Systematic Review and Meta-Analysis of Effects of Transfusion on Hemodynamic and Oxygenation Variables
Critical care medicine. 2020;48(2):241-248
OBJECTIVES RBC transfusions can increase oxygen availability to the tissues, but studies have provided conflicting results. The objectives of this study were, therefore, to evaluate, using systematic review and meta-analysis, the effects of transfusion on hemodynamic/oxygenation variables in patients without acute bleeding. DATA SOURCES PubMed, Scopus, Cochrane Database of Systematic Reviews, and Embase from inception until June 30, 2019. STUDY SELECTION All articles that reported values of prespecified hemodynamic or oxygenation variables before and after RBC transfusion. DATA EXTRACTION Publication year, number of patients, number of transfusions and the type of population studied, hemodynamic and oxygenation data (heart rate, cardiac index, mixed venous oxygen saturation or central venous oxygen saturation, oxygen delivery index, oxygen consumption index, oxygen extraction ratio, arteriovenous oxygen difference and arterial blood lactate) before and after transfusion. We performed a meta-analysis for each variable for which there were sufficient data to estimate mean differences. We also performed subgroup analyses comparing septic with nonseptic patients. DATA SYNTHESIS We retrieved 6,420 studies; 33 met the inclusion criteria, 14 of which were in patients with sepsis. In the meta-analysis, the estimated mean differences and 95% CIs comparing the periods before and after transfusion were -0.0 L/min/m (-0.1 to 0.1 L/min/m) (p = 0.86) for cardiac index; -1.8 beats/min (-3.7 to 0.1 beats/min) (p = 0.06) for heart rate; 96.8 mL/min/m (71.1-122.5 mL/min/m) (p < 0.01) for oxygen delivery index; 2.9% (2.2-3.5%) (p < 0.01) for mixed venous oxygen saturation or central venous oxygen saturation; -3.7% (-4.4% to -3.0%) (p < 0.01) for oxygen extraction ratio; and 4.9 mL/min/m (0.9-9.0 mL/min/m) (p = 0.02) for oxygen consumption index. The estimated mean difference for oxygen consumption index in the patients with sepsis was 8.4 mL/min/m (2.3-14.5 mL/min/m; p = 0.01). CONCLUSIONS Transfusion was not associated with a decrease in mean cardiac output or mean heart rate. The increase in mean oxygen delivery following transfusion was associated with an increase in mean oxygen consumption after transfusion, especially in patients with sepsis.
Transfusion requirements after head trauma: a randomized feasibility controlled trial
Critical care (London, England). 2019;23(1):89
BACKGROUND Anemia is frequent among patients with traumatic brain injury (TBI) and is associated with an increased risk of poor outcome. The optimal hemoglobin concentration to trigger red blood cell (RBC) transfusion in patients with TBI is not clearly defined. METHODS All eligible consecutive adult patients admitted to the intensive care unit (ICU) with moderate or severe TBI were randomized to a "restrictive" (hemoglobin transfusion threshold of 7 g/dL), or a "liberal" (threshold 9 g/dL) transfusion strategy. The transfusion strategy was continued for up to 14 days or until ICU discharge. The primary outcome was the mean difference in hemoglobin between groups. Secondary outcomes included transfusion requirements, intracranial pressure management, cerebral hemodynamics, length of stay, mortality and 6-month neurological outcome. RESULTS A total of 44 patients were randomized, 21 patients to the liberal group and 23 to the restrictive group. There were no baseline differences between the groups. The mean hemoglobin concentrations during the 14-day period were 8.4 +/- 1.0 and 9.3 +/- 1.3 (p < 0.01) in the restrictive and liberal groups, respectively. Fewer RBC units were administered in the restrictive than in the liberal group (35 vs. 66, p = 0.02). There was negative correlation (r = - 0.265, p < 0.01) between hemoglobin concentration and middle cerebral artery flow velocity as evaluated by transcranial Doppler ultrasound and the incidence of post-traumatic vasospasm was significantly lower in the liberal strategy group (4/21, 3% vs. 15/23, 65%; p < 0.01). Hospital mortality was higher in the restrictive than in the liberal group (7/23 vs. 1/21; p = 0.048) and the liberal group tended to have a better neurological status at 6 months (p = 0.06). CONCLUSIONS The trial reached feasibility criteria. The restrictive group had lower hemoglobin concentrations and received fewer RBC transfusions. Hospital mortality was lower and neurological status at 6 months favored the liberal group. TRIAL REGISTRATION ClinicalTrials.gov, NCT02203292 . Registered on 29 July 2014.
The effects of storage of red blood cells on the development of postoperative infections after noncardiac surgery
BACKGROUND Prolonged storage of red blood cells (RBCs) is a potential risk factor for postoperative infections. The objective of this study was to examine the effect of age of RBCs transfused on development of postoperative infection. STUDY DESIGN AND METHODS In this prospective, double-blind randomized trial, 199 patients undergoing elective noncardiac surgery and requiring RBC transfusion were assigned to receive nonleukoreduced RBCs stored for not more than 14 days ("fresh blood" group, n = 101) or for more than 14 days ("old blood" group, n = 98). The primary outcome was occurrence of infection within 28 days after surgery; secondary outcomes were postoperative acute kidney injury (AKI), in-hospital and 90-day mortality, admission to intensive care unit, and hospital length of stay (LOS). As older blood was not always available, an "as-treated" (AT) analysis was also performed according to actual age of the RBCs transfused. RESULTS The median [interquartile range] storage time of RBCs was 6 [5-10] and 15 [11-20] days in fresh blood and in old blood groups, respectively. The occurrence of postoperative infection did not differ between groups (fresh blood 22% vs. old blood 25%; relative risk [RR], 1.17; confidence interval [CI], 0.71-1.93), although wound infections occurred more frequently in old blood (15% vs. 5%; RR, 3.09; CI, 1.17- 8.18). Patients receiving older units had a higher rate of AKI (24% vs. 6%; p < 0.001) and, according to AT analysis, longer LOS (mean difference, 3.6 days; CI, 0.6-7.5). CONCLUSION Prolonged RBC storage time did not increase the risk of postoperative infection. However, old blood transfusion increased wound infections rate and incidence of AKI.
Transfusion strategies in patients with traumatic brain injury: which is the optimal hemoglobin target?
Minerva Anestesiologica. 2016;82((1)):112-6.
Robertson et al. (JAMA 2014; 312:36-47) investigated the effects of two different thresholds of hemoglobin (Hb) to guide red blood cells transfusions (RBCT; 7 g/dL vs. 10 g/dL) in patients suffering from traumatic brain injury (TBI). In a two-center, controlled, open-label trial (from May 2006 and August 2012), comatose patients with a closed TBI were randomized within 6 hours since initial resuscitation to one of the two RBCT strategies and, in a factorial design (2x2), to receive erythropoietin (EPO) or placebo. Patients were excluded if they had a Glasgow Coma Scale (GCS) score of 3 with fixed and dilated pupils, penetrating trauma, pregnancy, life-threatening systemic injuries and severe preexisting diseases. A total of 200 patients (7 g/dL with [N.=49] or without EPO [N. =50]; 10 g/dL with [N.=53] or without EPO [N.=48]) were enrolled among 598 who were screened. There was no interaction between EPO and Hb thresholds on the primary outcome, which was the occurrence of favorable neurological outcome, assessed using the Glasgow Outcome Scale (GOS) at 6 months after the injury (favorable=GOS 4-5). Favorable outcome was similar between patients included in the 7 g/dL (37/87-43%) and the 10 g/dL group (31/94-33%) as if receiving EPO or placebo, even after adjustment for several covariates. Thromboembolic events were significantly more frequent in the group transfused at 10 g/dL (22/101 [22%] vs. 8/99 [8%]; P=0.009). We discussed how theses results might influence the management of such patients as well as the methodological limitations that underline the need for further investigations.