Stings: Treatment, symptoms, advice and help
Several insects like honeybees, bumble bees, hornets, wasps, yellow jackets, and fire ants and reptiles like scorpions are capable of injecting venom into humans and animals. This is called a sting. Scorpions cause severe or lethal envenoming and insect stings (e.g. bees, wasps) are causes of sometimes lethal anaphylaxis.
Stings: Incidence, age and sex
The incidence varies widely in different parts of the world. Scorpion stings are common in North and South Africa and Asia but uncommon in the UK. Insect stings are more common in UK especially in the months of August and September. All age groups are vulnerable but stings are more likely to be lethal in smaller babies.
Signs & symptoms of stings: Diagnosis
Stings can result in three broad classes of effects.
Local effects such as pain, sweating, swelling, redness, bleeding, bruising and blistering.
General systemic effects: Headache, nausea, vomiting, diarrhoea, abdominal pain, tachycardia or bradycardia, hypertension or hypotension, dizziness, collapse, convulsions and shock.
Specific systemic effects such as paralysis, myotoxicity, coagulopathy, nephrotoxicity, cardiotoxicity, pulmonary oedema, necrosis and convulsions may occur.
In scorpion envenomation, excitatory neurotoxins cause an autonomic storm with profuse sweating, variable cardiac effects and cardiac failure, sometimes with pulmonary oedema. Myotoxicity can initially be silent, then present with generalized muscle pain tenderness, myoglobinuria and huge rises in serum creatine kinase (CK).
Diagnosis: Envenoming by stings is sometimes obvious but should also be considered in selected cases of unexplained paralysis, myotoxicity, coagulopathy, nephrotoxicity, cardiotoxicity, pulmonary oedema, necrosis, collapse and convulsions. History, examination and laboratory findings will help to confirm or exclude a diagnosis. The screen for envenoming includes full blood count, coagulation screen, urea and electrolytes, creatinine, CK and ECG.
Causes and prevention of stings
Stings are caused by insects like bees, wasps and reptiles like scorpions. To prevent getting bitten or stung by insects, ensure as far as possible, that the skin is covered with clothing by wearing a long sleeved shirt, long pants, socks, and a hat; avoid areas where bees and wasps nest and dark corners where scorpions lurk and use windows & door screens to prevent insects from getting inside residential zones.
Cardiotoxicity is often secondary, and symptoms and signs are non-specific in most cases.Haemotoxins cause coagulopathy which may present as bruising and bleeding from the bite site, gums and intravenous sites. Renal damage presents with changes in urine output- polyuria, oliguria or anuria or rises in creatinine and urea. In cases with intravascular haemolysis, secondary renal damage is likely.
First aid - the key principles are: supporting vital systems, delaying or preventing the onset of envenoming and avoiding harmful treatments (e.g. electric shock, cut and suck, tourniquets, cryotherapy).
The two main aspects are treating the effects with specific anti-venom and supportive management of the organ systems affected and of the whole patient. All patients receiving antivenin are at risk of both early and late adverse reactions, including anaphylactic/ anaphylactic reactions and serum sickness. Anticholinesterases are used as an adjunctive treatment for post-synaptic paralysis. Prazosin (an a-adrenoceptor antagonist) is used in the management of hypertension or pulmonary oedema in scorpion sting.
Tetanus is a risk in some types of bite/sting, such as snakebite, but intramuscular toxoid should not be given until any coagulopathy is reserved. Mechanical ventilation is vital for established respiratory paralysis that will not reverse with anti-venom, and may be required for prolonged periods: up to several months in some cases.