What are the recent guidelines for packed red cell (PRC) transfusion in patients on mechanical ventilation?

Guidelines for Packed Red Cell Transfusion in Mechanically Ventilated Patients

For mechanically ventilated patients, a restrictive transfusion strategy with a hemoglobin threshold of 7 g/dL should be used rather than a liberal transfusion strategy (hemoglobin threshold of 10 g/dL). 1

Transfusion Thresholds

• In adult ICU patients on mechanical ventilation, transfusion should be considered at hemoglobin concentrations of 7 g/dL or less 1
• There is no benefit to a "liberal" transfusion strategy (transfusion when Hb is ≥10 g/dL) in critically ill patients requiring mechanical ventilation 1
• In postoperative surgical patients on mechanical ventilation, transfusion should be considered at a hemoglobin concentration of 8 g/dL or less 1
• In the absence of acute hemorrhage, RBC transfusions should be given as single units with reassessment of hemoglobin levels after each unit 1

Evidence Supporting Restrictive Strategy

• A landmark prospective randomized trial comparing liberal and conservative transfusion triggers in ICU patients demonstrated that waiting for a hemoglobin level of 7.0 g/dL versus 9.0 g/dL before transfusion resulted in fewer transfusions with no adverse effects on outcome 1
• Multiple studies have identified exposure to allogeneic blood products as a risk factor for postoperative infection and postoperative pneumonia 1
• Restrictive transfusion resulted in lower mortality than liberal transfusion (RR, 0.85 [95% CI, 0.7 to 1.03]), although this finding was not statistically significant 1
• In patients with lower APACHE II scores, mortality was actually improved in the "restricted transfusion" group, possibly due to immunosuppressive effects of non-leukocyte-depleted red blood cell units 1

Risks of Transfusion in Mechanically Ventilated Patients

• Transfusion of packed red blood cells increases the risk of developing ventilator-associated pneumonia (VAP), with an odds ratio of 1.89 (95% CI, 1.33-2.68) 2
• The effect of transfusion on late-onset VAP (occurring after ≥5 days of mechanical ventilation) is even more pronounced with an odds ratio of 2.16 (95% CI, 1.27-3.66) 2
• Transfusion demonstrates a positive dose-response relationship with VAP risk 2
• RBC transfusions may increase pulmonary vascular resistance index (203 ± 58 to 238 ± 49 dyne/cm5/m2; P = 0.04), potentially hampering right ventricular ejection 3

Physiological Considerations

• Despite theoretical benefits, RBC transfusion does not consistently increase oxygen uptake at either the whole-body level or within individual organs in critically ill septic patients 3
• Oxygen utilization does not increase either by Fick equation or by indirect calorimetry following transfusion in anemic septic patients 3
• Prolonged storage of PRBCs was not associated with higher mortality in adults with ARDS but was associated with prolonged dependence on renal replacement therapy 4
• In post-cardiac surgery patients, 100% oxygen ventilation was more effective at improving tissue oxygenation than RBC transfusion 5

Implementation Considerations

• In the absence of acute hemorrhage, RBC transfusion should be given as single units with careful monitoring and repeat measurement of post-transfusion hemoglobin 1
• Avoiding unnecessary use of packed red blood cell transfusions may decrease the occurrence of VAP 2
• Consider using leukocyte-depleted red blood cell transfusions, which have been shown to reduce the incidence of postoperative infections in some patient populations 1
• Aggressive treatment of hyperglycemia should be considered alongside transfusion decisions, as it has been shown to reduce bloodstream infections and decrease frequency of mechanical ventilation 1

Special Considerations

• Patients with active bleeding, acute coronary syndrome, or severe cardiovascular disease may require individualized transfusion thresholds 1
• Symptoms of anemia (chest pain, orthostatic hypotension or tachycardia unresponsive to fluid resuscitation, or congestive heart failure) should be considered alongside hemoglobin concentration when making transfusion decisions 1
• Hyperoxia should be avoided in transfused patients, and normoxia should be targeted as soon as hemoglobin returns to acceptable levels 1