Laboratory Studies
Laboratory data usually are not helpful in patients with mild symptoms. Patients who present with anaphylaxis resulting from a wasp sting may benefit from studies such as arterial blood gas assessment, CBC count, electrolytes, BUN and creatinine, glucose, serum alpha/beta tryptases (which elevate within 15 min to 3 h from the onset of symptoms), histamine levels (which elevate from 15 min to 1 h from the onset of symptoms), [7] and liver function studies in order to provide their baseline values as part of the admission profile.
Patients may have mild leukocytosis related to demargination from catecholamine release.
Arterial blood gas values reflect the pathophysiology of the illness progression. The initial pH level should be normal or may be slightly elevated to reflect a respiratory alkalosis due to anxiety-produced hyperventilation with the corresponding decrease in the partial pressure of carbon dioxide (PCO2). As the patient becomes more hypotensive, the pH level may begin to fall. Conversely, this fall may also be due to increased respiratory distress with bronchospasm. This can be due to several factors. A respiratory acidosis can be caused by carbon dioxide retention from the respiratory bronchospasm and the development of pulmonary edema. At this point, the partial pressure of oxygen (PO2) level begins to fall. The decreased pH level can also be due to the development of a metabolic acidosis as the patient becomes more hypotensive and tissue perfusion decreases.
Imaging Studies
Lateral neck radiography to evaluate for soft tissue swelling may be helpful in patients who experience throat tightness after a wasp sting, although direct fiberoptic visualization of the airway (eg, with a Machida scope) is optimal.
Perform chest radiography in patients who present with dyspnea or chest tightness or who have an anaphylactic episode after a wasp sting. Chest radiography should be obtained by using a portable machine in the emergency department (ED) with equipment for aggressively managing the airway close to the bedside.
Other Tests
Perform an ECG on patients who experience palpitations, chest tightness, dyspnea, or lightheadedness after a wasp sting.
A baseline peak flow measurement helps to assess the progression of distress in patients who present with wheezing, dyspnea, or prolongation of the expiratory phase of respiration after a wasp sting.
Procedures
Flexible fiberoptic visualization of the larynx and vocal chords may be useful to exclude laryngeal edema or spasm. This should be performed by a clinician experienced in emergency airway management; use caution to avoid precipitating laryngospasm.
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Western paper wasp (Mischocyttarus flavitarsis) building a nest. By Sanjay Acharya (self-made at Sunnyvale, California, USA). Courtesy of Wikimedia Commons.
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Yellow jacket. By Richard Bartz, Munich aka Makro Freak (Own work). Courtesy of Wikimedia Commons.
