Thromboelastography in healthy, sick non-septic and septic neonatal foals

Decreased Circulating Red Cell Mass Induced by Intravenous Acepromazine Administration Alters Viscoelastic and Traditional Plasma Coagulation Testing Results in Healthy Horses

Coagulopathy is common in equine critical illness, with its early recognition being crucial for patient management and prognosis. In vitro viscoelastic (VE) hypercoagulability with decreased RCM/PCV has been demonstrated in dogs but not horses. Our objective was to evaluate the effects of acepromazine-induced (0.1 mg/kg IV) decreased RCM on VE and plasma coagulation parameters using a prospective interventional study of eight adult horses. Complete blood count (CBC), fibrinogen, prothrombin time (PT), partial thromboplastin time (PTT), packed cell volume (PCV), total solids (TS), and VCM Vet™ VE testing performed at baseline (T0), 1 h (T1), and 12 h (T2) post acepromazine administration. Splenic volume was determined ultrasonographically. The results were analyzed using one-way repeated measures ANOVA with Tukey's post hoc HSD test to determine the effect of time (sample). PCV decreased 13% points following acepromazine administration from T0 to T1 (p < 0.001), remaining decreased at T2 (p < 0.001). Splenic volume increased from T0 to T1 (p = 0.04) and was not different from baseline at T2. Maximal clot formation (MCF) increased from T0 (p = 0.03). PTT decreased from T0 to T1 and increased at T2 (p = 0.03). No other coagulation parameters were significantly altered. This study demonstrates a non-inflammatory acute model of anemia in horses that impacts VE and plasma-based testing.

Thromboelastography in obese horses with insulin dysregulation compared to healthy controls

BACKGROUND

Both obesity and metabolic syndrome are associated with hypercoagulability in people, increasing the risk of cardiovascular disease and thromboembolic events. Whether hypercoagulability exists in obese, insulin-dysregulated horses is unknown.

HYPOTHESIS/OBJECTIVES

To determine if coagulation profiles differ between healthy horses and those with obesity and insulin dysregulation.

ANIMALS

Fifteen healthy horses (CON) and 15 obese, insulin-dysregulated horses (OBID). Individuals were university or client owned.

METHODS

Case-control study. Obesity was defined as a body condition score (BCS) ≥7.5/9 (modified Henneke scale). Insulin dysregulation status was assessed by an oral sugar test (OST). Kaolin-thromboelastography and traditional coagulation variables were compared between groups. The direction and strength of the association between coagulation variables and BCS and OST results were determined using Spearman's correlation.

RESULTS

Thromboelastography variables MA (OBID: 69.5 ± 4.5 mm; CON: 64.8 ± 4.3 mm; P = .007) and G-value (OBID: 11749 ± 2536 dyn/m2 ; CON: 9319 ± 1650 dyn/m2 ; P = .004) were higher in OBID compared to CON. Positive correlations between MA and BCS (R = 0.45, P = .01) and serum insulin (T0 : R = 0.45, P = .01; T60 : R = 0.39, P = .03), and G-value and BCS (R = 0.46, P = .01), and serum insulin (T0 : R = 0.48, P = .007; T60 : R = 0.43, P = .02; T90 : R = 0.38, P = .04) were present.

CONCLUSIONS AND CLINICAL IMPORTANCE

Obese, insulin-dysregulated horses are hypercoagulable compared to healthy controls.

THE ACUTE-PHASE AND HEMOSTATIC RESPONSE IN DROMEDARY CAMELS ( CAMELUS DROMEDARIUS)

  Acute-phase reactants indicate inflammation and are increasingly used in veterinary medicine to indicate and to monitor progression of disease. Hemostasis and inflammation have interconnected pathophysiologic pathways and influence each other on different levels. This study established observed normal ranges for acute-phase reactants and for coagulation and thromboelastographic (TEG) parameters in 49 dromedary camels ( Camelus dromedarius) and assessed the response to chronic and acute inflammation. Chronically infected animals suffering from lymph abscessation due to Corynebacterium spp. had significantly higher concentrations of the acute-phase reactants haptoglobin ( P < 0.005) and fibrinogen ( P < 0.013) and an increased clot strength characterized by an increase of the TEG parameters MA ( P < 0.039), representing the maximum amplitude of the clot strengths, and G, the global clot strength ( P < 0.022), compared to healthy animals. When the acute-phase and hemostatic responses of 10 males receiving a gonadotropin-releasing hormone vaccine and of 9 males that were surgically castrated over 7 days were studied, haptoglobin proved to be a minor positive acute-phase protein, with moderate levels in healthy animals. It increased significantly after both vaccination and castration and remained elevated 7 days postinsult. The negative reactant iron significantly decreased over the 7-day period after castration, whereas a similar decrease following vaccination lasted less than 3 days. Fibrinogen reacted as a positive, minor reactant, with a significant increase and a peak on days 3-5, with higher values seen after castration. Prothrombin time showed a slight shortening at days 5-7, and the TEG parameters MA and G showed significantly increased values, similar to fibrinogen. The acute-phase protein serum amyloid A showed poor repeatability, suggesting that the assay was not reliable.

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.

Thromboelastometry and Thrombelastography Analysis under Normal Physiological Conditions - Systematic Review

BACKGROUND

Studies investigating thromboelastometry or thrombelastography analyses in a physiological context are scattered and not easy to access.

OBJECTIVE

To systematically retrieve and describe published reports studying healthy subjects and targeting at the correlation of ROTEM® and TEG® measurements with conventional parameters of hemostasis.

METHODS

Systematic Review: Papers were searched in Medline, Scopus and the Science Citation Index database. Reference lists of included studies and of reviews were screened. To be included papers had to report ROTEM or TEG data on healthy subjects. Two reviewers screened papers for inclusion, read full texts of potentially relevant papers, and extracted data of included papers.

RESULTS

Searches identified 1,721 records of which 1,713 were either excluded immediately or after reading the full text. The remaining 8 studies enrolled 632 subjects. The association of conventional parameters of hemostasis with ROTEM and with TEG was investigated in one and two studies, respectively. Overall correlation was limited and ranged from 0.0 to 0.40 (total thrombus generation vs. fibrinogen; clotting time INTEM vs. activated partial thromboplastin time).

CONCLUSIONS

Studies assessing the relationship between thromboelastometry or thromboelastography analyses and conventional parameters of hemostasis in healthy subjects remains scarce, and correlations are limited. Further research is needed to understand the physiology of thromboelastometry and thromboelastography parameters.

Study of acute hemocoagulation changes in a porcine endotoxemic shock model using thrombelastography

Disseminated intravascular coagulation and fibrinolysis have been associated with lipopolysaccharide (LPS)-induced endotoxemic sepsis. It has been well established by point-of-care (POC) thrombelastography (TEG) that pigs have a hemocoagulation pathophysiology that resembles humans. We evaluated the use of TEG during the development of coagulation abnormalities in a porcine model of endotoxemia. After approval by the Animal Welfare Committee, pigs were instrumented to record hemodynamic variables. Ten days after surgical instrumentation, LPS (50 μg/kg) was infused intravenously over a period of 45 minutes in conscious animals. Hemodynamic parameters were recorded before and for 6 hours after LPS infusion was completed. Simultaneously, blood samples were analyzed using TEG to measure reaction time (R), clotting time (K), alpha angle (α), maximum amplitude (MA), coagulation index (CI), percent lysis at 30 minutes, and percent lysis at 60 minutes. LPS induced profound hemodynamic changes associated with the induced endotoxemia. Concomitantly, a progressive consumption coagulopathy characterized by significant increases in R and K and decreases in α, MA, and CI developed. The overall hemocoagulation profile of the 3 nonsurviving animals (27%) was significantly different than that of the survivors. Fibrinolysis was not detected during the 6-hour evaluation period. All stages of clot formation were affected as demonstrated by TEG (increased R and K, decreased α and MA). Our results suggest that TEG is a rapid method for assessing coagulation abnormalities in early stages of endotoxemia in pigs. TEG could have significant clinical applications as a rapid POC method in human patients with sepsis.

Coagulopathies in horses

Although primary coagulopathies are rare in horses, changes in coagulation and fibrinolysis are commonly associated with inflammatory diseases. A clear understanding of the pathophysiology of normal and abnormal hemostasis is required to be able to choose and interpret diagnostic tests evaluating coagulation and fibrinolysis. After diagnosis, treatment of the underlying disease must occur regardless of whether clinical manifestations (excessive bleeding or thrombosis) of the coagulopathy are present or not. Specific treatment may be initiated if there are clinical signs of coagulopathy.

Use of viscoelastic coagulation testing to monitor low molecular weight heparin administration to healthy horses

OBJECTIVES

To evaluate the utility of thromboelastography (TEG) and Sonoclot analyses to monitor the effects of low molecular weight heparin (LMWH) administration to healthy horses.

DESIGN

Randomized crossover study.

SETTING

Large animal veterinary teaching hospital.

ANIMALS

Six adult mixed breed healthy mares.

INTERVENTIONS

LMWH (dalteparin) was administered (50 U/kg subcutaneously) either every 12 or 24 h for 3 consecutive days. Blood samples were collected before LMWH administration and then at selected time points for analysis. Thromboelastography derived R-time (R), K-time (K), angle (ANG), and maximum amplitude (MA), and Sonoclot activated clot time (ACT), clot rate (CR), and platelet function (PF) were measured in whole blood 30 min after sample collection. Change (Δ) and percentage change (%Δ) from baseline of each TEG and Sonoclot variable were subsequently calculated. Anti-factor Xa activity and activated partial thromboplastin time (aPTT) were assayed in harvested plasma. The association between anti-factor Xa activity and TEG and Sonoclot (measured and calculated) variables was assessed by calculating correlation coefficients and multiple regression analysis. The ability of measured and calculated TEG and Sonoclot variables to predict when anti-factor Xa activity fell below suggested thromboprophylactic levels was assessed using receiver operating characteristic curve analysis.

MEASUREMENTS AND MAIN RESULTS

The correlation between aPTT and anti-factor Xa activity was weak (r = 0.343). Changes in TEG and Sonoclot variables following LMWH administration were consistent with hypocoagulation. All measured and calculated TEG variables were significantly correlated with anti-factor Xa activity. Sonoclot ACT, ΔACT, CR, ΔCR, and %ΔCR were also significantly correlated with anti-factor Xa activity. TEG ΔR and %ΔR best predicted anti-factor Xa activity below the suggested thromboprophylactic level.

CONCLUSIONS

Although correlations were modest, serial measurement of TEG variables may be used to monitor LMWH therapy in horses; however, further research is required in sick horses.