Effect of site of lactate infusion on regional lactate exchange in pigs.

BACKGROUND: The rate of extra-hepatic lactate production and the route of influx of lactate to the liver may influence both hepatic and extra-hepatic lactate exchange. We assessed the dose-response of hepatic and extra-hepatic lactate exchange during portal and central venous lactate infusion. METHODS: Eighteen pigs randomly received either portal (n=5) or central venous (n=7) lactate infusion or saline (n=6). Sodium lactate was infused at 33, 66, 99, and 133 µmol kg⁻¹ min⁻¹ for 20 min each. Systemic and regional abdominal blood flows and plasma lactate were measured at 20 min intervals until 1 h post-infusion, and regional lactate exchange was calculated (area under lactate uptake-time curve). RESULTS: Total hepatic lactate uptake [median (95% confidence interval)] during the experimental protocol (140 min) was higher during portal [8198 (5487-12 798) µmol kg(-1)] than during central venous lactate infusion [4530 (3903-5514) µmol kg⁻¹, P<0.05]. At a similar hepatic lactate delivery (∼400 µmol kg⁻¹ min⁻¹), hepatic lactate uptake [mean and standard deviation (sd)] was higher during portal [118 (sd 55) µmol kg⁻¹ min⁻¹] than during central venous lactate infusion [44 (12) µmol kg⁻¹ min⁻¹, P < 0.05]. Time courses of arterial lactate concentrations and lactate uptake at other measured regions were similar in both groups. CONCLUSIONS: Higher hepatic lactate uptake during portal compared with central venous lactate infusion at a similar total hepatic lactate influx underlines the role of portal vein lactate concentration in total hepatic lactate uptake capacity. Arterial lactate concentration does not depend on the site of lactate infusion. At higher arterial lactate concentrations, all regions participated in lactate uptake.