Right Ventricular Function During Weaning From Respirator After Coronary Artery Bypass Grafting: Methods
Following approval by the Humans Investigations Committee of Ulm University and after obtaining written informed consent, 22 patients scheduled for elective coronary artery bypass grafting were investigated. There were 20 men and 2 women with a mean age of 63 years (range, 51 to 72 years). Coronary artery abnormalities included stenosis of the right coronary artery in 18 patients documented in the preoperative catheterization protocol. Patients with depressed ventricular function (left ventricular ejection fraction <40 percent, pulmonary capillary wedge pressure [PCWP] >18 mm Hg), pulmonary artery hypertension (mean pulmonary artery pressure [MPAP] >20 mm Hg), chronic obstructive lung disease, tricuspid valve incompetence, and patients with atrial fibrillation or other arrhythmias were excluded from the study.
Coronary artery bypass surgery, anesthesia (fentanyl, fluni-trazepam, pancuronium bromide in weight-dependent dosages) and postoperative management were performed as our standard procedures in all patients. Cardiopulmonary bypass was instituted with membrane oxygenators and a nonpulsatile flow of 2.4 L/min/m.2 Bretschneiders cardioplegia solution was used for myocardial preservation; in addition, myocardial surface was cooled with iced saline solution. During aortic clamping (ischemia), moderate hypothermia (32°C) was used. After successful operation controlled ventilation (IPPV, PEEP +5 cm H2O) was continued in the ICU until hemodynamic stabilization and final rewarming. Canada health and care mall comments With patients awake and able to breathe spontaneously, weaning was started with PSV at +15 to 20 cm H2O and PEEP at +5 cm H2O. Subsequently, all patients were weaned to pressure support at +10 cm H2O attaining normoventilation (РаСОг, 36 to 44 mm Hg). Then the protocol was started with the BiPAP system or PSV in randomized chronologic order.
The first selected mode was applied for 60 min. At the end of this period, measurements were performed and the second selected mode was started. After a further 60-min period in the second mode, the same measurements were performed again. This period of 60 min is at least as long or even longer as used by others. During the study, changes in baseline catecholamine therapy and additional volume substitution were renounced.