Crotaline snake bite in the Ecuadorian Amazon: randomised double blind comparative trial of three South American polyspecific antivenoms
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《英国医生杂志》
1 Hospital Vozandes del Oriente, Shell, Pastaza, Ecuador, 2 Alistair Reid Venom Research Unit, Liverpool School of Tropical Medicine, Liverpool L3 5QA, 3 Ministry of Health, Guayaquil, Ecuador, 4 Fundacion Herpetologica Gustavo Orcés, Quito, Ecuador, 5 Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DU
Correspondence to: D A Warrell david.warrell@clinical-medicine.oxford.ac.u
Abstract
Each year in Ecuador, 1200-1400 cases of snake bite are reported in 19 of the 21 provinces. Reports from Santo Domingo de los Colorados, Guayaquil,1 and Shell2 confirm its importance. In "El Oriente," east of the Andes, the principal venomous species are Bothrops atrox (common lancehead) and B bilineatus smaragdinus (two striped forest pit viper, also known as Bothriopsis bilineata smaragdina). B taeniatus (speckled forest pit viper, also known as Bothriopsis taeniata), the less common Bothrops and Bothrocophias species and Lachesis muta (bushmaster) cause some bites.3 4 The indigenous Amerindian peoples and people of mixed European ethnicity, whose occupations include farming and logging, are all at risk of snake bite. The principal clinical effects of envenoming by B atrox are life threatening bleeding and blood coagulation disorders, shock, and renal failure. Necrosis and bacterial infection at the site of the bite may cause permanent physical handicap. Envenoming by B bilineatus is usually less severe. Other species such as B brazili and L muta, although potentially as dangerous as B atrox, rarely bite people.4
In an earlier preclinical laboratory study, the neutralising potency of five antivenoms (Brazilian, Ecuadorian, Mexican, and two Colombian) was tested against the venoms of B atrox, B asper, and B xanthogrammus.5 6 The Brazilian antivenom proved most effective, followed by the Ecuadorian and two Colombian antivenoms. The Mexican antivenom showed absolutely no neutralising activity against Ecuadorian Bothrops venoms, consistent with its poor clinical reputation in Ecuador.5 We selected the three most effective antivenoms for a double blind randomised comparative clinical trial in Ecuador.
The main lethal effect of the venoms of the crotaline (rattlesnake-like) pit vipers responsible for envenoming is intracranial or gastrointestinal haemorrhage resulting from vascular endothelial damage, platelet dysfunction, and consumption coagulopathy. These dangerous antihaemostatic disorders and their reversal by specific antivenoms are reflected by whole blood coagulability, which is easily assessed at the bedside with a simple but sensitive 20 minute whole blood clotting test.7 8 We therefore used this test to measure the efficacy of the three antivenoms in restoring whole blood coagulability and observed early reactions to assess safety.
Methods
Randomisation and clinical features
We recruited 210 patients with incoagulable blood (fig 1). Eighty seven patients (41.4%) received Colombian INS antivenom, 82 (39%) received Brazilian antivenom, but only 41 (19.5%) received Ecuadorian antivenom because the supply ran out after the 140th patient (table 1). The groups of patients receiving the three different antivenoms were similar in all respects on admission to hospital and before they received treatment (tables 1 and 2). Table 2 shows the clinical features of recruited patients.
Fig 1 Flow of patient through study
Table 1 Comparison of groups of patients bitten by snakes in Ecuador, at randomisation before treatment with antivenom*
Table 2 Clinical features of envenoming in 210 patients bitten by snakes. All had incoagulable blood before randomisation to antivenom therapy*
Snakes responsible for bites
Twenty nine patients (14%) brought in the snake responsible for the bite: 13 (45%) were identified as B atrox, 12 (41%) as B bilineatus smaragdinus, 2 (7%) as B taeniatus, and 2 (7%) remained unidentified (table 1). Specimens of B atrox ranged from 20-90 cm (mean 43 cm, SD 22 cm) and B bilineatus 15-50 cm (34 cm, SD 14 cm) and the two B taeniatus specimens measured 150 cm and 180 cm. With the help of herpetologists and the results of enzyme immunoassay we identified the snake responsible for envenoming in 187 (89%) cases: 109 (58%) were bitten by B atrox, 68 (36%) by B bilineatus, 6 (3%) by B taeniatus, 1 (1%) by B brazili, and 3 (2%) by L muta. The distribution of bites by the different species was similar among the three groups (table 1).
Venom antigen detection
We assessed the serum concentrations of venom antigen from admission to discharge in 148 patients out of the 180 who received an initial dose of 20 ml of antivenom (samples from 32 patients were lost during transport from Shell to Quito). Concentrations on admission correlated significantly with the total volume of antivenom required to restore blood coagulability permanently (P < 0.0001). In the small group of patients who required more than 60 ml of antivenom, median venom antigen concentrations were about fourfold to fivefold higher than those in patients who required only 20 ml of antivenom (fig 2). The time to venom clearance was also longer in patients who required higher doses of antivenom (fig 3).
Fig 2 Relation between median serum concentrations of venom antigen on admission in patients requiring treatment with 20 ml (two vials), 40 ml (four vials), 60 ml (six vials), and >60 ml of antivenom
Fig 3 Clearance of venom antigen from 148 patients treated with one dose (venom antigen completely cleared by all three antivenoms within 6 hours of start of antivenom); two doses (venom antigen completely cleared from circulation within 12 hours after start of antivenom in patients whose coagulopathy did not respond to initial 20 ml dose); and three doses (venom antigen finally completely cleared from circulation within 18 hours after start of antivenom in patients whose coagulopathy did not respond to first two 20 ml doses)
Efficacy of antivenom treatment
Two patients died. A 4 year old boy treated with Brazilian antivenom and a 38 year old woman treated with Colombian antivenom died 11 hours and 3 days, respectively, after being bitten by B atrox. Both developed acute pulmonary oedema from which they could not be resuscitated. Ten patients (5% in each treatment group) developed local necrosis. All other patients were well on discharge from hospital.
Table 3 gives details of the comparative efficacy of the antivenoms. One hundred and eighty patients were treated with an initial dose of 20 ml (two vials). In those who received this dose of Colombian antivenom, blood coagulability was restored in 64% (46/72) at 6 hours compared with 49% (35/72) and 42% (15/36) of those who received Brazilian and Ecuadorian antivenoms, respectively (P = 0.054). Permanent restoration of coagulability was recorded within 24 hours after starting treatment in almost all patients given 20 ml of Colombian antivenom (64/65; 99%), in 60/67 (90%) treated with the Brazilian antivenom, and in 32/35 (91%) treated with the Ecuadorian antivenom. Colombian antivenom also proved superior when the initial dose was < 70 ml and after any initial dose of antivenom (table 3). Eighty one patients (45%) required more than one dose of antivenom, including 11 patients whose blood became incoagulable again after a normal result from the whole blood clotting test at 6 hours. There was no difference in median total doses of the three antivenoms.
Table 3 Permanent restoration of blood coagulability after various initial doses of antivenom at 6 and 24 hours after start of treatment
Therapeutic concentrations of antivenom
Of the 103 patients in whom we measured serum concentrations of therapeutic antivenom, 63 had received an initial dose of 20 ml with or without subsequent doses. Antivenom was detectable in the serum when serum venom antigenaemia had become undetectable and for at least 48 hours, even in those who had received only a single dose of antivenom (fig 4).
Fig 4 Therapeutic antivenom concentrations in 63 patients according to dose of antivenom on admission: one dose (antivenom clears venom from the circulation within 6 hours after start of antivenom; antivenom concentrations are maximum at 6 hours and remain high for more than two days); two doses (antivenom clears venom within 12 hours from start of first dose of antivenom; antivenom concentrations are maximum at 12 hours); and three doses (antivenom clears venom within 18 hours from start of first dose of antivenom; antivenom concentrations are maximum at 12 hours). Results are means (2 SE) showing overlapping error bars at each time point
Antivenom reactions
Early reactions to antivenom were common, including rash, vomiting, abdominal pain, fevers and chills, pruritis, and, more seriously, dyspnoea and hypotension. In those receiving an initial antivenom dose of 20 ml, reaction rates were 19% (7/37) in those receiving Ecuadorian antivenom, 73% (56/71) for Colombian, and 53% (37/70) for Brazilian antivenom. These rates were significantly different from each other (P < 0.0001). Two patients who developed hypotension had been treated with Colombian antivenom, one with Brazilian antivenom, and one with Ecuadorian antivenom.
Discussion
Swaroop S, Grab B. Snake bite mortality in the world. Bull World Health Org 1954;10: 35-76.
Kerrigan KR. Venomous snakebite in eastern Ecuador. Am J Trop Med Hyg 1991;44: 93-9.
Touzet JM. Mordeduras de ofidios venenosos en la comunidad de los indigenas Siona-Secoya de San Pablo de Kantesyia y datos sobre la fauna de reptiles y anfibios locales. Publicaciones Museo Ecuatoriano de Ciencias Naturales 1986;5: 163-90.
Warrell DA. Snakebites in Central and South America: epidemiology, clinical features, and clinical management. In: Campbell JA, Lamar WW, eds. The venomous reptiles of the western hemisphere. Vol 2. New York: Cornell University Press, 2004: 709-62.
Theakston RDG, Laing GD, Fielding CM, Freire Lascano A, Touzet J-M, Vallejo F, et al. Treatment of snake bites by Bothrops species and Lachesis muta in Ecuador: laboratory screening of candidate antivenoms. Trans R Soc Trop Med Hyg 1995;89: 550-4.
Campbell JA, Lamar WW. The venomous reptiles of the western hemisphere. New York: Cornell University Press, 2004.
Warrell DA, Davidson NMcD, Greenwood BM, Ormerod LD, Pope HM, Watkins BJ, et al. Poisoning by bites of the saw-scaled or carpet viper (Echis carinatus) in Nigeria. Q J Med 1977;46: 33-42.
Sano-Martins IS, Fan HW, Castro SCB, Tomy SC, Fran?a FOS, Jorge MT, et al. Reliability of the simple 20 minute whole blood clotting test (WBCT20) as an indicator of low plasma fibrinogen concentration in patients envenomed by Bothrops snakes. Toxicon 1994;32: 1045-50.
Theakston RDG, Warrell DA. Antivenoms: a list of hyperimmune sera currently available for the treatment of envenoming by bites and stings. Toxicon 1991;29: 1419-70.
Reid HA. Venomous bites and stings. Medicine 1978;3: 341-6.
Theakston RDG, Fan HW, Warrell DA, Dias da Silva WD, Ward SA, Higashi HG. Use of enzyme immunoassays to compare the efficacy and assess dosage regimens of three Brazilian Bothrops antivenoms. Am J Trop Med Hyg 1992;47: 593-604.
Ariaratnam CA, Sj?strom L, Raziek Z, Kularatne SAM, Kodikara RWK, Sheriff MHR, et al. An open, randomised comparative trial of two antivenoms for the treatment of envenoming by Sri Lankan Russell's viper (Daboia russelii russelii). Trans R Soc Trop Med Hyg 2001;95: 74-80.
Cardoso JLC, Fan HW, Fran?a FOS, Jorge MT, Leite RP, Nishioka SA, et al. Randomized comparative trial of three antivenoms in the treatment of envenoming by lance-headed vipers (Bothrops jararaca) in S?o Paulo, Brazil. Q J Med 1993;86: 315-25.
Jorge MT, Cardoso JLC, Castro SCB, Ribeiro L, Fran?a FOS, Sbroglio de Almeida ME, et al. A randomised blinded comparison of two doses of antivenom in the treatment of Bothrops envenoming in S?o Paulo, Brazil. Trans R Soc Trop Med Hyg 1995;89: 111-4.
Otero R, Cardoso JLC, Higashi HG, Nunez V, Diaz A, Toro MF, et al. A randomised, blinded, comparative trial of one pepsin-digested and two whole IgG antivenoms for Bothrops snake bites in Uraba, Colombia. Am J Trop Med Hyg 1998;58: 183-9.
Pardal PP, Souza SM, de Cassia da Costa Monteiro MR, Fan HW, Cardoso JLC, Fran?a FOS, et al. Clinical trial of two antivenoms for the treatment of snake bites in the eastern Amazon region of Brazil. Trans R Soc Trop Med Hyg 2004;98: 28-42.
Phillips RE, Theakston RDG, Warrell DA, Galagadera Y, Abeysekera DTDJ, Dissanayake P, et al. Paralysis, rhabdomyolysis and haemolysis caused by bites of Russell's viper (Vipera russelli pulchella) in Sri Lanka: failure of Haffkine antivenom. Q J Med 1988;68: 691-716.
Warrell DA, Looareesuwan S, Theakston RDG, Phillips RE, Chanthavanich P, Virivan C, et al. Randomized comparative trial of three monospecific antivenoms for bites by the Malayan pit viper (Calloselasma rhodostoma) in southern Thailand: clinical and laboratory correlations. Am J Trop Med Hyg 1986;35: 1235-47.
Chaves F, Barboza M, Gutierrez JM. Pharmacological study of edema induced by venom of the snake Bothrops asper (terciopelo) in mice. Toxicon 1995;33: 31-9.
Farsky SHP, Walber J, Coista-Cruz M, Cury Y, Teixera CF. Leukocyte response induced by Bothrops jararaca crude venom: in vivo and in vitro studies. Toxicon 1997;35: 185-93.
Trebien HA, Calixto JB. Pharmacological evaluation of rat paw edema induced by Bothrops jararaca venom. Agents Actions 1989;26: 292-300.
Laing GD, Clissa PB, Theakston RDG, Moura-da-Silva A, Taylor MJ. Inflammatory pathogenesis of snake venom metalloproteinase-induced skin necrosis. Eur J Immunol 2003;33: 3458-63.
Fan HW, Marcopito LF, Cardoso JLC, Fran?a FOS, Malaque C, Ferrari RA, et al. Sequential randomised and double blind trial of promethazine prophylaxis against early anaphylactic reactions to antivenom Bothrops snake bites. BMJ 1999;318: 1451-3.
Malasit P, Warrell DA, Chanthavanich AP, Virivan C, Mongkolsapaya J, Singhthong B, et al. Prediction, prevention and mechanism of early (anaphylactic) antivenom reactions in victims of snake bites. BMJ 1986;292: 17-20.
Otero R, Gutiérrez JM, Nunez V, Robles A, Estrada R, Segura E, et al. A randomised double-blind clinical trial of two antivenoms in patients bitten by Bothrops atrox in Colombia. Trans R Soc Trop Med Hyg 1996;90; 696-700.
Audebert F, Sorkine M, Bon C. Envenoming by viper bites in France: clinical grading and biological quantification by ELISA. Toxicon 1992;30: 599-609.
Bucher B, Canonge D, Thomas L, Tyburn B, Robbe-Vincent A, Choumet V, et al. Clinical indicators of envenoming and serum levels of venom antigens in patients bitten by Bothrops lanceolatus in Martinique, research group on snake bites in Martinique. Trans R Soc Trop Med Hyg 1997;91: 186-90.
28. Tun-Pe, Ba-Aye, Aye-Aye-Myint, Tin-Nu-Swe, Warrell DA. Bites by Russell's vipers (Daboia russelii siamensis) in Myanmar: effect of the snake's length and recent feeding on venom antigenaemia and severity of envenoming. Trans R Soc Trop Med Hyg 1991;85: 804-8.
Fran?a FOS, Barbaro KC, Fan HW, Cardoso JLC, Sano-Martins IS, Tomy SC, et al. Envenoming by Bothrops jararaca in Brazil: association between venom antigenaemia and severity on admission to hospital. Trans R Soc Trop Med Hyg 2003;97: 312-7.
Silva-Haad JJ. Las serpentes del género Bothrops en la Amazonia colombiana. Comando Unificado del Sur, Amazonia 1982;82: 45-50.(Roger Smalligan, hospital)
Correspondence to: D A Warrell david.warrell@clinical-medicine.oxford.ac.u
Abstract
Each year in Ecuador, 1200-1400 cases of snake bite are reported in 19 of the 21 provinces. Reports from Santo Domingo de los Colorados, Guayaquil,1 and Shell2 confirm its importance. In "El Oriente," east of the Andes, the principal venomous species are Bothrops atrox (common lancehead) and B bilineatus smaragdinus (two striped forest pit viper, also known as Bothriopsis bilineata smaragdina). B taeniatus (speckled forest pit viper, also known as Bothriopsis taeniata), the less common Bothrops and Bothrocophias species and Lachesis muta (bushmaster) cause some bites.3 4 The indigenous Amerindian peoples and people of mixed European ethnicity, whose occupations include farming and logging, are all at risk of snake bite. The principal clinical effects of envenoming by B atrox are life threatening bleeding and blood coagulation disorders, shock, and renal failure. Necrosis and bacterial infection at the site of the bite may cause permanent physical handicap. Envenoming by B bilineatus is usually less severe. Other species such as B brazili and L muta, although potentially as dangerous as B atrox, rarely bite people.4
In an earlier preclinical laboratory study, the neutralising potency of five antivenoms (Brazilian, Ecuadorian, Mexican, and two Colombian) was tested against the venoms of B atrox, B asper, and B xanthogrammus.5 6 The Brazilian antivenom proved most effective, followed by the Ecuadorian and two Colombian antivenoms. The Mexican antivenom showed absolutely no neutralising activity against Ecuadorian Bothrops venoms, consistent with its poor clinical reputation in Ecuador.5 We selected the three most effective antivenoms for a double blind randomised comparative clinical trial in Ecuador.
The main lethal effect of the venoms of the crotaline (rattlesnake-like) pit vipers responsible for envenoming is intracranial or gastrointestinal haemorrhage resulting from vascular endothelial damage, platelet dysfunction, and consumption coagulopathy. These dangerous antihaemostatic disorders and their reversal by specific antivenoms are reflected by whole blood coagulability, which is easily assessed at the bedside with a simple but sensitive 20 minute whole blood clotting test.7 8 We therefore used this test to measure the efficacy of the three antivenoms in restoring whole blood coagulability and observed early reactions to assess safety.
Methods
Randomisation and clinical features
We recruited 210 patients with incoagulable blood (fig 1). Eighty seven patients (41.4%) received Colombian INS antivenom, 82 (39%) received Brazilian antivenom, but only 41 (19.5%) received Ecuadorian antivenom because the supply ran out after the 140th patient (table 1). The groups of patients receiving the three different antivenoms were similar in all respects on admission to hospital and before they received treatment (tables 1 and 2). Table 2 shows the clinical features of recruited patients.
Fig 1 Flow of patient through study
Table 1 Comparison of groups of patients bitten by snakes in Ecuador, at randomisation before treatment with antivenom*
Table 2 Clinical features of envenoming in 210 patients bitten by snakes. All had incoagulable blood before randomisation to antivenom therapy*
Snakes responsible for bites
Twenty nine patients (14%) brought in the snake responsible for the bite: 13 (45%) were identified as B atrox, 12 (41%) as B bilineatus smaragdinus, 2 (7%) as B taeniatus, and 2 (7%) remained unidentified (table 1). Specimens of B atrox ranged from 20-90 cm (mean 43 cm, SD 22 cm) and B bilineatus 15-50 cm (34 cm, SD 14 cm) and the two B taeniatus specimens measured 150 cm and 180 cm. With the help of herpetologists and the results of enzyme immunoassay we identified the snake responsible for envenoming in 187 (89%) cases: 109 (58%) were bitten by B atrox, 68 (36%) by B bilineatus, 6 (3%) by B taeniatus, 1 (1%) by B brazili, and 3 (2%) by L muta. The distribution of bites by the different species was similar among the three groups (table 1).
Venom antigen detection
We assessed the serum concentrations of venom antigen from admission to discharge in 148 patients out of the 180 who received an initial dose of 20 ml of antivenom (samples from 32 patients were lost during transport from Shell to Quito). Concentrations on admission correlated significantly with the total volume of antivenom required to restore blood coagulability permanently (P < 0.0001). In the small group of patients who required more than 60 ml of antivenom, median venom antigen concentrations were about fourfold to fivefold higher than those in patients who required only 20 ml of antivenom (fig 2). The time to venom clearance was also longer in patients who required higher doses of antivenom (fig 3).
Fig 2 Relation between median serum concentrations of venom antigen on admission in patients requiring treatment with 20 ml (two vials), 40 ml (four vials), 60 ml (six vials), and >60 ml of antivenom
Fig 3 Clearance of venom antigen from 148 patients treated with one dose (venom antigen completely cleared by all three antivenoms within 6 hours of start of antivenom); two doses (venom antigen completely cleared from circulation within 12 hours after start of antivenom in patients whose coagulopathy did not respond to initial 20 ml dose); and three doses (venom antigen finally completely cleared from circulation within 18 hours after start of antivenom in patients whose coagulopathy did not respond to first two 20 ml doses)
Efficacy of antivenom treatment
Two patients died. A 4 year old boy treated with Brazilian antivenom and a 38 year old woman treated with Colombian antivenom died 11 hours and 3 days, respectively, after being bitten by B atrox. Both developed acute pulmonary oedema from which they could not be resuscitated. Ten patients (5% in each treatment group) developed local necrosis. All other patients were well on discharge from hospital.
Table 3 gives details of the comparative efficacy of the antivenoms. One hundred and eighty patients were treated with an initial dose of 20 ml (two vials). In those who received this dose of Colombian antivenom, blood coagulability was restored in 64% (46/72) at 6 hours compared with 49% (35/72) and 42% (15/36) of those who received Brazilian and Ecuadorian antivenoms, respectively (P = 0.054). Permanent restoration of coagulability was recorded within 24 hours after starting treatment in almost all patients given 20 ml of Colombian antivenom (64/65; 99%), in 60/67 (90%) treated with the Brazilian antivenom, and in 32/35 (91%) treated with the Ecuadorian antivenom. Colombian antivenom also proved superior when the initial dose was < 70 ml and after any initial dose of antivenom (table 3). Eighty one patients (45%) required more than one dose of antivenom, including 11 patients whose blood became incoagulable again after a normal result from the whole blood clotting test at 6 hours. There was no difference in median total doses of the three antivenoms.
Table 3 Permanent restoration of blood coagulability after various initial doses of antivenom at 6 and 24 hours after start of treatment
Therapeutic concentrations of antivenom
Of the 103 patients in whom we measured serum concentrations of therapeutic antivenom, 63 had received an initial dose of 20 ml with or without subsequent doses. Antivenom was detectable in the serum when serum venom antigenaemia had become undetectable and for at least 48 hours, even in those who had received only a single dose of antivenom (fig 4).
Fig 4 Therapeutic antivenom concentrations in 63 patients according to dose of antivenom on admission: one dose (antivenom clears venom from the circulation within 6 hours after start of antivenom; antivenom concentrations are maximum at 6 hours and remain high for more than two days); two doses (antivenom clears venom within 12 hours from start of first dose of antivenom; antivenom concentrations are maximum at 12 hours); and three doses (antivenom clears venom within 18 hours from start of first dose of antivenom; antivenom concentrations are maximum at 12 hours). Results are means (2 SE) showing overlapping error bars at each time point
Antivenom reactions
Early reactions to antivenom were common, including rash, vomiting, abdominal pain, fevers and chills, pruritis, and, more seriously, dyspnoea and hypotension. In those receiving an initial antivenom dose of 20 ml, reaction rates were 19% (7/37) in those receiving Ecuadorian antivenom, 73% (56/71) for Colombian, and 53% (37/70) for Brazilian antivenom. These rates were significantly different from each other (P < 0.0001). Two patients who developed hypotension had been treated with Colombian antivenom, one with Brazilian antivenom, and one with Ecuadorian antivenom.
Discussion
Swaroop S, Grab B. Snake bite mortality in the world. Bull World Health Org 1954;10: 35-76.
Kerrigan KR. Venomous snakebite in eastern Ecuador. Am J Trop Med Hyg 1991;44: 93-9.
Touzet JM. Mordeduras de ofidios venenosos en la comunidad de los indigenas Siona-Secoya de San Pablo de Kantesyia y datos sobre la fauna de reptiles y anfibios locales. Publicaciones Museo Ecuatoriano de Ciencias Naturales 1986;5: 163-90.
Warrell DA. Snakebites in Central and South America: epidemiology, clinical features, and clinical management. In: Campbell JA, Lamar WW, eds. The venomous reptiles of the western hemisphere. Vol 2. New York: Cornell University Press, 2004: 709-62.
Theakston RDG, Laing GD, Fielding CM, Freire Lascano A, Touzet J-M, Vallejo F, et al. Treatment of snake bites by Bothrops species and Lachesis muta in Ecuador: laboratory screening of candidate antivenoms. Trans R Soc Trop Med Hyg 1995;89: 550-4.
Campbell JA, Lamar WW. The venomous reptiles of the western hemisphere. New York: Cornell University Press, 2004.
Warrell DA, Davidson NMcD, Greenwood BM, Ormerod LD, Pope HM, Watkins BJ, et al. Poisoning by bites of the saw-scaled or carpet viper (Echis carinatus) in Nigeria. Q J Med 1977;46: 33-42.
Sano-Martins IS, Fan HW, Castro SCB, Tomy SC, Fran?a FOS, Jorge MT, et al. Reliability of the simple 20 minute whole blood clotting test (WBCT20) as an indicator of low plasma fibrinogen concentration in patients envenomed by Bothrops snakes. Toxicon 1994;32: 1045-50.
Theakston RDG, Warrell DA. Antivenoms: a list of hyperimmune sera currently available for the treatment of envenoming by bites and stings. Toxicon 1991;29: 1419-70.
Reid HA. Venomous bites and stings. Medicine 1978;3: 341-6.
Theakston RDG, Fan HW, Warrell DA, Dias da Silva WD, Ward SA, Higashi HG. Use of enzyme immunoassays to compare the efficacy and assess dosage regimens of three Brazilian Bothrops antivenoms. Am J Trop Med Hyg 1992;47: 593-604.
Ariaratnam CA, Sj?strom L, Raziek Z, Kularatne SAM, Kodikara RWK, Sheriff MHR, et al. An open, randomised comparative trial of two antivenoms for the treatment of envenoming by Sri Lankan Russell's viper (Daboia russelii russelii). Trans R Soc Trop Med Hyg 2001;95: 74-80.
Cardoso JLC, Fan HW, Fran?a FOS, Jorge MT, Leite RP, Nishioka SA, et al. Randomized comparative trial of three antivenoms in the treatment of envenoming by lance-headed vipers (Bothrops jararaca) in S?o Paulo, Brazil. Q J Med 1993;86: 315-25.
Jorge MT, Cardoso JLC, Castro SCB, Ribeiro L, Fran?a FOS, Sbroglio de Almeida ME, et al. A randomised blinded comparison of two doses of antivenom in the treatment of Bothrops envenoming in S?o Paulo, Brazil. Trans R Soc Trop Med Hyg 1995;89: 111-4.
Otero R, Cardoso JLC, Higashi HG, Nunez V, Diaz A, Toro MF, et al. A randomised, blinded, comparative trial of one pepsin-digested and two whole IgG antivenoms for Bothrops snake bites in Uraba, Colombia. Am J Trop Med Hyg 1998;58: 183-9.
Pardal PP, Souza SM, de Cassia da Costa Monteiro MR, Fan HW, Cardoso JLC, Fran?a FOS, et al. Clinical trial of two antivenoms for the treatment of snake bites in the eastern Amazon region of Brazil. Trans R Soc Trop Med Hyg 2004;98: 28-42.
Phillips RE, Theakston RDG, Warrell DA, Galagadera Y, Abeysekera DTDJ, Dissanayake P, et al. Paralysis, rhabdomyolysis and haemolysis caused by bites of Russell's viper (Vipera russelli pulchella) in Sri Lanka: failure of Haffkine antivenom. Q J Med 1988;68: 691-716.
Warrell DA, Looareesuwan S, Theakston RDG, Phillips RE, Chanthavanich P, Virivan C, et al. Randomized comparative trial of three monospecific antivenoms for bites by the Malayan pit viper (Calloselasma rhodostoma) in southern Thailand: clinical and laboratory correlations. Am J Trop Med Hyg 1986;35: 1235-47.
Chaves F, Barboza M, Gutierrez JM. Pharmacological study of edema induced by venom of the snake Bothrops asper (terciopelo) in mice. Toxicon 1995;33: 31-9.
Farsky SHP, Walber J, Coista-Cruz M, Cury Y, Teixera CF. Leukocyte response induced by Bothrops jararaca crude venom: in vivo and in vitro studies. Toxicon 1997;35: 185-93.
Trebien HA, Calixto JB. Pharmacological evaluation of rat paw edema induced by Bothrops jararaca venom. Agents Actions 1989;26: 292-300.
Laing GD, Clissa PB, Theakston RDG, Moura-da-Silva A, Taylor MJ. Inflammatory pathogenesis of snake venom metalloproteinase-induced skin necrosis. Eur J Immunol 2003;33: 3458-63.
Fan HW, Marcopito LF, Cardoso JLC, Fran?a FOS, Malaque C, Ferrari RA, et al. Sequential randomised and double blind trial of promethazine prophylaxis against early anaphylactic reactions to antivenom Bothrops snake bites. BMJ 1999;318: 1451-3.
Malasit P, Warrell DA, Chanthavanich AP, Virivan C, Mongkolsapaya J, Singhthong B, et al. Prediction, prevention and mechanism of early (anaphylactic) antivenom reactions in victims of snake bites. BMJ 1986;292: 17-20.
Otero R, Gutiérrez JM, Nunez V, Robles A, Estrada R, Segura E, et al. A randomised double-blind clinical trial of two antivenoms in patients bitten by Bothrops atrox in Colombia. Trans R Soc Trop Med Hyg 1996;90; 696-700.
Audebert F, Sorkine M, Bon C. Envenoming by viper bites in France: clinical grading and biological quantification by ELISA. Toxicon 1992;30: 599-609.
Bucher B, Canonge D, Thomas L, Tyburn B, Robbe-Vincent A, Choumet V, et al. Clinical indicators of envenoming and serum levels of venom antigens in patients bitten by Bothrops lanceolatus in Martinique, research group on snake bites in Martinique. Trans R Soc Trop Med Hyg 1997;91: 186-90.
28. Tun-Pe, Ba-Aye, Aye-Aye-Myint, Tin-Nu-Swe, Warrell DA. Bites by Russell's vipers (Daboia russelii siamensis) in Myanmar: effect of the snake's length and recent feeding on venom antigenaemia and severity of envenoming. Trans R Soc Trop Med Hyg 1991;85: 804-8.
Fran?a FOS, Barbaro KC, Fan HW, Cardoso JLC, Sano-Martins IS, Tomy SC, et al. Envenoming by Bothrops jararaca in Brazil: association between venom antigenaemia and severity on admission to hospital. Trans R Soc Trop Med Hyg 2003;97: 312-7.
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