Sonoclot evaluation of whole blood coagulation in healthy adult dogs.

OBJECTIVE: To establish a standard protocol for analysis of canine whole blood and generate reference intervals for healthy dogs using the Sonoclot analyzer, and to compare Sonoclot values to standard and viscoelastic coagulation tests. DESIGN: Prospective study. SETTING: Veterinary University research facility and teaching hospital. ANIMALS: Twelve healthy random source dogs and 52 healthy dogs from the general veterinary school population. INTERVENTIONS: Blood sampling for viscoelastic coagulation testing. MEASUREMENTS AND MAIN RESULTS: Blood was collected from 12 healthy adult dogs by jugular venipuncture. After a rest period at room temperature of 30, 60, or 120 minutes, 340 µL of citrated blood was added to 20 µL of 0.2 M CaCl(2) in 1 of 2 cuvette types warmed to 37° C. Cuvettes contained a magnetic stir-bar with glass beads (gbACT+) or only a magnetic stir-bar (nonACT). Reference interval samples were collected from 52 healthy adult dogs and analyzed in duplicate. The ACT, CR, and PF were not affected by duration of rest period for either cuvette type. ACT variability was decreased when using gbACT+ cuvettes (P < 0.05). In normal dogs reference intervals (mean ± 2 SD) using gbACT+ cuvettes were: ACT 56.0-154.0 seconds, CR 14.85-46.0, and PF 2.1-4.05. ACT correlated to TEG R-time, K-time, and angle, while CR correlated with all TEG parameters. Fibrinogen correlated with ACT, CR, and PF. Sonoclot did not correlate with other common coagulation tests. CONCLUSIONS: Sonoclot provides viscoelastic evaluation of canine whole blood coagulation and correlated to several TEG parameters and fibrinogen. A standard protocol and reference intervals were established.

Viscoelastic pharmacodynamics after dalteparin administration to healthy dogs.

OBJECTIVE: To evaluate the pharmacodynamic effects of dalteparin in dogs by means of viscoelastic coagulation monitoring with a thromboelastograph and a dynamic viscoelastic coagulometer. ANIMALS: 6 healthy adult mixed-breed dogs. PROCEDURES: Dalteparin (175 U/kg, SC, q 12 h) was administered for 4 days (days 1 through 4). Viscoelastic coagulation monitoring was performed hourly on the first and last days of treatment and included intermittent measurement of anti-activated coagulation factor X activity (AXA). RESULTS: Dalteparin administration resulted in progressive hypocoagulability. On both day 1 and 4, activated clotting time and clot rate for the dynamic viscoelastic coagulometer differed significantly from baseline values, whereas the platelet function parameter did not change on day 1 but did on day 4. The R (reaction time), time from reaction time until the amplitude of the thromboelastography tracing is 20 mm, α-angle, and maximum amplitude differed from baseline values on days 1 and 4, although many thromboelastographic variables were not determined. The AXA was increased from baseline values at 3 and 6 hours after administration of the dalteparin injection on days 1 and 4, and all dogs had AXA values between 0.5 and 1.0 U/mL at 2 and 4 hours after administration. The AXA correlated well with activated clotting time (r = 0.761) and with R (r = 0.810), when values were available. Thromboelastography could not be used to distinguish AXA > 0.7 U/mL. CONCLUSIONS AND CLINICAL RELEVANCE: Viscoelastic coagulation monitoring with strong coagulation activators may be used to monitor treatment with dalteparin in healthy dogs.

Effects of rest temperature, contact activation, and sample technique on canine thrombelastography.

OBJECTIVE: To determine the effects of rest temperature, contact activation (CA), and sample collection technique on thrombelastography (TEG) using canine whole blood. DESIGN: Prospective, experimental study. SETTING: University-based research facility. ANIMALS: Twelve healthy, adult, mixed-breed dogs. INTERVENTIONS: Blood was collected by jugular venipuncture. Tubes containing 3.2% sodium citrate, with and without 75 µg/mL corn trypsin inhibitor (CTI), were filled by vacuum. Samples rested for 30 minutes at 3 temperatures: 37°C, room temperature (RT, 20-22°C), or warmed to 37°C 5 minutes prior to analysis (prewarmed). Samples were analyzed at 37°C. CTI-treated samples were analyzed with and without 1:50,000 tissue factor (TF) as activator. Six dogs were also tested similarly using a needle/syringe collection technique. MEASUREMENT AND MAIN RESULTS: Prewarmed samples exhibited greater MA compared to RT (55.5 ± 7.2 mm vs. 53.5 ± 6.0, P< 0.05), while 37°C samples exhibited a steeper angle (56.7 ± 10.4°C vs. 52.4 ± 8.6°C) and greater MA (55.9 ± 7.5 mm vs. 53.5 ± 6.0 mm) than RT samples (both P< 0.05). CTI-treated samples were hypocoagulable (R time 45 min [7.5-56.8 min], angle 8.2°C [5.1-42.5°C], MA 29.2 ± 9.7 mm, P< 0.001), with TF activation returning all but the angle (42.5 ± 7.6°C) to values similar to citrated samples (angle = 56.7 ± 10.4°C, P = 0.017). Collection using a syringe/needle method revealed a shorter R time for prewarmed samples only (R time 4.7 ± 0.7 min, vs. 5.6 ± 0.8 min for vacuum-collected samples, P = 0.008). CONCLUSIONS: Even in the absence of exogenous activators, CA has an impact on canine TEG results. The effects of rest temperatures and sample collection technique on TEG appear to be minimal.

Potential risks, prognostic indicators, and diagnostic and treatment modalities affecting survival in dogs with presumptive aspiration pneumonia: 125 cases (2005-2008).

OBJECTIVE: To evaluate a clinical population of dogs diagnosed with presumptive aspiration pneumonia (AP) and determine diagnostic and treatment modalities contributing to survival. DESIGN: Retrospective study. SETTING: A university veterinary teaching hospital in an urban setting. ANIMALS: One hundred and twenty-five dogs with presumed AP treated from 2005 to 2008. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Dogs with presumptive AP identified by a review of medical records had an overall survival of 81.6% (102/125). Male large-breed dogs (mean 24.9 kg; 82/125) were overrepresented and were more likely to develop AP in this study population. Recent anesthesia had been performed in 16% (20/125), and vomiting was reported in 64% (80/125). The most common radiographic findings were a predominantly alveolar pattern (187/272, [68.8%] total lung lobes) in the right middle lung lobe (80/115, [69.6%]). A mean of 2 lung lobes were involved radiographically, and the relationship between survival and the number of lung lobes affected was statistically significant (P=0.04). Neutrophilia with a left shift was common with no significant change on consecutive daily evaluations. The mean PaO(2) was 77.7 mm Hg (SD, 17.5 mm Hg) (range, 40.7-100 mm Hg) with a median alveolar-arterial gradient of 41.1 mm Hg (range, 8.1-81.8 mm Hg). In this study population, 37.6% (47/125) of dogs had microbial cultures performed and of these, 76.6% (36/47) were positive for growth; Escherichia coli (38.8%), Mycoplasma spp. (21.3%), Pasturella spp. (19.1%), and Staphylococcus spp. (17%) were the most common isolates in either single or multiagent infections. No treatment modality was statistically associated with increased survival. Colloid therapy was a negative prognostic indicator. CONCLUSIONS: In this study the overall prognosis for AP was good. Patients with only 1 affected lung lobe appeared more likely to survive. Supportive treatment modalities are warranted for the hospitalized patient, although no individual treatment method was found to be clearly superior to others.