Reference Intervals for and the Effects of Sample Handling and Sex on Rotational Thromboelastometry in Healthy Adult Pigs

INVESTIGATION OF A POINT-OF-CARE VISCOELASTIC COAGULATION MONITOR AND ITS COMPARISON TO THROMBOELASTOGRAPHY IN CLINICALLY HEALTHY AFRICAN ELEPHANTS (LOXODONTA AFRICANA)

Elephant endotheliotropic herpesvirus (EEHV) can induce fatal hemorrhagic disease (HD) in African elephants (Loxodonta africana). Once clinical signs develop, progression is rapid, even with aggressive treatment. There is a critical need to develop point-of-care diagnostic tests to aid in identification of EEHV-HD prior to the onset of overt clinical signs. Study objectives were to investigate a novel, point-of-care viscoelastic coagulation monitor (VCM Vet), compare the results to thromboelastography (TEG), and report traditional hemostatic analytes in adult African elephants. Whole blood was collected from seven clinically healthy elephants (four females and three males, 18-47 yr) and analyzed in duplicate via VCM Vet and kaolin-activated TEG 1-3 and 30 min following collection, respectively. Separated plasma was frozen for ancillary coagulation testing. Both analyses generated quantifiable clotting reactions with variables (median [range]) describing clot formation rate (VCM Vet, clot time = 682 s [530-987 s], clot formation time = 244 s [186-744 s], Alpha = 40° [14-47°]; TEG, reaction time = 6.2 min [3.7-11.8 min], kinetic time = 1.3 min [0.9-2.6 min], Alpha = 70° [57-77°]), clot strength (VCM Vet, maximum clot formation = 34 units [20-45 units]; TEG, maximum amplitude = 75 mm [69-80 mm], shear elastic modulus strength = 14.7 Kdynes/s [11.3-19.5 Kdynes/s]), and clot lysis (VCM Vet, lysis index at 30 min = 100% [100-99%], lysis index at 45 min = 98% [95-100%]; TEG, lysis index at 30 min = 0% [0-0.4%], lysis index at 60 min = 1.4% [0-2.6%]) recorded. Additional testing (median [range]) included D-dimer concentration (33 ng/ml [28-94 ng/ml]), prothrombin time (12.4 s [12.2-13.2 s]), activated partial thromboplastin time (17.2 s [14.2-18.8 s]), and fibrinogen concentration (297 [282-383] mg/dL). Tracings generated by VCM Vet and TEG were clinically similar, and there was visual agreement and minimal difference between quantitative variables for duplicate tests. VCM Vet is a promising, user-friendly tool for use in identification and management of coagulopathies in African elephants.

A Novel Sutureless Anastomotic Device in a Swine Model: A Proof of Concept Study

INTRODUCTION

Vascular reconstruction requires technical expertise and is often time consuming. As a novel alternative to traditional hand-sewn vascular anastomoses, the VasoLock (VL), is a nonabsorbable, sutureless anastomosis device with traction anchors designed to hold free artery ends together. These anchors do not penetrate the vessel wall but adhere by leveraging the elasticity of the vessels to fasten blood vessels together. This pilot study assesses the performance and patency of this novel device in a porcine model of femoral artery injury.

METHODS

Female swine (n = 7) underwent femoral artery exposure for a total of 10 VL implanted. Study animals underwent hemodilution to a target hematocrit of 15% and ROTEM was used to assess coagulopathy, followed by an arterial injury via transection. The VL was inserted without any sutures. Flow-probe monitors were positioned proximal and distal to the device and flow rates were measured continuously for a total of 90 min. Flow was analyzed and presented as a ratio of distal to proximal flow with the slope of this ratio across time subsequently determined. Angiographic assessment was completed to evaluate for patency and technical complications after 90 min of implant.

RESULTS

The average animal weight was 44.1 ± 3.2 kg. The average mean arterial pressure at the time of implant was 51.2 ± 7.8 mmHg, median heart rate was 77.4 (IQR = 77.25-157.4) beats per minute, and average temperature was 36.1 ± 1.5°C. The baseline hematocrit was 13.5 ± 3.0%, average pH was 7.20 ± 0.1, average clotting time was 154.1 ± 58.7 s and average clot formation time was 103.4 ± 10.9 s all demonstrating the acidotic, hypothermic, and coagulopathic state of the swine at the time of insertion. During the 90-min observation period, the average flow gradient identified across the VL was 0.99 ± 0.24, indicating no significant change in flow across the VL. The average slope of the gradients was 0.0005 (P = 0.22), suggesting the ratio of proximal and distal flow did not change over the 90 min. Following 90 min of dwell time, all VL were patent without technical complication. Angiographic assessment at 90 min demonstrated no evidence of dissection, device migration, arterial extravasation, or thromboembolism with any of the 10 devices.

CONCLUSIONS

This pilot study demonstrated technical feasibility of the novel VL device over a 90-min observation period. All VL were patent and no negative events or complications were identified. This technology demonstrated significant promise in a coagulopathic state: additional investigation, involving long-term survival, is warranted for further validation.

Evaluation of novel hemostatic agents in a coagulopathic swine model of junctional hemorrhage

BACKGROUND

Hemostatic dressings are used extensively in both military and civilian trauma to control lethal noncompressible hemorrhage. The ideal topical hemostatic agent would provide reliable hemostasis in patients with profound acidosis, coagulopathy, and shock. This study aimed to compare next-generation hemostatic agents against the current military standard in a translational swine model of vascular injury and coagulopathy.

METHODS

Female Yorkshire swine were randomized to eight groups (total n = 63; control n = 14, per group n = 7) of hemostatic agents and included: QuikClot Combat Gauze (Teleflex, Morrisville, NC), which served as the control; BloodSTOP IX (LifeScience Plus, Mountain View, CA); Celox Rapid (Medtrade Product, Crewe, United Kingdom); ChitoSAM 100 (Sam Medical, Tualatin, OR); EVARREST Fibrin Sealant Patch (Ethicon, Raritan, NJ); TAC Wrapping Gauze (H&H Medical, Williamsburg, VA); ChitoGauze XR Pro (Tricol Biomedical, Portland, OR); and X-Stat 30 (RevMedX, Wilsonville, OR). Hemodilution via exchange transfusion of 6% hetastarch was performed to induce acidosis and coagulopathy. An arteriotomy was created, allowing 30 seconds of free bleeding followed by application of the hemostatic agent and compression via an external compression device. A total of three applications were allowed for continued/recurrent bleeding. All blood loss was collected, and hemostatic agents were weighed to calculate blood volume loss. Following a 180-minute observation period, angiography was completed to evaluate for technical complication and distal perfusion of the limb. Finally, the limb was ranged five times to assess for rebleeding and clot stability.

RESULTS

All swine were confirmed coagulopathic with rotational thromboelastography and acidotic (pH 7.2 ± 0.02). BloodSTOP IX allowed a significant increase in blood loss and number of applications required to obtain hemostasis compared with all other groups. BloodSTOP IX demonstrated a decreased survival rate (29%, p = 0.02). All mortalities were directly attributed to exsanguination as a result of device failure. In surviving animals, there was no difference in extravasation. BloodSTOP IX had an increased rebleeding rate after ranging compared with QuikClot Combat Gauze ( p = 0.007).

CONCLUSION

Most novel hemostatic agents demonstrated comparable efficacy compared with the currently military standard hemostatic dressing, CG.

Research-Relevant Clinical Pathology Resources: Emphasis on Mice, Rats, Rabbits, Dogs, Minipigs, and Non-Human Primates

Clinical pathology testing for investigative or biomedical research and for preclinical toxicity and safety assessment in laboratory animals is a distinct specialty requiring an understanding of species specific and other influential variables on results and interpretation. This review of clinical pathology principles and testing recommendations in laboratory animal species aims to provide a useful resource for researchers, veterinary specialists, toxicologists, and clinical or anatomic pathologists.