Margaret C. Mudge

Thromboelastography in healthy horses and horses with inflammatory gastrointestinal disorders and suspected coagulopathies

OBJECTIVES To evaluate the use of citrated recalcified (nonactivated) thromboelastography (TEG) in healthy horses and horses with colitis and suspected coagulopathies. DESIGN Prospective, observational study conducted between October 2007 and June 2009. SETTING Veterinary Teaching Hospital. ANIMALS Forty-five healthy adult horses and 12 sick adult horses with colitis and prolonged prothrombin time (PT) or activated partial thromboplastin time (aPTT). INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Whole blood was collected on admission. Coagulation profile (PT, aPTT, platelet count, and fibrinogen concentration) and citrated recalcified whole blood TEG analysis (R-time [R], K-time [K], angle [α], maximum amplitude [MA], G value [G], lysis at 60 min [LY60]) were evaluated. Mean values (SD) for TEG parameters in healthy horses were: R=10.4 (3.1) minutes; K=3.5 (1.2) minutes; α=46.3 (11.0)°; MA=55.6 (5.1) mm; G=6,429 (1,341) dyn/cm², and LY60=5.1 (2.4)%. Mean coefficients of variation for intra-assay/interindividual variability in healthy horses were: R=4.7%/30.7%, K=4.8%/35.3%, α=4.4%/23.8%, MA=1.4%/9.3%, G=3.4%/20.8%, and LY60=13.1%/47.7%, respectively. Horses with colitis and prolonged PT and/or aPTT had longer mean values for R (P<0.001) and K (P<0.001), narrower mean α (P<0.001), decreased mean MA (P=0.001), and smaller mean G (P=0.02); changes consistent with hypocoagulability. CONCLUSIONS Citrated recalcified (nonactivated) TEG demonstrated changes consistent with hypocoagulability in horses with colitis that had preidentified coagulation abnormalities. This technique has high interindividual variability and low intra-assay variability. TEG may be useful for detecting hypocoagulable states in horses with colitis and suspected coagulopathies.

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

OBJECTIVES To evaluate citrated recalcified thromboelastography (TEG) in healthy newborn foals, and to determine intra-assay, inter-individual and intra-individual (at 12 h, 24 h and 7 days after birth) variations. Additionally, to compare TEG variables, haematological values and conventional coagulation profiles from healthy, sick non-septic, and septic foals. DESIGN Prospective study. METHODS The study group comprised 18 healthy, 15 sick non-septic and 17 septic foals. Two citrated (3.2%; 1 : 9 anticoagulant : blood ratio) blood samples were submitted for haemostatic evaluation using a TEG analyser and conventional coagulation profile. TEG values (R time (R), K time (K), angle (α), maximum amplitude (MA) and G value (G)), complete blood count (CBC) and conventional coagulation profile (prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration (Fib) and antithrombin (AT)) were evaluated. Signalment, presenting complaint, sepsis scores, blood culture results and outcome were taken from the medical records of the sick foals. RESULTS Mean values ± SD for TEG variables in healthy neonatal foals were: R = 11.82 ± 5.35 min, K = 3.06 ± 1.34 min, α= 51.19 ± 12.66 degrees, MA = 55.06 ± 6.67 mm and G = 6361 ± 1700 dyn/cm(2) . Mean coefficients of variation for intra-assay/inter-individual/intra-individual in healthy foals were: R = 3.5/45.2/43.1%; K = 5.3/58.7/28.7%; α= 1.5/24.7/11.9%; MA = 0.3/12.1/6.1%; G = 1.6/26.7/14.7%. Septic foals had significantly greater α, MA and G values than sick non-septic foals, and significantly greater MA and G than healthy foals, changes that are consistent with hypercoagulability. Weak correlations were detected between TEG variables and haematological or haemostatic values. CONCLUSIONS TEG could be used to provide additional information about the haemostatic system in equine neonates.

Post-transfusion survival of biotin-labeled allogeneic RBCs in adult horses.

BACKGROUND Post-transfusion survival of allogeneic RBCs has been reported to be much shorter in horses than in other species. We hypothesized that post-transfusion survival of biotinylated allogeneic equine RBCs would be greater than the survival previously reported from studies using radioactive RBC-labeling techniques. OBJECTIVE The study objective was to determine post-transfusion survival of N-hydroxysuccinimide (NHS)-biotin-labeled allogeneic equine RBCs transfused into adult horses. METHODS Horses were adults and included 5 donors and 5 recipients. All horses were blood-typed, and donors were paired with recipients based upon blood type and crossmatch results. Donor blood was collected in a volume of 4 L into citrate phosphate dextrose adenine-1 and stored for 24 hours, labeled with NHS-biotin, and re-infused into recipients. Post-transfusion blood samples were collected at 15 minutes and at 1, 2, 3, 5, 7, 14, 21, 28, and 35 days. Biotin-labeled RBCs were detected by flow cytometry using streptavidin-phycoerythrin. Post-transfusion survival at 24 hours, lifespan, and half-life of biotinylated RBCs were determined. RESULTS Mean ± SD survival of biotinylated RBCs at 24 hours post-transfusion was 95 ± 24%; the mean lifespan of transfused allogeneic RBCs was 39 days based on calculation of a linear regression survival curve, and mean post-transfusion RBC half-life was 20 days. CONCLUSIONS Post-transfusion survival of 24-hour stored equine allogeneic RBCs was greater than previously reported but less than that observed for other companion animal species. Mechanisms for the relatively short post-transfusion lifespan of allogeneic equine RBCs remain unknown and warrant further study.

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.

Acute Hemorrhage and Blood Transfusions in Horses

Treatment of acute hemorrhage in the horse involves targeted medical management and also may involve surgical stabilization. This article provides an approach to the initial stabilization and information on available topical hemostats. The practice of blood collection and transfusion is also described, with attention to new information on viability of transfused equine blood, potential negative effects of blood transfusion, and methods of cell salvage.

Systematic evaluation of evidence on veterinary viscoelastic testing part 5: Nonstandard assays.

OBJECTIVE To systematically examine the evidence on nontraditional uses of viscoelastic coagulation monitoring in veterinary species. DESIGN Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. SETTING Academic and referral veterinary medical centers. RESULTS Databases searched included Medline, CAB abstracts, and Google Scholar. CONCLUSIONS Nontraditional assays identified included thrombelastography (TEG)-PlateletMapping (PM), functional fibrinogen assessment, and rapid-TEG (r-TEG). Direct veterinary evidence was found for only the ADP-activated PM, which appears to generate valid data in dogs but not cats or horses. Arachidonic acid activated PM shows high variability and requires further assessment and validation in veterinary species. Functional fibrinogen assays may be performed in veterinary species but may require modification due to species differences in response to abciximab. While tissue factor (TF)-activated TEG has been well described in the veterinary literature, the specific r-TEG assay has not been assessed, but presumably would be effective for generating TEG tracings and values for maximum amplitude and angle in shorter periods of time than some traditional assays.Objective To systematically examine the evidence on nontraditional uses of viscoelastic coagulation monitoring in veterinary species. Design Standardized, systematic evaluation of the literature, categorization of relevant articles according to level of evidence and quality, and development of consensus on conclusions for application of the concepts to clinical practice. Setting Academic and referral veterinary medical centers. Results Databases searched included Medline, CAB abstracts, and Google Scholar. Conclusions Nontraditional assays identified included thrombelastography (TEG)-PlateletMapping (PM), functional fibrinogen assessment, and rapid-TEG (r-TEG). Direct veterinary evidence was found for only the ADP-activated PM, which appears to generate valid data in dogs but not cats or horses. Arachidonic acid activated PM shows high variability and requires further assessment and validation in veterinary species. Functional fibrinogen assays may be performed in veterinary species but may require modification due to species differences in response to abciximab. While tissue factor (TF)-activated TEG has been well described in the veterinary literature, the specific r-TEG assay has not been assessed, but presumably would be effective for generating TEG tracings and values for maximum amplitude and angle in shorter periods of time than some traditional assays.

Presumptive bacterial translocation in horses with strangulating small intestinal lesions requiring resection and anastomosis

Objective To document whether presumptive bacterial translocation (PBT) occurs in horses with small intestinal strangulation (SIS). Design Prospective clinical cohort study. Setting University tertiary care facility. Animals Thirty-six adult horses with SIS (clinical cases) and 10 adult horses without gastrointestinal disease (control cases). Interventions Sterile collection and bacterial culture of samples from peripheral venous blood, mesenteric venous blood, mesenteric lymphatic tissue, and intestinal aspirates from horses with SIS and control horses without gastrointestinal disease. Measurements and Main Results Five of 36 (13.8%) horses with SIS had at least 1 sample yield a positive result. Shorter SIS bowel segments were more likely to yield a positive culture result. (P < 0.01). Two of 10 of control horses had positive culture results with different bacterial species identified compared to horses with SIS. Antimicrobial usage did not influence bacterial culture status (P = 0.31). There were no differences between culture-positive and culture-negative horses with SIS regarding admission, clinical, or clinicopathologic variables. Conclusions PBT occurs in normal horses and in horses with SIS. Bacterial genera differed between groups. A low incidence of PBT occurs in horses with SIS suggesting postoperative morbidity in some cases may be due to other factors.OBJECTIVE To document whether presumptive bacterial translocation (PBT) occurs in horses with small intestinal strangulation (SIS). DESIGN Prospective clinical cohort study. SETTING University tertiary care facility. ANIMALS Thirty-six adult horses with SIS (clinical cases) and 10 adult horses without gastrointestinal disease (control cases). INTERVENTIONS Sterile collection and bacterial culture of samples from peripheral venous blood, mesenteric venous blood, mesenteric lymphatic tissue, and intestinal aspirates from horses with SIS and control horses without gastrointestinal disease. MEASUREMENTS AND MAIN RESULTS Five of 36 (13.8%) horses with SIS had at least 1 sample yield a positive result. Shorter SIS bowel segments were more likely to yield a positive culture result. (P < 0.01). Two of 10 of control horses had positive culture results with different bacterial species identified compared to horses with SIS. Antimicrobial usage did not influence bacterial culture status (P = 0.31). There were no differences between culture-positive and culture-negative horses with SIS regarding admission, clinical, or clinicopathologic variables. CONCLUSIONS PBT occurs in normal horses and in horses with SIS. Bacterial genera differed between groups. A low incidence of PBT occurs in horses with SIS suggesting postoperative morbidity in some cases may be due to other factors.

Potential for iatrogenic coil embolization of the caudal cerebellar artery during treatment of internal carotid artery bifurcation in two horses with guttural pouch mycosis

CASE DESCRIPTION 2 horses were examined for chronic nasal discharge secondary to unilateral guttural pouch mycosis. CLINICAL FINDINGS Initial endoscopic examination of both horses confirmed the presence of a fungal plaque on the dorsomedial aspect of the medial compartment of the guttural pouch (auditory tube diverticulum) involving the internal carotid artery (ICA). No signs of hemorrhage or neurologic deficits were present at admission. TREATMENT AND OUTCOME Transarterial stainless steel coil embolization of the affected ICA was performed under general anesthesia, with fluoroscopic guidance. During treatment, an aberrant branch of the ICA, or a proposed bifid ICA, that anastomosed with the caudal cerebellar artery was identified. Occlusion of the distal (noncardiac) side of the aberrant branch was performed in both horses because of potential mycotic involvement at that level. Following treatment, resolution of the mycotic infection was observed in both horses; however, 1 horse developed neurologic signs compatible with unilateral caudal cerebellar artery ischemia on recovery from anesthesia; these signs resolved over the following 2 months. CLINICAL RELEVANCE Findings highlighted variability of the anatomy of the ICA in 2 horses that was identified during treatment for guttural pouch mycosis and identified caudal cerebellar artery infarction as a potential complication of treatment. Because of the size and pathway of both arterial branches, we suggest that the term bifurcation of the ICA is more appropriate than aberrant branching, as has been previously described in the literature. The information in this report may be of value to clinicians performing procedures involving the vasculature of the head and neck in horses.

Dark‐field microscopy in the assessment of large colon microperfusion and mucosal injury in naturally occurring surgical disease of the equine large colon

REASON FOR PERFORMING STUDY Intraoperative assessment of colonic viability can be challenging and largely subjective. Objective methods are often impractical. Viability is related to re-establishment of colonic perfusion; particularly microvascular perfusion. This study evaluated the utility of dark-field microscopy (DFM) of the colonic serosa as an objective method of assessing microperfusion. OBJECTIVES To measure microvascular perfusion indices (MPI) of the pelvic flexure serosa in horses with surgical colonic lesions and correlate these with macroperfusion indices (MaPI) and histomorphometry. STUDY DESIGN Prospective, clinical, case-control study. METHODS Control horses and horses with colonic volvulus (LCV), displacement, and/or simple obstruction undergoing surgery had DFM video loops performed on the pelvic flexure. Total vessel density, perfused vessel density, proportion of perfusion vessels and microvascular flow index were calculated from video analysis. Macroperfusion indices (arterial blood pressure and heart rate) were recorded. Histomorphometry was used to determine a mucosal injury score. Differences between lesions for MPI, MaPI and histomorphometry were compared using ANOVA or Kruskal-Wallis statistic. Spearman correlations between MPI with MaPI were performed. Linear regression was used to assess the relationship between MPI and histomorphometry. P<0.05 was significant. RESULTS Horses with LCV had lower perfused vessel density, proportion of microvascular perfusion vessels and flow index than horses with nonstrangulating obstructions and control horses. Macroperfusion indices were not correlated with MPI but MPI were correlated with histomorphometry. CONCLUSIONS Dark-field microscopy is achievable in the operating room and can quantify MPI from the colonic serosa in different colonic lesions. Macroperfusion indices were not related with colonic MPI. Microvascular perfusion indices can predict the severity of histopathological change at the pelvic flexure. Derangements of MPI may be more useful indicators of colonic pathology and viability and offer a more objective assessment of intestinal injury than subjective methods. Further study is needed to determine the utility of DFM in predicting survival in horses with LCV.

Coil Embolization of a Palatine Artery Pseudoaneurysm in a Gelding

OBJECTIVE To describe successful transarterial coil embolization of a palatine artery pseudoaneurysm that extended into the caudal maxillary sinus of a gelding. STUDY DESIGN Clinical report. ANIMAL A 24-year-old Morgan gelding with right-sided epistaxis. METHODS The right maxillary sinus was imaged by radiography, computed tomography, and sinoscopy. Angiography was performed to locate the source of bleeding, and transarterial coil embolization of a right palatine artery pseudoaneurysm was performed. RESULTS There was some mucoid nasal discharge and an intermittent cough postoperatively. No epistaxis was seen after embolization. There was moderate swelling of the surgical incision over the mid-cervical common carotid artery. The horse was discharged from the hospital 4 days after surgery, and had been doing well, with no signs of bleeding, for 2 months postoperatively. The horse had acute colic secondary to a strangulating lipoma at 2 months and was euthanatized after exploratory celiotomy. Placement of embolization coils in the right palatine artery was confirmed by CT and necropsy. CONCLUSIONS Severe epistaxis in the horse may be caused by a ruptured major palatine artery pseudoaneurysm. Occlusion of this vessel can be successfully accomplished by transarterial coil embolization.