Insect and Spider Envenomations - Web viewVenom immunotherapy: if anaphylactic reaction to insect...
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Insect Envenomations Ants Bull ants – 3% are allergic; risk death if on ACE inhibitors Red fire ants – very aggressive; sterile pustules for after bite Ticks Venom: alpha-latrotoxin; causes release of Ach and catecholamines at nerve endings in autonomic nervous system massive synaptic vesicle exocytosis from presynaptic terminal Investigation: none helpful Discharge criteria: asymptomatic for 2 hours after bite / antivenom Redback Spider Venom: Toxin in tick salivary gland – neurotoxin (holocyclotoxin) similar to botulinum toxin act at neuromuscular junction to inhibit release of Ach; also haemostatic and antiinflamm agents to aid Mouse Venom: envenomatin rate <5%; toxin similar to funnel web so treated as funnel web anyway Funnel Web Spider Venom: most toxic known; all deaths from male spiders; most bites don’t result in envenomation (10-25% envenoming rate); bites usually witnessed; contains neurotoxins (atracotoxins) spontaenous repetitive firing and prolongation of action potentials neurotransmitter release from somatic and autonomic nervous system neuromuscular and autonomic excitation Investigation: none helpful in diagnosis; may have CK Bee 1-4 deaths/year in Australia; usually due to anaphylaxis Swarming: 15% mortality; death highly likely if >20 stings/kg Management Treat all big black spider bites as Funnel Web Pressure immobilisation technique: at 55mmHg (don’t occlude circulation); splint joints above and below; keep victim and limb completely at rest Indicated if : apply ASAP if life threatening envenomation with rapid venom absorption: Funnel Web spider, mouse spider, big black spider in S/E Australia; bee / wasp / ant stings if allergic (also used in all snakes, Blue-ringed octopus, cone shell) NOT indicated if : redback spider, other non-Funnel spiders, fish stings, scorpions, centipedes, beetles, jelly fish Remov e: after 1 hour if no evidence of envenoming and Funnel Web AV available if no features of envenoming at 2 hours, then unlikely observe for 4 hours after time of bite Pros : safe, simple; retards venom transport and absorption into Antivenom Administration: have full resus facilities avaiable when give; safe in children, pregnancy and lactation; usually given IM; if given IV, dilute 1:10 in 100ml N saline and give over 20-30 minutes via pump (advantage as can stop infusion if allergy); when discharge, give advice Re: serum sickness
Transcript of Insect and Spider Envenomations - Web viewVenom immunotherapy: if anaphylactic reaction to insect...
Insect Envenomations
Ants Bull ants – 3% are allergic; risk death if on ACE inhibitorsRed fire ants – very aggressive; sterile pustules for after bite
Ticks
Venom: alpha-latrotoxin; causes release of Ach and catecholamines at nerve endings in autonomic nervous system massive synaptic vesicle exocytosis from presynaptic terminalInvestigation: none helpfulDischarge criteria: asymptomatic for 2 hours after bite / antivenom administration Vs funnel web: small and shiny; progressive / delayed pain; usually benign; neuromuscular blockade (weak, paralysis); ice 1st; SSU admission
Redback Spider
Venom: Toxin in tick salivary gland – neurotoxin (holocyclotoxin) similar to botulinum toxin act at neuromuscular junction to inhibit release of Ach; also haemostatic and antiinflamm agents to aid attachment
Mouse Spider
Venom: envenomatin rate <5%; toxin similar to funnel web so treated as funnel web anyway
Funnel Web Spider
Venom: most toxic known; all deaths from male spiders; most bites don’t result in envenomation (10-25% envenoming rate); bites usually witnessed; contains neurotoxins (atracotoxins) spontaenous repetitive firing and prolongation of action potentials neurotransmitter release from somatic and autonomic nervous system neuromuscular and autonomic excitationInvestigation: none helpful in diagnosis; may have CKPrognosis: non-cardiogenic pulmonary oedema is major cause of mortalityVs redback: big and hairy; immediate pain; potentially fatal; NM excitation (fasciculation, tone); PIB indicated; ICU admission
Bee 1-4 deaths/year in Australia; usually due to anaphylaxisSwarming: 15% mortality; death highly likely if >20 stings/kg
Management
Treat all big black spider bites as Funnel WebPressure immobilisation technique: at 55mmHg (don’t occlude circulation); splint joints above and below; keep victim and limb completely at restIndicated if: apply ASAP if life threatening envenomation with rapid venom absorption: Funnel Web spider, mouse spider, big black spider in S/E Australia; bee / wasp / ant stings if allergic (also used in all snakes, Blue-ringed octopus, cone shell)NOT indicated if: redback spider, other non-Funnel spiders, fish stings, scorpions, centipedes, beetles, jelly fishRemove: after 1 hour if no evidence of envenoming and Funnel Web AV available if no features of envenoming at 2 hours, then unlikely observe for 4 hours after time of bitePros: safe, simple; retards venom transport and absorption into circulation; avoids use of arterial tourniquet; can be left in place for long periods without patient discomfortClose observation: as above Other: clean wound, analgesia, ADT; ice: apply to bite site wrapped in cloth and hold in place with light bandage; don’t use for >10mins, remove if skin erythemaAntivenom available: funnel web, red backVenom immunotherapy: if anaphylactic reaction to insect venom; 80-90% protective against further severe reactions; refer to immunologist if anaphylaxis and discharge with epipen
Antivenom
Administration: have full resus facilities avaiable when give; safe in children, pregnancy and lactation; usually given IM; if given IV, dilute 1:10 in 100ml N saline and give over 20-30 minutes via pump (advantage as can stop infusion if allergy); when discharge, give advice Re: serum sicknessPre-medication: no longer indicated routinely (with adrenaline only if equine / antivenom allergy known); allergic reaction <2%Complications: serum sickness risk 11-16%
