Changes in cerebral blood flow (CBF) associated with decreases in mean arterial pressure (MAP) produced by sodium nitroprusside (SNP) infusion were measured by intra-aortic injection of 133Xe in 17 patients during hypothermic cardiopulmonary bypass (CPB). In each patient, CBF was determined as baseline 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·100 g-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.
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine