[Investigation on risk factors of prolonged mechanical ventilation after cardiopulmonary bypass]

To analyze the risk factors of prolonged mechanical ventilation (PMV) after cardiopulmonary, and to improve the management for the patients underwent respiratory complications.

From January 1995 to August 2003, there occurred 50 cases of patients in our ICU. The clinical data of 50 cases of patients in our ICU who undergoing open heart surgery was reviewed retrospectively, and the multivariate liner regress analysis model was used to evaluate the influence of the variables.

The age of the patients underwent PMV ranged from 14 to 65 years old, body weight 28 to 80 kg, 28 cases of the patients were male, and 22 female. Mean cardiopulmonary bypass (CPB) time was (156.38+/-52.02) minutes. Mean mechanical ventilation time was (62.86+/-22.55) hours. The mortality was 18.0 percent. Compared to the contrast, the patients in prolonged ventilation groups were in higher NYHA class, underwent longer period of CPB time and cross-clamping time (P<0.001). The postoperative arterial partial pressure of oxygen (PaO(2)) and PaO(2)/FiO(2) were much lower, the alveolar-arterial oxygen pressure gradient and the intrapulmonary shunt (Qs/Qt) were higher (all P<0.001). There was no significant difference in pulmonary dynamic compliance between the two groups. The postoperative drainage was much more, and the myocardial enzymes were in higher level in prolonged ventilation groups (both P<0.001). The incidence of postoperative complications was higher (P<0.001). Multivariate liner regress analysis showed that the duration of mechanical ventilation was related with the preoperative cardiac function, CPB time, PaO(2)/FiO(2), the level of postoperative myocardial enzyme, and the quantity of postoperative drainage.

This study shows preoperative cardiac function, CPB time, PaO(2)/FiO(2), the level of postoperative myocardial enzyme and the quantity of postoperative drainage are risk factors of PMV.