What is the threshold for blood transfusion in septic shock?

From the Guidelines

The recommended hemoglobin threshold for blood transfusion in septic shock is 7 g/dL for most patients. This means that transfusion of packed red blood cells should be initiated when the hemoglobin level falls below 7 g/dL in hemodynamically stable septic shock patients. For patients with specific comorbidities such as acute coronary syndrome, severe hypoxemia, or acute hemorrhage, a higher threshold of 9-10 g/dL may be appropriate. When transfusing, administer one unit of packed red blood cells at a time (approximately 300 mL), then reassess hemoglobin levels before giving additional units. This restrictive transfusion strategy is preferred because liberal transfusion strategies have not been shown to improve mortality and may increase risks such as transfusion reactions, volume overload, and immunomodulation, as supported by the most recent study 1.

The rationale behind the 7 g/dL threshold is that the body can compensate for anemia through increased cardiac output and oxygen extraction, while avoiding the potential harms associated with unnecessary transfusions. During active resuscitation, frequent monitoring of hemoglobin levels (every 6-12 hours) is recommended to guide transfusion decisions. It is also important to consider the patient's tolerance of anemia, particularly in patients with cardiovascular disease, as noted in the study 1.

Some studies have suggested that a higher threshold may be necessary for patients with certain comorbidities, but the majority of the evidence supports a restrictive transfusion strategy. The study 1 found that a restrictive RBC transfusion strategy was recommended over a permissive RBC transfusion strategy, with a hemoglobin threshold of 7-8 g/dL.

Key points to consider when making transfusion decisions in septic shock patients include:

• The patient's hemodynamic status and tolerance of anemia
• The presence of comorbidities such as acute coronary syndrome, severe hypoxemia, or acute hemorrhage
• The potential risks and benefits of transfusion, including transfusion reactions, volume overload, and immunomodulation
• The need for frequent monitoring of hemoglobin levels to guide transfusion decisions, as recommended by the study 1.

Overall, the evidence supports a restrictive transfusion strategy in septic shock patients, with a hemoglobin threshold of 7 g/dL for most patients.

From the Research

Threshold for Blood Transfusion in Septic Shock

• The optimal threshold for blood transfusion in septic shock patients is a topic of ongoing debate, with different studies suggesting varying hemoglobin levels as the threshold for transfusion 2, 3, 4.
• A multicenter trial published in The New England Journal of Medicine in 2014 found that among patients with septic shock, mortality at 90 days and rates of ischemic events and use of life support were similar among those assigned to blood transfusion at a higher hemoglobin threshold (9 g/dL) and those assigned to blood transfusion at a lower threshold (7 g/dL), with the latter group receiving fewer transfusions 2.
• Another study published in Revista Brasileira de terapia intensiva in 2015 evaluated the immediate effects of red blood cell transfusion on central venous oxygen saturation and lactate levels in septic shock patients with different transfusion triggers, and found that red blood cell transfusion increased central venous oxygen saturation and decreased lactate levels in patients with hypoperfusion regardless of their baseline hemoglobin levels 3.
• An observational prospective study published in BMC infectious diseases in 2016 found that anemia is very common in sepsis, and while hemoglobin level on admission exhibits independent correlation with survival, blood transfusion does not appear to be an independent predicting factor for mortality 4.
• A review article published in Journal of critical care in 2020 discussed the initial resuscitation of septic shock, including the role of fluid resuscitation and vasopressor administration, but did not specifically address the threshold for blood transfusion 5.
• A study protocol published in Acta anaesthesiologica Scandinavica in 2019 proposed a post hoc analysis of the Transfusion Requirements in Septic Shock (TRISS) trial to assess the effect of a lower vs a higher hemoglobin threshold for red blood cell transfusion in patients of different ages with septic shock 6.

Key Findings

• The evidence suggests that a lower hemoglobin threshold (7 g/dL) may be safe and effective for blood transfusion in septic shock patients, with similar outcomes to a higher threshold (9 g/dL) 2, 3.
• However, the optimal threshold may vary depending on patient age and other factors, and further research is needed to determine the best approach 6.
• Blood transfusion does not appear to be an independent predicting factor for mortality in septic patients, although hemoglobin level on admission is correlated with survival 4.