Chest
Volume 119, Issue 6, June 2001, Pages 1850-1857
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Clinical Investigations in Critical Care
Do Blood Transfusions Improve Outcomes Related to Mechanical Ventilation?

https://doi.org/10.1378/chest.119.6.1850Get rights and content

Background

Correcting the decrease in oxygen delivery from anemia using allogeneic RBC transfusions has been hypothesized to help with increased oxygen demands during weaning from mechanical ventilation. However, it is also possible that transfusions hinder the process because RBCs may not be able to adequately increase oxygen delivery. In this study, we determined whether a liberal RBC transfusion strategy improved outcomes related to mechanical ventilation.

Methods

Seven hundred thirteen patientsreceiving mechanical ventilation, representing a subgroup of patients from a larger trial, were randomized to either a restrictive transfusion strategy, receiving allogeneic RBC transfusions at a hemoglobin concentration of 7.0 g/dL (and maintained between 7.0 g/dLand to 9.0 g/dL), or to a liberal transfusion strategy, receiving RBCsat 10.0 g/dL (and maintained between 10.0 g/dL and 12.0 g/dL). The larger trial was designed to evaluate transfusion practice rather than weaning per se.

Results

Baseline characteristics in the restrictive-strategy group (n = 357) and the liberal-strategy group (n = 356) were comparable. The average durations of mechanical ventilation were 8.3 ± 8.1 days and8.3 ± 8.1 days (95% confidence interval [CI] around difference,−0.79 to 1.68; p = 0.48), while ventilator-free days were17.5 ± 10.9 days and 16.1 ± 11.4 days (95% CI around difference,−3.07 to 0.21; p = 0.09) in the restrictive-strategy group vs the liberal-strategy group, respectively. Eighty-two percent of the patients in the restrictive-strategy group were considered successfully weaned and extubated for at least 24 h, compared to 78% for theliberal-strategy group (p = 0.19). The relative risk (RR) of extubation success in the restrictive-strategy group compared to theliberal-strategy group, adjusted for the confounding effects of age, APACHE (acute physiology and chronic health evaluation) II score, and comorbid illness, was 1.07 (95% CI, 0.96 to 1.26; p = 0.43). Theadjusted RR of extubation success associated with restrictive transfusion in the 219 patients who received mechanical ventilation for >7 days was 1.1 (95% CI, 0.84 to 1.45; p = 0.47).

Conclusion

In this study, there was no evidence that aliberal RBC transfusion strategy decreased the duration of mechanical ventilation in a heterogeneous population of critically illpatients.

Section snippets

Description of the TRICC Trial

The TRICC trial9 was a randomized, controlled trial that enrolled 838 critically ill patients with hemoglobin concentrations ≤ 9.0 g/dL within 72 h of ICU admission, and were considered volume resuscitated by the attending ICU staff. Patients with chronic anemia and acute severe blood loss, defined as a decrease in hemoglobin concentration > 30 g/L or a requirement for three RBC units in 12 h, were excluded from the TRICC trial, as well as this analysis. Physicians caring for patients allocated

Study Population

The TRICC trial randomized 838 patients (418 in the restrictive allogeneic transfusion group and 420 in the liberal-strategy group). In total, 713 patients (85%) required mechanical ventilation, 357 in the restrictive-strategy group and 356 in the liberal-strategy group. All patients in this analysis completed the trial and were followed up for 30 days. Two patients were unavailable for follow-up at 60 days.

All baseline characteristics were equally balanced between the treatment groups among

Discussion

In summary, we found no significant differences in the duration of mechanical ventilation, in the number of ventilator-free days, or in the time necessary to successfully wean and extubate patients from mechanical ventilation among those receiving a restrictive transfusion strategy vs a liberal transfusion strategy. This was true for all patients receiving mechanical ventilation and in the subgroup who required mechanical ventilation for > 7 days. Therefore, hemoglobin concentrations and RBC

TRICC Trial Executive and Writing Committee

Paul C. Hébert, MD, Irwin Schweitzer, MSc, Ottawa Hospital, General Campus; George Wells, PhD, MSc, Guiseppe Pagliarello, MD, Ottawa Hospital, Civic Campus; Morris Blajchman, MD, McMaster University, Hamilton; John Marshall, MD, Toronto Hospital, General Division; Claudio Martin, MD, MSc, Victoria Hospital, London; Martin Tweeddale, MD, PhD, Vancouver General Hospital.

TRICC Investigators

Paul C. Hébert, MD, Ottawa Hospital, General Campus; Guiseppe Pagliarello, MD, Ottawa Hospital, Civic Campus; John Marshall, MD,

ACKNOWLEDGMENT

We thank Drs. Graeme Rocker, Darren Heyland, Jacques Lacroix, Thomas Todd, and the members of the Canadian Critical Care Trials group; the nurses and critical care teams who provided medical care; and Christine Piché for secretarial support. We also thank Dr. Mark Pickett, Director of Research and Development at Bayer Inc., and Dr. Bert T. Aye, former Director of the Canadian Red Cross Society Blood Services.

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      In a post hoc analysis, in patients with APACHE II scores less than 20 and with ages younger than 55 years of age, significant reductions in 30-day mortality were found. A liberal transfusion strategy did not speed extubation in mechanically ventilated patients.32 In pediatric patients, a similar trial compared a restrictive (Hgb < 7 g/dL) vs liberal (Hgb < 9.5 g/dL) transfusion strategy.33

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    Drs. Hébert and Cook are Career Scientists of the Ontario Ministry of Health.

    This study was supported by the Medical Research Council of Canada and an unrestricted grant from Bayer Inc.

    A list of other study investigators is given in the Appendix

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