SI Units

To the Editor.—  As Marvin M. McCall, MD (241:360, 1979), rightly points out, there are still objections to the International System of Units (SI) from physicians in England Four years ago such a debate raged in the correspondence columns of one of the British journals, until details of a tragic accident were published in The Times (Nov 28, 1975, p 6). This incident underlines the need for a cohesive system of units and emphasizes that the benefit accrues not only for scientists and biochemists but for physicians also.The details of the case are simple. A surgeon asked for "normal saline," which the pharmacist understood to mean 1 normal solution of sodium chloride—a chemist's interpretation of the word "normal" being 1 equivalent/L (ie, 54 g/L). The resultant solution was six times too strong and, of course, killed the patient. Had the concentration required been expressed in SI terms of molarity, this