A prospective evaluation of hemodynamic indexes to predict weaning from mechanical ventilation in patients after cardiac surgery

Introduction

Weaning from mechanical ventilation represents an important issue after cardiac surgery because a delayed extubation can burden the patient's recovery health, increasing the risk of infections and the length of hospital stay. Recognized parameters such as minute ventilation, negative inspiratory force, maximal inspiratory pressure ratio, and Tobin index do not predict very well the success of extubation in these patients. We tested whether hemodynamic parameters and indexes predict better successful extubation after cardiac surgery.

Methods

We prospectively evaluated 100 patients undergoing cardiac surgery with pump admitted to the InCor ICU and monitored with Swan-Ganz. Exclusion criteria were congenital diseases, transplantation procedures, chronic renal failure, and ejection fraction lower than 20%.

Results

Patients were considered for extubation if they tolerated a T-piece for 30 minutes. From 100 patients, 88 were successfully extubated and 12 patients failed. There was no difference between groups regarding baseline characteristics, including ejection fraction and co-morbidities. Univariate analysis showed in the successful group a lower duration of pump (55 minutes × 90 minutes, P = 0.038), a lower length of stay in ICU (12 × 32 days, P < 0.0001), a lower BNP level (144 × 422, P = 0.002), and a higher PO₂/FiO₂ (312 × 266, P = 0.043) and a higher VeRT (time recovery minute ventilation) 4 × 2, P < 0.01. Multivariate analysis showed high levels of BNP and of PO₂/FiO₂ at admission are strong predictors of successful weaning.

Conclusions

After cardiac surgery, lower levels of BNP and higher PO₂/FiO₂ are predictors of successful weaning. This suggests that adequate hemodynamic optimization must be achieved in patients to improve outcomes as early weaning of mechanical ventilation.