Ammonia

Can be measured in serum, plasma or cerebrospinal fluid in suspected cases of hyperammonaemia. Hyperammonaemia presents as neurologic signs including depression, ataxia, head-pressing, staggering, circling, blindness etc.. Two general causes exist comprising:

See also:

1. Failure of hepatic extraction of ammonia which is generated by a normal gastrointestinal tract
2. Excessive production of ammonia from the gastrointestinal tract that overwhelms normal hepatic clearance. This could result from dysbiosis or enteric bleeding which creates considerable substrate for ammoniagenic bacteria in the gut.

Neurologic signs result from cerebral oedema after ammonia is converted to osmotically active glutamine by astrocytes.
Two broad approaches to treatment:

1. Decrease oedema – using boluses of hypertonic 7.2% saline IV (3-5 mL/kg)
2. Decrease ammonia production:
   a. Oral lactulose 0.3 mL/kg q 4-12 hours
   b. Oral metronidazole 15 mg/kg q12 hours