Scorpion Envenomation Workup

Updated: Nov 09, 2018
  • Author: David Cheng, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Workup

Laboratory Studies

Scorpion envenomation cases vary from those requiring no laboratory tests to scenarios requiring extensive hematologic, electrolyte, and respiratory analysis.

Obtain a CBC count, as Hemiscorpius lepturus has been shown to cause severe hemolysis. In addition, marked leukocytosis suggests induction of a venom-mediated systemic inflammatory response‒like syndrome.

Electrolyte evaluation is warranted in patients with venom-induced salivation, vomiting, and diarrhea.

Coagulation parameters should be measured for venom-induced defibrination because, at high concentrations, the venom is an anticoagulant. Defibrination syndrome has been reported following Mesobuthus tamulus stings.

Glucose levels should be measured to evaluate for hyperglycemia from liver and pancreas dysfunction.

Troponin and NT-proBNP elevation suggests myocarditis.

Creatine kinase and urinalysis help evaluate for venom-induced excessive motor rhabdomyolysis. Renal failure may occur secondary to hemoglobinuria from hemolysis (after H lepturus sting) or myoglobinuria from rhabdomyolysis

Obtain amylase/lipase values to assess for pancreatitis, which is common, from Tityus trinitatis stings.

Patients may have increased aspartate aminotransferase and alanine aminotransferase levels from venom-induced liver cell destruction.

Increased catecholamine, aldosterone, renin angiotensin, and antidiuretic hormone levels are detected a few hours after the sting. The increased levels persist for 6 hours, after which a gradual decline occurs.

Obtain arterial blood gas (ABG) measurements as indicated for respiratory distress or to determine acid/base status.

Additional laboratory abnormalities that may have research relevance include interleukin (IL)–1 levels, which have been reported to be elevated.

High levels of IL-6, interferon-gamma, and granulocyte-macrophage colony-stimulating factor are reported in severe envenomations.

Radiolabeled antibodies or immunoenzymatic assays help quantify the serum venom level because an association exists between the clinical signs of envenomation and this level. [29]  However, it is rarely used, owing to cost and because clinical grading is as effective. It is most likely only used as a research tool.

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Imaging Studies

Obtain a chest radiograph in cases of respiratory difficulty. Unilateral pulmonary edema may be seen on chest x-ray films because of the venom effect on pulmonary vascular permeability.

Echocardiography is more sensitive than electrocardiography and creatine kinase assays for assessing myocardial compromise after a scorpion sting. Findings show a diffuse global biventricular hypokinesis with a decreased left and right ventricular ejection fraction of approximately 0.14-0.38. This dysfunction can appear just a few hours after the sting and usually normalizes within 4-8 days. Serial echocardiography findings show that the return of left ventricular function to a normal state correlates to clinical cardiorespiratory improvement.

Color-flow Doppler study findings show mitral incompetence, probably secondary to venom-induced dilated cardiomyopathy.

Myocardial perfusion scintigraphy can also be used to investigate the contractility and perfusion of the cardiac tissue. [30]

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Other Tests

Arterial blood gas determinations show a decrease in arterial oxygenation tension and an increase in PCO2 within 15 minutes of the envenomation, findings consistent with mild metabolic acidosis.

Pulmonary artery catheterization findings may include the following:

  • Elevated systemic vascular resistance occurs up to 4 times the normal level, with elevated mean arterial pressure (MAP) of 203 mm Hg.

  • Left ventricular failure produces a MAP of 57-69 mm Hg.

  • Biventricular failure produces a MAP of 47 mm Hg.

  • Low cardiac index occurs with elevated filling pressures.

Perform serial spirometry measurements to help detect impending venom-induced diaphragmatic failure.

Electrocardiography, if indicated, should be performed. ECG changes persist for 10-12 days before normalizing. ECG changes are observed in 63% of children who have been envenomated. Rhythm disturbances are not dose-dependent but are related to the venom composition. Note the following:

  • First-degree block - 10.2%

  • Bundle-branch block - 12.8%

  • Ventricular repolarization abnormalities - 15%

  • T-wave inversion - 39%

  • ST changes - 39%

  • QTc prolongation - 53%

  • Sinus tachycardia - Most common rhythm

  • A possible sequence of ECG changes has been noted. This sequence starts with bizarre, broad-notched, biphasic, peaked T waves with a beat-to-beat variation. This bizarre T wave is followed by the appearance of tiny Q waves and then atrioventricular dissociation with an accelerated junctional rhythm.

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Procedures

Cerebrospinal fluid pleocytosis is evident on spinal tap studies.

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Histologic Findings

The local sting site shows mixed inflammatory cell infiltrates with eosinophils scattered among collagen bundles in an edematous dermis. Myocardial changes, which are most prominent at the papillary muscle and subendocardial region, include focal myocardial necrosis; myofibril destruction, especially at the I band; fine fatty deposits in the cardiac muscle fibers; interstitial edema; and increased cellularity, mainly lymphocytes and monocytes. Changes resemble interstitial hypoxia-induced myocarditis caused by large doses of catecholamines.

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