Adder (Vipera berus) bite

Essentials

  • Vipera berus, i.e. the common European adder (or viper) is widespread in northern, central and eastern Europe, Britain, as well as Asia.
    • The adder or viper is the only naturally occurring poisonous snake in the Nordic countries.
    • In Finland, the annual number of bites is estimated at 50–150; there are no exact statistics available.
  • Fatal bites are rare in healthy adults but possible. Risk groups include children, elderly people, multimorbid patients and pregnant women.
  • The exact composition of the venom is unknown, and it may vary.
    • The venom causes direct destruction at the bite site and elsewhere in the body depending on its systemic transportation (proteolysis, haemolysis, cytotoxic effects).
    • In addition, it may release mediators (such as histamine, bradykinin, serotonin), which may lead to an anaphylactoid reaction.
    • Systemically, the venom may trigger a sepsis-type cytokine storm.
  • The bite may be a warning without venom, i.e., a ‘dry bite’. On the other hand, symptoms may develop with significant delay; make sure to follow up the patient for a sufficiently long time!
  • Moving or agitation after the bite will speed up absorption of the venom through lymph vessels into the systemic circulation.
    • At the accident site, the person should not be asked to walk, and the bite site should not be touched.
    • Any jewellery or tight clothes should be removed before the site begins to swell.
    • All other actions (such as applying a tourniquet, sucking the venom, applying ice cubes to the site, etc.) are either harmful or useless.
  • Glucocorticoids (in OTC snake bite kits or equivalent given at the accident site or later therapy at hospital) have not been shown to be beneficial regarding the severity of the developing symptoms or subsequent healing.
  • Essential aspects of treatment
    • Keep the patient and the bite site still and calm. Ensure sufficient analgesia (e.g. opioids) at the time of initial treatment, already.
    • Ensure constant monitoring: any organ failure may develop suddenly. Treat organ failure symptomatically.
    • Follow up local symptoms, repeatedly marking the limits of the lesions with a marker and measuring the limb circumference
    • Consider starting administration of the specific antidote at an early stage. See local guidelines.

Diagnosis and follow-up

  • Bite marks are rarely typical and of no significance for assessing follow-up or treatment.
    • An adder’s teeth are about 4 mm long and 3–9 mm apart.
    • There may be only one mark or as many as four, and as swelling and discolouration proceed, these may be difficult to distinguish.
  • The symptoms and findings may vary; see Table T1.
  • The initial symptoms may be confusingly mild and progress slowly (for as long as 72 h); severe poisoning may develop with delay.
  • If an adder was seen to bite, the patient should be admitted for follow-up even in the absence of symptoms.
  • Even if it is not sure whether an adder bit at all, patients with even mild symptoms (swelling or discolouration around the assumed bite site, more than mild pain, general symptoms) should be admitted for follow-up.
  • If a healthy adult develops no symptoms (severe / more extensive pain, oedema, discolouration, general symptoms) in 2-h follow-up, discharge may be considered.
    • In any other case, the patient should be followed up for at least 24 h.
    • Risk groups (children, multimorbid patients, pregnant women) should generally be followed up for a longer time.
  • Organ failure may have a sudden onset and should be prepared for.
  • The limits of the lesions should be repeatedly marked with a marker and the limb circumference measured to follow up on local symptoms.
  • If severe symptoms (hypotension, shock, respiratory distress, etc.) develop quickly, their cause may be an anaphylactic reaction rather than, or in addition to, a toxic reaction (see (Anaphylaxis)).

Workup

  • Limb circumference, peripheral pulses, sensation and temperature
  • Tests such as basic blood count, coagulation, haemolysis, liver and kidney function, fluid and electrolyte balance, acid-base balance, lactate, myoglobin/CK and ECG, as considered necessary and depending on the symptoms

Treatment

  • The bite site should be kept still and the patient calm.
    • Immobilization of the limb, keeping it elevated, and bed rest
    • Good initial analgesic treatment using short-acting opioids or paracetamol, for instance (avoid NSAIDs)
  • Follow-up and management of the level of consciousness, breathing and circulation and other organ failures according to the usual principles. Patients with significant general symptoms should be monitored intensively at an observation ward or transferred to an intensive care unit, high-risk patients more readily.
  • The wound should be cleaned avoiding handling the bite site as far as possible. Vesicles should not be punctured.
  • Other possible drug treatment
    • Tetanus immunization, unless previous immunization is still effective (Tetanus).
    • Glucocorticoids or antimicrobials are not given routinely because their effectiveness has not been shown.
    • Low molecular weight heparin should be started according to normal practice in case of prolonged immobilization or if venous thrombosis is detected during the treatment (Prevention of venous thromboembolism) (Deep vein thrombosis).
  • Surgery
    • Surgical removal of the venom is not useful and should not be done.
    • If compartment syndrome is suspected, a surgeon should be consulted (Muscle compartment syndromes).

Anaphylactic or anaphylactoid reaction

Antivenom (ViperaTAb®)

  • The antivenom is made of serum from lambs injected with snake venom [Evidence Level: C].
  • It is the more effective the earlier the treatment is started. Starting antivenom treatment after more than 48–72 h is probably no longer useful.
    • Starting treatment is recommended if the patient has systemic symptoms clearly consistent with poisoning or extensive local symptoms, more readily for risk groups.

Table 1. Symptoms and findings related to adder bite
Onset of symptoms Local symptoms
  • Onset usually soon after the bite but in some cases symptoms may be mild and progress for up to 2–3 days.
  • They may last several weeks.
Systemic symptoms
  • After an average of 0.5–4 hours (once the venom has been absorbed); in some cases with delay
Local symptoms Pain, dark/purple discolouration and swelling spreading proximally
Subcutaneous haematoma and blistering possible
Necrosis or compartment syndrome rarely develop but patients should be monitored for these.
Intestinal symptoms Vomiting, diarrhoea, abdominal pain and paralytic ileus
Central nervous symptoms Irritability, headache, convulsions, impaired consciousness, paraesthesias, visual disturbances
Cardiovascular symptoms Vasodilation, hypotension, hypovolaemia, conduction disorders and arrhythmias, myocardial ischaemia
In the most extreme cases, hypovolaemic and/or anaphylactoid shock
Renal symptoms Oliguria, proteinuria, haematuria (renal damage)
Blood Haemolytic anaemia, leucocytosis, thrombocytopenia, rarely generalized disseminated intravascular coagulopathy (DIC)
Other symptoms Rarely rhabdomyolysis, pancreatitis, pulmonary oedema
Late symptoms (Limb) muscle rigidity, restricted movement, dysaesthesias, swelling tendency and dark discolouration may last several weeks or months. Permanent discolouration, chronic pain and neurological symptoms are also possible.


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