The determination of anaesthetic agent requirement with use of bispectral index in liver transplantation

Background and aim of the study: Liver transplantation has been a method which is preferred for the treatment of end stage liver disease and some acute liver failure patients. It is demonstrated that the anesthetic requirement is inversely proportional to the degree of hepatic dysfunction during the operation. The liver transplantation operation is performed at three stages in the perioperative period: The dissection phase with dysfunctional liver, the anhepatic phase without liver and neohepatic phase with new and intact liver.Bispectral index (BIS) is a processed EEG method which measures the hypnotic effects of anesthetic and sedative agents on brain. With this technique, the anesthetic depth is determined and anesthetic drug titration is possible.We aimed to investigate alterations between the three phases on the requirement of intraoperative isoflurane within the target of 40-50 BIS values on the patients with end stage liver disease who are candidates for liver transplantation in this study.Materials and methods: This study was performed on 50 patients (18-65 years) who underwent liver transplantation after Faculty Ethics Committee approval. The patients were monitorised with ECG, pulse oximetry non-invasive arterial blood pressure and BIS. Anesthesia induction is performed with lidocaine 1-1,5 mg/kg, thiopental 3-7 mg/kg and fentanyl 2 mcg/kg with intravenous route. Cisatracurium 0,2 mg/kg was given for endotracheal intubation. Isoflurane with air/oxygen (FiO2 = 0,5) was used for anesthesia maintenance in the semi-closed system. The isoflurane concentration was set within the range of 40-50 BIS values. Remifentanil 0,15 mcg/kg/min was infused for analgesia and cisatracurium 0,08 mg/kg/hr was infused for muscle relaxation. After the anesthesia induction 20 G arterial catheter was inserted on the left side for invasive blood pressure monitorisation. Three lumen central venous catheter and 8-8,5 F introducer sheath for pulmonary artery monitorisation were inserted in right internal juguler vein. After initial phase (first 15 minutes), the heart rate (HR), mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), body temperature, bispectral index (BIS) values, end-tidal isoflurane concentration (ETiso) and end-tidal carbon dioxide concentration (ETco2) were recorded at 30 minutes intervals in dissection and neohepatic phase, at 15 minutes intervals in anhepatic phase, beyond the last 30 minutes of the operation.Results: There was no difference in heart rate values according to operation phases. There were statistically significant changes of MAP, MPAP, BIS, ETCO2 and body temperature values according to operation phases. However, all of that parameters were in physiological ranges and clinically insignificant. The ETiso values were lowest at the anhepatic phase. The values were 5% and 8,6% statistically significantly lower in the dissection and neohepatic phases, respectively compared to anhepatic phase.Discussion and conclusion: There was lower end-tidal isoflurane concentration requirement for anhepatic phase compared to the other two phases within the range of 40-50 BIS target values during liver transplantation.Key words: liver transplantation, minimum alveolar concentration, bispectral index