Neither nalbuphine nor atropine possess special antishivering activity.

The special antishivering action of meperidine may be mediated by its kappa or anticholinergic actions. We therefore tested the hypotheses that nalbuphine or atropine decreases the shivering threshold more than the vasoconstriction threshold. Eight volunteers were each evaluated on four separate study days: 1) control (no drug), 2) small-dose nalbuphine (0.2 microg/mL), 3) large-dose nalbuphine (0.4 microg/mL), and 4) atropine (1-mg bolus and 0.5 mg/h). Body temperature was increased until the patient sweated and then decreased until the patient shivered. Nalbuphine produced concentration-dependent decreases (mean +/- SD) in the sweating (-2.5 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.75 +/- 0.25), vasoconstriction (-2.6 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.75 +/- 0.25), and shivering (-2.8 +/- 1.7 degrees C. microg(-1). mL; r(2) = 0.79 +/- 0.23) thresholds. Atropine significantly increased the thresholds for sweating (1.0 degrees C +/- 0.4 degrees C), vasoconstriction (0.9 degrees C +/- 0.3 degrees C), and shivering (0.7 degrees C +/- 0.3 degrees C). Nalbuphine reduced the vasoconstriction and shivering thresholds comparably. This differs markedly from meperidine, which impairs shivering twice as much as vasoconstriction. Atropine increased all thresholds and would thus be expected to facilitate shivering. Our results thus fail to support the theory that activation of kappa-opioid or central anticholinergic receptors contribute to meperidine's special antishivering action.

Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.

OBJECTIVE: Acute normovolaemic haemodilution with subsequent autologous blood transfusion after surgery is widely used to reduce homologous blood requirements during cardiac surgery. The hypothesis tested was whether a low intraoperative haematocrit (Hct) resulting from haemodilution decreases gastric mucosal pH (pHi). DESIGN: Prospective clinical investigation. SETTING: University Hospital of Vienna, Austria. PATIENTS: 16 consecutive patients scheduled for elective cardiac surgery. INTERVENTIONS: The patients were randomly assigned to one of two groups: In 10 patients (group 1), 500 ml of blood was withdrawn and stored after anaesthesia induction. An equal amount of 6% hydroxyethyl starch was simultaneously infused. After discontinuation of cardiopulmonary bypass (CPB), the autologous blood unit was transfused. Six patients (group 2), who were not subjected to haemodilution and autologous blood transfusion served as controls. In all patients, a gastric tonometry probe was inserted. MEASUREMENTS AND RESULTS: Measurements of pHi and Hct were performed before and after acute normovolaemic haemodilution, during pulsatile hypothermic (30-32 degrees C) CPB, after rewarming, and 30 min after autologous blood transfusion in group 1, and at corresponding time intervals in group 2. Repeated measures analysis of variance and the Mann-Whitney U test were used for statistical analysis. Data are presented as means +/- standard error of the mean. Haemodilution in group 1 caused a significant and persistent decrease in Hct (after haemodilution in group 1 34 +/- 1 vs 40 +/- 1% in group 2). In both groups, pHi decreased during rewarming and after termination of CPB. However, in group 1, pHi was better preserved than in group 2 (rewarming: 7.44 +/- 0.02 vs 7.34 +/- 0.04; after CPB: 7.38 +/- 0.03 vs 7.28 +/- 0.02; p < 0.05). CONCLUSIONS: Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.

Effects of dobutamine versus insulin on cardiac performance, myocardial oxygen demand, and total body metabolism after coronary artery bypass grafting.

OBJECTIVE: The purpose was to study whether the hemodynamic benefit of a catabolic catecholamine (dobutamine) induces a certain oxygen cost for the myocardial energy demand and whether this effect would be less pronounced if an anabolic intervention, such as the administration of insulin, was used. DESIGN: A prospective and randomized study. SETTING: A university hospital. PARTICIPANTS: Investigation of two comparable groups of cardiac patients. INTERVENTIONS: The interventions were postoperative infusions of dobutamine, 7 micrograms/kg/min, and of insulin, 1.5 U/kg/h, respectively, over a period of 30 minutes. MEASUREMENTS AND MAIN RESULTS: The effects of the interventions were measured using parameters relating to cardiac work and myocardial oxygen demand. Moreover, parameters relating to total body metabolism were also recorded. In the dobutamine group, cardiac index (CI) and left ventricular stroke work index (LVSWI) increased significantly (p < 0.05) during therapy by 30% and 40%, respectively. Cardiac effort index (CEI) and tension time index (TTI) also increased (p < 0.05) during therapy by 41% and 30%, respectively. However, in the insulin group, CI and LVSWI also increased (p < 0.01 and p < 0.05) during therapy, although to a lesser extent (16% and 14%), but CEI and TTI did not change at all during therapy. Total body CO2 production (VCO2) and O2 consumption (VO2) in the dobutamine group increased (p < 0.05) during therapy by 9% and 11%, respectively, whereas in the insulin group only CO2 production increased (p < 0.05) by 13%. O2 consumption remained unchanged in this group. CONCLUSIONS: It is concluded that dobutamine as well as insulin administration increase cardiac performance. However, in contrast to dobutamine, insulin does not appear to increase myocardial oxygen demand. Therefore, the anabolic insulin administration may represent a more economic pattern of energy-consuming hemodynamic intervention than does the catabolic catecholamine administration.