Intravenous nicardipine in the treatment of postoperative arterial hypertension

Background: Calcium entry blockers are commonly used in the management of postoperative hypertension. The hemodynamic and blood gas effects of nicardipine, a dihydropyridine derivative available intravenously, were studied in patients after abdominal aortic surgery. Methods: Sixteen patients (66 ± 8 years) who developed arterial hypertension (mean arterial pressure, >90 mmHg) after abdominal aortic aneurysm reconstruction were studied. Fourteen patients had already been treated with a sodium nitroprusside infusion, the doses of which were maintained constant (mean dose: 1.42 ± 1.04 μg/kg/min). Hemodynamic and blood gas data were collected at baseline, 15 minutes, and 45 minutes after a slow bolus administration of 3 to 5 mg of nicardipine. Results: After the nicardipine administration, mean arterial pressure decreased from 101 ± 11 to 83 ± 11 mmHg (p < 0.001), and the cardiac index acutely increased from 3.96 ± 0.74 to 4.57 ± 0.83 L/min/m2 (p < 0.05). Systemic vascular resistance significantly decreased. There were no significant changes in heart rate, stroke volume, cardiac filling pressures, pulmonary artery pressures, pulmonary vascular resistance, left ventricular stroke work, or right ventricular stroke work. One patient developed acute pulmonary edema, associated with a dramatic increase in cardiac filling pressures, and electrocardiographic signs of myocardial ischemia. Nicardipine administration was also associated with an acute reduction in Pao2 from 85.0 ± 12.1 mmHg to 70.3 ± 9.2 mmHg (p < 0.001), associated with an increase in venous admixture from 21.7% ± 3.2% to 28.0% ± 5.2% (p < 0.01). Oxygen delivery increased moderately and oxygen extraction decreased, but oxygen consumption was unchanged. Conclusion: This study confirms the excellent efficacy of nicardipine in the management of postoperative hypertension, but underlines the risk of poor cardiac tolerance in patients after major surgery. Although oxygen delivery to the cells is usually well preserved, nicardipine can also significantly alter blood oxygenation by increasing ventilation/perfusion mismatch.