Impact of nitroglycerin infusion on weaning off hypertensive mechanically ventilated chronic obstructive pulmonary disease patients

IntroductionMechanical ventilation (MV) weaning trial can be compared to a cardiac stress test where spontaneous ventilation is a form of an exercise and therefore hemodynamic compromise can occur during the weaning process in critically ill patients. The combined increase in arterial pressure and heart rate during unsuccessful weaning is quite suggestive of weaning failure of cardiac origin. Assessment and prediction of weaning failure from cardiac origin remain complicated in patients with chronic obstructive pulmonary disease (COPD). Recent data showed that COPD itself is a powerful independent risk factor for cardiovascular morbidity and mortality, suggesting that occult cardiac dysfunction could be frequent in patients with COPD. The immediate transition from positive pressure mechanical ventilation to spontaneous ventilation may generate significant cardiopulmonary alterations that are complex and mainly include the inspiratory fall in intrathoracic pressure, the increase in work of breathing, and the catecholamine discharge that occur during abrupt transfer from mechanical ventilation to spontaneous breathing. Therefore, it could be suggested that a treatment targeting the cardiovascular system decreasing the preload might help the heart to tolerate the critical period of weaning more effectively.MethodsThis study was carried on 60 adult male and female patients admitted to the Critical Care Medicine Departments in the Alexandria Main University Hospital and who fulfilled the diagnosis of acute exacerbation of COPD according to the Global initiative for chronic obstructive lung disease (GOLD) [1], and considered eligible for weaning after at least 24 h of invasive mechanical ventilation exhibiting systemic arterial hypertension during the start of spontaneous breathing trial. 30 of them were adult patients and served as the study group (Group I), and the other 30 were age-matched adults who served as the control group (Group II). Each group was subjected to spontaneous breathing trial (SBT) using a T-piece receiving FiO2 the same as during mechanical ventilation. Control group underwent SBT alone while the nitroglycerin group underwent continuous nitroglycerin infusion started at the beginning of the SBT and titrated to maintain normal arterial systolic blood pressure that is; 120–139 mmHg). Hemodynamic, oxygenation and respiratory measurements were performed on the start of SBT, and after a 2-h T-piece SBT.ResultsCompared to the start of SBT, systolic arterial blood pressure and mean arterial blood pressure decreased [from (Mean ± SD) 150.33 ± 14.26, 112.56 ± 9.37 mmHg to 134.33 ± 11.04, 92.78 ± 5.81 mmHg, respectively] in the nitroglycerin group, while the opposite occurred in the control group as systolic arterial blood pressure and mean arterial blood pressure increased [from (Mean ± SD) 144.67 ± 13.58, 109.78 ± 10.09 mmHg to 158.0 ± 19.43, 114.73 ± 10.82 mmHg, respectively]. Mixed central venous saturation (ScvO2) decreased significantly in the control group at the end of SBT [from (Mean ± SD) 71.90 ± 1.84 to 69.25 ± 2.20%], while in the nitroglycerin group, ScvO2 did not change at the end in comparison to the start of SBT [from (Mean ± SD) 71.63 ± 1.75 to 71.12 ± 1.65%]. Nitroglycerin infusion at the start of SBT enabled a successful weaning from mechanical ventilation in 90% of patients in comparison to a successful weaning from mechanical ventilation of only 63.3% in the control group.ConclusionsNitroglycerin infusion might facilitate the weaning off hypertensive COPD patients by alleviating the cardiovascular compromise occurring during liberation from MV.