Rosen & Barkin's 5-Minute Emergency Medicine Consult (70 page)

Elicit time of symptom onset in relation to dive surfacing (almost all symptoms occur within the 1st 10 min).

Careful neurologic exam owing to the wide variety of neurologic manifestations

• Clinical diagnosis: Recognize risk factors and various clinical presentations.
  
• Inquire as to unusual circumstances during ascent:
  
  • Breath holding
    
  • Panic/out-of-air situation
    
• Thorough neurologic exam must carefully document the extent of the deficits to the motor, sensory, cerebellar, and cranial nerves.
  

• Serum creatinine kinase activity:
  
  • Marker of the severity of cerebral AGE
    
• CBC
  
• Electrolytes, BUN, creatinine, glucose
  
• ABG when respiratory symptoms are present
  

• CXR:
  
  • For evidence of pneumothorax or mediastinal emphysema (both rare)
    
• Chest CT
  
  • For evidence of local lung injury or hemorrhage
    
• Ventilation Perfusion Scan
  
  • For evidence consistent with pulmonary emboli
    
• EKG
  
• Echo:
  
  • Looking for evidence of patent foramen ovale
    
• CT head:
  
  • For altered mental status
    
  • Do not delay recompression for CT when AGE almost certain clinically.
    

• Cerebrovascular accident (CVA) from causes unrelated to gas embolism
  
• Neurologic deficits owing to decompression sickness
  

TREATMENT

• Cautions:
  
  • Patients who experience sudden neurologic recovery can relapse quickly as bubble positions change.
    
  • Recognize AGE as a potential diagnosis.
    
• Altered mental status within 10 min of surfacing from compressed air dive
  
• Sudden neurologic decompensation following placement of central line
  
• Controversies:
  
  • Trendelenburg positioning patients with suspected AGE is not effective:
    
    • Hypothesized that elevation of legs could cause air bubbles to migrate away from cerebral circulation and that increased hydrostatic pressure in brain will shrink bubbles
      
    • Trendelenburg positioning may in fact increase injury by increasing intracerebral pressure.
      

ABCs:

• 100% oxygen by tight-fitting mask
  
• Intubation for ventilation/protection of airway required
  
• IV access with volume augmentation
  

• Hyperbaric oxygen recompression therapy (see “Hyperbaric Oxygen Therapy”):
  
  • For all AGE
    
  • Arrange transportation to nearest hyperbaric facility.
    
  • Aircraft capable of cabin pressurization below 1,000 feet barometric pressure best suited for transfers
    
  • Prophylactic chest tube for simple pneumothorax to prevent conversion to tension pneumothorax during recompression
    
  • Fill endotracheal and Foley catheter balloons with water or saline to avoid shrinkage/damage during recompression.
    
• Divers alert network (DAN):
  
  • Based at Duke University Medical Center
    
  • Provides 24 hr emergency hotline for medical consultation on treatment of dive-related injuries and for referrals to hyperbaric chambers (telephone: [919] 684-8111)
    

FOLLOW-UP

Admit all following initial hyperbaric therapy for observation and re-exam.

No AGE patients should be discharged from the ED.

Hyperbaric oxygen referral for patients with arterial gas embolisms

• Symptoms occur during ascent or within 10 min of reaching the surface.
  
• Patients who experience sudden neurologic recovery can relapse quickly as bubble positions change.
  
• Fill endotracheal and Foley catheter balloons with water or saline to avoid shrinkage/damage during recompression.
  

• Hawes J, Massey EW. Neurologic injuries from scuba diving.
  Neurol Clin.
  2008;26:297–308.
  
• Levett DZ, Millar IL. Bubble trouble: A review of diving physiology and disease.
  Postgrad Med J
  . 2008;84:571–578.
  
• Lynch JH, Bove AA. Diving medicine: A review of current evidence.
  J Am Board Fam Med
  . 2009;22:399–407.
  
• Tourigny PD, Hall C. Diagnosis and management of environmental thoracic emergencies.
  Emerg Med Clin North Am.
  2012;30:501–528.
  
• Van Hoesen KB, Bird NH. Diving medicine. In: Auerbach PS, ed.
  Wilderness Medicine
  . 6th ed. St. Louis, MO: CV Mosby; 2011.
  

See Also (Topic, Algorithm, Electronic Media Element)

• Barotrauma
  
• Decompression Sickness
  
• Hyperbaric Oxygen Therapy
  

CODES

958.0 Air embolism

BASICS

Immediate and severe compromise of the blood supply to a limb, threatening its viability, secondary to the sudden blockage of a peripheral artery

• Arterial embolization
  
  • Thrombus or plaque
    
  • Originates from aneurysms or atherosclerotic lesions
    
  • Emboli typically lodge where there is an acute narrowing of the artery
    
  • 75% of emboli involve an axial limb vasculature
    
    • Femoral 28%
      
    • Arm 20%
      
    • Aortoiliac 18%
      
    • Popliteal 17%
      
    • Visceral and other 9%
      
• Thrombosis
  
• Arterial dissection
  
• Trauma
  
  • Crush injuries
    
  • Compression
    
  • Arterial contusion and thrombosis
    
  • Arterial transection
    
• Limb ischemia >6 hr usually results in functional impairment or limb loss.
  
  • If acute on chronic, collateral circulation may preserve tissue beyond 6 hr.
    

• Embolus:
  
  • Atrial fibrillation
    
  • Myocardial infarction
    
  • Valvular disease
    
  • Endocarditis
    
  • Atrial myxoma
    
  • Aneurysm
    
  • Atherosclerotic plaques
    
  • Paradoxical embolus
    
    • Patent foramen ovale
      
• Thrombosis
  
  • Vascular grafts
    
  • Atherosclerosis
    
  • Thrombosis of an aneurysm
    
  • Entrapment syndrome
    
  • Blood clotting disorders
    
  • Low flow state
    
  • Heparin-induced thrombosis
    
• Arterial dissection
  
• Arterial injury:
  
  • Intimal flap
    
  • Dissection
    
  • Pseudoaneurysms
    
  • Iatrogenic
    
    • Catheterization
      
    • Arteriography
      
    • Balloon angioplasty
      
    • Complication of arterial puncture
      
  • Penetrating trauma
    
    • Gunshot, stab wounds, shotgun, shrapnel
      
    • IV drug use
      
  • Blunt trauma
    
    • Joint displacement
      
    • Fracture
      
    • Compartment syndrome
      

DIAGNOSIS