medical management of a snake bite

Management

• Little management is required around the wound. If necrosis occurs antibiotics may be used.
• Hypotension is treated with IV fluids
• Anxiety is treated with diazepan.
• treatment of other cardiac and renal symptons is necesary
• Antivenom's should be used with caution because they invoke allergic reactions in some people.
  

Anaphylaxis:
Features:

• bronchospasm (constriction of muscles in the bronchials, lungs.)
• Facial and laryngeal oedema (swelling)
• Hypotension
• Nausea, vomiting and diarrhoea
  

Management

• lie patient flat with feet raised
• free airway
• give oxygen
• monitor BP - give 1-2l of IV fluid if needed
  
• introduce adrenaline(.5mg, repeat every 5 minutes), antihistamine (10-20mg) via IV

Rhabdomyolysis and Myoglobinuria

Snake venom contains toxins called myotoxins that affect the muscle cells causing Rhabdomyolysis and Myoglobinuria.

Myoglobinuria: is when myoglobin is excreted in the urine causing tea-like discolouration of the urine. Is associated with rhabdomyolysis and may be indicative of renal damage.

Rhabdomyolysis:

-is the breakdown of muscle fibres
-causes release of potentially toxic cellular components into circulation - includes creatinine kinase, myoglobin and potassium
-may have consequences such as hyperkalemia (release of potassium into circulation - can cause life threatening dysrhythmias and death), acute renal failure in 30% patients(from precipitation of myoglobin causing tubule blockage and/or by direct nephrotoxic effects of myglobin), hypervolemia (decrease in blood plasma volume), metabolic acidosis
-symptoms may include fever, muscle pain and/or weakness

Causes (are many):
-trauma -exercise induced -toxicologic (includes many drugs and venoms) -environmental
and many more.

Diagnosis:
-Lab studies: most useful diagnostic measure is serum creatinine kinase (CK) levels (although CK may be released into the blood stream in patients with other disorders eg acute myocardial infarction) therefore CK levels are a good but not entirely specific marker
-Urine dipstick test: may reveal the presence of myoglobin in the urine which is a definitive marker of rhadomyolysis however this is only present in about 50% of patients
-Blood tests for other markers eg elevated potassium levels

Treatment:
-treatment of underlying condition eg snake toxins
-fluid replacment - saline
-potassium may need correcting
-alkaline diuresis may prevent renal damage

Snake Venom Detection Test Kit

Principles of use
· CLS snake venom detection test kit (SVDK)
· Developed specially for snakes bites in Australia
· Can detect as low as nanogram quantities of venom
· Based on enzyme linked immunosolvent assay (ELISA)
o Wells coated with specific antibodies for the venom antigens
o If venom is present, it is bound to the corresponding well
o Further reactants added indicate the positive wells by producing a blue colour
· 8 Wells
o 5 Wells for 5 common snake venoms
o 1 negative control (must not change colour)
o 1 positive control (must change colour)
o 1 blank well
· Which antivenom to use
o Well 1 positive – Tiger snake antivenom
o Well 2 positive – Brown snake antivenom
o Well 3 positive – Black or Tiger snake antivenom
o Well 4 positive – Black Adder antivenom
o Well 5 positive – Taipian or polyvalent antivenom
o Only well 7 positive – No venom detected
o No well positive or well 7 not positive – Test kit failure


Samples to test on
· Urine
· Blood – unreliable due to high false positive results, resultant from unspecific binding with plasma proteins
· Bite site swab – importance of not washing site
· Swab from fang of dead snake – beware of finger pricks
· Affected bandage or clothing segment


Further notes
· Positive test result does not mean antivenom is required in the absence of clinical signs
· Conversely, negative result doesn’t mean there is no envenomation
· After sufficient antivenom is given, test kit should report negative