Acute liver failure is associated with a marked depletion of intrahepatic adenosine 5'-triphosphate (ATP), a compound required for the maintenance of hepatic function and enhanced hepatic regeneration.

The aim of this study was to test the safety and efficacy of exogenous ATP at various doses in a rat model of acute liver failure.

Adult male Sprague-Dawley rates (n = 56) received an intraperitoneal dose (1.0 g/kg) of the potent hepatotoxin D: -galactosamine (D: -galN). Thereafter, rats were divided into groups that received saline (n = 18), low (n = 8), moderate (n = 18) or high (n = 12) doses of ATP for 7 days.

There was an inverse correlation between ATP dose and survival such that rats treated with low dose ATP had the highest survival rate (50%) compared to moderate (39%) and high (17%) dose treated groups. However, survival in all treated groups was similar (P = 0.085) to that of controls (45%). Liver biochemistry, regenerative activity and ATP levels were similar in the highest survival group (low dose ATP) versus controls.

These findings suggest that exogenous ATP does not improve and indeed at high doses may impair survival in rats with acute liver failure. Further studies involving a wider range of ATP doses and different routes and frequency of ATP administration are required to determine whether exogenous ATP has therapeutic value in the treatment of acute liver failure.

In order to investigate the effects of verapamil on renal haemodynamics in rats with portal hypertension, verapamil was given at either a low (0.2 mg/kg) or high (2 mg/kg) dose to rats after portal vein ligation. An approximate 12% decrease in mean arterial pressure followed administration of low dose verapamil, with a significant decrease in cardiac output and renal blood flow, as well as reduced portal pressure, observed; these signs were all indicative of a rise in renal vascular resistance. In contrast, the marked fall in both mean arterial pressure and cardiac output with high dose verapamil, accompanied by a significant decrease in portal pressure and no change in renal blood flow, suggests a reduction in renal vascular resistance. This study shows that the acute effects of verapamil on renal haemodynamics may vary with the dose used. Also, acute verapamil administration tends to decrease renal blood flow to alter the autoregulation of the kidney; thus, caution should be taken in the clinical use of verapamil in the treatment of cirrhosis with portal hypertension.

Somatostatin has been used to effectively control acute variceal haemorrhage, with conjectured mechanisms on portal hypertension. We, therefore, evaluated the effects of somatostatin on hepatic and systemic haemodynamics in 15 patients with hepatitis B-related cirrhosis and portal hypertension. All patients received an intravenous, continuous infusion of somatostatin 250 micrograms/h, following a bolus injection of 250 micrograms. In systemic haemodynamics, the mean arterial pressure (MAP) increased (P < 0.05), associated with a reflex bradycardia within 3 min following bolus injections, compared with basal values. The right atrial pressure, pulmonary capillary wedge pressure, inferior vena cava pressure, cardiac index, and systemic vascular resistance remained unaffected after drug infusion. In hepatic haemodynamics, the wedge hepatic vein pressure remained unchanged after drug administration. However, there was an increase in free hepatic vein pressure (FHVP; P < 0.05), and a trend toward a decrease in the hepatic vein pressure gradient (HVPG; P = 0.063), within 3 min after bolus injection. Furthermore, the hepatic blood flow decreased significantly at 10 and 30 min after somatostatin infusion (P < 0.05). The effective sinusoidal perfusion assessed by indocyanine green infusion also decreased progressively at 10 min (P = 0.057) and 30 min (P < 0.05). We concluded that somatostatin, at the dose used in this study, caused a transient and bolus-related vasoconstrictive effect, resulting in increases in MAP and FHVP, a decrease in heart rate, and a trend toward lower HVPG. In addition, somatostatin reduced the hepatic blood flow and effective sinusoidal perfusion which may be hazardous to cirrhotic patients during variceal haemorrhage.

The hemodynamic effects of octreotide were studied in 20 patients with hepatitis B-related cirrhosis. In patients receiving a 100-micrograms bolus and a 100-micrograms/h infusion, heart rate, cardiac index, and systemic vascular resistance showed no significant changes, whereas right atrial pressure, pulmonary capillary wedge pressure, and inferior vena cava pressure decreased significantly after octreotide infusion compared with basal values. In contrast, in patients receiving a 50-micrograms bolus and a 50-micrograms/h infusion, all the systemic hemodynamic values were unaffected. In both groups of patients receiving two different doses of octreotide, the estimated hepatic blood flow, hepatic indocyanine green clearance, and wedge hepatic venous pressure were significantly reduced at 60 minutes after octreotide administration compared with basal values, whereas the hepatic venous pressure gradient remained unchanged. It is concluded that the two different doses of octreotide administration result in the reduction of the wedge hepatic venous pressure and the hepatic blood flow of a similar magnitude, whereas the hepatic venous pressure gradient is unaffected. Octreotide induces discrepant systemic hemodynamic response; this effect is dose related.

1. Vasodilators are currently under investigation as possible therapeutic agents in the treatment of portal hypertension. Among them calcium-channel antagonists and organic nitrates have been of particular interest. Few and conflicting data, however, have been reported on their effect on liver function. 2. Twenty patients with biopsy-proven alcoholic cirrhosis were studied before and 25-35 min following the acute administration of 5 mg verapamil i.v. (eight patients) or 5 mg isosorbide dinitrate sublingually (12 patients). The plasma clearance of indocyanine green (ICG) and its intrinsic hepatic clearance were used as indices of liver function. Seven further patients were investigated before and after a placebo infusion according to the same methodology. 3. No significant change in ICG kinetics was found after verapamil or isosorbide dinitrate.

To elucidate the effects of verapamil on splanchnic haemodynamics in rats with portal hypertension, verapamil was given at a low dose (0.2 mg/kg) and a high dose (2 mg/kg) to the rat model after portal vein ligation. Approximately 10% decrease in arterial pressure was caused by the low dose of verapamil, with significant decreases in cardiac output and portal venous inflow as well as reduced portal pressure; these were all indicative of a rise in portal vascular resistance. In contrast, the marked fall in both arterial pressure and cardiac output in the high dose, accompanied by a significant decrease in the portal pressure and the unchanged portal venous inflow, suggested a reduction in portal vascular resistance. This study shows that the acute effects of verapamil on portal hypertension may vary with the dosage used. These results also demonstrate that, since the therapeutic efficacy and safety of verapamil is only in a very limited range of dose, caution should be taken in its clinical use in the treatment of cirrhosis with portal hypertension.