Sufentanil disposition during cardiopulmonary bypass

In order to investigate the ability of a computer-assisted continuous infusion (CACI) system to maintain constant plasma levels of sufentanil during cardiopulmonary bypass (CPB) using pharmacokinetic data derived from healthy surgical patients to determine the infusion rate, ten patients were anaesthetized with diazepam, enflurane and oxygen until ten minutes prior to the expected time of initiation of CPB. At that point, an infusion of sufentanil, aimed to reach a central compartment concentration of 5 ng.ml-1, was started via CACI. Plasma concentrations of sufentanil, haematocrit, total protein and albumin concentrations, and nasopharyngeal and CPB inflow temperatures were obtained at predetermined intervals before and up to 90 min after the initiation of CPB. Plasma concentrations of sufentanil reached 3.8 +/- 0.4 ng.ml-1 before CPB and approached the 5.0 ng.ml-1 set point (4.7 +/- 0.4 ng.ml-1) over the 90 min of CPB. In conclusion, our results show that it is possible to obtain stable plasma levels of sufentanil on CPB using a pharmacokinetically driven infusion scheme; however, our data suggest that use of such a system may lead to accumulation of drug during CPB.

Effects of preoperative calcium entry blocker therapy on alpha-adrenergic responsiveness in patients undergoing coronary revascularization

Calcium entry blocking drugs (CaEBs) produce vasodilation and, in high doses, modify alpha adrenergic receptor function. Previous laboratory data suggested that CaEBs might alter the response to alpha-adrenergic stimulation. The authors tested the hypothesis that CaEB therapy altered alpha-adrenergic responsiveness in patients chronically treated with CaEBs. Twenty-six consenting patients with coronary artery disease were given a phenylephrine challenge before anesthesia induction and during cardiopulmonary bypass while the aorta was cross-clamped. A log dose response curve was constructed for each patient, and the ED30 (dose producing 30% increase in systemic vascular resistance) was calculated. Nine patients not treated with CaEB served as controls, and 17 patients were treated with nifedipine (n = 7) or diltiazem (n = 10). Mean ED30 was increased approximately three-fold in the CaEB treated groups compared to the control group. However, there was no statistical difference in the ED30 or phenylephrine dose response slopes between CaEB treated and untreated patients. In awake patients, ED30 correlated with nifedipine levels (R = 0.953, P = 0.01). There was a significant (P less than .02) shift in the ED30 from prior to anesthesia to during aortic cross-clamp and cardiopulmonary bypass; ED30 was approximately 50% less and correlated with CaEB level (R = 0.713, P = 0.03). Hemodynamic variables were not different between groups at any interval. Our data suggest that vascular responsiveness to phenylephrine in patients treated with CaEBs is diminished, but similar to that in untreated patients. Vascular responsiveness decreases in awake patients with increasing nifedipine levels.

Regulation of bovine adipose tissue metabolism during lactation. 3. Adaptations of hormone-sensitive and lipoprotein lipases

Activity of lipases in adipose tissue during pregnancy and lactation was investigated in Holstein cows producing 5950 to 10,000 kg milk per 305 d. Activity of cytoplasmic lipoprotein lipase per gram of tissue was 97, 78, 140, 162, 179, and 235% of 30 d prepartum at -15, 15, 30, 60, 180, and 349 d about calving in yr 1. In yr 2, lipoprotein lipase per gram was 100, 259, 838, 791, and 430% of -30 d at -15, 30, 60, 120, and 180 d. Adaptations in activity per milligram cytoplasm protein were similar to those per gram tissue. Hormone-sensitive lipase per milligram protein was 161, 251, 114, 126, and 252% of -30 d when measured at 30, 60, 120, 180, and 240 d postpartum. Activity per gram of tissue responded similarly to the lactation state. Lipoprotein lipase is thus not a large contributor to the peripartum bovine adipose adaptation but is important in reattainment of body composition in mid and late lactation. Hormone-sensitive lipase is also increased during peak and midlactation. The pattern of elevated activity of these oppositely directed lipases reflects the dichotomous forces of milk fat production and body fat recovery acting on adipose tissue of lactating heifers.