Objective: To assess the cardiac consequences of successful respiratory weaning using the variations of circulating B-type and atrial natriuretic peptides (BNP, ANP) and Doppler mitral flow.
Design: A prospective preliminary observational study.
Setting: A 14-bed medical ICU in a French university hospital.
Patients: Thirty-one patients undergoing a spontaneous breathing trial on a T-tube.
Interventions: Circulating BNP and ANP levels and Doppler-derived E/A ratio and deceleration time of the E wave were measured before and 1 h after disconnection.
Results: BNP levels increased from 299 pg/ml (range 56-1079) to 412 pg/ml (147-1324) (p=0.02) in patients with systolic left ventricular dysfunction, decreased from 98 pg/ml (25-337) to 45 pg/ml (38-180) (p=0.04) in patients with right ventricular dilation and remained unchanged in patients with neither of these cardiac abnormalities. Overall ANP levels increased from 33 pg/ml to 67 pg/ml (p<0.001) regardless of ventricular function. The E/A ratio increased from 0.91 (0.66-3.56) to 1.17 (0.5-4.76), (p=0.01), after disconnection, whereas deceleration time of E wave decreased from 185 ms (120-280) to 160 ms (70-206) (p=0.02).
Conclusion: During successful weaning from mechanical ventilation ANP levels increase in all patients whereas changes in BNP levels depend on underlying cardiac function. Changes in Doppler mitral flow indexes following ventilator disconnection suggest an increase in left-ventricular filling pressure.