Preliminary evaluation of hemostasis in neonatal foals using a viscoelastic coagulation and platelet function analyzer

Effect of experimentally induced endotoxaemia and meloxicam administration on the haemostatic system in donkeys

BACKGROUND

Endotoxaemia is a common condition in equids, frequently accompanied by alterations in haemostasis. Non-steroidal anti-inflammatory drugs, such as meloxicam, have been proven to alleviate some signs of endotoxaemia in donkeys. Neither the haemostatic response to induced endotoxaemia nor the effect of meloxicam in this regard have been described in donkeys.

OBJECTIVES

(a) To characterise the haemostatic changes in response to induced endotoxaemia in healthy donkeys, and (b) to assess the effect of meloxicam in these animals.

STUDY DESIGN

In vivo experiments.

METHODS

Endotoxaemia was induced by LPS (20 ng/kg) infusion in six healthy adult Andalusian donkeys. All animals randomly received either an IV bolus of saline solution (untreated group) or meloxicam (0.6 mg/kg) after LPS infusion (PLI), with a 1-month washout period between trials. Samples were collected at -30, 0, 30, 60, 90, 120, 180 and 360 min PLI for clotting times, antithrombin III, anti-Xa activities, platelet and fibrinogen concentrations; and at -30, 90, 180 and 360 min PLI for viscoelastography (Sonoclot).

RESULTS

LPS caused prothrombotic-specific viscoelastographic changes (short activated clot time and elongated clot rate formation) and lower antithrombin III activities compared with reference range for this species. Prolonged prothrombin times were also seen at late timepoints in the experiment. Meloxicam administration resulted in no significant differences between groups.

MAIN LIMITATIONS

Short sampling duration, only Andalusian donkeys.

CONCLUSIONS

Acute endotoxaemia induced hypercoagulability and initial signs of a consumptive coagulopathy in donkeys. Despite a more prolonged increase in anti-Xa activity, meloxicam did not ameliorate most of these haemostatic changes.

Successful caudal vena cava and pulmonary vein isolation in healthy horses using 3D electro-anatomical mapping and a contact force-guided ablation system

BACKGROUND

Recently, treatment of equine atrial tachycardia by three-dimensional electro-anatomical mapping (3D EAM) and radiofrequency catheter ablation (RFCA) has been described. Myocardial sleeves in the caudal vena cava and pulmonary veins are a potential trigger for initiation and perpetuation of atrial tachycardia and atrial fibrillation in the horse. Isolation of these myocardial sleeves by RFCA may be an effective treatment for these arrhythmias.

OBJECTIVES

To describe the feasibility of 3D EAM and RFCA to isolate caudal vena cava and pulmonary veins in adult horses using 3D mapping and a contact force (CF)-guided ablation system.

STUDY DESIGN

In vivo experiments.

METHODS

3D EAM and RFCA was performed in five horses without cardiovascular disease under general anaesthesia, using the CF-guided system CARTO®3. Point-by-point RFCA aimed for isolation of caudal vena cava and pulmonary veins. Radiofrequency energy was delivered in power-controlled mode with a target power of 45 W, CF between 10 and 15 g and 30 mL/min irrigation rate, until an ablation-index of 450-500 was reached.

RESULTS

In the right atrium, myocardial sleeves of the caudal vena cava were isolated (n = 5). In the left atrium, isolation of ostium II (n = 3), ostium III (n = 1) and ostium I, II and III en bloc (n = 1) was performed. Successful isolation was confirmed by entrance and exit block.

MAIN LIMITATIONS

Horses were euthanised at the end of the procedure, so long term effects such as potential reconnection of isolated veins could not be studied.

CONCLUSIONS

This is the first description of 3D EAM and RFCA with CARTO®3 in horses, thereby showing the technical feasibility and successful caudal vena cava and pulmonary vein isolation. CF measurement allowed monitoring of catheter-tissue contact, resulting in efficient acute lesion creation as confirmed by entrance and exit block. This is a promising treatment for cardiac arrhythmias in horses.

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.

Evaluation and clinical application of platelet function testing in small animal practice

Tests that evaluate many aspects of platelet function have been applied in both human and veterinary medicine for the monitoring of treatment with platelet function inhibitors and for detection of platelet function abnormalities (inherited or acquired). Interspecies variation in the response to various platelet agonists is an important consideration when methods that have been developed for people are applied in other species. At the present time, many of these assays are not readily available in standard veterinary practice. Advanced platelet function testing for veterinary patients is offered at select academic institutions. Discussion with a specialist is recommended when considering the use of these tests, and the relative strengths and limitations of each assay should be considered in the interpretation of test results.

Viscoelastic coagulation testing: technology, applications, and limitations

Use of viscoelastic point-of-care (POC) coagulation instrumentation is relatively new to veterinary medicine. In human medicine, this technology has recently undergone resurgence owing to its capacity to detect hypercoagulability. The lack of sensitive tests for detecting hypercoagulable states, along with our current understanding of in vivo coagulation, highlights the deficiencies of standard coagulation tests, such as prothrombin and partial thromboplastin times, which are performed on platelet-poor plasma. Viscoelastic coagulation analyzers can provide an assessment of global coagulation, from the beginning of clot formation to fibrinolysis, utilizing whole blood. In people, use of this technology has been reported to improve management of hemostasis during surgery and decrease usage of blood products and is being used as a rapid screen for hypercoagulability. In veterinary medicine, clinical use of viscoelastic technology has been reported in dogs, cats, foals, and adult horses. This article will provide an overview of the technology, reagents and assays, applications in human and veterinary medicine, and limitations of the 3 viscoelastic POC analyzers in clinical use.

The equine neonatal intensive care laboratory: point-of-care testing

Rapid evaluation and intervention is a requirement and a characteristic of patient management in neonatal intensive care units, and this applies for equine neonates also. Appropriate interventions are based on solid knowledge of age, maturity, and species-specific differences in reference ranges. Point-of-care (POC) testing devices speedup decision making regarding treatments and interventions. However, there are potential limitations of these devices when applied to age groups and species beyond those they were specifically developed for. This article discusses the age-specific differences in the reference ranges and the potential limitations of POC devices currently used, which may affect delivery of care.

Comparison of viscoelastic coagulation analysis and standard coagulation profiles in critically ill neonatal foals to outcome

OBJECTIVE

To determine if changes in viscoelastic variables are associated with abnormalities observed in the standard coagulation profile and patient outcome in foals with suspected septicemia.

DESIGN

Prospective clinical trial during 2003 and 2004 foal season.

SETTING

Neonatal intensive care unit at a veterinary teaching hospital.

ANIMALS

Thirty critically ill foals <72-hour-old admitted sequentially meeting criteria for systemic inflammatory response associated with infection.

INTERVENTIONS

Hemostatic evaluation, using standard coagulation testing and viscoelastic analysis, was performed at admission, 24 hours following admission, and 48 hours following admission in critically ill foals. Standard coagulation tests included platelet count, prothrombin time, activated partial thromboplastin time, fibrinogen, fibrin(ogen) degradation products, and antithrombin. Data collected from viscoelastic analysis included time to initial clot formation (ACT), clot rate, and platelet function. Signalment, blood culture results, clinicopathologic data, and outcome were collected from medical records. Equality of populations test was used to determine associations between coagulation tests and blood culture status/outcome, as well as between viscoelastic parameters and coagulopathy, blood culture status, and outcome. Logistic regression was used to quantify associations. A significance level of P<0.05 was used.

MEASUREMENTS AND MAIN RESULTS

Foals with decreasing clot rate (CR) over the sample period were more likely to be euthanized or die (P=0.02). Foals with prolonged ACT (P=0.03), and decreased CR at admission (P=0.047), were more commonly coagulopathic. Identification of coagulopathy on admission (P=0.02), or persistence of hemostatic dysfunction 48 hours later (P=0.04), was associated with death.

CONCLUSIONS

Viscoelastic coagulation evaluation could be used in a neonatal intensive care unit setting to further characterize coagulopathy, and identify foals at higher risk for poor outcome.