Effects of propranolol on venous compliance in conscious rats with pre-hepatic portal hypertension

Development of hyperdynamic circulation and response to β-blockers in compensated cirrhosis with portal hypertension

Nonselective β-blockers are useful to prevent bleeding in patients with cirrhosis and large varices but not to prevent the development of varices in those with compensated cirrhosis and portal hypertension (PHT). This suggests that the evolutionary stage of PHT may influence the response to β-blockers. To characterize the hemodynamic profile of each stage of PHT in compensated cirrhosis and the response to β-blockers according to stage, we performed a prospective, multicenter (tertiary care setting), cross-sectional study. Hepatic venous pressure gradient (HVPG) and systemic hemodynamic were measured in 273 patients with compensated cirrhosis before and after intravenous propranolol (0.15 mg/kg): 194 patients had an HVPG ≥10 mm Hg (clinically significant PHT [CSPH]), with either no varices (n = 80) or small varices (n = 114), and 79 had an HVPG >5 and <10 mm Hg (subclinical PHT). Patients with CSPH had higher liver stiffness (P < 0.001), worse Model for End-Stage Liver Disease score (P < 0.001), more portosystemic collaterals (P = 0.01) and splenomegaly (P = 0.01) on ultrasound, and lower platelet count (P < 0.001) than those with subclinical PHT. Patients with CSPH had lower systemic vascular resistance (1336 ± 423 versus 1469 ± 335 dyne · s · cm(-5) , P < 0.05) and higher cardiac index (3.3 ± 0.9 versus 2.8 ± 0.4 L/min/m(2) , P < 0.01). After propranolol, the HVPG decreased significantly in both groups, although the reduction was greater in those with CSPH (-16 ± 12% versus -8 ± 9%, P < 0.01). The HVPG decreased ≥10% from baseline in 69% of patients with CSPH versus 35% with subclinical PHT (P < 0.001) and decreased ≥20% in 40% versus 13%, respectively (P = 0.001).

CONCLUSION

Patients with subclinical PHT have less hyperdynamic circulation and significantly lower portal pressure reduction after acute β-blockade than those with CSPH, suggesting that β-blockers are more suitable to prevent decompensation of cirrhosis in patients with CSPH than in earlier stages.

Intraoperative vital and haemodynamic monitoring using an integrated multiple-channel monitor in rats

The aim of this study is to give a hands-on description of the successful monitoring procedure established for extended liver resections and liver transplantations in rats and to provide the typical range of data as obtained before and after a hepatobiliary surgical procedure (right median hepatic vein [RMHV] ligation) in healthy male Lewis rats. All manipulations were performed in anaesthetized (3% isoflurane in O2 1 L/min) healthy male Lewis rats (250–350 g) with an integrated multiple-channel intraoperative monitor (Powerlab® system) using a series of sensors for data acquisition. Vital parameters (body temperature, electrocardiogram, respiratory rate and heart rate), haemodynamic parameters (mean arterial blood pressure [MAP] and central venous pressure) and liver perfusion parameters (inferior hepatic venous pressure, portal vein pressure [PVP], blood flow of portal vein and inferior hepatic cava) were monitored. Catheters were placed in microsurgical technique after careful exposure guided by anatomical landmarks. Vascular incisions were closed with interrupted sutures. Complete instrumentation of animals was performed within 1 h. No specific complications occurred. Vital and haemodynamic parameters such as MAP (94 ± 16.2 mmHg) or portal pressure (9.6 ± 1.34 mmHg) were in the same range as known for humans (MAP = 100 mmHg, portal pressure = 5–10 mmHg), whereas parameters dependent on the size of the body or organ such as flow rates (portal blood flow = 16.2 ± 6 mL/min) were obviously different compared with those of humans (portal blood flow = 800 mL/min). In conclusion, the normal range for vital, haemodynamic and liver perfusion parameters was reported as reference values to allow quality control for future surgical hepatobiliary research projects. As the procedure can be easily learned, the extensive intraoperative monitoring can be used routinely.

Altered mesenteric venous capacitance and volume pooling in cirrhotic rats are mediated by nitric oxide

In cirrhosis, despite augmented blood volume, effective circulating volume is decreased. This implies abnormal regulation of blood volume, i.e., venous pooling. Because gut veins are the main blood reservoir, we studied mesenteric venous capacitance and compliance in a rat model of cirrhosis. Cirrhosis was induced by bile duct ligation (4 wk). Controls were sham operated. Changes in first-order mesenteric vein diameters induced by drugs, hemorrhage, and stepwise increases in portal pressure (inflatable cuff) were directly observed by intravital microscopy. Effects of nitric oxide on responses to acute graded hemorrhage were studied by use of selective NO synthase (NOS) isoform inhibitors. Pressures were related to diameters to assess capacitance and compliance. Compared with controls, cirrhotic rats demonstrated increased mesenteric venous capacitance and decreased compliance. Norepinephrine induced venoconstriction but did not affect compliance. Prazosin markedly diminished compliance in controls but not cirrhotics. Conversely, the nonspecific NOS inhibitor N-nitro-l-arginine methyl ester (l-NAME) decreased compliance in cirrhotics, but not controls. Tetrodotoxin venodilated controls, venoconstricted cirrhotics, and markedly decreased compliance in both groups. When hemorrhaged, controls rapidly venoconstricted to compensate for initial hypotension, whereas cirrhotic rats remained hypotensive because venoconstriction was severely blunted. Pretreatment with l-NAME or the selective neuronal NOS inhibitors S-methyl-l-thiocitrulline and 7-nitroindazole normalized the homeostatic responses of cirrhotic rats, whereas the selective endothelial-constitutive NOS inhibitor N-iminoethyl-l-ornithine did not affect the response. In conclusion, mesenteric veins of cirrhotic rats showed enhanced capacitance, attenuated compensatory constrictive response to hemorrhage, and decreased compliance. The first two abnormalities were caused by neuronal NOS-derived nitric oxide.