Excessive bleeding at hepatic resection after experimental liver denervation

Hemostatic properties of a venomic protein in rat organ trauma

Previous in vitro work characterized the protease Q8009 isolated from the venom of the Australian brown snake Pseudonaja textilis textilis with Factor Xa-like activity and hemostatic properties. The purpose of the work described here characterizes the in vivo hemostatic properties in a rat model of parenchymatous organ injury. The key parameters of activity included reduction in time-to-hemostasis and total volume of blood loss in spleen, liver and kidney wound models in rats. The surgical protocols involved exposure of the organs via a midline abdominal laparotomy. Using a clean metal template with 6, 6.5, 9 mm holes for spleen, liver and kidney, respectively, a predetermined volume of the organ was gently extruded through the template hole and excised with a razor blade. About 50 to 75 microL of collagen matrix with the different test solutions was applied to the wounds. Blood was collected and at the end of the procedure animals were humanely sacrificed with an anesthetic overdose. Determination of blood was performed using the hematin assay using a standard curve. Blood loss per minute and total blood loss were calculated. Results from the studies demonstrated that the application of Q8009 and collagen matrix to surgical wounds significantly reduced the total amount of blood loss and the time-to-hemostasis. In the spleen wound model, Q8009 at 100, 250 and 1000 microg/ml significantly reduced (p<0.001) the total volume of blood lost relative to thrombin and reduced the time-to-hemostasis by 25-50%, as compared to 7% by thrombin. In the liver wound model, Q8009 at 250 and 1000 microg/ml significantly reduced (p<0.001) the total volume of blood lost relative to thrombin and reduced the time-to-hemostasis from 10.5 min by thrombin to 5.6 min with Q8009. In the kidney wound model, Q8009 at 250 microg/ml significantly reduced (p<0.05) the total volume of blood lost and reduced the time-to-hemostasis by 25% when compared to thrombin. The hemostasis levels were consistent with previous findings in skin wound rat models where Q8009 consistently reduced the total volume of blood lost and shortened time-to-hemostasis. Application of Q8009 plus collagen matrix significantly reduced the volume of total blood loss and time-to-hemostasis in rat surgical organ wound models induced bleeding, as compared to a commercially available hemostat device. The protein Q8009 has greater capacity to reduce blood loss and shorten time-to-hemostasis; highly desirable properties where rapid hemostasis is needed in surgical wounds in parenchymatous organs.

The influence of total porto-systemic shunting on the noradrenaline response and on the contractile effects of various vasoactive agents in small rat portal veins and hepatic arteries

Contractile responses were studied in isolated tubal segments of branches of the rat portal vein (diameter 300 microns) and hepatic artery (diameter 200 microns) 1, 3 and 6 weeks after total porto-systemic shunt operation (PCS). 5-Hydroxytryptamine contracted hepatic arteries concentration-dependently, whereas it produced only weak and inconsistent contractions in portal veins. Vasopressin effectively contracted hepatic arteries, but had no effect on portal veins. Both vessel types responded to prostaglandin F2 alpha with contractions, although the drug potency was relatively low. The responses to these agents were not changed significantly in hepatic arteries or portal veins of PCS rats compared with controls at any of the postoperative time intervals. In both portal veins and hepatic arteries noradrenaline produced contraction-dependent contractions, portal veins being 3 times more sensitive to noradrenaline than hepatic arteries. PCS did not change the nor-adrenaline sensitivity in hepatic arteries, whereas it increased the noradrenaline sensitivity in portal veins after 1, but not after 3 or 6 weeks. This effect was enhanced by cocaine, suggesting a partial sympathetic denervation of branches of the portal vein as well as a complete reinnervation within 3 weeks. Furthermore, the results of this study indicate no influence in any vessel type on the response to several vasoactive agents after depriving the liver of splanchnic venous blood.

Increased galactose clearance after liver transplantation: a measure of increased blood flow through the denervated liver?

This study measured the liver blood flow-dependent index of galactose clearance in patients after liver transplantation, to test the hypothesis that liver blood flow is increased in the denervated liver. Eight normal subjects and 16 patients 1 to 8 months after liver transplant were studied. All patients were stable with no evidence of severe rejection at the time of study. Galactose clearance was measured at steady state during continuous infusion of 75 mg per min of 5% galactose. The results show a statistically significant (p less than 0.01) higher average galactose clearance in the transplant patients (1,187 +/- 316 ml per min per m2) compared to the control group (709 +/- 121 ml per min per m2). The major limiting factor in galactose clearance at low concentrations is liver blood flow, and we interpret these data as evidence for increased blood flow in the transplanted liver. Possible mechanisms for the increased galactose clearance are (i) loss of normal vasomotor tone in the denervated liver, or (ii) persistence of abnormal systemic hemodynamics after transplantation. Elucidation of these mechanisms awaits further study.

Contractile effects of various vasoactive agents in small rat portal veins and hepatic arteries and the influence of sympathetic denervation on the noradrenaline response

Contractile responses were studied in isolated tubal segments of branches of the rat portal vein (luminal diameter approximately 300 microns) and hepatic artery (luminal diameter approximately 200 microns). Portal veins were approximately three times more sensitive to noradrenaline (NA) than hepatic arteries. 5-hydroxytryptamine contracted hepatic arteries concentration-dependently, whereas it produced only weak and inconsistent contractions in portal veins. Vasopressin effectively contracted hepatic arteries, whereas it had no effect on portal veins. Both vessel types responded to prostaglandin F2 alpha with contractions, although the drug potency was relatively low (EC50 greater than 10(-5) mol l-1). Histamine and carbachol failed to induce (hepatic arteries) or caused only weak (portal veins) contractions. Microsurgical hepatic hilar denervation reduced the catecholamine content of the parenchyma to less than or equal to 25% of controls. In both portal veins and hepatic arteries, the denervation procedure increased the NA sensitivity by factors of 3.1 and 2.0, respectively. In non-denervated livers, cocaine produced a similar increase of the NA sensitivity, whereas the drug had no significant effect in vessels from denervated animals. Thus, there was a marked difference between rat portal veins and hepatic arteries in their responsiveness to several contractile agents. Furthermore, the results of the present study indicate that the adrenergic nerves in both vessel types can be adequately removed by the microsurgical denervation procedure used.

A microsurgical method for experimental kidney denervation

A successful microsurgical method for denervation of the kidney in the rat is presented. Unilateral kidney denervation was performed in eight animals. Ten sham-operated animals were used as controls. Under ether anaesthesia, the kidney vessels on one side were exposed. The peritoneum above the vessels was incised and the area was stained with 1% toluidine blue solution. The nerves were identified. With microsurgical technique, the nerves were carefully separated from the vessels and resected. Tissue specimens from both kidneys in all animals were removed and analysed for norepinephrine content. There was no normal difference between the kidneys in the sham-operated rats. About 1 week after denervation, the norepinephrine concentration in the denervated kidney showed a 95% reduction, indicating a complete denervation. The described microsurgical procedure was a rapid, simple, and reproducible method for kidney denervation in the rat.

Significant bleeding at kidney resection after experimental denervation

The effects of microsurgical denervation of the kidney on blood loss, bleeding time, platelet count and APT time in standardized kidney resection were studied in rats. The renal nerves running alongside the blood vessels were stained, identified and resected with a microsurgical technique. One week after the denervation, the blood loss and bleeding time at kidney resection were significantly greater than in control rats (without denervation). The bleeding resulted in reduced haemoglobin and haematocrit values, but the platelet count and APT time were unchanged. Platelet aggregation was not influenced by the denervation procedure. The increased bleeding at parenchymal kidney resection in the denervated rats was regarded as a consequence of interrupted nerve supply to the kidney. The effects on bleeding may have implications for renal surgery in humans.