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OBJECTIVE The aim of this study is to investigate the effect of general anesthesia plus thoracic epidural on oxygen consumption of patients during intraoperatively intravenous administration of amino acid.METHODS Thirty patients, ASA physical status I-II, undergoing middle-upper abdominal surgery, were randomized to either general anesthesia plus epidural (GAE group, n=15) or general anesthesia only(GA group, n=15). For all patients, an epidural catheter was inserted at a tharacic level between T8 and T9, and a catheter was inserted into the right internal jugular vein and a catheter into the left radial artery after patients’entry into the operation room(OR). General anesthesia in all patients was induced by 3μg/kg of fentanyl,0.1μg·kg-1·min-1 of remifentanil and propofol with plasma target control infusion(Cp)(Marsh model) of 4μg/ml. Tracheal intubation was facilitated with 0.6 mg/kg of rocuronium, and patients’lungs were ventilated with Auto-control model by Drager Zeus anesthesia workstation, by which the real-time oxygen consumption(VO2) was also monitored and sevoflurane at the fixed end-tidal concentrations was set at 1.2%. Anesthesia was maintained with closed-circuit sevoflurane, intravenous propofol, remifentanil and fentanyl. The Cp of propofol was adjusted to maintain BIS values between 30 and 60, and supplemental doses of rocuronium were applied as needed for complete surgical muscle relaxation. An infusion of compound amino acid 11.4% solution was started at a rate of 4 kj·kg-1·h-1 simultaneously and continued for 2 h or until the end of surgery(if surgery time less than 2 h) in both groups. In the GAE group, total 10ml of 0.375% epidural bupivacaine was administered for loading dose before skin incision, and intermittently supplemental bolus dose of 4 ml of 0.375% bupivacaine was given every hour, whereas the equal volume of epidural saline was given at each corresponding same time points in the GA group. MAP and HR were recorded at 5 min before and 0,5,15,30,45,60,75 min after tracheal intubation,and VO2 and Tcore at 5,15,30,45, 60,75 min after intubation. Arterial blood samples were taken 5 min after intubation and 5 min after extubation for blood glucose (Glu) analysis. The requirement of anesthetics (including propofol, fentanyl, remifentanil and rocuronium) and vasopressor (phenylephrine and ephedrine) were respectively recorded. RESULTS Compared to the basic value of VO2 at 5 min, VO2 at 15,30,45,60,75 min increased slightly in both groups but no significant difference was found (P> 0.05) and no significant difference at all time points was found between these groups (P> 0.05). Tcores in both groups decreased significantly since 30 min (from baseline of 36.67±0.32℃and 36.62±0.24℃to 36.42±0.35℃and 36.39±0.27℃at the time point of 30 min, respectively, P<0.05) and no significant difference existed between the groups (P>0.05). Postoperative Glu significantly increased in both groups (from 5.57±0.75 to 6.50±1.49 mmol/L in GAE group, from 5.86±1.44 to 7.31±1.39 mmol/L in GA group, P< 0.01), however, the growth of Glu (△Glu= Glupostoperative-Glupreoperative) did not differ significantly between groups (P> 0.05). Compared to GA group, requirements of fentanyl (3.98±0.63 vs.6.23±2.03μg/kg, P<0.01) and remifentanil (6.72±5.52 vs.15.87±10.16μg/kg, P<0.01) were significantly reduced and the requirements of phenylephrine (1.75±1.68 vs. 0.41±0.34 mg, P<0.01) and ephedrine (11.60±9.75 vs.4.60±4.93 mg, P< 0.05) significantly increased in GAE group.CONCLUSION In patients receiving intravenous administration of amino acid intraoperatively, the addition of thoracic epidural to general anesthesia significantly reduces the requirements of fentanyl and remifentanil, however, is not able to suppress the oxygen consumption as a result of amino acid administration.
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