Transfusion in ACS management

# PRBC transfusion in actual clinical practice:
- Transfusion of PRBC is the most commonly performed procedure in the Cardiovascular Health Study Cohort by 1997 Part A Medicare Claims with 3.3% of the cohort receiving it.
- 2004 CRUSADE quality improvement initiative in-hospital outcomes revealed an overall non-CABG transfusion rate of 9.9% among patients with NSTEMI and unstable angina.
- Yang et al. (JACC, 2005;46:1490-1495) found significant increase in rate of transfusion among older ACS patients. Among non-CABG patients, the transfusion rate was 4.5% for those less than 65 years of age compared to 14.1% for those older than 75. Within the overall population, the transfusion rate was 9.7% and 18.5% respectively.
- CRUSADE predictors of transfusion (JACC, 2005;46:1490-1495) were renal insufficiency, drop in systolic blood pressure, female sex, history of diabetes mellitus, increasing age, and congestive heart failure on presentation.

# PRBC transfusion and ACS outcome:
- Transfusion requirement in critical care investigators: 838 critically ill ICU patients who had hemoglobin concentrations of 9 g/dl were enrolled. 418 were randomized to a restrictive strategy of transfusion when hemoglobin concentration falls below 7.0 g/dl and were maintained at 7.0  9.0 g/dl. 420 patients were randomized to a liberal strategy of transfusion when   hemoglobin concentration falls below 10.0 g/dl and it was maintained at 10.0  12.0 g/dl. The primary end point of 30 day mortality was similar in the two groups (18% vs 23%, p=0.11). The mortality rate during hospitalization was significantly lower in the restrictive strategy group (22.2% vs 28.1%, p=0.05).
- Cooperative cardiovascular project: 78974 patients that were 65 years of age or older who were admitted for acute myocardial infarction were grouped into categories of admission hematocrit value. Patients who had bleeding or underwent CABG were excluded. Aim of the study was to evaluate any association between PRBC transfusion and the primary end point which was 30 day mortality. After accounting for survival bias, blood transfusion was associated with a lower short term mortality rate if the hematocrit was 30% or lower on admission. There was no benefit for transfusion when hematocrit was 30.1% or above.
- S Rao et al analyzed 24112 participants in 3 large international trials of ACS management (the GUSTO IIb, PURSUIT, and PARAGON B trials). The patients were grouped according to whether they received a blood transfusion during the hospitalization. The association between transfusion and outcome was assessed using Cox proportional hazards modeling. The thirty day mortality rate which was the main outcome measure along with myocardial infarction and death/mi rate were significantly higher as among those underwent transfusion (8% vs 3.08%, P<0.001; 25.16% vs 8.16%, p<0.001; 29/24% vs 10.02%, p<0.001 respectively). Using the landmark analysis, transfusion was noted to be associated with a trend toward increased mmortality. The predicted probability of 30 day death was higher with transfusion at nadir hematocrit values above 25%.

# Possible explanations:
- Depletion of nitric oxide in PRBC leads to vasoconstriction, platelet aggregation and therefore inefficient oxygen delivery.
- Transfusion is associated with increase in generalized inflammation as evident by a rise of CRP and IL6.

# Recommendation:
In patients with ACS, both bleeding and PRBC transfusion are associated with worsening outcomes. Therefore where possible appropriate dosing of anti-platelet and anticoagulation therapy should be adopted to lower adverse bleeding events. Transfusion should be used conservatively instead of liberally in ACS management. In the absence of demand ischemia, PRBC transfusion should only be given when hct drops below 25.g/dl.