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February 13, 1967

Blood Ammonia

Author Affiliations

From the Department of Surgery, Harvard Medical School, the Fifth (Harvard) Surgical Service, and the Sears Surgical Laboratory, Boston City Hospital.

JAMA. 1967;199(7):473. doi:10.1001/jama.1967.03120070085013

Blood ammonia levels are determined by simple techniques with relatively inexpensive apparatus; therefore, most clinical laboratories should be able to make these measurements. The two principal diffusion methods for blood ammonia are those developed by Conway and Cooke1 and Seligson and Seligson.2 Both are based on the liberation of gaseous ammonia from ammonium salts by strong alkali, and absorption by an acid solution. The amount of ammonia absorbed is then determined by acid titration of colorimetrically by nesslerization. Ammonia concentrations are generally expressed in terms of micrograms per 100 ml of whole blood. Normal blood levels as a rule are less than 100 μg/100 ml. The determination is usually made immediately after the blood is drawn, but in practice it has been observed that blood drawn in vacuum tubes containing sodium edetate and refrigerated will remain stable for several hours.

Ammonia is an essential metabolite. This is emphasized