Effect of experimental endotoxemia on thrombelastography parameters, secondary and tertiary hemostasis in dogs

Background: Thrombelastography (TEG) and indicators of secondary and tertiary hemostasis might be altered in dogs with endotoxemia. Hypothesis: Endotoxemia influences measures of coagulation in dogs. Animals: Ten healthy cross‐bred dogs. Material and Methods: Prospective laboratory study between controls (n = 5) receiving 0.9% saline IV and the study group (n = 5) treated with low‐dose lipopolysaccharide (0.02 mg/kg IV). Physical examination and sampling for measurement of leukocytes, platelets, and coagulation variables were performed at time points 0, 1, 4, and 24 hours. Coagulation variables included kaolin‐activated TEG, 1‐stage prothrombin time (OSPT), activated partial thromboplastin time (aPTT), fibrinogen, factor VIII, antithrombin, protein C, protein S, activated protein C (APC)‐ratio calculated from aPTT with and without presence of APC), and D‐Dimers. Results: Endotoxemia‐induced clinical signs included lethargy (n = 5/5), diarrhea (n = 4/5), emesis (n = 4/5), and abdominal pain (2/5). After 1 hour there was severe leukopenia (2.5 ± 0.7 × 10⁹/L; mean ± SD, P < .0001) and a 2.2‐fold increase in D‐Dimers (0.81 ± 0.64 mg/L, P < .0001). After 4 hours there was hyperthermia (40.3 ± 0.4°C, P < .0001) and increases in OSPT (10.5 ± 2.7 seconds, P < .0001), aPTT (16.7±5.2 seconds, P= 0.002). A significant decrease in fibrinogen (1.5±1.0 g/L, P= 0.001), protein C (31 ± 33%, P <.0001), protein S (63 ± 47%, P < .0001), TEG α (58 ± 19, P= .007), and TEG maximal amplitude (50 ± 19 mm, P= .003) was seen compared with the controls. APC‐ratio rose significantly (2.5 ± 0.2, P < .0001) without exceeding the reference interval (n = 4/5). Conclusion and Clinical Importance: D‐Dimers are the earliest indicator for endotoxemia‐associated coagulation abnormalities followed by decreased protein C concentration. APC‐ratio and TEG were not good screening variables.     

Metabolic changes induced by regular submaximal aerobic exercise in meat-type rabbits

Pannon White growing rabbits (a group of 8) were exposed to treadmill exercise (3-9 m/s, 1.2-1.6 km/day) twice a day for 4 weeks, while additional 8 animals, kept inactive, were assigned as the control group. Weekly, 12 hours after exercise, venous blood was taken for serum metabolite and enzyme activity measurements. Total serum protein, albumin and creatinine levels significantly increased during the second half of the training, as compared to the control group. Triacylglycerol levels in the exercised group as compared to controls, however, were higher only after the first and the fourth weeks of the experiment. Resting non-esterified fatty acid (NEFA) concentration of the trained rabbits was lower at the end of the trial. On the other hand, there were no significant differences, as compared to the respective controls, in serum urea, total and HDL cholesterol levels. At the end of the exercise alkaline phosphatase activity was higher and total lactate dehydrogenase activity was lower in the trained rabbits. Serum alanine aminotransferase, aspartate aminotransferase and gamma-glutamyl transpeptidase activities were not changed, while creatine kinase activity was slightly lower in the trained group. The serum cortisol concentration was not different in the trained and control rabbits.     

Effect of preoperative administration of tepoxalin on hemostasis and hepatic and renal function in dogs

Preemptive analgesia is an important part of surgical management, but some NSAIDs can adversely affect platelet function or renal or hepatic status. Tepoxalin is approved in the United States for control of pain and inflammation associated with arthritis and in Europe for relief of pain caused by musculoskeletal disorders. In this study, no significant effects on indices of hemostasis or renal or hepatic function were detected when a single preoperative oral dose of tepoxalin was administered to young healthy dogs undergoing anesthesia and surgery.     

Changes in platelet function, hemostasis, and prostaglandin expression after treatment with nonsteroidal anti-inflammatory drugs with various cyclooxygenase selectivities in dogs

OBJECTIVE: To determine the effects of nonsteroidal anti-inflammatory drugs of various cyclooxygenase selectivities on hemostasis and prostaglandin expression in dogs. ANIMALS: 8 client-owned dogs with clinical signs of osteoarthritis. PROCEDURES: Dogs received aspirin (5 mg/kg, PO, q 12 h), carprofen (4 mg/kg, PO, q 24 h), deracoxib (2 mg/kg, PO, q 24 h), and meloxicam (0.1 mg/kg, PO, q 24 h) for 10 days each, with an interval of at least 14 days between treatments. On days 0 and 10, blood was collected for platelet aggregation assays, thrombelastography, and measurement of lipopolysaccharide-stimulated prostaglandin E(2), platelet thromboxane B(2) (TXB(2)), and free serum TXB(2) and 6-keto-prostaglandin F (PGF)-1alpha concentrations. RESULTS: Platelet aggregation decreased after treatment with aspirin and carprofen, whereas significant changes from baseline were not detected for the other drugs tested. Thrombelastograms obtained after treatment with carprofen revealed decreased maximum amplitude and alpha-angle, suggesting hypocoagulability. Maximum amplitude and coagulation index increased after treatment with deracoxib. Plasma concentrations of prostaglandin E(2) decreased after treatment with carprofen or deracoxib, and platelet TXB(2) production increased after treatment with aspirin. Serum concentrations of the prostacyclin metabolite 6-keto-PGF-1alpha did not change significantly after treatment with any of the drugs, although the ratio of free TXB(2) to 6-keto-PGF-1alpha decreased slightly after treatment with carprofen and increased slightly after treatment with deracoxib. CONCLUSIONS AND CLINICAL RELEVANCE: At the dosages tested, treatment with meloxicam affected platelet function minimally in dogs with osteoarthritis. Treatment with carprofen decreased clot strength and platelet aggregation. Clot strength was increased after treatment with deracoxib.     

Effects of carprofen, meloxicam and deracoxib on platelet function in dogs

ObjectiveTo determine effects of anti-inflammatory doses of COX-2 selective NSAIDs carprofen, meloxicam, and deracoxib on platelet function in dogs and urine 11-dehydro-thromboxane B2.Study designRandomized, blocked, crossover design with a 14-day washout period.AnimalsHealthy intact female Walker Hounds aged 1–6 years and weighing 20.5–24.2 kg.MethodsDogs were given NSAIDs for 7 days at recommended doses: carprofen (2.2 mg kg^?1, PO, every 12 hours), carprofen (4.4 mg kg^?1, PO, every 24 hours), meloxicam (0.2 mg kg^?1, PO, on the 1st day then 0.1 mg kg^?1, PO, every 24 hours), and deracoxib (2 mg kg^?1, PO, every 24 hours). Collagen/epinephrine and collagen/ADP PFA-100 cartridges were used to evaluate platelet function before and during and every other day after administration of each drug. Urine 11-dehydro-thromboxane B₂ was also measured before and during administration of each drug.ResultsAll NSAIDs significantly prolonged PFA-100 closure times when measured with collagen/epinephrine cartridges, but not with collagen/ADP cartridges. The average duration from drug cessation until return of closure times (collagen/epinephrine cartridges) to baseline values was 11.6, 10.6, 11 and 10.6 days for carprofen (2.2 mg kg^?1 every 12 hours), carprofen (4.4 mg kg^?1 every 24 hours), meloxicam and deracoxib, respectively.Conclusions and clinical relevanceOral administration of some COX-2 selective NSAIDs causes detectable alterations in platelet function in dogs. As in humans, PFA-100 collagen/ADP cartridges do not reliably detect COX-mediated platelet dysfunction in dogs. Individual assessment of platelet function is advised when administering these drugs prior to surgery, particularly in the presence of other risk factors for bleeding.     

Cardiovascular effects of submaximal aerobic training on a treadmill in Standardbred horses, using a standardized exercise test

Seven healthy, unexercised, previously trained, adult Standardbred horses were allotted to 2 groups and trained 78 days on a treadmill set at a 7 degree 30' angle. The groups were trained on different schedules, and the effects of training on heart rate, cardiac output, stroke volume, arteriovenous oxygen difference, systemic blood pressure, and venous lactic acid were determined. Measurements were made at rest, during exercise on the treadmill at rates of 55 m/min, 75 m/min, 100 m/min, and 154 m/min, and at 5 minutes after exercise (standardized exercise test). Heart rate and cardiac output decreased during the training period. Significantly slower heart rates were observed at 55 m/min by day 8, at 100 m/min and 154 m/min by day 36, at 1 minute after exercise by day 57, and at 5 minutes after exercise by day 78 (P less than 0.05). Stroke volume increased with exercise, but not significantly. The arteriovenous oxygen difference increased significantly (P less than 0.05) with each increase in work load. There was no significant increase with training, although an upward trend was recorded. Mean systemic blood pressure did not differ from resting with treadmill rates of 55 m/min, 75 m/min, or 100 m/min. It was greater at 154 m/min, although this was not significant. During exercise, the total peripheral resistance decreased to as little as 30% of its resting value. After exercise, diastolic and mean arterial blood pressures and peripheral resistance increased. Marked increases in blood volume and blood viscosity during exercise were closely related to the decrease in peripheral resistance. There was no significant effect of training on blood pressure. Venous lactic acid concentrations at rest were greater than those of the horses on the treadmill at rates of 55 m/min, 75 m/min, and 100 m/min and at 5 minutes after exercise on days 1, 8, and 15. Subsequently, they were not different from resting values. Differences in the effects of the different training programs could not be detected.     

Effects of propranolol on cardiopulmonary function in the pony during submaximal exercise

Cardiopulmonary responses of four ponies were monitored during standard exercise tests (SET), before and after beta-adrenergic receptor blockade with propranolol. The SET consisted of four 5 min increments of increasing speed from 1.0 to 2.8 m/sec on a treadmill at a 7 degrees incline. Data were collected at rest, throughout the SET and recovery. Administration of propranolol to ponies at rest had no effect on cardiopulmonary function. During the SET, increases in heart rate, mean pulmonary artery flow velocity (an index of cardiac output) and right ventricular dP/dt (an index of myocardial contractility) were progressively attenuated as running speed increased. Body temperature and mean pulmonary artery and right ventricular pressures were significantly elevated over normal. Propranolol treatment had no effect on the responses of mean arterial pressure, haematocrit, haemoglobin, blood lactate and arterial blood gases and pH to the SET. These results suggest that in the pony there is no sympathetic activity to the heart at rest and that during exercise there is pulmonary vasodilation mediated by beta-adrenergic receptors.     

Effects of short-term racing activity on platelet and neutrophil activation in dogs

OBJECTIVE: To determine whether platelets and neutrophils become activated in dogs during short-distance sled-pulling activity. ANIMALS: 18 physically fit adult Siberian Huskies. PROCEDURE: Dogs were allocated into 2 teams (9 dogs/team). Each team ran a course of approximately 6.4 km while pulling a sled that contained 2 people. Blood samples were collected immediately before and within 10 minutes after completion of sled-pulling activity. Blood was aspirated into sterile syringes and immediately transferred to evacuated tubes containing EDTA solution. Platelet activation status was evaluated by determining cell-surface P-selection expression, number of platelet aggregates and platelet microparticles, mean platelet-component (MPC) concentration, and mean platelet-component distribution width (MPCDW) concentration. Neutrophil activation status was evaluated by determining cell-surface CD11/CD18 expression, neutrophil size, and neutrophil granularity. RESULTS: Short-duration strenuous sled-pulling activity was associated with lower MPC concentration, higher MPCDW concentration, and higher cell-surface P-selectin expression after activation with phorbol myristate acetate. An increase in neutrophil CD11/CD18 expression and a decrease in neutrophil granularity were also observed after exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study provide evidence of priming and activation of platelets and activation of neutrophils after strenuous short-duration sled-pulling activity. Additional studies will be needed to determine whether these changes have adverse effects on animal performance or induce tissue injury.     

Effect of a high single subcutaneous dose of unfractionated heparin on platelet function in dogs

The influence of heparin on different tests of platelet function was investigated in 5 healthy dogs receiving subcutaneously 1000 I.E./kg BW of a commercial unfractionated Sodium heparin preparation. Blood samples were collected before and 4 hours after heparin injection. Besides plasma activity of heparin platelet count, capillary bleeding time with two different methods, platelet aggregation according to Breddin and to Born with the inductors ADP, collagen, and thrombin as well as in vitro bleeding time were measured. The activity of heparin four hours after the subcutaneous heparin application was 1.20 +/- 0.11 I.E./ml. Compared to the starting values no significant influence of this heparin level could be demonstrated on platelet count, platelet aggregation according to Born with the inductors ADP and collagen, platelet aggregation according to the Breddin method as well as in vitro bleeding time (p > 0.05). Only one of the two methods used for measuring the capillary bleeding time showed a slight prolongation compared to the starting value (mean = 77 sec) to 88 sec (p < 0.05). The most significant influence was seen on the platelet aggregation induced by 1 I.U./ml thrombin, whereby the aggregation maximum decreased from 92.0% (mean) to 12.2% (p < 0.001). Whereas the latter result has to be interpreted primarily as a consequence of the anti-thrombin effect of heparin, the results of the other tests in summary illustrate the clinical unimportant influence of heparin on platelet function in dogs.     

The effects of clopidogrel and omeprazole on platelet function in normal dogs

Omeprazole is used concurrently with clopidogrel to reduce gastrointestinal adverse effects. In humans, the concurrent use of these two drugs can reduce the antiplatelet efficacy of clopidogrel. Our objective was to determine the effects of omeprazole and clopidogrel on platelet function in healthy dogs. A crossover study utilized turbidimetric aggregometry (ADP and collagen) and the PFA‐100^® with the collagen/ADP cartridge to evaluate platelet function in eight healthy dogs during the administration of clopidogrel (1 mg/kg/24 h p.o.), omeprazole (1 mg/kg/24 h p.o.), and a combination of clopidogrel and omeprazole. Drug metabolite concentrations were also measured. Compared to pretreatment, on Days 3 and 5, with ADP as the agonist, there was a significant decrease in maximum amplitude on aggregometry for both clopidogrel and clopidogrel/omeprazole groups. The following revealed no significant differences between clopidogrel and clopidogrel/omeprazole groups when compared on Days 3 and 5: maximum amplitude on aggregometry with ADP or collagen agonists, and PFA‐100^® closure times. When compared to the clopidogrel group, clopidogrel metabolite concentrations in the clopidogrel/omeprazole group were significantly higher on Days 3 and 5. The concurrent administration of omeprazole and clopidogrel in healthy dogs was associated with an increase in the plasma concentration of an inactive metabolite of clopidogrel, but does not significantly alter the antiplatelet effects of clopidogrel.     

Effects of breed, gender, exercise and white-coat effect on markers of endothelial function in dogs

This study examines how systemic biomarkers of endothelial function and nitric oxide metabolism are affected by exercise in dogs. Furthermore, breed variation and white-coat effect have been tested by sampling three different dog breeds both in their home and in a clinical setting. Short-term exercise increased plasma nitrate and nitrite (NOx) and von Willebrand factor (vWf). There was significant difference between Pointers and the small dog breeds Cairn Terriers and Cavalier King Charles Spaniels in the general plasma levels of vWf and asymmetric dimethylarginine (ADMA). NOx and vWf were significantly higher when the sample was taken in the laboratory cf. at home, whereas ADMA and L-arginine were significantly lower. In conclusion, both short-term exercise and white-coat effect influence several plasma markers of endothelial function depending also on the breed and gender of the dogs. These findings should be considered in future studies concerning endothelial function in dogs.     

Effects of doxycycline, amoxicillin, cephalexin, and enrofloxacin on hemostasis in healthy dogs

OBJECTIVE: To determine the effects of enteral administration of doxycycline, amoxicillin, cephalexin, and enrofloxacin at therapeutic dosages for a typical duration on hemostatic variables in healthy dogs. ANIMALS: 14 Beagles. PROCEDURE: Doxycycline (10 mg/kg, PO, q 12 h), amoxicillin (30 mg/kg, PO, q 12 h), cephalexin (30 mg/kg, PO, q 12 h), and enrofloxacin (20 mg/kg, PO, q 24 h) were administered in random order to 10 healthy dogs at standard therapeutic dosages for 7 days, with a 7-day washout period between subsequent antimicrobials. In addition, 4 Beagles served as control dogs. Variables were evaluated before and after antimicrobial administration; they included platelet count, Hct, 1-stage prothrombin time (PT), activated partial thromboplastin time (PTT), fibrinogen concentration, and platelet function. Platelet function was assessed via buccal mucosal bleeding time, aggregation, and a platelet-function analyzer. RESULTS: Administration of all antimicrobials caused a slight prolongation of 1-stage PT and activated PTT and slight decrease in fibrinogen concentration. Cephalexin caused a significant increase in 1-stage PT and activated PTT, amoxicillin caused a significant increase in activated PTT, and enrofloxacin caused a significant decrease in fibrinogen concentration. Platelet count or function did not differ significantly after administration of any antimicrobial. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of commonly used antimicrobials in healthy dogs resulted in minor secondary hemostatic abnormalities, with no change in platelet count or function. Although these changes were clinically irrelevant in healthy dogs, additional studies of the effects of antimicrobial administration on hemostasis in animals with underlying disease processes are warranted.     

Effect of submaximal exercise on horse homocysteinaemia: possible implications for immune cells

Physical exercise induces a reduction of immune defences and an imbalance of red-ox status. In this study plasma levels of cysteine and homocysteine (Hcy) were determined in horses before and after submaximal treadmill exercise as well as the effect on horse lymphocyte proliferation. The exercise induced a significant increase in plasma Hcy levels, which remained high both after the 20 min recovery period and after 2 h of rest. Moreover, a reduction of lymphocyte responsiveness to the proliferative stimulus induced by Concanavalin A was observed. The effects of different Hcy concentrations on the proliferative capacity of lymphocytes in culture were also tested. The results indicated that 10 microM of this amino acid can reduce the proliferative capacity of resting lymphocytes as well as their responsiveness to mitogen. Moreover, our results suggest that homocysteinaemia could be considered one of the parameters affected by physical exercise in horses and that this amino acid could be implicated in the effects of physical exercise on the immune system.     

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

Objectives – To compare coagulation and platelet function parameters measured using a viscoelastic analyzer in 3 groups: foals presenting to a neonatal intensive care unit with presumed sepsis, normal foals, and adult horses. Design – Preliminary prospective trial. Setting – Veterinary teaching hospital. Animals – Ten clinically healthy foals, 13 clinically healthy adult horses, and 17 foals sequentially admitted for suspected sepsis. Intervention – A single citrated (3.8%) blood sample collected at admission was submitted for coagulation evaluation using a viscoelastic analyzer. Measurements and Main Results – Time to initial clot formation (ACT), clot rate (CR), platelet function, and time to peak parameters were collected from the signature generated with the associated software. Peak clot strength was collected manually from signature tracings. Signalment, presenting complaint, blood culture results, clinical progression, and outcome were collected from the medical record. Kruskal‐Wallis testing was used to determine differences in coagulation parameters between groups, as well as to identify any associations between coagulation variables, foal variables, and outcome. Normal foals were more likely to have increased platelet function (P=0.04) compared with normal adult horses. Prolonged ACT (P=0.004) and decreased CR (P=0.03) were associated with foals with positive blood culture. There was a trend toward prolonged ACT and increased likelihood of death (P=0.06). Conclusions – Healthy foals differ in values measured by the viscoelastic coagulation and platelet function analyzer compared with healthy adult horses. ACT and CR abnormalities were more likely to be observed in foals with positive blood cultures. The viscoelastic coagulation and platelet function analyzer may be useful in identifying early hemostasic and platelet dysfunction in critically ill foals, particularly those that are septic.     

Influence of platelet count,acetylsalicylic acid,von Willebrand's disease,coagulopathies, and haematocrit on results obtained using a platelet function analyser in dogs

The platelet function analyser PFA-100 aspirates blood in vitro from a sample reservoir in disposable test cartridges through a microscopic aperture cut into a biologically active membrane at the end of a capillary. In different cartridges the membrane is coated with collagen and adenosine diphosphate (ADP) or collagen and epinephrine (adrenaline) inducing a platelet plug and closure of the aperture. The closure time and total volume of blood flow through the capillary until closure of its aperture were measured. The correlation between platelet count in samples of thrombocytopenic dogs and results of the collagen/ADP cartridge (closure time: r(S)=-0.579; total volume: r(S)=-0.549) was closer than between platelet count and capillary bleeding time. No significant correlation was observed between platelet count and the results obtained with the collagen/epinephrine cartridge. In addition, a higher sensitivity was obtained for the collagen/ADP cartridge. Injection of acetylsalicylic acid into healthy dogs significantly increased closure time and total volume of both types of cartridges (P<0.01). Two dogs with von Willebrand's disease had abnormal values. In contrast, coagulopathies did not significantly influence the results of the platelet function analyser (P>0.05). Despite adequate sensitivity of measurements using the collagen/ADP cartridge to assess quantitative and qualitative platelet disorders in dogs, the influence of haematocrit (P<0.0001) will limit the clinical application of the analyser.     

Evaluation of platelet function in dogs with cardiac disease using the PFA‐100 platelet function analyzer

Background: Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA‐100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets. Objectives: The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs. Methods: Thirty‐nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty‐eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA‐100 analyzer using collagen/ADP cartridges. Results: Compared with CTs in the control group (mean±SD, 57.6±5.9 seconds; median, 56.5 seconds; reference interval, 48.0–77.0 seconds), dogs with valvular insufficiency (mean±SD, 81.9±26.3 seconds; median, 78.0 seconds; range, 52.5–187 seconds), subaortic stenosis (71.4±16.5 seconds; median, 66.0 seconds; range, 51.5–95.0 seconds), and all dogs with murmurs combined (79.6±24.1 seconds; median, 74.0 seconds; range, 48.0–187 seconds) had significantly prolonged CTs (P<.01). Conclusions: The PFA‐100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.