The Comparative Effects of Intravenous Nicardipine and Prostaglandin E1 on the Cerebral Pial Arteriolar Constriction Seen After Unclamping of an Aortic Cross-Clamp in Rabbits

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Abstract

BACKGROUND:

The potent vasodilators nicardipine and prostaglandin E1 (PGE1) are useful for the treatment of systemic hypertension or pulmonary hypertension during aortic surgery.

METHODS:

We measured cerebral pial arteriolar diameters, using a rabbit closed cranial window preparation: before (baseline) and 15 min after the start of an IV infusion (preclamp) (0.9% saline [control group], nicardipine [at 0.1, 1.0, or 10 μg·kg−1·min−1], or PGE1 [at 0.1 or 1.0 μg·kg−1·min−1]), just after aortic clamping, 20 min after clamping, and at 0–60 min after unclamping.

RESULTS:

In the control group, a significant decrease in diameter persisted for at least 60 min after unclamping (maximum [at 60 min], −16% for large [≥75 μm], and −27% for small [<75 μm] arterioles versus baseline). Although the aortic unclamping-induced vasoconstriction was unaffected under the smallest dose of nicardipine, it was significantly attenuated under larger doses in both large and small arterioles (residual vasoconstriction, −10% and −6% for large and −18% and −10% for small arterioles; at 60 min). The pial arteriolar constriction observed at 5 min or more after unclamping in the control group was not altered by PGE1 in either large or small arterioles.

CONCLUSIONS:

The larger doses of nicardipine, but neither dose of PGE1, attenuated aortic unclamping-induced sustained cerebral pial arteriolar constriction.

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