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Correction: Effects of pirbuterol and sodium nitroprusside on pulmonary haemodynamics in hypoxic cor pulmonale

The value of determining concentrations of C3 and C4 as antigen has been debated by previous workers. C4 and to a lesser extent C3 are acute reactive proteins and sudden rises could be expected during the bypass procedure, which might tend to offset any depletion due to in vivo activation. A correction factor to take into account haemodilution from the pump prime must be applied, but it can be seen that true depletion occurred both in this study (fig 1) and in another.9 The role of corticosteroids has been little studied. No previous investigation has administered the drug in two doses to take account of the dilution shown by Thompson et al1.2 In single dose studies in two patients,6 and in another in five patients,22 the authors concluded that steroids had no effect. Although we also could show no difference in activation in those patients who received the steroid compared with controls, the difference between men and women seen in the steroid group is of considerable interest. In the recent study by Boralessa and colleagues only men were examined.9 We cannot explain the apparent increase in complement activation seen in this subgroup but it is surprising, as steroids may suppress the immune response by their lysosome-stabilising activity.13 A previous study using a single dose of steroid found no difference in lung function.3 The role of pulsatile flow has not been elucidated here in relation to any complement related benefit. This study on a group of only 10 patients was sufficient for statistical analysis but requires extension before firm conclusions can be drawn. It would be useful to relate change in complement activation to clinical outcome. Because of the many surgical factors an extremely large study would be necessary. In our study of 44 patients, three died in the perioperative period, all of whom had received methylprednisolone, but obviously no conclusion can be drawn. Our patients all underwent perfusion through a bubble oxygenator. This might be expected to cause both more trauma to the cellular elements of the blood and greater complement activation than a membrane oxygenator. Previous comparative studies22 have been too small to allow any conclusions to be derived.