In a patient who recently scuba dived and was diagnosed with left otitis media treated with antibiotics, now presenting two days later with fatigue and left arm tingling, what laboratory tests should be ordered to rule out dive‑related causes?

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Immediate Laboratory Testing for Suspected Decompression Sickness

This patient requires urgent evaluation for decompression sickness (DCS), not just routine blood work—order an arterial blood gas (ABG), complete blood count (CBC), comprehensive metabolic panel (CMP), creatine kinase (CK), and coagulation studies (PT/INR, PTT) immediately, while arranging emergent hyperbaric oxygen consultation.

The constellation of recent scuba diving, new-onset neurological symptoms (left arm tingling), and systemic symptoms (fatigue) two days after an initial ED visit raises serious concern for Type II decompression sickness affecting the central nervous system, regardless of the concurrent otitis media diagnosis.

Critical Distinction: Two Separate Processes

While the provided guidelines extensively discuss otitis media management 1, 2, they do not address dive-related complications. The otitis media may be:

  • A barotrauma-related middle ear injury from diving (pressure equalization failure)
  • An incidental infection unrelated to diving
  • A confounding diagnosis that delayed recognition of DCS

The neurological symptoms appearing 2 days post-dive are the red flag that cannot be attributed to simple otitis media.

Essential Laboratory Tests for DCS Evaluation

Immediate Priority Tests:

Arterial Blood Gas (ABG)

  • Assesses oxygenation and acid-base status
  • May reveal hypoxemia or metabolic acidosis in severe DCS
  • Baseline before hyperbaric oxygen therapy

Complete Blood Count (CBC) with Differential

  • Hemoconcentration suggests intravascular volume depletion from bubble formation
  • Elevated white count may indicate inflammatory response to gas emboli
  • Platelet count to assess for consumptive coagulopathy

Comprehensive Metabolic Panel (CMP)

  • Renal function (BUN/creatinine) to assess for dehydration or rhabdomyolysis
  • Electrolyte abnormalities from fluid shifts
  • Glucose to rule out hypoglycemia as alternative cause of symptoms

Creatine Kinase (CK)

  • Elevated in musculoskeletal DCS
  • Marker for rhabdomyolysis risk

Coagulation Studies (PT/INR, PTT)

  • DCS can trigger disseminated intravascular coagulation (DIC)
  • Baseline before potential anticoagulation considerations

Additional Recommended Tests:

D-dimer

  • Elevated in thrombotic processes
  • May be elevated with intravascular bubble formation

Lactate

  • Tissue hypoperfusion marker
  • Elevated in severe DCS with circulatory compromise

Troponin (if chest symptoms present)

  • Cardiac DCS is rare but life-threatening

Critical Clinical Actions Beyond Laboratory Testing

Immediate Management Steps:

  1. Contact Divers Alert Network (DAN) Emergency Hotline (+1-919-684-9111) for consultation
  2. Arrange emergent hyperbaric oxygen therapy evaluation - this is definitive treatment, not laboratory results
  3. Administer 100% oxygen via non-rebreather mask immediately
  4. Establish IV access and begin fluid resuscitation with normal saline
  5. Position patient supine (not Trendelenburg, which is outdated)
  6. Obtain detailed dive profile: depth, duration, ascent rate, number of dives, surface intervals

Neurological Assessment Specifics:

Document precisely:

  • Dermatomal distribution of tingling (suggests spinal cord DCS)
  • Motor weakness presence/absence
  • Sensory level if present
  • Bladder/bowel function
  • Cranial nerve examination
  • Cerebellar signs (ataxia, dysmetria)

Common Pitfalls to Avoid

Do not dismiss neurological symptoms as "anxiety" or attribute them solely to the otitis media. The temporal relationship to diving and specific symptom pattern (unilateral paresthesias, fatigue) are classic for DCS.

Do not delay hyperbaric consultation waiting for laboratory results. DCS is a clinical diagnosis; labs support management but should not delay definitive treatment. Time to recompression therapy directly correlates with outcome.

Do not assume antibiotics for otitis media will address dive-related pathology. These are separate issues requiring parallel management.

Do not order only routine infection workup. The dive history fundamentally changes the differential diagnosis and required evaluation.

Imaging Considerations

While not "blood tests," brain and spinal cord MRI may be indicated if hyperbaric facilities are not immediately available or if symptoms progress, to evaluate for:

  • Cerebral arterial gas embolism
  • Spinal cord infarction from venous gas emboli
  • Alternative neurological pathology

However, imaging should not delay hyperbaric oxygen therapy if DCS is clinically suspected.

Time-Critical Nature

Neurological DCS outcomes worsen significantly with treatment delays beyond 6-12 hours. The patient is already 2 days post-dive with worsening symptoms—this represents a medical emergency requiring immediate action beyond standard laboratory evaluation.

The otitis media diagnosis, while requiring continued antibiotic treatment 2, should not distract from the potentially life-altering or fatal consequences of untreated decompression sickness.

References

1
Guideline

acr appropriateness criteria® inflammatory ear disease.

Journal of the American College of Radiology, 2025

2
Guideline

otitis media.

Nature Reviews Disease Primers, 2016

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