Effects of propofol vs sevoflurane on arterial oxygenation during one-lung ventilation.

BACKGROUND: The inhibitory effect of anaesthetic agents on hypoxic pulmonary vasoconstriction may depend upon their dose, especially when using a volatile agent. The aim of this randomized open study was to compare the effects of sevoflurane and propofol, as primary anaesthetic agents, on oxygenation during one-lung ventilation (OLV), with their administration being adjusted to maintain bispectral index (BIS) values between 40 and 60. METHODS: Eighty patients scheduled for a lobectomy, receiving an epidural mixture of ropivacaine and sufentanil, were randomly assigned to Group S (maintenance with sevoflurane) or Group P (maintenance with propofol). After placement of a double-lumen tube, the lungs were ventilated at an inspiratory fraction of oxygen of 1.0, a tidal volume of 6 ml kg(-1), and 12 bpm. Arterial blood gas samples were taken as follows: during two-lung ventilation before OLV, and during the first 40 min of OLV. RESULTS: Fifteen patients were excluded (incorrect placement of the tube or BIS outside the desired range). The two groups were comparable in terms of demographic variables, haemodynamic, and BIS levels during the operation. Four patients in each group had a Sp(O2)<90%. Mean of the lowest Pa(O2) was 16.3 (7.5) kPa in Group S and 17.7 (9.3) kPa in Group P (ns). CONCLUSIONS: Sevoflurane and propofol had similar effect on Pa(O2) during OLV when their administration is titrated to maintain BIS between 40 and 60.

Whole body oxygen uptake is not a good indicator of liver allograft function following orthotopic liver transplantation.

Variations of whole body oxygen uptake (VO2) have been studied during orthotopic liver transplantation. Some authors have suggested that the increase in VO2 after revascularization of the graft could be an index of good function of the grafted liver and thus low VO2 an early sign of primary non-function. The purpose of our study was to assess the temporal course of measured respiratory VO2 and to compare the VO2 changes to indicators of hepatic function. We used a metabolic monitor (Deltatrac, Datex Corp. Finland) to measure VO2 in 18 patients during transplantation. Clotting factors II and V at 1, 3, 7, 14 and 21 days post-operatively and peak serum transaminases within the first 3 post-operative days were determined. Variations of VO2 were a decrease during the anhepatic phase and an increase following the reperfusion phase as compared to the VO2 value obtained at the beginning of the procedure. No correlation was found between the increase in VO2 after reperfusion of the graft and either factor II (r = 0.33-0.4), factor V (r = 0.23-0.43) or peak transaminases (r = 0.13). One patient developed a primary non-function of the graft. For this patient VO2 increased far above the pre-anhepatic values. The authors conclude that VO2 is not a reliable sign of graft function.

The failure of venovenous bypass to prevent graft liver postreperfusion syndrome.

We studied 58 patients undergoing orthotopic liver transplantation, aged 42 +/- 10 years (mean +/- SD), and weighing 65 +/- 14 kg. Anesthesia was maintained with fentanyl, midazolam, and vecuronium. Serum bicarbonate, serum potassium, serum ionized calcium and pH did not change significantly throughout the study. Usual hemodynamic parameters were recorded. Hemodynamic tolerance was assessed by a trial of clamping of the inferior vena cava, above and below the liver and the portal vein; patients were allocated to two groups: the group without venovenous bypass (NBP, n = 29) consisted of patients whose MAP did not decrease by more than 30% and/or cardiac output did not decrease by more than 50%; the group with venovenous bypass (BP, n = 29) consisted of patients whose MAP decreased by more than 30% and/or cardiac output decreased by more than 50% or required venovenous bypass for easier surgical dissection. After clamping of the vena cava and the portal vein, the cardiac index (CI) and mean pulmonary arterial pressure (MPAP) decreased significantly, whereas systemic vascular resistances (SVR) increased. After unclamping the inferior vena cava suprahepatically and infrahepatically, no hemodynamic change was observed. After unclamping the portal vein, MAP decreased, despite the increase in the CI, because of an significant decrease in SVR; in addition MPAP increased despite the decrease in pulmonary vascular resistances. The decrease in MAP of more than 30% during at least 1 min occurred in 6 patients (20%) in the NBP group and in 6 patients (20%) in the BP group. We concluded that the occurrence of the syndrome of cardiovascular collapse following liver reperfusion was similar whether venovenous bypass was used or not.

Continuous monitoring of mixed venous oxygen saturation during orthotopic liver transplantation.

Hemodynamic management is an important issue concerning anesthesia for orthotopic liver transplantation (OLT). Mixed venous oxygen saturation (SvO2) is considered a good index of tissue oxygenation, but controversy exists about the usefulness of monitoring this parameter in different types of surgery. Therefore, a prospective study was performed to determine changes in SvO2 during OLT and to study the correlation between SvO2 and hemodynamic measurements. Thirty patients undergoing transplantation for end-stage liver disease were divided into two groups: group 1 (n = 15, aged 42 +/- 11 years [mean +/- SD]) without venovenous bypass (VVB), and group 2 (n = 15, aged 43 +/- 10 years) with VVB. SvO2 was greater than 74% throughout the procedure and remained stable during dissection and the anhepatic phase. There was a significant increase in SvO2 after unclamping the portal vein in group 1, whereas a significant decrease was observed during the first hour following reperfusion in group 2. There was no correlation among SvO2 and oxygen consumption, arterial oxygen saturation, (SaO2), or hemoglobin concentrations. A statistically significant correlation was found between SvO2 and cardiac index in both groups (group 1: r = 0.58, P = 0.01; group 2: r = 0.51, P = 0.01), but the correlation was relatively poor. Continuous monitoring of SvO2 may be useful, but cannot substitute for intermittent determinations of other hemodynamic or oxygenation parameters.