Guidelines for the Management of Snakebites

Description

Snakebites are well-known medical emergencies in many parts of the world, especially in rural areas. Agricultural workers and children are most affected. The incidence of snakebite mortality is particularly high in South-East Asia. Rational use of snake anti-venom can substantially reduce mortality and morbidity due to snake bites. These guidelines are a revised and updated version of those published in 2011. The geographical coverage extends from India in the west to DPR Korea and Indonesia in the east, Nepal and Bhutan in the north, and to Sri Lanka and Indonesia in the south and south-east. Snakes inhabiting the Indonesian islands east of Wallace’s line (West Papua and Maluku Islands) are part of the Australasian elapid fauna, differing from those west of this line. This publication passes on a digest of available knowledge about all clinical aspects of snake-bite to medically trained personnel, including medical doctors, nurses, dispensers and community health workers. They will provide sufficient practical information to allow medically trained personnel to assess and treat patients with snake-bites at different levels of the health service. i. Foreword 7 ii. Acknowledgement 8 iii. Preface 9 1 Executive summary 11 2 Prevention 17 Essentials 19 2.1 Reducing the risk of snakebites 19 2.2 Implementing preventive strategies for community education 22 2.3 Conclusion 23 3 Venomous snakes of the South-East Asia Region, 25 their venoms and pathophysiology of human envenoming Essentials 27 3.1 The venom apparatus 3.2 Classification of venomous snakes 29 3.2.1 Medically important species in South-East Asia Region countries 30 3.2.2 Other medically important venomous snakes 63 3.2.3 Non-venomous snakes 64 3.3 Identification of venomous snakes 67 3.4 Snake venoms 67 3.4.1 Venom composition 67 3.4.2 Quantity of venom injected at a bite, “dry bites” 69 3.4.3 Variations in venom composition within 69 individual species of snakes 3.5 Pathophysiology of human envenoming 69 4 Epidemiology of snakebites in South-East Asia Region countries 73 Essentials 75 4.1 Introduction 77 4.2 Determinants of snakebite incidence and severity of envenoming 78 4.3 Epidemiological characteristics of snakebite victims 79 4.4 Circumstances of snakebites 79 4.5 Snakebite as an occupational disease 79 4.6 Death from snakebite 80 4.6.1 Factors contributing to fatal snakebite 80 4.6.2 Time between snakebite and death 80 4.7 Snakebite in different South-East Asia Region countries 80 5 Clinical aspects of snakebites 89 Essentials 91 5.1 When venom has not been injected 94 5.2 When venom has been injected 94 5.2.1 Early symptoms and signs 94 5.2.2 Clinical patterns of envenoming by snakes in South East Asia 95 5.2.3 Local symptoms and signs in the bitten part 95 5.2.4 Generalized (systemic) symptoms and signs 96 5.3 Clinical syndromes of snakebite in South-East Asia 101 5.4 Long-term complications (sequelae) of snakebite 104 5.5 Symptoms and signs of seasnake envenoming 103 5.6 Symptoms and signs of cobra-spit ophthalmia 104 (eye injuries from spitting cobras) 6 Management of snakebites in South-East Asia 105 Essentials 107 6.1 Stages of management 115 6.2 First-aid treatment 115 6.2.1 Principles of first-aid 115 6.2.2 The danger of respiratory paralysis and shock 115 6.2.3 Recommended first-aid methods 116 6.3 Transport to hospital 117 6.4 Medical treatment in the dispensary or hospital 118 6.4.1 Rapid primary clinical assessment and resuscitation 118 6.4.2 Detailed clinical assessment 119 6.4.2.1 History 119 6.4.2.2 Physical examination 120 6.4.2.3 Neurotoxic envenoming: Bulbar and respiratory paralysis 121 6.4.2.4 Generalized rhabdomyolysis 123 6.4.2.5 Examination of pregnant women 123 6.5 Species diagnosis 123 6.6 Investigations/laboratory tests 123 6.6.1 20 minute whole blood clotting test (20WBCT) 123 6.6.2 Other tests of blood coagulation 126 6.6.3 Other laboratory tests 126 6.6.4 Other investigations 127 6.7 Antivenom treatment 128 6.7.1 What is antivenom? 128 6.7.2 Indications for antivenom treatment 129 6.7.3 Inappropriate use of antivenom 130 6.7.4 How long after the bite can antivenom be expected to be effective? 130 6.7.5 Antivenom reactions 130 6.7.5.1 Prediction of antivenom reactions 132 6.7.5.2 Contraindications to antivenom: 132 Prophylaxis in high risk patients 6.7.5.3 Prevention of antivenom reactions 132 6.7.5.4 Treatment of antivenom reactions 134 6.7.6 Supply, Selection, storage and shelf-life of antivenom 135 6.7.7 Administration of antivenom 136 6.7.8 Dosage of antivenom 138 6.7.9 Recurrence of systemic envenoming 142 6.7.10 Criteria for repeating the initial dose of antivenom 142 6.8 Conservative treatment when no antivenom is available 143 6.9 Supportive/ancillary treatment 144 6.9.1 Treatment of neurotoxic envenoming 144 6.9.2 Practical guide to airway management and respiratory support 144 6.9.3 Trial of anticholinesterase 152 6.9.4 Treatment of hypotension and shock 154 6.9.5 Treatment of oliguria and acute kidney injury 156 6.9.5.1 Oliguric phase of renal failure 156 6.9.5.2 Bleeding/ blood clotting disturbances in 159 patients with acute kidney injury 6.9.5.3 Prevention of renal damage in patients with myoglobinuria 159 or haemoglobinuria 6.9.5.4 Diuretic phase of renal failure 160 6.9.5.5 Renal recovery phase 160 6.9.5.6 Persisting renal dysfunction 160 6.10 Haemostatic disturbances 160 6.10.1 Dangers of venipuncture in patients with haemostatic abnormalities 160 6.11 Treatment of the bitten part 161 6.11.1 Wound management 161 6.11.2 Bacterial infections 161 6.11.3 Compartment syndromes and fasciotomy 161 6.12 Rehabilitation 163 6.13 Discharge advice and assessment 163 6.14 Management of cobra spit ophthalmia 164 6.15 Management of snakebites at different levels of the health service 165 6.16 Summary of current evidence for treatment of snakebite envenoming 168 7 References and further reading 169 8 Annexes 185 Annex 1 Algorithm 1: Antivenom treatment of snakebite cases 187 Annex 2 Algorithm 2: Differentiating major Asian snake species by clinical syndrome 188 Annex 3 Antivenoms for treating bites by South-East Asian snakes 191 Annex 4 Pressure-immobilization and pressure pad 195 Annex 5 Measurement of central venous pressure 197 Annex 6 Measurement of intracompartmental pressure 198 Annex 7 List of Contributors 199