Background: This study investigates whether long-term treatment with an angiotensin converting enzyme inhibitor (ACEI) impairs the hemodynamic regulation during the early phase of spinal anaesthesia.
Methods: Forty-two patients undergoing minor surgery were studied. Twenty-one patients were long-term treated (ACEI group), while the other patients served as controls (nonACEI group). All patients received a balanced electrolyte solution(6 ml kg−1) 20 min before spinal anaesthesia.
Results: Mean arterial blood pressure decreased 19% in both groups within 20 min after spinal anaesthesia. Heart rate did not change in either group. Plasma renin concentration increased from 7.3 ± 2.1 to 12.8 ± 4 pg ml−1 during spinal anaesthesia in nonACEI patients (P < 0.05), whereas an elevated plasma renin level remained unchanged in the nonACEI group. The angiotensin II concentration increased in both groups during spinal anaesthesia (P < 0.05). The vasopressin concentration did not change during spinal anaesthesia in the ACEI group, but increased from 1.2 ± 0.3 to 2.2 ± 0.5 pg ml−1 in patients with ACEI treatment (P < 0.05). The norepinephrine concentration increased transiently 5 min after spinal anaesthesia in both groups, and returned to baseline levels within 15 min.
Conclusion: Long-term ACEI treatment does not further exaggerate the blood pressure decrease in the early phase of spinal anaesthesia. The increase in vasopressin concentrations in ACEI treated patients seems to be sufficient to compensate for the inhibited renin-angiotensin system. In addition, the transient increase in plasma norepinephrine, which occurs independent of preoperative ACEI treatment, seems to be involved in blood pressure regulation during spinal anaesthesia.