Haematological evaluation of patients bitten by the jararaca, Bothrops jararaca, in Brazil☆
Introduction
In Brazil, almost 27,000 snake bites are recorded annually (15 cases per 100,000 population), resulting in more than 100 deaths each year (0.4%) and unknown numbers of permanent sequelae. Almost 90% of them are caused by lance-headed vipers (Bothrops and related genera) (Brasil, 2001). In southeastern Brazil, particularly in São Paulo State, Bothrops jararaca is responsible for most (97.5%) of the bites (Ribeiro and Jorge, 1997). People bitten by B. jararaca frequently manifest local effects at the site of the bite (oedema, ecchymoses, blisters and necrosis) and systemic signs of envenoming such as spontaneous bleeding (gingival bleeding, haematuria and epistaxis) and blood incoagulability (Rosenfeld, 1971). Deaths are rare and are usually associated with massive haemorrhage, shock and acute renal failure (Amaral et al., 1985, Amaral et al., 1986; Kouyoumdjian et al., 1991; Milani et al., 1997). Local necrosis is one of the most serious consequences of B. jararaca envenoming, since it may require amputation resulting in permanent disability. Local necrosis and amputation are mostly associated with bites by larger snakes, bites on fingers and legs and use of a tourniquet (Jorge et al., 1999; Ribeiro et al., 2001).
Since most of the snakes responsible are not identified, diagnosis is based on the clinical features. The dose of antivenom administered is usually based on the severity of clinical symptoms and signs on admission to hospital. Patients bitten by Bothrops spp. are classified clinically as mildly, moderately or severely envenomed depending on the extent and rate of spreading of local swelling at the site of bite, the occurrence of bleeding and shock (França and Málaque, 2003), although the prognostic significance of these features has not been tested rigorously. In addition, the detection of circulating venom by enzyme-linked immunosorbent assay (ELISA) has also been used to diagnose and prospectively to assess the severity of Bothrops envenoming (Theakston et al., 1992). Higher circulating venom levels are certainly found in more severe cases (França et al., 2003; Theakston et al., 1992), but the lack of technical skills and the time taken to obtain the results make it impracticable for use in isolated areas where most bites occur. Simple coagulations tests, including the bedside 20 min whole blood clotting test (20WBCT) (Sano-Martins et al., 1994), can be used to diagnose systemic envenoming and to control the dose of antivenom. Likewise, the complete blood count (CBC) of patients is a practicable and relatively inexpensive tool that may guide supportive treatment. Detailed results of CBC have not yet been reported in victims of B. jararaca. We have therefore investigated whether the CBC of patients with clinically “less severe” or “more severe” Bothrops envenoming, before and after antivenom therapy, could be used as an ancillary tool to help physicians to predict the occurrence of complications, such as necrosis.
Section snippets
Patients
The clinical protocol was approved by the hospital ethics committee and all patients gave informed consent to participate in the study (Cardoso et al., 1993). One hundred patients admitted to Hospital Vital Brazil, Instituto Butantan, São Paulo, Brazil, from 1989 to 1991 with a clinical diagnosis of Bothrops envenoming, confirmed in some cases by identification of the dead snake or by ELISA immunodiagnosis, were included in this study (Cardoso et al., 1993). The length of Bothrops snakes
Results
Thirty-eight patients brought the snakes, of which 16 were young and 22 adult specimens (Table 1). The others had a confirmatory diagnosis of Bothrops envenoming based on the detection in blood of specific venom antigen by ELISA (Theakston et al., 1992). Seventy-four patients were classified as “less severely” and 26 as “more severely” envenomed.
Table 1 shows that the use of tourniquets and bites on fingers were more frequently observed in the “more severe” group, and the higher frequency of
Discussion
Several factors such as the use of a tourniquet, site of the bite and length of snake are already known as risk factors for the development of complications in snake bites, especially necrosis (França et al., 2003; Ribeiro et al., 2001). CBC is routinely used by physicians in hospitals to manage the progression of pathological conditions. We used it to evaluate and follow the evolution of complications in victims of Bothrops snake bites.
The progressive slight fall in erythrocytic values up to 48
Acknowledgements
Financial support for the project was obtained from the Science and Technology for Development Programme of the European Community, Contract no. TS2-0045-UK. Antivenoms used were donated by the manufactures. I.S.S.M was a recipient of CNPq fellowship (No. 304035/2004).
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Ethical statement: The authors warrant that the manuscript is an original work, it has not been published before and it was not submitted for publication anywhere. It contains no libelous or other unlawful statements, and it does not infringe on the rights of others. The authors have no relationship with any manufacturers or distributors of products used in this manuscript. This paper reflects our own research and analysis and does so in a truthful and complete manner. All authors have contributed significantly to the execution, analysis and writing of the study reported and co-authors have agreed to submit the manuscript to Toxicon. Besides, the manuscript is appropriately placed in the context of prior and existing research.
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BIASG: Butantan Institute Antivenom Study Group: J.L.C. Cardoso, H.W. Fan, F.O.S. França, M.T. Jorge, R.P. Leite, S.A. Nishioka, A. Avila, I.S. Sano-Martins, S.C. Tomy, M.L. Santoro, A.M. Chudzinski, S.C.B. Castro, A.S. Kamiguti, E.M.A. Kelen, M.H. Hirata, R.M.S. Mirandola, R.D.G. Theakston and D.A. Warrell.