What are the indications for blood transfusions?

Blood Transfusion Indications

For hemodynamically stable patients without active bleeding, transfuse red blood cells when hemoglobin falls below 7 g/dL, with higher thresholds of 8 g/dL for patients with active ischemic heart disease or acute coronary syndrome. 1

Hemoglobin-Based Transfusion Triggers

Standard Threshold (Hemodynamically Stable Patients)

• Transfuse at hemoglobin < 7 g/dL in most hospitalized adults who are hemodynamically stable 1, 2
• This restrictive strategy is supported by 45 randomized controlled trials involving over 20,000 participants, showing no adverse effects on patient outcomes compared to liberal strategies 2
• The restrictive approach (Hb < 7 g/dL) is as effective as liberal strategies (Hb < 10 g/dL) in critically ill patients, including those on mechanical ventilation and trauma patients 1

Higher Thresholds for Specific Populations

• Cardiac surgery patients: 7.5 g/dL 3, 2
• Orthopedic surgery patients: 8 g/dL 2
• Active ischemic heart disease or acute coronary syndrome: 8 g/dL 1, 2
• Patients with coronary artery disease (intraoperative): 8 g/dL 3
• Patients with angina, heart failure, or on beta-blockers (intraoperative): 10 g/dL 3
• Cardiovascular disease or high risk (elderly, peripheral vascular disease): 9 g/dL 3

Pediatric Thresholds

• Critically ill children (hemodynamically stable): 7 g/dL 2
• Biventricular repair congenital heart disease: 7 g/dL 2
• Single-ventricle palliation: 9 g/dL 2
• Uncorrected congenital heart disease: 7-9 g/dL 2

Absolute Indications (Regardless of Hemoglobin Level)

Hemorrhagic Shock and Active Bleeding

• Transfuse immediately in hemorrhagic shock, regardless of hemoglobin concentration 1
• Systolic blood pressure < 90 mmHg with bleeding 3, 4
• Heart rate > 110 beats/min with bleeding 3, 4
• Bleeding rate > 150 mL/min 3, 4
• Blood loss > 30% of total blood volume 5
• Blood loss > 1500 mL (intraoperative) 3
• Acute blood loss of 50% of total blood volume in < 3 hours 3

Signs of Inadequate Tissue Oxygenation

• ST segment changes on ECG indicating cardiac ischemia 3, 1, 4
• Elevated serum lactate 3, 1, 4
• Low pH (metabolic acidosis) 3, 4
• Low mixed venous oxygen saturation 3, 1, 4
• Decreased central venous oxygen saturation 3
• Tachypnea or dyspnea 4
• Postural hypotension 4
• Confusion or altered mental status 4
• Decreased urine output 3, 1

Clinical Decision-Making Algorithm

Step 1: Assess Hemodynamic Stability

• If hemorrhagic shock or hemodynamic instability present → transfuse immediately 1
• If hemodynamically stable → proceed to Step 2

Step 2: Measure Hemoglobin

• Use laboratory measurement as gold standard; near-patient testing acceptable for rapid assessment 3
• Important caveat: Hemoglobin may remain falsely elevated during active bleeding due to inadequate fluid resuscitation 3, 4

Step 3: Apply Risk-Stratified Threshold

• No cardiovascular disease: 7 g/dL 1, 2
• Cardiovascular disease/acute coronary syndrome: 8 g/dL 1, 2
• Intraoperative with specific cardiac conditions: up to 10 g/dL 3

Step 4: Evaluate for Signs of Tissue Hypoxia

• Check for ST changes, elevated lactate, low pH, decreased oxygen saturation 1, 4
• If present → transfuse regardless of hemoglobin level 4

Step 5: Monitor Blood Loss

• Quantify blood loss from surgical field, drains, sponges, suction canister 3, 1
• If ongoing significant bleeding → transfuse proactively 3

Transfusion Administration Strategy

Dosing Approach

• Transfuse one unit at a time and reassess in non-bleeding patients 1
• This single-unit approach prevents over-transfusion and associated complications 3, 1
• Measure hemoglobin before and after each unit in normovolemic patients without active bleeding 3

Massive Hemorrhage Protocol

• Administer blood products in 1:1:1 ratio (red blood cells:plasma:platelets) 1
• Initiate early blood product replacement based on blood loss 3

Contraindications and Situations to Avoid Transfusion

When NOT to Transfuse

• Hemoglobin > 10 g/dL: transfusion rarely necessary 1
• Asymptomatic patients without significant comorbidities and Hb > 7 g/dL 4
• For volume expansion when oxygen-carrying capacity is adequate 1

Important Caveats

• Do not base transfusion decisions solely on hemoglobin thresholds 4
• Hemodilution from IV fluids can cause falsely low hemoglobin values 4
• Acute anemia is less well-tolerated than chronic anemia due to lack of compensatory mechanisms 4
• Consider alternative therapies with fewer risks when available 1

Special Populations

Hematologic and Oncologic Disorders

• Use restrictive strategy with threshold of 7 g/dL 2
• Consider transfusion for progressive hemoglobin decrease after anticancer treatment, even without evident symptoms 4

Acute Sickle Cell Crisis

• Transfusion indicated for symptomatic anemia 5

Cardiopulmonary Bypass (Moderate Hypothermia)

• Transfusion trigger: 6 g/dL 3
• Higher threshold (7 g/dL) for those at risk of critical end-organ ischemia 3