Noninvasive assessment of Cardiac Index using impedance cardiography during liver transplantation surgery: a comparison with pulmonary artery thermodilution.

BACKGROUND: Liver transplantation (LT) is a high-risk surgery associated with significant hemodynamic changes requiring advanced hemodynamic monitoring. Pulmonary Artery Catheter (PAC) is still considered as a gold-standard for Cardiac Index (CI) measurement during LT despite association with an increased risk of complications. Noninvasive impedance cardiography (ICG) could be an interesting alternative tool for CI monitoring. The aim of this study was to compare the precision and trending ability of ICG versus PAC methods during LT. METHODS: Patients undergoing LT were prospectively included. CI was measured with PAC and ICG at 4 time points (T1: before surgical incision, T2: during anhepatic phase, T3: after portal reperfusion, T4: during wound closure). Bias and percentage error (PE) between CI measured with PAC and ICG were analyzed with the Bland-Altman method for repeated measurements. Trending ability was studied with 4-quadrant and polar plots and correlation coefficient. RESULTS: We included 43 patients with 156 measures. Mean bias was -0.95 L.min-1.m-2, SD±1.07, limits of agreement -3.73 to 1.83 L.min-1.m-2 and PE 58%. There was a significant increase in bias during LT (P<0.001). Assessment of trending ability displayed a concordance rate of 72% on the 4-quadrant plot and a mean angular bias of -8.4° (SD±28°) and radial limits of agreement ±55° on the polar plot. CONCLUSIONS: CI measurements using ICG exhibited a low precision and a poor trending ability when compared to thermodilution method during LT. Consequently, ICG is not an adequate hemodynamic tool to monitor CI during LT.

Assessment of the external validity of a predictive score for blood transfusion in liver surgery.

BACKGROUND: Perioperative bleeding is a predictor of morbidity following liver resection. The transfusion-related score (TRS), which is derived from five variables (cirrhosis, preoperative haemoglobin level, tumour size, vena cava exposure and associated extraliver surgical procedure), has been proposed to predict the likelihood of transfusion in liver resection. OBJECTIVE: The purpose of this observational study was to evaluate the external validity of the TRS. METHODS: In a retrospective, monocentre, observational cohort study of patients undergoing elective liver resection surgery, data for transfused and non-transfused patients were compared by univariate analysis. The TRS was calculated for each patient. The frequency of transfusion was calculated for each score level. The accuracy of the TRS was evaluated using the area under the receiver operator characteristic curve (AUC). RESULTS: A total of 205 patients submitted to liver resection were included. Of these, 48 (23.4%) patients received a blood transfusion. There was no significant difference between transfused and non-transfused patients in age, American Society of Anesthesiologists (ASA) score or cirrhosis. The AUC for the TRS was 0.68 (95% confidence interval 0.59-0.77). Among TRS items, only vena cava exposure and associated surgical procedures were significantly associated with risk for transfusion. CONCLUSIONS: In the present population, the TRS appeared to serve as a weak predictor of perioperative transfusion. This study confirms that the external validity of the transfusion predictive score should be subject to further investigation before it can be implemented in clinical use.