Factors determining the duration of tracheal intubation in cardiac surgery: a single-centre sequential patient audit.

BACKGROUND AND OBJECTIVE: The study was designed to identify those factors associated with early tracheal extubation following cardiac surgery. Previous studies have tended to concentrate on surgery for coronary artery bypass or on other selected cohorts. METHODS: Sequential cohort analysis of 296 unselected adult cardiac surgery patients was performed over 3 months. RESULTS: In total, 39% of all patients were extubated within 6 h, 89% within 24 h and 95% within 48 h. Delayed extubation (>6 h after surgery) appeared unrelated to age, gender, body mass index, a previous pattern of angina or myocardial infarction, diabetes, preoperative atrial fibrillation, and preoperative cardiovascular assessment, as well as other factors. Delayed tracheal extubation was associated with poor left ventricular, renal and pulmonary function, a high Euroscore, as well as the type, duration and urgency of surgery. Early extubation (<6 h) was not associated with a reduced length of stay in either the intensive care unit or in hospital compared with patients who were extubated between 6 and 24 h. In these groups, it is presumed that organizational and not clinical factors appear to be responsible for a delay in discharge from intensive care. Patients who were extubated after 24 h had a longer duration of hospital stay and a greater incidence of postoperative complications. Postoperative complications were not adversely affected by early tracheal extubation. CONCLUSIONS: In an unselected sequential cohort, both patient- and surgery-specific factors may be influential in determining the duration of postoperative ventilation of the lungs following cardiac surgery. In view of the changing nature of the surgical population, regular re-evaluation is useful in reassessing performance.

Comparison of desflurane and fentanyl-based anaesthetic techniques for coronary artery bypass surgery.

We have compared, in 51 ASA II and III patients undergoing coronary artery bypass surgery, an inhaled anaesthetic technique based on desflurane, supplemented with low-dose (10 micrograms kg-1) fentanyl, with an i.v. technique using high-dose (50 micrograms kg-1) fentanyl with midazolam for induction. Satisfactory records were available for analysis in 50 patients. There were no differences between groups in operating time, cardiopulmonary bypass time, aortic cross-clamp time or duration of stay in the intensive care unit after surgery. Desflurane maintained mean systemic arterial pressure at the awake level during incision and sternotomy (end-tidal concentrations 3.7% and 4.6%, respectively) but decreased it significantly at all other times. With fentanyl, mean systemic arterial pressure was unchanged from awake values during induction and laryngoscopy but increased significantly at incision and sternotomy by 8% and 12.8%, respectively, to exceed the desflurane group at sternotomy by 20 mm Hg (P < 0.001). With desflurane, heart rate remained at 60-67 beat min-1 at all times before cardiopulmonary bypass. This was always lower than the fentanyl group by 5-15 beat min-1 and the difference was significant at induction, during skin preparation and before aortic cannulation. In comparison with the desflurane group, cardiac index was significantly greater in the fentanyl group at induction, laryngoscopy and during skin preparation, but was significantly less before aortic cannulation. The need for vasodilator intervention was significantly more common in the fentanyl group before, during and after cardiopulmonary bypass and for beta adrenoceptor block before cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of histamine-receptor blockade on the hemodynamic responses to protamine.

A prospective randomized study was undertaken to evaluate the use of histamine-receptor blockade to prevent protamine-induced hypotension in patients undergoing elective aortocoronary artery bypass graft surgery. Normotensive patients with good left ventricular function who did not receive vasoactive or inotropic agents after cardiopulmonary bypass (CPB) were allocated to either a study or a control group. After CPB, patients in the study group received 10 mg of chlorpheniramine, and 400 mg of cimetidine, intravenously, five minutes before infusion of protamine. In both groups, protamine was injected via a central venous cannula at 2.5 mg/sec. Hypotension in the control group was significantly more severe and prolonged than in the study group. Systolic and mean arterial blood pressures in the control group fell 35% and 34%, differing significantly (P less than 0.01) from the study group in whom the reduction was 24% for both systolic and mean pressures. In addition, the control group showed significant falls in central venous pressure and increases in heart rate following protamine. In conclusion, it appears that the hemodynamic changes are only partially mediated through histamine action, and the normal response to protamine may be modified, but not abolished, by H1 and H2 receptor blockade. This blockade may, however, prevent the reduction in right heart preload and increase in heart rate following protamine.

Intravenous isosorbide dinitrate during open-heart surgery and its role in the treatment of right-sided congestive heart failure.

Recent awareness of the importance of the functional integrity of the right ventricle and the effect of raised pulmonary vascular resistance on cardiac output after cardiopulmonary bypass has focused attention on means of protecting right ventricular myocardium and reducing right ventricular afterload during open-heart surgery. A study of the acute effects of bolus intravenous isosorbide dinitrate (ISDN) has shown that after cardiopulmonary bypass, bolus intravenous ISDN produced highly significant (p less than 0.001) decreases in mean pulmonary arterial pressure (13%), pulmonary vascular resistance (23%) and the ratio of pulmonary to systemic vascular resistance (20%), indicating that active pulmonary vasodilation had occurred in the absence of other hemodynamic changes. The results suggest that possibly the acute effect of low-dose ISDN after cardiopulmonary bypass is predominantly exerted on the right ventricular afterload if systemic arterial pressure is not elevated. Two different clinical situations are described in which intravenous ISDN proved beneficial, one being acute pulmonary hypertension after protamine sulphate and the second being acute right-sided congestive heart failure with systemic hypotension unresponsive to conventional therapeutic measures. Thus, ISDN may prove a useful agent for alleviating right ventricular dysfunction at a time of not infrequent cardiovascular instability, the period after bypass.

The effects of an intravenous infusion of isosorbide dinitrate during open heart surgery.

Recent awareness of right ventricular dysfunction during open heart surgery has focused attention upon the importance of protection of the right ventricle and control of right ventricular afterload for the maintenance of the cardiac output. Conventional doses of systemic vasodilators, when used to reduce pulmonary vascular resistance, may produce systemic hypotension, reduce coronary arterial perfusion and even lower the cardiac output. A study of the effects of bolus intravenous isosorbide dinitrate during open heart surgery showed that following cardiopulmonary bypass intravenous isosorbide dinitrate produced highly significant falls in pulmonary artery pressure and induced active pulmonary vasodilatation without systemic side-effects or reduced atrial filling procedures. Treatment with intravenous isosorbide dinitrate by low-dose infusion during and after open heart surgery significantly lowered mean pulmonary artery pressure and pulmonary vascular resistance (P less than 0.001) in patients receiving no sympathomimetic drug support. The results suggest that possibly the effect of low-dose isosorbide dinitrate following cardiopulmonary by-pass is exerted predominantly on the right ventricular afterload if systemic arterial pressure is not elevated. This may have applications in the management of pulmonary hypertension and of acute right heart failure following cardiac surgery.

Drugs, alcohol and road accidents in Tasmania.

Drug analyses were performed on 200 blood samples that were taken for alcohol analysis from road users in Tasmania. Alcohol at a concentration of above 0.5 g was found in 75% of the samples, and other drugs were found in 17% of the samples. Cannabis was the most prevalent of these other drugs: it was detected in 6% of road users; benzodiazepine drugs were detected in 5% of road users; and barbiturate drugs were detected in 2% of road users. Alcohol was found in 50% and other drugs were found in 25%, of drivers, riders and pedestrians who were involved in road accidents that were serious enough to cause death or injury. In addition to alcohol, other drugs may be making a significant contribution to road accidents because all the drugs that were identified are capable of impairing psychomotor performance. Of particular concern is the prevalence of cannabis, which is an illegal drug, and barbiturate drugs, which are now prescribed rarely. A well-controlled study is required to quantitate the contribution of drugs other than alcohol to road accidents. In the meantime, drivers should be warned that drugs that depress the central nervous system can be expected to impair driving ability and to increase the risk of an accident.

The acute effects of intravenous isosorbide dinitrate during cardiac surgery.

The acute effects of intravenous isosorbide dinitrate during open heart surgery were studied in 15 adult patients. Consistent and significant (p less than 0.001) reductions in pulmonary vascular resistance (25% before, 23% after, cardiopulmonary bypass) and mean pulmonary artery pressure (14% before, 13% after, cardiopulmonary bypass) were observed in the absence of significant changes in cardiac index, mean systemic arterial pressures or right or left atrial filling pressures. These findings indicate that after cardiopulmonary bypass, when right ventricular dysfunction with raised pulmonary vascular resistance may occur, selective reduction of right ventricular afterload with isosorbide dinitrate may prove beneficial.

Nifedipine and cardiopulmonary bypass. Post-bypass management after continuation or withdrawal of therapy.

The management of the period after hypothermic cardiopulmonary bypass has been compared in a group of patients maintained on nifedipine therapy, a group who had the drug withdrawn at least 24 hours prior to cardiac surgery, and a control group who had never received calcium antagonists. Patients in the drug withdrawal group were significantly more likely to need vasodilator intervention than the treated (p less than 0.001) or the control (p less than 0.05) groups. Although nifedipine withdrawal appeared to reduce the need for inotropic support, compared to treated (p less than 0.001) and control groups (p less than 0.005), this may be at the cost of increasing systemic vascular resistance. This observation, coupled with reports of a rebound phenomenon following abrupt withdrawal of calcium antagonist therapy, suggests that nifedipine should be continued up to the time of surgery.