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Journal of Venomous Animals and Toxins

Print version ISSN 0104-7930On-line version ISSN 1678-4936

J. Venom. Anim. Toxins vol.7 no.1 Botucatu  2001 




 1 Servicio de Infectología, Hospital Nacional de Niños, San José, Costa Rica.



ABSTRACT: Snakebite envenomation is a worldwide problem and in Costa Rica. The following is a retrospective review of 79 patients admitted to the Hospital Nacional de Niños (HNN) from January 1985 to September 1996. Child's age ranged from 9 months to 14 years. The M: F ratio was 1.5:1. Sixty percent of the patients lived in remote rural areas. The most common clinical signs at the time of hospitalization were pain and edema. Fifty patients (63,29%) showed moderate to severe envenomation grades. Fifty-one (64,55%) was caused by Bothrops asper. Complications during hospitalization were compartment syndrome and secondary infection. Three children died, one from disseminated intravascular coagulation, another from renal insufficiency, and the third from a perforated duodenal ulcer. Patients who underwent early fasciotomy had significantly less hospitalization and fewer infectious complications, (p < 0.001). There was no relationship between the envenomation grade and length of hospitalization (p = 0.4). The most common pathogen isolated was S. aureus.

Early fasciotomy seemed to reduce the complications seen in these patients. Further studies are necessary to identify the factors that may help clinicians to decide those who should undergo fasciotomy, as well as the best moment to perform it.
KEY WORDS: snakebites, complications, fasciotomy, children.




Snakebite envenomation is a worldwide problem resulting in approximately 30,000 annual deaths(17). In the United States, between 40,000 and 50,000 people are bitten by snakes annually. From these 8,000 to 10,000 are from venomous snakes, of which 15 are fatal(20).

In Costa Rica, a country with a great variety of venomous snakes nearly 700 people are bitten by snakes every year, with 10 to 15 deaths(10). Bothrops asper accounts for more than 50% of the snakebites and the majority of deaths.

At the Hospital Nacional de Niños (HNN) in San José, Costa Rica, approximately 6 to 10 snakebites are treated annually. The purpose of this study was to record demographic data, clinical features and complications in children, and determine if early fasciotomy can reduce complications and improve the outcome.



Data were obtained from the hospital clinical records of patients released after diagnosis of snakebite envenomation between January 1985 and September 1996. Information on age, sex, geographic origin, area affected, envenomation grade, snake species, length of hospitalization, treatment, complications, and condition at the time of discharge were recorded.

Envenomation Grades: Classification of envenomation grades(4,7):

Grade 0. Absence of signs or symptoms; antivenom administration not required;

Grade 1. Mild - Local swelling, pain, and erythema; no systemic manifestations; normal laboratory findings; initial antivenom dose 4 to 5 vials;

Grade 2. Moderate - Progressive swelling around the bite site and one or more systemic manifestations; abnormal laboratory findings, such as decreased hematocrit or platelet; initial antivenom dose 6 to 10 vials;

Grade 3. Severe - Marked systemic manifestations and significant alteration in laboratory findings; initial antivenom dose 11 vials or more.

Fasciotomy was classified as early or late depending on whether it was done during the first 48 hours or thereafter.

Primary bacterial infection was defined as clinical signs of infection at the bite site or a positive blood culture during the first 72 hours of hospitalization. Secondary (nosocomial) infection was defined as bacterial super-infection 72 hours after hospitalization.

As established in our institution, blood cultures were made for all patients before initiating intravenous antibiotic treatment. Intravenous antibiotics used were penicillin G and an aminoglycoside (gentamicin or amikacin). Swabs from the wound and from fasciotomy, when performed were used for culture. Specimens were examined by Gram staining and were cultured using routine methods. In this study, no samples were collected under anaerobic conditions.

A coagulation disorder was identified due to the presence of the following: hematuria, positive stool guaiac, gum bleeding or punctured sites, coagulation abnormalities, or/and thrombocytopenia. 

Statistical Analysis. Categorical data were compared using the Chi-square test. A p value < 0.05 was considered significant.



During the study period, 100 patients were discharged from the HNN with snakebite diagnosis. Information for analysis was available from 82 patients. Seventy-nine of these patients were bitten by venomous snakes and three by non-venomous snakes.

Child's age ranged from 9 months to 14 years, with most of them being between 6 and 10 years. The M: F ratio was 1.5:1 and 47/79 (59.49%) of the patients lived in remote rural areas (Table 1).


Table 1. Characteristics of the 79 children bitten by venomous snakes.

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Pain and edema at the bite site were the most common clinical signs at the time of hospitalization (Table 2). A 24-month-old patient arrived at the hospital with disseminated intravascular coagulation (DIC) of unknown etiology. Diagnosis of snakebite was made when the mother said that the child told her that some ants had bitten his head. His hair was shaved and bite marks were found on the scalp. Despite intensive care the patient died.


Table 2. Clinical Findings of the 79 children bitten by venomous snakes.

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In 50/79 patients (63.29%), the envenomation grade was moderate to severe. Fifty-five patients (69.62%) were bitten in the lower limbs, 21/79 patients (26.52%) in the upper limbs, and 6/79 patients (7.59%) on the face.

In general, 51/82 (62.19%) bites were caused by Bothrops asper, while bites from other species were not common. Crotalus durissus, three patients and Micrurus nigrocinctus, one patient. The snake specie was not identified in 24/82 cases (29.27%). In three cases, identification was not made because of lack of signs and symptoms, and we concluded that the patients had been bitten by non-venomous snakes.

Of the 79 patients with snake envenoming diagnosis, 64 were transferred from other hospitals to the HNN. The most common reason of referral was for fasciotomy, 34 (43.03%) patients. Other reasons included severe bleeding, (8/79, 10.12%), allergic reaction to antivenom (4/79, 5.06%), and age less than 12 months (3/79, 3.8%). Fifteen patients (18.99%) remained in the hospital for observation.

The seeking of medical attention took less than one day for 58 patients (73.41%), from one to two days for 8 patients (10.12%), and more than 2 days for 13 patients (16.45%).

Table 3 shows the complications during hospitalization. Compartment syndrome was the most frequent complication (n = 41, 51.89%). Thirty-seven patients (46.83%) developed secondary infection, of these 12 (15.18%) showed abscess formations. Three children died; a 14-month old from secondary infection to DIC; an 11-year old of secondary infection to DIC and renal failure; and an 11-year old of a perforated duodenal ulcer during surgery.


Table 3. Complications during hospitalization of the 79 children bitten by venomous snakes.

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In 13 of 37 cases with a secondary infection, bacterial species were cultured. Two bacterial species in six patients, three in five patients, and four in two patients (Table 4). In 14 patients, bacteria were not isolated despite clinical evidence of infection. Of the 67 blood cultures, only one was positive for Staphylococcus aureus.


Table 4. Etiologic agents of primary and secondary infections in the 79 children bitten by venomous snakes. Eighteen patients showed primary infection and 37 secondary infection.

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The average length of hospitalization was 12.8 days (range 1-71 days). In 23/79 patients (29.11%) early fasciotomy was performed and in 18/79 (22.78%) late fasciotomy. When comparing patients who underwent early fasciotomy with those with late fasciotomy, hospitalization was significantly shorter in the first group (p < 0.001). There was no relationship between envenomation grade and length of hospitalization (p = 0.4). Infectious complications were less frequent in patients who underwent early fasciotomy in comparison with those who were not submitted to this procedure or those for whom therapy was delayed (p < 0.001). Other complications, including persistent functional limitation of limb movement because of muscle retractions and/or keloids scar were seen in 25/79 (31.64%) of the patients.



In Costa Rica there are more than 130 species of snakes, but only 18 are considered venomous. Snakes can be divided into three families: 1) Hydrophiidae, better known as sea snakes, including Pelamis platurus; 2) Elapidae, also known as coral snakes, including Micrurus nigrocinctus, M. alleni, M. clarcki, and M. mipartitus; and 3) Viperidae subdivided into Crotalus, Lachesis, Agkistrodom, and Bothrops genera (4,10,17,20). It has recently been suggested that some species classified as Bothrops should be classified in the new genera Atropoides, Bothriechis, and Porthidium (10).

Adult males are more at risk to snakebites, especially laborers. Children are also a major risk group because they frequently work on farms (4,7,10). Snakebites occur mostly in the lower limbs, suggesting that many bites could be prevented by wearing boots that avoid the penetration of the snake fangs.

Recommended first aid treatment for snakebite includes cleaning the bitten area with soap and water and immobilizing the wounded limb. Transporting the victim to the nearest hospital for antivenom administration as soon as possible is recommended.

In Costa Rica, the Clodomiro Picado Institute distributes two types of antivenom produced in horses: a polyvalent antivenom against most Central American venomous snakes from the Viperidae family and an coral antivenom against bites caused by most Central American Micrurus snakes (10,19).

Bites by coral snakes are relatively rare in Costa Rica, with approximately 10 cases reported each year. We have three recorded cases (3.5%). When a coral snake bites, the venom is introduced into the subcutaneous tissue and disseminated by lymphatic and blood vessels. When it reaches the neuromuscular junction, the venom produces a depolarizing synaptic block with a consequent flaccid paralysis (9). One of the first signs of toxicity is ptosis, followed by ophthalmoplegia, diplopia, disarthria, and muscular weakness (19). In this study, one patient had facial nerve palsy.

In our country, the most frequent envenoming is caused by Viperidae snakes. This venom consists of toxic proteins including myotoxins, anticoagulants, clothing toxins, nephrotoxins, and neurotoxins (10). The combination of these toxic effects can create a complex pathophysiological state characterized by immediate local effects and various systemic perturbations that may occur immediately or be delayed (9,18,22,24). The severity of envenomation varies and clinical assessment of severity is an important tool in deciding appropriate treatment. Severity depends on several factors (14,16,21,25).

1. The amount venom injected. Bothrops asper compared to other species injects large quantities of venom, often resulting in death;

2. The anatomic bite site. The bite is more severe when it involves the head or the trunk;

3. The weight, height, and general condition of the victim. Children are usually more severely affected because of their smaller volume relative to venom dose.

Pain and edema at the injection site are the most frequent findings, as shown in this study. Local swelling results from the direct action of venom on the endothelium, which causes the release of inflammatory mediators. The increase in vascular permeability with subsequent increase in the interstitial volume may result in a compartment syndrome (9,22,24,25).

In this study, early bacterial infection was common. Snake mouth is heavily colonized by many bacteria, consequently the wounded tissue favors bacterial proliferation (19) Arroyo et al. found a high incidence of anaerobes, including Clostridium spp and aerobic organisms, such as Proteus vulgaris, Morganella morganii, Proteus mirabilis, Providencia spp, Klebsiella spp, Pseudomonas spp, and Escherichia coli in the oral cavities of venomous snakes (Bothrops asper, Lachesis muta, Crotalus durissus) (3) Bolaños and Brunker reported concentrations of anaerobic and aerobic bacteria of 3 x 1024 CFU/ml in B. asper and C. durissus durissus venom (5). This information is useful for choosing the appropriate antibacterial therapy. Similar findings have been reported in South America (2,12,13). In our study, the most frequently isolated organisms were Enterobacteriaceae similar to that reported by Arroyo et al. (3). This finding emphasizes the need for cleansing snakebite wounds and for strict aseptic techniques. Appropriate antibiotic therapy includes penicillin or clindamycin and an aminoglycoside (2,3,5,12). Abscess drainage and necrotic tissue debridement are essential to prevent bacterial infection and growth (11).

In this study, 30% of the patients bitten by Viperidae snakes developed hemorrhagic phenomena, and DIC was the cause of death in two patients. Hemorrhage is a consequence of the direct action of the metalloproteinases present in snake venom on the endothelium (10). There is also a thrombin-like enzyme in the venom that activates fibrinogen, which produces microthrombosis. Blood loss and microvascular damage resulting in third space fluid losses often causes cardiovascular shock. These together with the effect of venomous toxins on the renal tubules cause acute renal failure, another factor contributing to the mortality of these patients (9).

Fasciotomy is mandatory in all patients with compartment syndrome. Many authors report that caution should be taken before performing an invasive intervention such as fasciotomy, which may result in further complications (1,6,8,15,23,25). The Doppler technique to evaluate blood flow in the affected area (1) and the measurement of compartment pressure are recommended. If the pressure is over 30-mmHg, surgery should be performed. Local pulse oximetry below 10 mm of O2 compared to that of other parts of the body is also an indicator of surgery. Because of the high bacterial contamination rate in snakebites, early fasciotomy may avoid further complications or even prevent limb loss. In this retrospective study, early fasciotomy significantly shortened hospitalization. On the other hand, secondary infection was common in patients submitted to late fasciotomy or those who were not submitted to this procedure. Interestingly, the severity of the snakebites did not correlate with hospitalization time.

It thus appears that one of the most important factors determining the outcome of bitten patients is the critical timing of surgical intervention. Further studies are necessary to identify factors that can help clinicians to decide which patients need early fasciotomy.



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