Clinical Management

Caution: do not attempt to capture snakes if you are not treained to do so!

Consult

• How does the clinical picture of  envenoming by the various sea snakes develop? 
• Biological features
• Clinical entries: Sea snakes

Comment

Unfortunatelly, tight (arterial) tourniquets are still being applied. They must not be rcommended for general use. 

One case was reported in which an Astrotia stokesii (=Hydrophis stokesii) bite led to a sudden onset of neurological symptoms and subsequent respiratory failure after cessation of stasis in the lower leg (Mercer et al. 1981).

Inquire

• time of the bite,
• local pain,
• nausea, vomiting, abdominal pain.

Assess

• state of consciousness.

Measure

• blood pressure/pulse,
• respiratory rate,
• oxygen saturation (pulse oximeter),
• urinary output.

Observe/investigate

• bite marks,
• extent and intensity of local swelling,
• cranial nerve deficits, such as ptosis, ophthalmoplegia, dysphagia, dysarthria,
• paralysis of the skeletal musculature including the respiratory musculature (→ respiratory insufficiency/respiratory failure),
• myalgia with active and passive movement and upon pressure,
• pseudotrismus,
• muscle spasms,
• dark-brown/red urine (rhabdomyolysis!),
• flank pain and renal bed sensitive to percussion.

Neurological effects

• Blood gas analysis
• Forced expiration test (peak expiratory flow)

Muscular effects

• Myoglobin in the serum/urine,
• Serum creatinine kinase (CK, CPK)
• GOT (AST)
• Serum potassium
• serum phosphate
• serum calcium

Cardiac effects

• Blood pressure, pulse
• ECG

Renal effects

• Urine output (balance, hourly)
• Serum creatinine
• Serum potassium
• Serum bicarbonate

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 (=Hydrophis schistosus) bites, 11/14 Hydrophis cyanocinctus bites and 6/9 Hydrophis spiralis bites did not involve a clinically relevant injection of venom (Reid 1975a,b,c)].
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:

1. primarily myotoxic envenoming (e.g. Enhydrina schistosa =Hydrophis schistosus): signs and symptoms arising in the skeletal musculature; secondary effects of rhabdomyolysis: dark urine (myoglobinuria), acute renal failure, cardiac dysrhythmias (hyperkalaemia);
   EMG-findings indicate a myopathy (Sitprija et al. 1971). The species of sea snake that caused both these accidents were not identified.
   E. schistosa (=Hydrophis schistosus): the venom contains only short-chain neurotoxins that require tryptophan at position 187 of the acetycholine receptor in order to be effective. This is not present in humans. This makes it clear that the venom of E. schistosa (=Hydrophis schistosus) cannot cause primary neurotoxic effects in humans, in contrast to many animals (Harris 1989, Minton 1990). However, in human envenoming a myotoxic phospholipase A is active, which causes the clinical signs and symptoms in the skeletal musculature (Fohlman and Eaker 1977).
2. neurotoxic/(myotoxic) envenoming (e.g. Hydrophis stokesii (described as Astrotia stokesii) and Laticauda colubrina): 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.

Monitoring for signs and symptoms that would indicate systemic envenoming for at least 12h. 

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 (=Hydrophis schistosus).

At least hourly

• state of consciousness,
• heart rate and rhythm,
• blood pressure,
• respiratory rate,
• symtoms & signs of rhabdomyolysis,
  • myalgia with active and passive movement and upon pressure,
  • pseudotrismus,
  • muscle spasms,
  • colour of urine,
  • flank pain and renal bed sensitive to percussion (acute renal failure)
• signs and symptoms of paralysis,

• other newly appearing signs and symptoms.

6-hourly (or more frequently if there is cause for suspicion)

• CK, GOT (AST)
• myoglobinuria,
• urine output.

Symptomatic emergency medical treatment and antivenom treatment are complementary strategies.

Antivenom must be secured as early as possible while emergency medical teratment is running.

The aim of symptomatic emergency medical treatment is the rapid correction of critical parameters (fluid balance, blood pressure, oxygenation etc.) and the maintenance of vital functions (respiratory, cardiovascular).

Symptomatic measures help bridge the gap until specific treatment (antivenom) can be administered and starts being effective. If no antivenom is available or if the required effect is not achieved with antivenom, the goal is to employ symptomatic measures until such time as the venom naturally starts losing its activity.

The aim of antivenom treatment is neutralisation of the venom. The success of antivenom treatment depends on the quality of the antivenom, the specific properties of those venom components relevant to envenoming and the time point at which antivenom is administered (neurotoxic envenoming).

Systemic signs of envenoming 

• Symtoms & signs of rhabdomyolysis
  • myalgia with active and passive movement and upon pressure,
  • pseudotrismus,
  • muscle spasms,
  • dark-brown/red urine, myoglobinuria
  • elevated CK, GOT (AST)
  • flank pain and renal bed sensitive to percussion (acute renal failure)

• cranial nerve deficits (ptosis, ophthalmoplegia, dysphagia, dysarthria),
• paralysis of the limb musculature,
• paralysis of the respiratory musculature (→ respiratory insufficiency/failure).

Early administration of antivenom should be considered if the patient has 

• nonspecific systemic symptoms (e.g. muscle pain and tenderness).

as antivenom administered within 6 hours of the bite appears to be associated with a reduction in the severity of myotoxicity (Johnston et al. 2022).

If the selected antivenom is not effective, 3 possible causes need to be considered

1. correct identification of the cause, but insufficient dose administered;
2. correct identification of the cause, but inadequate efficacy of the antivenom;
3. incorrect identification of the cause → revision of identification.

See Antivenom treatment

Snakebite. In: Therapeutic Guidelines, Melbourne 2020

Assessment of success of antivenom and of complications

Snakebite. In: Therapeutic Guidelines, Melbourne 2020

CSL Seqirus

Repeat clinical examination as above.

Complications

See Antivenom treatment

Snakebite. In: Therapeutic Guidelines, Melbourne 2020

CSL Seqirus

Comprehensive ABCDE approach
ICRC Basic Emergency Care: approach to the acutely ill and injured (SAMPLE and ABCDE approach: first module)

The guidance provided addresses major genus- or species-specific specific snakebite envenoming problems.

Clinical entries: Sea snakes

Snakebite. In: Therapeutic Guidelines, Melbourne 2020

Paralysis and respiratory failure is mainly due to mytoxic muscle damage, rarely neurotoxic effects (e.g. Hydrophis stokesii (described as Astrotia stokesii) and Laticauda colubrina; see Clinical entries: Sea snakes)

Muscle damage

Immobilisation to allow regeneration of musculature.

"Direct venom nephrotoxicity, renal ischaemia secondary to shock, disseminated intravascular coagulation with thrombotic microangiopathy (TMA), haemoglobinuria, myoglobinuria, and hyperkalaemia contribute to acute tubular necrosis.” (Warrell and Williams 2023).
In sea snake envenoming, AKI mostly occurs in the context of rhadomyolysis.
See 'Muscle injury, rhabodomyolysis' above.

•  Pain control

• Tetanus prophylaxis

• Standard wound care (as sea snake bites generally do not cause any marked local symptoms of envenoming, local complications are very uncommon).

WHO (2010)

• Immobilisation to guarantee undisturbed regeneration of the skeletal musculature.