Clinical Assessment of Primary Hemostasis: A Review.

Primary hemostatic disorders such as thrombocytopenia and thrombocytopathia are commonly encountered in small animal practice. The key stages of primary hemostasis include platelet adhesion, activation, and aggregation. Understanding the interaction between tissues, platelets, and signaling molecules not only helps clinicians comprehend clot formation but also better recognize thrombocytopathias. Although congenital thrombocytopathia is rare, commercially available platelet function tests allow veterinarians to narrow differentials in many clinical settings. Thrombocytopenia can be easily diagnosed in any clinical setting. In this paper, we review the current understanding of primary hemostasis in veterinary medicine, including the clinical presentation and available diagnostics to identify platelet abnormalities.

Comparison of 4 point-of-care techniques to detect correct positioning of nasogastric tubes in dogs (2020-2021).

OBJECTIVE: To compare 4 point-of-care (POC) techniques to assess nasogastric (NG) tube placement versus radiographs as a reference standard. POC methods included air inflation with auscultation, fluid aspiration with pH measurement, ultrasonography, and capnography. DESIGN: Prospective observational study in hospitalized dogs between 2020 and 2021. SETTING: University teaching hospital. ANIMALS: Fifty-one dogs requiring NG tube placement as part of their normal care. INTERVENTIONS: After standard blind NG tube placement, each POC method was performed following standardized instructions. All POC methods were scored as to whether the investigator believed the tube to be in the gastrointestinal tract (as indicated by positive auscultation of borborygmus during insufflation, positive fluid aspiration with pH ≤5, presence of hyperechoic shadow in the esophagus, or absence of capnographic waveform). Subsequently, radiographs were taken to determine NG tube position as a gold standard. The sensitivity, specificity, and accuracy of each test as compared to 2-view thoracic radiographs were determined. MEASUREMENTS AND MAIN RESULTS: Sensitivity, specificity, and accuracy for each POC technique were as follows: air auscultation (84.4%, 50.5%, and 80.4%, respectively), neck ultrasound (95.6%, 83.3%, and 94.1%, respectively), capnography (91.1%, 33.3%, and 84.3%, respectively), and fluid aspiration with pH measurement (22.2%, 100%, and 31.4%, respectively). CONCLUSIONS: Among the 4 techniques evaluated, neck ultrasound had the best overall performance for assessing NG tube placement. Fluid aspiration with pH measurement might also have potential due to perfect specificity, but its clinical utility may be limited by low sensitivity and accuracy. Nonetheless, 2-view thoracic radiography should still be considered the standard method for confirmation of NG tube placement as none of the 4 POC techniques investigated showed both high sensitivity and perfect specificity.

Interstitial glucose monitoring has acceptable clinical accuracy in juvenile dogs.

OBJECTIVE: To compare the performance of an interstitial glucose monitor (IGM) versus a portable blood glucose monitor (PBGM) in sick juvenile dogs in a veterinary ICU. ANIMALS: 16 client-owned dogs admitted to the university teaching hospital under 1 year of age with systemic illness. PROCEDURES: Paired interstitial and blood glucose samples were collected. A third glucose measurement with a reference method was obtained when IGM and PBGM values were clinically disparate. Analytical accuracy was measured by Pearson correlation and agreement statistics, including mean absolute relative difference (MARD), bias, and 95% limits of agreement. The Parkes consensus error grid analysis was performed to assess clinical accuracy. RESULTS: 159 paired glucose measurements were available for analysis. Comparison of IGM readings to PBGM measurements resulted in an MARD of 15.4% and bias of -2.6%, with the 95% limits of agreement ranging from -42.5% to 37.4%. Positive correlation between IGM and PBGM (Pearson r = 0.65) was found. On consensus error grid analysis, 100% of the pairs fell into clinically acceptable zones (74.2% in zone A, and 25.8% in zone B). When disparate IGM and PBGM readings were compared to a laboratory reference standard (n = 13), both methods resulted in high MARD and wide limits of agreement. CLINICAL RELEVANCE: The IGM provides clinically acceptable glucose measurements compared to PBGM to monitor glucose levels in juvenile dogs in a clinical setting. Further clinical studies with a larger sample size, particularly in the hypoglycemic range, are needed to assess IGM performance in the lower glucose range.

Comparison of a commercial immunochromatographic strip crossmatch kit and standard laboratory crossmatch methods for blood transfusion compatibility in dogs.

OBJECTIVE: To evaluate agreement between 2 standard laboratory (SL) methods and an immunochromatographic strip (ICS) method to crossmatch dogs receiving RBC transfusions. A second objective was to evaluate uninterpretable SL crossmatch results as compared to ICS in the presence of autoagglutination. DESIGN: Prospective observational study (September 2018 to October 2019). SETTING: University teaching hospital. ANIMALS: Forty anemic dogs receiving RBC transfusions. INTERVENTIONS: None. MEASUREMENT AND MAIN RESULTS: All dogs received DEA 1-negative packed RBCs. Three crossmatch methods were evaluated against the same unit transfused to each dog: SL method performed at institutional laboratory (SL-I), SL method sent to a commercial laboratory (SL-C), and a commercially available point-of-care ICS method. Major and minor crossmatches were incompatible for 2.5%/7.5% of ICS tests, 82.5%/52.5% of SL-I tests, and 52.5%/27.5% of SL-C tests. Agreement between ICS and SL-C major (κ = 0.05) and minor (κ = 0.02) crossmatches and between ICS and SL-I major (κ = 0.009) and minor (κ = 0.03) crossmatches was slight. Agreement between SL-C and SL-I major (κ = -0.06) and minor (κ = -0.12) crossmatches was poor. Results of major and minor crossmatches were uninterpretable due to autoagglutination in 38%/38% for SL-I and 29%/18% for SL-C crossmatches. ICS method was interpretable for 93% (major) and 98% (minor) crossmatches. After exclusion of uninterpretable SL pairings, agreement still remained poor to slight between all tests. Only 1 of 40 dogs (2.5%; 95% confidence interval: <1.0%-13.2%) had an immediate immunological transfusion reaction. CONCLUSIONS: Lack of agreement between all methodologies was noted. The high level of incompatibility predicted by SL methods despite lack of clinically relevant reactions suggests a high false incompatibility rate as compared to the ICS test. ICS testing was also able to give results more frequently in the face of autoagglutination. Further work is needed to investigate the ICS method's ability to predict clinically significant transfusion reactions.

Assessment of the physical compatibility of injectable enrofloxacin with commonly used intravenous fluids and drugs during simulated Y-port administration.

OBJECTIVE: To evaluate physical compatibility of small animal (SAE) and large animal (LAE) injectable formulations of enrofloxacin with select IV fluids and drugs. SAMPLE: 162 admixtures containing SAE or LAE with saline (0.9% NaCl) solution, lactated Ringer solution (LRS), Plasma-Lyte A (PLA), 6% hydroxyethylstarch 130/0.4 (HES), metoclopramide, or ampicillin-sulbactam. PROCEDURES: In the first of 2 simultaneously conducted experiments, admixtures containing enrofloxacin (10 mg/kg) and a volume of IV fluid that would be administered over a 20-minute period when dosed at the maintenance infusion rate (40 mL/kg/d for saline solution, LRS, and PLA and 20 mL/kg/d for HES) were created. In the second experiment, enrofloxacin (10 mg/kg) was admixed with saline solution (40 mL/kg/d) and metoclopramide (2 mg/kg/d) or ampicillin-sulbactam (30 mg/kg). In both experiments, admixture components were infused into a flask over 20 minutes assuming patient weights of 5, 10, and 20 kg. Admixtures were created by use of undiluted SAE and SAE diluted 1:1 with saline solution and undiluted LAE and LAE diluted 1:1 and 1:10 with saline solution. Admixtures were assessed for physical incompatibility at 0, 15, 30, and 60 minutes after completion of mixing. Physical incompatibility was defined as gross precipitation, cloudiness, Tyndall effect, or change in turbidity. RESULTS: Admixtures containing undiluted SAE or LAE were physically incompatible with saline solution, PLA, LRS, and HES. Because saline solution was used to dilute SAE and LAE, all admixtures containing diluted SAE or LAE were also physically incompatible. Physical compatibility of enrofloxacin with metoclopramide or ampicillin-sulbactam could not be assessed because those admixtures also contained saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: Enrofloxacin was physically incompatible with all tested solutions.

RNA sequencing of whole blood in dogs with primary immune-mediated hemolytic anemia (IMHA) reveals novel insights into disease pathogenesis.

Immune-mediated hemolytic anemia (IMHA) is a life-threatening autoimmune disorder characterized by a self-mediated attack on circulating red blood cells. The disease occurs naturally in both dogs and humans, but is significantly more prevalent in dogs. Because of its shared features across species, dogs offer a naturally occurring model for studying IMHA in people. In this study, we used RNA sequencing of whole blood from treatment-naïve dogs to study transcriptome-wide changes in gene expression in newly diagnosed animals compared to healthy controls. We found many overexpressed genes in pathways related to neutrophil function, coagulation, and hematopoiesis. In particular, the most highly overexpressed gene in cases was a phospholipase scramblase, which mediates the externalization of phosphatidylserine from the inner to the outer leaflet of cell membranes. This family of genes has been shown to be critically important for programmed cell death of erythrocytes as well as the initiation of the clotting cascade. Unexpectedly, we found marked underexpression of many genes related to lymphocyte function. We also identified groups of genes that are highly associated with the inflammatory response and red blood cell regeneration in affected dogs. We did not find any genes that distinguished dogs that lived vs. those that died at 30 days following diagnosis, nor did we find any relevant genomic signatures of microbial organisms in the blood of affected animals. Future studies are warranted to validate these findings and assess their implication in developing novel therapeutic approaches for dogs and humans with IMHA.

Effect of packed red blood cell transfusion on thromboelastographic tracings in dogs with naturally occurring anemia.

OBJECTIVE: To assess the effect of packed RBC (pRBC) transfusion on thromboelastographic (TEG) tracings in dogs with naturally occurring anemia. ANIMALS: 22 clinically anemic dogs that received a pRBC transfusion. PROCEDURES: For each dog, a blood sample was collected before and within 3 hours after completion of the pRBC transfusion for a CBC, nonactivated TEG analysis, and measurement of blood viscosity. Wilcoxon signed rank tests were used to compare CBC, viscosity, and TEG variables between pretransfusion and posttransfusion blood samples. Multivariable linear regression was used to assess the effects of pretransfusion-posttransfusion changes in Hct, WBC count, and platelet count on changes in TEG variables. RESULTS: Median posttransfusion Hct (21%; range, 13% to 34%) was significantly greater than the median pretransfusion Hct (12.5%; range, 7% to 29%). Packed RBC transfusion was associated with a median increase in Hct of 6.2% (range, 1.2% to 13%). Maximum amplitude significantly decreased from 74.9 to 73.8 mm and clot strength significantly decreased from 14,906 to 14,119 dynes/s after pRBC transfusion. Blood viscosity significantly increased, whereas platelet and WBC counts significantly decreased after transfusion. Multivariable linear regression revealed that pretransfusion-posttransfusion changes in Hct, WBC count, and platelet count were not associated with changes in TEG variables. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that pRBC transfusion had only small effects on the TEG tracings of hemodynamically stable dogs. Therefore, large changes in TEG tracings following pRBC transfusion are unlikely to be the result of the transfusion and should be investigated further.

Cryopreservation of feline red blood cells in liquid nitrogen using glycerol and hydroxyethyl starch.

OBJECTIVES: The objective of this study was to evaluate the techniques and short-term effects of cryopreservation of feline red blood cells (RBCs) in liquid nitrogen using glycerol or hydroxyethyl starch (HES) as a cryoprotectant. METHODS: Feline RBCs were manually mixed with either 20% glycerol or 12.5% HES and frozen for 24 h in liquid nitrogen. The samples were thawed and glycerolized samples were manually washed. Success of the freeze/thaw process was determined by recovery rate of RBCs and evaluation of morphological changes using scanning electron microscopy (SEM). A unit of canine packed RBCs was also subjected to the same methodology to evaluate the cryopreservation handling technique. RESULTS: Feline RBCs preserved with 20% glycerol had a high recovery rate (94.23 ± 1.25%) immediately after thawing. However, the majority of the cells were lost during the washing process, with a final packed cell volume of <1%. A recovery rate was unable to be assessed for samples preserved with HES owing to the high viscosity of the mixture. SEM revealed significant morphological changes after glycerol was added to the feline RBCs. Although these morphological changes were partially reversed after thawing, the majority of the RBCs were lost during the washing process. Minimal morphological changes were noted in the HES sample. Similar results were noted with the canine RBCs. CONCLUSIONS AND RELEVANCE: The described manual technique for cryopreservation using glycerol was not able to successfully preserve feline or canine RBCs. In the present study, it was difficult to make conclusions about the efficacy of HES. Further studies evaluating HES as a cryoprotectant are warranted.

Ultrasound measurements of the caudal vena cava before and after blood donation in 9 greyhound dogs.

This prospective study evaluated variation in the diameter of the caudal vena cava (DCdVC) as a marker of change in intravascular volume before and after blood donation in greyhound dogs. A preliminary study determined that the DCdVC increased with body weight. Nine greyhound blood donors had ultrasonographic images acquired of the maximum and minimum DCdVCs in transverse and sagittal orientations and sagittal aortic diameter (AoD) before and after blood donation. The collapsibility index = [(maximal mean transverse DCdVC - minimal mean transverse DCdVC)/maximal mean transverse DCdVC] and transverse DCdVC:AoD ratio were calculated for each dog. In the greyhounds, the changes in mean minimal and maximal transverse DCdVC (0.69 and 0.84 mm, respectively) and sagittal mean maximal DCdVC (0.9 mm) and collapsibility index (0.018) were significantly different (P < 0.05) before and after blood donation. While statistically significant, the magnitude of DCdVC change found in this limited number of greyhound dogs with 8% intravascular volume loss during blood donation was small. This magnitude of change is likely indistinguishable in clinical patients.

Mesures par ultrason de la veine cave caudale avant et après le don de sang chez 9 chiens Greyhound. Cette étude prospective a évalué la variation du diamètre de la veine cave caudale (DCdVC) comme marqueur du changement du volume intravasculaire avant et après le don de sang chez les chiens Greyhound. Une étude préliminaire a déterminé que le DCdVC a augmenté le poids corporel. Neuf Greyhound donneurs de sang avaient des images échographiques acquises pour les DCdVC maximum et minimum dans les orientations transversales et sagittales et le diamètre aortique sagittal (AoD) avant et après le don de sang. L'indice de collapsibilité = [(DCdVC maximal transversal moyen ­ DCdVC minimal transversal moyen)/DCdVC maximal transversal moyen] et le ratio transversal DCdVC:AoD ont été calculés pour chaque chien. Chez les Greyhounds, les changements des DCdVC minimaux et maximaux transversaux moyens (0,69 et 0,84 mm, respectivement) et le DCdVC maximal sagittal moyen (0,9 mm) et l'indice de collapsibilité (0,018) étaient significativement différents (P < 0,05) avant et après le don de sang. Même si ce changement est significatif sur le plan statistique, l'ampleur du changement DCdVC constatée dans ce nombre limité de chiens Greyhound ayant 8 % de perte de volume intravasculaire durant le don de sang était faible. Cette ampleur de changement est probablement impossible à distinguer chez les patients cliniques.(Traduit par Isabelle Vallières).

Comparison of ultrasound-guided and landmark-based techniques for central venous catheterization via the external jugular vein in healthy anesthetized dogs.

OBJECTIVE To compare time to achieve vascular access (TTVA) between an ultrasound-guided technique (UST) and landmark-based technique (LMT) for central venous catheter (CVC) placement in healthy anesthetized dogs. ANIMALS 39 purpose-bred hounds. PROCEDURES Anesthetized dogs that were hemodynamically stable following completion of a terminal surgical exercise were enrolled in the study during 2 phases, with a 45-day intermission between phases. For each dog, a UST and LMT were used for CVC placement via each external jugular vein by 2 operators (criticalist and resident). The TTVA and number of venipuncture attempts and catheter redirections were recorded for each catheterization. Placement of the CVC was confirmed by contrast fluoroscopy. After euthanasia, a gross dissection was performed during which a hematoma score was assigned to the catheter insertion site. For each phase, nonlinear least squares estimation was used for learning curve analysis of the UST. RESULTS Median TTVA, number of venipuncture attempts and catheter redirections, and hematoma score did not differ significantly between the 2 operators for either technique. Median TTVA for the UST (45 seconds) was significantly longer than that for the LMT (7 seconds). Learning curve analysis indicated that 8 and 7 UST catheterizations were required to achieve performance stability in phases 1 and 2, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the UST was comparable to the LMT for CVC placement in healthy dogs. The extra time required to perform the UST was not clinically relevant. Additional studies evaluating the UST for CVC placement in clinically ill dogs are warranted.

Effects of hematocrit and red blood cell-independent viscosity on canine thromboelastographic tracings.

BACKGROUND: It is well established that hematocrit (Hct) influences whole blood thromboelastography (TEG) tracings. Previous studies showed hypercoagulable TEG tracings in anemic patients despite clinical expectations that anemia often prolongs bleeding. TEG is a viscoelastic assessment of clot kinetics, and Hct is the main determinant of whole blood viscosity. TEG changes in anemia may be an in vitro artifact due to Hct effect on blood viscosity rather than true in vivo changes in hemostasis. The effect of changes in whole blood viscosity on TEG independent of Hct is not well understood. STUDY DESIGN AND METHODS: Twenty-one blood samples from seven dogs were manipulated to produce one of three Hct conditions (45, 20, and 10%). Each was tested in two situations: viscosity adjusted to normal by adding alginate (ALG) or dilution with equal volume of saline (SAL). Both samples were analyzed with TEG simultaneously. RESULTS: Twenty percent Hct plus ALG and 10% Hct plus ALG were significantly more viscous than their SAL counterparts (p=0.0156). Ten percent Hct plus SAL, 20% Hct plus SAL, and 45% Hct plus SAL all had different viscosities (p=0.006). Twenty percent Hct plus SAL and 10% Hct plus SAL had significantly shorter K and higher angle, MA, and G compared to their ALG counterparts as well as 45% Hct plus SAL (p<0.05). CONCLUSIONS: ALG samples with low Hct, normal viscosity showed hypocoagulable tracings, whereas SAL samples with low Hct, low viscosity showed hypercoagulable tracings. TEG variables are influenced by whole blood viscosity altered with ALG, independently of Hct.

Successful treatment of a dog with massive 5-fluorouracil toxicosis.

OBJECTIVE: To describe the clinical presentation and successful treatment of a dog that ingested a lethal dose (approximately 330 mg/kg) of 5-fluorouracil (5-FU). CASE SUMMARY: A 1-year-old male intact German Shepherd dog was presented to the Emergency Service of the Ohio State University Veterinary Medical Center after ingesting 10 g of 5% 5-FU cream. The dog rapidly developed refractory seizures and was managed by inducing heavy sedation with phenobarbital, benzodiazepines, ketamine, and propofol, necessitating 48 hours of mechanical ventilation. Seizure activity continued despite these treatments until IV administration of levetiracetam. The dog was discharged from the hospital 6 days after admission and remains neurologically normal currently, with no further seizure activity after 9 months. NEW INFORMATION PROVIDED: This report documents the first successful treatment of a dog that ingested > 43 mg/kg of 5-FU. In this case, the use of rapid decontamination, heavy sedation with anticonvulsant medications including levetiracetam to control seizures, and mechanical ventilation may have contributed to a positive outcome.

Use of the PleuralPort device for management of pleural effusion in six dogs and four cats.

OBJECTIVE: To describe the placement technique, complications, and outcomes associated with use of the PleuralPort device for management of pleural effusion in dogs and cats. STUDY DESIGN: Case Series. ANIMALS: Six dogs and 4 cats. METHODS: Medical records of all animals with pleural effusion managed with the PleuralPort device were reviewed. Data regarding signalment, fluid analysis, placement technique, duration of function, duration of implantation, complications, and outcome were collected. Owners and referring veterinarians were contacted for follow-up information. RESULTS: Nine animals had chylous effusion and 1 dog had pleural carcinomatosis. Eleven ports were placed with 1 cat receiving bilateral ports. Four animals developed complications. One cat developed pneumothorax immediately after implantation and was euthanatized. In 2 dogs and 1 cat, the ports obstructed. The 6 remaining animals had functioning ports at time of death or resolution of effusion and no longer required use of the port. No significant port migration, irritation, or infection of the device was reported. Excluding the cat with pneumothorax, median duration of port function was 20 days (range 1-391), and median duration of port implantation was 391 days (range 6-723). CONCLUSIONS: The PleuralPort device is a feasible option for the management of pleural effusion in dogs and cats.