Is the patient envenomed?
Is it likely that a clinically relevant injection of venom has taken place?
- time of the bite,
- nausea, vomiting,
- blurred vision, double images,
- flank pain.
- state of consciousness.
- blood pressure/pulse,
- respiratory rate,
- urinary output.
- bite marks,
- favouring of the affected limb (muscle pain),
- signs of paralysis:
- cranial nerve deficits, such as ptosis, ophthalmoplegia, dysphagia, dysarthria,
- paralysis of the skeletal musculature including the respiratory musculature (→ respiratory insufficiency/respiratory failure),
- muscle spasms,
- urine (dark, brown/black or red),
- passive movement of the musculature painful,
- muscle compression painful,
- flank pain and renal bed sensitive to percussion.
- cause of the accident by detection of specific venom antigen,
- venom concentration in the serum using the ELISA method (if clinically proven and standardised test kits are commercially available),
- arterial blood gases,
- ECG (cardiac dysrhythmia, signs of hyperkalaemia).
The symptoms and degree of envenoming depend not only on the amount of venom injected and numerous other variables, but also on the time that has elapsed since the bite. This variable factor must be taken into account when making the following decisions:
- exclusion of envenoming,
- the time interval between clinical examinations,
- emergency care.
The fact that a patient has been bitten by a sea snake and the presence of bite marks do not automatically allow the conclusion that a clinically relevant injection of venom has taken place [39 of 55 Enhydrina schistosa bites, 11/14 Hydrophis cyanocinctus bites and 6/9 Hydrophis spiralis bites did not involve a clinically relevant injection of venom (Reid 1975b)].
Local signs, such as swelling and pain at the site of the bite, are usually absent and thus completely unreliable as clinical indicators of an injection of venom.
There seem to exist 2 forms of Hydrophiidae envenoming with different courses:
- primarily myotoxic envenoming (e.g. Enhydrina schistosa): signs and symptoms arising in the skeletal musculature; secondary effects of rhabdomyolysis: dark urine (myoglobinuria), acute renal failure, cardiac dysrhythmias (hyperkalaemia);
- neurotoxic/(myotoxic) envenoming (e.g. Astrotia stokesii): initially prominent are acute neurotoxic symptoms that occur a short time after the bite and their corresponding signs: ptosis, ophthalmoplegia, dysphagia, dysphonia; progressive paralysis of the respiratory musculature with respiratory insufficiency and failure.
Exclusion of clinically relevant envenoming
Monitoring for signs and symptoms (see above) that would indicate systemic envenoming for at least 12(–24) h (recommended examinations see Therapy phase: Hospital: Monitoring of the patient):
- preparalytic phase: within minutes,
- preclinical phase of effects of the venom on the skeletal musculature: 0.5–4 h (Reid 1979).
According to observations by Reid in Penang (Malaysia) severe envenoming can be excluded if there is no skeletal muscle pain upon movement 2 h after the bite (Reid 1979). However, these observations were made chiefly in patients who had been bitten by Enhydrina schistosa.