Blood platelet function in canine acute pancreatitis with reference to treatment with Nafamostat mesilate (FUT-175)

Utility and safety of nafamostat mesilate for anticoagulation in dogs

BACKGROUND

Surgical interventions are recommended for cases of advanced mitral regurgitation, however, limited facilities are available. The most prominent complication in such procedures is heparin-derived bleeding. An alternative anticoagulant to heparin, nafamostat mesilate (NM), can reduce the occurrence of complications associated with heparin such as bleeding or shock.

OBJECTIVES

This study aimed to evaluate the utility and safety of using NM during anaesthesia in canines.

METHODS

Six healthy adult Beagle dogs were anaesthetised, and NM was administered intravenously as a 10 mg/kg bolus dose over 5 min, followed by a continuous infusion of 10 mg/kg/h over 20 min. Blood tests and blood pressure measurements were performed at 0, 5, 25 and 55 min after NM administration.

RESULTS

Activated thromboplastin times at 0, 25 and 55 min were 13.0 ± 0.7 s, 106.7 ± 13.3 s and 28.2 ± 2.9 s, respectively, with a significant difference between 0 and 25 min (p < 0.01) only. No significant differences were observed in prothrombin time, antithrombin, fibrinogen and fibrin degradation product concentrations between timepoints. Activated clotting times (ACTs) at 0, 5, 25 and 55 min were 119.5 ± 9.6 s, 826.7 ± 78.6 s, 924.8 ± 42.4 s and 165.2 ± 13.5 s, respectively. Significant differences were observed between 0 and 5 min (p < 0.05) and between 0 and 25 min (p < 0.05). Blood pressure changes occurred in four dogs (66.7%). No other serious adverse effects were observed.

CONCLUSIONS

ACT results indicated that NM use in anaesthetised healthy dogs was sufficient to obtain procedural anticoagulation with minimal adverse effects. However, these preliminary data require validation in further studies on cardiopulmonary bypass surgery.

Platelet function in dogs with chronic liver disease

OBJECTIVES

To assess platelet function, buccal mucosal bleeding time and plasma von Willebrand factor concentration in dogs with chronic inflammatory and/or fibrotic liver disease and to compare results with those obtained in healthy dogs.

MATERIALS AND METHODS

Preliminary study including 18 dogs with chronic inflammatory and/or fibrotic liver disease undergoing liver biopsy and 18 healthy age-matched control dogs. Platelet function was assessed by measuring closure time with the PFA-100® analyser using adenosine diphosphate (ADP) as an agonist. Buccal mucosal bleeding time, closure time and plasma von Willebrand factor antigen were measured in dogs in both groups. After undergoing ultrasound-guided needle biopsy, dogs were monitored for haemorrhage to determine if there was an association of any measurement with post-biopsy bleeding.

RESULTS

The closure time was not different between the liver disease group (median 76.3; range 53 to 118.5 seconds) and control group (72.8; 57 to 89.5 seconds). The buccal mucosal bleeding time was longer in the liver disease group (median 138; range 95 to 229 seconds) than the control group (103; 63 to 200 seconds). The plasma von Willebrand factor antigen concentration was not different between the liver disease group (median 203; range 109 to 351%) and control group (165.5; 63 to 246%).

CLINICAL SIGNIFICANCE

In this study, dogs with chronic necroinflammatory and/or fibrotic liver disease did not have overt, clinically relevant derangements in platelet function as assessed by buccal mucosal bleeding time, closure time and von Willebrand factor analysis. In addition, none of the dogs undergoing percutaneous ultrasound-guided biopsy in the study exhibited bleeding complications post-biopsy procedure.

Effects of nafamostat mesilate on ADP-induced platelet aggregation and disaggregation in hemodialysis patients

Nafamostat mesilate (NM), a synthetic protease inhibitor, is the most commonly used anticoagulant in the setting of extracorporeal circulation (ECC) in patients with bleeding tendency. It inhibits both platelet aggregation and activation of coagulation factors. Although it has been reported that NM disaggregates aggregated platelets, little is known about such an effect in the setting of hemodialysis therapy (HD). We examined the effects of NM on adenosine 5'-diphosphate (ADP)-induced platelet aggregation and disaggregation using platelet-rich plasma obtained from 6 HD patients. The platelet aggregation was stimulated by 3 microM ADP and change of aggregation was monitored by an aggregometer. NM adjusted to the final concentrations of 0.1 (1.9 x 10(-7)), 1.0 (1.9 x 10(-6)), 10, (1.9 x 10(-5)), and 100 (1.9 x 10(-4)) microg/ml (M) or veronal-buffered saline (VBS) as control was added before or after to the stimulation of ADP. NM not only inhibited platelet aggregation, but also disaggregated already aggregated platelets at concentrations of 1.0 microg/mln or higher. Moreover, NM almost completely disaggregated at 100 microg/ml. This NM concentration of 1.0 microg/ml was lower than the therapeutic concentration in ECC of HD (i.e., 10 M(-5)). Both inhibitory and disaggregatory effects of NM expressed a dose-related dependency. Our results suggest that NM can exert both aggregation inhibitory and disaggregatory effects on platelets of HD patients within the therapeutic concentration.

Platelet hyperfunction in dogs with malignancies

In vitro platelet aggregometry was performed on whole blood samples from 59 dogs with malignancies and 24 control dogs. Three reagents were used for the aggregation studies: collagen, arachidonic acid, and adenosine diphosphate (ADP). The parameters measured to evaluate response to collagen included delay in the aggregation response, slope of the aggregation curve, maximum aggregation, and adenosine triphosphate (ATP) secretion. The platelets of dogs with malignancies exhibited significantly (P < .05) shorter delays in the aggregation response, higher maximum aggregation, and higher ATP secretion when compared to control dogs. For the weaker reagents, ADP and arachidonic acid, the lowest concentration resulting in aggregation was determined. Platelets of dogs with malignancies tended to aggregate in response to lower concentrations of ADP than did those of controls (P < .05). The response of platelets to the concentrations of arachidonic acid employed in this study was poor, with few samples achieving measurable aggregation. The findings of this study suggest that dogs with malignancies have hyperaggregable platelets.