Pulmonary hypertensive crisis is a fatal and irreversible postoperative complication of congenital heart disease that has been associated with increased pulmonary flow [6, 7]. Acute hypoxia, hypercarbia, metabolic acidosis, and high doses of catecholamine administration, all of which increase pulmonary vascular resistance, have been considered postoperative risk factors for this condition [2]. Sympathetic stimulation procedures, such as tracheal sectioning, endotracheal intubation, and patient agitation, have also been recognized as risk factors. To decrease these risk factors, maintenance of paralysis and sedation are required for at least the first 20–24 h after surgery considering that the prevalence of pulmonary hypertensive crisis is greatest at around 18 h after surgery [8].
VSD is the most frequent congenital cardiac anomaly [9, 10]; however, the incidence of postoperative events among patients with VSD is lower than that among patients with other complex congenital heart diseases. A study by Lindberg and colleagues reported that the incidence of PH crisis was low (0.7%). They also found that simple defects, such as VSD, had a low incidence [11]. To prevent death after VSD closure in patients with preoperative PH, selection criteria are required to determine patients who need maintenance of paralysis and sedation or those suitable for the fast-track approach. Furthermore, the fast-track approach can prevent postoperative issues, including ventilator-associated pneumonia, delayed oral nutrition, and prolonged postoperative hospital stay in patients with a low risk of PH crisis [12, 13].
Our study demonstrated that intraoperative systolic PAP was one of the predictors of postoperative adverse events after VSD closure in infants with preoperative PH. The intraoperative PAP monitoring approach is straightforward, with possible complications associated with this procedure being merely non-fatal bleeding owing to puncture. In contrast, conventional measurement of PAP after operation is generally more invasive, with trans-thoracic pulmonary artery catheter use having been associated with several complications, such as catheter malfunction, thrombus formation, infection, hemothorax, pneumothorax [14, 15], and cardiac tamponade [16], either during insertion or removal of the catheter.
We found that surgery performed by trainees was one of the risk factors for postoperative adverse outcomes. This could probably be attributed to the increased pulmonary vascular resistance after surgery resulting from longer CPB duration (surgeries by attending physicians: 103 ± 26 min vs. those by trainees: 125 ± 43 min; P = 0.003), which could contribute to the increased postoperative adverse events [17, 18]. Small BW (< 4 kg) was found to be another risk factor for postoperative adverse outcomes. In fact, Sier et al. reported that a BW of < 4 kg during surgery and the presence of inlet VSD were risk factors of developing surgical complete atrioventricular block [19]. Ergün et al. also reported that an age of < 4 months at surgery was a risk factor for prolonged mechanical ventilation time, whereas a large BW during surgery reduced morbidity [18].
Limitations
The present study has some limitations worth noting. First, given that this was a retrospective, non-randomized, single-center study, selection bias might have influenced the results. Secondly, postoperative outcomes, such as the administration of PH medications, might have been influenced by selection bias. Lastly, the duration of intubation could have been influenced by various factors beyond PAP, such as respiratory function. The retrospective nature of the study made it difficult to eliminate cases with respiratory impairments. As such, our findings should be interpreted with these limitations in mind.