Investigation of coagulopathy in three cases of tiger snake (Notechis ater occidentalis) envenomation

Review article: Let us talk about snakebite management: A discussion on many levels

We want to discuss antivenom use in snakebite clinical practice guidelines. Coronial reviews in Victoria of two cases of snakebite envenomation, one described in detail below, prompted us to submit this paper for a wider audience and debate. Venom and antivenom levels were measured in the case detailed below, but not in the other. The coroner received conflicting and varied advice from experts regarding the dose of antivenom. The Victorian Department of Health and Human Services and the Australasian College for Emergency Medicine were instructed to review snakebite management guidelines, particularly with respect to antivenom dosage. The discussion that took place among medical experts led to considerable media attention. We discuss the potential fallout when there is no consensus among medical experts.

A randomized controlled trial of fresh frozen plasma for coagulopathy in Russell's viper (Daboia russelii) envenoming

Essentials Russell's viper envenoming is a major health issue in South Asia and causes coagulopathy. We studied the effect of fresh frozen plasma and two antivenom doses on correcting coagulopathy. Fresh frozen plasma did not hasten recovery of coagulopathy. Low-dose antivenom did not worsen coagulopathy.

SUMMARY

Background Russell's viper (Daboia russelii) envenoming is a major health issue in South Asia and causes venom-induced consumption coagulopathy (VICC). Objectives To investigate the effects of fresh frozen plasma (FFP) and two antivenom doses in correcting VICC. Methods We undertook an open-label randomized controlled trial in patients with VICC at two Sri Lankan hospitals. Patients with suspected Russell's viper bites and coagulopathy were randomly allocated (1 : 1) to high-dose antivenom (20 vials) or low-dose antivenom (10 vials) plus 4 U of FFP. The primary outcome was the proportion of patients with an International Normalized Ratio (INR) of < 2 at 6 h after antivenom administration. Secondary outcomes included anaphylaxis, major hemorrhage, death, and clotting factor recovery. Results From 214 eligible patients, 141 were randomized: 71 to high-dose antivenom, and 70 to low-dose antivenom/FFP; five had no post-antivenom blood tests. The groups were similar except for a delay of 1 h in antivenom administration for FFP patients. Six hours after antivenom administration, 23 of 69 (33%) patients allocated to high-dose antivenom had an INR of < 2, as compared with 28 of 67 (42%) allocated to low-dose antivenom/FFP (absolute difference 8%; 95% confidence interval - 8% to 25%). Fifteen patients allocated to FFP did not receive it. Severe anaphylaxis occurred equally frequently in each group. One patient given FFP developed transfusion-related acute lung injury. Three deaths occurred in low-dose antivenom/FFP patients, including one intracranial hemorrhage. There was no difference in recovery rates of INR or fibrinogen, but there was more rapid initial recovery of factor V and FX in FFP patients. Conclusion FFP after antivenom administration in patients with Russell's viper bites did not hasten recovery of coagulopathy. Low-dose antivenom/FFP did not worsen VICC, suggesting that low-dose antivenom is sufficient.

A randomized controlled trial of fresh frozen plasma for treating venom-induced consumption coagulopathy in cases of Australian snakebite (ASP-18)

BACKGROUND

Venom-induced consumption coagulopathy (VICC) is a major effect of snake envenoming.

OBJECTIVES

To investigate whether fresh frozen plasma (FFP) given after antivenom resulted in more rapid correction of coagulation.

PATIENTS/METHODS

This was a multicenter open-label randomized controlled trial in patients with VICC of FFP vs. no FFP within 4 h of antivenom administration. Patients (> 2 years) recruited to the Australian snakebite project with VICC (International Normalized Ratio [INR] > 3) were eligible. Patients were randomized 2 : 1 to receive FFP or no FFP. The primary outcome was the proportion with an INR of < 2 at 6 h after antivenom administration. Secondary outcomes included time from antivenom administration to discharge, adverse effects, major hemorrhage, and death.

RESULTS

Of 70 eligible patients, 65 consented to be randomized: 41 to FFP, and 24 to no FFP. Six hours after antivenom administration, more patients randomized to FFP had an INR of < 2 (30/41 [73%] vs. 6/24 [25%]; absolute difference, 48%; 95% confidence interval 23-73%; P = 0.0002). The median time from antivenom administration to discharge was similar (34 h, range 14-230 h vs. 39 h, range 14-321 h; P = 0.44). Seven patients developed systemic hypersensitivity reactions after antivenom administration - two mild and one severe (FFP arm), and three mild and one severe (no FFP). One serious adverse event (intracranial hemorrhage and death) occurred in an FFP patient with pre-existing hypertension, who was hypertensive on admission, and developed a headache 6 h after FFP administration. Post hoc analysis showed that the median time from bite to FFP administration was significantly shorter for non-responders to FFP than for responders (4.7 h, interquartile range [IQR] 4.2-6.7 h vs. 7.3 h, IQR 6.1-8 h; P = 0.002).

CONCLUSIONS

FFP administration after antivenom administration results in more rapid restoration of clotting function in most patients, but no decrease in discharge time. Early FFP administration (< 6-8 h) post-bite is less likely to be effective.

Tiger snake (Notechis spp) envenoming: Australian Snakebite Project (ASP-13)

OBJECTIVES

To describe the clinical syndrome associated with definite tiger snake (Notechis spp) envenoming and to examine the ability of tiger snake antivenom (TSAV) to bind free venom in vivo.

DESIGN, SETTING AND PARTICIPANTS

We conducted a prospective cohort study within the Australian Snakebite Project, reviewing all definite tiger snake envenoming cases between October 2004 and June 2011. Definite cases were identified by venom-specific enzyme immunoassay or expert snake identification.

MAIN OUTCOME MEASURES

Clinical effects of tiger snake envenoming; peak venom concentrations; number of vials of antivenom administered.

RESULTS

Fifty-six definite tiger snake envenomings were identified. Clinical effects included venom-induced consumption coagulopathy (VICC) (n = 53), systemic symptoms (n = 45), myotoxicity (n = 11) and neurotoxicity (n = 17). Thrombotic microangiopathy occurred in three patients, all of whom developed acute renal failure. There were no deaths. A bite-site snake venom detection kit test was done in 44 patients, but was positive for tiger snake in only 33 cases. Fifty-three patients received TSAV and eight of these patients had immediate hypersensitivity reactions, severe enough in one case to satisfy diagnostic criteria for severe anaphylaxis. The median peak venom concentration in 50 patients with pretreatment blood samples available was 3.2 ng/mL (interquartile range [IQR], 1-12 ng/mL; range 0.17-152 ng/mL). In 49 patients with post-treatment blood samples available, no venom was detected in serum after the first antivenom dose. Ten patients were given 1 vial of TSAV; the median dose was 2 vials (range, 1-4 vials). Pretreatment serum venom concentrations did not vary significantly between patients given 1 vial of TSAV and those given 2 or more vials.

CONCLUSION

Tiger snake envenoming causes VICC, systemic symptoms, neurotoxicity and myotoxicity. One vial of TSAV, the dose originally recommended when the antivenom was first made available, appears to be sufficient to bind all circulating venom.

Acquired factor VIII deficiency after consuming the dried gallbladder of a cobra, Naja naja

Acquired factor VIII deficiency is very rare, often fatal. It is associated with pregnancy, autoimmune diseases, malignancy, and drugs, although no underlying cause is found in 50%. A 49-year-old male was referred with right shoulder bruising. The coagulation test showed a prolonged activated partial thromboplastin time. The factor VIII level was less than 1%, and the factor VIII inhibitor antibody titer was 246 Bethesda units/mL. The findings were compatible with acquired factor VIII deficiency. He had consumed the dried gallbladder of a cobra, Naja naja, for two weeks, it contained venom. After the initial treatment with factor VIII, he did not take supplemental coagulation factor VIII. The patient was readmitted with left forearm swelling. He lost consciousness suddenly and brain computed tomography (CT) revealed a subdural hematoma. Despite administering recombinant factor VII, his bleeding was not controlled and he died.

The use of therapeutic plasmapheresis in the treatment of poisoned and snake bite victims: An academic emergency department's experiences

The objective of this study is to describe the clinical status, procedural interventions, and outcomes of critically ill patients with poisoning and snake bite injuries presenting to a tertiary-care emergency department for treatment with therapeutic plasmapheresis. Records of 20 patients who presented to our academic emergency department over a 2-year period and who underwent plasmapheresis for poisoning or snake bite were retrospectively reviewed. Plasmapheresis was performed using centrifugation technology via an intravenous antecubital venous or subclavian vein catheter access. Human albumin or fresh frozen plasma were used as replacement fluids. Data extracted from the patient record included demographic data, clinical status, and outcome measures. Sixteen patients underwent plasmapheresis because of toxicity from snake bite. Three patients were treated for drug poisoning (phenytoin, theophylline, bipyridene HCl) and one patient for mushroom poisoning. Haematologic parameters such as platelet count, PT, and INR resolved rapidly in victims of snake bite injuries after treatment with plasmapheresis. Loss of limbs did not occur in these cases. Seven patients required admission to the intensive care unit. One patient with mushroom poisoning died. Mean length of hospital stay was 14.3 days (range 3-28 days) for all cases. Plasmapheresis was a clinically effective and safe approach in the treatment of snake bite envenomation and other drug poisoning victims especially in the management of hematologic problems and in limb preservation/salvage strategies. In addition to established conventional therapies, emergency physicians should consider plasmapheresis among the therapeutic options in treatment strategies for selected toxicologic emergencies.

Characterization of ‘basparin A,’ a prothrombin-activating metalloproteinase, from the venom of the snake Bothrops asper that inhibits platelet aggregation and induces defibrination and thrombosis

A prothrombin activator, named 'basparin A,' was isolated from the venom of the crotaline snake Bothrops asper, the species responsible for the majority of snakebite cases in Central America. It is an acidic (pI 5.4), 70kDa, single chain P-III metalloproteinase comprising, in addition to the metalloproteinase domain, disintegrin-like, and high-cysteine domains. Basparin A is a glycoprotein displaying immunological cross-reactivity with BaH1, a P-III hemorrhagic metalloproteinase isolated from the same venom. It activates prothrombin through the formation of meizothrombin, without requiring additional cofactors; it is, therefore, a class A snake venom prothrombin activator. In contrast with most venom metalloproteinases, it does not degrade components of the extracellular matrix. Apart from its clotting activity, basparin A inhibits collagen-dependent platelet aggregation in vitro, an effect that does not depend on proteolytic activity. Clotting activity on human plasma is not abrogated by the plasma proteinase inhibitors alpha(2) macroglobulin and murinoglobulin, whereas activity is completely inhibited by Costa Rican polyvalent (Crotalinae) anti-venom. Basparin A does not induce local tissue alterations, such as hemorrhage, myonecrosis, and edema, in mice. Moreover, it does not induce systemic hemorrhage, thrombocytopenia nor prolongation of the bleeding time following intravenous administration. At low doses, the only observed effect induced by basparin A, when injected intravenously or intramuscularly into mice, is defibrin(ogen)ation. At higher doses, intravenous administration resulted in sudden death due to numerous occluding thrombi in pulmonary vessels. Basparin A is likely to play an important role in the coagulopathy associated with B. asper envenoming.