Changes in maternal middle cerebral artery blood flow velocity associated with general anesthesia in severe preeclampsia

In women with severe preeclampsia, significant increases in mean arterial p ressures (MAP) are common after rapid induction of general anesthesia (GA) and tracheal intubation. The objectives of this prospective study were to a ssess the effects of the rapid induction-intubation technique on middle cer ebral artery (MCA) flow velocity in severe preeclampsia and to examine the correlation between mean MCA flow velocity (Vm) and MAP. Eight women with s evere preeclampsia (study group) and six normotensive women at term (contro l group) scheduled to undergo cesarean section under GA were studied. Befor e induction, patients in the study group received IV labetalol in divided d oses to lower diastolic pressures to <100 mm Hg. Anesthesia was induced wit h pentothal 4-5 mg/kg, followed by succinylcholine 1.5 mg/kg to facilitate tracheal intubation. A transcranial Doppler was used to measure Vm. Both Vm and MAP were recorded before induction and every minute for 6 min after in tubation. In the study group, after the administration of labetalol, MAP de creased from 129 +/- 9 to 113 +/- 9 mm Hg (P < 0.05), and Vm decreased from 59 +/- 11 to 54 +/- 10 cm/s (P < 0.05). After intubation, MAP increased fr om 113 +/- 9 to 134 +/- 5 mm Hg (P < 0.001), and Vm increased from 54 +/- 1 0 to 70 +/- 10 cm/s (P < 0.001). In the control group, while MAP increased significantly from 89 +/- 6 to 96 +/- 4 mm Hg (P < 0.05) after intubation, the concurrent increase in Vm from 49 +/- 5 to 54 +/- 7 cm/s was not signif icant. There was a significant positive pooled correlation between Vm and M AP (r = 0.5, P < 0.0006) in the study group but not in the control group (r = 0.24). After induction and intubation, both Vm and MAP values were signi ficantly increased in the study group patients at all observation points co mpared with the control group patients. The findings indicate that Vm incre ases significantly after rapid-sequence induction of GA and tracheal intuba tion in women with severe preeclampsia, and there seems to be a direct rela tionship between MAP and Vm. Implications: In women with severe preeclampsi a, rapid-sequence induction of general anesthesia and tracheal intubation c an cause severe hypertension. Our results indicate that the increase in blo od pressure is associated with a significant increase in maternal cerebral blood flow velocity and that there is a significant correlation between the se two variables.