[Post cardiac surgery In children: extubation failure predictor's]

It is important to know the risk factors for extubation failure (EF) in children submitted to cardiac surgery in order to avoid inherent events due to reintubation (airways injury, usage of medications, cardiovascular changes) and because of prolonged ventilatory support (pneumonias, reduction of the ventilatory muscles strength). The objective of this study is to evaluate mechanical ventilation (MV) parameters, ventilatory mechanics [rapid shallow breathing index (RSBI), ventilatory muscles force [the maximum inspiratory pressure (MIP), the maximum expiratory pressure (MEP) and the load/force balance (LFB)] and blood gases before and after extubation in pediatric patients undergoing cardiac surgery.

Prospective (March 2004 to March 2006) observational cross sectional study, enrolling children submitted to cardiac surgery admitted to an university PICU hospital and considered able to be extubated. With the tracheal tube in situ and maintaining the children spontaneously breathing we evaluate: expiratory minute volume (V E), MIP and MEP. We calculated the RSBI [(RR/VT)/Weight)], LFB [15x [(3xMAP)/MIP] + 0.03 x RSBI-5], the mean airway pressure (MAP) [MAP={(PIP-PEEP)x[Ti/(Te+Ti)]}+PEEP] and the oxygenation index (OI) [OI=(FiO2 x MAP/PaO2)x100]. Arterial blood gas was collected one hour before extubation. If after 48 hours there was no need to reintubate the patient the extubation was considered successful (SE).

59 children were included. EF was observed in 19% (11/59). Median (QI25%-75%) for age, weight, MAP, OI, duration of MV after cardiac surgery (DMV) were respectively, 36 (12-82) months, 12 (8-20) kg, 8 (6-9), 2 (2-5), 1 (1-3) days. Median (QI25-75%) of EF in relation to SE for OI, LFB and DMV were respectively 5(3-8) versus 2(2-4), p = 0.005; [8(6-11) versus 5(4-6), p =0.002 and 3(2-5) versus 1(1-2) days, p = 0.026. Mean ± SD of EF in relation to SE for V E, PaO2 and MIP were respectively 1.7 ± 0.82 versus 3 ± 2.7 mL/kg/min, p = 0.003); 64 ± 34 versus 111 ± 50 mmHg, p = 0.002 and 53 ± 18 versus 78 ± 28 cmH2O; p=0.002. Concerning the risk factors for EF: OI > 2 (area under the ROC 0.74, p = 0.017) and LFB > 4 (area under the ROC 0.80, p = 0.002), achieved a sensibility of 100% and specificity of 80%; MIP < -35 cmH2O (area under the ROC 0.23; p= 0.004) achieved a sensibility of 80% and specificity of 60%.

EF in children submitted to cardiac surgery is related to OI > 2, LFB > 4, DMV > 3 days; V E < 1.7 mL/kg/min, PaO2 < 64 mmHg and MIP < - 53 cmH2O. The kind of cardiac defect, MAP, RSBI and arterial blood gas were not related to EF.