A clinical scenario-based survey of transfusion decisions for intensive care patients with delayed weaning from mechanical ventilation.

BACKGROUND: Despite evidence supporting the use of restrictive hemoglobin (Hb) transfusion triggers in critically ill patients, translation of this evidence into practice remains inconsistent. It was hypothesized that clinicians believe that longer-term ventilated patients require a higher Hb, particularly when ischemic heart disease coexists. STUDY DESIGN AND METHODS: A scenario was developed describing an anemic patient recovering from multiple organ failure, but failing weaning trials after 6 days of mechanical ventilation. Clinicians were asked to state their Hb transfusion trigger and target Hb range assuming no history of ischemic heart disease (Scenario 1), known stable chronic ischemic heart disease (Scenario 2), or evidence of myocardial ischemia during weaning trials (Scenario 3). A prospective cross-sectional postal survey of clinicians practicing intensive care in the United Kingdom was undertaken. RESULTS: A total of 184 responses were obtained (52% response rate), which varied widely. Median (first, third quartile) transfusion trigger Hb levels were 8 (7, 8), 9 (8, 9.5), and 9.5 (9, 9.5) g/dL for Scenarios 1 to 3, respectively (p < 0.001 across and between each group). The target Hb was more than 9 g/dL for 47, 80, and 94% of respondents for Scenarios 1 to 3, respectively, and more than 10 g/dL for 14, 44, and 65% of respondents for Scenarios 1 to 3, respectively (p < 0.001 across the groups). CONCLUSIONS: In response to scenarios, clinicians in the United Kingdom believe that a more liberal transfusion practice is required for patients failing weaning trials after 6 days of mechanical ventilation than the current evidence base supports.

Anemia during and at discharge from intensive care: the impact of restrictive blood transfusion practice.

OBJECTIVE: To document the prevalence of anemia among patients admitted to intensive care (ICU) and, among survivors, at ICU discharge when restrictive transfusion practice was used. DESIGN: This was an observational cohort study. SETTING: Ten of the 26 general ICUs in Scotland. PATIENTS AND PARTICIPANTS: One thousand twenty-three sequential ICU admissions over 100 days, representing 44% of all ICU admissions in Scotland during the study period, studied daily from admission to discharge or death in the ICU. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: The median transfusion trigger used, in the absence of bleeding, was 78 g/l (interquartile range 73-84); <2% of transfusion triggers were above the upper limit of the national transfusion trigger guideline (100 g/l). Overall, 25% of admissions had a hemoglobin concentration <90 g/l at ICU admission. Seven hundred sixty-six patients admitted survived to ICU discharge. Among these, the prevalence of anemia (male <130 g/l; female <115 g/l) at ICU discharge was 87.0 (95% CI: 83.6 to 89.9)% for males and 79.6 (74.8 to 83.7)% for females. Of the male survivors 24.1 (20.3 to 28.3)% and of the female 27.9 (23.4 to 33.2)% had a hemoglobin <90 g/l at ICU discharge. The prevalence was similar for patients with and without pre-existing ischemic heart disease. Logistic regression found independent associations between having a hemoglobin concentration <90 g/l at ICU discharge and the first measured hemoglobin in ICU, the presence of acute renal failure and thrombocytopenia during ICU stay. CONCLUSIONS: Anemia is highly prevalent in ICUs that use restrictive transfusion triggers. The impact of anemia on functional recovery after intensive care requires investigation.

Red cell requirements for intensive care units adhering to evidence-based transfusion guidelines.

BACKGROUND: Anemia commonly complicates critical illness. Restrictive transfusion triggers are appropriate in this setting, but no large studies have measured red cell (RBC) requirements for intensive care patients when evidence-based transfusion guidelines are followed consistently. STUDY DESIGN AND METHODS: Data were recorded daily for 1023 of 1042 sequential admissions to 10 intensive care units (ICUs) over 100 days. The sample comprised 44 percent of all ICU admissions in Scotland during this period. RBC transfusions and the occurrence of clinically significant hemorrhage were recorded for every ICU day. Transfusion episodes were classified as either associated with or not associated with hemorrhage. Measures of RBC use were derived for the cohort and for Scotland with national audit data. RESULTS: A total of 39.5 percent (95% confidence interval [CI], 36.5%-42.5%) of admissions received transfusions. Eighteen percent of admissions received at least one transfusion associated with hemorrhage and 26 percent received at least one transfusion not associated with hemorrhage. The median (interquartile range) transfusion trigger in the absence of hemorrhage was 78 (73-78) g/L. The overall mean RBC use was 1.87 (95% CI, 1.79-1.96) units per admission or 0.34 (95% CI, 0.33-0.36) units per ICU-day. Forty-seven percent of RBCs administered were not associated with clinically significant hemorrhage. Mean RBC requirements for intensive care in Scotland were estimated to be 3950 (95% CI, 3780-4140) per million-adult-population per year. This represented 7 to 8 percent of the Scottish blood supply. CONCLUSIONS: Despite evidence-based transfusion practice, 40 percent of ICU patients receive transfusions, which account for 7 to 8 percent of the national blood supply.

Does the storage time of transfused red blood cells influence regional or global indexes of tissue oxygenation in anemic critically ill patients?

OBJECTIVE: To determine whether transfusion of red cells either < or =5 days or > or =20 days from donation alters tonometric indexes of gastric mucosal oxygenation or global oxygenation parameters in euvolemic anemic critically ill patients without ongoing hemorrhage. The a priori hypothesis was that stored red cells worsen gastric oxygenation. DESIGN: Prospective, double-blind, randomized study. SETTING: A 12-bed general medical/surgical intensive care unit in a Scottish teaching hospital. PATIENTS: Ventilated euvolemic anemic (mean +/- sd hemoglobin, 85.8 +/- 8.4 g/L) critically ill patients with significant organ failure, but no evidence of hemorrhage. INTERVENTIONS: After baseline measurements, patients were randomized to receive two units of leukodepleted red cells that were either < or =5 days (ten patients) or > or =20 days (12 patients) after donation according to a standardized protocol. MEASUREMENTS AND MAIN RESULTS: Changes in gastric to arterial Pco2 gap (Pg-Paco2 gap), gastric intramucosal pH, arterial pH, arterial base excess, and arterial lactate concentrations were measured during baseline (2.5 hrs), during transfusion (3 hrs), and for 5 hrs after transfusion. Mean age of red cells stored < or =5 days was 2 days (first and third quartile, 2, 2.25; range, 2-3); red cells stored >/=20 days had a mean age of 28 days (first and third quartile, 27, 31; range, 22-32). Hemoglobin concentration increased by 15.0 g/L and 16.6 g/L, respectively, in the fresh and stored groups (p =.62). There were no significant differences between the groups either using treatment-by-time analysis or comparing the pre- and posttransfusion periods either for Pg-Paco2 gap (mean difference, 0.03 kPa; 95% confidence limits, -1.66, 1.72) or gastric intramucosal pH (mean difference, 0.015 pH units; 95% confidence limits, -0.054, 0.084). The mean change within each group from the pre- to posttransfusion period for Pg-Paco2 gap and gastric intramucosal pH, respectively, was 0.56 kPa (95% confidence limits, -0.68, 1.79) and -0.018 pH units (95% confidence limits, -0.069, 0.032) for "fresh" red cells and 0.52 kPa (95% confidence limits, -0.6, 1.64) and -0.033 pH units (95% confidence limits, -0.080, 0.129) for "stored" red cells. There was no statistically or clinically significant improvement in any other oxygenation index during the measurement period for either group compared to baseline values. CONCLUSIONS: Transfusion of stored leukodepleted red cells to euvolemic, anemic, critically ill patients has no clinically significant adverse effects on gastric tonometry or global indexes of tissue oxygenation. These findings do not support the use of fresh red cells in critically ill patients.