Changes in the blood coagulation profile after ovariohysterectomy in female dogs

This study investigated changes in the coagulation profile of 10 healthy female dogs subjected to ovariohysterectomy. Blood samples were collected three times--before, directly after and 24 h after surgery. Plasma samples were analyzed to determine thrombin time (TT), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen content, D-dimer content and antithrombin (AT) III activity. The results revealed post-operative haemostatic system disorders related to prolonged APTT, higher fibrinogen and D-dimer concentrations and lower levels of AT III activity.     

Effect of desmopressin on plasma factor VIII and von Willebrand factor concentrations in Greyhounds

Objective To determine the effect of 1-Deamino-8-D-argi-nine vasopressin on plasma concentrations of von Willebrand factor and factor VIII in Greyhound blood donors, and to compare the response of 1-Deamino-8-D-arginine vaso-pressin injection on plasma concentrations of von Willebrand factor between groups with different resting plasma concentrations of von Willebrand factor.
Animals Fifteen Greyhound blood donors were used. Dogs were grouped into three categories depending on their von Willebrand factor concentrations.
Procedure Desmopressin was administered subcuta-neously at 1 mg/kg to all dogs. Plasma von Willebrand factor and factor VIII concentrations were measured before and 10, 20, 30, 45, 60, 90 and 120 min after desmopressin injection.
Results The von Willebrand factor and factor VIII concentrations in all dogs increased significantly and remained higher than base-line throughout the 2 h period.
Conclusion Desmopressin is useful in increasing von Willebrand factor concentrations in Greyhound blood donors, including those with low resting concentrations.     

Plasma D-dimer for the diagnosis of thromboembolic disorders in dogs.

D-dimer is formed during thrombus formation when factor XIIIa crosslinks the terminal D-domains of fibrin. The D-dimer epitope is exposed when the thrombus is lysed by plasmin. Thus, D-dimer represents both thrombin and plasmin activation and is specific for fibrinolysis. D-dimer concentrations are increased in dogs with DIC or other thromboembolic disorders, but because D-dimer is an indicator of physiologic or pathologic fibrinolysis, values are elevated in other conditions associated with fibrinolysis, including orthopedic surgery, neoplasia, and internal hemorrhage. It can be used as an ancillary test for the diagnosis of DIC but is not recommended as a sole test for this purpose. D-dimer has the potential to be a useful laboratory test for the detection of pulmonary thromboembolism in dogs. Further studies are needed to determine the appropriate applications for this test in veterinary patients to aid in clinical decision making, treatment, and patient care.     

Preoperative and postoperative hemostatic profiles of dogs undergoing ovariohysterectomy.

Hemostatic profiles were evaluated in 15 healthy dogs immediately before and 24 hours after celiotomy for routine ovariohysterectomy. Prothrombin time, activated partial thromboplastin time, fibrinogen, fibrin degradation products, antithrombin III activity, platelet count, and hemogram were measured. There were no significant changes in prothrombin time, activated partial thromboplastin time, fibrin degradation products, antithrombin III activity, or platelet count. Fibrinogen concentration was significantly higher following surgery. Postoperative leukocyte differential counts were typical of stress leukograms, and were characterized by leukocytosis, neutrophilia, lymphopenia and eosinopenia. Mild decreases in packed cell volume, red blood cell count and hemoglobin concentration were consistent with minor blood loss during surgery or fluid retention and hemodilution postoperatively. It was concluded that celiotomy and routine ovariohysterectomy in healthy dogs did not alter hemostatic profiles 24 hours after surgery. Abnormal postoperative hemostatic profiles should not be attributed to surgery alone; other causes of abnormal hemostatic profiles should be investigated.     

Diagnostic Approach to Small Animal Bleeding Disorders

A well-designed and executed diagnostic approach to patients with bleeding disorders is critical to determine disease etiology and guide therapeutic measures. This systematic process begins with a comprehensive history and physical examination, followed by laboratory tests of primary hemostasis (platelet enumeration, platelet function testing, and von Willebrand factor assays), secondary hemostasis (prothrombin time, activated partial thromboplastin time, activated clotting time, and individual factor deficiencies), and fibrinolysis (fibrinogen activity, thrombin time, fibrin degradation products, D-dimers), dependent on the clinical picture. Equally valuable are proper specimen collection, handling, and storage methods, which provide reliable and reproducible result interpretation. This review will emphasize the common diagnostic tools and blood sampling techniques important to the workup of hemostatic diseases as well as provide an overview of advanced clinical and research methods and equipment available to assist our bleeding veterinary patients, including thromboelastography/thromboelastometry, calibrated automated thrombogram, and the thrombin-antithrombin assay.     

Failure of sodium pentobarbital anesthesia to alter 1-desamino-8-D-arginine vasopressin-induced elevations of plasma factor VIII/ von Willebrand factor in normal dogs.

The vasopressin analog 1-desamino-8-D-arginine stimulates elevations in plasma Factor VIII/ von Willebrand factor in normal dogs. In order to study the effects of general anesthesia on this response, six dogs were anesthetized with sodium pentobarbital or given an equivalent amount of saline then challenged with an intravenous dose of 1-desamino-8-D-arginine (0.6 micrograms/kg body weight). Factor VIII coagulant activity, von Willebrand factor antigen, and ristocetin cofactor activity were quantitated before anesthesia (or saline infusion), 20 min after induction (pre-1-desamino-8-D-arginine), and at 30 and 60 min post-1-desamino-8-D-arginine. Anesthesia did not significantly affect the elevations in plasma Factor VIII/ von Willebrand factor induced by 1-desamino-8-D-arginine. Sodium pentobarbital appeared however to prevent the rise in Factor VIII coagulant activity seen following saline treatment. The results of this study suggest that when 1-desamino-8-D-arginine is to be used in normal dogs to boost basal plasma von Willebrand factor levels, it is not necessary to administer it prior to induction of general anesthesia with sodium pentobarbital.     

Coagulation profiles in dogs with congenital portosystemic shunts before and after surgical attenuation

BACKGROUND: Serious postoperative hemorrhage has been reported in dogs after closure of congenital portosystemic shunts (CPS). HYPOTHESIS: In dogs with portosystemic shunting, low coagulation factor activity is responsible for coagulopathy, which can cause complications after surgery. ANIMALS: Thirty-four dogs with CPS and 39 healthy dogs. METHODS: In a prospective study, coagulation times, platelet count, and the activity of 8 coagulation factors were measured in dogs before and after surgical shunt attenuation and in 31 healthy dogs. The effect of abdominal surgery on hemostasis was determined at ovariectomy in 8 healthy dogs. RESULTS: Dogs with CPS had lower platelet counts, lower activity of factors II, V, VII, and X, and increased factor VIII and activated partial thromboplastin time (APTT) compared to healthy dogs. After surgical attenuation, dogs with CPS had decreased platelet counts and activity of factors I, II, V, VII, IX, X, and XI and a prolonged prothrombin time (PT). Ovariectomy resulted in decreased activity of factors VII and X. Six weeks after surgery, portosystemic shunting persisted in 9 of 30 dogs, with no improvement of hemostatic values. CPS dogs without shunting had improved coagulation times and increased activity of factors II, V, VII, and X. CONCLUSIONS AND CLINICAL IMPORTANCE: Dogs with CPS have lower activity of clotting factors compared to healthy dogs, resulting in a prolonged APTT. Surgical attenuation of the shunt results in increased abnormalities in coagulation times and factors immediately after surgery. Hemostasis is normalized after complete recovery of shunting after attenuation, in contrast to dogs with persistent shunting.     

Ontogeny of bovine hemostasis

Ontogeny of selected hemostatic system components was studied in 120 bovine fetuses which had been divided into eight monthly gestational age groups. Fetal blood was subjected to the following tests: platelet count, partial thromboplastin time, prothrombin time, thrombin time, fibrinogen quantitation, and assays for prothrombin and factors V and VIII. Platelet numbers corresponding to adult numbers were in fetal blood at least as early as gestation day 60, and their numbers varied only slightly thereafter. Bovine blood was incapable of in vitro coagulation at gestation day 90, with all samples coagulating by gestation day 150. Fetal coagulation screening test times (partial thromboplastin time, prothrombin time, and thrombin time) shortened during gestation and were near times of adults at birth. Of the four individual coagulation factors tested, only factor VIII reached adult values in the fetus in utero. Amounts of fibrinogen, prothrombin, and factors V and VIII in the neonate exceeded that of normal adult cattle.     

Effect of acepromazine, xylazine and thiopentone on factor VIII activity and von Willebrand factor antigen concentration in dogs

The effect of acepromazine maleate, xylazine and thiopentone on the packed cell volume, plasma protein content, factor VIII activity and von Willebrand factor antigen concentration of blood was studied in normal dogs. The same variables were measured in dogs with haemophilia A given acepromazine maleate and thiopentone. Both the packed cell volume and plasma protein content decreased after the administration of either acepromazine maleate or xylazine. Values were not changed further after administration of thiopentone. Changes in the haemostatic variables measured were generally small. Consequently, blood samples collected from dogs under the influence of premedicant doses of acepromazine maleate or xylazine, and when subsequently anaesthetised with thiopentone, are adequate for the assay of factor VIII activity and von Willebrand factor antigen concentration for establishing an animal's haemophilia A and von Willebrand's disease status.     

Evaluation of human recombinant tissue factor-activated thromboelastography in 49 dogs with neoplasia

BACKGROUND: Abnormal routine coagulation assay results have been reported to be common in veterinary patients with neoplasia, but the overall hemostatic functional state, including hypercoagulability, has not been described. HYPOTHESIS: The overall hemostatic functional state, including hypercoagulability, can be assessed in dogs with neoplasia by tissue factor (TF)-activated thromboelastography (TEG). ANIMALS: Thirty-six dogs with malignant neoplasia and 13 dogs with benign neoplasia presented to the Small Animal Veterinary Teaching Hospital, The University of Copenhagen, Frederiksberg, Denmark. METHODS: Prospective study evaluating the overall hemostatic functional state in dogs with neoplasia by a newly validated TF-activated TEG assay and routine coagulation parameters activated partial thromboplastin time (aPTT), prothrombin time (PT), platelet count, and D-dimer concentration. RESULTS: Hemostatic dysfunction was observed in 28/49 (57%) dogs with neoplasia. Twenty-four were dogs with malignant neoplasia, the majority of which 18/36 (50%) were hypercoagulable, whereas 6/36 (17%) were hypocoagulable. All hypocoagulable dogs had metastatic disease. The proportion of dogs with altered hemostasis was significantly different between dogs with malignant and benign neoplasia. CONCLUSIONS AND CLINICAL IMPORTANCE: TF-activated TEG detected hypercoagulable and hypocoagulable states in this population of dogs with neoplasia. The most common hemostatic abnormality in dogs with malignant neoplasia was hypercoagulability. These findings suggest that this novel hemostatic function test may be of value as a cage side method for the assessment of overall hemostatic function in dogs with cancer, including the detection of both hyper- and hypocoagulable states as well as mixed disorders.     

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.     

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.     

Effects of oxypolygelatin and dextran 70 on hemostatic variables in dogs

Objective To evaluate and compare coagulation variables following the administration of oxypolygelatin and dextran 70 to clinically healthy dogs. Study design Randomized cross‐over experimental study. Animals A total of eight healthy adult female Beagles aged 2–4 years old and weighing 11.8 ± 2.7 kg. Methods The dogs received a 15‐minute intravenous (IV) infusion of 5 mL kg^?1 oxypolygelatin or 10 mL kg^?1 6% dextran 70. Before (PRE) and at 2, 5, and 24 hours after administration, packed cell volume (PCV), total solids concentration (TS), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration (FIB), platelet numbers (Plat), factor VIII coagulant activity (VIII:C), von Willebrand factor antigen concentration (vWf:Ag) and platelet function and buccal mucosal bleeding time (BMBT) were measured. Platelet function was assessed using aggregation and by measuring ATP release from aggregating platelets over 6 minutes, with 20, 10, and 5 µm ADP and 5 and 10 µg of collagen mL^?1 as platelet activation agonists. Results All baseline values were within our normal ranges, except for one dog that had low vWf:Ag PRE values prior to both dextran and oxypolygelatin administration. Following dextran and oxypolygelatin administration, the PCV and TP were significantly (p < 0.05) decreased. Plat, FIB, and vWf:Ag decreased, while BMBT and VIII:C increased following dextran administration. Dextran also caused a significant decrease in platelet aggregation in response to ADP. Oxypolygelatin caused a significant decrease in vWf:Ag, Plat, and FIB compared to PRE values. The total amount of ATP released, standardized to platelet number, did not vary significantly for either group at any sampling time from PRE values. No significant changes from PRE values were noted at any time in either group for PT or APTT. Conclusion At the doses administered, both dextran and oxypolygelatin can interfere with hemostatic variables in healthy dogs, but dextran's effect is more profound and prolonged when compared to oxypolygelatin. Clinical relevance Oxypolygelatin causes fewer hemostatic abnormalities when compared to dextran, making it a superior colloid for administration at the doses tested.     

Exercise induced hypercoagulability,increased von Willebrand factor and decreased thyroid hormone concentrations in sled dogs

Background

Sled dogs performing endurance races have been reported to have a high incidence of gastric erosions or ulcerations and an increased risk of gastro intestinal bleeding leading to death in some cases. In addition, these dogs also become hypothyroid during training and exercise. Canine hypothyroidism has been shown to correlate with decreased von Willebrand factor antigen and potentially increased bleeding tendency. Whether increased gastro intestinal bleeding risk is exacerbated due to changes in the hemostatic balance is unknown. The aim of this study was to investigate the hemostatic balance in sled dogs before and after exercise and in addition evaluate any correlation to thyroid status. Twenty sled dogs have been assessed in untrained and trained condition and immediately after exercise. The first sample was collected in the autumn following a resting period, and subsequently the dogs were exposed to increased intensity of training. After four months the peak of physical condition was reached and a 68 km long sled pulling exercise was performed. Samples were collected before and immediately after the exercise. Evaluated parameters were: plasma thromboelastographic (TEG) R, SP, α and MA, activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, von Willebrand factor (vWf), D-dimer, platelet number, thyroid hormones, hematocrit and C-reactive protein (CRP).

Results

Exercise induced an overall hypercoagulable state characterized by significant decreases of TEG R and SP and an increase of α, increased concentrations of plasma vWf and decreased aPTT. In addition, a proinflammatory status was seen by a significant increase of serum CRP concentrations. Thyroid status was confirmed to be hypothyroid as training and exercise induced significant decrease of thyroxin (T4), free thyroxin (fT4) and thyroxin stimulating hormone (TSH) concentrations. Fibrinogen decreased significantly and PT increased. The training-induced changes showed correlation between T4, fT4 and aPTT and correlation between TSH and fibrinogen. Exercise-induced changes showed correlation between T4 and PT.

Conclusions

Exercise was associated with a hypercoagulable state and an increase of vWf concentration in this group of sled dogs. Decreased thyroid hormone concentrations after training and exercise were confirmed, but were associated with increased and not decreased vWf in this group of sled dogs.     

Effects of 6% hetastarch (600/0.75) or lactated Ringer's solution on hemostatic variables and clinical bleeding in healthy dogs anesthetized for orthopedic surgery

ObjectiveTo evaluate and compare hemostatic variables and clinical bleeding following the administration of 6% hetastarch (600/0.75) or lactated Ringer’s solution (LRS) to dogs anesthetized for orthopedic surgery.Study designRandomized blinded prospective study.AnimalsFourteen, healthy adult mixed-breed hound dogs of either sex, aged 11–13 months, and weighing 20.8 ± 1.2 kg.MethodsThe dogs were randomly assigned to receive a 10 mL kg^?1 intravenous (IV) bolus of either 6% hetastarch (600/0.75) or LRS over 20 minutes followed by a maintenance infusion of LRS (10 mL kg^?1hour^?1) during anesthesia. Before (Baseline) and at 1 and 24 hours after bolus administration, packed cell volume (PCV), total protein concentration (TP), prothrombin time (PT), activated partial thromboplastin time (APTT), von Willebrand’s factor antigen concentration (vWF:Ag), factor VIII coagulant activity (F VIII:C), platelet count, platelet aggregation, colloid osmotic pressure (COP) and buccal mucosal bleeding time (BMBT) were measured. In addition a surgeon who was blinded to the treatments assessed bleeding from the incision site during the procedure and at 1 and 24 hours after the bolus administration.ResultsFollowing hetastarch or LRS administration, the PCV and TP decreased significantly 1-hour post-infusion. APTT did not change significantly compared to baseline in either treatment group, but the PT was significantly longer at 1-hour post-infusion than at 24 hours in both groups. No significant change was detected for vWF:Ag, FVIII:C, platelet aggregation or clinical bleeding in either group. The BMBT increased while platelet count decreased significantly at 1-hour post-infusion in both groups. The COP decreased significantly in both treatment groups 1-hour post-infusion but was significantly higher 1-hour post-infusion in the hetastarch group compared to the LRS group.Conclusions and clinical relevanceAt the doses administered, both hetastarch and LRS can alter hemostatic variables in healthy dogs. However, in these dogs undergoing orthopedic surgery, neither fluid was associated with increased clinical bleeding.     

Von Willebrand's disease in dogs in the United Kingdom

An assay for the measurement of von Willebrand factor antigen has been established. In a period of 18 months, 13 dogs have been identified as suffering from von Willebrand's disease. The affected animals had levels of von Willebrand factor antigen which ranged from undetectable to 43 per cent of normal. Factor VIII levels were also reduced. Haemorrhagic episodes were usually associated with trauma or surgery, and often required transfusion with fresh blood or plasma to arrest haemorrhage.     

Hemostatic defects associated with two infusion rates of dextran 70 in dogs.

We investigated changes in hemostatic function after infusion of 6% dextran 70 (high molecular weight dextran) at 2 rates. Six healthy dogs underwent 3 regimens: 20 ml of dextran/kg of body weight administered in 1 hour (trial A), 20 ml of dextran/kg administered in 30 minutes (trial B), and 0.9% sodium chloride solution as a control administered over 1 hour to achieve hemodilution equivalent to that for 20 ml of dextran/kg (trial C). Before and at 2, 4, 8, and 24 hours after the start of trials A and B, we measured PCV, total solids (TS) concentration, amount of von Willebrand factor antigen (vWf:Ag), factor VIII coagulant activity (VIII:C), prothrombin time, activated partial thromboplastin time (APTT), platelet retention in a glass bead column, and buccal mucosa bleeding time (BMBT). Values were not obtained at 8 and 24 hours for trial C. Saline-induced changes in hemostasis were significant (P less than 0.05) from baseline throughout the sample collection period. Significant differences (P less than 0.05) between trial A and control were observed for vWf:Ag, VIII:C, BMBT, APTT, TS, and PCV values at 2 hours, and for VIII:C at 4 hours. Significant differences (P less than 0.05) between trial B and control were observed for APTT, TS, and PCV values at 2 hours, and for vWf:Ag, VIII:C, BMBT, APTT, TS, and PCV values at 4 hours. During trials A and B, mean values of analytes infrequently deviated from reference intervals, and clinical signs of bleeding were not observed in any dog.(ABSTRACT TRUNCATED AT 250 WORDS)     

DDAVP-induced increases in coagulation factor VIII and von Willebrand factor in the plasma of conscious dogs

Infusion of the vasopressin analogue DDAVP into five normal dogs at doses of 0.1-2.0 micrograms DDAVP per kg body weight induced dose-dependent increases in the plasma content of coagulation factor VIII and von Willebrand factor. Plasma concentrations of von Willebrand factor (determined antigenically as factor VIII-related antigen and functionally as coagglutinin cofactor activity) and coagulation factor VIII were measured immediately before and at 10, 30, and 120 min after 10-min intravenous infusions of DDAVP. The greatest increases in coagulation factor VIII were produced with the 2.0 micrograms/kg dose. Ten minutes after infusion the mean increase in coagulation factor VIII was 32 units/dl (concentrations of all indices were reported relative to concentrations in a standard canine plasma pool, arbitrarily assigned a concentration of 100 units/dl) and this increase did not change significantly throughout the duration of the experiment. At 10 min post-infusion, the mean factor VIII-related antigen concentration increased 81 units/dl (dose = 2.0 micrograms/kg) and did not change significantly for the duration of the experiment. The maximum mean increase in coagglutinin cofactor activity, 141 units/dl, occurred 10 min after infusion (dose = 1.0 microgram/kg). Coagglutinin cofactor activity decreased significantly from peak activity by 120 min post-infusion.     

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.     

Thrombokinetic Studies in Normal and Factor VIII-deficient Canine Plasmas

Thrombokinetograms are graphic depictions of the optical changes occurring in plasma during the clotting process and provide information, not only on the time required for clotting to begin, but also on the way in which the clot forms. We studied thrombokinetic profiles in plasmas from normal dogs, and dogs with varying degrees of factor VIII deficiency. Clotting was induced through intrinsic, extrinsic and common coagulation pathways [activated partial thromboplastin time, prothrombin time and thrombin time, respectively].

The thrombokinetograms for the various clotting tests were qualitatively similar in normal canine plasmas. After activation of the clotting system there was a period in which no change in optical density occurred. This period was represented by the left base line and corresponded to the duration of the clotting time. When fibrin production commenced there was a rapid increase in the rate of optical density change (ΔOD) to a maximum (V_maxΔOD) in time t₁. This was followed by a more gradual reduction in ΔOD in time t₂.

The activated partial thromboplastin time thrombokinetograms for von Willebrand's disease plasmas were characterized by a reduced V_maxΔOD and prolonged t₁. In severe hemophilic plasma [factor VIII coagulant (F VIII:C)<1% of normal] there was a very slow increase in ΔOD following a prolonged left baseline. The V_maxΔOD, t₁ and t₂ could not be determined since a peak was not attained in one minute. The prothrombin and thrombin time thrombokinetograms for von Willebrand's disease plasmas were normal. The prothrombin time thrombokinetogram for hemophilic plasma had a 2X normal V_maxΔOD possibly related to the relatively high fibrinogen concentration of this plasma compared to the normal.

Changes in thrombokinetogram profiles may be of value in studying mild to moderate clotting factor deficiencies particularly where the clotting times are not markedly prolonged.