Effects of cardiopulmonary bypass on propofol pharmacokinetics and bispectral index during coronary surgery

PURPOSE: Cardiopulmonary bypass is known to alter propofol pharmacokinetics in patients undergoing cardiac surgery. However, few studies have evaluated the impact of these alterations on postoperative pharmacodynamics. This study was designed to test the hypothesis that changes in propofol pharmacokinetics increase hypnotic effects after cardiopulmonary bypass. METHODS: Twenty patients scheduled for on-pump coronary artery bypass graft (group, n=10) or off-pump coronary artery bypass graft (group, n=10) coronary artery bypass grafts were anesthetized with sufentanil and a propofol target controlled infusion (2.0 µg/mL). Depth of hypnosis was monitored using the bispectral index. Blood samples were collected from the induction of anesthesia up to 12 hours after the end of propofol infusion, at predetermined intervals. Plasma propofol concentrations were measured using high-performance liquid chromatography, followed by a non-compartmental propofol pharmacokinetic analysis. Data were analyzed using ANOVA, considering p<0.05 as significant. RESULTS: After cardiopulmonary bypass, despite similar plasma propofol concentrations in both groups, bispectral index values were lower in the on-pump coronary artery bypass graft group. Time to extubation after the end of propofol infusion was greater in the on-pump coronary artery bypass graft group (334 ± 117 vs. 216 ± 85 min, p = 0.04). Patients undergoing cardiopulmonary bypass had shorter biological (1.82 ± 0.5 vs. 3.67 ± 1.15h, p < 0.01) and terminal elimination (6.27 ± 1.29 vs. 10.5h ± 2.18, p < 0.01) half-life values, as well as higher total plasma clearance (28.36 ± 11.40 vs.18.29 ± 7.67 mL/kg/min, p = 0.03), compared to patients in the off-pump coronary artery bypass graft group. CONCLUSION: Aside from the increased sensitivity of the brain to anesthetics after cardiopulmonary bypass, changes in propofol pharmacokinetics may contribute to its central nervous system effects

Grazing Management Flexibility in Pastures Subjected to Rotational Stocking Management: Herbage Production and Chemical Composition of Kikuyu-Grass Swards

Several recent papers published on tropical pastures have pointed out that under rotational stocking management regrowth should be interrupted when canopy light interception is 95% (LI). Further, these studies have revealed a positive and high correlation between LI and sward height, allowing LI management targets to be defined in terms of sward height. However, there are some indications that lower pre-grazing heights relative to those targets would result in similar leaf accumulation without interfering with sward persistence. The objective of this paper was to verify a possible flexibility of such pre-grazing height targets. A replicated experiment was conducted with treatments corresponding to four pre-grazing height targets (25 cm, corresponding to a canopy light interception of 95%; 20; 15 and 10 cm), which were associated with a single severity of grazing equivalent to removal of 50% of initial height, leaving four post-grazing heights (12.5, 10.0, 7.5 and 5 cm, respectively). Preliminary results indicated that there were no differences in rate of herbage accumulation, herbage yield and crude protein, NDF and ADF contents on swards managed with the pre-grazing targets of 15, 20 and 25 cm. Swards managed with the 10 cm pre-grazing target had the highest contents of CP and lowest contents of NDF and ADF, but herbage accumulation was reduced. Overall, the findings indicate that there may be some flexibility in targets of pre-grazing sward height, provided that defoliation severity is moderate and does not interfere with herbage yield and quality. In that context, targets of pre-grazing sward height defined in terms of canopy light interception would correspond to the maximum value of the possible range of values to be used

Ciclo de Seminários como estratégia para incrementar a divulgação e utilização de publicações da Divisão de Ensino de Química da SBQ e a qualidade de Ensino na Educação Básica Pública

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