Question 26

College Answer

Syllabus topic/section:

2.1.18    Peri-operative Issues in Intensive Care – L1.

Aim:
To assess the candidate’s understanding of the main issues that affect ICU care post pneumonectomy. In detail, an understanding of pathophysiological considerations affecting immediate post op ICU care, the potential early complications to look for and detailed understanding of intricacies of fluid therapy was tested.

Discussion:
Candidates are rewarded for following the glossary, being precise with listing the specific and early complications, correct handling of fluid therapy, and demonstrating an understanding of specific pathophysiological perturbations, as opposed to generic statements.
Candidates who received less marks demonstrated a poor understanding of the cardiovascular physiological changes following pneumonectomy. Those that understood the changes were able to score well for this question. Many simply stated the obvious respiratory changes of reduced FVC and tidal volume. This would be implied in the surgery itself and didn't demonstrate that candidates understand the changes that occur when a lung is removed. Examples of such changes include chylothorax, phrenic nerve/ recurrent laryngeal nerve damage, Atrial arrythmias (80% within 72 hours) and RV failure among others.

Many candidates listed general complications common to many different surgeries like infection or atelectasis (these did not score marks) rather than the specific complications of a pneumonectomy. Majority of candidates were able to provide and justify a sensible fluid management strategy.

Discussion

The middle "list" question was weighted six marks, which should alert the candidates to the importance of making a good list of only pneumonectomy-relevant complications, rather than

squandering their six points on listing generic surgical badness. 

a) Cardiorespiratory physiological effects of pneumonectomy, which, to be fair, might also sound as if they are "complications" of pneumonectomy, insofar as these are undesirable consequences of the procedure, except if one looks closely the surgical literature defines "complications" as "any deviation from the normal postoperative course". At the same time the college seemed to have wanted us to list only those physiological changes which were not barn-door-obvious, such as the decrease in FVC would be, for example. What these might have consisted of, one can not be sure, but the following list was constructed from Batirel (2021):

• Respiratory
  • Decreased carbon monoxide diffusion capacity (DLCO) by about 30%
  • Decreased maximal oxygen uptake (VO₂max) by about 30%
  • Hyperinflation of the remaining lung
• Cardiac
  • Increased RV afterload due to increased pulmonary vascular resistance
  • Increased pulmonary artery pressure
  • Change of the cardiac position within the chest cavity, with rotation and displacement of the heart, which results in the impairment of venous return

b) Complications of pneumonectomy:

• Atrial fibrillation: occurs in 10-20%
• Cardiac ischaemia: seems to occur in 1.2-3.8%
• Right ventricular failure: this is caused by the increased afterload.
• Post-pneumonectomy pulmonary oedema: incidence is about 2.5-4%. 
• Right to left shunt though a PFO
• Cardiac herneation
• Compression of the intact main bronchus due to a shift of the medistainal structures
• Hilar torsion and gangrene
• Chylothorax: the risk is between 0.7 and 2%.
• Stump breakdown and bronchopleural fistula
• Phrenic nerve damage
• Recurrent layngeal nerve damage
• Post-operative pneumonia or empyema: This seems to happen in up to 25% of patients. The major culprit is post-operative atelectasis.

c) Post operative fluid management, for two marks, would not have been an extensive outline:

• Keep the patient in a neutral or negative balance, because:
  • The right heart has suddenly increased afterload by 50-60%
  • The pulmonary veins have suddenly increased pressure by 50-60%
  • Increased pressure can cause capillary damage, increasing their leakiness
  • The overall upshot of all these is a propensity to pulmonary oedema