Chest Pain, Anticoagulated Falls, and Bug Bites

General Emergency Medicine
Written By Dillon Warr

Hello Team,

Eclectic mix of topics from a string of overnights.

Diagnostic Prevalence in Chest Pain

Just published a few days ago in AJEM. This is a retrospective study of nearly 1 million ED chest pain visits across 141 U.S. emergency departments (2021–2024). It examined the prevalence of seven life-threatening chest pain diagnoses.

Here are the key takeaways:

Prevalence by Diagnosis (in order of frequency):

  • Acute Coronary Syndrome (ACS): 4.5% (1 in 22)

  • Pulmonary Embolism (PE): 0.78% (1 in 130)

  • Pneumothorax: 0.13% (1 in 750)

  • Thoracic Aortic Dissection (TAD): 0.09% (1 in 1,000)

  • Esophageal Rupture: 0.007% (1 in 14,000)

  • Pericardial Tamponade: 0.005% (1 in 20,000)

  • Ruptured Aortic Aneurysm: 0.002% (1 in 50,000)

Who Is at Higher Risk? Life-threatening diagnoses were more common in patients who were:

  • Older (prevalence ~10% in age 65+, vs. ~1% in age 18–34)

  • Male (7.5% vs. 3.8% in females)

  • Higher acuity at triage (ESI 1 patients: 55% had a life-threatening diagnosis)

  • Arriving by ambulance (9.3% vs. 4.5%)

  • Covered by commercial insurance (after adjustment)

Facility Factors Mattered Less: ED volume, urban/rural setting, and training site status were not significantly associated with diagnostic outcomes after adjustment. Western U.S. EDs had higher prevalence, likely reflecting healthcare access patterns rather than true geographic risk differences.

Critical Reminder — Chest Pain Is Not Required: More patients with these life-threatening diagnoses presented WITHOUT chest pain than with it. Only 35.8% of all patients with these seven diagnoses had chest pain as a complaint. Maintain a high index of suspicion regardless of chief complaint.

Clinical Application: These prevalence figures can serve as a priori pre-test probabilities when evaluating undifferentiated chest pain in the ED, helping to calibrate risk stratification and guide appropriate use of diagnostic testing.

The Big Picture: About 1 in 18 ED patients with atraumatic chest pain (5.5%) are diagnosed with a life-threatening condition — but the vast majority (~95%) are not.

Question: Do we need to CT the head of every patient on a DOAC who falls, even without any reported or clinical evidence of head trauma?

  • The Canadian CT Head Rule, New Orleans Criteria, and NEXUS all either exclude anticoagulated patients or automatically flag them as high-risk. None can be used to safely withhold imaging in this population.

  • The existing literature on ICH rates in anticoagulated patients with mild TBI (approximately 7-8% for DOAC users in one study) is based on patients with at least suspected head injury — not falls without any evidence of head involvement in alert and oriented patients.

  • Data does suggest elderly patients are unreliable historians for head strike. Ground-level falls in the elderly frequently involve unwitnessed or poorly recalled events. An estimated ~3% of geriatric trauma patients have intracranial injury without clinical signs, LOC, focal neurology, or GCS change. 

  • The decision to scan is driven by extrapolation and risk aversion, not by data showing that a truly head-strike-negative, neurologically intact anticoagulated patient has a meaningful ICH rate.

  • This is a genuine evidence gap. For further reading, see the 2023 ACEP Clinical Policy on Mild TBI and a 2024 systematic review and meta-analysis in the Journal of Neurology.

Question: Bee sting/bug bite or cellulitis?

Large Local Reactions (LLRs)

  • Large local reactions occur in ~19% of Hymenoptera stings and are IgE-mediated.

  • Swelling typically peaks at 24–48 hours, can exceed 10 cm with erythema and induration involving contiguous parts of the extremity, and may persist up to a week.

  • Even lymphangitic streaks can result from mast cell mediator release alone and do not indicate infection.

  • LLRs tend to be pruritic more than painful, and the patient is afebrile and non-toxic.

Skeeter syndrome

  • The mosquito equivalent — a large local allergic reaction to mosquito salivary proteins, driven by IgE and non-IgE mechanisms.

  • It can produce dramatic swelling, erythema, and warmth that closely mimics cellulitis, particularly in children and sensitized individuals.

  • Reactions range from large wheals and papules to extensive edema.

  • Skeeter syndrome mimics cellulitis, but the difference is in the duration of symptoms: Skeeter syndrome occurs within hours of a mosquito bite and cellulitis has a more protracted time course.

Management of LLR / Skeeter syndrome:

  • Ice/cool compresses, oral antihistamines, and analgesics

  • For extensive swelling: prednisone 40–60 mg/day × 3–5 days

  • Antibiotics are not indicated unless there is clear evidence of secondary infection (fever, chills, sweats)

When to suspect cellulitis:

  • Swelling that continues to progress beyond 48 hours (rather than plateauing), fever/systemic signs of infection, purulence, or pain significantly predominating over itch.

Feel free to read more about this:

Dillon Warr
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Enough is Enough. Routine Coags in the ED.