Brett S. Tennent-Brown

Multicenter case-control study of signalment, diagnostic features, and outcome associated with cervical vertebral malformation-malarticulation in horses

OBJECTIVE To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM. DESIGN Retrospective case-control study. ANIMALS 270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007. PROCEDURES Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM. RESULTS Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresented in the CVM group. Gait asymmetry and cervical hyperesthesia were frequently detected in horses with CVM. Vertebral canal stenosis and articular process osteophytosis were commonly observed at necropsy; agreement between the results of radiographic or myelographic analysis and detection of lesions at necropsy was 65% to 71% and 67% to 78%, respectively. Of 263 horses with CVM for which outcome was recorded, 1 died and 172 (65.4%) were euthanatized. CONCLUSIONS AND CLINICAL RELEVANCE Odds of a diagnosis of CVM were greater in young horses and horses of specific breeds. Detection of gait asymmetry and cervical hyperesthesia were frequently reported in association with CVM. Accurate diagnosis of lesions associated with CVM by use of radiography and myelography can be challenging.

Liver lobe torsion in six horses

CASE DESCRIPTION 6 horses were determined to have torsion of a liver lobe at 4 referral institutions over a 21-year period. CLINICAL FINDINGS Clinical findings were nonspecific but often included signs of marked inflammation. Two of the 6 horses were examined because of colic, and 2 were assessed because of peritonitis that failed to respond to treatment; the remaining 2 horses were examined because of nonspecific clinical signs that included inappetence, lethargy, and weight loss. The results of laboratory tests were widely variable, and values for liver enzyme activities were typically within reference limits or only mildly increased. Most affected horses had markedly increased peritoneal nucleated cell counts. TREATMENT AND OUTCOME Exploratory laparotomy and resection of the affected liver lobe was performed in 5 horses. Three of those patients survived to discharge. CLINICAL RELEVANCE Results suggested that diagnosis of liver lobe torsion in horses may be difficult because clinical signs and results of laboratory testing are nonspecific and variable. Most affected horses had markedly abnormal peritoneal fluid. The prognosis for hepatic lobe torsion can be good, and early surgical correction is expected to improve outcome.

Pharmacodynamics of Multi-Dose Low Molecular Weight Heparin in Healthy Horses

OBJECTIVES To compare the pharmacodynamics of once daily and twice daily administration of low molecular weight heparin (LMWH) administration in horses. STUDY DESIGN Randomized cross over study. ANIMALS Adult mixed breed healthy mares (n = 6). METHODS LMWH (dalteparin) was administered (50 U/kg subcutaneously) either every 12 or 24 hours for 3 consecutive days. Anti-factor Xa activity was measured before and at select time points after LMWH administration. Packed cell volume (PCV), platelet count, partial thromboplastin time (PTT), and anti-thrombin (AT) activity were monitored throughout the study. RESULTS No changes in PCV, platelet count, or AT activity were detected with either frequency of daily LMWH administration. Values for PTT increased throughout the study but never exceeded the normal reference interval. Anti-factor Xa activity was maintained within or above the suggested thromboprophylactic range (0.1-0.2 U/mL) when LMWH was administered twice daily, but fell below this range ≈ 16 hours after administration when given once daily. For both once and twice daily LMWH administration, the area under the curve was significantly greater after the last dose of LMWH when compared to the first dose. CONCLUSIONS Administration of LMWH once or twice daily for 3 consecutive days appears to be safe in healthy adult horses. Anti-factor Xa activity was maintained within or above the suggested thromboprophylactic range for 24 hours with twice daily LMWH administration but not with once daily administration.

Effects of radial extracorporeal shock wave therapy on radiographic and scintigraphic outcomes in horses with palmar heel pain

OBJECTIVE To investigate the effects of radial extracorporeal shock wave therapy (RESWT) on radiographic and scintigraphic variables in horses with clinical pain referable to the palmar heel. METHODS Eight client-owner horses with palmar heel pain were treated with RESWT for a total of three treatments. Nuclear scintigraphy and radiography were repeated at the beginning and completion of the study. Scintigram region of interest (ROI) density ratios were calculated and compared between treated limbs, untreated limbs, and a population of comparison limbs from eight horses free of lameness. Radiographs were scored for whole navicular bone appearance as well as distal border synovial fossae number and severity. RESULTS There was not any pre- versus post-treatment difference in scintigraphic navicular pool phase or delayed phase ROI density ratios in treated limbs, or between treated and untreated limbs. Delayed phase ROI density was increased in the central navicular region in treated limbs compared to comparison limbs from non-lame horses at both time points. Radiographic scores remained unchanged. CLINICAL SIGNIFICANCE RESWT as applied in the present study has no effect on acute palmar heel region scintigraphic or radiographic parameters. Any acute clinical benefit may be due to analgesic effects rather than stimulation of local tissue metabolism.

Comparison of three point-of-care blood glucose meters for use in adult and juvenile alpacas.

OBJECTIVE To compare the performance of 3 point-of-care glucose meters in adult and juvenile alpacas with that of a laboratory-based analyzer. DESIGN Evaluation study. ANIMALS 35 adult alpacas and 21 juvenile alpacas. PROCEDURES Whole blood samples obtained via jugular venipuncture were tested with all 3 point-of-care glucose meters; plasma samples were also tested with 1 of those meters. Glucose concentrations determined by use of the point-of-care meters were compared with results from the laboratory-based analyzer. RESULTS Plasma glucose concentrations determined by use of the laboratory-based analyzer ranged from 36 to 693 mg/dL. Over the entire range of glucose concentrations tested, the Lin concordance correlation coefficient (agreement) was significant and excellent for all comparisons. Concordance decreased for 1 glucometer when testing whole blood samples over a narrower range of glucose concentrations (50 to 200 mg/dL). Bias was typically small (< 10 mg/dL) for 3 of the 4 comparisons but considerable for 1 meter with the use of whole blood. The limits of agreement were wide for all comparisons over the entire range of glucose concentrations tested but decreased to within acceptable limits when the narrower glucose range (50 to 200 mg/dL) was analyzed for 3 of the comparisons. For samples with a PCV < 25%, bias and the limits of agreement were greater for one of the meters tested. CONCLUSIONS AND CLINICAL RELEVANCE Discrepancies between point-of-care glucose meters and reference techniques can be considerable in alpacas, emphasizing the importance of assessing individual meter performance in a target population.

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.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.

Clinical use of plasma lactate concentration. Part 2: Prognostic and diagnostic utility and the clinical management of hyperlactatemia: Clinical use of plasma lactate concentration part 2

OBJECTIVE To review the current literature pertaining to the use of lactate as a prognostic indicator and therapeutic guide, the utility of measuring lactate concentrations in body fluids other than blood or plasma, and the clinical management of hyperlactatemia in dogs, cats, and horses. DATA SOURCES Articles were retrieved without date restrictions primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection. HUMAN AND VETERINARY DATA SYNTHESIS Increased plasma lactate concentrations are associated with increased morbidity and mortality. In populations with high mortality, hyperlactatemia is moderately predictive in identifying nonsurvivors. Importantly, eulactatemia predicts survival better than hyperlactatemia predicts death. Consecutive lactate measurements and calculated relative measures appear to outperform single measurements. The use of lactate as a therapeutic guide has shown promising results in people but is relatively uninvestigated in veterinary species. Increased lactate concentrations in body fluids other than blood should raise the index of suspicion for septic or malignant processes. Management of hyperlactatemia should target the underlying cause. CONCLUSION Lactate is a valuable triage and risk stratification tool that can be used to separate patients into higher and lower risk categories. The utility of lactate concentration as a therapeutic target and the measurement of lactate in body fluids shows promise but requires further research.