Blood salvage in cardiac surgery.

The aim of this study was to evaluate blood salvage provided by an intraoperative blood recovery system (IBRS) and a mediastinal drainage blood recovery system (MBRS) during and after cardiac surgery. Sixty-six patients undergoing aortocoronary bypass surgery were randomly assigned to three groups of 22 patients each. In group I, patients received only homologous blood (HB). Group II and group III patients received the blood content of the oxygenator after concentration by an IBRS at the end of the operation. In group III, patients also received their own mediastinal drainage blood, shed for 6 hours after operation, after concentration and washing in a MBRS. The patients were transfused with homologous blood if needed, in order to obtain a hematocrit of 28% at the end of operation, 30% the following day, and a hemoglobin level over 10 g/dL while on the cardiac surgery ward (8 to 10 days). The three groups were comparable with respect to age, body surface, preoperative and postoperative hematocrits, number of grafts, bypass duration, and postoperative mediastinal blood loss. The amount of HB that was transfused during the operation was significantly lower in groups II and III than in group I (P less than 0.0001). After the operation it was significantly lower in group II than in group I (P less than 0.05), and in group III versus group I. Thus, 13.6% of patients in group II and 38% of patients in group III did not require HB transfusion. No infection, renal dysfunction, or coagulation disorders were observed. It is concluded that the use of an IBRS allows a significant saving of HB. However, because it does not avoid all HB requirements, it should be associated with other techniques to avoid blood transfusion such as the MBRS or predonation.

[Changes in myocardial metabolism induced by drugs used during intensive care]. / Modifications du métabolisme myocardique par les médicaments utilisés en réanimation.

More and more patients with coronary heart disease (CAD) are admitted to intensive care units. The drugs used to treat these patients have various effects on the myocardium which must be known in order to avoid worsening the CAD. This review examines the metabolic effects on the myocardium of the most commonly used drugs in intensive care. The physiology of myocardial oxygen supply is first recalled with regard to the coronary circulation, myocardial oxygen extraction and consumption. Digitalis glycosides do not affect the coronary circulation, but the decrease myocardial oxygen consumption in patients with heart failure, mainly by lowering heart rate. Dihydropyridine calcium blockers (nifedipine, nicardipine) increase coronary blood flow, despite a decrease in arterial blood pressure. Their effects on myocardial oxygen consumption are mediated by a sympathetic reflex. Verapamil decreases the heart rate and myocardial inotropism, and is responsible for coronary vasodilation. The result is a decrease in myocardial oxygen consumption. Diltiazem and bepridil have almost similar effects: they decrease myocardial oxygen consumption and increase blood supply to the heart. It has been recently shown that verapamil was the most depressant calcium channel blocking agent, and that it resulted in the most important decrease in myocardial metabolism. Beta-blocking agents decrease myocardial metabolism, except those with an important intrinsic sympathomimetic activity, such as pindolol. Amiodarone can be considered as an alpha and beta blocking drug: its main effect is to counteract the effects of endogenous catecholamines on myocardial metabolism. The sympathomimetic amines (noradrenaline, adrenaline, isoprenaline, dopamine, dobutamine) increase, to different extents, myocardial oxygen consumption. Vasodilators, such as the nitrates or sodium nitroprusside, decrease cardiac filling pressures, and increase myocardial blood flow, thus lowering myocardial oxygen consumption. Phosphodiesterase inhibitors (amrinone, enoximone) have both an inotropic and a vasodilating effect. They decrease cardiac afterload, and increase blood supply to the myocardium; this compensates for the increase in myocardial oxygen consumption due to the increase in myocardial contractility. Because all the drugs used in intensive care have different effects on myocardial metabolism, their reasoned use should avoid an inappropriate increase in oxygen demand.

[Action of ranitidine on changes in gastric pH during the perioperative period in cardiac surgery]. / Action de la ranitidine sur l'évolution du pH-gastrique dans la période péri-opératoire de chirurgie cardiaque.

Any state of stress originates a reduction of gastric pH contributing to the development of digestive lesions. The objective of this prospective work was to evaluate in subjects having undergone a heart surgical procedure, the effect of an anti-H2 agent, ranitidine, on the changes with time of gastric pH during the first 24 hours following induced anaesthesia. Administered discontinuously intravenously, ranitidine was shown to have a clearcut effect on gastric pH, shifting the pH profiles towards higher values. This phenomenon proves to be statistically significant from the 12th hour following the beginning of anesthesia.