Viper Envenoming: Evaluation of Treatment by Restoration of Haemostasis and Venom Clearance

Abstract

Treatment of systemic envenoming in snakebite victims has, in the past, depended almost entirely on the individual clinician's experience in assessing the severity of envenoming. The efficacy of treatment is obviously related to the neutralising potency of the antivenom used, the route by which it is administered and the dose. The use of techniques for evaluating the efficacy of antivenoms has proved to be very useful, as an adjunct to recognised clinical observations, for a more objective evaluation of antivenom efficacy and dosage. In patients bitten by many vipers, including the Brazilian pit vipers, the reversal of the venom-induced coagulopathy provides an ideal indicator as to the efficacy of an antivenom. Likewise, the development of enzyme immunoassay has permitted us to estimate levels of circulating specific venom and antivenom levels at any time after the bite in the patient's blood; the efficacy of an antivenom can thus be objectively assessed by measuring the neutralisation and clearance of venom antigen. In Brazil, it appears that clinicians treat patients with excessive amounts of highly efficient antivenoms, which results in an unacceptably high incidence of reactions. In Sri Lanka, the use of imported Indian antivenom is relatively ineffective in neutralising the procoagulant and other effects of the venoms of Sri Lankan snakes, demonstrating the real problem of venom variability within individual species. In West Africa, the improved restoration of blood coagulability, the resolution of haemorrhagic disturbances and the increased rate of clearance of venom following treatment of Echis victims with a monospecific as opposed to a polyspecific antivenom has been demonstrated, and new smaller fragment Fab antivenoms have been developed and are now under clinical assessment. Such clinically based coagulation and immunological studies should result in more efficient and controlled use of expensive antivenoms for treatment of systemic envenoming and the accurate assessment of newly designed products. Such studies also emphasise the importance of individual countries producing their own antivenoms for treatment of systemic envenoming. Likewise, the use of such objective systems now enable us to assess the use of first aid measures such as tourniquets

Bite-to-hospital time and morbidity in victims of viper bite in a rural hospital in Nigeria

“…On presentation all patients had 2 ml of venous blood withdrawn and put inside a glass tube 12 for whole-blood clotting test by the method already described by Warrell et al 13 – 15 Those with non-clotting blood after 20 minutes were given 10 ml of monospecific ovine Fab snake antivenom by intravenous route. The time at which the patient was bitten by the snake was obtained from the patient and/or at least two other care-givers.…”

Appropriate antivenom doses for six types of envenomations caused by snakes in taiwan

“…Additionally, new assay systems allow a very accurate assessment of antivenom efficacy, apart from changes in a patient clinical status (15). Though we may agree that improvements in quality, efficacy and consistency have resulted from enhanced methods of antivenom production, appropriate dosage and treatment duration are still decisive, and are based on clinician assessment of the patient condition.…”

Fatores associados à incoagulabilidade sangüínea no envenenamento por serpentes do gênero Bothrops

“…Embora alguns autores considerem que não haja dados convincentes de que o torniquete possa retardar a absorção do veneno 53 , se isso for possível, a demora que acarretaria na difusão do veneno para os tecidos a jusante e para a corrente sangüínea, entre os pacientes em uso de torniquete poderia propiciar que fossem tratados com a soroterapia específica e ter o veneno neutralizado antes mesmo do sangue tornarse incoagulável. Isso explicaria o fato daqueles que usaram torniquete terem apresentado menor freqüência de incoagulabilidade sangüínea.…”