Studies of the source and significance of blood ammonia. IV. Early ammonia peaks after ingestion of ammonium salts.

In the course of stuidies of ammonia absorption from the gastrointestinal tract in cirrlhosis it was notedl that the hiiglhest arterial ammonia levels were achieved slhortly after oral ingestioni of ammonium clhloride. Peak values usually occurred witlhin 15 min of adnministration. The rapid appearance time of the zenith was surprising in view of previous studies of ammonia tolerance, whiclh lhad suggeste(l that the peak bloocl amminoniia level, determined on eitlher arterial or venous blood, occurred lbetween 30 ancd 60 min after ingestion(l-3). Several laboratories, ours incltuded, lhave usedl the 45-min blood ammonia level as tlle peak value in performing ammonia tolerance tests(4-6). We have previotusly lpresentedl data associating impairedl ammoniia tolerance with portal-systemic shunting(5), esoplhageal varices(7) andl patent portacaval anastomoses(8) using the 45-min arterial ammoinia level. The present inivestigation was tun(lertaken to (letermine the nature of the arterial ammoInia tolerance curIve in nlormal sul)jects ail(l cirrlotic platients. Iln a(llitioni, it was planlecd to compare the peak arterial ammonia levels, whenever they occurred, witlh the 45-min level in assessing the presence or absence of esoplhageal varices in thie cirrlhotic patients so studied.