Reply to Dubin

Excerpt

Sir: We would like to thank Dr. Dubin and colleagues for their comments about our recent article [1]. However, we disagree with most of their statements. First of all, the greater sensitivity of Stewart’s method using the strong ion difference (SID) compared to the use of base excess (BE) cannot be explained by the use of different cutoff points. We agree that to diagnose metabolic acidosis, we would need a 5 mmol/l reduction in BE and only 2 mmol/l in SID, which means a greater sensitivity for the last criterion. However, if this were the explanation, it would be enough to change the cutoff point of BE, and all cases diagnosed using the SID criterion would also be identified using the BE criterion. But this is not so. In our cases, of the 34 patients with BE between −1.9 and +1.9 mmol/l, most (n = 27, 79.4%) still had SID <38 mmol/l (data not shown). And we go even further. The best performance is not limited to identifying cases that have not been diagnosed by the traditional evaluation; there is also a better determination of the magnitude of the disorder. In the case of patient 2 of our article [1], if we were to reduce the cutoff point of BE to −2 mmol/l, we would identify metabolic acidosis in this patient. However, the reduction of the base buffer (BB) would be only 3.2 mmol/l; using the criterion of SID the reduction is at least 11 mmol/l. This is a large difference. Independently of the cause of the disorder, the aggressiveness of management will be different. …