Case Study 1: Bug Bite While Swimming

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Headshot of Dawn Elise DeWitt, MD, MSc, CMedEd, MACP, FRACP, FRCP-London · Senior Associate Dean, Collaboration for InterProfessional Health Education Research & Scholarship (CIPHERS)
Dawn Elise DeWitt
MD, MSc, CMedEd, MACP, FRACP, FRCP-London · Senior Associate Dean, Collaboration for InterProfessional Health Education Research & Scholarship (CIPHERS)
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Case study 1: Jeremy—Bug bite while swimming

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A previously healthy, athletic 40-year-old man is brought in by ambulance. He is hypotensive after collapsing. While he was swimming, he was bitten by a large fly or bee on the forehead and bled from the bite. He suddenly felt unwell and fainted. A doctor/family member saw 2–3 tonic-clonic jerks and was initially unable to get a peripheral pulse. Apical pulse 48, BP 76/50.
He was diaphoretic and unconscious for 3–4 minutes before waking up completely. No incontinence occurred. The patient had fainted once previously after having sutures for a small wound. No cardiac risk factors. PE shows a healthy-appearing man, BP 90/62, P54. The rest of the examination is entirely normal. ECG shows bradycardia but is otherwise normal.

Question

At this time, the next best step is:

This was most likely vasovagal, but the severity was concerning.

    • Previous vasovagal episode + blood on arm.
    • 2–3 tonic-clonic jerks do not indicate seizure activity.
      • Rather brain hypoxia.
    • Vasovagal and situational syncope =  23% of syncope.
    • Investigations helpful in 2–3% of cases (not helpful here).
    • “Do not miss” is CHD (he has no CRFs).
    • If exercise-induced syncope: 
      • Examine for murmurs: Hypertrophic obstructive cardiomyopathy (HOCM).
      • Systolic murmur that increases with valsalva.

 

Because of many minutes of hypotension, Jeremy was seen in the ED.

  • Troponins were mildly elevated (hypotension); other bloods normal.
  • Echo showed mild aortic valve sclerosis.
  • Exercise stress: 19 minutes, normal (fit).

Conclusion

Volume depletion.

Severe vasovagal reaction to seeing the bite bleed.

Unlikely allergic (mild anaphylaxis?)

Zebra

He was dx’d with systemic mastocytosis years later after another event.

Syncope physiology

  • Decreased blood flow to the brain that results in sudden loss of consciousness.
  • Because lying down increases blood flow, most patients regain consciousness almost immediately.
  • Distinguish from dizziness, vertigo, seizures.
  • Patients with seizures often have auras, automatisms, or tonic-clonic movements (though a few are common in syncope), incontinence, and post-ictal confusion for >5 minutes.

Question

Review the next few sections—H&P for syncope and workup. About 90 percent of patients can be diagnosed with the basic workup.


High-risk patients include those who have syncope during exertion, while lying down, with chest pain or palpitations prior to the event, family history of sudden death, known heart disease, new left bundle-branch block, QTc prolongation, or HGB 60.

Step 1: Estimate risk for CV Disease

  • CV History.
    • CRF and SX.
  • CV Exam for bruits, irregular heart rate, or murmurs.
    • Pathologic murmurs usually > 2/6 and radiate.
    • HOCM murmur increases with decreased preload (Valsalva). 
  • ECG.
  • Orthostatic hypotension: Fall in BP of >20 mm systolic (pulse rise > 30 volume depletion).
  • Carotid sinus massage (CSM).
    • Patient upright, for 5–20 seconds on each side of the neck (sequentially).
    • Systolic BP fall of 50 points or > 3 seconds of asystole is diagnostic of neurocardiogenic carotid sinus syncope (Parry).  
    • The risk of complications is low—11/16,000 maneuvers in one study (Davies)—but CSM should be avoided in patients with bruits or with a history of stroke or MI within 6 months. 

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