Clinical significance of plasma ammonia in patients with generalized convulsion

Plasma ammonia has been used in emergency departments to assess whether or not generalized convulsion attacks exist in patients who are suspected of having convulsions. However, there are few reports that have assessed the relationship between generalized convulsions and hyperammonemia. The clinical significance of plasma ammonia measurements in the diagnosis of generalized convulsions is investigated in this study.

A total of 293 patients who were transported by ambulance to the emergency department of St. Luke's International Hospital, Tokyo, Japan under suspicion of convulsive seizure or disturbance of consciousness were studied.

The objectives were divided into two groups--"Convulsion" and "Non-convulsion"--according to the information provided by witnesses. Bivariate and multivariate analyses were carried out for patient background, clinical course, past medical history and blood test results.

All 11 items showing significant differences on the bivariate analysis were included in the multivariate analysis. Of these, age, total Glasgow Coma Scale score, plasma ammonia level and arterial lactate level showed a significant difference and are recognized as independent findings for the diagnosis of generalized convulsion. The plasma ammonia level had an odds ratio of 14.8 (95% CI, 3.2 to 111.5; p<0.01), 53% sensitivity and 90% specificity when 65 µg/dL was used as the cut-off value.

Plasma ammonia values rise during generalized convulsion. Measurement of plasma ammonia is clinically highly significant as an independent finding during the diagnosis of generalized convulsion.