Plasma ammonia concentration in dogs using ion-exchange method of analysis

Laboratory methods for measuring plasma ammonia concentration were reviewed. The ion-exchange method of analysis was evaluated using canine plasma from 15 clinically normal dogs and five dogs with portosystemic shunts. Mean and standard deviation was 40.3 +/- 8.1 microgram NH(3)/dl in normal dogs, and values ranged from 125 to 200 microgram NH(3)/dl in dogs with portosystemic shunts. Handling of blood samples properly for accurate results was found to require pre-chilled collection tubes, chilling the samples in an ice bath, immediate separation of plasma from red blood cells and immediate analysis for ammonia concentration. The ion exchange method was determined to be sufficiently accurate for clinical use and is suggested for any veterinary clinical pathology laboratory.