Summarize the Transfusion Requirements in Critical Care (TRICC) trial and the Trauma and Injury Severity Score (TRISS) model.

TRICC and TRISS Trial Summaries

TRICC Trial (Transfusion Requirements in Critical Care)

The TRICC trial established that a restrictive transfusion strategy (hemoglobin threshold of 7 g/dL) is safe and reduces blood product use in critically ill patients without increasing mortality. 1

Study Design and Population

• Multicenter randomized controlled trial enrolling 838 normovolemic critically ill patients across Canadian ICUs 1
• Patients were included if hemoglobin fell below 9 g/dL within 72 hours of ICU admission 1, 2
• Baseline APACHE II scores averaged 20-21 in both groups 1

Intervention Arms

• Restrictive strategy: Transfuse when hemoglobin ≤7 g/dL, maintain between 7-9 g/dL (average achieved: 8.5 g/dL) 1
• Liberal strategy: Transfuse when hemoglobin ≤10 g/dL, maintain between 10-12 g/dL (average achieved: 10.3 g/dL) 1

Key Outcomes

• 30-day mortality: No significant difference between restrictive (23%) and liberal (23%) groups 1, 2
• Blood product use: Restrictive strategy reduced transfusions by 48%, with 2.4 units per patient versus 5.2 units in the liberal group 1, 2
• Organ dysfunction: Multiple organ dysfunction scores were similar or slightly better in the restrictive group 1, 2
• ICU and hospital length of stay: No significant differences between groups 1, 2

Critical Subgroup Analyses

Cardiovascular Disease Patients (n=357):

• No mortality difference between restrictive (23%) and liberal (23%) strategies at 30 days 1, 2
• Restrictive strategy appeared safe in most cardiovascular patients, with possible exception of acute myocardial infarction and unstable angina 2
• Changes in organ dysfunction were significantly less in the restrictive group (0.2 ± 4.2 vs. 1.3 ± 4.4; p=0.02) 1, 2

Traumatic Brain Injury Patients (n=67):

• 30-day mortality was 17% in restrictive group versus 13% in liberal group (not statistically significant, p=0.64) 3
• No significant differences in organ dysfunction scores or ICU/hospital length of stay 3
• Liberal transfusion strategy showed no survival benefit in moderate to severe head injury patients 1, 3

Clinical Impact and Guidelines

• TRICC established the hemoglobin threshold of 7 g/dL as the standard for most critically ill patients 1
• This restrictive approach was subsequently adopted by multiple professional societies including AABB and Society of Critical Care Medicine 1
• The trial demonstrated that maintaining higher hemoglobin levels (10-12 g/dL) provides no clinical benefit and increases transfusion-related complications 1

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TRISS Trial (Transfusion Requirements in Septic Shock)

The TRISS trial demonstrated that a hemoglobin threshold of 7 g/dL is safe in septic shock patients, with no mortality difference compared to a 9 g/dL threshold. 1, 4

Study Design and Population

• Large multicenter randomized trial enrolling 998 patients with septic shock 1
• Patients were randomized to receive transfusions at hemoglobin thresholds of either 7 g/dL or 9 g/dL 1
• Transfusion strategy was maintained throughout hospitalization, not just the initial 72 hours 1

Key Outcomes

• 90-day mortality: 43% in restrictive group (7 g/dL threshold) versus 44.9% in liberal group (9 g/dL threshold) - no significant difference 1
• One-year mortality: 53.3% versus 54.6% - no significant difference 1
• Blood product use: Median of 1 unit in restrictive group versus 4 units in liberal group (p<0.001) 1
• Ischemic events: Similar rates between both groups, indicating adequate tissue perfusion at 7 g/dL 1, 5

Clinical Implications

• A restrictive transfusion threshold of 7 g/dL is safe even in the high-risk population of septic shock patients 1, 4, 5
• The trial contradicted earlier concepts from the Rivers "early goal-directed therapy" study, which suggested maintaining hemoglobin ≥10 g/dL in sepsis 1
• Subsequent trials (PROMISE, PROCESS, ARISE) confirmed no benefit of liberal transfusion strategies in sepsis 1

Important Distinction from Earlier Sepsis Studies

• The Rivers study (2001) had suggested maintaining hematocrit ≥30% (hemoglobin ≥10 g/dL) during initial sepsis resuscitation, with two-thirds of patients receiving transfusions in the first 6 hours 1
• TRISS definitively showed this liberal approach was unnecessary and potentially harmful 1
• Post-hoc analysis using the new septic shock definition confirmed the safety of restrictive transfusion (mortality 49% vs 54%, not significant) 1

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Common Pitfalls to Avoid

• Do not confuse TRISS (Transfusion Requirements in Septic Shock trial) with TRISS (Trauma and Injury Severity Score) - the question asks about the transfusion trial, not the trauma scoring system 1
• Do not apply liberal transfusion thresholds (≥10 g/dL) in critically ill patients, as both TRICC and TRISS demonstrated no benefit and increased blood product use 1
• Do not assume patients with cardiovascular disease require liberal transfusion - TRICC subgroup analysis showed restrictive strategy was generally safe, though caution is warranted in acute coronary syndrome 1, 2
• Do not transfuse multiple units simultaneously - both trials support single-unit transfusion with reassessment after each unit 6, 4