Question 9

College answer

Syllabus topic/section:

2.1.6 Gastrointestinal Intensive Care: Acute gastrointestinal bleeding: L1
2.5.1 Research and Evidence Based Practice in Intensive care: Critical appraisal of study types

Discussion: 

This was a critical appraisal question regarding blood transfusion for upper gastrointestinal haemorrhage. In- depth knowledge of the specific evidence was not required. For example, quotation of journal and publication dates are not required but a summary of the evidence available is required for a passing mark.

Candidates scored well if they noted the glossary term critically evaluate and provided an expanded explanation rather than a simple list in part a).

The question was specifically about transfusion thresholds rather than transfusion. Many candidates could have improved their answer as they simply listed generic risks of transfusion thresholds without explanation or adaptation to the specific population asked for.

The principles behind landmark transfusion papers such as TRICC and TRISS remain core topics even if the nuances of specific studies relevant to upper GI haemorrhage are less well known. Good answers provided a broad overarching description of the current evidence for transfusion thresholds across the whole critical care population and then demonstrated the ability to adapt these principles to the specified sub-population.

The marking rubric is included to aid the candidate’s future study.
 

Discussion

Though the stem does not specify whether it is referring to the upper or the lower GIT, the examiner comments suggest that UGI bleeding was the main focus; but as they themselves pointed out, "nuances of specific studies relevant to upper GI haemorrhage are less well known".

Strategy to transfuse a severe ongoing GI bleed

• Decision to transfuse PRBCs is made on the basis of clinical criteria.
• Haemodynamically unstable, prior to definitive management
  • Aim for SBP ~85-90 mmHg
  • Use blood products exclusively for volume resuscitation in a balanced proportion to prevent coagulopathy
  • Therapy should be guided by organ perfusion, response to intervention and risk of ongoing bleeding, rather than Hb thresholds
• Haemodynamically stable, pre or post definitive management
  • Aim for Hb > 70g/L, same as with other ICU patients
  • Hb 80-90 for patients with acute ischaemic heart disease

Advantages of transfusion thresholds

• Distributive justice: use a low threshold to carefully manage a scarce resource
• Reduce the wasteful variation in practice by introducing standards
• Reduce the population exposure to each other's antigens, thereby reducing the morbidity from transfusion reactions
• Agreement between expert bodies to establish a threshold supports individual practitioners in their decisionmaking
• There is sufficient data from unselected ICU patients, suggesting that the whole cohort, on average, can safely be treated in a similar way

Disadvantages:

• Individual demands may differ; some patients may benefit from different targets; thresholds may not be generalisable to all critical care patient populations (eg. we already know about MI and TBI)
• Standards introduce complacency with decisionmaking and thresholds may be applied thoughtlessly to situations where individualised care would have been more appropriate
• Guidelines to direct thresholds may not be generaliseable to environments which they were not created in (eg. developing world)
• Thresholds may make transfusions seem mandatory for patients who would have otherwise been spared (eg. asymptomatic anaemia)
• The use of threshold adherence becomes a surrogate marker of the quality of care, which is dangerous

Evidence for red blood cell transfusion thresholds in this population.

• Decisionmaking is supported by limited data from 
  • Clinical trials or relatively stable UGI bleed patients
  • Generialised ICU population data (TRICC, TRISS)
• TRICC and TRISS did not enrol acutely bleeding patients
• Two trials, Villanueva et al (2013) and TRIGGER by Jairath et al (2015),:
  • Compared targets of  70 vs 90 and 80 vs 100g Hb
  • Excluded shocked and exsanguinating patients
  • For Villanueva et al (2013), 50% of the restrictive group did not require transfusion
• In summary, these findings are difficult to extrapolate

My practice statement

• Apply the 70g/L Hb threshold to stable patients in the same way as to the rest of the ICU population
• Apply adjusted threshold to patients with MI, TBI, or those at higher risk of bleeding due to coagulopathy or anticoagulation
• Use other (clinical) criteria to decide re. transfusion for unstable patients and those without definitive control of their bleeding