Résumé
BACKGROUND: Epidural block is known to block sympathetic efferent nerve fiber, resulting in the decrease of catecholamine. We examined the effects of thoracic epidural block on DFT, neuroendocrine responses and hemodynamic changes in dogs. METHODS: Twenty one dogs were divided into three groups. The control group (N = 7) was anesthesized with only alpha-chloralose for general anesthesia, and a high thoracic epidural (T; N = 7) while the thoracolumbar epidural groups (TL; N = 7) were put under general anesthesia with high thoracic or thoracolumbar epidural blocks, respectively. The DFT was determined at 30 mins after surgical manipulation in the control group and at 10 mins after the epidural blocks in the two epidural groups. Four hemodynamic variables, catecholamine, cAMP and lactate were measured at 30 mins after the surgical manipulation (resting period), at 10 mins after epidural blocks and after defibrillation. RESULTS: 1) The DFT levels were significantly higher in the T (6.4 +/- 2.2 J) and TL groups (11.2 +/- 9.3 J) than in the control group (3.2 +/- 1.6 J)(P < 0.05). In the TL group, epinephrine-induced second DFT was lower (3.0 +/- 1.5 J) than the first DFT (11.2 +/- 9.3 J)(P < 0.05). 2) Catecholamine levels and hemodynamic variables including heart rate, mean arterial pressure, and cardiac output significantly decreased in the TL group compared with the control group after epidural block and defibrillation (P < 0.05). The DFT showed a significant correlation with plasma epinephrine levels after the epidural block (r = 0.56, P < 0.05). CONCLUSIONS: Our results show, an increase in transmyocardial DFT by the epidural block which may be caused by a decrease in catecholamine, especially epinephrine.
Sujets)
Animaux , Chiens , Anesthésie générale , Pression artérielle , Débit cardiaque , Chloralose , Épinéphrine , Rythme cardiaque , Hémodynamique , Acide lactique , Neurofibres , Plasma sanguinRésumé
BACKGROUND: High dose fentanyl anesthesia has been recommended for circulatory stability during coronary artery bypass grafting (CABG), but hypertension and tachycardia in response to noxious stimulation have been noted. The purpose of this study was to evaluate the hemodynamic effects of extensive thoracic epidural analgesia (TEA) combined with general anesthesia (GA). METHODS: The hemodynamic effects in CABG were evaluated in 30 patients. They were randomized into two groups ; the GA group receiving high dose fentanyl (50-70 mcg/kg), the TEA group receiving 10 ml bupivacaine 5 mg ml 1 followed by 5 ml every two hours epidurally GA (N2O-O2). The hemodynamic parameters were evaluated before induction of anesthesia, 20 minutes after induction of anesthesia, after sternotomy, and 30 minutes after end of cardiopulmonary bypass. RESULTS: Heart rate and mean arterial pressure were significantly lower after sternotomy in the TEA group compared to the GA group. Significant increase in cardiac index and decrease in central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure were found after induction of anesthesia and sternotomy in the TEA group compared to the GA group. Especially, the pulmonary vascular resistance was significantly lower during all the period in the TEA group compared to the GA group. No differences were observed in stroke volume index, systemic vascular resistance, left ventricular stroke work index between two groups. CONCLUSIONS: The present study suggests a more effective blockade of the stress response during CABG with TEA than with GA. So, we consider that TEA could be used as an adjunctive anesthetic method during CABG.