Blood Transfusion Indications
Red blood cell transfusion should be administered when hemoglobin falls below 7 g/dL in most patients, with a lower threshold of 6 g/dL representing an almost universal indication for immediate transfusion, particularly in acute anemia. 1
Hemoglobin-Based Transfusion Thresholds
Standard Threshold (Most Patients)
- Transfuse at hemoglobin <7 g/dL (70 g/L) in hemodynamically stable patients without active bleeding 1
- This restrictive strategy applies to critically ill patients, including those with ARDS and septic shock 1
- Hemoglobin <6 g/dL almost always requires immediate transfusion, especially when anemia is acute 1, 2
Higher Threshold (Cardiovascular Disease)
- Transfuse at hemoglobin <8 g/dL (80 g/L) in patients with ischemic heart disease, acute coronary syndrome, or after cardiac surgery 1, 2
- This higher threshold accounts for increased oxygen demand and reduced cardiopulmonary reserve 1
Upper Limit
- Do not transfuse when hemoglobin >10 g/dL unless exceptional circumstances exist 1
- Transfusion above this threshold provides no clinical benefit and increases complications 2
Clinical Assessment Beyond Hemoglobin
Never use hemoglobin level alone as a transfusion trigger. The decision must incorporate: 1, 2
Signs of Inadequate Oxygen Delivery
- Elevated blood lactate concentration 1
- Low central or mixed venous oxygen saturation 1
- ST-segment changes on ECG or chest pain 2
- Decreased urine output 2
- Altered mental status 2
Hemodynamic Parameters
- Blood pressure (systolic <90 mmHg suggests major hemorrhage) 1
- Heart rate (>110 beats/min suggests major hemorrhage) 1
- Oxygen saturation 1
- Temperature (hypothermia worsens coagulopathy) 1
Bleeding Assessment
- Rate of ongoing blood loss (>150 mL/min defines major hemorrhage) 1
- Magnitude of total blood loss (>50% blood volume in <3 hours) 1
- Visual assessment for microvascular bleeding suggesting coagulopathy 1
Major Hemorrhage Protocol
Definition
Major hemorrhage is defined as: 1
- Loss of >50% total blood volume in <3 hours
- Bleeding >150 mL/min
- Systolic BP <90 mmHg with heart rate >110 beats/min
Management Approach
- Prioritize early hemorrhage control using temporary hemostatic devices (pressure, tourniquets), followed by definitive surgery or interventional radiology 1
- Avoid normalizing blood pressure during active hemorrhage—maintain lower acceptable BP with volume resuscitation alone (permissive hypotension) 1
- Exception: modify this approach in traumatic brain injury where brain perfusion is the dominant concern 1
Tranexamic Acid Administration
- Give 1 g IV over 10 minutes within 3 hours of injury in major trauma (including mild-to-moderate traumatic brain injury), followed by 1 g infusion over 8 hours 1
- Reduces mortality in bleeding trauma patients 1
- Alternative: 2 g IV over 20 minutes as single bolus 1
Transfusion Administration Protocol
Single-Unit Strategy
- Transfuse one unit at a time, then reassess clinical status and hemoglobin before administering additional units 1, 2
- Each unit increases hemoglobin by approximately 1-1.5 g/dL 2, 3
Target Hemoglobin
- Aim for post-transfusion hemoglobin of 7-9 g/dL in most patients 1, 2, 3
- Higher targets provide no additional benefit and increase complications 1, 2
Volume Resuscitation
- Maintain intravascular volume with crystalloids or colloids until red blood cell transfusion criteria are met 1
- Adequate quantities of red blood cells should be transfused to maintain organ perfusion 1
Management of Coagulopathy
Monitoring
- Conduct visual assessment of surgical field for excessive microvascular bleeding 1
- Use point-of-care or laboratory testing to guide management 1
Metabolic Optimization
During resuscitation, prevent or treat: 1
- Hypothermia (maintain normothermia)
- Acidosis (correct metabolic acidosis)
- Hypocalcemia (aim for ionized calcium >1.0 mmol/L)
Blood Product Administration
- Fresh frozen plasma for reversal of anticoagulant effects 4
- Platelets for thrombocytopenia or platelet dysfunction 4, 5
- Cryoprecipitate for hypofibrinogenemia in massive hemorrhage 4
Special Populations
Critical Care Patients
- Use restrictive threshold of hemoglobin <7 g/dL in mechanically ventilated patients, including those with ARDS and septic shock 1
- Hemoglobin drops by mean 0.52 g/L per day in ICU 1
- 30-40% of critically ill patients develop moderate-severe anemia (Hb <9 g/dL) during ICU stay 1
Pediatric Patients
- Hemoglobin <5.5-6 g/dL represents life-threatening anemia requiring immediate transfusion 6
- Transfusion volume: Weight (kg) × Desired Hb rise (g/dL) × 3 6
- Alternative: 10-15 mL/kg of packed red blood cells 6
- Transfuse slowly over 2-4 hours to avoid volume overload 6
Surgical Patients
- Measure hemoglobin when substantial blood loss or organ ischemia occurs 1
- Hemoglobin 6-10 g/dL requires individualized assessment based on ongoing bleeding, intravascular volume, and risk factors for inadequate oxygenation 1
Critical Pitfalls to Avoid
Liberal Transfusion Strategy
- Avoid transfusing to hemoglobin >10 g/dL—this increases nosocomial infections, multi-organ failure, TRALI, and transfusion-associated circulatory overload without benefit 2, 3
- Liberal strategies provide no mortality benefit compared to restrictive approaches 1, 2
Hemoglobin as Sole Trigger
- Never base transfusion decisions on hemoglobin alone—hemoglobin may remain falsely elevated despite significant blood loss due to inadequate fluid resuscitation 1
- Hemoglobin may fall due to hemodilution from IV fluids without actual blood loss 1
Transfusion Risks
- Transfusion-related acute lung injury (TRALI) 2, 3, 7
- Transfusion-associated circulatory overload (particularly in pediatrics and elderly) 6, 2
- Infections (though dramatically reduced with modern screening) 6, 2, 7
- Immunosuppression 2, 3
- Hemolytic reactions 7