Prostaglandin E1 infusion and functional hepatic flow in control subjects and in patients with cirrhosis

Functional hepatic flow in patients with liver cirrhosis

AIM: To evaluate hepatic reserve function by investigating the change of functional hepatic flow and total hepatic flow in cirrhotic patients with portal hypertension.

METHODS: HPLC method was employed for the determination of concentration of D-sorbitol in human plasma and urine. The functional hepatic flow (FHF) and total hepatic flow (THF) were determined by means of modified hepatic clearance of D-sorbitol combined with duplex doppler color sonography in 20 patients with cirrhosis and 10 healthy volunteers.

RESULTS: FHF, evaluated by means of the D-sorbitol clearance, was significantly reduced in patients with cirrhosis in comparison to controls (764.74 ± 167.91 vs 1 195.04 ± 242.97 mL/min, P < 0.01). While THF was significantly increased in patients with cirrhosis in comparison to controls (1 605.23 ± 279.99 vs 1 256.12 ± 198.34 mL/min, P < 0.01). Portal blood flow and hepatic artery flow all were increased in cirrhosis compared to controls (P < 0.05 and P < 0.01). D-sorbitol total clearance was significantly reduced in cirrhosis compared to control (P < 0.01), while D-sorbitol renal clearance was significantly increased in cirrhosis (P < 0.05). In controls FHF was similar to THF (1 195.05 ± 242.97 vs 1 256.12 ± 198.34 mL/min, P = 0.636), while FHF was significantly reduced compared with THF in cirrhosis (764.74 ± 167.91 vs 1 605.23 ± 279.99 mL/min, P < 0.01).

CONCLUSION: Our method that combined modified hepatic clearance of D-sorbitol with duplex doppler color sonography is effective in the measurement of FHF and THF. FHF can be used to estimate hepatic reserve function.

Cyclooxygenase 2 (COX2)-prostanoid pathway and liver diseases

Cycloocygenases 2 (COX2)-prostanoid pathway plays important and complex roles in the pathogenesis of various liver diseases. Most studies indicated that COX2-prostanoid pathway might suppress hepatic fibrogenesis by decreasing proliferation, migration, and contractility of hepatic stellate cells (HSCs). In animal model, COX2-prostanoid pathway increases portal hypertension, which can be reduced by treatment with COX2 inhibitor. In cirrhosis, COX2-prostanoid pathway may reduce formation of ascites by enhancing free water excretion, and protect gastric mucosa from ulcerative insults. Aberrant expression of COX2 has been well associated with hepatocarcinogenesis. COX2 inhibitors can effectively suppress proliferation of hepatocellular carcinoma (HCC) cells. This provided rationale for further testing COX2 inhibitors as clinical agents for HCC chemoprovention. Further studies will be needed to examine how COX2 inhibitors affect pathogenesis of various liver diseases.

Eicosanoids in cirrhosis and portal hypertension

In the last decade, the knowledge of the pathogenesis of portal hypertension and cirrhosis has increased dramatically. In portal hypertension, almost all the known vasoactive systems/substances are activated or increased and the most recent studies have stressed the importance of the endothelial factors, in particular, prostaglandins. Prostaglandins are formed following the oxygenation of arachidonic acid by the cyclooxygenase (Cox) pathway. An important consideration in portal hypertension and cirrhosis in the periphery is the altered hemodynamic profile and its contributory role in controlling endothelial release of these vasoactive substances. Prostaglandins are released from the endothelium in response to both humoral and mechanical stimuli and can profoundly affect both intrahepatic and peripheral vascular resistance. Within the liver, intrahepatic resistance is altered due to a diminution in sinusoidal responsiveness to vasodilators and an increase in prostanoid vasoconstrictor responsiveness. This review will examine the contributory role of both hormonal and/or hemodynamic force-induced changes in prostaglandin production and signaling in cirrhosis and portal hypertension and the consequence of these changes on the structural and functional response of both the vasculature and the liver.

Evaluation of liver functional reserve by combining D-sorbitol clearance rate and CT measured liver volume

AIM: Our research attempted to evaluate the overall functional reserve of cirrhotic liver by combination of hepatic functional blood flow, liver volume, and Child-Pugh’s classification, and to discuss its value of clinical application.

METHODS: Ninety two patients with portal hypertension due to hepatic cirrhosis were investigated. All had a history of haematemesis and hematochezia, esophageal and gastric fundus varices, splenomegaly and hypersplenia. A 2-year follow-up was routinely performed and no one was lost. Twenty two healthy volunteers were used as control group. Blood and urine samples were collected 4 times before and after intravenous D-sorbitol infusion. The hepatic clearance (CL_H) of D-sorbitol was then calculated according to enzymatic spectrophotometric method while the total blood flow (Q_TOTAL) and intrahepatic shunt (R_INS) were detected by multicolor Doppler ultrasound, and the liver volume was measured by spiral CT. Data were estimated by t-test, variance calculation and chi-squared test. The relationships between all these parameters and different groups were investigated according to Child-Pugh classification and postoperative complications respectively.

RESULTS: Steady blood concentration was achieved 120 mins after D-sorbitol intravenous infusion, which was (0.358 ± 0.064) mmol·L^-1 in cirrhotic group and (0.189 ± 0.05) mmol·L^-1 in control group (P < 0.01). CL_H = (812.7 ± 112.4) mL·min^-1, Q_TOTAL = (1280.6 ± 131.4) mL·min^-1, and R_INS = (36.54 ± 10.65)% in cirrhotic group and CL_H = (1248.3 ± 210.5) mL·min^-1, Q_TOTAL = (1362.4 ± 126.9) mL·min^-1, and R_INS = (8.37 ± 3.32)% in control group (P < 0.01). The liver volume of cirrhotic group was 1057 ± 249 cm³, 851 ± 148 cm³ and 663 ± 77 cm³ in Child A, B and C group respectively with significant difference (P < 0.001). The average volume of cirrhotic liver in Child B, C group was significantly reduced in comparison with that in control group (P < 0.001). The patient, whose liver volume decreased by 40% with the CL_H below 600 mL·min^-1, would have a higher incidence of postoperative complications. There was no strict correspondent relationship between CL_H, liver volume and Child-Pugh’s classification.

CONCLUSION: The hepatic clearance of D-sorbitol, CT measured liver volume can be reliably used for the evaluation of hepatic functional blood flow and liver metabolic volume. Combined with the Child-Pugh’s classification, it could be very useful for further understanding the liver functional reserve, therefore help determine reasonable therapeutic plan, choose surgical procedures and operating time.

Effects of long-term oral misoprostol administration on hepatic amino acid-nitrogen metabolism in patients with cirrhosis

BACKGROUND

The acute infusion of a Prostaglandin of E series 1 (PGE1) analogue results in nitrogen sparing in cirrhosis.

AIMS

To test the effects of long-term oral PGE1 on hepatic and whole-body nitrogen metabolism.

PATIENTS AND METHODS

Ten patients with advanced cirrhosis were studied in paired experiments, before and 30-50 days after oral misoprostol therapy. alpha-Amino-nitrogen levels and urea-nitrogen synthesis rate were measured in the post-absorptive state and in response to continuous alanine infusion (2 mmol/kg per hour for 4.5h). Data were used to compute the functional hepatic nitrogen clearance, i.e. the slope of the regression of alpha-amino-N levels to urea-N synthesis rate, and the apparent nitrogen exchange.

RESULTS

Misoprostol reduced urea-N synthesis rate (during fasting and in response to alanine), resulting in a positive nitrogen exchange. The functional hepatic nitrogen clearance slightly increased, and the regression line was rightwards shifted, indicating a reduced urea synthesis rate at any alpha-amino-N concentration. Amino acid- and ammonia-N did not accumulate in plasma. No systematic effects on insulin and glucagon were observed.

CONCLUSIONS

Data are consistent with a nitrogen sparing mechanism of misoprostol, not mediated by hormone levels. These effects may be beneficial in clinical hepatology, and need to be tested in controlled trials.

Effect of continuous infusion of prostaglandin E1 on hepatic blood flow

STUDY OBJECTIVE

To evaluate the effects of an intravenous infusion of prostaglandin E1 (PGE1) on hepatic blood flow.

DESIGN

Prospective clinical study.

SETTING

University-affiliated hospital.

PATIENTS

16 ASA physical status I and II surgical patients who were scheduled for abdominal surgery.

INTERVENTIONS

Patients were anesthetized with 1% sevoflurane and 66% nitrous oxide. PGE1 0.05 mg/kg/min or PGE1 0.10 mg/kg/min was continuously infused, followed by an infusion of 1000 mL Ringer's acetate solution.

MEASUREMENTS

The hemodynamic effect of PGE1 was examined using pulse dye densitometry (PDD). A nose probe for PDD was used, and 10 mg indocyanine green (ICG) in 2 mL distilled water was bolus-infused into a central venous catheter for each measurement. Cardiac output (CO), circulating blood volume (CBV), and plasma dye clearance rate (K) were monitored from the dye-densitogram. Hepatic blood flow was estimated using the K and CBV values.

MAIN RESULTS

PGE1 did not increase CBV or CO. Even adding a 1000 mL crystalloid infusion did not expand CBV, whereas mean arterial pressure (MAP) significantly decreased from 91.1 +/- 16.5 mmHg to 84.8 +/- 13.5 mmHg (PGE1 0.05 microg/kg/min) and 80.6 +/- 14.4 mmHg (PGE1 0.10 microg/kg/min ) (p < 0.01 compared with control value), then to 72.0 +/- 6.5 mmHg (PGE1 0.10 microg/kg/min + 1000 mL Ringer's acetate) (p < 0.01 compared with control value). Hepatic blood flow changes were 1.46 +/- 0.60 L/min (control), 1.48 +/- 0.45 L/min (PGE1 0.05 microg/kg/min), 1.14 +/- 0.35 L/min (PGE1 0.10 microg/kg/min), and 1.15 +/- 0.19 L/min (PGE1 0.10 microg/kg/min + 1000 mL Ringer's acetate) (no significant difference, p < 0.05). Hepatic blood flow and K values did not statistically significantly differ at each condition.

CONCLUSIONS

PGE1 does not affect blood volume shift, CO, or hepatic blood flow.

Role of prostanoids and nitric oxide inhibition in rats with experimental hepatic fibrosis

Nitric oxide (NO) and prostaglandins have been proposed as vasodilator substances involved in peripheral vasodilatation characteristic of the liver cirrhosis. A link between NO and prostanoids has been suggested. The present study investigated the effect of simultaneous blockade of both, NO synthase (NOS) and cyclooxigenase (COX) in sham-operated (SO), or rats with bile-duct ligation (BDL) in the development of liver fibrosis. Animals were distributed in two groups SO (n=15) or BDL (n=15). Treatments (5 days) started three weeks after surgical procedure. Both, SO and BDL animals were treated with indomethacin (INDO) (5 mg/kg/day) alone, with NG-nitro-L-arginine-methyl-ester (NAME) (4 mg/kg/day) alone or with INDO and NAME combination at the same doses. At the end of follow-up body weight, packed cell volume, mean arterial blood pressure (MAP) and heart rate were measured. Liver tissue was processed for histological studies. In this study, BDL animals showed a decreased MAP. Treatment with L-NAME in BDL rats increased MAP. The chronic COX inhibition alone did not play an important role in the haemodynamic changes. The BDL produced a loss of hepatic structure, with ductular metaplasia that occupied the greater part of the hepatic parenchyma. Also, an important degree of fibrosis was observed. Both NO and PG synthesis inhibitors, alone or in combination, induced enhancing collagen fiber deposition in the hepatic parenchyma. These findings support the notion that the interaction between the NOS and COX pathways should be relevant in hepatic cirrhosis in which both NOS and COX are induced.