Effects of Epidural Anesthesia on Catecholamines, Renin Activity, and Vasopressin Changes Induced by Tilt in Elderly Men

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Abstract
Mean arterial pressure, heart rate, plasma catecholamine [CA], renin activity and vasopressin changes induced by a 30.degree. head-up tilt were studied before and during epidural anesthesia with bupivacaine in 8 elderly patients (ages 58-82 yr). The tilt performed before epidural anesthesia did not modify mean arterial pressure, heart rate, plasma Ca, renin activity and vasopressin at 5 and 15 min. During epidural anesthesia, the superior level of analgesia ranged from [thoracic] T4-T10. Epidural anesthesia induced significant (P < 0.05) decreases from control values in mean arterial pressure and plasma norepinephrine [NE] (from 85 .+-. 6 to 67 .+-. 8 mmHg and from 600 .+-. 108 to 307 .+-. 77 pg/ml, respectively, mean .+-. SEM [standard error of mean]) without significant changes in heart rate, plasma epinephrine, renin activity and vasopressin. However, 5 and 15 min after tilt, significant decreases from pretilt values were measured in mean arterial pressure (from 67 .+-. 8 to 57 .+-. 6 and 55 .+-. 6 mmHg, respectively) and in heart rate (from 70 .+-. 8 to 63 .+-. 7 and 62 .+-. 7 beats/min). Simultaneously, an increase in plasma vasopressin (from 14.8 .+-. 5.5 to 36.2 .+-. 10.3 and 40.0 .+-. 10.5 pg/ml) was recorded, whereas plasma NE and epinephrine remained unchanged. Posttilt plasma renin activity values at 5 and 15 min were increased significantly when compared with the preepidural values (2,752 .+-. 1,168, 2,410 .+-. 1,214 and 713 .+-. 190 pg .cntdot. ml-1 .cntdot. h-1, respectively). During epidural anesthesia in elderly patients, the heart rate and the plasma Ca responses to hypotension induced by tilt are impaired, even if the level of analgesia is < T4 and vasopressin and, to a lesser degree, the renin-angiotensin system may play important roles in the regulation of arterial pressure.