Effects of Nitric Oxide Donor on Hepatic Arterial Buffer Response in Anesthetized Pigs

The effects of systemic administration of exogenous nitric oxide (NO) donor on hepatic arterial buffer response (HABR) have not yet been studied in an anesthetized model. In this study, 28 anesthetized pigs received administration of sodium nitroprusside (SNP) or nitroglycerin (NTG) as exogenous NO donors. Pressure-flow (P-Q) relationships in the hepatic artery defined the pressure at zero flow (P-Qha = 0) and flow-dependent resistance (R). The magnitude of HABR was evaluated by comparing the change in hepatic arterial blood flow (Delta Qha) divided by the change in portal venous blood flow (Delta Qpv), using the index of change in blood flow (Delta Qha/Delta Qpv). Mean arterial pressure decreased from baseline (95.6 +/- 3.8 mmHg) to SNP condition (68.3 +/- 1.9 mmHg) and decreased from baseline (92.7 +/- 4.4 mmHg) to NTG condition (66.2 +/- 1.7 mmHg). Mean index of change in blood flow (Delta Qha/Delta Qpv) was also significantly increased from baseline (0.19 +/- 0.12) to SNP condition (0.28 +/- 0.17; p=.009) and from baseline (0.18 +/- 0.17) to NTG (0.28 +/- 0.20; p<.05). In conclusion, systemic administration of SNP and NTG increases HABR with reduced hepatic arterial tone under decreased mean arterial pressure, presumably via exogenous NO enhancing another regulatory system and reducing the pressure gradient for sinusoidal washout.