Journal of cardiothoracic and vascular anesthesia
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J. Cardiothorac. Vasc. Anesth. · Oct 1993
The effect of preoperative beta-blocker therapy on cardiovascular responses to weaning from mechanical ventilation and extubation after coronary artery bypass grafting.
The hemodynamic and electrocardiographic changes during weaning from mechanical ventilation and tracheal extubation were studied in 75 patients after elective coronary artery bypass surgery. Transfer from synchronized intermittent mandatory ventilation to spontaneous respiration through a T-piece was associated with an increase greater than 20% over baseline in systolic (SBP) and diastolic (DBP) blood pressure in 27% of patients, and in heart rate (HR) in 5% of patients. Although baseline SBP, DBP, and HR differed significantly between the patients taking chronic beta-blocker therapy and those not on beta-blockers (P values all < 0.003), there were no differences between these groups in their response to transfer to the T-piece. (P values: SBP = 0.98; DBP = 0.46; HR = 0.20). ⋯ However, there were significant differences between the chronically beta-blocked and non-beta-blocked groups, both in baseline values for SBP, DBP, and HR (P values all < 0.001), and also in the SBP response (P = 0.007) and HR response (P = 0.02) to extubation. Extubation was associated with a greater than 20% increase in SBP in 8.2% and DBP in 12.2% of chronically beta-blocked patients, compared to 40% and 23% of non-beta-blocked patients, although the DBP response was not statistically different (P = 0.14) between the groups. Similar proportions of patients in both groups increased their HR more than 20% above baseline, but the increase was much greater in the non-beta-blocked group (P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
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J. Cardiothorac. Vasc. Anesth. · Oct 1993
Effect of continuous positive airway pressure applied by face mask on right ventricular function after cardiac surgery.
The effect of respiratory therapy with continuous positive airway pressure (CPAP) on right ventricular function 24 hours after elective cardiac surgery was evaluated in patients with or without severe coronary artery disease. The first group included 10 patients following coronary artery bypass graft (CABG) surgery, and the second group included 10 patients following aortic valve replacement (AVR) without preexisting coronary artery disease. Patients of both groups had preoperative left ventricular ejection fractions above 40%. ⋯ Right ventricular function was estimated at end-expiration by a fast-response thermodilution cardiac output catheter. The results demonstrate that in both groups of patients, CPAP did not significantly modify right ventricular indices, ejection fraction, end-systolic and end-diastolic volume indices, and stroke volume index, indicating that CPAP can safely be applied after elective cardiac surgery in patients with or without severe coronary artery disease and preoperative left ventricular ejection fractions above 40%. Furthermore, the concomitant postoperative intravenous infusion of nitroglycerin (to all 10 patients of the CABG group and to 4 patients of the AVR group) counteracted the expected beneficial effect of CPAP therapy on arterial oxygenation.