Transfusion Threshhold - Critical Hematocrit

5/26/2004

Question: What is the threshold or critical hematocrit at or below which a transfusion is required?

<1>

Unique Identifier:12901136

Authors: Davenport RD.

Institution: Department of Pathology, University Hospital 2G33/0054, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-0054, USA. rddvnprt@umich.edu

Title: The red blood cell transfusion threshold: evidence and outcome. [Review] [12 refs]

Source: Current Hematology Reports. 1(2):142-8, 2002 Nov.

Abstract: The appropriate threshold for administration of red blood cell transfusion is the subject of controversy. Recently, several prospective randomized clinical trials have compared restrictive and liberal transfusion regimens in the settings of critical care and surgery. In addition, several large cohort studies have provided information on associations between anemia, transfusion, and clinical outcomes. Taken together, these studies generally support conservative red blood cell transfusion strategies. [References: 12]

<2>

Unique Identifier:12076437

Authors: Hill SR. Carless PA. Henry DA. Carson JL. Hebert PC. McClelland DB. Henderson KM.

Institution: Clinical Pharmacology, University of Newcastle, Level 5 Clinical Sciences Building Newcastle Mater Hospital, Edith Street, Newcastle, New South Wales, Australia, 2298. hillsu@mail.newcastle.edu.au

Title: Transfusion thresholds and other strategies for guiding allogeneic red blood cell transfusion. [Review] [65 refs]

Source: Cochrane Database of Systematic Reviews. (2):CD002042, 2002.

Abstract: BACKGROUND: Most clinical practice guidelines recommend restrictive red cell transfusion practices with the goal of minimising exposure to allogeneic blood (from an unrelated donor). The purpose of this review is to compare clinical outcomes in patients randomised to restrictive versus liberal transfusion thresholds (triggers). OBJECTIVES: To examine the evidence on the effect of transfusion thresholds, on the use of allogeneic and/or autologous blood, and the evidence for any effect on clinical outcomes. SEARCH STRATEGY: Trials were identified by: computer searches of OVID Medline (1966 to December 2000), Current Contents (1993 to Week 48 2000), and the Cochrane Controlled Trials Register (2000 Issue 4). References in identified trials and review articles were checked and authors contacted to identify any additional studies. SELECTION CRITERIA: Controlled trials in which patients were randomised to an intervention group or to a control group. Trials were included where the intervention groups were assigned on the basis of a clear transfusion "trigger", described as a haemoglobin (Hb) or haematocrit (Hct) level below which a RBC transfusion was to be administered. DATA COLLECTION AND ANALYSIS: Trial quality was assessed using criteria proposed by Schulz et al. (1995). Relative risks of requiring allogeneic blood transfusion, transfused blood volumes and other clinical outcomes were pooled across trials using a random effects model. MAIN RESULTS: Ten trials were identified that reported outcomes for a total of 1780 patients. Restrictive transfusion strategies reduced the risk of receiving a red blood cell (RBC) transfusion by a relative 42% (RR=0.58: 95%CI=0.47,0.71). This equates to an average absolute risk reduction (ARR) of 40% (95%CI=24% to 56%). The volume of RBCs transfused was reduced on average by 0.93 units (95%CI=0.36,1.5 units). However, heterogeneity between these trials was statistically significant (p<0.00001) for these outcomes. Mortality, rates of cardiac events, morbidity, and length of hospital stay were unaffected. Trials were of poor methodological quality. REVIEWER'S CONCLUSIONS: The limited published evidence supports the use of restrictive transfusion triggers in patients who are free of serious cardiac disease. However, most of the data on clinical outcomes were generated by a single trial. The effects of conservative transfusion triggers on functional status, morbidity and mortality, particularly in patients with cardiac disease, need to be tested in further large clinical trials. In countries with inadequate screening of donor blood the data may constitute a stronger basis for avoiding transfusion with allogeneic red cells. [References: 65]

<3>

Unique Identifier:12075558

Authors: Carson JL. Hill S. Carless P. Hebert P. Henry D.

Institution: Division of General Internal Medicine, Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA.

Title: Transfusion triggers: a systematic review of the literature. [Review] [61 refs]

Source: Transfusion Medicine Reviews. 16(3):187-99, 2002 Jul.

Abstract: Most clinical practice guidelines recommend restrictive red blood cell (RBC) transfusion practices with the goal of minimizing transmission of blood-borne pathogens. The purpose of this review is to compare clinical outcomes in patients randomized to restrictive versus liberal transfusion thresholds (triggers). We conducted a search of OVID Medline, Current Contents, the Cochrane Library, and bibliographies of published studies. Our search strategies used a combination of key-word terms as text and MeSH headings relating to transfusion triggers. We included trials if the comparison groups were assigned on the basis of a clear transfusion trigger or threshold, and the study was randomized with a concurrent control group. Eligibility of studies was assessed by 2 independent raters, with disagreements resolved by consensus. Disagreements not resolved by consensus were referred to a third party for review. Two raters assessed the methodologic quality of the trials modified from the methods of Schultz. The main study outcomes probability of receiving an RBC transfusion, volume of RBCs transfused, hematocrit levels, mortality, and length of hospital stay. Ten trials, which reported outcomes for a total of 1,780 patients, were included. Five studies were in surgical patients, 3 were in the setting of acute blood loss and trauma, and 2 involved intensive care unit patients. Transfusion triggers varied between 7 and 10 g/dL (most often they were 8 or 9 g/dL). Being randomized to a restrictive transfusion trigger group had the following average effects: the probability of receiving an RBC transfusion was reduced by 42% (relative risk, 0.58; 95% confidence interval [CI] 0.47, 0.71), the volume of RBCs was reduced by 0.93 units (95% CI 0.36, 1.5 units), and hematocrit values were 5.6 % lower (95% CI 3.5, 7.7%). Mortality, rates of cardiac events, morbidity, and length of hospital stay were unaffected. The limited published evidence supports the use of restrictive transfusion triggers in patients who are free of serious cardiac disease. However, most of the data on clinical outcomes were generated by a single trial. The effects of conservative transfusion triggers on functional status, morbidity, and mortality, particularly in patients with cardiac disease, need to be tested in further large clinical trials. In countries with inadequate screening of donor blood, the data may constitute a stronger basis for avoiding transfusion with allogeneic RBCs. Copyright 2002, Elsevier Science (USA). All rights reserved. [References: 61]