Systematic evaluation of evidence on veterinary viscoelastic testing Part 3: Assay activation and test protocol

The establishment of reference intervals for the ClotPro thromboelastometry device in healthy dogs

OBJECTIVE

To establish reference intervals using a new point-of-care thromboelastometry device in dogs for the extrinsically activated test (EX-test), intrinsically activated test (IN-test), fibrin polymerization test (FIB-test), ecarin test (ECA-test), and tissue plasminogen activator test (TPA-test) and to investigate the effects of storage time on the results.

DESIGN

Prospective clinical study in 2022.

SETTING

University teaching hospital.

ANIMALS

Forty-eight healthy privately or university-owned dogs were prospectively enrolled and included on the basis of normal physical examination and normal baseline laboratory results (CBC, biochemistry profile, prothrombin time, and activated partial thromboplastin time [aPTT]).

INTERVENTIONS

After a 30-minute storage time, the EX-test, IN-test, FIB-test, ECA-test, and TPA-test were performed on citrated blood samples. To determine the effect of storage time, 11 samples had the EX-test, FIB-test, and IN-test repeated 90 and 150 minutes after sample collection.

MEASUREMENTS AND MAIN RESULTS

Ten thromboelastometry parameters were evaluated for each test. Reference intervals were calculated using the robust method for parametric data, and the robust Box-Cox transformed or nonparametric methods were used for nonparametric data. Increasing storage time resulted in more hypocoagulable tracings. A correlation was found between the IN-test and aPTT (r = 0.62, P < 0.0001). Other weak to moderate correlations were seen between thromboelastometry parameters and platelet count and hematocrit.

CONCLUSIONS AND CLINICAL IMPORTANCE

The development of reference intervals for the thromboelastometry device allows for the clinical use of this technology. Analyzing samples after a prolonged storage time of more than 30 minutes may result in erroneous results. Results may also be affected by an abnormal hematocrit or platelet count.

Comparison of Citrated Whole Blood to Native Whole Blood for Coagulation Testing Using the Viscoelastic Coagulation Monitor (VCM Vet™) in Horses

Viscoelastic monitoring of horse coagulation is increasing due to its advantages over traditional coagulation testing. The use of a point-of-care viscoelastic coagulation monitor (VCM Vet™) has been validated for use in horses using native whole blood (NWB) but has not been assessed using citrated whole blood (CWB), a technique that might have advantages in practicality and precision. Blood was collected from 70 horses, tested in duplicate immediately using NWB (T0), and stored at room temperature as CWB for testing in duplicate at 1 (T1) and 4 (T4) hours after venipuncture for comparison to NWB. Of these horses, 20 were classified as clinically healthy and used to determine reference intervals for CWB at 1 and 4 h post-collection. There were clinically relevant differences in all measured viscoelastic parameters of CWB compared to NWB meaning that they cannot be used interchangeably. These differences were not consistent at T1 and T4 meaning the resting time of CWB influences the results and should be kept consistent. The use of CWB in this study also resulted in more machine errors when compared to NWB resulting in measurements that might not be interpretable.

Increased packed cell volume alters point of care viscoelastic clotting parameters in horses

BACKGROUND

Polycythaemia and coagulopathy are identified risk factors for non-survival in critically ill horses. Assessment of coagulation is recommended for critical care monitoring but may be affected by concurrent polycythaemia.

OBJECTIVE

To evaluate the effects of induced polycythaemia on coagulation parameters as measured by a point-of-care viscoelastic coagulation device (VCM Vet™).

STUDY DESIGN

Prospective interventional study.

METHODS

Healthy adult horses (n = 7) were given 6 mcg/kg of phenylephrine IV over 15 min to induce transient polycythaemia. Samples for packed cell volume (PCV), total solids (TS), complete blood count (CBC), activated partial thromboplastin time (PTT), prothrombin (PT) and VCM Vet™ viscoelastic testing were collected at baseline (T0), 5 min (T1) and 2 h (T2) post-phenylephrine infusion. Splenic volume was measured by transabdominal ultrasonography. VCM Vet™ and plasma-based coagulation parameters, splenic volume and haematologic values were compared within and between time points.

RESULTS

Splenic volume decreased from T0 (11.5 ± 4.8 L) to T1 (6.1 ± 2 L, p = 0.04) and returned to baseline volume by T2 (12.1 ± 3.9 L, p = 0.8), consistent with phenylephrine-induced splenic contraction. PCV increased from T0 (37% ± 4%) to T1 (56.3% ± 5.3%; p < 0.001) and returned to baseline at T2 (41.6% ± 3.6%; p = 0.1). A10 and A20 (amplitude at 10 and 20 min, VCM units) were decreased from T0 (12.6 ± 1.6, 18.9 ± 5) to T1 (5.4 ± 1.9, 7.6 ± 2.4; both p < 0.001) and remained lower than baseline at T2 (9.3 ± 2.1, 12.7 ± 3; both p = 0.01). PT and PTT remained within reference ranges with no significant difference over time (p = 0.5 and 0.09, respectively). PCV was negatively correlated with CFT (R = -0.61, p = 0.003), A10 (R = -0.9, p < 0.001) and A20 (R = -0.87, p < 0.001).

MAIN LIMITATIONS

Small sample size, limited to healthy mares.

CONCLUSIONS

Phenylephrine-induced polycythaemia was associated with hypocoagulable viscoelastic traces using the VCM Vet™ device without effect on plasma-based coagulation assessments or platelet number. Further investigation of viscoelastic testing is needed in horses with increased PCV due to clinical illness.

Comparison of shelf-stable and conventional resuscitation products in a canine model of hemorrhagic shock

BACKGROUND

Treatment of severe hemorrhagic shock typically involves hemostatic resuscitation with blood products. However, logistical constraints often hamper the wide distribution of commonly used blood products like whole blood. Shelf-stable blood products and blood substitutes are poised to be able to effectively resuscitate individuals in hemorrhagic shock when more conventional blood products are not readily available.

METHODS

Purpose-bred adult dogs (n = 6) were anesthetized, instrumented, and subjected to hemorrhagic shock (mean arterial pressure <50 mm Hg or 40% blood volume loss). Then each dog was resuscitated with one of five resuscitation products: (1) lactated ringers solution and hetastarch (LRS/Heta), (2) canine chilled whole blood (CWB), (3) fresh frozen plasma (FFP) and packed red blood cells (pRBC), (4) canine freeze-dried plasma (FDP) and hemoglobin-based oxygen carrier (HBOC), or (5) HBOC/FDP and canine lyophilized platelets (LyoPLT). Each dog was allowed to recover after the hemorrhage resuscitation event and was then subjected to another hemorrhage event and resuscitated with a different product until each dog was resuscitated with each product.

RESULTS

At the time when animals were determined to be out of shock as defined by a shock index <1, mean arterial pressure (mmHg) values (mean ± standard error) were higher for FFP/pRBC (n = 5, 83.7 ± 4.5) and FDP/HBOC+LyoPLT (n = 4, 87.8 ± 2.1) as compared with WB (n = 4, 66.0 ± 13.1). A transient increase in creatinine was seen in dogs resuscitated with HBOC and FDP. Albumin and base excess increased in dogs resuscitated with HBOC and FDP products compared with LRS/heta and CWB ( p < 0.01).

CONCLUSION

Combinations of shelf-stable blood products compared favorably to canine CWB for resolution of shock. Further research is needed to ascertain the reliability and efficacy of these shelf-stable combinations of products in other models of hemorrhage that include a component of tissue damage as well as naturally occurring trauma.

Platelet hyperresponsiveness and increased platelet-neutrophil aggregates in dogs with myxomatous mitral valve disease and pulmonary hypertension

BACKGROUND

Pulmonary hypertension (PH) in dogs with myxomatous mitral valve disease (MMVD) is caused by increased pulmonary venous pressure. Thrombosis, vascular remodeling, and vasoconstriction mediated by platelets could exacerbate PH.

HYPOTHESIS

Dogs with PH will exhibit a hypercoagulable state, characterized by increased platelet activation, platelet-leukocyte, and platelet-neutrophil aggregate formation.

ANIMALS

Eleven dogs (≥3.5 kg) diagnosed with MMVD and PH and 10 dogs with MMVD lacking PH.

METHODS

Prospective cohort ex vivo study. All dogs underwent echocardiographic examination, CBC, 3-view thoracic radiographs, and heartworm antigen testing. Severity of PH and MMVD were assessed by echocardiography. Viscoelastic monitoring of coagulation was assessed using thromboelastography (TEG). Platelet activation and platelet-leukocyte/platelet-neutrophil interactions were assessed using flow cytometry. Plasma serotonin concentrations were measured by ELISA.

RESULTS

Unstimulated platelets from dogs with MMVD and PH expressed more surface P-selectin than MMVD controls (P = .03). Platelets from dogs with MMVD and PH had persistent activation in response to agonists. The number of platelet-leukocyte aggregates was higher in dogs with MMVD and PH compared with MMVD controls (P = .01). Ex vivo stimulation of whole blood resulted in higher numbers of platelet-neutrophil aggregates in dogs with MMVD and PH (P = .01). Assessment of hypercoagulability based on TEG or plasma serotonin concentrations did not differ between groups.

CONCLUSION AND CLINICAL IMPORTANCE

Platelet hyperresponsiveness and increased platelet-neutrophil interaction occur in dogs with MMVD and PH, suggesting that platelets play a role of in the pathogenesis of PH. Clinical benefits of antiplatelet drugs in dogs with MMVD and PH require further investigation.

Viscoelastic coagulation monitoring parameters in cats with acute arterial thromboembolism

BACKGROUND

Hypercoagulability has been documented in cats with cardiac disease. However, hemostatic parameters, including viscoelastic coagulation monitoring (VCM) have not been reported in cats with arterial thromboembolism (ATE).

HYPOTHESIS/OBJECTIVES

Compare VCM parameters in cats with acute cardiogenic ATE and in control cats.

ANIMALS

Sixteen cats with ATE and 30 control cats.

METHODS

Multicenter university-based prospective study. Cardiogenic ATE was diagnosed based on physical examination and by ultrasonographically-diagnosed left atrial enlargement. Viscoelastic coagulation monitor analysis, CBC, serum biochemistry profile and coagulation profile were performed at admission in cats with ATE. Analysis from healthy control cats was performed using blood collected by direct venipuncture. Our objective was comparison of VCM parameters clot time (CT), clot formation time (CFT), alpha angle (Angle), maximum clot formation (MCF), amplitude at 10 and 20 minutes (A10 and A20, respectively) and clot lysis index at 30 and 45 minutes (LI30 and LI45, respectively) between ATE and control cats.

RESULTS

Cats with ATE had a decreased angle compared to control cats, with a median (range) of 43° (30-48°) compared to 47° (14-59°; P = .01). The parameters A10, A20 and MCF were decreased in ATE cats compared to control cats with a median (range) of 19 units (8-32) compared to 22 units (6-38), 24.5 units (11-40) compared to 29 units (10-47) and 29.5 units (13-44) compared to 33.5 units (14-53), respectively (P = .01, .01 and .01, respectively). The parameters CT, CFT, LI30 and LI45 were similar between groups (P = .22, .09, .62 and .34, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Cats with cardiogenic ATE cats have VCM parameters consistent with hypocoagulability compared with healthy cats.

Prothrombin and activated partial thromboplastin times, thromboelastography, hematocrit, and platelet count in a feline hemorrhage/over-resuscitation model using lactated Ringer's solution or 6% tetrastarch 130/0.4

OBJECTIVE

To describe and compare prothrombin time (PT), activated partial thromboplastin time (aPTT), thromboelastography (TEG), HCT, and platelet count measurements in a hemorrhage/over-resuscitation model.

DESIGN

Randomized crossover study.

SETTING

University teaching hospital.

ANIMALS

Six cats.

INTERVENTIONS

Anesthetized cats underwent 3 treatments at 2-month intervals. The treatments were as follows: NHR-no controlled hemorrhage and sham resuscitation; LRS-controlled hemorrhage and lactated Ringer's solution (LRS) for resuscitation; and Voluven-controlled hemorrhage and 6% tetrastarch 130/0.4 for resuscitation. The LRS and Voluven were administered at 60 and 20 mL/kg/h, respectively, for 120 minutes. Blood samples were drawn for PT, aPTT, TEG, HCT, and platelet count measurements at a healthy check (T - 7d), after controlled hemorrhage (T0), at 60 and 120 minutes of resuscitation (T60 and T120), and at 24 hours after completion of resuscitation (T24h). Data were analyzed using a general linear mixed model approach (significance was P < 0.05).

MEASUREMENTS AND MAIN RESULTS

Total median blood loss (controlled hemorrhage and blood sampling from T0 to T120) at T120 was 11.4, 31.0, and 30.8 mL/kg for NHR, LRS, and Voluven, respectively. PT and aPTT during LRS and Voluven were prolonged at T60 and T120 compared to NHR (P < 0.001). On TEG, the reaction time, kinetic time, and alpha-angle were within reference intervals for cats at all time points in all treatments, while maximum amplitude was less than the reference interval (40 mm) at T0, T60, and T120 during Voluven and at T60 and T120 during LRS compared to NHR (both P < 0.001). The HCT and platelet count were significantly lower at T60 and T120 during LRS and Voluven compared to NHR (P < 0.001).

CONCLUSIONS

Hypocoagulopathy was observed during hemorrhage and liberal fluid resuscitation. Prolongation of PT and aPPT and decreased clot strength may have been caused by hemodilution and platelet loss.

Point-of-care viscoelastic coagulation monitor parameters in Amazon parrots (Amazona spp.)

OBJECTIVE

To evaluate the feasibility of the point-of-care viscoelastic coagulation monitor (VCM) in Amazon parrots (Amazona spp.) and describe the parameters with fresh whole-blood samples in healthy Amazon parrots.

DESIGN

A total of 18 Amazon parrots were enrolled. Physical examinations, a CBC, and a biochemistry profile, including bile acids, were performed on all parrots. VCM tracings were obtained at the time of venipuncture for baseline laboratory work.

MEASUREMENTS AND MAIN RESULTS

The median clot time was 2102 seconds (range: 38.6-3599 s), median clot formation time was 929 seconds (range: 21.4-1711 s), median alpha angle was 20 (range: 6-67), and the median maximum clot formation was 8.5 (range: 0-36). The median lysis index at 30 minutes (LI30) was 100 (range: 98-100), and the median lysis index at 45 minutes (LI45) was 100 (range: 90-100). Of 18 samples, alpha angles were not reported in 7 samples, LI30 was not reported in 10 samples, and LI45 was not reported in 12 samples. Of the qualitative curves, 6 reflected normal mammalian curves, and the remainder were consistent with a hypocoaguable state.

CONCLUSIONS

The results were markedly variable, with the majority of VCM tracings being hypocoagulable in comparison with reference intervals established for dogs and cats. Using these protocols, the VCM is not reliable in Amazon parrots. Future areas of investigation include altering the temperature during sample analysis, the use of activators, or an exchange of clotting reagents for an extrinsic pathway activator, which may contribute to the success of this device in avian species.

Preliminary evaluation of reference intervals for a point-of-care viscoelastic coagulation monitor (VCM Vet) in healthy adult horses

OBJECTIVE

To evaluate a point-of-care viscoelastic coagulation monitor (VCM Vet) for use in horses by assessing variability between devices and establish reference intervals (RIs) for healthy adult horses.

DESIGN

Prospective observational study.

SETTING

Two university teaching hospitals.

ANIMALS

Healthy adult horses (n = 68).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood collected by direct jugular venipuncture was applied directly from the syringe into 2 VCM Vet cassettes to establish coefficients of variation (CVs) and RIs for reported parameters of clotting time (CT), clot formation time (CFT), alpha angle, amplitude at 10 and 20 minutes, maximum clot firmness, and lysis index at 30 and 45 minutes. CVs for each parameter were within clinical tolerance. There was a significant difference in CT between institutions (P < 0.001). Differences in CV were found between institutions for CT (P = 0.003) and CFT (P = 0.01). Healthy horse RIs were calculated for the overall data set and each individual institution. Calculated RIs were as follows: CT, 255.6-1233.9 seconds; CFT, 89.4-581 seconds; alpha angle, 11.4-53.6°; maximum clot firmness, 18-37.7; lysis index at 30 minutes, 97.3%-102.1%; lysis index at 45 minutes, 80.8%-103.3%; amplitude at 10 minutes, 8.7-28.3; and amplitude at 20 minutes, 17.4-35.7.

CONCLUSIONS

VCM Vet is a repeatable and practical option for rapid point-of-care assessment of hemostasis in horses but has a wide RI and is susceptible to variability. Establishment of institution-specific RIs is recommended.

Reference Range of Kaolin-Activated Thromboelastography (TEG) Values in Healthy Pet Rabbits (Oryctolagus cuniculus)

Thromboelastography (TEG) is a viscoelastic technique that allows the examination of both cellular and plasma protein clotting factors. Thromboelastography helps to investigate the underlying coagulopathy and to monitor therapeutic modalities. Although viscoelastic techniques have been used in human and veterinary medicine, reference ranges in pet rabbits are missing. The objective of this study is to establish the reference-range values of TEG parameters in healthy pet rabbits. 24 healthy pet rabbits of different breeds were included: 16 crossbreeds, four Californians, two lops, one lionhead, and one angora. Four rabbits were less than one year old and 20 were older than one year. Twelve rabbits were neutered females, 10 neutered males, and two were intact females. Health status was assessed through a physical examination, a complete blood work, and a coagulation profile. A TEG 5000 Thromboelastograph Hemostasis System was used with kaolin-activated citrated whole blood. All samples were analysed 30 min postextraction. The TEG reference ranges were reaction time (R) 1.4-6.9 min; clot formation time (K) 0.8-2.2 min; α angle 65.8-82.2 degrees; maximal amplitude (MA) 53.7-73.5 mm; measure of clot strength/firmness (G-value) 5796.6-13,885.9 dyn/cm²; and percentage of clot lysis in 30 min (LY30%) 0-41.5%. This study provides the reference ranges of TEG in pet rabbits.

Point-of-care viscoelastic coagulation assessment in healthy dogs during the perianesthetic period

Background

The viscoelastic coagulation monitor (VCM Vet) is a novel, portable device that provides a global assessment of hemostasis. The study aims were to evaluate serial viscoelastic analysis during the perianesthetic period in healthy dogs and to compare the agreement between two VCM Vet devices. Twenty healthy dogs undergoing orthopedic surgery were enrolled. Whole blood samples were collected from an intravenous catheter at four time points: baseline, 15 min after premedication, 60 min after inhalant initiation, and 60 min after inhalant termination. Viscoelastic tests were performed in duplicate on different devices, providing: clot time (CT; seconds), clot formation time (CFT; seconds), alpha angle (α; degrees), amplitude (units) at 10 (A10) and 20 (A20) minutes post clot time, maximum clot firmness (MCF; units), and lysis index (%) at 30 (Li30) and 45 (Li45) minutes post maximum clot formation.

Results

One hundred sixty samples were analyzed. The speed of CT and CFT significantly decreased an average of 25.5 s (95% confidence interval [CI]15.9–35.0) and 6.9 s (95% CI 3.1–10.7) per time point, respectively. There were no significant changes in clot strength or lysis variables. The Bland–Altman style plot shows an acceptable rate of agreement for all variables with intra-class correlation ranging from 0.64–0.94.

Conclusion

The rate of clot formation (CT and CFT) decreased over the perianesthetic period in healthy dogs undergoing surgery. These changes were small and occurred without changes in clot strength or fibrinolysis rate, thus were not clinically relevant. There was clinically acceptable consistency between devices.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03442-x.

Comparison of assessment of coagulation in healthy dogs by the TEG 6s and TEG 5000 viscoelastic analyzers

The TEG 6s (Haemonetics) point-of-care viscoelastic analyzer is portable, compact, simple to use, and has the potential for rapid viscoelastic analysis that can guide the treatment of veterinary patients at the site of care. Although approved for use in people, the TEG 6s has yet to be evaluated for hemostatic analysis in veterinary medicine. Citrated whole blood (CWB) was collected from 27 healthy dogs. An aliquot of CWB from each dog was diluted by 33% with an isotonic crystalloid, representing an in vitro model of hemodilution. Unaltered and diluted CWB samples were analyzed using 2 TEG 6s and 6 TEG 5000 (Haemonetics) analyzers. The 6 TEG 5000 analyzers ran duplicate analyses of either unaltered or diluted samples using 1 of 3 reagents (Haemonetics): Kaolin TEG, RapidTEG, or TEG Functional Fibrinogen. Duplicate TEG 5000 analyses were averaged and compared with a single TEG 6s analysis. Lin concordance correlation coefficient and Bland-Altman plots were used to evaluate agreement of reaction time, kinetic time, alpha angle, maximum amplitude (MA), and G value (G) for samples activated with Kaolin TEG, and agreement of MA for samples activated with RapidTEG between the 2 machines. Overall, agreement between the TEG 6s and TEG 5000 analyzers was poor. Viscoelastic measurements by the TEG 6s and TEG 5000 in healthy dogs were not all interchangeable. Agreement was satisfactory only for MA and G measurements of diluted blood samples activated with Kaolin TEG, and MA measurements for both unaltered and diluted blood samples activated with RapidTEG.

Evaluation of the Effect of Storage Time on ROTEM S® Parameters in Healthy and Ill Dogs

Viscoelastic testing as a bedside test to assess global haemostasis has gained popularity in the past decade, with rotational thromboelastometry (ROTEM) and thromboelastography (TEG) being the two commonly used devices. TEG studies suggest analysis 30 min after blood sampling. However, the reproducibility of results over time for ROTEM analysis using lyophilized samples in dogs has not been established. In this study, we investigated the influence of time on viscoelastic testing, using 33 healthy staff-/client-owned dogs for blood sampling and repeated measurements of ROTEM tracings at three different time points after blood collection. Additionally, a group of 21 hospitalized patients with suspected coagulation disorders were included to investigate whether stability over time was comparable between healthy and ill dogs. We demonstrated a significant difference of ROTEM tracings over time, with a tendency towards hypocoagulability over time. These changes do have a clinical relevance as they exceed reference intervals and could therefore lead to erroneous conclusions about a patient's coagulation status. Therefore, time-specific reference intervals are proposed and presented in this publication.

Pre-operative Hemostatic Status in Dogs Undergoing Splenectomy for Splenic Masses

Portal system thrombosis is a rare but potentially fatal complication of splenectomy in dogs. The mechanism behind development of post-operative portal system thrombosis is unclear but may include alterations of portal blood flow following surgery, acquired hypercoagulability and endothelial dysfunction. The aim of the study was to evaluate hemostatic biomarkers in hemodynamically stable (heart rate <130 beats/min, blood lactate < 2.5 mMol/L) and non-anemic (hematocrit >35%) dogs prior to splenectomy for splenic masses. Our hypothesis was that this population of stable dogs would have pre-existing laboratory evidence of hypercoagulability unrelated to shock, bleeding, anemia, or other pre-operative comorbidities. Pre-operatively, abdominal ultrasonography was performed and blood was collected for platelet enumeration, prothrombin time (PT), activated partial thromboplastin time (aPTT), kaolin-activated thromboelastography (TEG), fibrinogen, von Willebrand factor activity (vWF:Ag), antithrombin and thrombin-antithrombin complex (TAT). Histopathological diagnosis and 30-day survival were recorded. None of the 15 enrolled dogs had pre-operative sonographic evidence of portal system thrombosis. Three of fifteen dogs were thrombocytopenic, three had thrombocytosis, three were hyperfibrinogenemic, one had low vWF:Ag, three had mild prolongations of PT and none had abnormal aPTT. Based on the TEG G value, 13/15 dogs were hypercoagulable (mean ± SD 13.5 ± 5.4 kd/s). Antithrombin deficiency was identified in 9/15 dogs (mean ± SD 68.7 ± 22.7%) with 5/9 having concurrently elevated TAT suggesting active thrombin generation. No dogs developed portal system thrombosis and all achieved 30-day survival. Pre-operative hypercoagulability was recognized commonly but its association with post-operative thrombosis remains undetermined.

Hemostatic Dysfunction in Dogs Naturally Infected with Angiostrongylus vasorum—A Narrative Review

This narrative review aims to describe Angiostrongylus vasorum-induced hemostatic dysfunction of dogs with emphasis on clinical and laboratory findings as well as potential therapeutic strategies for the bleeding patient. Canine angiostrongylosis (CA) is a disease with potentially high morbidity and mortality in endemic areas and with fatal outcome often associated with either severe respiratory compromise, pulmonary hypertension and right-sided heart failure, or hemostatic dysfunction with severe bleeding. The most common signs of hemorrhage are hematomas, petecchiation, ecchymoses, oral mucosal membrane bleeding and scleral bleeding, while intracranial and pulmonary hemorrhage are among the most severe. The pathophysiological mechanisms underlying hemostatic dysfunction in these patients are presently researched. While the larval effect on platelets remains unknown, the parasite appears to induce dysregulation of hemostatic proteins, with studies suggesting a mixture of pro-coagulant protein consumption and hyperfibrinolysis. Importantly, not all dogs display the same hemostatic abnormalities. Consequently, characterizing the hemostatic state of the individual patient is necessary, but has proven difficult with traditional coagulation tests. Global viscoelastic testing shows promise, but has limited availability in general practice. Treatment of A. vasorum-infected dogs with hemostatic dysfunction relies on anthelmintic treatment as well as therapy directed at the individual dog’s specific hemostatic alterations.

Coagulation Status in Dogs Naturally Infected with Angiostrongylus vasorum

Angiostrongylus vasorum infection has been associated with coagulopathies including hyperfibrinolysis. We compared coagulation status including thromboelastometry (ROTEM) parameters in dogs naturally infected with A. vasorum versus healthy dogs to determine clinicopathological parameters associated with bleeding, hypocoagulopathy, and hyperfibrinolysis. Clinical signs, white blood cell count, platelet count, hematocrit, plasmatic coagulation tests (PT, aPTT, fibrinogen concentration), D-dimer, and ROTEM S parameters (Ex-tem, In-tem, Fib-tem, Ap-tem) were analysed and compared between bleeding, nonbleeding, and control dogs and between hypo- and normocoagulable animals. Clinical signs of bleeding were present in 6/9 (67%) hypocoagulable and 1/9 (11%) normocoagulable dogs. PT, fibrinogen concentration, and several ROTEM parameters were significantly different between hypocoagulable and normocoagulabe A. vasorum infected dogs. Hyperfibrinolysis was identified in 44% of infected dogs and was significantly more common in bleeding and hypocoagulable dogs. Hyperfibrinolysis was significantly associated with low MCFFib-tem but not with low fibrinogen concentration or increased D-dimers. CFTEx-tem > 248 swas 100% sensitive and 89% specific to predict hyperfibrinolysis. Hyperfibrinolysis, hypocoagulability and bleeding are common in A. vasorum infected dogs. Only Ex-tem and Fib-tem parameters and potentially PT were associated with bleeding or hypocoagulability. Ex-tem analysis enables detection of bleeding, hypocoagulability and hyperfibrinolysis within minutes.

Comparison of viscoelastic test results from blood collected near simultaneously from the jugular and saphenous veins in cats

OBJECTIVES

The aim of this study was to compare viscoelastic test results from samples collected from a jugular vein using a 20 G needle and a medial saphenous vein using a 22 G needle in cats presenting for elective ovariohysterectomy (OHE) or castration.

METHODS

Forty apparently healthy cats (20 males and 20 females) presenting for elective OHE or castration were included in a prospective study observing viscoelastic test results from central and peripherally collected whole blood. Cats were anesthetized during blood collection with a standardized protocol including buprenorphine, ketamine, dexmedetomidine and isoflurane. Blood samples from jugular and saphenous veins were collected near simultaneously. Viscoelastic evaluations of whole blood were performed using a point-of-care device measuring clot time (CT), clot formation time (CFT), alpha angle (α), maximum clot formation (MCF), and amplitude at 10 and 20 mins (A10 and A20, respectively). Viscoelastometry continued post-clot time to determine a lysis index at 30 and 45 mins (LI30 and LI45, respectively) to assess fibrinolysis.

RESULTS

Studied cats had a median age of 18 months (range 5 months to 5 years) and a median weight of 3.6 kg (range 2.7-5.9 kg). A total of 80 samples were available for analysis. While lysis indices were not different, viscoelastic measures of coagulation differed between sampling sites (CT, P <0.005; CFT, P = 0.01; α, P <0.05; MCF, P <0.0005; A10, P <0.0005; A20, P <0.0005).

CONCLUSIONS AND RELEVANCE

Viscoelastic results from jugular venous blood samples appear to be more hypercoagulable than those collected from the medial saphenous vein, suggesting that the same site should be used consistently for serial monitoring or for collecting study data.

Thromboelastography in cats with cholestatic liver disease

OBJECTIVES

While thromboelastography (TEG) has helped define a complex state of hemostasis in dogs and humans with hepatobiliary disease, it has not been explored in cats with cholestatic liver disease (CLD). The objective of this study was to describe TEG parameters in cats with CLD and to compare these parameters with conventional plasma-based coagulation tests, white blood cell (WBC) count and biochemical indicators of liver disease grade and severity.

METHODS

Eighteen cats with CLD, defined by a serum bilirubin ⩾3 mg/dl and a greater than two-fold increase in serum alanine aminotransferase (ALT) and/or alkaline phosphatase (ALP) activity, were prospectively enrolled. All cats received vitamin K1 subcutaneously for 24-36 h prior to acquisition of blood for kaolin-activated TEG analysis, prothrombin time (PT) and activated partial thromboplastin time (aPTT). Patient total solids, packed cell volume, platelet count, WBC count, and serum liver enzymes and bilirubin were extracted from the medical record and correlated with coagulation test results.

RESULTS

TEG global clot strength (TEG G) values defined 9/18 (50%), 5/18 (28%) and 4/18 (22%) cats as hypercoagulable, normocoagulable or hypocoagulable, respectively. TEG G was significantly negatively correlated with PT, aPTT and serum ALP activity and positively correlated with total solids. Five cats (5/18, 28%) were hyperfibrinolytic with clot lysis at 60 mins (LY 60) >15.3%. LY 60 was significantly positively correlated with PT.

CONCLUSIONS AND RELEVANCE

By TEG analysis, cholestatic cats replete with vitamin K1 display a variety of coagulation profiles. Indications of synthetic failure (prolonged PT and aPTT) were associated with hypocoagulable and hyperfibrinolytic TEG parameters. High disease activity (serum ALP) was associated with a hypocoagulable state.

Prevalence of Acute Traumatic Coagulopathy in Acutely Traumatized Dogs and Association with Clinical and Laboratory Parameters at Presentation

OBJECTIVE

 The aim of this study was to determine the prevalence of acute traumatic coagulopathy (ATC) and identify associated clinical and laboratory parameters including rotational thromboelastometry.

STUDY DESIGN

 Dogs presenting within 6 hours after trauma were allocated to the ATC or non-ATC group based on thromboelastometry analysis (ex-tem S, in-tem S, fib-tem S). ATC was defined as ≥2 hypocoagulable parameters in 1 profile and ≥ 1 hypocoagulable parameter in an additional profile. Parameters used were ex-tem and in-tem clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), maximum lysis and fib-tem MCF. Clinical and laboratory parameters at presentation, animal trauma triage (ATT) score, transfusion requirement and outcome were compared. Logistic regression was used to identify independent factors associated with ATC.

RESULTS

 Eleven of 33 dogs presented with ATC and showed ex-tem CT and CFT prolongation and reduced MCF amplitude in all profiles (all p < 0.001). pH (p = 0.043) and potassium concentration (p = 0.022) were significantly lower and bleeding (p = 0.027) and plasma transfusions (p = 0.001) more common in dogs with ATC. Time after trauma (p = 0.040) and Animal Trauma Triage score (p = 0.038, including haematocrit as confounding factor) were associated with the presence of ATC.

CONCLUSION

 Acute traumatic coagulopathy is more common in traumatized dogs than previously reported. Acute traumatic coagulopathy was associated with acidosis, Animal trauma triage score, time after trauma and higher transfusion needs. Coagulation abnormalities include ex-tem CT and CFT prolongations and decreased clot strength.

Effects of refrigerated storage on hemostatic stability of four canine plasma products

OBJECTIVE

To assess clotting times, coagulation factor activities, sterility, and thromboelastographic parameters of liquid plasma (LP), thawed fresh frozen plasma (FFP-T), and 2 novel formulations of freeze-dried plasma (FDP) stored refrigerated over 35 days.

SAMPLE

6 units of canine LP and FFP-T from a commercial animal blood bank and 5 units each of 2 formulations of canine FDP.

PROCEDURES

Prothrombin time; activated partial thromboplastin time; activities of coagulation factors II, V, VII, VIII, IX, X, XI, and XII; and thromboelastographic parameters were determined for each product on days 0 (baseline), 3, 7, 14, 21, 28, and 35. For each day, a sample of each product was also submitted for aerobic bacterial culture.

RESULTS

Small changes in coagulation factor activities and mild increased time to initial clot formation in LP and FFP-T were noted over the 35-day storage period. Activities of factor VIII in FDP1 and factor XII in FDP2 were < 50% at baseline but varied throughout. Compared with FFP-T, time to initial clot formation was increased and clot strength was preserved or increased for the FDPs throughout the study. One FDP had decreased pH, compared with other products. No plasma product yielded bacterial growth.

CONCLUSIONS AND CLINICAL RELEVANCE

Liquid plasma and FFP-T would be reasonable to use when stored refrigerated for up to 35 days. Both FDP products showed variability in coagulation factor activities. Studies investigating the usefulness of these plasma products (FDPs) in dogs and the variable days of refrigerated storage (all products) are warranted. (Am J Vet Res 2020;81:964-972).

Serial Evaluation of Haemostasis Following Acute Trauma Using Rotational Thromboelastometry in Dogs

OBJECTIVE

 The aim of this study was to describe the coagulation status of traumatized dogs over the first 24 hours after admission.

STUDY DESIGN

 In 33 dogs presenting within 6 hours after trauma blood was sampled for rotational thromboelastometry (ROTEM), thrombocyte number and venous blood gas analysis at presentation and 6 and 24 hours thereafter. At each time point, dogs were defined as hypo-, normo- or hypercoagulable based on extrinsic, intrinsic and fibrinogen ROTEM profiles.

RESULTS

 Significantly more dogs (11/33) presented hypocoagulable compared with 6 hours (p = 0.046) and 24 hours (p = 0.008) thereafter and none presented hypercoagulable. Significantly more dogs were hypercoagulable (6/23, p = 0.014) and no dog was hypocoagulable at 24 hours compared with presentation. All evaluated ROTEM parameters except maximum lysis were significantly more hypocoagulable at presentation compared with 24 hours thereafter.

CONCLUSION

 Hypocoagulability is more common in acutely traumatized dogs than previously described. Dogs were hypo- or normocoagulable at presentation and the coagulation status changed to normo- or hypercoagulability over the first 24 hours. Clotting times, clot formation and clot firmness but not clot lysis were significantly altered at presentation compared with 24 hours and fibrinogen concentration or function may play an important role in the dynamic change of coagulation state over time.

Lyophilized platelets versus cryopreserved platelets for management of bleeding in thrombocytopenic dogs: A multicenter randomized clinical trial

Background

Thrombocytopenia in dogs is common in critical care medicine, but availability of fresh platelet concentrates in veterinary medicine can be limiting. Lyophilized platelets have long shelf‐lives and can be easily transported, stored, and administered in various settings.

Objective

To evaluate the efficacy and safety of a novel trehalose‐stabilized canine lyophilized platelet product in thrombocytopenic dogs with clinically‐evident bleeding.

Animals

Eighty‐eight dogs with platelet counts <50 × 10³/μL and a standardized bleeding assessment tool (DOGiBAT) score ≥2.

Methods

Multicenter, randomized, non‐blinded, non‐inferiority clinical trial comparing dimethyl sulfoxide (DMSO)‐stabilized cryopreserved platelet concentrates (CPP) with trehalose‐stabilized lyophilized platelets (LP) for control of bleeding in thrombocytopenic dogs. Dogs were randomized to receive 3 × 10⁹ platelets/kg of LP or CPP. Primary outcome measures were change in DOGiBAT score, platelet count, need for additional red cell transfusion and all‐cause mortality.

Results

Fifty dogs received LP and 38 received CPP. Baseline demographics and clinical characteristics of both groups were comparable. At 1‐hour post‐transfusion, LP were superior for change in DOGiBAT score, and non‐inferior at 24‐hours post‐transfusion. The LP were non‐inferior to CPP for change in platelet count, need for additional red blood cell units, and survival to discharge. The LP were superior for change in hematocrit at 1‐hour post‐transfusion, and non‐inferior at 24‐hours. No adverse effects were noted in either group.

Conclusions and Clinical Importance

A novel trehalose‐stabilized canine LP product appears to be logistically superior and is clinically non‐inferior to DMSO‐stabilized canine CPP for management of bleeding in thrombocytopenic dogs.

Effect of packed red blood cell transfusion on thromboelastographic tracings in dogs with naturally occurring anemia

OBJECTIVE

To assess the effect of packed RBC (pRBC) transfusion on thromboelastographic (TEG) tracings in dogs with naturally occurring anemia.

ANIMALS

22 clinically anemic dogs that received a pRBC transfusion.

PROCEDURES

For each dog, a blood sample was collected before and within 3 hours after completion of the pRBC transfusion for a CBC, nonactivated TEG analysis, and measurement of blood viscosity. Wilcoxon signed rank tests were used to compare CBC, viscosity, and TEG variables between pretransfusion and posttransfusion blood samples. Multivariable linear regression was used to assess the effects of pretransfusion-posttransfusion changes in Hct, WBC count, and platelet count on changes in TEG variables.

RESULTS

Median posttransfusion Hct (21%; range, 13% to 34%) was significantly greater than the median pretransfusion Hct (12.5%; range, 7% to 29%). Packed RBC transfusion was associated with a median increase in Hct of 6.2% (range, 1.2% to 13%). Maximum amplitude significantly decreased from 74.9 to 73.8 mm and clot strength significantly decreased from 14,906 to 14,119 dynes/s after pRBC transfusion. Blood viscosity significantly increased, whereas platelet and WBC counts significantly decreased after transfusion. Multivariable linear regression revealed that pretransfusion-posttransfusion changes in Hct, WBC count, and platelet count were not associated with changes in TEG variables.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that pRBC transfusion had only small effects on the TEG tracings of hemodynamically stable dogs. Therefore, large changes in TEG tracings following pRBC transfusion are unlikely to be the result of the transfusion and should be investigated further.

A Novel Microchip Flow Chamber (Total Thrombus Analysis System) to Assess Canine Hemostasis

Hemorrhagic diseases are common in dogs. Current coagulation assays do not model all aspects of in vivo hemostasis and may not predict bleeding risk. The Total-Thrombus Analysis System (T-TAS) is a novel hemostasis assay system in which whole blood flows through microfluidic channels at defined shear rates to provide qualitative and quantitative evaluation of platelet function (PL-chip) and coagulation function (AR-chip). The present study evaluated the T-TAS in dogs with hereditary bleeding disorders and with acquired hemorrhagic syndromes (Group 1), and healthy controls (Group 2). Hereditary defects included von Willebrand's disease (VWD; n = 4), hemophilia A (n = 2), and canine Scott syndrome (n = 2). Acquired hemorrhagic disorders included neoplastic hemoperitoneum (n = 2) and acute hemorrhagic diarrhea syndrome (n = 1). Citrate anticoagulated samples were collected from diseased dogs (Group 1, n = 11) and controls (Group 2, n = 11) for coagulation screening tests, fibrinogen analyses, D-dimer concentration, antithrombin activity, von Willebrand Factor antigen, PFA-100 closure time (PFA-CT), and thromboelastography (TEG). Citrate and hirudin anticoagulated samples were used for T-TAS analyses at two shear rates. Qualitative thrombus formation in each chip was recorded using the T-TAS video camera. Numeric parameters, derived from the instrument software, included occlusion start time (OST; time to 10 kPa), occlusion time (OT; time to 60 kPa (PL-chip) or 80 kPa (AR-chip)), and area under the pressure curve (AUC). Correlations between continuous variables were evaluated by Spearman's rank. Continuous variables were compared between groups by Student's t-test or the Mann-Whitney U-test. Alpha was set at 0.05. In combined analyses of all dogs, significant correlations were identified between T-TAS variables, between the PFA-CT and PL-chip parameters and between TEG variables and AR-chip parameters. The prothrombin time correlated with the AR-chip AUC at both shear rates. In Group 1 dogs, the AR-chip AUC at low shear was significantly reduced compared with Group 2 dogs. Aberrant thrombus formation was seen in video images recorded from dogs with VWD and hemophilia A. The T-TAS AR-chip analysis distinguished dogs with bleeding risk compared to healthy controls. Initial evaluations of the T-TAS suggest it may aid characterization of hemostasis in patients at-risk of bleeding and assist with delineating bleeding phenotypes.

Determination of reference intervals for single vial rotational thromboelastometry (ROTEM) parameters and correlation with plasmatic coagulation times in 49 clinically healthy dogs

The objectives of this prospective study were determination of reference intervals (RI) for rotational thromboelastometry (ROTEM) parameters in single use reagents and to evaluate correlations between plasmatic coagulation times and ROTEM parameters. Blood was sampled from a jugular vein in 49 client-owned healthy dogs and ex-tem S, in-tem S, fib-tem S and ap-tem S parameters, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, haematology, blood chemistry and venous blood gas analysis was performed. Determination of RI was performed using Excel add-in Reference Value Advisor and correlations between PT, aPTT and fibrinogen with selected ROTEM parameters were determined by Spearman correlation. Ex-tem S maximum clot firmness (MCF) RI are smaller compared to RI in people and liquid ex-tem in dogs while maximum lysis was comparable to those in people but smaller than previously reported in dogs. A strong correlation was found between fibrinogen measured by Clauss and fib-tem S and in-tem S MCF (r = 0.541, P < .001 and r = 0.610, P < .001, respectively). PT showed a significant but moderate correlation with ex-tem S CT (r = 0.340, P = .030), in-tem S CFT (r = 0.433, P = .003), fib-tem S CT (r = 0.426, P = .009) and ap-tem S CT (r = 0.354, P = .015) while aPTT was not significantly correlated with any of the evaluated parameters. In conclusion, this study provides single use reagent ROTEM parameter RIs that are different from RI determined with liquid reagents. Significant correlations between fibrinogen concentrations measured by Clauss and clot firmness of fib-tem S and in-tem S profiles and between PT and clotting times of all reagents were identified.

A prospective evaluation of oral Yunnan Baiyao therapy on thromboelastographic parameters in apparently healthy cats

OBJECTIVE

To determine the effect of Yunnan Baiyao (YB) on hemostatic parameters measured by thromboelastography (TEG) in apparently healthy cats administered 1 capsule of YB orally twice daily for 1 week.

DESIGN

Prospective study of client-owned cats at a small animal specialty hospital.

SETTING

One private referral center.

ANIMALS

Twenty client-owned adult cats were prospectively enrolled.

INTERVENTIONS

All cats underwent echocardiographic examination by the same board-certified cardiologist to rule out occult cardiomyopathy. Blood samples were collected for analysis of baseline CBC, fibrinogen, and kaolin-activated TEG values. Cats were administered 1 capsule (250 mg/capsule) of YB twice daily orally for 1 week and the physical examination, CBC, fibrinogen, and TEG were re-evaluated. Any side effects attributed to YB were noted at this time.

MEASUREMENTS AND MAIN RESULTS

Three cats were excluded as 2 cats were identified with underlying cardiomyopathy and another cat had a cystic mass in the cranial mediastinum identified via echocardiography. Seventeen cats were treated with YB; however, 1 cat could not complete the study due to severe vomiting associated with YB administration. The remaining 16 cats completed the study, although 2 additional cats experienced transient vomiting. Yunnan Baiyao administration was associated with a significant decrease in HCT and red blood cell count, although no cat became anemic. None of the TEG parameters significantly changed compared to baseline after 1 week of YB therapy.

CONCLUSIONS

The results of this study suggest YB at a dose of 1 capsule orally twice daily in cats fails to produce any significant change in hemostatic parameters as measured by TEG, although it did significantly reduce HCT and red blood cell count. Yunnan Baiyao was tolerated for most of the cats, although 3 of 17 (17.6%) cats experienced vomiting. Clinicians should be aware of these effects before considering the use of YB in cats.

Correlation of rotational thromboelastometry (ROTEM) parameters with platelet count and their ability to predict thrombocytopenia in dogs

The study objectivs were to evaluate the correlation between platelet count (PLT) and rotational thromboelastometry (ROTEM) parameters and to determine ROTEM cut-off values for identification of thrombocytopenia in dogs. Medical records of 113 dogs with concurrent EXTEM (ROTEM activated by proprietary tissue factor), FIBTEM (EXTEM with added cytochalasin D) analysis and PLT were retrospectively reviewed. Signalment, treatment prior to analysis, hematocrit (HCT), EXTEM/FIBTEM maximum clot firmness (MCF_EXTEM, MCF_FIBTEM), EXTEM/FIBTEM maximum clot elasticity (MCE_EXTEM, MCE_FIBTEM) and EXTEM maximum lysis (ML_EXTEM) were extracted from patient records and ROTEM database. Delta (Δ) MCF was calculated as MCF_EXTEM-MCF_FIBTEM and ΔMCE as MCE_EXTEM-MCE_FIBTEM. The PLT was correlated to MCF_EXTEM, MCE_EXTEM, ΔMCF and ΔMCE using Spearman-Rho analysis. Correlations were further analyzed in thrombocytopenic dogs. The ability to predict thrombocytopenia was evaluated with receiver operating characteristics (ROC). Thirty-seven samples (32.7%) showed thrombocytopenia (<130 × 10⁹/L) and 19 samples (17%) severe thrombocytopenia (<60* x 10⁹/L). The PLT significantly correlated with MCF_EXTEM (r = 0.545, P < .001), MCE_EXTEM (r = 0.547, P < .001), ΔMCF (r = 0.441, P < .001) and ΔMCE (r = 0.559, P < .001). MCF_EXTEM < 49 mm, MCE_EXTEM < 93, ΔMCF <42 mm and ΔMCE <90 predicted thrombocytopenia <60 × 10⁹/L with a sensitivity of 90% and a specificity of 78% with a negative predictive value >97% for all 4 parameters. In conclusion, PLT in dogs correlated moderately but significantly with all evaluated ROTEM parameters. All parameters were able to rule out thrombocytopenia <60 × 10⁹/L with a high negative predictive value, while the sensitivity to predict thrombocytopenia was only moderate and the positive predictive value was low.

The effect of atorvastatin on haemostatic parameters in apparently healthy dogs

OBJECTIVE

To determine the effect of atorvastatin on haemostatic parameters as measured by prothrombin time, activated partial thromboplastin time and thromboelastography in apparently healthy dogs administered 2 mg/kg orally once daily for 1 week.

MATERIALS AND METHODS

Prospective study of 20 apparently healthy client-owned dogs at a small animal specialty hospital. Dogs had a baseline complete blood count, serum chemistry profile, fibrinogen, platelet count, prothrombin time, activated partial thromboplastin time and thromboelastography performed. Each dog was then administered approximately 2 mg/kg of atorvastatin orally once daily for 1 week, and the laboratory tests were repeated. Adverse effects attributed to atorvastatin were recorded.

RESULTS

All 20 enrolled dogs completed the study. Dogs received a median dose of 2.06 mg/kg (range 1.94 to 2.44 mg/kg) atorvastatin once daily, which was associated with a significant increase in pulse rate, mean corpuscular haemoglobin concentration, albumin and a significant decrease in mean corpuscular volume, cholesterol and lipase values compared with baseline. On thromboelastography, there was a significant increase in maximum amplitude, G, coagulation index, amplitude at 30 minutes, amplitude at 60 minutes and significant decrease in percentage of clot lysed at 30 minutes and percentage of clot lysed at 60 minutes values compared with baseline. Six dogs had a noticeable increase in appetite.

CLINICAL SIGNIFICANCE

The results of this study suggest that atorvastatin may produce a procoagulant effect in dogs, although the clinical significance is unclear. Polyphagia was the most commonly reported adverse effect.

A prospective evaluation of rivaroxaban on haemostatic parameters in apparently healthy dogs

The purpose of this study was to determine the effect of rivaroxaban (RIV) on haemostatic parameters assessed by prothrombin time (PT), activated partial thromboplastin time (aPTT) and kaolin‐activated thromboelastography (TEG) in apparently healthy dogs administered 1 mg kg⁻¹ orally once daily for 1 week. Eleven dogs had a baseline complete blood count (CBC), fibrinogen, platelet count, serum chemistry profile, PT, aPTT, and TEG performed. Each dog was then administered approximately 1.0 mg kg⁻¹ of RIV orally once daily for 1 week and the CBC, fibrinogen, platelet count, serum chemistry profile, PT, aPTT, and TEG was re‐evaluated. Any side effects attributed to RIV were noted at this time. One dog was excluded due to identification of a macrocytic thrombocytopenia on pre‐treatment blood work. The remaining 10 enrolled dogs completed the study. Dogs received a median dose of 1.02 mg kg⁻¹ (range 0.94–1.17 mg kg⁻¹) of RIV once daily and was associated with a significant increase in pulse, packed cell volume, total solids, platelet count, fibrinogen and a significant decrease in mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. There was no significant change in PT, aPTT or any TEG parameters. The RIV appeared well tolerated with one dog having one episode of vomiting on day 4 but otherwise no other side effects were identified clinically or on recheck blood work. The results of this study suggests that RIV at a dose of 1 mg kg⁻¹ orally once daily is safe and well tolerated but does not cause a significant prolongation of PT, aPTT or TEG parameters.

In-vitro study of species-specific coagulation differences in animals and humans using rotational thromboelastometry (ROTEM)

Animal tests are conducted in all fields of trauma research, but transferability of these data to humans is limited. For example, it is still unclear which animal species is most similar to humans in terms of physiology of blood coagulation. To improve transferability and raise awareness of the existing differences, we compared human coagulation to coagulation of different animals. Rotational thromboelastometry was used to analyse the blood of pigs, sheep, rabbits and dogs. Animal data were compared with human coagulation based on the number of significant differences of the test parameters and on a descriptive comparison of the extent of relative deviation of the single values. All animal species showed significant differences in coagulation properties when compared with humans. Coagulation parameters of dogs and sheep were on average most similar to humans. However, there is no animal which is most similar to humans concerning all aspects of coagulation. Differences in coagulation between humans and animals are significant. This must be taken into account when transferring animal test data to humans.

Correlation of plasma coagulation tests and fibrinogenClauss with rotational thromboelastometry parameters and prediction of bleeding in dogs

Background

Correlation of plasma fibrinogen concentration (fibrinogen_Clauss) with rotational thromboelastometry (ROTEM) parameters has not been investigated in dogs.

Objectives

To determine the correlation between plasma coagulation tests and fibrinogen_Clauss with ROTEM parameters and to evaluate their ability to predict bleeding in dogs.

Animals

Ninety‐seven dogs with concurrent determination of fibrinogen_Clauss and fibrin polymerization test (FIBTEM) analysis.

Methods

Signalment, pretreatment, clinical signs of bleeding, fibrinogen_Clauss, plasma coagulation test results, hematocrit, platelet count, FIBTEM, extrinsic (EXTEM) and intrinsic (INTEM) activated ROTEM assays were retrieved retrospectively. Correlations between fibrinogen_Clauss and FIBTEM maximum clot firmness (MCF_FIBTEM) and between prothrombin time (PT) or activated partial thromboplastin time (aPTT) and ROTEM parameters were determined. Dogs were further assigned to groups with or without clinical signs of bleeding. The prognostic significance of significantly different parameters to predict bleeding was evaluated.

Results

Fibrinogen_Clauss showed strong correlation with MCF_FIBTEM (r = 0.860, n = 97, P < .001). PT showed strong correlation with EXTEM clotting time (CT_EXTEM) (r = 0.839, n = 53, P < .001), and aPTT was strongly correlated with INTEM CT (CT_INTEM) (r = 0.664, n = 31, P < .001). Platelet count, PT/aPTT, EXTEM clot formation time (CFT_EXTEM), MCF_EXTEM, EXTEM maximum clot elasticity (MCE_EXTEM), and CT_INTEM were significantly different between groups. A CT_INTEM >149 seconds was 100% sensitive to detect bleeding.

Conclusions and Clinical Importance

The MCF_FIBTEM can be used to evaluate the effect of fibrinogen on hemostasis as an alternative to determination of fibrinogen_Clauss. In addition, CT_EXTEM and CT_INTEM are strongly correlated with PT and aPTT, respectively.

A prospective evaluation of oral Yunnan Baiyao therapy on thromboleastographic parameters in apparently healthy dogs

OBJECTIVE

To determine the effect of Yunnan Baiyao (YB) on hemostatic parameters measured by thromboelastography (TEG) in healthy dogs administered 1 capsule of YB orally twice daily for 1 week.

DESIGN

Prospective study of client-owned dogs at a small animal specialty hospital.

SETTING

Private referral center.

ANIMALS

Eighteen client-owned adult dogs weighing at least 15 kg.

INTERVENTIONS

Dogs had a baseline TEG performed and then each dog was administered 1 capsule of YB twice daily by mouth for 1 week and the TEG was reevaluated. Any side effects attributed to YB were noted at this time.

MEASUREMENTS AND MAIN RESULTS

All 18 enrolled dogs completed the study. Dogs that received 1 capsule (250 mg/capsule) of YB orally twice daily had significantly increased G as well as A30 and A60 values. There was also a significantly decreased LY30 and LY60 values after 1 week. The YB appeared well tolerated as only one dog developed mild diarrhea.

CONCLUSIONS

The results of this study suggest that YB at 1 capsule orally twice daily in healthy medium to large breed dogs increases the strength of the clot as measured by TEG and that YB was apparently well tolerated in the study population reported here. Larger prospective studies in different disease states are warranted to further evaluate these preliminary findings.

Retrospective comparison of standard clotting tests and novel clot waveform parameters in dogs using the turbidimetric ACL-TOP CTS 300 coagulation analyzer

Clot waveforms are generated by coagulation analyzers, such as the ACL-TOP, that utilize photo-optical turbidimetric methods to measure prothrombin time (PT) and activated partial thromboplastin time (aPTT), which are standard clotting tests (SCTs). Additional quantitative clot waveform analysis (CWA) parameters include maximum velocity of the PT curve (PT1d), maximum acceleration of the aPTT curve (aPTT2d), and their change in optical density (ODdelta). We explored the potential for CWA to contribute unique information compared to SCTs and quantitative fibrinogen assay (QFA) in dogs with clinical indications for laboratory evaluation of coagulation. We retrospectively evaluated the frequency and agreement between normal, high, and low values of CWA and SCTs for 203 dogs relative to reference intervals (RIs). Most dogs had SCTs within RIs, but most CWA values were high regardless of whether SCT values were within, below, or above the RI. Agreement between SCTs and CWA was slight (kappa <30%). Clinically significant bleeding was noted in 28 of 203 (14%) dogs. SCTs were not different between bleeders and non-bleeders. Median QFA, PT1d, aPTTdelta, and aPTT2d values were statistically significantly higher than RIs in non-bleeders compared to bleeders, whose median values were not below RI. Compared with SCTs, CWA identified differences between the 2 groups. However, wide overlap between the 2 groups limits the use of CWA to clinically discriminate between bleeders and non-bleeders in a heterogeneous population of dogs. Further studies on the diagnostic utility of CWA in coagulopathic dogs are needed.

Characteristics of hemostasis during experimental Ehrlichia canis infection

Background

Ehrlichia canis infection in dogs can cause thrombocytopenia and clinical evidence of bleeding. It is unknown why some dogs show signs of bleeding whereas others do not despite clinically relevant thrombocytopenia.

Hypothesis/Objectives

Activated platelets, decreased fibrinolysis or both mitigate bleeding tendency. Assess standard hemostatic variables, platelet dynamics, and specialized coagulation testing in dogs experimentally infected with E. canis to evaluate this clinical discrepancy.

Animals

Four healthy laboratory beagles.

Methods

Dogs were given blood infected with E. canis IV. Platelet indices of activation, platelet aggregometry, antiplatelet antibodies (percent IgG), complete coagulation panel, and thromboelastography (TEG) were measured before inoculation and on weeks 1‐8. Dogs were treated with doxycycline at approximately 5 mg/kg PO q12h between weeks 3 and 4 (day 24). For each variable, 1‐way repeated measures analysis (1‐way ANOVA) with post‐hoc analysis was performed with statistical significance set at P < .05.

Results

Dogs had significantly lower platelet counts, evidence of activated platelets, and antiplatelet antibodies during E. canis infection. Dogs also appeared hypercoagulable and hypofibrinolytic using TEG as compared with baseline, changes that persisted for variable amounts of time after doxycycline administration. No overt signs of bleeding were noted during the study.

Conclusions and Clinical Importance

Activated platelets and a hypercoagulable, hypofibrinolytic state could explain the lack of a bleeding phenotype in some dogs despite clinically relevant thrombocytopenia. Findings from our pilot study indicate that additional studies are warranted.

The effect of 3 resuscitative fluid therapies on hemostasis as measured by rotational thromboelastometry in dogs

BACKGROUND

Evidence suggests that administration of intravenous fluids impairs hemostasis. Thromboelastometry (TEM) may provide a more sensitive measure of the fluid effects on hemostasis than traditional coagulation tests.

OBJECTIVE

The study aim was to determine if resuscitative fluid therapy affects hemostasis, as measured by TEM.

MATERIALS AND METHODS

Using a randomized crossover design, 6 healthy dogs were administered intravenous colloid, crystalloid, and hypertonic saline at therapeutic doses. Whole blood samples were taken at baseline, 1, 4, and 8 h posttreatment for TEM analysis and measurement of PT, APTT, and fibrinogen. Univariate ANOVA on transformed data evaluated differences between groups and within groups. When significant differences were noted (P = .003), a Tukey test was performed.

RESULTS

A statistically significant interaction between individual dogs and treatment was noted for most TEM variables. There was a significant decrease in clot firmness from baseline in the TEM assessment of the intrinsic pathway. Colloid treatment correlated with significantly higher clot firmness in the TEM extrinsic pathway assessment, which decreased over time, and PT was significantly shorter in colloid-treated dogs. Overall, PT was significantly prolonged at one hour; however, all PT values were within the RI. The fibrinogen concentration was significantly different between all treatments.

CONCLUSIONS

Clinically relevant doses of resuscitative fluids resulted in a decreased clot firmness in the intrinsic pathway, as measured by TEM, which affected hemostatic variables in healthy dogs. There was also a significant individual response to treatment. The changes noted in this study are not expected to result in clinically apparent bleeding.

Plasmatic coagulation and fibrinolysis in healthy and Otostrongylus-affected Northern elephant seals (Mirounga angustirostris)

BACKGROUND

Prepatent Otostrongylus arteritis results in hemorrhagic diathesis in free-ranging Northern elephant seals (Mirounga angustirostris) attributed to aberrant larval migration of the lungworm, Otostrongylus circumlitus. Clinical signs are often nonspecific, including lethargy, anorexia, and blepharospasm, but can progress to spontaneous frank hemorrhage and death within 72 hours of onset. Previously published case reports describe coagulopathy with prolonged PT and APTT, normal to elevated platelet counts, normal antithrombin concentrations, and low concentrations of fibrinogen degradation products. Disseminated intravascular coagulation was proposed as the cause of hemorrhage, but is inconsistent with some of the reported clinicopathologic changes.

OBJECTIVE

The purpose of this study was to compare plasmatic coagulation and fibrinolysis in healthy and Otostrongylus-affected elephant seals, in order to identify potential therapy. We hypothesized that hyperfibrinolysis contributed to hemorrhage in these cases.

METHODS

Citrated plasma samples were collected from 3- to 4-month-old Northern elephant seals in a wildlife rehabilitation hospital. The sampled population included 25 healthy, prerelease seals and 32 clinically ill seals diagnosed with presumptive Otostrongylus arteritis. Twenty-one of the included seals had Otostrongylus infestation confirmed at necropsy. Standard coagulation tests and plasma thromboelastography were performed for a complete assessment of coagulation and fibrinolysis.

RESULTS

Northern elephant seals with definitive Otostrongylus infestation were hypocoagulable and hypofibrinolytic compared to healthy controls.

CONCLUSIONS

Results were most consistent with disseminated intravascular coagulation. Treatment with antifibrinolytic drugs to control hemorrhage may be unrewarding; alternative therapies such as plasma transfusions or coagulation factor concentrates should be investigated.

Effects of Yunnan Baiyao on blood coagulation parameters in beagles measured using kaolin activated thromboelastography and more traditional methods

Yunnan Baiyao is anecdotally widely used in veterinary medicine for its pro-coagulation properties. There are no studies determining its effect on clotting tests. The purpose of this study was to determine the effect of oral Yunnan Baiyao (YB) on hemostasis by measuring coagulation via kaolin activated citrated whole blood thromboelastography (TEG), prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, and d-dimers. The study was a prospective, randomized controlled crossover trial. Eight healthy University of Calgary owned beagles were treated orally with either Yunnan Baiyao or placebo every 12 h for 5 treatments. Blood was collected immediately before treatment, 2 h after the last treatment, and 24 h after the last treatment. TEG analysis was run 30 ± 5 min after blood collection. All other coagulation analyses were sent to a reference laboratory for further analysis. No treatment adverse effects were observed. Oral YB increased R-time significantly within the YB group, but the increase was still within canine reference ranges. No other changes were observed. Oral YB at the dosage and frequency administered in this study did not produce any significant improvement in hemostatic parameters. There is a need for further research and scientific evidence for YB use and dosage.

Thromboelastography in Dogs with Chronic Hepatopathies

BACKGROUND

The coagulation status of dogs with liver disease is difficult to predict using conventional coagulation testing.

HYPOTHESIS/OBJECTIVES

To evaluate thromboelastography (TEG) results and associations with conventional coagulation results and indicators of disease severity and prognosis in dogs with chronic hepatopathies (CH).

ANIMALS

Twenty-one client-owned dogs.

METHODS

Dogs with CH were prospectively (10 dogs) and retrospectively (11 dogs) enrolled from 2008 to 2014. Kaolin-activated TEG was performed and compared with reference intervals by t-tests or Mann-Whitney tests. Correlation coefficients for TEG results and conventional coagulation and clinicopathologic results were determined. Significance was set at P < .05.

RESULTS

Dogs with CH had significant increases in R (5.30 min vs 4.33 min), K (3.77 min vs 2.11 min), and LY30 (4.77% vs 0.68%) and decreased angles (55.3° vs 62.4°). G value defined 9 of 21, 7 of 21, and 5 of 21 dogs as normocoagulable, hypercoagulable, and hypocoagulable, respectively. G and MA were correlated with fibrinogen (r = 0.68, 0.83), prothrombin time (PT; r = -0.51, -0.53), and activated partial thromboplastin time (aPTT; r = -0.50, -0.50). K was correlated with PT (r = 0.75) and protein C activity (r = -0.92). Angle was correlated with aPTT (r = -0.63). Clinical score was correlated with PT (r = 0.60), MA (r = -0.53), and R (r = -0.47). Dogs with hyperfibrinolysis (LY30 > 3.04%; 5 of 21) had significantly higher serum transaminase activities. Dogs with portal hypertension had significantly lower G, MA, and angle and prolonged, K, R, and PT.

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs with CH have variable TEG results. Negative prognostic indicators in CH correlate with hypocoagulable parameters on TEG. Hyperfibrinolysis in dogs with CH is associated with high disease activity.

PHARMACOKINETIC STUDY OF ORAL ε-AMINOCAPROIC ACID IN THE NORTHERN ELEPHANT SEAL (MIROUNGA ANGUSTIROSTRIS)

ε-Aminocaproic acid (EACA) is a lysine analogue antifibrinolytic drug used to treat bleeding disorders in humans and domestic animals. Its use in zoological medicine is rare, and dosage is anecdotal. One possible application of EACA is to treat bleeding associated with prepatent Otostrongylus arteritis in Northern elephant seals ( Mirounga angustirostris ) presenting to wildlife rehabilitation centers. This study used an in vitro model of hyperfibrinolysis and a thromboelastograph-based assay to estimate the therapeutic plasma concentration of EACA in elephant seals (85 μg/ml, 95% confidence interval = 73.8-96.8 μg/ml). A concurrent pharmacokinetic study of orally administered, single-dose EACA found that doses of 75 and 100 mg/kg achieved therapeutic plasma concentrations (>85 μg/ml), but the drug was rapidly eliminated and remained in the therapeutic range for only 0.4 and 1.5 hr, respectively. Models of repeated oral dosing at 100 mg/kg every 6 hr predict that therapeutic plasma concentration will be maintained for 31.7% (7.6 hr) of a 24-hr period. More frequent dosing would be required to maintain continuous therapeutic concentrations but would be impractical in a wildlife rehabilitation setting. Further pharmacodynamic studies to evaluate the duration of action of EACA in elephant seals and a prospective, placebo-controlled study are needed to determine if EACA is effective in decreasing bleeding associated with prepatent Otostrongylus arteritis and other bleeding disorders in this species.

Assessment of hemostatic changes in a model of acute hemorrhage in dogs

OBJECTIVE

To evaluate hemostatic changes following experimental acute hemorrhage in dogs using traditional coagulation tests (eg, platelet count, prothrombin time [PT], and activated partial thromboplastin time [aPTT]), kaolin-activated thromboelastography (TEG), and whole blood multiple electrode impedance platelet aggregometry.

DESIGN

Prospective study.

SETTING

Research laboratory.

ANIMALS

Five Beagles.

INTERVENTIONS

Dogs were anesthetized prior to obtaining blood samples for baseline PCV, total plasma protein (TPP), arterial blood-gas, platelet count, PT, aPTT, TEG, fibrinogen, and aggregometry. Blood was obtained at 4 additional time points, following 20% blood volume loss, 40% blood volume loss, 60 minutes of sustained hypotension, and after autologous blood transfusion. In addition, heart rate and direct arterial blood pressure were measured at each time point.

MEASUREMENTS AND MAIN RESULTS

Significant decreases were noted for PCV (P = 0.048), TPP (P < 0.0001), and arterial blood pressures (P < 0.0001) over time. Platelet count did not change significantly (P = 0.879), but platelet function was decreased following hemorrhage when arachidonic acid (P = 0.004) and ADP (P = 0.008) were used as agonists. The TEG variables R (P = 0.030), MA (P = 0.043), and G (P = 0.037) were significantly, albeit mildly, changed following hemorrhage. Significant prolongations in PT (P < 0.0001) and aPTT (P = 0.041), and decreases in fibrinogen concentration (P = 0.002) were also seen.

CONCLUSION

Platelet dysfunction occurred following hemorrhage in this model, despite a stable platelet count. Additionally, significant changes associated with hemorrhage were documented in aPTT, fibrinogen, and MA. Platelet function testing in dogs with naturally occurring hemorrhage warrants further investigation.

Retrospective comparison of thromboelastography results to postmortem evidence of thrombosis in critically ill dogs: 39 cases (2005-2010)

OBJECTIVE

To determine whether there is an association between thromboelastography (TEG) data and necropsy evidence of thrombosis in a cohort of critically ill dogs.

DESIGN

Retrospective study (2005-2010).

SETTING

University teaching hospital.

ANIMALS

Thirty-nine client-owned critically ill dogs for which TEG was performed within 7 days of complete necropsy.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thrombi were found in 26 (67%) dogs. Spayed females (n = 20) were significantly more likely to have thrombosis (P = 0.0127). No significant association was found between presence of thrombosis and any TEG parameter, the calculated coagulation index, results of coagulation testing, type of vascular access, or clinical diagnosis. D-dimers were significantly higher in dogs with thrombosis (P = 0.0207) and a weak positive correlation was found between D-dimer value and number of sites of thrombosis (ρ = 0.18, P = 0.0045). Dogs with WBC > 16 × 10(3) /μL were more likely to have thrombosis compared to others (odds ratio 5.56, 95% confidence interval 1.2-25.7, P = 0.025).

CONCLUSIONS

This study found no association between any TEG parameter and the presence of thrombosis on postmortem examination.