Tests
1st tests to order
prothrombin time, PTT, fibrinogen, and D-dimer
Test
Crotalinae envenomation may cause venom-induced consumption coagulopathy, a syndrome with similarities to disseminated intravascular coagulation.
Baseline and subsequent coagulation studies should be drawn in patients with symptomatic Crotalinae envenomations. In asymptomatic patients or dry bites, these studies should be repeated prior to patient discharge.
Result
prolonged prothrombin time and/or PTT, low fibrinogen levels, elevated D-dimer
CBC
Test
Should be obtained in suspected Crotalinae envenomation, because it may cause thrombocytopenia by coagulation cascade activation and platelet consumption.
Coagulopathy may result in hemorrhage with subsequent anemia.
Result
may be normal; anemia, thrombocytopenia
electrolytes, BUN, and creatinine
Test
Reasonable to obtain as a baseline in both Crotalinae and Elapidae envenomations.
Acidosis may result from respiratory compromise after Elapidae envenomation.
Metabolic acidosis with a wide anion gap may occur from hypotension and lactic acidosis in Crotalinae envenomation.
Myoglobinuric renal failure may complicate Crotalinae envenomations with significant rhabdomyolysis.
Result
acidosis, elevated anion gap acidosis, high levels of BUN and creatinine
arterial blood gas
Test
May be considered in Crotalinae and Elapidae envenomations with signs of respiratory distress.
Elapidae envenomation may cause hypoxemia and respiratory acidosis from paralysis of the muscles of respiration.
Crotalinae envenomation may cause hypoxemia and respiratory acidosis from increased pulmonary capillary permeability and pulmonary edema. It may also cause metabolic acidosis from hypotension and cardiovascular shock.
Result
hypoxemia, metabolic acidosis, respiratory acidosis
creatine kinase (CK)
Test
CK levels may be considered in patients with severe local toxicity to evaluate for rhabdomyolysis and the risk of myoglobinuric renal failure.
In patients with severe local effects from Crotalinae envenomation, serial CK measurements should be performed every 4 to 6 hours.
Result
high levels
lactate
Test
Test may be used in patients with severe Crotalinae envenomation to follow the degree of microvascular hypoperfusion and guide resuscitation.
Baseline and subsequent tests should be performed.
Result
high levels
urinalysis
Test
Urinalysis with microscopy may aid in the diagnosis of myoglobinuria in Crotalinae envenomation in patients with severe local toxicity.
Baseline and subsequent tests should be performed.
Result
myoglobinuria
ECG
Test
Crotalinae envenomation has been reported to cause myocardial infarction, arrhythmia, and conduction delay.
The mechanism of injury is unclear but may be due to vasospasm, disseminated intravascular coagulation, or a direct toxic effect of venom on the myocardium.[28][29][30]
Initial and subsequent ECG should be performed in patients with chest pain, palpitations, or other signs or symptoms of cardiovascular organ system derangement.
A high level of suspicion for hyperkalemia should be maintained during ECG interpretation.
Result
ST elevation, arrhythmia
chest x-ray
Test
Pulmonary edema may occur following Crotalinae envenomation, due to cardiac failure or increased pulmonary capillary permeability, and may lead to death in some cases.[25]
Initial and subsequent x-rays should be performed in patients with signs or symptoms of respiratory compromise..
Result
pulmonary edema
wound x-ray
Test
Retained snake fangs are rare following envenomation by North American pit vipers but have been reported to be visible with plain x-rays.[22][23][24]
If signs or symptoms of foreign body are present, a plain radiograph of the wound should be obtained to evaluate for foreign body.
Result
radiopaque foreign body
negative inspiratory force (NIF) test
Test
Elapidae envenomation may cause weakness or paralysis of the muscles of respiration.
The NIF test may help identify developing respiratory insufficiency before it becomes clinically evident.
Initial and subsequent tests should be performed.
Result
paralysis of muscles of respiration
Tests to consider
CT/MRI
Test
Generally a CT or an MRI for evaluation of foreign body following snakebite is not necessary.
If there is a high suspicion for foreign body and a normal plain radiograph, CT/MRI may be performed to evaluate for retained radiolucent foreign body.
Recurrent soft-tissue infections, persistent pain, or deep-space infections should raise suspicion for retained foreign body despite negative plain radiographs.
Result
radiolucent foreign body
compartment pressure
Test
Compartment syndrome may develop as a result of local effects following Crotalinae envenomation.
Compartment pressures should be measured serially when there is suspicion for compartment syndrome. It can be measured using a commercial device, such as the Stryker intracompartmental pressure monitor device, or an arterial line set-up.
Result
elevated compartment pressure
central venous line with central venous pressure (CVP) transduction
Test
Crotalinae envenomation may cause hypotension by third-spacing with intravascular depletion or by direct cardiac myotoxicity with impaired cardiac pump function.
The test may help guide the resuscitation of hypotensive patients.
A low CVP suggests intravascular depletion requiring intravenous hydration.
An elevated CVP suggests pump dysfunction, which may be responsive to vasopressors.
Result
low or high central venous pressures
arterial line with pressure transduction
Test
Continuous arterial pressure transduction may help guide the management of Crotalinae venom-induced hypotension.
Result
low mean arterial pressure
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