Application of thrombelastography/thromboelastometry to veterinary medicine

Standard tests of haemostasis do not predict elevated thromboelastographic maximum amplitude, an index of hypercoagulability, in sick dogs

OBJECTIVES

To compare standard tests of haemostasis in hypercoagulable and normocoagulable sick dogs as identified by thromboelastography.

MATERIALS AND METHODS

We compared prothrombin time, activated partial thromboplastin time, D-dimers, packed red blood cell volume and platelet counts in client-owned sick dogs with hypercoagulable (n = 36) and normocoagulable (n = 35) states as identified by thromboelastography maximum amplitude above or within the established reference interval, respectively.

RESULTS

Seventy-one dogs were included. Thirty-six dogs were hypercoagulable and 35 were normocoagulable on thromboelastography. Using multivariable linear models, prothrombin time, activated partial thromboplastin time and D-dimers were not associated with hypercoagulability. Platelet counts and packed red blood cell volume were significantly associated with hypercoagulability.

CLINICAL SIGNIFICANCE

Prothrombin time, activated partial thromboplastin time and D-dimers were not useful in the identification of hypercoagulability in dogs as defined by thromboelastography.

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.

Thromboelastometry for assessment of hemostasis and disease severity in 42 dogs with naturally-occurring heatstroke

BACKGROUND

Thromboelastometry (TEM) provides a comprehensive overview of the entire coagulation process and has not been evaluated in heatstroke-induced coagulopathies in dogs.

OBJECTIVES

To determine the diagnostic and prognostic utility of TEM in dogs with heatstroke.

ANIMALS

Forty-two client-owned dogs with heatstroke.

METHODS

Prospective observational study. Blood samples for intrinsic and extrinsic TEM (INTEM and EXTEM, respectively) were collected at presentation and every 12 to 24 hours for 48 hours. Coagulation phenotype (hypo-, normo-, or hypercoagulable) was defined based on TEM area under the 1st derivative curve (AUC).

RESULTS

Case fatality rate was 31%. Median TEM variables associated with death (P < .05 for all) included longer INTEM clotting time, lower AUC at presentation and at 12 to 24 hours postpresentation (PP), lower INTEM alpha angle, maximum clot firmness, and maximum lysis (ML) at 12 to 24 hours PP, and lower EXTEM ML at 12 to 24 hours PP. Most dogs were normo-coagulable on presentation (66% and 63% on EXTEM and INTEM, respectively), but hypo-coagulable 12 to 24 PP (63% for both EXTEM and INTEM). A hypo-coagulable INTEM phenotype was more frequent at presentation and 12 to 24 PP among nonsurvivors compared to survivors (55% vs 15% and 100% vs 50%, P = .045 and .026, respectively). AKI was more frequent (P = .015) in dogs with hypo-coagulable INTEM tracings at 12 to 24 hours. Disseminated intravascular coagulation was more frequent (P < .05) in dogs with a hypo-coagulable INTEM phenotype and in nonsurvivors at all timepoints.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypocoagulability, based on INTEM AUC, is predictive of worse prognosis and occurrence of secondary complications.

Assessment of hemostasis in hyperthyroid and euthyroid cats using two viscoelastic assays and platelet aggregometry

BACKGROUND

Hyperthyroidism in humans is associated with a hypercoagulable state and an increased risk of thromboembolism.

OBJECTIVE

To evaluate hemostatic variables in hyperthyroid and euthyroid cats with the hypothesis that hyperthyroid cats will have evidence of altered hemostasis consistent with a potential hypercoagulable state.

ANIMALS

Client-owned hyperthyroid (n = 16) and euthyroid (n = 15) cats over 8 years of age.

METHODS

Prospective observational study. Hyperthyroid and euthyroid cats were enrolled. Rotational thromboelastometry (ROTEM), whole-blood platelet impedance aggregometry (WBPIA) and a point-of-care viscoelastic coagulation monitor (VCM-Vet) were performed immediately after minimally traumatic venipuncture under sedation.

RESULTS

Hyperthyroid cats had significantly higher values for variables as assessed by VCM-Vet: A10 (34 [17-47] vs 25 [17-38], P = .003); A20 (39.5 [23-55] vs 31 [21-45], P = .003); and MCF (41 [24-58] vs 35 [22-49], P = .03). Hyperthyroid cats had significantly different values versus the euthyroid cohort as assessed by different ROTEM channels: increased A10, INTEM (61.5 [39-75] vs 54 [23-66], P = .007) and FIBTEM (18 [10-35] vs 13 [2-27], P = .01); increased A20, INTEM (68 [45-78] vs 61 [30-70], P = .006) and FIBTEM (17 [10-34] vs 11 [2-25], P = .002); increased MCF, EXTEM (72 [65-81] vs 69 [34-78], P = .04), INTEM (70 [45-85] vs 62 [35-71], P = .01) and FIBTEM (18 [13-37] vs 14 [3-27], P = .02); increased alpha angle, EXTEM (80 [68-85] vs 76 [41-84], P = .01); shortened CT, EXTEM (52.5 [29-73] vs 60 [52-92], P = .003) and FIBTEM (52.5 [16-75] vs 65 [53-165], P = .001); and decreased ML, FIBTEM (20 [1-36] vs 33 [19-59], P <.001). No significant differences were found with WBPIA.

CONCLUSIONS AND CLINICAL IMPORTANCE

The hyperthyroid cats in this study had evidence of altered hemostasis as assessed by 2 viscoelastic methodologies, and characterized by increased clot amplitude, firmness, and faster coagulation times vs euthyroid controls.

Comparison of D-dimer concentration and thromboelastography for diagnosis of cerebrovascular accidents in dogs: A retrospective study

BACKGROUND

Cerebrovascular accidents (CVAs) in dogs are diagnosed using magnetic resonance imaging (MRI). This modality is sometimes unavailable, and CVAs can resemble other lesions on MRI. D-dimer concentration and thromboelastography (TEG) are utilized in human medicine in addition to diagnostic imaging to support diagnosis of CVAs, but their use in veterinary patients has not been assessed.

OBJECTIVE

Assess utility of blood D-dimer concentration and TEG in supporting the imaging diagnosis of CVAs in dogs.

ANIMALS

Sixty-eight client-owned dogs with neurologic signs that had brain MRI and D-dimer concentration or TEG performed.

METHODS

Multicenter, retrospective study. The incidence of abnormal D-dimer concentration or TEG was compared between patients with MRI evidence of CVA and a control population. Analysis methods included Fisher's exact test or Chi-squared test for association and comparison of independent proportions.

RESULTS

Neither D-dimer concentration nor TEG was significantly associated with a CVA (P = .38 and .2, respectively). D-dimer testing was performed in a low-risk population and showed low sensitivity (30.8%; 95% confidence interval [CI], 10%-61%) and high specificity (86.4%; 95% CI, 64%-96%) for CVA diagnosis. Thromboelastography was performed in a high-risk population and showed moderate sensitivity (64.3%; 95% CI, 44%-81%) and specificity (66.7%; 95% CI, 24%-94%) for CVA diagnosis. Abnormal D-dimer concentration or TEG were not helpful in differentiating hemorrhagic from ischemic stroke (P = .43 and .41, respectively).

CONCLUSIONS

Although blood D-dimer concentration or TEG alone are not diagnostic of CVAs in dogs, a positive D-dimer result supports additional testing for CVA.

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.

Paired Analysis of D-Dimer and Its Correlated Hemostatic Parameters in 30 Dogs with Neoplasms after Tumorectomy

Previous studies have reported that dogs with neoplasms had elevated D-dimer levels. However, few studies have addressed whether D-dimer could be an indicator of tumor burden. The clinical significance of paired analysis of pre- and post-operation of D-dimer levels in dogs has rarely been described. The present study investigated the values of D-dimer levels and their correlated hemostatic alterations in dogs with surgically removable benign and malignant tumors. This study analyzed 30 clinically healthy and 30 tumor-bearing dogs and evaluated the hemostatic functions including D-dimer, thromboelastography G (TEG G), fibrinogen, activated partial thromboplastin time (aPTT), prothrombin time, and platelet count. The median level of pre-treatment D-dimer was 0.8 µg/mL (range: 0.1–6.3 µg/mL), whereas the control dogs exhibited a median value of 0.1 µg/mL (range: 0.1–0.1 µg/mL, p < 0.0001). After tumorectomy, the median levels of D-dimer (p < 0.0001), fibrinogen (p < 0.0001), TEG G value (p < 0.01), and aPTT (p < 0.05) were significantly lower than those of the pre-treatment samples. However, further studies are needed to clarify the values of other hemostatic evaluations. The study revealed the clinical significance of D-dimer and its correlated hemostatic parameters by paired analysis in dogs with tumors. Though more cases are needed for solid confirmation, these values could be potential tumor biomarkers for dogs.

Point-of-care global coagulation assay parameters in normal dogs and dogs with primary immune-mediated hemolytic anemia

OBJECTIVE

To compare viscoelastic parameters between healthy control dogs and dogs with primary immune-mediated hemolytic anemia (pIMHA) using a new, point-of-care viscoelastic coagulation monitor (VCM).^a DESIGN: Retrospective study from 2017 to 2021.

SETTING

Three regional private referral centers.

ANIMALS

Eighteen client-owned dogs with pIMHA and 33 healthy control dogs. pIMHA dogs were defined based on established criteria.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Medical records of dogs with pIMHA and VCM performed at diagnosis from 2017 to 2021 and apparently healthy control dogs voluntarily enrolled in the blood donor program from 2017 to 2018 were reviewed. For the healthy control dogs, consent was obtained to perform VCM in addition to traditional screening. Compared to healthy control dogs, dogs with pIMHA had mean VCM parameters consistent with hypercoagulability, demonstrated by lower mean (SD) clot formation time (108 s [30] vs 233 s [55]; P < 0.0001), higher mean alpha angle (62 degrees [6] vs 52 degrees [6]; P < 0.0001), higher mean maximum clot formation (49 VCM units [11] vs 32 VCM units [5]; P < 0.0001), higher mean amplitude at 10 minutes (40 VCM units [11] vs 19 VCM units [3]; P < 0.0001), and higher mean amplitude at 20 minutes (47 VCM units [11] vs 25 VCM units [4]; P < 0.0001). pIMHA dogs also had significantly higher median (interquartile range) lysis index at 30 minutes (100% [100-100] vs 98% [90-100]; P < 0.0001). When compared to 3 established normal canine reference intervals, dogs with pIMHA had a significantly higher proportion of VCM variables (48%-57%) consistent with hypercoagulability, and a significant percentage of pIMHA dogs (78%-89%) had VCM tracings consistent with hypercoagulability overall, irrespective of the interval utilized for interpretation.

CONCLUSIONS

This study demonstrates hypercoagulability in dogs with pIMHA when compared to healthy control dogs using VCM. Prospective evaluation is warranted to further characterize these findings as well as to evaluate their clinical impact.

Evaluation of Haemostasis in Dogs Affected by Resectable Malignancy

Dogs with neoplasm are at risk of thrombosis, yet there is no information on the haemostatic alterations that may result from the surgeries performed to remove neoplastic masses. The aim of this study was to observe the characteristics of haemostasis in dogs undergoing surgery to remove a malignancy by means of rotational thromboelastometry and thrombin generation. Haemostasis was assessed immediately before surgery (T0), 24 h after surgery (T1), and two weeks after surgery (T2). Statistically significant differences were found between the thromboelastometric parameters at T0 vs. T1, with increases observed in MCF, the α angle, and G parameters in the ex-TEM and in-TEM profiles. In the thromboelastometric analysis performed after surgery differences were identified between T1 and T2, with a decrease observed in parameters such as CFT, MCF, the α angle, and G. Between T0 and T2, only a significant decrease in CT was detected in the fib-TEM profile. No differences were found in the comparison among the results obtained via thrombin generation. In dogs with resectable malignancies, the surgeries performed to remove cancer affected coagulation, causing a tendency towards hypercoagulability. The interference with coagulation was transient, and 2 weeks after surgery, the thromboelatometric results returned to those obtained before surgery (T0).

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.

Impact of general anesthesia on rotational thromboelastometry (ROTEM) parameters and standard plasmatic coagulation tests in healthy Beagle dogs

OBJECTIVE

To assess the influence of general anesthesia on rotational thromboelastometry (ROTEM) and standard coagulation testing in healthy dogs.

STUDY DESIGN

Prospective experimental study.

ANIMALS

10 healthy Beagle dogs.

METHODS

Dogs were administered methadone (0.2 mg/kg) intramuscularly. Anesthesia was co-induced intravenously 30 min later with midazolam (0.1 mg/kg) and propofol to effect, and maintained with sevoflurane. Crystalloids were administered at 5 ml/kg/h. Blood was sampled by direct venipuncture before induction (T0) and 3.5 h later (T3.5) and ROTEM parameters (ExTEM, InTEM, FibTEM, ApTEM), standard plasmatic coagulation tests (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration), hematology, ionized calcium, triglycerides, pH, lactate and body temperature were compared over time with Students t - test or Wilcoxon matched pairs signed-rank tests.

RESULTS

The following variables dropped significantly between T0 and T3.5: body temperature (p < 0.0001), hematocrit (p < 0.0001), platelet count (p < 0.01), pH (p < 0.01), triglycerides (p < 0.01), fibrinogen concentration (p < 0.01), ExTEM, FibTEM (p < 0.01) and ApTEM (p < 0.05) clotting times. Lactate concentration (p < 0.01), aPTT (p < 0.05) and FibTEM maximum clot firmness increased (p < 0.05). No changes were noted in ionized calcium, PT and InTEM values.

CONCLUSION AND CLINICAL RELEVANCE

General anesthesia with concurrent hemodilution and hypothermia induced significant but clinically irrelevant changes in coagulation variables measured at 37 °Celsius. Blood samples from anaesthetized animals can be used for determination of coagulation status in dogs.

Assessment of hemostasis in dogs with gastric-dilation-volvulus, during resuscitation with hydroxyethyl starch (130/0.4) or hypertonic saline (7.5%)

OBJECTIVE

To compare the impact of an IV bolus of hydroxyethyl starch 130/0.4 (HES) or hypertonic saline 7.5% (HS) on hemostasis in dogs resuscitated for gastric-dilation-volvulus (GDV).

DESIGN

Open-label, parallel-group randomized clinical trial.

ANIMALS

Twenty-three client-owned dogs.

INTERVENTIONS

Dogs affected by GDV and shock were randomly assigned to receive HES at 10 mL/kg or HS at 4 mL/kg every 15 minutes. Blood samples were collected for blood gas analysis, PCV, total plasma protein, albumin, standard coagulation profile, and thromboelastometry (ROTEM) at baseline (T0) and at the end of bolus (T1). To assess the differences between the 2 groups at T1, Student's t-test or Wilcoxon rank-sum test was used. To evaluate the differences between T0 and T1, ANOVA for paired data or Wilcoxon matched-pairs signed-ranks test was used. P < 0.05 was considered significant.

MEASUREMENT AND MAIN RESULTS

Hemostasis was evaluated by means of prothrombin time, activated partial thromboplastin time, fibrinogen, and ROTEM. The study included 13 dogs in the HES group and 10 dogs in the HS group. Differences were found between groups at T1: increase in clotting time (P = 0.018) and decrease in fibrinogen level (P = 0.021) in the HS-treated group. Between T0 and T1, there were differences for the HES group: increase in clot formation time (P = 0.046), decrease in maximum clot firmness (P = 0.002) in ex-TEM profile, and decrease in maximum clot firmness (P = 0.0117) in fib-TEM profile. Between T0 and T1, the following differences were noted for the HS group: increase in clotting time (P = 0.048) and clot formation time (P = 0.0019), decrease in maximum clot firmness (P = 0.031) and α angle (P = 0.036) in ex-TEM profile, decrease in α angle (P = 0.036) in in-TEM profile, and decrease in maximum clot firmness (P = 0.017) in fib-TEM profile.

CONCLUSION

In dogs affected by GDV, HES or HS infusion caused a similar tendency toward hypocoagulability, with few differences between the 2 groups.

Comparison of healthy blood donor Greyhounds and non-Greyhounds using a novel point-of-care viscoelastic coagulometer

OBJECTIVE

To measure and compare viscoelastic coagulation in 2 canine blood donor populations using a novel, point-of-care device (VCM Vet Analyzer, VCM).

DESIGN

Cohort study.

SETTING

Academic and commercial veterinary blood banks.

ANIMALS

Non-Greyhounds from community-based blood donor program and Greyhounds from a blood bank colony.

INTERVENTION

Blood was collected from all dogs via direct venipuncture for a complete hemogram, biochemistry, and point-of-care viscoelastic coagulation.

MEASUREMENT AND MAIN RESULTS

All biochemical measurements for all dogs in Group NG (n = 38, non-Greyhounds) and Group G (n = 53, Greyhounds) were within local reference intervals. Hematology data showed significant statistical differences between groups in hemoglobin, RBC, platelet, and WBC concentrations. Group G demonstrated lower maximum clot firmness (MCF) with 17 VCM units (26 VCM units in Group NG), increased lysis with 30 VCM units at 30 minutes (LI30) and 27 VCM units at 45 minutes (LI45) (86 VCM units LI30 and 85 VCM units LI45 in Group NG), and decreased amplitude of 13 VCM units 10 minutes (A10) after clot time (CT) and 6 VCM units 20 minutes after CT (A20) (18 VCM units [A10] and 22 VCM units [A20] in Group NG).

CONCLUSION

This study found differences between healthy Greyhound and non-Greyhound blood donors in measures of clot strength and fibrinolysis as measured by the VCM. Whereas Greyhound have unique hematologic and hemostatic profiles, these measured viscoelastic differences are important to note prior to and following surgical intervention to aid in clinical decision-making if bleeding complications develop.

Changes in the coagulation parameters in dogs with protein-losing enteropathy between before and after treatment

Protein-losing enteropathy (PLE) is known to induce hypercoagulability and resultant thromboembolism in dogs. We hypothesized that hypercoagulability would improve if remission was obtained in dogs with PLE after treatment. This study aimed to evaluate the changes in the coagulation parameters after treatment in dogs diagnosed with PLE. As coagulation parameters, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, thrombin-antithrombin complex (TAT), D-dimer, and antithrombin (AT) were measured. In addition to these parameters, rotational thromboelastometry (ROTEM), which evaluates the comprehensive coagulation and fibrinolysis reactions of whole blood, was conducted and the data of clotting time (CT), clot formation time (CFT), α angle (α), maximum clot firmness (MCF) and lysis index at 60 min (LI60) were obtained. Eleven of the 14 dogs diagnosed with PLE were classified as responders to the treatment based on the changes in their plasma albumin (ALB) concentration after treatment. Significant increase in CFT and decrease of α and MCF indicating the resolution of hypercoagulability were found after treatment in responder dogs; however, there was no significant change in the coagulation and fibrinolysis parameters other than those measured by ROTEM. This study demonstrated that the hypercoagulability detected by ROTEM was significantly improved after treatment in dogs with PLE.

Thromboelastometry assessment of mycophenolate mofetil effect on thrombotic risk in dogs with primary and secondary immune-mediated hemolytic anemia and by Erhlichia canis infection

ABSTRACT This study aimed to identify, by means of thromboelastometry assessment, altered thrombotic risk in dogs with primary and secondary IMHA by E. canis infection after initiating the immunosuppressive therapy with mycophenolate mofetil. The animals’ screening was based on complete blood count (CBC), biochemical and urine tests. Dogs with moderate to severe anemia (hematocrit ≤ 25%) which showed symptoms of immune-mediated hemolysis, such as spherocytosis, positive saline agglutination, bilirubinuria and/or hemoglobinuria, were included. Blood and urine samples were collected at two different moments. The first sample (M1) was collected at the time of diagnosis, when hematocrit was lower or equal to 25% before treatment with mycophenolate mofetil (Accord ®); the second sample (M2) was collected after treatment with mycophenolate mofetil, when hematocrit was greater or equal to 30%. Five out of the twelve animals selected died before the end of the study. No reduction in thrombotic risk was observed in the animals treated with mycophenolate mofetil. The animals that presented hypocoagulation at the time of diagnosis showed the worst prognosis, and their reticulocyte count displayed a better prognostic value than their erythrocytes count at the time of diagnosis.

Effects of storage time and temperature on thromboelastographic analysis in dogs and horses

BACKGROUND

The accessibility of thromboelastography (TEG) to general practitioners is limited by short sample storage times (30 minutes) and storage temperatures (20-23°C).

OBJECTIVES

We aimed to evaluate the stability of canine and equine citrated blood samples when stored for extended periods of time, both at room temperature (RT) (20-23°C) and refrigerator temperature (FT) (2-7.5°C).

METHODS

Citrated whole blood samples from healthy dogs and horses (n = 10 for each) were stored for 30 minutes (baseline) at RT before TEG analysis. Baseline values for TEG variables R, K, α, MA, LY30, and LY60 were compared with those from samples stored for 2, 8, and 22.5 h, at RT and FT. Results were compared using an ANOVA (P < .05). Total allowable analytical error (TE_a ) based on biological variation data was used to evaluate stability.

RESULTS

In dogs, statistically significant differences included shorter R, longer K, decreased MA, and increased LY60 at various time points and storage temperatures from 2 h onward. Only samples stored for 2 h at FT showed acceptable stability compared with TE_a . In horses, statistically significant differences included shorter R and K, and decreased α, LY30, and LY60 at various time points and storage temperatures from 2 h onward. Samples were not stable at any time compared with TE_a , regardless of the temperature.

CONCLUSIONS

In this study, canine samples could be stored for up to 2 h at FT without affecting TEG results; equine samples should be stored for 30 minutes at RT.

Analysis of blood clotting with the total thrombus analysis system in healthy dogs

To date, coagulation tests are unable to reflect in vivo coagulation status in the same system, including platelet function, fibrin clot formation, and whole blood flow. The Total Thrombus Analysis System (T-TAS), which is a microfluidic assay that simulates conditions in vivo, measures whole blood flow at defined shear rates under conditions designed to assess platelet function (PL-chip) or coagulation and fibrin clot formation (AR-chip). The T-TAS records occlusion start time, occlusion time, and area under the curve. We evaluated this test in healthy control dogs. We also investigated the effect in vivo of acetylsalicylic acid (ASA), and the effect in vitro of an anticoagulation drug (dalteparin; low-molecular-weight heparin; LMWH). The CV of the AUC of both chips was good (CVs of 6.45% [PL] and 1.57% [AR]). The inhibition of platelet function by ASA was evident in the right-shift in the PL test pressure curve. The right-shift in the AR test pressure curves showed that the administration of LMWH inhibited both platelets and the coagulation cascade. The T-TAS may be useful in the evaluation of canine blood coagulation.

Establishment of a reference interval for a novel viscoelastic coagulometer and comparison with thromboelastography in healthy cats

BACKGROUND

Viscoelastic analysis provides information on the dynamics and strength of clot formation as well as clot stability. A novel point-of-care viscoelastic test (Viscoelastic Coagulation Monitor Vet, VCM Vet) could be more cost-effective, simpler to use, and more portable than thromboelastography (TEG).

OBJECTIVES

The primary aim of this study was to establish a feline reference interval (RI) for the VCM Vet. A secondary aim was to compare VCM Vet analysis with TEG in healthy cats.

METHODS

Fifty-six healthy cats were enrolled in this study. Linear regression was completed to determine whether age and CBC parameters were associated with the VCM Vet parameters and if TEG parameters were correlated with VCM Vet data. Statistical significance was set at P < .05.

RESULTS

Fifty-three VCM Vet tracings were used to determine RIs for healthy cats. The determined RIs were: clot time (CT) 104-438 seconds; clot formation time (CFT) 104.5-488 seconds; alpha angle (AA) 30.5°-70°; a10 13.8-32.7 VCM units; a20 19.2-40.1 VCM units; maximum clot formation (MCF) 22.5-44.8 VCM units; Lysis Index 30 (Li30) 92.9%-100.9%; and Lysis Index 45 (Li45) 92%-100%. Linear regression identified a strong positive correlation between the CT and R-time measured using the VCM Vet and TEG methods, respectively; no other parameters were correlated.

CONCLUSIONS

The use of VCM Vet is feasible in cats, and we determined the first described feline RIs for this test. In general, the VCM Vet data did not correlate with TEG in healthy cats.

Echis coloratus envenomation in a dog: clinical, hemostatic and thromboelastometric findings and treatment

CONTEXT

Echis coloratus is endemic to the Middle East. Clinical reports describing E. coloratus envenomation in humans are scarce, while natural envenomations of animals were not reported. Such envenomations may induce systemic coagulopathy. This report describes a confirmed E. coloratus envenomation in a dog, with assessment of the global hemostasis by thromboelastometry.

CASE DETAILS

A 6-year old Belgian Shepherd dog was presented in shock, mucosal bleeding and swelling due to snakebite. Laboratory tests showed prolonged prothrombin and activated partial thromboplastin times. Because Daboia palaestinae is the most common venomous snake in Israel, immunoglobulin-G monovalent D. palaestinae antivenom was administered, with supportive care. The dog improved clinically, was discharged, and was readmitted, with active bleeding from the bite site. The dead snake was only then identified as E. coloratus. Thromboelastometry demonstrated severe hypocoagulability. The dog was treated with polyvalent antivenom directed against venoms of several Middle Eastern snakes, fresh-frozen plasma and packed red blood cells. Bleeding completely ceased, and thromboelastometry results improved. The dog was discharged. 3 days later, all hemostatic test results had normalized.

DISCUSSION

Thromboelastometry is useful for assessing the hemostatic status in E. coloratus envenomation, and for monitoring and managing the venom-induced coagulopathy, and guide plasma and polyvalent antivenom treatment.

Canine Protein Losing Enteropathies and Systemic Complications

Canine protein-losing enteropathies occur commonly in small animal practice, and their management is often challenging with a long-term survival rate of only about 50%. Recent studies have investigated prognostic factors that may determine outcome in individual cases. In particular, systemic complications such as hypercoagulability, vitamin D3 deficiency, and tryptophan deficiency may play an important role and should be investigated in severely affected cases in order to maximize outcome.

Postoperative thrombocytosis and thromboelastographic evidence of hypercoagulability in dogs undergoing splenectomy for splenic masses

OBJECTIVE

To determine the frequency and severity of thrombocytosis and thromboelastographic evidence of hypercoagulability during the first 2 weeks after splenectomy in dogs with splenic masses and to investigate relationships between platelet counts and thromboelastography values.

ANIMALS

34 dogs undergoing splenectomy for splenic masses.

PROCEDURES

Blood samples for platelet counts and thromboelastography were obtained at induction of anesthesia (day 0) prior to splenectomy and on days 2, 7, and 14.

RESULTS

Mean platelet counts were 167.9 × 10³/μL, 260.4 × 10³ μ/L, 715.9 × 10³/μL, and 582.2 × 10³/μL on days 0, 2, 7, and 14, respectively, and were significantly higher at all postoperative assessment points than on day 0. Thrombocytosis was observed in 3% (1/34), 6% (2/33), 81% (21/26), and 69% (18/26) of dogs on days 0, 2, 7, and 14. Platelet counts > 1,000 × 10³/μL were observed in 1 dog on day 2 and in 5 dogs on day 7. One or more thromboelastography values suggestive of hypercoagulability were observed in 45% (15/33), 84% (26/31), 89% (24/27), and 84% (21/25) of dogs on days 0, 2, 7, and 14. At each assessment point, higher platelet counts were correlated with thromboelastography values suggestive of hypercoagulability.

CONCLUSIONS AND CLINICAL RELEVANCE

Marked thrombocytosis and thromboelastography values suggestive of hypercoagulability were common during the first 2 weeks after splenectomy for the dogs of this study. If present, hypercoagulability could increase the risk for development of postsplenectomy thrombotic conditions such as portal system thrombosis and pulmonary thromboembolism.

Efficacy of specific antivenom and fresh frozen plasma in reversing Daboia palaestinae venom-induced hemostatic derangement

OBJECTIVES

To evaluate the in vitro efficacy of specific Daboia (Vipera) palaestinae (Dp) antivenom or fresh frozen plasma (FFP) against Dp venom-induced hemostatic changes DESIGN: In vitro study.

SETTING

Laboratory of a university referral hospital.

ANIMALS

Five healthy dogs.

INTERVENTIONS

Rotational thromboelastometry (including recombinant tissue factor or kaolin activators [EXTEM and INTEM, respectively]) and conventional hemostatic tests were evaluated in citrated whole blood samples that underwent 4 treatments: (1) no additives (control); (2) 15 μg of Dp venom; (3) 15 μg of Dp venom and 10 μL of specific Dp antivenom; (4) 15 μg of Dp venom and 0.3 mL of FFP. A linear mixed-effects regression model was used to compare results between each treatment and the control.

MEASUREMENTS AND MAIN RESULTS

Dp-venom engendered statistically significant (P < 0.05) EXTEM changes in 8/17 variables, all indicative of hypercoagulability, which were negated by antivenom but not with FFP. Similarly, Dp-venom induced hypercoagulable, hyperfibrinolytic changes in 12 of 17 INTEM variables, of which only 5 of 12 were negated by antivenom but not with FFP. Fibrinogen concentration was decreased, and the activated partial thromboplastin time (aPTT) was shortened (P < 0.05 for both) in all treatments compared to the control.

CONCLUSIONS

This study demonstrated the ephemeral procoagulant phase of Dp envenomation for the first time. Many venom-induced thromboelastometric changes were reversed by specific antivenom but not with FFP. Prospective clinical studies are warranted to investigate whether the present findings translate to clinical efficacy.

Emerging chitin nanogels/rectorite nanocomposites for safe and effective hemorrhage control

Excessive bleeding due to trauma, surgery and diseases may cause severe mortalities. Here, an emerging chitin nanogel/rectorite nanocomposite is developed for effective hemorrhage control. Chitin chains are intercalated into rectorite and subsequent mechanical high speed stirring generates chitin nanogels, which assemble on the surface of the rectorite nanoplates through electrostatic interactions to form a sandwich structure. The in vitro experiments reveal that the nanocomposite exhibits favorable biocompatibility and negligible hemolysis (<3.5%) as compared to rectorite (40%). The nanocomposite stops bleeding in 121 s in rat tail incision and exhibits higher hemostatic activity in the rabbit artery injury model as compared to a commercialized chitosan hemostat, Celox. The efficient blood clotting activity is attributed to the induction of a coagulation cascade by rectorite and the quick adsorption and aggregation of platelets and red blood cells by chitin. The enhanced biocompatibility and hemostatic activity of the chitin/rectorite nanocomposite make it a safe and cost effective hemostat to control bleeding.

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.

Thromboelastography testing in mice following blood collection from facial vein and cardiac puncture

: Blood collection is critical for mouse research studies particularly in hemostatic testing. Cardiac puncture; a standard effective method requires anesthesia and is a terminal procedure while facial vein technique allows multiple collections. Thromboelastography (TEG) is a global hemostasis test, provides a dynamic real-time picture of coagulation. However, TEG experiments in mice require large number of animals and may not allow pre/postinterventions assessment. In this study, we aimed to investigate the feasibility of facial vein sampling for TEG analysis as an alternative to cardiac puncture and examined the impact on coagulation results. Blood samples were obtained from a total of 10 C57BL/6 and CD-1 mice via cardiac puncture and a total of another eight mice of similar strains via facial vein sampling. We compared TEG parameters in both methods using descriptive statistics and the Student t test. Results show no significant difference in any of the TEG parameters between cardiac and facial vein blood indicating the two methods are comparable. Facial vein sampling provides a less costly alternative to cardiac puncture. It is a suitable blood collection method for pre/postinterventions or follow-up studies and it better addresses reduction and refinement goals in mouse studies. A larger study to evaluate the sex or strain and genetic background differences will be valuable.

Reference intervals for rotational thromboelastometry measurements using the ROTEM® delta device in dogs

Aims of the present study were to define reference intervals for viscoelastic analyses of canine haemostasis using the ROTEM® delta analyser, and as a secondary aspect to determine the precision (repeatability) of this method. Blood samples from 125 clinically healthy dogs were included. Measurements were performed with commercially available activating reagents (ex-tem, in-tem and kaolin solution) as well as without activation. Additional fourfold measurements were done in 3 of the normal blood samples and in 3 samples with haemostatic alterations to evaluate the precision of the method. Coefficients of variation (CVs) for most of the ROTEM variables were < 10%. Clot formation time and maximum clot elasticity showed a wide inter-individual variation in comparison with alpha angle and maximum clot firmness. A multivariate analysis on various ROTEM parameters revealed particularly a significant influence of neuter status and a significant interrelationship between the factors sex and neuter status for measurements with different activating reagents. These results reflected the fact that significant differences occurred only between intact and neutered females, but not in males. No or only occasionally significant differences were found between groups of sex, age, and size. In conclusion, CVs demonstrated that the method delivers repeatable results in canine citrated whole blood. Established reference intervals should deliver valuable orientation for the evaluation of viscoelastic properties of clotting whole blood in dogs using the ROTEM delta analyser. Neuter status in females appeared to be the most relevant influencing factor and should be considered for the interpretation of ROTEM delta test results.

Coagulation parameters in hyperthyroid cats before and after radioiodine treatment compared with healthy controls

OBJECTIVES

The aim of the study was to describe the coagulatory state of hyperthyroid cats before and after successful radioiodine therapy (RIT) compared with healthy age-matched controls, using classical coagulation parameters and thromboelastogram (TEG) as a global assessment method. The differences in coagulation activity after RIT, depending on the thyroid hormone (normal vs low total thyroxine [T4]) state, were also evaluated.

METHODS

Fifteen hyperthyroid cats and 10 healthy age-matched controls were recruited. Hyperthyroid cats that remained hyperthyroid 14 days after RIT were excluded. Haematology, biochemistry, T4, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and TEG were assessed in control cats and hyperthyroid cats before and 7 and 14 days after RIT. Two weeks after successful RIT, further comparisons were made between cats with normal T4 vs those with low T4.

RESULTS

Fourteen days after successful RIT, 7/15 cats had normal T4 and 8/15 had low T4. Thrombocytosis was noted in 6/15 cats after treatment. Fibrinogen was significantly higher (P <0.001) and PT shorter (P <0.01) in the hyperthyroid cats compared with the healthy controls and these changes persisted after RIT. Persistent increases in fibrinogen, PT, TEG maximal amplitude and TEG clot rigidity, reflecting clot stability, after RIT primarily occurred in the cats with normal T4. TEG-K (time until preset amplitude of 20 mm is reached) and alpha (α) angle reflected impaired fibrin cross-linking ability prior to RIT, which significantly increased after therapy (P <0.05).

CONCLUSIONS AND RELEVANCE

Based on some of the coagulation parameters, cats with hyperthyroidism showed hypercoagulable tendencies, which were mildly increased after RIT, possibly due to transient radiation-induced thyroiditis.

Hemostatic function in Cavalier King Charles Spaniels assessed using thromboelastography

BACKGROUND

Macrothrombocytopenia is a well-known anomaly in Cavalier King Charles Spaniels (CKCSs), a breed also highly predisposed to develop myxomatous mitral valve disease (MMVD). Thromboelastography (TEG) has been shown to be a valuable instrument for whole blood hemostatic evaluation in dogs and correlates well with different physiologic and pathologic situations.

OBJECTIVES

We aimed to assess the influence of macrothrombocytopenia and the severity of MMVD on hemostatic function as measured by TEG.

METHODS

Associations between TEG variables (R, K, α, MA, and G) and dog characteristics, heart rates, systolic blood pressures, MMVD severities (healthy, mild or moderate, and severe), echocardiographic variables, platelet variables (platelet count, mean platelet volume [MPV], and plateletcrit), and hematocrits were evaluated in 47 prospectively recruited privately owned CKCSs. Blood samples were analyzed using a computerized thromboelastograph and an Advia 2120 hematology analyzer.

RESULTS

Univariable and multiple regression analyses showed an effect of left ventricular (LV) fractional shortening (FS%) on all TEG variables, an effect of LV FS% and age on TEG α, and an effect of LV FS% and MPV on TEG MA and TEG G. TEG MA and G increased with increasing MPV, but the associations were generally weak. No significant differences were detected in the TEG variables between the MMVD severity groups.

CONCLUSION

Macrothrombocytopenia and increased LV FS%, of which the latter commonly increases in various positive inotropic states, were both associated with a more hypercoagulable hemostatic system, according to the TEG results, in the present study.

A review of hyperfibrinolysis in cats and dogs

The fibrinolytic system is activated concurrently with coagulation; it regulates haemostasis and prevents thrombosis by restricting clot formation to the area of vascular injury and dismantling the clot as healing occurs. Dysregulation of the fibrinolytic system, which results in hyperfibrinolysis, may manifest as clinically important haemorrhage. Hyperfibrinolysis occurs in cats and dogs secondary to a variety of congenital and acquired disorders. Acquired disorders associated with hyperfibrinolysis, such as trauma, cavitary effusions, liver disease and Angiostrongylus vasorum infection, are commonly encountered in primary care practice. In addition, delayed haemorrhage reported in greyhounds following trauma and routine surgical procedures has been attributed to a hyperfibrinolytic disorder, although this has yet to be characterised. The diagnosis of hyperfibrinolysis is challenging and, until recently, has relied on techniques that are not readily available outside referral hospitals. With the recent development of point-of-care viscoelastic techniques, assessment of fibrinolysis is now possible in referral practice. This will provide the opportunity to target haemorrhage due to hyperfibrinolysis with antifibrinolytic drugs and thereby reduce associated morbidity and mortality. The fibrinolytic system and the conditions associated with increased fibrinolytic activity in cats and dogs are the focus of this review article. In addition, laboratory and point-of-care techniques for assessing hyperfibrinolysis and antifibrinolytic treatment for patients with haemorrhage are reviewed.

D-Dimer Concentrations and Thromboelastography in Five Dogs With Ischemic Stroke

Ischemic stroke is a condition increasingly recognized in dogs; however, the number of publications on dogs with ischemic stroke is still limited and hemostatic parameters are infrequently reported. D-dimer levels have been shown to be elevated in people with acute ischemic stroke compared to a healthy control population and it has been proposed that a normal D-dimer can be used to exclude thromboembolism in dogs. In this case series, we report hemostatic parameters, including D-dimer and thromboelastography (TEG) along with clinical and imaging findings for five dogs diagnosed with ischemic stroke. All dogs had a normal D-dimer concentration on presentation. A hypercoagulable state was identified in two dogs based on the results of the TEG, and was suspected in the remaining three cases based on a shortened TEG clot reaction time. Based on the findings in the present cases, a D-dimer within the normal reference range does not seem an appropriate negative predictor for canine ischemic stroke. The demonstration of a possible hypercoagulable state, as identified by the TEG, is an interesting finding which should be explored further to help reveal predisposing hypercoagulable conditions in dogs with ischemic stroke.

Perfusion of Porcine Kidneys With Macromolecular Heparin Reduces Early Ischemia Reperfusion Injury

BACKGROUND

Previously, we have been able to demonstrate the possibility of coating the inner surface of the renal arteries in porcine kidneys with a heparin conjugate during hypothermic machine perfusion (HMP). The purpose of this study was to assess the efficacy of this treatment in reducing early ischemia-reperfusion injury.

METHOD

Brain death was induced in male landrace pigs by stepwise volume expansion of an epidural balloon catheter until negative cerebral perfusion pressure (CPP) was obtained. Both kidneys (matched pairs; n = 6 + 6) were preserved for 20 hours by HMP during which 50 mg heparin conjugate was added to one of the HMP systems (treated group). A customized ex vivo normothermic oxygenated perfusion (NP) system with added exogenous creatinine was used to evaluate early kidney function. Blood, urine and histological samples were collected during the subsequent 3 hours of NP.

RESULTS

Kidney weight was lower at the end of NP (P = 0.017) in the treated group compared with control kidneys. The rate of decline in creatinine level was faster (P = 0.024), total urinary volume was higher (P = 0.031), and the level of urine neutrophil gelatinase-associated lipocalin (NGAL) was lower (P = 0.031) in the treated group. Histologically, less tubular changes were seen (P = 0.046). During NP intrarenal resistance remained lower (P < 0.0001) in the treated group.

CONCLUSIONS

Perfusion of porcine kidneys with heparin conjugate during HMP reduces preservation injury and improves organ function shortly after reperfusion. No increased risk of bleeding was seen in this setup. This protective strategy may potentially improve the quality of transplanted kidneys in the clinical setting.

Multicenter investigation of hemostatic dysfunction in 15 dogs with acute pancreatitis

OBJECTIVE

To characterize hemostatic profiles in dogs with acute pancreatitis.

DESIGN

Prospective and observational study.

SETTING

Tertiary referral centers.

ANIMALS

Fifteen client-owned dogs with acute pancreatitis enrolled between December 1, 2011 and June 1, 2012.

MATERIALS AND METHODS

Blood samples were collected on admission for measurement of platelet count, PCV, thromboelastography (TEG), antithrombin, prothrombin time, activated partial thromboplastin time, D-dimer, von Willebrand factor, and fibrinogen values, which were compared to reference intervals derived from healthy dogs. The Wilcoxon rank-sum test was used to test for differences in continuous variables between study subjects and reference intervals.

MEASUREMENTS AND MAIN RESULTS

Dogs with acute pancreatitis were globally hypercoagulable using TEG when compared with reference intervals. Dogs with acute pancreatitis had significantly higher D-dimers (1,144 μg/L vs 251 μg/L [6264.5 vs 1374.5 nmol/L]; P = 0.001), fibrinogen (837 vs 232 mg/dL [8.37 vs 2.32 g/L]; P < 0.001), and von Willebrand factor (92.9% vs 65.1%; P = 0.02) as well as significantly lower antithrombin (85.7% vs 120%; P < 0.001) and prothrombin time values (3.8 vs 7.6 sec; P < 0.001) than reference intervals.

CONCLUSIONS

Laboratory evidence of hypercoagulability was present in dogs with acute pancreatitis. TEG may be useful in dogs with acute pancreatitis for monitoring response to therapy and guiding therapeutic interventions.

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.

Thrombin-antithrombin complex measurement using a point-of-care testing device for diagnosis of disseminated intravascular coagulation in dogs

Reference interval for thrombin-antithrombin complex (TAT) level was determined using an in-house TAT measurement device, and its validity for diagnosis of disseminated intravascular coagulation (DIC) was evaluated in dogs. One hundred and two clinically healthy dogs and 247 diseased dogs with conditions that potentially caused DIC were recruited in the study. Six diagnostic testing for DIC were evaluated in diseased dogs and the diseased dogs were categorized into five groups depending on abnormal findings. TAT was measured in all study animals and between-group differences were evaluated. TAT level was positively associated with severity of DIC. There were no significant differences in TAT levels among clinically healthy dogs, diseased dogs without any abnormal finding and diseased dogs with one abnormal finding in the DIC diagnostic testing. TAT levels in groups with two or more abnormal findings were significantly higher than clinically healthy dogs. Reference interval of TAT level for clinically healthy dogs was ≤ 0.25 ng/ml. Validity of using TAT for early detection of DIC was evaluated. In-house TAT measurement was suggested to be a clinically relevant and useful tool for early detection of canine DIC.

Viscoelasticity and structure of blood clots generated in-vitro by rheometry: A comparison between human, horse, rat, and camel

BACKGROUND

Although the coagulation system is evolutionary well preserved, profound species differences exist in viscoelastic as well as in common laboratory tests of coagulation.

OBJECTIVE

Evaluating differences in clot formation and material characterisation of clots of four mammalian species on macro-, micro- and nanoscales by the means of rheometry, scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS).

METHODS

Blood samples were collected from healthy human volunteers, laboratory rats (HL/LE inbred strain), warmblood horses and dromedary camels. Clot formation was observed by oscillating shear rheometry until plateau formation of the shear storage modulus G', at which point selected clots were prepared for scanning electron microscopy. SEM images were analysed for fibre diameter and fractal dimension. Additionally, scattering profiles for plasma and whole blood samples were obtained with SAXS.

RESULTS

Viscoelasticity of clots showed great interspecies variation: clots of rats and horses exhibited shorter clotting times and higher G' plateau values, when compared to human clots. Camel clots showed unique clotting characteristics with no G' plateau formation in the timeframe observed. Less differentiating features were found with SEM and SAXS, although the rat fibre network appears to be more convoluted and dense, which resulted in a higher fractal dimension.

CONCLUSION

Clotting kinetic differs between the species, which is not only of clinical interest, but could also be an important finding for animal models of blood coagulation.

Thromboelastography in wild Florida manatees (Trichechus manatus latirostris)

BACKGROUND

Thromboelastography (TEG) provides a comprehensive evaluation of blood clot formation. This test can be used to identify abnormalities in coagulation by assessing multiple aspects of the clotting cascade, including the speed of clot initiation and formation, clot strength, and ultimately fibrinolysis. Thromboembolic disease has been hypothesized to play a role in the pathophysiology of cold stress syndrome (CSS), an important cause of mortality in the threatened Florida manatee (Trichechus manatus latirostris).

OBJECTIVES

The objective of this study was to establish thromboelastography RIs using the TEG 5000 with citrated whole blood samples and kaolin activation in wild, healthy manatees.

METHODS

In December 2014 and January 2015, 29 wild manatees (17 male and 12 female) were blood sampled as part of the annual wild manatee health assessments organized by United States Geological Survey (USGS). TEG was performed using citrated kaolin-activated samples.

RESULTS

The samples were obtained from manatees caught in Crystal River, Citrus County, and used to identify the mean ± SD of normal TEG parameters: R = reaction time 2.1 minutes (0.8), K = clot formation time 0.8 min (0), α angle = 83.1° (2), MA = maximum amplitude 75 mm (7.6), and LY30 = clot lysis 0.41% (0.68). No significant differences were found between manatee size, sex, or time between sampling and running the test.

CONCLUSIONS

Manatee TEG parameters demonstrate a relatively hypercoagulable condition when compared to other mammals. This information will facilitate detection of changes in hemostasis during injury and disease and provide a valuable reference range.

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.

Thromboelastometric assessment of hemostasis following hydroxyethyl starch (130/0.4) administration as a constant rate infusion in hypoalbuminemic dogs

BACKGROUND

The primary aim was to evaluate by means of thromboelastometry (ROTEM) the effects of hydroxyethyl starch (HES) 130/0.4 administered as a constant rate infusion (CRI) on hemostasis in hypoalbuminemic dogs. The second aim was to use ROTEM analysis to detect whether all hypoalbuminemic dogs of our population were hypercoagulable.

RESULTS

The study sample was 20 hypoalbuminemic dogs (albumin < 2 g/dl) with normal perfusion parameters and requiring intravenous fluid therapy. In order to support plasma colloid osmotic pressure, in addition to crystalloid, HES 130/0.4 was administered as a constant rate infusion at 1 ml/kg/h (group 1, n = 11) or 2 ml/kg/h for 24 h (group 2, n = 9). Blood samples were collected at baseline (T0) and 24 h postinfusion (T1); coagulation was assessed by standard coagulation profile (prothrombin time, activated partial thromboplastin time, and fibrinogen), and ROTEM analysis (in-TEM®, ex-TEM® and fib- TEM® profile). No statistically significant differences in ROTEM values in group 1 were observed (P > 0.05), whereas in group 2 statistically significant differences (P < 0.05) were found at T1 in the in-TEM® profile [decrease in clot formation time (P = 0.04) and increase in α angle (P = 0.02)] and in the ex-TEM® profile [increase in maximum clot firmness (P = 0.008) and α angle (P = 0.01)]; no changes were identified in the fib-TEM® profile. In both groups, a statistically significant decrease (P = 0.007) in hematocrit was noted, whereas no statistically significant differences in platelet count and standard coagulation profile were found. In group 2, a statistically significant increase in TS values (P = 0.03) was noted at T1. ROTEM tracings indicating a hypercoagulable state were observed in 7/20 dogs at T0 (5/11 in group 1 and 2/9 in the group 2).

CONCLUSION

Our findings suggest that HES 130/0.4 administered as CRI does not cause hypocoagulability in hypoalbuminemic dogs. A trend toward hypercoagulability, probably related to the underlying diseases, was observed in group 2 at T1. Although all dogs were hyoalbuminemic, only 7/20 were hypercoagulable at T0, confirming the lack of correlation between albumin level and prothrombotic state.

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.

Operator-based variability of equine thromboelastography

OBJECTIVE

To determine the extent of intraoperator (between duplicate samples) and interoperator (between different operators) variability in equine thromboelastography (TEG).

DESIGN

Kaolin-activated TEG was performed in duplicate by operator-pair A/B or A/C (2 groups of 10 horses) using discrete setups, within 30-45 minutes of vacuum-assisted blood collection. Recorded TEG variables included clot initiation time (R), clot formation time (K), rate of clot formation (α), clot strength (MA), and viscoelastic/shear strength (G). Operators independently determined the clinical coagulation status for each sample. Intra- and interoperator variabilities were reported as coefficients of variation (CV), using descriptive statistics and paired samples t-test or Wilcoxon matched pair signed-rank test (P < 0.05 considered significant).

ANIMALS

Twenty hospitalized adult horses with no clinical evidence of systemic inflammation.

MEASUREMENTS AND MAIN RESULTS

Mean intraoperator CVs ranged from 2.6 to 14% (operator A), 2.8 to 13% (operator B) and 1.2 to 18% (operator C). Both intra- and interoperator variabilities were lowest for MA (1.2-3.2%) and G (2.9-7.3%), and highest for K (13-23%). Mean CVs for all TEG parameters were lower when comparing intra- to interoperator variation. Seventy percent of horses had at least 1 TEG variable (out of 4 replicates) outside the established reference intervals. Assessment of coagulation status was conserved between operators in 9/10 and 8/10 horses for A/B and A/C, respectively, with comparable agreement between operator A/B (к = 0.73) and A/C (к = 0.74).

CONCLUSIONS

TEG measurements of MA and G are more reproducible than assessment of K, within samples and between operators. The highest test variability was thus observed within the early phase of clot formation.

Global hemostasis in healthy bitches during pregnancy and at different estrous cycle stages: Evaluation of routine hemostatic tests and thromboelastometry

This study assessed the global hemostasis (including prothrombin time [PT], activated partial thromboplastin time [aPTT], antithrombin activity [ATA], fibrinogen and d-Dimer concentrations, platelet count, plateletcrit and thromboelastometry) in healthy pregnant bitches, comparing the results with those of healthy bitches at different estrous cycle stages, and assessed whether hemostatic changes during pregnancy are associated with serum progesterone concentration or the presence of fetuses in utero. The results show that pregnant bitches have higher fibrinogen concentration, platelet count and platelatecrit, and that fibrin and global clot formations occur faster than in non-pregnant bitches at different estrous cycle stages. Additionally, clot strength was higher in pregnant bitches than in non-pregnant ones. There were no differences in PT, ATA, and D-dimer concentration between all study groups. The aPTT was significantly shorter in bitches at the fourth and last pregnancy weeks, compared to the anestrus group, and shorter in both the fourth and last pregnancy weeks groups, compared to diestrus group. These results all support a hypercoagulable state in healthy pregnant bitches, unassociated with progesterone concentration.

Thromboelastometric assessment of hemostasis in newborn Piemontese calves

We investigated possible age-related differences in coagulation profiles in bovine species by means of rotational thromboelastometric (ROTEM) analysis. We evaluated hemostasis by ROTEM in newborn Piemontese calves at birth (T0), 8 d (T8), and 15 d (T15) of age and compared the ROTEM results obtained in 16 newborn calves with 28 adult Piemontese cattle. Hemostasis was evaluated using standard coagulation tests and ROTEM analysis, obtaining in-TEM, ex-TEM, and fib-TEM profiles. Statistically significant differences in the ROTEM profiles of newborn calves were found between T0 and T8 and between T0 and T15 ( p < 0.05) but not between T8 and T15. Differences between ROTEM profiles of calves and adults were statistically significant at T0 ( p < 0.05) but no differences were found at T15 ( p < 0.05). Hence, ROTEM reference intervals for adult cattle can be used to evaluate profiles in Piemontese calves ≥8 d of age.

Synthetic polyphosphate inhibits endogenous coagulation and platelet aggregation in vitro

Platelet-derived polyphosphate has previously been indicated to induce coagulation. However, industrially synthesized polyphosphate has been found to have different effects from those of the platelet-derived form. The present study investigated whether synthetic sodium polyphosphate inhibits coagulation using routine coagulation tests and thromboelastography. Synthetic polyphosphate was found to inhibit adenosine diphosphate-, epinephrine-, arachidonic acid-, ristocetin-, thrombin-, oxytocin- and pituitrin-induced platelet aggregation. The effects of synthetic polyphosphate in clotting inhibition were revealed by the analysis of clotting factor activity and platelet aggregation tests. Synthetic polyphosphate may inhibit platelet aggregation by reducing platelet calcium levels, as indicated by the results of flow cytometric analysis and high-throughput fluorescent screening. Furthermore, analysis of thromboxane (TX)B2 by ELISA indicated that synthetic polyphosphate reduces platelet aggregation by inhibiting the TXA2 signaling pathway. In conclusion, synthetic polyphosphate inhibits clotting factor activity and endogenous coagulation by reducing the levels of calcium ions and TXA2 to curb platelet aggregation.