What are the indications for blood transfusion?

Indications for Blood Transfusion

Hemoglobin-Based Transfusion Thresholds

For most hospitalized adults who are hemodynamically stable, transfuse red blood cells when hemoglobin falls below 7 g/dL. 1, 2, 3

Standard Thresholds by Patient Population

• General hospitalized patients (hemodynamically stable): Hemoglobin < 7 g/dL 1, 2, 3
• Cardiac surgery patients: Hemoglobin < 7.5 g/dL 1, 3
• Orthopedic surgery patients: Hemoglobin < 8 g/dL 3
• Patients with preexisting cardiovascular disease or active coronary artery disease: Hemoglobin < 8 g/dL 1, 2, 4, 3
• Patients with acute coronary syndrome: Hemoglobin < 8 g/dL 1, 2
• Critically ill children (hemodynamically stable, without hemoglobinopathy): Hemoglobin < 7 g/dL 3

The restrictive strategy (7-8 g/dL threshold) is supported by 45 randomized controlled trials involving over 20,000 participants, demonstrating it is as effective as liberal strategies (9-10 g/dL) without increasing mortality, myocardial infarction, stroke, or infection. 1, 3

Hemoglobin Levels Where Transfusion is Almost Always Indicated

• Hemoglobin < 6 g/dL: Transfusion is almost always indicated, especially when anemia is acute. 5, 4

Hemoglobin Levels Where Transfusion is Rarely Necessary

• Hemoglobin > 10 g/dL: Transfusion is rarely necessary and may increase complications including nosocomial infections, multi-organ failure, and transfusion-associated circulatory overload. 5, 2, 4

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Absolute Indications for Immediate Transfusion (Regardless of Hemoglobin)

Transfuse immediately in hemorrhagic shock or hemodynamic instability, regardless of hemoglobin concentration. 1, 2

Signs of Hemorrhagic Shock Requiring Immediate Transfusion

• Systolic blood pressure < 90 mmHg 1
• Heart rate > 110 beats/min 1
• Bleeding rate > 150 mL/min 1
• Blood loss > 1500 mL 5, 4
• Acute blood loss > 30% of blood volume 6

Signs of End-Organ Ischemia Requiring Immediate Transfusion

• ST segment changes on ECG indicating cardiac ischemia 5, 1, 4
• Elevated serum lactate 1, 2
• Low pH 1
• Decreased mixed venous oxygen saturation 1, 4
• Chest pain or angina 4, 6
• Decreased urine output 5, 4
• Altered mental status 4
• Shortness of breath or dyspnea 4, 6
• Orthostatic hypotension or tachycardia unresponsive to fluid resuscitation 4
• Congestive heart failure 4, 6

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Clinical Decision-Making Algorithm

Step 1: Assess Hemodynamic Stability

• If hemorrhagic shock or hemodynamic instability is present (systolic BP < 90 mmHg, HR > 110 bpm, bleeding > 150 mL/min), transfuse immediately regardless of hemoglobin. 1, 2

Step 2: Measure Hemoglobin

• Obtain hemoglobin or hematocrit measurement when substantial blood loss occurs or any indication of organ ischemia is present. 5
• Perform repeated measurements to monitor dynamics of blood loss. 5

Step 3: Apply Risk-Stratified Hemoglobin Thresholds

• No cardiovascular disease: Transfuse at Hb < 7 g/dL 1, 2, 3
• Cardiovascular disease or acute coronary syndrome: Transfuse at Hb < 8 g/dL 1, 2, 4, 3
• Cardiac surgery: Transfuse at Hb < 7.5 g/dL 1, 3
• Orthopedic surgery: Transfuse at Hb < 8 g/dL 3

Step 4: Evaluate for Signs of Tissue Hypoxia

Monitor for evidence of inadequate oxygen delivery using: 5, 2

• Blood pressure and heart rate 5
• Oxygen saturation 5
• Urine output 5
• Electrocardiography for ST changes 5
• Serum lactate 2
• Mixed venous oxygen saturation 5
• Arterial blood gas 5
• Echocardiography when appropriate 5

Step 5: Monitor Blood Loss

• Conduct visual assessment of the surgical field for excessive microvascular bleeding (coagulopathy). 5
• Use standard quantitative methods: suction canister volume, surgical sponges, drains. 5
• Assess clot size and shape. 5

Step 6: Consider Patient-Specific Risk Factors

The decision to transfuse at intermediate hemoglobin concentrations (6-10 g/dL) should be based on: 5

• Ongoing indication of organ ischemia 5
• Potential or actual ongoing bleeding (rate and magnitude) 5
• Patient's intravascular volume status 5
• Low cardiopulmonary reserve 5
• High oxygen consumption 5

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Transfusion Administration Strategy

Non-Bleeding Patients

Transfuse one unit of red blood cells at a time and reassess clinical status and hemoglobin after each unit. 1, 2, 4, 3

• One unit of packed red blood cells increases hemoglobin by approximately 1-1.5 g/dL. 4
• This approach prevents over-transfusion and associated complications. 1, 2

Massive Hemorrhage

Administer blood products in a 1:1:1 ratio (red blood cells:plasma:platelets) and initiate early blood product replacement. 1, 2

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Contraindications and Situations to Avoid Transfusion

Do Not Transfuse When:

• Asymptomatic patients without significant comorbidities and hemoglobin > 7 g/dL 1, 2
• Hemoglobin > 10 g/dL (transfusion rarely necessary) 5, 2, 4
• For volume expansion when oxygen-carrying capacity is adequate 1, 2

Important Caveats

• Never base transfusion decisions solely on hemoglobin thresholds; always consider clinical context. 1, 2, 4
• Consider alternative therapies with fewer risks when available. 1, 2
• Be aware that hemodilution from IV fluids can cause falsely low hemoglobin values. 1
• Liberal transfusion strategies (transfusing to Hb > 10 g/dL) provide no benefit and may increase complications. 4

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Special Populations

Hematologic and Oncologic Disorders

• Use restrictive strategy with threshold of 7 g/dL. 1, 3
• Consider transfusion for progressive hemoglobin decrease after anticancer treatment, even without evident symptoms. 1

Cardiopulmonary Bypass with Moderate Hypothermia

• Transfusion trigger of 6 g/dL 1
• Higher threshold of 7 g/dL for those at risk of critical end-organ ischemia 1

Pediatric Congenital Heart Disease

• Biventricular repair: Hb < 7 g/dL 3
• Single-ventricle palliation: Hb < 9 g/dL 3
• Uncorrected congenital heart disease: Hb 7-9 g/dL 3

Chronic Kidney Disease

• Target hemoglobin 11.0-12.0 g/dL with erythropoiesis-stimulating agents after acute stabilization. 4
• Acute transfusion still needed at critically low hemoglobin levels (< 7 g/dL). 4

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Blood Conservation Strategies

Adjuvant Therapies to Reduce Transfusion

• Maintain adequate intravascular volume with crystalloids or colloids until transfusion criteria are met. 5
• Use intraoperative or postoperative blood recovery (cell salvage) when appropriate. 5
• Consider acute normovolemic hemodilution in appropriate surgical procedures (cardiac surgery, liver surgery, large orthopedic surgeries). 5
• Use deliberate hypotension when appropriate to decrease blood loss. 5