Reply to Rezaei et al.

We read the letter of Rezaei et al. [1] with interest. We think that the most important point to bear in mind is that the lungs are very fragile organs; they suffer easily in response to the slightest aggression. This is illustrated by the fact that pulmonary complications often follow a severe acute illness, almost independently of the nature of the primary illness. One form of pulmonary aggression may well be the opening of the pleurae, as the authors mention, since this may alter respiratory mechanics. Indeed, the fact that even such seemingly slight aggression is significant is testimony to the fragility of these organs.

However, the lungs may suffer in response to many other processes, some of which are well known and much more aggressive than opening the pleurae; examples include septic shock, renal/hepatic failure and blood transfusion. Many other examples may be cited, but one that particularly concerns us is the cessation of mechanical ventilation during cardiopulmonary bypass with its consequent atelectrauma and the barotrauma associated with the need for lung re-expansion prior to termination of the bypass as mentioned in our article [2]. This concerns us not only because both atelectrauma and barotrauma are well known to damage the lungs but also because they are avoidable, i.e. this is an iatrogenic complication. It is difficult to imagine that opening the pleurae could possibly even come close to such aggression. To us, it seems naive to think that the lungs would not suffer by cessation of ventilation during cardiopulmonary bypass as long as the pleural cavities are not breached.

Nevertheless, the pleurae were likely opened in all patients presented in our article in both the control group and the ventilated group, although we do not keep records of this. These patients underwent repair of either transposition of the great arteries or hypoplasia of the aortic arch; it is difficult to carry out such procedures in neonates without opening the pleurae, especially since we peel the pleurae off the pericardium so that a generous pericardial patch may be excised for use during the repair. Therefore, we assume that all patients had this in common such that this would not be a confounding factor in our results, which show that mechanical ventilation during cardiopulmonary bypass is clearly beneficial.

REFERENCES