Neobook — clinical reference

T63.0 + (X20.99/W59.99)

DESCRIPTION

In the majority of snakebite incidents, the offending snake is not identified. The table below illustrates the three main envenomation syndromes seen in South Africa: cytotoxic, neurotoxic and haemotoxic.

Snake species

Envenomation syndromes
Cytotoxic	Neurotoxic	Mixed cytotoxic & neurotoxic	Haemotoxic
Puff adder, Gaboon adder, spitting cobras (Mozambique, black-necked, zebra), stiletto snake, night adders, horned adders	Black and green mamba, non-spitting cobras (Cape, forest, snouted)	Rinkhals, Berg adder, Peringuey’s adder, desert mountain adder, garter snakes, shieldnose snake, coral snake	Boomslang, vine snakes

Clinical features of envenomation

Envenomation syndromes
Cytotoxic	Neurotoxic	Mixed cytotoxic & neurotoxic	Haemotoxic
Pain, swelling, bruising, blisters, necrosis, regional lymphadenopat hy, hypotension, coagulopathy, compartment syndrome	Pins and needles, metallic taste, visual disturbances, ptosis, drowsiness, sweating, drooling, dysphagia, progressive weakness, respiratory paralysis	Combined cytotoxic and neurotoxic features	Spontaneous bleeding (can present late >24 hours after bite), headaches, dizziness, fainting

Antivenom (when indicated)

Envenomation syndromes
Cytotoxic	Neurotoxic	Mixed cytotoxic & neurotoxic	Haemotoxic
Polyvalent antivenom for Puff adder, Gaboon adder, and Mozambique spitting cobra only	Polyvalent antivenom for all species	Polyvalent antivenom for rinkhals only	Boomslang monovalent antivenom for boomslang bites only

Table 19.1: Presentation and management of envenomation syndromes
To find pictures for the identification of snakes: http://www.cmej.org.za/index.php/cmej/article/view/2546/2581

GENERAL MEASURES

Most snakebites will not result in death.
Monitor all cases of snakebite for 24 hours.
Supportive and symptomatic management with/without antivenom is required.
Mechanical ventilation may be needed in some cases of neurotoxic envenomation.
Cases of haemotoxic envenomation may require fluid resuscitation including blood products.
True compartment syndrome is extremely rare in cytotoxic snakebites, as swelling is localised to the subcutaneous tissues. Fasciotomy is seldom indicated.

MEDICINE TREATMENT

Cleanse wound:

Chlorhexidine 0.05% in water.

Antibiotics:
T79.3 + (X20.99/W59.99)

Antibiotics are seldom indicated unless there is evidence of secondary infection.

Amoxicillin/clavulanic acid, oral, 875/125 mg 12 hourly for 5 days

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Immunisation, primary or booster:
(Z23.5)

Tetanus toxoid vaccine, IM, 0.5 mL immediately, if not previously immunised within the last 5 years.

In unimmunised or partially immunised patients:

Tetanus immunoglobulin, human, IM, 250 units immediately.

Analgesia

For mild pain:

Paracetamol, oral, 500mg-1 g 4–6 hourly when required (to a maximum of 4 g in 24 hours)
- Maximum dose: 15 mg/kg/dose.

For severe pain:

ADD

Morphine, IV, to a total maximum dose of 10 mg (See prescribing information for specific medicines for individual dosing and monitoring for response and toxicity).

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CAUTION
Opioids increase the risk of respiratory depression particularly for neurotoxic envenomation, and if required, should only be used with caution in severe uncontrolled pain.

Note:
NSAIDS are not recommended as they increase the risk of bleeding and renal failure, especially in patients with severe cytotoxic bites.

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CYTOTOXIC AND NEUROTOXIC SNAKEBITE

T63.0 + (X20.99/W59.99)

MEDICINE TREATMENT

Polyvalent antivenom

Used in some cytotoxic and neurotoxic envenomations, only where indicated (see indications below).
Available from South African Vaccine Producers (refer to the table above for contact details). See package insert for full details.

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Note:

- In most cases, patients do not need and should not be given antivenom.
- Adverse reactions to antivenom such as allergic reactions (10-30%) are common and may be severe. Pre-medication with adrenaline (epinephrine) may reduce the risk of severe adverse reactions to polyvalent snake antivenom.
- The dose of antivenom is the same for adults and children.
- Monitor for any deterioration in respiratory function as patients may need ventilation whether or not polyvalent antivenom has been given.
- Antivenom should be given as soon as possible, however, administration may be considered even as late as 48-72 hours after the bite if there is continued clinical deterioration that indicates ongoing venom activity.

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Indications for polyvalent antivenom:

Signs of neurotoxicity.
Positively identified puff adder, Gaboon adder, Mozambique spitting cobra or rinkhals bites AND evidence of progressive severe cytotoxicity.
Unidentified snakebite AND evidence of progressive severe cytotoxicity.
Severe local cytotoxicity is defined as:
- Swelling of the whole hand or foot within 1 hour
- Swelling to the knee or elbow in less than 6 hours (or two joints above the bite site in 6 hours)
- Swelling of the whole limb in less than 12 hours
- Swelling progression > 5 cm/hour
- Discolouration of the skin / necrosis at the bite site
- A threatened airway due to swelling
- Evidence of complications e.g. pseudo- or true compartment syndrome
- Additional features of severe systemic cytotoxicity include:
  - Haematological abnormalities: Hb <8 g/dL, thrombocytopaenia, (<100 x 10⁹ /L), raised INR or abnormal thromboelastography (if available)
  - Arrhythmias (rare).
  - Shock

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Note:

Polyvalent antivenom is ineffective against the venom of: night adders, berg adders and other smaller adders, boomslang, and vine/twig snakes.

CAUTION

Never administer antivenom without being prepared to manage acute anaphylaxis.

Administration and polyvalent antivenom dose:

Pre-treat with adrenaline (epinephrine), SC, 0.25 mL of 1:1000 solution.

Note:
This is contraindicated in patients with IHD, stroke, uncontrolled hypertension, and tachyarrhythmia.

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Polyvalent snake antivenom, slow IV infusion.
- This guidance refers to the antivenom produced by South African Vaccine Producers. For any other product refer to the relevant package insert for guidance.
- 1 ampoule contains 10 mL antivenom.
- Cytotoxic snakebite (unidentified snake): give 50 mL,
- For puff adder bites: the initial dose is 80 mL.
- For Mozambique spitting cobras the initial dose is 100 mL
- Neurotoxic snakebite: give 80–100 mL (and up to 200 mL in black mamba bites).
- Dilute in sodium chloride, 0.9%, 200mL; for example, if 8 ampoules are required, remove 80 mL from 200 ml saline bag and replace with 80 mL antivenom.
- Administer IV, over 30 minutes.
- Reassess once the infusion is completed. A repeat dose may be given if there is ongoing neurotoxicity or cytotoxicity.

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BOOMSLANG SNAKE BITE

T63.0 + (X20.99/W59.99)

DESCRIPTION

Boomslang venom is haemotoxic. A consumptive coagulopathy with hypofibrinogenaemia and bleeding usually sets in within 6–36 hours after the bite.

GENERAL MEASURES

In suspected boomslang bite, a whole blood clotting time is a useful bedside test, especially in rural areas. Place 5 mL of blood in a dry glass test tube and leave at room temperature for 20 minutes. Normal clotting time varies from 5–20 minutes. It is important to repeat these over a few days.
Other investigations include FBC, activated PTT, prothrombin time (INR), fibrinogen, D-dimer, and monomers.

Note:

Polyvalent antivenom is not effective in boomslang bites.

Boomslang monovalent antivenom

Indicated for all boomslang bites with evidence of haemotoxicity. Available from South African Vaccine Producers (refer to the table above for contact details). See full details in the package insert.

CAUTION

Never administer antivenom without being fully prepared to manage acute anaphylaxis.

Boomslang monovalent antivenom, slow IV infusion, 20 mL diluted in 50–100 mL sodium chloride, 0.9% or dextrose 5%, administered over 5–10 minutes.
- The dose of antivenom is the same for adults and children.
- Spontaneous systemic bleeding should stop within 15–30 minutes and blood coagulability be restored within 6 hours of administering antivenom.
- Re-evaluate regularly: Consider a repeat dose of 10 ml of antivenom if there is ongoing evidence of coagulopathy after 6 hours.

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SNAKE VENOM IN THE EYE

S05.9 + (X20.99/W59.99)

DESCRIPTION

Snake venom in the eye, particularly from various species of spitting cobras and rinkhals, can cause local cytotoxic effects. Clinical presentation ranges from periocular swelling and mild conjunctival and corneal inflammation, to frank corneal ulceration and perforation with eventual blindness.

MEDICINE TREATMENT

Instil local anaesthetic:

Local anaesthetic ophthalmic drops, e.g.:
Tetracaine 1%, drops (if available), instil 1 drop into the affected eye(s) before irrigation.
- Irrigate the eye thoroughly for 15–20 minutes with water or sodium chloride, 0.9% to dilute or remove the toxin.

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Topical antibiotics:

Chloramphenicol 1%, ophthalmic ointment 8 hourly for 7 days.
- Apply chloramphenicol eye ointment and cover the affected eye with an eye patch.

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Note:

Do not instil polyvalent antivenom in the eye or give systemically.

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REFERRAL

Refer all patients to an ophthalmologist.

Click here to access the pdf.

Standard Treatment Guidelines and Essential Medicines List for South Africa, Adult Hospital Level, 2020-2024_Version 2.0_27 March 2025

Chapter 19 Poisoning_19.2 Snake Bites

Snake Bites

DESCRIPTION

GENERAL MEASURES

MEDICINE TREATMENT

Drugs mentioned

ICD-10 codes