Effect of storage conditions on hemostatic parameters of canine plasma obtained for transfusion

OBJECTIVE: To evaluate the effects of various storage conditions on one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), and fibrinogen concentration of canine plasma collected for transfusion. SAMPLE POPULATION: Plasma from 9 dogs. PROCEDURE: Whole blood was collected from dogs by means of jugular venipuncture and centrifuged at 7,300 X g for 20 minutes at 0 C. A plasma extractor was then used to generate plasma. Aliquots of plasma were collected in segments of plastic tubing and in microcentrifuge tubes, and plasma collection bags, tubing segments, and microcentrifuge tubes were immediately frozen at -30 C. Additional tubing segments and microcentrifuge tubes were stored at 2 C. After 1 week of storage, all samples were thawed, and OSPT, APTT, and fibrinogen concentration were measured. Collection bags and microcentrifuge tubes were refrozen at -30 C, and values were measured again 30 days after blood collection. RESULTS: Values for OSPT, APTT, and fibrinogen concentration did not vary significantly with storage time, temperature, or container. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that storage for up to 30 days and at 2 C versus -30 C did not have any significant effect on hemostatic parameters of canine plasma obtained for transfusion.     

Comparative stability of canine and feline hemostatic proteins in freeze‐thaw‐cycled fresh frozen plasma

Objective – To evaluate the stability of canine and feline hemostatic proteins in freeze‐thaw‐cycled (FTC) fresh frozen plasma (FFP). Design – Prospective study. Setting – Veterinary Teaching Hospital. Animals – Nine blood donor dogs and 10 blood donor cats. Interventions – Whole blood was collected and separated into packed RBC and plasma units according to standard methods. Each unit of plasma was divided into 2 equal aliquots and frozen (?41°C). One aliquot from each donor (FTC) was then thawed and then refrozen (?41°C) until time of analysis. The second aliquot (nonfreeze‐thaw‐cycled; NFTC) remained frozen until time of analysis. The hemostatic proteins assessed included coagulation factors, anticoagulant factors (antithrombin and Protein C), and adhesive proteins (fibrinogen and von Willebrand Factor). The coagulant activities of factors II, VII, VIII, IX, X, XI, and XII were measured in modified one‐stage activated partial thromboplastin time or prothrombin time assays. Antithrombin and Protein C activities were measured in chromogenic substrate assays. Clottable fibrinogen was measured via the Clauss method, and von Willebrand Factor concentration (vWF:Ag) was measured in an ELISA. A paired t‐test was utilized to identify differences in factor activity or concentration between FTC FFP and NFTC FFP. Measurements and Main results – No clinically or statistically significant differences (all P>0.05) were identified between FTC FFP and NFTC FFP. Conclusions – Refreezing FFP within 1 hour of initial thawing appeared to have no deleterious effects on the hemostatic protein activity or content of that unit. Transfusion of FTC FFP is expected to provide the recipient with comparable replacement of hemostatic proteins as FFP that has remained frozen.     

Stability of stored canine plasma for hemostasis testing

BACKGROUND: A review of the literature revealed limited information about the stability of samples for coagulation testing in dogs. OBJECTIVE: The aim of this study was to evaluate the stability of individual coagulation factors, clotting times, and other parameters of hemostasis in stored canine plasma. METHODS: Citrated plasma samples were obtained from 21 dogs. Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, and factor I, II, V, VII, VIII, IX, X, XI, and XII activities were measured on an automated coagulation analyzer with commercially available reagents. Antithrombin (AT) activity and D-dimer concentration were measured on an automated chemistry analyzer using validated kits. Samples were analyzed within 1 hour after collection (initial analysis) and once daily for 2 or 4 consecutive days following storage at room temperature (RT) or 4 degrees C, respectively. RESULTS: Storage time at either temperature did not have any effect on PT, factor II, V, VII, X, or XII activities, D-dimer concentration, or AT activity. In contrast, aPTT was significantly prolonged after 72 and 96 hours at 4 degrees C; fibrinogen concentration was decreased after 48 hours at RT; the activities of factors VIII and IX were decreased after 48, 72, and 96 hours at 4 degrees C; and factor XI activity was decreased after 72 hours at 4 degrees C. CONCLUSIONS: Results suggest that storage of canine plasma for 2 days at RT does not have a significant effect on hemostasis test results with the exception of a slight decrease in fibrinogen concentration. In contrast, aPTT and factors VIII, IX, and XI were unstable in refrigerated plasma after 48 or 72 hours of storage.     

Afibrinogenemia and a circulating antibody against fibrinogen in a Bichon Frise dog

A 1.5-year-old female Bichon Frise dog was evaluated for a life-threatening hemorrhagic condition that occurred after ovariohysterectomy, requiring 4 whole-blood transfusions. A hemostatic profile, including activated clotting time (ACT), one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), buccal mucosal bleeding time, and specific assays (heat-precipitation microhematocrit method and electroimmunoassay) for fibrinogen, were performed to investigate the coagulopathy. Clotting times for all tests having a fibrin clot endpoint (ACT, OSPT, APTT) and buccal mucosal bleeding time were prolonged. Plasma fibrinogen was not detected by heat-precipitation microhematocrit method or electroimmunoassay. Using the Ellis-Stransky method, a mixture of patient plasma and normal canine plasma with known fibrinogen content yielded substantially less than the calculated fibrinogen concentration, indicating the presence of an interfering substance. The interferent properties of the patient's plasma were retained following heat precipitation at 56 degrees C indicating the absence of a pyroglobulin or an abnormal fibrinogen molecule. Radial immunodiffusion assay using the patient's plasma and activated thrombin confirmed the existence of an inhibitor to the formation of fibrin. Western blot analysis using the patient's plasma identified an IgG antibody that reacted with the Beta- and gamma- but not the Alpha-subunits of canine fibrinogen. Antibody was detected in samples taken 8, 16, and 68 days after the surgery; peak titers were evident at day 16. These results supported a diagnosis of afibrinogenemia with a circulating antibody inhibitor to fibrin clot formation that developed secondary to blood transfusion.     

Submitting canine blood for prothrombin time and partial thromboplastin time determinations

Practitioners commonly submit samples from dogs for partial thromboplastin time and prothrombin time determinations. Controversy exists as to the necessity for rapid separation of plasma and cells, and submission of the plasma on ice (or frozen). The purpose of this study was to address three questions. First, is it better to submit plasma or is whole blood satisfactory? Second, is it necessary to refrigerate the sample or is maintenance at room temperature (20° C) adequate? Third, does the sample have to arrive at the laboratory within a few hours of collection or can reliable partial thromboplastin time/prothrombin time determinations be made on samples up to 48 hours old?It has been shown by this study that reliable partial thromboplastin time and prothrombin time determinations can be carried out on canine plasma for up to 48 hours after collection regardless of whether or not the plasma is separated immediately; however the samples must be kept at 4°C. If the samples are maintained at room temperature, reliable prothrombin time determinations can be obtained for up to six hours after collection regardless of whether or not the plasma is separated immediately. Reliable partial thromboplastin time determinations can be made on plasma stored at 20°C for up to 24 hours after collection and possibly longer (up to 48 hours) if the plasma has been separated immediately.     

Endotoxin-induced changes in the hemostatic system in neonatal calves: the effect of antiserum to a mutant Escherichia coli (J-5)

Changes in the hemostatic system were studied in 22 neonatal calves given a small dosage of Escherichia coli endotoxin (0.5 microgram/kg) by slow (5-hour) IV infusion. The effect of pretreatment with an antiserum to mutant of E coli O111:B4 (J-5) was evaluated. The platelet count, plasma fibrinogen concentration, prothrombin time, and activated partial thromboplastin time changed significantly from base line during and after endotoxin infusions in all calves. The mean platelet count was significantly decreased from 1 through 24 hours after endotoxin infusion was started. Mean plasma fibrinogen was decreased 2 through 12 hours after endotoxin infusion was started. The mean prothrombin time and activated partial thromboplastin time were significantly greater than base line at 3 to 6 hours and 3 to 12 hours, respectively, after endotoxin infusion was started. Serum concentration of fibrinolytic degradation products remained less than 10 micrograms/ml. Bovine J-5 antiserum did not prevent the endotoxin-induced changes in the hemostatic system of these neonatal calves.     

Evaluation of EDTA hematology tubes for collection of blood samples for tests of secondary hemostasis in dogs

OBJECTIVE: To evaluate the use of EDTA tubes for collection of blood samples for assays of secondary hemostasis in dogs. ANIMALS: 108 dogs of various ages, breeds, and sexes (19 healthy and 89 with abnormalities of secondary hemostasis). PROCEDURES: Blood samples were collected via cephalic venipuncture and transferred to sodium citrate tubes and EDTA tubes. Plasma was harvested from each type of tube for assays of concentrations of fibrinogen and D-dimer as well as prothrombin time, activated partial thromboplastin time, and antithrombin activity. Intra-assay and interassay precision and correlation coefficients for all hemostatic tests were calculated for each type of plasma sample. The effect of storage conditions on assay results for the 2 types of plasma samples was also evaluated. RESULTS: Results of hemostatic tests were highly correlated between citrated and EDTA-treated plasma samples. Intra-assay imprecision for all hemostatic tests with the exception of D-dimer concentration was < 10% for both citrated and EDTA-treated plasma samples; interassay imprecision was higher for EDTA-treated versus citrated plasma samples. Storage of plasma samples for 1 hour did not result in significantly different assay results for either type of plasma sample, but storage for 2 hours significantly affected values for EDTA-treated plasma samples. CONCLUSIONS AND CLINICAL RELEVANCE: Although evaluation of the sensitivity and specificity of hemostatic tests that use EDTA-treated plasma samples is required, EDTA may be a suitable alternative to sodium citrate as an anticoagulant for use in hemostatic testing in conditions in which tests could be performed within 1 hour after sample collection.     

Blood coagulation parameters in clinically normal intensively farmed red deer (Cervus elaphus) and fallow deer (Dama dama)

Reference ranges for five parameters of blood coagulation were established in clinically normal farmed fallow deer (Dama dama) and red deer (Cervus elaphus). Storage of plasma at -15 degrees C resulted in small increases in activated partial thromboplastin time (APTT) for both species, and in the one stage prothrombin time (OSPT) of fallow deer, between days 1 and 30. These times were then stable between days 30 and 60. The fibrinogen levels of fallow deer plasma showed a small apparent increase over 60 days. These storage artefacts were not of sufficient magnitude to preclude the use of such plasma for diagnostic purposes although they could limit its use in research. Levels of fibrin/fibrinogen degradation products (FDP) were not affected by storage at -15 degrees C. Rabbit brain thromboplastin appeared adequate for OSPT determination in both species. The activated clotting time (ACT) is recommended as a field test for screening the intrinsic and common pathways of blood coagulation in deer.     

Use of hexadimethrine bromide as a heparin-neutralizing agent in canine plasma

Hexadimethrine bromide was evaluated as a heparin-neutralizing agent in a simple modification of the activated partial thromboplastin time test in canine plasma. Addition of various amounts of heparin in vitro to canine plasma indicated that heparin could be neutralized by adding 0.5 micrograms of hexadimethrine bromide 15 s before CaCl2 was added to the reaction mixture of the activated partial thromboplastin time test. In 8 dogs given (subcutaneous injection) 500 USP units of sodium heparin/kg, marked individual variations in clotting time prolongations were observed over the 12-hour period of study. The hexadimethrine bromide modification effectively neutralized the heparin-related clotting time prolongations to values that were not significantly different from base-line (preheparin) activated partial thromboplastin time values. The modification seems to be useful in confirming the presence of heparin and in monitoring heparin therapy in dogs.     

Temporal effects of freezing on plasma nitric oxide concentrations in ponies

The purpose of this study was to compare concentrations of nitric oxide (NO) in fresh plasma versus frozen plasma, and determine the temporal effects of freezing on jugular venous plasma NO concentrations in clinically healthy ponies. Twenty-eight helminth-naïve ponies, aged from 4 to 6 mo, were raised and maintained under parasite-free conditions. Blood was collected from the jugular vein, centrifuged, and the plasma supernatant was analyzed fresh for NO concentrations using a chemiluminescent method. The remaining samples were aliquoted into 12 samples and stored at −70°C until they were analyzed for NO concentration. Plasma NO concentration was measured at monthly intervals for 12 mo. There were significant differences in the plasma NO concentration across time compared with the baseline value at 1, 3, 4, 6, 7, and 11 mo. However, these values remained within the range for clinically healthy equids compared with concentrations of NO from horses with increased NO from diseased states.     

Changes in platelet concentrates from dogs due to storage. I. Platelet count in in vitro function]

The possibility of storage of canine platelet concentrates (PC) was investigated using PC from dogs which were obtained with an automatic cell separator in C4-cell separation sets with low gasdiffusionable Polyvinylchlorid (PVC) storage containers or in C4L-sets developed for storage with high gasdiffusionable Polyolefin (PO) containers, respectively. The storage was carried out for a period of 10 days under permanent agitation at 22 degrees C (C4/22 degrees C, n = 10; C4L/22 degrees C, n = 11) or at 4 degrees C (C4L/4 degrees C, n = 6), respectively. Measurements were done directly after production of the PC, after 6 hours and then daily during the 10-day storage period. In the first part of this paper the results of platelet count (determined automatically with a blood cell differentiation automat and visually), the number of platelet aggregates, the mean platelet volume (MPV) as well as the platelet function with regard to the platelet aggregation induced by collagen or ADP and the resonance-thrombogram (RTG) are presented. The platelet count, measured automatically as well as visually, remained preponderantly constant over the complete storage time in all storage conditions. Dependent on the storage conditions--especially under storage at 22 degrees C--an increase of the number of platelet aggregates and a decrease of MPV was determined. In addition, the loss of platelet function measured by aggregation induced by collagen as well as by ADP showed a significant dependency of storage conditions. The stored platelets lost their ability to aggregate under C4/22 degrees C-conditions after a storage period of 2 days, under C4L/22 degrees C-conditions after 4 days and under C4L/4 degrees C-conditions not before 8 days of storage. Previous resuspending of platelets in fresh plasma delayed the loss of platelet function. Because the loss of platelet function described in the RTG became significant at nearly the same point in time, a storage of canine PC under corresponding conditions can be recommended for upto 2 days (C4/22 degrees C), for 4 days (C4L/22 degrees C) or 8-10 days (C4L/4 degrees C), respectively.     

Serum and plasma latex agglutination tests for detection of fibrin(ogen) degradation products in clinically ill dogs

Abstract: An increased concentration of fibrin(ogen) degradation products (FDPs) commonly is used in conjunction with other hemostatic test abnormalities to identify patients with disseminated intravascular coagulation (DIC). Positive FDP results, however, have been observed in dogs without clinical evidence of DIC. The purpose of this study was to evaluate FDP concentrations in a group of clinically ill dogs with a variety of disorders. Dogs included in the study had the following hemostatic parameters evaluated: prothrombin time, activated partial thromboplastin time, fibrinogen concentration, platelet count, and FDP concentration. Two rapid latex agglutination methods were compared for detecting FDP in serum samples (Thrombo-Wellcotest, International Murex Technologies Corp) and plasma samples (FDP Plasma, American Bioproducts Inc). Results of the serum FDP method were positive in 8% (4/50) of the dogs tested: 3 with DIC and 1 with immune-mediated hemolytic anemia and liver disease. Results of the plasma FDP test were positive in 60% (30/50) of the animals tested: 6 with DIC, 3 with confirmed thrombosis, and 21 with a variety of conditions, including neoplasia, immune-mediated hemolytic anemia, pancreatitis, gastric dilatation-volvulus, heat stroke, severe trauma, sepsis, protein-losing nephropathy, liver disease, hyperadrenocorticism, and chronic heart failure. Because the plasma FDP test was positive more frequently than the serum FDP test in ill dogs, it may be more sensitive for the detection of canine FDP.     

Hemostatic response to surgical neutering via ovariectomy and ovariohysterectomy in dogs

Objective-To investigate the hemostatic response to surgery and compare the response for ovariohysterectomy with that for ovariectomy and to evaluate the usefulness of thromboelastography on plasma samples. Animals-42 female dogs. Procedures-Dogs were assigned to undergo ovariohysterectomy or ovariectomy. Blood samples were collected immediately before and 1, 6, and 24 hours after surgery and stored at -80°C for subsequent analysis. Plasma samples were subjected to thromboelastography after thawing. In addition, coagulation variables were measured, including concentrations of von Willebrand factor antigen, fibrinogen, antithrombin, and protein C; activity of factor VIII; activated partial thromboplastin time; prothrombin time; and thrombin time. The fibrinolytic response was assessed via concentrations of D-dimer, plasminogen, and α-2-antiplasmin (plasmin inhibitor). Results-Substantial hemostatic and fibrinolytic activation was evident after surgery in both groups, as characterized by significantly increased global clot strength and an overall hypercoagulable state at 4 hours after surgery in addition to decreases in von Willebrand factor antigen and factor VIII concentrations and shortened prothrombin and thrombin times. The dogs also typically had activation of the fibrinolytic system, as evidenced by increased postoperative concentrations of D-dimer, plasminogen, and plasmin inhibitor. Differences between the 2 groups could not be detected for any variables. Conclusions and Clinical Relevance-Elective surgery with limited tissue trauma induced hemostatic activation in dogs, which led to hypercoagulability after surgery. A difference between the ovariohysterectomy and ovariectomy groups was not detected. Thromboelastography can be used on plasma samples and may be useful for evaluating patterns over time.     

Stability of hemostatic proteins in canine fresh frozen plasma units

Abstract: The stability of hemostatic proteins, including coagulation factors II, VII, VIII, IX, and X and von Willebrand factor (vWf), in canine fresh frozen plasma (FFP) units stored for up to 1 year was studied. Plasma units from 7 donor dogs were subjected to 4 treatments following collection, including storage at −30°C for 3 months, 6 months, and 1 year and storage at −20°C for 6 months. Coagulant factor activity and vWf concentrations were measured at these times. Significant differences between prestorage and poststorage values were noted for factors VIII, IX, and X, and vWf. Differences seemed to be least pronounced for plasma stored for 3 months; however, a significant interaction between prestorage and poststorage differences and the 4 treatment groups could not be demonstrated. On the basis of factor content in the present study, 15–20 mL/kg of FFP stored for up to 1 year was capable of providing approximately 10–15 U/kg of vWf and factors VIII, IX, X, and II, whereas 10 mL/kg FFP provided at least 10 U/kg of factor VII.     

Effect of carprofen on hemostatic variables in dogs

OBJECTIVE: To evaluate the effect of carprofen on hemostatic variables in clinically normal dogs. ANIMALS: 12 clinically normal Labrador Retrievers. PROCEDURE: 10 dogs (6 females, 4 males) received carprofen (2.2 mg/kg of body weight, PO, q 12 h) for 5 days. Two dogs (untreated control group; 1 female, 1 male) did not receive carprofen. Hemostatic variables (platelet count, activated partial thromboplastin time, prothrombin time, fibrinogen, platelet aggregation, and bleeding time) were assessed for all dogs prior to treatment, on day 5 of treatment, and 2 and 7 days after discontinuation of the drug (days 7 and 12). Serum biochemical variables and Hct were assessed prior to treatment and on days 5 and 12. RESULTS: In dogs receiving carprofen, platelet aggregation was significantly decreased, and onset of aggregation was significantly delayed on days 5, 7, and 12, compared with pretreatment values. Activated partial thromboplastin time was significantly increased on days 5, 7, and 12 over pretreatment values in treated dogs, but values remained within reference ranges. Significant differences were not detected in buccal mucosal bleeding time, other serum biochemical and hemostatic variables, or Hct, compared with pretreatment values and the internal control group. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of carprofen for 5 days causes minor but not clinically important alterations in hemostatic and serum biochemical variables in clinically normal Labrador Retrievers. Carprofen is commonly used to treat osteoarthritis and chronic pain in dogs, but prior to this study, its effect on platelet aggregation and hemostatic variables was unknown.     

Activated partial thromboplastin time as a screening test of minor or moderate coagulation factor deficiencies for canine plasma: sensitivity of different commercial reagents.

To determine the sensitivity for detection of coagulation factor deficiencies by commercial reagents for canine plasma, 5 commercial activated partial thromboplastin time (APTT) reagents with different types of contact activator and phospholipid of various origin were examined. Thirty canine plasma samples with minor or moderate deficiencies of coagualition factors that influence the APTT were examined. Significant differences were found for the sensitivity of various reagents, but no correlation was found with the type of contact activator. Following the test instructions provided by the manufacturers, the number of APTT results that were prolonged beyond the reference range varied between 20 and 30 (sensitivity = 0.67-1.00); the number of corresponding results using a standardized test protocol varied between 19 and 28 (sensitivity: 0.63-0.93). The most sensitive reagent contained kaolin as a contact activator and a human placental thromboplastin. The results of this study indicate that the APTT test optimized for human plasma is also a sensitive screening test of the intrinsic system of canine plasma, provided that a suitable reagent is used.     

Western Blot Analysis of Proacrosin/Acrosin in Frozen Dog Sperm During In Vitro Capacitation

Acrosin is an acrosomal protease synthesized as an inactive precursor, proacrosin, which is processed via autoproteolysis into active forms alpha- and beta-acrosin. In this paper, a comparative study on the immunoreactivity of acrosin during in vitro capacitation of frozen and fresh (control) canine sperm using Western blot analysis is reported. Semen samples were obtained by digital stimulation and ejaculates processed as fresh and frozen samples and then capacitated for 0, 30, 60 and 90 min. At each time period, samples were analyzed with monoclonal antibody C5F10 by Western blot. The antibody specifically recognized, in fresh and frozen/thawed spermatozoa, a 40-, 32- and 27-kDa bands corresponding to proacrosin, alpha- and beta-acrosin, respectively, during capacitation. Western immunoblots showed that the beta-acrosin reactivity in fresh sperm was directly proportional to the time of capacitation, whereas a decreased reactivity of active form of acrosin was observed with frozen-thawed sperm (p   < 0.05). These results suggest that proacrosin is activated to beta-acrosin earlier in frozen/thawed dog spermatozoa than in fresh dog spermatozoa.     

Hemostatic and Fibrinolytic Indices in Neonatal Foals with Presumed Septicemia

Thirteen coagulation tests evaluating hemostatic and fibrinolytic indices and serum cytokine and plasma endotoxin concentrations were obtained in 34 foals with a positive sepsis score (septic group) and 46 age-matched healthy foals. Compared to healthy foals, the prothrombin, activated partial thromboplastin, and whole blood recalcification times were significantly longer in septic foals. The fibrinogen and fibrin degradation products concentrations, percent plasminogen, alpha-2 antiplasmin, and plasminogen activator inhibitor activities, and tumor necrosis factor and interleukin-6 activities were greater in septic foals. Protein C antigen and antithrombin III activity were significantly lower in septic foals. Blood cultures were positive for growth and endotoxin was detected in 19 of 29 and 15 of 30 septic foals, respectively. In septicemic foals with detectable endotoxin in the plasma, the prothrombin and activated partial thromboplastin times were significantly longer and the plasminogen and antithrombin III activities were significantly less than in septic foals in which endotoxin was not detected. Twenty-three of the 34 septic foals did not survive. Septic foals that did not survive were most likely to have a positive blood culture in which a gram-negative organism was isolated. Histopathologic evidence of hemorrhage was evident in 11 foals at postmortem examination and thrombosis was identified in 2 foals. The prothrombin time was significantly longer in foals that had multisite hemorrhage at postmortem examination. The results of this study indicate that clinically relevant alternations in hemostatic and fibrinolytic indices occur in neonatal foals with septicemia and that derangements can be correlated with the presence of endotoxin in plasma. Derangements in hemostatic or fibrinolytic indices were helpful in identification of septic foals with increased risk of coagulopathy, but were not helpful in predicting hemorrhage as compared to thrombus formation. Survival of septicemic foals was correlated with gram-negative bacteremia, but not with the presence of endotoxin or coagulopathy.     

Storage stability of some bovine plasma enzymes

Blood samples taken from domestic or wild ruminant animals typically require transportation to an analytical laboratory. Depending on circumstances, several hours or even a few days may pass between sampling and analysis. Several diagnostic plasma enzymes were measured in bovine blood samples immediately after sampling and after storage under a variety of conditions. Conditions studied included storing whole heparinized blood at 20 C for 6 hours, storage at 4 C for 3 and 5 days, and freezing freshly prepared plasma once and 4 times before analysis. For studies of erythrocyte enzymes, fresh erythrocytes were compared with erythrocytes frozen once, frozen 4 times, and prepared from whole blood stored for one week at 4 C. None of these conditions deteriorated erythrocyte acetylcholinesterase. The serum pseudoacetylcholinesterase and lactate dehydrogenase were not affected by any storage condition used. By contrast, acid phosphatase was significantly decreased by all storage conditions used. Ornithine carbamoyltransferase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase were stable under some of the storage conditions tested.     

Heparin in vitro sensitivity of the activated partial thromboplastin time in canine plasma depends on reagent.

The in vitro heparin sensitivity of 6 different commercial activated partial thromboplastin time (APTT) reagents was investigated based on artificial plasma samples prepared by addition of sodium heparin at different activities (0-1.5 IU/ml) to pooled normal canine plasma. Statistical analysis using 2-way analysis of variance was based on APTT ratios (APTT/mean APTT control). Significant differences between the APTT ratios of different APTT reagents (P < 0.00001) were found, which also depended on heparin activity (interaction between the factors; P < 0.00001). For example, mean APTT ratio at 0.7 IU/ml heparin varied between 1.2 and 2.5. The results of this study indicate that recommendations for the control of heparin therapy in dogs by APTT ratio should be reagent specific.