 ± 3 ml-100 g.min-1 (P < 0.01), a decrease that became statistically insignificant once the time correction factor had been applied (16 ± 4 ml.100 g-1.min-1). In Group II, MAP declined from 75 ± 5 mm Hg to 54 ± 5 mm Hg, and CBF declined from 25 ± 10 to 17 ± 7 ml.100 g.min-1 (P < 0.01), but, again, after time correction, the CBF decline was statistically insignificant (22 ± 8 ml.100g-1.min-1). We conclude that SNP infusion is associated with a decrease in CBF during hypothermic nonpulsatile CPB but that the decrease is not significant when corrected for the duration of cardiopulmonary bypass. Received from the Departments of Anesthesia, Neurology, and Surgery (Section on Cardiothoracic Surgery), Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina. Accepted for publication August 25, 1988. Supported in part by Grant No. HL33869-02 from the National Heart Lung and Blood Institute of the NIH. Address correspondence to Dr. Rogers, Department of Anesthesia, Bowman Gray School of Medicine of Wake Forest University, 300 South Hawthorne Road, Winston-Salem, NC 27103. © 1989 International Anesthesia Research Society...