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OSCE 462: Acute Hypoxia

OSCE Format:

  • Please answer the following questions on the given topic
  • The case will be displayed with each question followed by an answer, allowing you to review your given response
  • Please score yourself according to the orange text
  • A timer is available for use to determine the given time period

Introduction

You are asked to review a 45 year old man on the intensive care unit. He was admitted 8 days ago following a road traffic accident in which he sustained significant multisystem injuries. The nurse reports he has recently been for a scan, but has been getting more hypoxic since he returned. He is intubated and ventilated, and is now saturating at 88% on an FiO2 of 1.0…

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Question No. 2

Q: What type of scan is this image taken from? (1 marks)

Answer No. 2

This image is taken from a CT pulmonary angiogram (CTPA) 1

1

Question No. 3

Q: What abnormality is shown (1) and what is the diagnosis (1)? (2 marks)

Answer No. 3

  • Demonstrates contrast filling defect across the bifurcation of the main pulmonary artery 1 extending to the right and left main pulmonary arteries
  • In keeping with a diagnosis of saddle 0.5 pulmonary embolism 0.5

2

Question No. 4

Q: Name 3 advantages and 2 disadvantage for CTPA in the diagnosis of PE? (5 marks)

Answer No. 4

Score
Advantages
Disadvantages
CTPA
  • Readily available around the clock in most centres1
  • Excellent accuracy1
  • Strong validation in prospective management outcome studies1
  • Low rate of inconclusive results (3–5%)1
  • May provide alternative diagnosis if PE excluded1
  • Short acquisition time1
  • Can evaluate IVC and lower extremity thrombi when used in conjunction with venography1
  • Radiation exposure, particularly to young female breast tissue 1
  • Exposure to iodine contrast 1
  • Tendency to overuse because of easy accessibility 1
  • Clinical relevance of CTPA diagnosis of subsegmental PE unknown 1

5

Question No. 5

Q: How would you define high-risk PE? (1 marks)

Answer No. 5

High-risk PE is defined as a PE in the presence of haemodynamic instability 1
Early Mortality Risk
Early Mortality Risk
Risk Parameters & Scores
Risk Parameters & Scores
Risk Parameters & Scores
Risk Parameters & Scores
Early Mortality Risk
Early Mortality Risk
Haemodynamic Instability
PESI class III-V
Signs or RV Dysfunction on Imaging
Cardiac Laboratory Biomarkers
High
High
+
(+)
+
(+)
Intermediate
High
-
+
Both positive
Both positive
Intermediate
Low
-
+
Either one (or none) positive
Either one (or none) positive
Low
Low
-
-
-
Assessment optional but negative if assessed
ESC Guidelines

G

1

Question No. 6

Q: Describe 2 criteria that would constitute haemodynamic instability in a high-risk pulmonary embolism suggesting thrombolysis would be indicated? (2 marks)

Answer No. 6

Cardiac arrest
  • Need for cardiopulmonary resuscitation 1
Obstructive shock
  • Systolic BP <90 mmHg or vasopressors required to achieve a BP ≥90 mmHg despite adequate filling status 1
    and
  • End-organ hypoperfusion (altered mental status; cold, clammy skin; oliguria/anuria; increased serum lactate)
Persistent hypotension
  • Systolic BP <90 mmHg1 or systolic BP drop ≥40 mmHg 1lasting longer than 15 min and not caused by new-onset arrhythmia, hypovolaemia, or sepsis
ESC Guidelines

G

2

Case Information

Upon reviewing the patient you note that the patient has a blood pressure consistently below 80mmHg systolic. You decide to thrombolyse and proceed to administer alteplase. The nurse asks you about other management of the patient…

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Question No. 8

Q: Describe the possible therapies that can be used to support the right ventricle? (5 marks)

Answer No. 8

Fluid Therapy
  • Cautious fluid therapy 1 may improve haemodynamic status:
    • Small fluid boluses (500ml) have been shown to improve cardiac output
  • Aggressive volume expansion should be avoided: 1
    • Potential to over distend the RV and lead to reduced systemic cardiac output
    • Not shown to be of benefit in studies and may be harmful
    • If signs of elevated CVP, further volume loading should be withheld
Vasopressors & Inotropes
  • Noradrenaline considered as first line therapy: 1
    • Increases RV inotropy and systemic blood pressure
    • Restores coronary perfusion gradient and improves ventricular interactions
  • Dobutamine may be considered useful for patients with PE, a low cardiac index and normal: 1
    • Potential to aggravate ventilation/perfusion mismatch
    • Can worsen circulatory failure given vasodilatory effect
Pulmonary Vasodilators
  • Pulmonary vasodilators may be useful in in patients with PE and pulmonary hypertension 1 , though anecdotal evidence only
  • Options include inhaled nitric oxide and aerosolised prostacyclin
Mechanical Circulatory Support
  • Mechanical support may be useful in the setting of circulatory collapse or cardiac arrest: 1
    • VA-ECMO most frequently used:
    • Associated with a high incidence of complications, even when used for short periods
    • Effectiveness depends upon centre experience and patient selection

5

Question No. 9

Q: Give 2 options for interventional based treatment? (2 marks)

Answer No. 9

  • Percutaneous catheter-directed Thrombolysis 1
  • Percutaneous catheter-directed embolectomy 1
  • Surgical embolectomy 1

2

Question No. 10

Q: Describe two situations where catheter or surgical interventions should be considered? (2 marks)

Answer No. 10

  • Should be considered:
    • Where there are absolute contraindications to thrombolysis 1
    • Where thrombolytic therapy has failed and the patient is critically ill 1

2

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