Cardiac dysfunction induced by weaning from mechanical ventilation: incidence, risk factors, and effects of fluid removal.

BACKGROUND

Weaning-induced pulmonary oedema (WiPO) is a well-recognised cause of failure of weaning from mechanical ventilation, but its incidence and risk factors have not been reliably described. We wanted to determine the incidence and risk factors in a population of critically ill patients. In addition, we wanted to describe the effects of diuretics when they are administered in this context.

METHODS

We monitored 283 consecutive spontaneous breathing trials (SBT; T-piece trial) performed in 81 patients. In cases with cardiac output monitoring (n = 85, 29 patients), a passive leg raising (PLR) test was performed before SBT. Three experts established the diagnosis of WiPO based on various patient characteristics.

RESULTS

SBT failed in 128 cases (45 % of all SBT). WiPO occurred in 59 % of these failing cases. Compared to patients without WiPO (n = 52), patients with at least one WiPO (n = 29) had a higher prevalence of chronic obstructive pulmonary disease (COPD) (38 % vs. 12 %, respectively; p < 0.01), previous "structural" cardiopathy (dilated and/or hypertrophic and/or hypokinetic cardiopathy and/or significant valvular disease, 9 % vs. 25 %, respectively; p < 0.01), obesity (45 % vs. 17 %, respectively; p < 0.01), and low left ventricular ejection fraction (55 % vs. 21 %, respectively; p = 0.01). At logistic regression, COPD (odds ratio (OR) 8.7, 95 % confidence interval (CI) 2.0-37.3), previous structural cardiopathy (OR 4.5, 95 % CI 1.4-14.1), and obesity (OR 3.6, 95 % CI 1.2-12.6) were independent risk factors for experiencing at least one episode of WiPO. In 16 cases with WiPO and a negative PLR at baseline, treatment including diuretics was started. In 9 of these cases, the PLR remained negative before the following SBT. A new episode of WiPO occurred in 7 of these instances, while the two other were extubated. In 7 other cases, the PLR became positive before the following SBT. WiPO did not occur anymore in 6 of these 7 patients who were extubated, while the remaining one was not.

CONCLUSIONS

In our population of critically ill patients, WiPO was responsible for 59 % of weaning failures. COPD, previous "structural" cardiopathy, and, to a lesser extent, obesity were the main risk factors. When a treatment including fluid removal had changed preload-independence to preload-dependence, the following SBT was very likely to succeed.