Evaluation of serum lidocaine/monoethylglycylxylidide concentration to assess shunt closure in dogs with extrahepatic portosystemic shunts

Background: Liver function tests do not always normalize despite successful attenuation of extrahepatic portosystemic shunts (EHPSS).

Objectives: Assess the lidocaine/monoethylglycylxylidide (MEGX) test to determine liver perfusion after EHPSS closure.

Animals: Twenty dogs with EHPSS.

Methods: A prospective cohort study was performed and all dogs were tested at diagnosis, 1, 3, and 6 months postoperatively. After collecting a baseline blood sample (T0), 1 mg/kg body weight of lidocaine was injected intravenously. Fifteen (T15) and 30 minutes (T30) later, blood was collected. Plasma concentrations of lidocaine and its metabolites MEGX and glycylxylidide (GX) were determined, using a high-performance liquid chromatography with electrospray ionization tandem mass spectrometry method. Three months postoperatively, transsplenic portal scintigraphy was performed to determine EHPSS closure.

Results: At T15, median MEGX concentrations were higher in dogs with closed EHPSS compared to diagnosis (33.73 ng/mL [21.11-66.44 ng/mL] vs 13.74 ng/mL [7.25-21.93 ng/mL]; P < .001), but were not different (12.28 ng/mL [10.62-23.17 ng/mL] vs 13.74 ng/mL [7.25-21.93 ng/mL]) in dogs with persistent shunting. Sensitivity to determine shunt closure for MEGX at T15 was 96.2% (95% confidence interval [CI]: 78.4-99.8) and specificity 82.8% (95% CI: 63.5-93.5).

Conclusions and clinical importance: The lidocaine/MEGX test is a promising, rapid, and noninvasive blood test that seems helpful to differentiate dogs with closed EHPSS and dogs with persistent shunting after gradual attenuation.