Purpose: To investigate the effects of chronic ACE inhibition on cardiac neural function following induction of general anesthesia in patients with underlying coronary artery disease.
Method: In a prospective case-control study, heart rate variability (HRV) and baroreflex control were compared preoperatively and 30 min after anesthesia induction in patients receiving, or not, ACEI (n=16, control group and n=16, ACEI group). All patients had normal cardiac function and anesthesia consisted of a fixed dose regimen of fentanyl and midazolam. Anesthesia-related hypotension was defined by systolic blood pressure < 90 mmHg. Spectral density of HRV was calculated for low frequency and high frequency bands (LF, from 0.05 to 0.15 Hz and HF, from > 0.15 to 0.6 Hz). Baroreflex sensitivity was estimated after blood pressure changes induced by injections of phenylephrine (PHE) and nitroglycerin (NTG).
Results: The HRV parameters and baroreflex sensitivity were not different between groups, during the awake and anesthesia periods. Anesthesia produced similar reduction in total HRV in the Control and ACEI groups (-93 +/- 28% vs -89 +/- 32%), and in baroreflex sensitivity during NTG (-64 +/- 21% vs -54 +/- 17%) or PHE tests (-74 +/- 25% vs -72 +/- 22%). Anesthesia-related hypotension occurred in nine patients in the ACEI group (vs two controls). Although the hypertensive response to phenylephrine was greater after anesthesia in both groups, the sensitivity to phenylephrine was attenuated in those patients experiencing hypotension in the ACEI group.
Conclusions: Chronic preoperative treatment with ACEIs does not influence cardiac autonomic regulation and anesthetic-induced hypotensive episodes are mainly attributed to decreased alpha-adrenergic vasoconstrictive response.