Effect of dopamine-induced changes in splanchnic blood flow on MEGX production from lidocaine in septic and cardiac surgery patients

The production of monoethylglycine xylidide (MEGX) from lidocaine is thought to be dependent on hepatic blood flow. We assessed the relationship between hepatosplanchnic blood flow, lidocaine uptake, and the production of MEGX from lidocaine in seven patients after cardiac surgery and in nine septic patients. Systemic (pulmonary artery catheter) and splanchnic (hepatic vein catheter and dye dilution) hemodynamics and arterial and hepatic venous lidocaine and MEGX concentrations were measured after a lidocaine bolus injection (1 mg/kg) before and 90 min after increasing cardiac output by at least 25% with dopamine. Dopamine infusion in cardiac surgery patients 4.2 (1.4-8.5) microg x kg(-1) x min(-1) (median, range) and in septic patients 4.0 (2.1-9.0) microg x kg(-1) x min(-1)] increased splanchnic blood flow in cardiac surgery patients from 0.65 (0.12) L x min(-1) x m(-2) to 0.84 (0.14) L x min(-1) x m(-2) mean (standard deviation) P = 0.018) and in septic patients from 0.91 (0.32) L x min(-1) x m(-2) to 1.12 (0.40) L x min(-1) x m(-2) (P = 0.038). Splanchnic MEGX production for the 30 min after lidocaine injection was higher in cardiac surgery patients than in septic patients both at baseline 4130 (1100) microg x m(-2) vs. 930 (420) microg x m(-2) (P < 0.005)] and afterdopamine infusion 4480 (1000) microg x m(-2) vs. 1090 (620) microg x m(-2) (P = 0.005)]. We found no correlation between changes in MEGX production and changes in splanchnic blood flow. Patients with sepsis have severe impairment of cytochrome P450-dependent liver function, which is not influenced by acute changes in hepatosplanchnic blood flow. MEGX production cannot be used as an estimate of changes in splanchnic blood flow.