Emergency Medicine

Toxinology Emergencies 195

SNAKE BITES

Viper (adder) snake bites

DIAGNOSIS

1 Snakes of the viper species include the North American rattlesnake, the
African rhinoceros viper and the adder, which is the only naturally occur-
ring venomous snake in the UK.

2 Local effects of an adder bite include pain, bruising, swelling and local
lymphadenopathy within hours of the bite. However, fewer than 50% of bites
are associated with envenomation, and occasionally systemic poisoning may
occur with no local reaction.

3 Systemic envenomation causes:
(i) Early features including non-allergic anaphylaxis with transient
syncope and hypotension, angioedema, urticaria, abdominal
pain, vomiting and diarrhoea.
(ii) Late features including recurrent or persistent hypotension, ECG
changes, spontaneous bleeding, coagulopathy, adult respiratory
distress syndrome and acute renal failure.

4 Gain i.v. access, and send blood for FBC, clotting screen, U&Es and liver
function tests (LFTs).

5 Perform an ECG and a CXR in severe cases.

MANAGEMENT

1 Reassure the patient, apply a firm bandage proximal to the bite, immobilize
the dependent limb and transport the patient rapidly to hospital.

2 Treat non-allergic anaphylaxis reactions with oxygen, adrenaline (epinephrine)
and f luids (see p. 27).

3 Give European viper venom antiserum for significant adder envenomation:
(i) Indications for viper venom antiserum include:
(a) hypotension
(b) ECG changes
(c) vomiting
(d) bleeding
(e) extending limb swelling within 4 h of the bite.
(ii) Add one 10 mL vial to normal saline 5 mL/kg diluent and infuse
over 30 min, repeated as indicated.
(iii) Have adrenaline (epinephrine) immediately available for
anaphylactic reactions to the antivenom.

4 Give tetanus prophylaxis, and refer all patients to the medical team for
admission, even in the absence of initial symptoms or signs.