Baroreflex control of heart rate during high thoracic epidural anaesthesia

Abstract

SummaryBaroreflex control of heart rate after cardiac sympathectomy induced by thoracic epidural anaesthesia was evaluated in 30 patients who were randomly assigned to group I (bupivacaine 0.25%). group 2 (bupivacaine 0.5%) or group 3 (control). Plasma volume expanders were given to equalise preload conditions. as assessed using transoesophageal echocardiography. All measurements were made under general anaesthesia. Barorejex sensitivity was determined from the heart rate response to phenylephrine and nitroglycerine. There was no difference in cardiac slowing in response to phenylephrine hetween the three groups. Baroreflex sensitivity. measured as cardiac acceleration in response to nitroglycerine, was significantly lower ( p < 0.01) in groups I and 2 (1.8 and 1.5 ms.mmHg-' respectively) compared with group 3 (3.5 ms.mmHg-') with no differences between the two hupivacaine concentrations. The results suggest that barorejex-mediated response to decreases in arteriul pressure is dependent on the integrity of the sympathetic nervous system. Key wordsAnaesthetic techniques regional; epidural. Reflexes; baroreceptor. Heart; cardiovascular reflexes. Sympatheric nervous system; blockade.It has been suggested that cardiac sympathectomy induced by high spinal or epidural anaesthesia may alter arterial baroreceptor reflexes [ 1-31, At present, little information is available about the extent and clinical significance of such alterations. One study by Takeshima and Dohi surprisingly showed that cardiac sympathectomy induced by cervical epidural blockade did not alter heart rate response to decreasing blood pressure, but suppressed cardiac slowing in response to blood pressure increase [4]. It was speculated that sympathetic control of heart rate might function as a vagus inhibitor rather than as an active cardiac accelerator. The authors admitted that cardiopulmonary baroreceptors could have been affected by changes in central blood volume, secondary to peripheral vasodilation or vasoconstruction, and that this might have altered arterial baroreceptor heart rate reflex.The aim of our study was to investigate the effect of high thoracic epidural anaesthesia on baroreflex control of heart rate, in a controlled randomised trial, with an attempt to keep central blood volume equal in the different groups. Secondly, we compared the effect of two different bupivacaine concentrations (0.25% and 0.5%) on the baroreflex control of heart rate. MethodsThirty patients, with an ASA physical status of 1 or 2, scheduled for elective abdominal surgery entered the study. Subjects with any kind of cardiac or circulatory disorder, autonomic neuropathy, contraindications to epidural anaesthesia and contraindications to transoesophageal echocardiography were not studied. The abdominal operations included: duodenum-preserving resection of the pancreatic head (n = 12), cholecystectomy ( n = 6), cholecystojejunostomy ( n = 4), liver tumour resection ( n = 2), Whipple's pancreaticoduodenectomy (n = 2), resection of the sigmoid colon (n = I), cholec...

Endoscopic thoracic sympathectomy attenuates reflex tachycardia during head-up tilt in lightly anesthetized patients with essential plamar hyperhidrosis

“…However, Goertz et al [11] reported that epidural anesthesia producing analgesia above T1 reduced baroreflex sensitivity, as calculated with the depressor test. The major differences between the two studies were that, in the study of Takeshima and Dohi [10], CTEA was performed with lidocaine, with the patient conscious, whereas, in the study of Goertz et al [11], CTEA was induced with bupivacaine during nitrous oxide-fentanyl anesthesia.…”

“…However, Goertz et al [11] reported that epidural anesthesia producing analgesia above T1 reduced baroreflex sensitivity, as calculated with the depressor test. The major differences between the two studies were that, in the study of Takeshima and Dohi [10], CTEA was performed with lidocaine, with the patient conscious, whereas, in the study of Goertz et al [11], CTEA was induced with bupivacaine during nitrous oxide-fentanyl anesthesia. Our present findings are in contrast to those of Takeshima and Dohi [10], but are quite similar to those of Goertz et al [11], although the scope of our study probably encompassed factors other than the depressor response.…”

“…The major differences between the two studies were that, in the study of Takeshima and Dohi [10], CTEA was performed with lidocaine, with the patient conscious, whereas, in the study of Goertz et al [11], CTEA was induced with bupivacaine during nitrous oxide-fentanyl anesthesia. Our present findings are in contrast to those of Takeshima and Dohi [10], but are quite similar to those of Goertz et al [11], although the scope of our study probably encompassed factors other than the depressor response. Therefore, we speculate that consciousness may help to preserve the tachycardic response evoked by acute central hypovolemia after the partial or incomplete denervation of cardiofugal sympathetic fibers.…”

“…Confirmation of the safety of ETS for the treatment of EPH is essential, because EPH is a socially embarrassing, but not life-threatening, disorder. In addition, previous clinical studies have reported contradictory results concerning the effects on baroreflex sensitivity of cardiac sympathectomy induced by cervicothoracic epidural analgesia (CTEA) [9][10][11]. We are particularly interested in the behavioral differences vesulting from the incomplete or partial sympathetic denervation induced by ETS compared with those resulting from CTEA.…”

Epidural Clonidine Suppresses the Baroreceptor-Sympathetic Response Depending on Isoflurane Concentrations in Cats

“…Baroreflex sensitivity has been reported to be suppressed by volatile anesthetics (10), cervicothoracic epidural anesthesia (11), and large doses of IV local anesthetics (12). Therefore, baroreflexes are significantly affected by combined general/epidural anesthesia with cardiac sympathectomy (13,14). Sudden bradycardia and severe hypotension secondary to decreased venous return or surgical bleeding can occur during combined general/thoracic epidural anesthesia because of decreased sympathetic response and increased vagal activation.…”