An 82-year-old male has been cleared for discharge to the ward after spending three weeks in your ICU for a large subdural haemorrhage. A junior nurse gave him a trial of oral feeding and then removed his right subclavian vein catheter. Subsequently, he became cyanosed and suffered a bradycardic/asystolic cardiac arrest.

Following successful resuscitation and orotracheal intubation, his observations are as follows: Heart rate: 135 beats/min (sinus)
 
Blood pressure: 120/72 mmHg on noradrenaline 20 mcg/min Oxygen saturation of 90% on FiO2 0.8

a)    List two likely differential diagnoses that best explain the events.    (20% marks)

b)    Outline your diagnostic approach to distinguish between them.    (40% marks)

c)    Briefly outline the specific management for each of your diagnoses.    (40% marks)
 

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College answer

  1. One mark each for the following diagnoses (only count first 2 listed by candidate)
    1. Air embolism
    2. Aspiration pneumonitis/pneumonia
    3. Pulmonary embolus
  2. For each diagnosis 2 marks for clear and concise diagnostic strategy:
  • 1 mark for appropriate history and examination features
  • 1 mark for specific investigations

e.g.

Air Embolism:

History of unclamped line especially in upright position, sudden onset typically. Exam may reveal ‘Mill Wheel’ murmur

Investigation: Echocardiography to reveal air in cardiac chambers

Aspiration:

History: May be witnessed, hypoxia after eating/drinking

Exam: Signs of consolidation/collapse (crackles, bronchial breathing etc.) Investigations: CXR usually sufficient, OK to mention US

PE:

History: risk factors, sudden onset, chest pain, SOB

Exam: usually nil specific, absence of alternative diagnostic signs e.g. normal auscultation Investigations: CTPA confirmatory if stable enough for transport, Echo highly suggestive in correct clinical setting and occasional visualise thrombus.

  1. Clear specific, safe, sensible management strategy = 2 marks for each condition. 1 = partial detail or lacking clinical perspective

e.g.

Air embolism:

Occlude CVC site

Head down / Trendelenberg position Catheter aspiration

O2/supportive care

Consider hyperbaric when haemodynamically stable especially if neurological symptoms and signs

Aspiration:

Intubation/airway protection

Bronchoscopy if large volume or bronchial obstruction

Antibiotics for secondary infection

PE:

Consider embolectomy or catheter directed clot retrieval if available.

Thrombolysis may be considered even in cases of massive PE even with recent surgery if death otherwise imminent, balance risk of bleeding vs. death by PE on case-by-case basis.

Anticoagulation with Heparin/Clexane depending on perceived risk of bleeding

Discussion

This is one of those things that might work better as a table:

Possibility Diagnosis Management
Air embolism

Clinical:

  • characteristic "mill-wheel" murmur 
  • Gas bubbles in the retina
  • Hypoxia with shunt
  • Tachypnoea and dyspnoea

Monitoring:

Investigations

  • Bubbles on TTE/TOE
  • Increased PA pressure
  • Bubbles on CTPA
  • Put the patient in a supine position (a head-down position is sometimes recommended)
  • Increase the FiO2 to 100%
  • Aspirate the gas using a PA catheter
  • Hyperbaric oxygen
  • Anticonvulsants
  • A heparin infusion is occasionally recommended
Massive PE

Clinical:

  • Tachycardia, tachypnoea, hypoxia
  • Normal chest auscultation
  • Massive dead space ventilation 

Monitoring:

  • ECG changes (S1 Q3 T3, right heart strain pattern)
  • Low end-todal CO2

Investigations

  • Normal CXR
  • Distended RV on TTE
  • Obviously CTPA
  • Thrombolysis
  • Heparin infusion
  • Clot retrieval or catheter-directed thrombolysis
  • Inotropes with pulmonary vasodilator properties (eg. milrinone or levosimendan
Massive aspiration

Clinical:

  • Tachycardia, tachypnoea, hypoxia
  • Creps on chest auscultation
  • Massive shunt

Monitoring:

  • Poor lung compliance (via ventilator)

Investigations

  • Abnormal CXR
  • Bronchoscopy for lavage
  • Prone position ventilation
  • Lung-protective ventilator settings
  • Inhaled pulmonary vasodilators

References

References

Muth, Claus M., and Erik S. Shank. "Gas embolism." New England Journal of Medicine 342.7 (2000): 476-482.

Palmon, Sally C., et al. "Venous air embolism: a review." Journal of clinical anesthesia 9.3 (1997): 251-257.

Oh's Intensive Care manual: Chapter 34   (pp. 392) Pulmonary  embolism by Andrew  R  Davies  and  David  V  Pilcher

Anderson, Frederick A., and Frederick A. Spencer. "Risk factors for venous thromboembolism." Circulation 107.23 suppl 1 (2003): I-9.

Konstantinides, Stavros V., et al. "2014 ESC Guidelines on the diagnosis and management of acute pulmonary embolism." European Heart Journal (2014): ehu283.