ASSESSMENT OF LIDOCAINE METABOLITE FORMATION IN COMPARISON WITH OTHERQUANTITATIVE LIVER-FUNCTION TESTS

In clinical practice, the seriousness of liver disease is assessed bas ed on the combined information from clinical examination, routine bioc hemical tests, and liver histology. Recently, the assessment of hepati c lidocaine metabolism has been proposed as a quantitative liver funct ion test offering valuable additional information. To evaluate whether this new liver function test reflects the combined clinical assessmen t, we prospectively measured lidocaine metabolism in 111 patients with well characterized liver disease. In addition, lidocaine test results were compared with the aminopyrine breath test and the galactose elim ination capacity. Lidocaine (1 mg/kg) was injected i.v. and serum conc entrations of its main metabolite monoethylglycinexylidide were determ ined after 15 min. The results varied widely and the means (+/- S.D.) were similar among patients with mild liver disease (46 +/- 23 ng/ml), but significantly (P < 0.05) lower among patients with Child class A cirrhosis (19 +/- 11 ng/ml) or Child class B or C cirrhosis (21 +/- 19 ng/ml). The [C-13]aminopyrine breath test, however, gave a better dis crimination among patients with increasing severity of liver disease t han lidocaine metabolite formation. The galactose elimination capacity finally best separated patients with mild liver disease from those wi th cirrhosis. The correlations between any two of the different quanti tative liver function tests were weak (R2 consistently < 0.2). We conc lude that lidocaine metabolite formation, like other quantitative live r function tests that are based on the microsomal metabolism of model compounds, quantitates a very particular enzymatic reaction which may not be representative for the functional reserve of the entire organ.