What are the indications for blood transfusion?

Indications for Blood Transfusion

Blood transfusion is primarily indicated for patients with evidence of hemorrhagic shock, acute hemorrhage with hemodynamic instability, or inadequate oxygen delivery to tissues that is unresponsive to crystalloid resuscitation. 1

Primary Indications for Red Blood Cell Transfusion

Hemorrhagic Shock and Acute Blood Loss

• RBC transfusion is strongly indicated for patients with evidence of hemorrhagic shock 1
• Indicated in patients with acute hemorrhage who remain hemodynamically unstable despite crystalloid resuscitation 1
• Initial treatment should begin with isotonic crystalloid solutions, with RBC transfusion indicated when patients are unresponsive to 2L of crystalloid or have ongoing hemorrhage 1
• Decision to transfuse during acute hemorrhage should be based on physiologic state, evidence of blood loss, and potential for ongoing bleeding, not solely on hemoglobin concentration 1

Hemoglobin-Based Transfusion Thresholds

• Restrictive transfusion strategy is recommended for most critically ill patients 1
• Hemoglobin thresholds for transfusion:
  • <7 g/dL: Transfusion generally indicated in critically ill patients 1
  • <8 g/dL: Consider in perioperative patients and those with cardiovascular disease 1

  • 10 g/dL: Transfusion generally unnecessary 1

  • 7-10 g/dL: Decision should be based on evidence of organ ischemia, ongoing bleeding, intravascular volume status, and patient risk factors 1

Physiologic Indications

• To increase oxygen delivery to tissues when inadequate 1
• To alleviate symptoms of anemia (dyspnea, fatigue, diminished exercise tolerance) 1
• To relieve cardiac effects of severe anemia with critical oxygen delivery 1
• For symptomatic anemia (maternal tachycardia >110 beats per minute, dizziness, syncope) with Hb 7-8 g/dL 2

Special Clinical Scenarios

Trauma and Critical Care

• Prehospital: Blood components recommended over crystalloids for first-line treatment of traumatic life-threatening bleeding 3
• Low titer group O whole blood is the first-choice product for prehospital treatment of traumatic life-threatening bleeding 3
• Blood lactate or base deficit measurements help monitor metabolism related to hypoperfusion and extent of hemorrhagic shock 1
• Shock index (heart rate/systolic BP) >1 is a reliable indicator of significant bleeding requiring intervention 4

Gastrointestinal Bleeding

• Initial hemoglobin <80 g/L is a significant risk factor for complications and mortality in lower GI bleeding requiring surgery 5
• Need for >10 units of blood transfusion is associated with higher mortality in GI bleeding 5
• Early consideration of surgery or interventional procedures is crucial in uncontrolled GI bleeding 4

Perioperative Setting

• Maintain adequate intravascular volume with crystalloids or colloids until transfusion criteria are met 1
• Intraoperative or postoperative blood recovery and other means to decrease blood loss (e.g., deliberate hypotension) should be considered 1
• Perioperative blood product use is associated with increased risk of complications and mortality, emphasizing the need for judicious use 6

Postpartum Hemorrhage

• Criteria for blood transfusion in PPH include:
  • Clinically severe uncontrollable ongoing hemorrhage
  • Symptomatic anemia with Hb 7-8 g/dL
  • Postpartum Hb level <7 g/dL regardless of symptoms 2
• Combination of shock index, immediate postpartum Hb, and lactate levels can predict need for blood transfusion in PPH 2

Risks and Complications of Transfusion

• Fluid overload, pulmonary edema, posttransfusion circulatory overload 1
• Fever and acute transfusion reactions 1
• Increased multiple organ failure 1
• Increased infection risk 1
• Transfusion-associated immunomodulation (TRIM) 1
• Transfusion-related acute lung injury 1
• Human error—incorrect blood component 1
• Thromboembolic events 7

Monitoring During Transfusion

• Visual assessment of the surgical field to assess microvascular bleeding 1
• Standard methods for quantitative measurement of blood loss (e.g., suction and sponge) 1
• Conventional monitoring systems (blood pressure, heart rate, oxygen saturation, urine output, ECG) to assess adequacy of perfusion and oxygenation 1
• Special monitoring systems when appropriate (echocardiography, mixed venous oxygen saturation, blood gases) 1
• Active monitoring for transfusion-related adverse events 3

Common Pitfalls to Avoid

• Underestimating blood loss, as hemoglobin and hematocrit values do not fall for several hours after acute hemorrhage 1
• Relying solely on hemoglobin levels without considering the patient's clinical status and risk factors 1
• Assuming hemodynamic stability means adequate tissue oxygenation, as silent ischemia may occur despite stable vital signs 1
• Delaying transfusion in cases of massive hemorrhage 1
• Failing to prevent and treat coagulopathy, hypothermia, acidosis, and hypocalcemia during massive transfusion 4
• Overlooking the need for early FFP infusion to prevent dilutional coagulopathy in massive hemorrhage 4

By following these evidence-based indications and considering both the benefits and risks of blood transfusion, clinicians can optimize patient outcomes while minimizing unnecessary transfusions and their associated complications.