The non-stimulant cardioselective beta adrenocepter antagonist atenolol has been studied in volunteers in order to define its pharmacokinetic characteristics. Atenolol (100 and 200 mg orally) is rapidly absorbed, reductions in heart rate and systolic pressure being observed in 30 min. The effect persists for up to 8 h. Over 85% of an intravenous dose is excreted in urine within 24 h but only 50% of an oral dose. The bioavailability of approximately 50% is due to reduced absorption. Peak blood levels are observed at 2-4 h and the half life of atenolol given orally is 5-6 h. Atenolol reduces the cardiac response to standing and head-up tilt. It does not reduce circulating levels of renin but slightly impairs the renin response to tilt. Atenolol both orally and intravenously reduces supine diastolic pressure about four hours after administration, the effect persisting for up to 24 h.
Avoidance of increasing afterload is important during anaesthesia for cardiac surgery. We studied the haemodynamic consequence of deliberate vasodilation during sternotomy in nine patients (mean age 57 -+ 12 years, mean left ventricular ejection fraction 0.51 +-0.09) undergoing valvular replacement. Nicergoline, a new ergol derivative, produces vasodilation (alpha blocking effect), bradycardia (central effect) and has no effect on myocardial metabolism) It was given as a continuous infusion, started after induction, at a rate of 0.8 mg. kg-t/hour.This group was compared to a control group of 12 patients (mean age 60 +-13 years; mean left ventricular ejection fraction 0.51 -+ 0.1) undergoing valvular replacement (seven patients) coronary artery bypass graft (four patients) or aneurysmectomy (one patient). Premedication was pentobarbitone sodium 60-120 mg PR., with intramuscular promethazine I mg. kg -I and meperidine 1 rag. kg -I. Anaesthesia was neurolepanalgesia with droperidol 100 mg and fentanyl 2 mg in 500 ml D5W infused during 15 minutes of induction at 5 mg. kg-t/hr and then maintained at 2 mg. kg-I/hr during sternotomy. Flunitrazepam 0.25 to 0.5 mg and paneuroniurn bromide 0.08 mg-kg -l were given at induction. Measurements were made before and after stcrnotomy in the two groups of patients.In the control group, sternotomy did result in an increased rate-pressure product (p < 0.01), while cardiac index and systemic vascular resistance remained unchanged. In the nieergoline group, increase in rate pressure product was not significant. Cardiac index increased significantly (p < 0.05) as systemic vascular resistance decreased; volume needed to maintain adequate filling pressure was higher in this group (p < 0.05) as was the weight gain during operation (p < 0.05) and postoperative bleeding. This may be related to nicergoline platelet anti-aggregation properties.Our study suggests that deliberate vasodilation such as produced with nicergoline may yield to increased vasoplegia, bleeding and weight gain during operation despite decrease in MVO2 and aftedoad. Intravenous nitroglycerin (NG) is used in coronary patients during anaesthesia to reduce blood pressure (BP) and rate-pressure-product (RPP). It is given orally or intravenously to awake patients for angina. Does the awake patient with cerebration and an active autonomic system react to NG differently than an anaesthetized patient?We studied seven patients having coronary grafts, both awake, sedated and, later, after sternotomy with hypertension. With a radial needle and two thermodiluuon catheters (pulmonary artery and coronary sinus) we determined total coronary sinus flow (CSF), cardiac index (CI), vascular resistance (SVR), total coronary sinus flow (CSF), myocardian oxygen consumption (MVO2) and lactate extraction. Studies were done before and after NG 100 ug/min with mean doses of 1.04 mg given in 10.6 minutes awake and 1.2 mg given in 8.2 minutes after sternotomy.These male patients had a mean age of 57.4 years and mean surface area of 1.95 m 2. Mean...
During thoraco-abdominal aortic aneurysmectomy, the aorta is replaced from the left subclavian artery to the aortic bifurcation. We wished to describe the haemodynamic events occurring during clamping and unclamping of the thoracic aorta and the metabolic changes associated with the interruption of organ perfusion beyond the left subclavian artery. MethodsWe studied I I patients (58-77 years) undergoing thoracoabdominal aortic aneurysm resection without the use of cardiopulmonary bypass. All patients had normal left ventricular systolic function. No patient had angina.Diazepam, fentanyl, pancuronium, air/O2 anaesthesia was used, An arterial line, a Swan-Ganz catheter and a left double lumen endobronchial tube were inserted. The left lung was collapsed to facilitate surgical exposure. Immediately prior to the application of the thoracic aortic cross-clamp, sodium nitroprusside was infused in an attempt to eliminate excessive hypertension at the time of cross-clamp. This was continued for the duration of the cross-clamp (mean 72 minutes) to maintain systolic arterial pressures between 150-200 mmHg. An IV infusion of five per cent sodium bicarbonate was given to achieve a serum b/carbonate of 30-35 nunol.L-~ prior to unclamping of the aorta. ResultsHaemodynamic results (Table I) Cross-clamping of the thoracic aorta produced an immediate increase in mean arterial blood pressure (MAP). This reverted hack to preclamp levels with removal of the clamp, Mean pulmonary artery pressure (MPAP) increased significantly with clamp application and this increase persisted after removal of the clamp. There was no significant change in either systemic vascular resistance (SVR) or pulmonary vascular resistance (PVR). Cardiac indices (CI) were not affected by clamp application but increased significantly after clamp removal. Both the central venous (CVP) and pulmonary capillary wedge pressures (PCWP) increased with clamp application and these changes persisted after clamp removal.Metabolic results (Table 11) An average of 791 mmol of sodium bicarbonate (range 240-1545 mmol) was infused during the time of crossclamp. Unclamping of the aorta with re-establishment of circulation to liver, gut, and kidneys produced an acid wash out, resulting in a highly significant drop in pH (p < 0.001) and plasma bicarbonate. PCO2 rose significantly Catecholamine release may influence the haemodynamic response to anaesthetic induction with narcotics in patients with coronary disease. 1 Previous studies have yielded conflicting results regarding serum catecholamine responses to narcotic anaesthesia.~-4 We have noted unexplained, potentially deleterious, increases in heart rate (HR) and arterial pressure (AP) in occasional patients during induction with high-dose fentanyl. 5 Therefore we tested the hypothesis that catecholamine release accompanies anaesthetic induction with potent narcotics. MethodsInstitutional approval was obtained and all patients gave informed consent. Thirty-three patients with preoperative left ventricular ejection fraction >0.50...
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