New CHEST Guidelines – Transfusing RBCs in Critical Illness 

Written by Samuel Rouleau

Spoon Feed
Most of the time, targeting a hemoglobin threshold of 7 – 8 g/dL in critically-ill patients is recommended, with acute coronary syndrome as the exception to the rule. Strap in for this longer-than-normal Spoon Feed summary of these guidelines.

More blood doesn’t always mean more better
This consensus statement from CHEST included 23 studies that addressed contemporary questions on red blood cell (RBC) transfusions for adults with critical illness. The guidelines compared a restrictive threshold, defined as a hemoglobin threshold of 7 – 8 g/dL, to a permissive threshold, defined as hemoglobin level 8.5 – 10 g/dL for the scenarios below.

For all adults with critical illness, CHEST strongly recommends a restrictive RBC transfusion strategy instead of permissive. There is good-quality evidence that demonstrates no difference in mortality between restrictive and permissive transfusion approaches, and with less adverse events in those randomized to restrictive transfusion.

In critically ill patients with GI bleeding, CHEST strongly recommends a restrictive approach to transfusion. One key trial of 921 patients with acute upper GI bleeding and access to early endoscopy found improved 6-week mortality, lower rates of re-bleeding, and fewer adverse events in the restrictive group.

The CHEST guidelines offer a conditional recommendation against restrictive transfusion strategy for those with acute coronary syndrome (what awkward wording…). The idea is to balance oxygen delivery while avoiding too much blood that could cause increased viscosity. In the CHEST pooled analysis, there was a trend toward higher mortality with a restrictive approach, but it was not statistically significant. The MINT trial, the largest RCT to date, found lower rates of cardiac death in permissive blood transfusion (transfusing for a hemoglobin below 10) strategies when compared to restrictive, though there was no difference in 30-day mortality or rate of myocardial infarction. The target hemoglobin for these patients is not well understood. Importantly, an isolated elevation in troponin level without other evidence or cardiac ischemia is not a reason to pursue a permissive transfusion strategy.  On the other hand, for post-operative cardiac surgery patients who underwent coronary artery bypass graft or valvular surgery, the CHEST pooled analysis favors a restrictive approach, which aligns with Society of Thoracic Surgeons’ guidelines.

And last, but not least, sepsis! CHEST conditionally recommends against using a permissive transfusion strategy. The largest study, TRISS, found no difference in 30-day mortality, ICU and hospital length-of-stay between permissive and restrictive thresholds. There was a non-statistically significant benefit in a subgroup of cancer patients in this trial. 

How will this change my practice?
I have been trained to use a restrictive approach to transfusion of blood products in critically ill patients, and these consensus guidelines reinforce this practice. However, I will use a permissive transfusion approach in patients with acute coronary syndrome.

Source 
Red Blood Cell Transfusion in Critically Ill Adults: An American College of Chest Physicians Clinical Practice Guideline. Chest. 2024 Sep 26:S0012-3692(24)05272-3. doi: 10.1016/j.chest.2024.09.016. Epub ahead of print. PMID: 39341492