Snake-bite Envenomation - Internet Scientific Publications

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disclose that an estimated 10,000 annual venomous snake bites account for 2000 deaths. 2 Romulus Whitaker, pointed out that, the Indian cobra (Naja naja), ...
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The Internet Journal of Emergency Medicine Volume 5 Number 1

Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital K Sam, M Khan, S Peerally, P Kumar, P Rao Citation

K Sam, M Khan, S Peerally, P Kumar, P Rao. Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital. The Internet Journal of Emergency Medicine. 2008 Volume 5 Number 1. Abstract Snake bite is a known cause for increased morbidity and mortality in India. A six year retrospective review of medical records was carried out to study the trends, epidemiology, snakebite severity, treatment, and outcome among 252 patients of snakebite in a tertiary care South Indian hospital. Severity assessment showed an average grade of 3.3 with moderate injury. Hemotoxicity and Cellulitis was the most common complications among unidentified snake bites and cobra bites. An average of 11.9 ± 9.3 vials (N=2994) were administered and 96 (48%) anaphylactic reactions were observed. The mortality rate was 10.7% (n=27) while 78.9%of patients improved with 8.2±8.3 day hospitalization period. Severity scores, complications and outcomes were significantly associated with type of snakes, age distribution and linearly correlated to the time elapsed between snake bite instance and hospitalization. Mortality and morbidity can be minimised by the early interventions following identification of snakes, associated sign, symptoms and severity.

INTRODUCTION In India, it is estimated that up to 20,000 people die annually from snake bites. Morbidity is also significant and there seems to have been little improvement in reducing the fatalities over the years in spite of now having good supplies of polyvalent anti-snake venom (ASV) available in all population centers. The major reason for high mortality rate (about 5% to 10% of all those reporting bites) is the delay in getting the victim to a well-equipped casualty treatment facility fast enough. Snake bite, an important cause of death in rural patients in developing countries, is a neglected public health problem. Worldwide, of the estimated 5 million people bitten by snakes each year, about 1,25,000 die. 1 More than 2,00,000 cases of snake bite are reported in India each year and 35,000–50,000 of them have turned out to be fatal. Reports from Maharashtra, State in India, disclose that an estimated 10,000 annual venomous snake bites account for 2000 deaths. 2 Romulus Whitaker, pointed out that, the Indian cobra (Naja naja), the common krait (Bungarus caeruleus), the Russell's viper (Daboia russelii) and the sawscaled viper (Echis carinatus) are basically four venomous snakes found in India. He called them the “Big Four” which are mainly responsible for Indian snake bite mortality. 3 The concept of the ‘‘Big Four'‘ restricts sound

epidemiological work and the development of effective snake antivenoms. It should be replaced by the model introduced in the 1980s by the World Health Organization, which has not received adequate circulation and implementation. 4 The type of snake bite varies from region to region. Wherever one species prevails, the chances of humans coming into their contact is higher, then the bite of that species will be more common. 3 Snake bite is continuing to be a major medical concern in India. World Health Organization survey reports that 1.2–2.4 deaths occur per 100,000 victims with a mortality level of 25,000 per annum. There are many causal factors that contribute to this mortality rate, and many questions remain unanswered. To make more meaningful use of resources such as antivenom, ventilator therapy and renal support systems in patients with snake bite, it is important that the healthcare providers aptly identify those at high risk of potentially fatal complications. Simple demographic and clinical characteristics could be used to help doctors distinguish between high-risk and lowrisk patients. To be useful, the predictors like snake bite severity score should be simple, accurate and clinically credible.

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Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital There has, however, been very little qualitative herpetological work in India, since the 1940s. Limited statistics on mortality and morbidity due to envenomation are available. Such data have recognizable limitations. 4 There are very limited Indian studies which have assessed severity and its role in predicting outcome of snake envenomation. The factors, like time-lags from exposure till hospitalisation, influencing the severity and outcome, are not captured during epidemiological studies. The present study was carried to out to estimate the snake bite related epidemiology, clinical characteristics, severity and outcome. An attempt was made to evaluate the predictors of severity, relationship between type of snake, clinical severity, complications, outcome and usage pattern of polyvalent anti snake venom (ASV).

identified from medical records which were arranged according to ICD-10 classification of diseases. A computer generated list, of patients with hospital numbers was collected. The medical records of patients, discharged with diagnosis of envenomation due to venomous snakes were obtained from the medical record office. Records with diagnosis of envenomation from arthropods, or other animals were excluded. Epidemiological data collected from the medical records were categorized into type of snake identified; time lapsed from the time of bite till the time of hospital admission, clinical characteristics of snake bite, severity, quantity of polyvalent antisnake venom used, outcome in terms of duration of hospitalisation, and clinical status at discharge.

MATERIALS AND METHODS

The severity of envenomation was assessed using to the modified snakebite severity score (SSS) according to Dart et al.,1996 and Nualnong et al., 2005. 5,6 Occurrence of a particular symptom was checked against the chart (Table 1) and graded. The severity grading assigned to a case was determined by the most severe symptom(s) or signs(s) observed. The severity was graded from 0 to 4 ranging from no envenomation to severe life threatening symptoms and death taking into consideration clinical signs/symptoms and/or laboratory data. The four levels represent as follows; grade 0 for no symptoms or signs, grade 1 for mild, transient and spontaneously resolving symptoms or signs, grade 2 for moderate, pronounced or prolonged symptoms or signs, grade 3 for severe or life threatening symptoms or signs, while grade 4 represents extremely severe envenomation leading to mortality. The factors that affect SSS like prehospitalization period, demographical variables, type of snakebite and the outcome were evaluated.

STUDY SITE A retrospective review of medical records was carried out to determine the pattern of snake bite envenomation cases admitted to Kasturba hospital. Medical records of patients admitted for six years during the period January 2002 to December 2007 were reviewed. All patients of snake bite that were presented to our institution over a period of 6 years were included in the present study. The study aimed to assess the time lag between snake bite and hospitalisation, severity of patient at hospitalisation and subsequent development of complications, treatment provided and the outcome of 252 patients who became eligible for the study.

OPERATION MODALITY Study was conducted by carrying out a review of envenomed patients presenting to the emergency centre. The cases were

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SEVERITY ASSESSMENT.

Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital Figure 1

Table 1: Snakebite Severity Scale (SSS) (Dart et al.,1996)

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Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital

OUTCOME ANALYSIS Outcomes like hospitalization period and clinical condition at the time of discharge were determined. The clinical outcomes were sorted out using three variables, namely improved, morbid state or fatal outcome. The variable ‘improved status' was defined as state of complete recovery with no associated permanent physical or physiological abnormality. ‘Morbidity state' was defined as a state of either clinically unstable vital functions or disturbed physical, functional and physiological state. ‘Fatality' was defined as clinical state of brain death as certified by the physician. Factors affecting clinical outcome, like demographical factors, prehospitalization period and SSS were assessed.

ASSESSMENT OF TREATMENT The treatment provided was assessed in terms of the quantity of polyvalent anti snake venom vials (ASV) administered during the hospitalisation and compared with the severity and outcome. The time lapsed was compared to assess its role in predicting severity and outcome. The patient's records were evaluated from day of admission to discharge in order to note any subsequent development of complications. The incidence of complications like renal failure, neurotoxicity including ptosis, breathing difficulty, and hematological toxicity including, bleeding time, clotting time, prothrombin time, active prothrombin time, and cellulitis were evaluated and compared with the type of snake implicated in the envenomation .

STATISTICAL ANALYSIS Results were expressed as frequency percentages. The categorical data collected was summarized using proportions by chi-square test. Pearson's correlation test was used to study the linear correlation between various scores. A probability of P?0.05 was considered statistically significant. SPSS version 13, 2004 statistical software was used for evaluation. Chi-square analysis was carried out to assess the association of severity, clinical complications and outcome with parameters like type of snake involved, the demographical parameters, site of bite, time lapsed after bite, number of ASV vials.

RESULTS PATIENT CHARACTERISTICS AND DEMOGRAPHIC ANALYSIS OF SNAKE BITE PATIENTS: Two hundred and fifty two patients of snake bites became

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eligible for the study, over a period of 6 years. Majority were aged between 11- 50 years, the youngest patient was one year old, age was 82 years. Gender distribution revealed that 154(61.1%) patients were males while 98 (38.9%) were females. The relationship between the various determinants affecting severity and outcome are summarized in Table2 and Table 3. The mean time elapsed between snake bite and time of hospital admission was 28.97 ±77.7 hours with a median time of 6 hours. Majority of patients N=169 (67.1%) had a severity grade between 2 and 3 and 95 (37.7%) of them had a grade 3 severity which denotes occurrence of severe life threatening symptoms. Assessment of the determinants of severity grading score showed that there was a statistically significant (P