Effects of intravenous administration of tranexamic acid on hematological, hemostatic, and thromboelastographic analytes in healthy adult dogs

Evaluation of Therapeutic Use of Antifibrinolytics in Cats

Limited data are available regarding the use of the antifibrinolytic drugs tranexamic acid (TXA) and epsilon aminocaproic acid (EACA) in cats. This study aimed to evaluate the indications for the use of TXA and EACA in cats and to describe dosing regimens used, occurrence of adverse events, and patient outcomes. This was a retrospective multicenter study. Medical databases were searched for feline patients billed for TXA or EACA between 2015 and 2021. Thirty-five cats met the inclusion criteria; 86% received TXA and 14% received EACA. The most common indication was nontraumatic hemorrhage (54%), followed by traumatic hemorrhage (17%) and elective surgery (11%). The median dose was 10 mg/kg for TXA and 50 mg/kg for EACA. Overall, 52% of cats survived to discharge. Potential adverse events were noted in 7/35 (20%) patients. Of these, 29% survived to discharge. No standardized dosing regimen was identified; rather, dose, dosing interval, and duration of administration varied markedly between patients. Administration was potentially associated with severe adverse events, although the retrospective design makes it difficult to establish a causal association with antifibrinolytic use. This study provides a base for future prospective studies by giving an insight into the use of antifibrinolytic drugs in cats.

Retrospective analysis of the use of tranexamic acid in critically ill dogs and cats (2018-2019): 266 dogs and 28 cats

OBJECTIVE

To describe the signalment, dosing, adverse events, and patient diagnosis for dogs and cats admitted to the critical care unit (CCU) receiving tranexamic acid (TXA).

DESIGN

Case series from 2018 to 2019.

SETTING

Private referral and primary care veterinary hospital.

ANIMALS

Two hundred and sixty-six dogs and 28 cats.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Records of dogs and cats admitted to the CCU that received TXA were evaluated. A diagnosis was assigned to each patient based on the International Statistical Classification of Diseases system. "Neoplasia" ([most frequently] hemangiosarcoma) (89/226 [39%]) and "diseases of the blood and blood forming organs" (idiopathic hemoabdomen, pericardial effusion) (78/226 [34%]) were the most common disease processes for which dogs received TXA. In cats, "diseases of the blood and blood forming organs" (idiopathic hemoabdomen) (9/28 [32%]), "neoplasia" (hemangiosarcoma, mast cell tumor, carcinoma) (7/28 [25%]), and "injury, poisoning, or certain other consequences of external causes" (high-rise syndrome) (5/28 [17%]) were most common. One hundred and forty-eight dogs (65%) and 13 cats (46%) underwent an invasive procedure during hospitalization. Thirty percent (70/226) of dogs received a packed RBC (pRBC) transfusion. Administration of TXA before or after pRBC transfusion did not significantly affect median dose of pRBC administered (P = 0.808). The median IV dose of TXA was similar for dogs and cats at 10 mg/kg. One cat received a 10 times overdose of TXA and did not suffer any appreciable adverse effects. Adverse events were reported in 1.7% (4/226) of dogs including hypersalivation (3/226) and seizure (1/226) in a dog that received a cumulative dose of 280 mg/kg of TXA. Hypersalivation was the only adverse event reported in 3% (1/28) of cats.

CONCLUSION

TXA is primarily utilized in critically ill dogs and cats diagnosed with neoplasia, bleeding disorders, and trauma at this institution. Adverse events were infrequent and largely mild.

Diagnosis of primary hyperfibrinolysis and in vitro investigation of the inhibitory effects of tranexamic acid in a group of dogs with sarcomas - A pilot study

Primary hyperfibrinolysis is not well characterised in canine cancer. This prospective case-control pilot study aimed to evaluate tissue plasminogen activator-modified thromboelastography (tPA-TEG) for diagnosis of primary hyperfibrinolysis in dogs with cancer and establish the in vitro therapeutic concentration of tranexamic acid (TXA). Nine dogs with sarcomas and normocoagulable thromboelastograms and 11 healthy dogs were included. For each a whole blood tPA-TEG, and four tPA-TEGs with added TXA in different concentrations were analysed. Lysis percentage at 30/60 min following maximal amplitude (LY30/60), clot lysis index (CL30/60), maximum rate of lysis (MRL), and total lysis (L) were investigated as diagnostic parameters of primary hyperfibrinolysis. In vitro TXA concentrations needed to inhibit 50% (IC50) and 90% (IC90) of the fibrinolytic potential were compared between groups. Significant primary hyperfibrinolysis (LY30 (P = 0.0001), LY60 (P = 0.003), CL30 (P = 0.01), and L (P = 0.02)) was observed in dogs with sarcomas. IC50 and IC90 of in vitro TXA for normalizing LY30 were 13.34 (SE 1.52) and 31.10 (SE 3.01) mg/L for dogs with sarcomas and 4.41 (SE 5.84) and 20.00 (SE 6.18) mg/L for healthy dogs. IC50 and IC90 for normalizing LY60 were 22.18 (SE 1.27) and 58.94 (SE 5.47) mg/L for dogs with sarcomas and 11.25 (SE 2.82) and 56.20 (SE 11.61) mg/L for healthy dogs. The IC50 for LY60 was significantly increased for dogs with sarcomas (P = 0.0003). Primary hyperfibrinolysis was documented by tPA-TEG in dogs with sarcomas. In vitro IC50 and IC90 for TXA were established. Clinical studies are required to establish therapeutic dosages in vivo.

Lessons Learned From the Battlefield and Applicability to Veterinary Medicine-Part 1: Hemorrhage Control

In humans, the leading cause of potentially preventable death on the modern battlefield is undoubtedly exsanguination from massive hemorrhage. The US military and allied nations have devoted enormous effort to combat hemorrhagic shock and massive hemorrhage. This has yielded numerous advances designed to stop bleeding and save lives. The development of extremity, junctional and truncal tourniquets applied by first responders have saved countless lives both on the battlefield and in civilian settings. Additional devices such as resuscitative endovascular balloon occlusion of the aorta (REBOA) and intraperitoneal hemostatic foams show great promise to address control the most difficult forms (non-compressible) of hemorrhage. The development of next generation hemostatic dressings has reduced bleeding both in the prehospital setting as well as in the operating room. Furthermore, the research and fielding of antifibrinolytics such as tranexamic acid have shown incredible promise to ameliorate the effects of acute traumatic coagulopathy which has led to significant morbidity and mortality in service members. Advances from lessons learned on the battlefield have numerous potential parallels in veterinary medicine and these lessons are ripe for translation to veterinary medicine.

Prospective, controlled, blinded, randomized crossover trial evaluating the effect of maropitant versus ondansetron on inhibiting tranexamic acid-evoked emesis

OBJECTIVE

To evaluate the incidence of tranexamic acid (TXA)-induced nausea and vomiting after the prophylactic use of 2 antiemetics, ondansetron and maropitant, compared with saline.

DESIGN

Prospective, blinded, placebo-controlled, randomized, crossover study.

SETTING

University research facility.

ANIMALS

Eight adult, purpose-bred Beagles.

INTERVENTION

Dogs received 3 treatments on 3 occasions with a 3-week washout period. Either maropitant (1 mg/kg), ondansetron (0.2 mg/kg), or saline solution was given intravenously in equal volumes, followed 10 minutes later by 50 mg/kg IV TXA. A blinded observer evaluated the dogs for signs of vomiting and nausea for 30 minutes. The severity of nausea was assessed with a visual analog scale (VAS) and recorded at baseline before TXA, and at the end of 3 observational periods: 0-5, 5-15, and 15-30 minutes after TXA. A generalized linear mixed effect model was used to assess for group and period effects. Statistical significance was set at P < 0.05 .

MEASUREMENTS AND MAIN RESULTS

None of the dogs vomited after maropitant. Emesis occurred in 5 out of 8 dogs (62.5%), a median (range) of 1 time (1-2) after ondansetron and 1 time (1-3) after saline. There was a significant effect on vomiting of maropitant against saline (P < 0.0001) but not for ondansetron against saline (P = 0.53). The highest nausea VASs were recorded during the first 5 minutes after TXA with a significant reduction of VAS variability in the maropitant group (P = 0.003). The effect of maropitant and ondansetron against saline on the severity of nausea was not statistically significant (P = 0.069).

CONCLUSION

The neurokinin 1 receptor antagonist maropitant at the dose used, administered IV 10 minutes before 50 mg/kg TXA, was effective in preventing vomiting compared with ondansetron and placebo. Our results support the prophylactic IV administration of maropitant in dogs that are scheduled to receive TXA.

A review of hyperfibrinolysis in cats and dogs

The fibrinolytic system is activated concurrently with coagulation; it regulates haemostasis and prevents thrombosis by restricting clot formation to the area of vascular injury and dismantling the clot as healing occurs. Dysregulation of the fibrinolytic system, which results in hyperfibrinolysis, may manifest as clinically important haemorrhage. Hyperfibrinolysis occurs in cats and dogs secondary to a variety of congenital and acquired disorders. Acquired disorders associated with hyperfibrinolysis, such as trauma, cavitary effusions, liver disease and Angiostrongylus vasorum infection, are commonly encountered in primary care practice. In addition, delayed haemorrhage reported in greyhounds following trauma and routine surgical procedures has been attributed to a hyperfibrinolytic disorder, although this has yet to be characterised. The diagnosis of hyperfibrinolysis is challenging and, until recently, has relied on techniques that are not readily available outside referral hospitals. With the recent development of point-of-care viscoelastic techniques, assessment of fibrinolysis is now possible in referral practice. This will provide the opportunity to target haemorrhage due to hyperfibrinolysis with antifibrinolytic drugs and thereby reduce associated morbidity and mortality. The fibrinolytic system and the conditions associated with increased fibrinolytic activity in cats and dogs are the focus of this review article. In addition, laboratory and point-of-care techniques for assessing hyperfibrinolysis and antifibrinolytic treatment for patients with haemorrhage are reviewed.

Suspected anaphylactic shock associated with administration of tranexamic acid in a dog

A 10-year-old male castrated Maltese was referred with clinical signs of hematuria, stranguria, and pollakiuria. The dog was diagnosed with sterile hemorrhagic cystitis with urethroliths and cystoliths. To remove the uroliths, the dog underwent retrograde urohydropropulsion followed by a cystotomy. The following day, persistent bleeding in the urinary bladder was identified with large hematoma, hematuria and anemia. In order to reduce bleeding, the dog received 10 mg/kg of tranexamic acid (TXA) intravenously. Immediately after TXA administration, the dog developed anaphylactic shock manifested by hypotension, hypothermia, tachycardia and a dull mentation. Thus, an emergency treatment including bolus injection of crystalloid, administration of dexamethasone and diphenhydramine, and oxygen supplementation was given, after which the dog quickly recovered within a few minutes.

Application of thrombelastography (TEG) for safety evaluation of tranexamic acid in primary total joint arthroplasty

BACKGROUND

Questions remain, mainly concerning whether tranexamic acid (TXA) is truly safe since all available trials were underpowered to identify clinically important differences. The objective of this study is to evaluate the safety of TXA by using a novel technique-thromboelastography (TEG).

METHODS

A retrospective review was conducted on 359 consecutive patients who underwent primary total hip arthroplasty (THA) or total knee arthroplasty (TKA) and received multiple-dose or single-dose of TXA at a tertiary academic center. TEG parameters, TEG coagulation status, conventional coagulation test parameters, and incidence of thrombotic events were used for safety evaluation.

RESULTS

Compared with single-dose cohort, patients who received multiple-dose of TXA had consistent statistically significant shortened R times on post-operative day 1 (POD1) and POD3 in both THA (POD1: 4.06 ± 0.71 s versus 4.45 ± 1.28 s, P = 0.011; POD3: 4.36 ± 0.83 s versus 5.12 ± 1.64 s, P < 0.0001) and TKA (POD1: 3.90 ± 0.73 s versus 4.29 ± 0.92 s, P = 0.011; POD3: 4.24 ± 0.94 s versus 4.65 ± 1.07 s, P = 0.023), while the K, α-angle, and MA values were similar during the perioperative period. TEG coagulation status analysis indicated that patients were significantly (P = 0.003) more likely with hypercoagulable status during the course of multiple-dose TXA. Conventional coagulation test parameters were similar. Only one patient developed calf vein thrombosis in the multiple-dose cohort.

CONCLUSIONS

Multiple-dose of TXA was associated with aggravated hypercoagulable state when compared with single-dose of TXA, but this prothrombotic state does not provoke thrombosis when combined with appropriate anticoagulant therapy. Therefore, multiple-dose of TXA remains safe and could be recommended for clinical practice. Potential benefits and possible risks should be trade-off when considering increasing the dosage and frequency of TXA on the present basis.

TRIAL REGISTRATION

ChiCTR1800015422 .

Trauma Management of Military Working Dogs

There are about 2,500 war and military service dogs in service, with about 700 serving at any given time overseas. Military Working Dogs (MWDs) are critical assets for military police, special operations units, and others operating in today's combat environment. The expectation, given the significant combat multiplier impact of these dogs and the intense bond between the handler and dog, is that injured working dogs will receive the same level of care as any injured U.S. military personnel. Veterinary care is available at multiple locations throughout theater, and the veterinary healthcare team is the MWD's primary provider. Yet, human healthcare providers (HCPs) may be the only medical personnel available to MWDs that are gravely ill or injured. As most HCPs are unfamiliar with medical care of dogs, the Joint Trauma System published a Clinical Practice Guideline (CPG), a set of detailed clinical guidelines for managing life-threatening problems of MWDs encountered in combat operations. The CPG is available at the JTS website. This article is covers the most common urgent MWD care challenges HCPs may face.

Pharmacokinetics of tranexamic acid in healthy dogs and assessment of its antifibrinolytic properties in canine blood

OBJECTIVE To assess pharmacokinetics of tranexamic acid (TXA) in dogs and assess antifibrinolytic properties of TXA in canine blood by use of a thromboelastography-based in vitro model of hyperfibrinolysis. ANIMALS 6 healthy adult dogs. PROCEDURES Dogs received each of 4 TXA treatments (10 mg/kg, IV; 20 mg/kg, IV; approx 15 mg/kg, PO; and approx 20 mg/kg, PO) in a randomized crossover-design study. Blood samples were collected at baseline (time 0; immediately prior to drug administration) and predetermined time points afterward for pharmacokinetic analysis and pharmacodynamic (thromboelastography) analysis by use of an in vitro hyperfibrinolysis model. RESULTS Maximum amplitude (MA [representing maximum clot strength]) significantly increased from baseline at all time points for all treatments. The MA was lower at 360 minutes for the 10-mg/kg IV treatment than for other treatments. Percentage of clot lysis 30 minutes after MA was detected was significantly decreased from baseline at all time points for all treatments; at 360 minutes, this value was higher for the 10-mg/kg IV treatment than for other treatments and higher for the 20-mg/kg IV treatment than for the 20-mg/kg PO treatment. Maximum plasma TXA concentrations were dose dependent. At 20 mg/kg, IV, plasma TXA concentrations briefly exceeded concentrations suggested for complete inhibition of fibrinolysis. Oral drug administration resulted in a later peak antifibrinolytic effect than did IV administration. CONCLUSIONS AND CLINICAL RELEVANCE Administration of TXA improved clot strength and decreased fibrinolysis in blood samples from healthy dogs in an in vitro hyperfibrinolysis model. Further research is needed to determine clinical effects of TXA in dogs with hyperfibrinolysis.

A prospective evaluation of oral Yunnan Baiyao therapy on thromboleastographic parameters in apparently healthy dogs

OBJECTIVE

To determine the effect of Yunnan Baiyao (YB) on hemostatic parameters measured by thromboelastography (TEG) in healthy dogs administered 1 capsule of YB orally twice daily for 1 week.

DESIGN

Prospective study of client-owned dogs at a small animal specialty hospital.

SETTING

Private referral center.

ANIMALS

Eighteen client-owned adult dogs weighing at least 15 kg.

INTERVENTIONS

Dogs had a baseline TEG performed and then each dog was administered 1 capsule of YB twice daily by mouth for 1 week and the TEG was reevaluated. Any side effects attributed to YB were noted at this time.

MEASUREMENTS AND MAIN RESULTS

All 18 enrolled dogs completed the study. Dogs that received 1 capsule (250 mg/capsule) of YB orally twice daily had significantly increased G as well as A30 and A60 values. There was also a significantly decreased LY30 and LY60 values after 1 week. The YB appeared well tolerated as only one dog developed mild diarrhea.

CONCLUSIONS

The results of this study suggest that YB at 1 capsule orally twice daily in healthy medium to large breed dogs increases the strength of the clot as measured by TEG and that YB was apparently well tolerated in the study population reported here. Larger prospective studies in different disease states are warranted to further evaluate these preliminary findings.

Phenylephrine use for blood sparing during splenectomy in a dog

A dog with immune-mediated haemolytic anaemia was presented for splenectomy. Phenylephrine administration immediately before the removal of the spleen induced splenic contraction and significantly elevated packed cell volume. This technique conserved red blood cells and may be beneficial in euvolaemic animals to reduce the likelihood of a transfusion being required in the event of surgical haemorrhage.

Safety and efficacy of intravenous administration for tranexamic acid-induced emesis in dogs with accidental ingestion of foreign substances

A prospective observational study was performed in canine clinical medicine to evaluate the emetic action and adverse effects of tranexamic acid. Veterinarians treated 137 dogs with a single dose of tranexamic acid (50 mg/kg, IV) after accidental ingestion of foreign substances. If needed, a second (median, 50 mg/kg; range, 20–50 mg/kg, IV) or third dose (median, 50 mg/kg; range, 25–50 mg/kg, IV) was administered. Tranexamic acid induced emesis in 116 of 137 (84.7%) dogs. Median time to onset of emesis was 116.5 sec (range, 26–370 sec), median duration of emesis was 151.5 sec (range, 30–780 sec), and median number of emesis episodes was 2 (range, 1–8). Second and third administrations of tranexamic acid induced emesis in 64.7 and 66.7% of dogs, respectively. In total, IV administration of tranexamic acid successfully induced emesis in 129 of 137 (94.2%) dogs. Adverse effects included a tonic-clonic convulsion and hemostatic disorder in two different dogs, both of which recovered after receiving medical care. Tranexamic acid induced emesis in most dogs following a single-dose. When a single dose was not sufficient, an additional dosage effectively induced emesis. Overall, adverse effects were considered low and self-limiting.

Hyperfibrinolysis and Hypofibrinogenemia Diagnosed With Rotational Thromboelastometry in Dogs Naturally Infected With Angiostrongylus vasorum

Background

The pathomechanism of Angiostrongylus vasorum infection‐associated bleeding diathesis in dogs is not fully understood.

Objective

To describe rotational thromboelastometry (ROTEM) parameters in dogs naturally infected with A. vasorum and to compare ROTEM parameters between infected dogs with and without clinical signs of bleeding.

Animals

A total of 21 dogs presented between 2013 and 2016.

Methods

Dogs with A. vasorum infection and ROTEM evaluation were retrospectively identified. Thrombocyte counts, ROTEM parameters, clinical signs of bleeding, therapy, and survival to discharge were retrospectively retrieved from patient records and compared between dogs with and without clinical signs of bleeding.

Results

Evaluation by ROTEM showed hyperfibrinolysis in 8 of 12 (67%; 95% CI, 40–86%) dogs with and 1 of 9 (11%; 95% CI, 2–44%) dogs without clinical signs of bleeding (P = .016). Hyperfibrinolysis was associated with severe hypofibrinogenemia in 6 of 10 (60%; 95% CI, 31–83%) of the cases. Hyperfibrinolysis decreased or resolved after treatment with 10–80 mg/kg tranexamic acid. Fresh frozen plasma (range, 14–60 mL/kg) normalized follow‐up fibrinogen function ROTEM (FIBTEM) maximal clot firmness in 6 of 8 dogs (75%; 95% CI, 41–93%). Survival to discharge was 67% (14/21 dogs; 95% CI, 46–83%) and was not different between dogs with and without clinical signs of bleeding (P = .379).

Conclusion and Clinical Importance

Hyperfibrinolysis and hypofibrinogenemia were identified as an important pathomechanism in angiostrongylosis‐associated bleeding in dogs. Hyperfibrinolysis and hypofibrinogenemia were normalized by treatment with tranexamic acid and plasma transfusions, respectively.