Experience with sodium fluorescein flow cytometry in the determination of red cell volume.

Sodium fluorescein flow cytometry for the calculation of red cell volume is an exciting proposition in that the repeatability of the technique in a short time frame should allow for applications such as the measurement of surgical red cell volume loss. Our results found that the rapid decay in fluorescence negated the usefulness of this technique as currently described. However, further investigation into the behaviour of the sodium fluorescein labelled red blood cells may allow for the mathematical correction of the fluorescent red cell population prior to red cell volume calculation.

Rationalizing blood transfusion in cardiac surgery: the impact of a red cell volume-based guideline on blood usage and clinical outcome.

BACKGROUND AND OBJECTIVES: Cardiac surgery is currently considered one of the heaviest users of red blood cells. An explanation may be found, in part, in considering the effect of the heavy clear fluid load associated with cardiopulmonary bypass. This may result in the artificial depression of haemoglobin concentration, overestimating the requirement for red cell transfusion if this is the sole parameter considered. To address this issue, we examined the impact of a red cell volume-based transfusion guideline on transfusion requirement. MATERIALS AND METHODS: This was a single-centre, randomized controlled trial. The cohort of 86 patients was allocated to receive red cells as per the red cell volume guideline (group RCV) or standard haemoglobin concentration-based departmental policy (group C). Outcome measures were red cell transfusion and clinical outcome. RESULTS: All preoperative data were comparable between the two groups. A significantly fewer percentage of patients in group RCV were transfused red cells (RCV = 32.6% vs. C = 53.5%, P = 0.05). No significant difference was found between any of the outcome measures with the exception of median hospital stay (RCV = 5.9 days vs. C = 6.8 days, P = 0.02). CONCLUSION: In elective cardiac surgery patients, considering haemoglobin concentration alone may overestimate the requirement for red cell transfusion. More research is required to determine the impact of restrictive transfusion policies on clinical outcome following cardiac surgery.

Prevalence of anaemia before major joint arthroplasty and the potential impact of preoperative investigation and correction on perioperative blood transfusions.

BACKGROUND: Preoperative investigation and treatment of anaemia is recommended before orthopaedic surgery. We measured the prevalence of anaemia among admissions presenting for elective major joint arthroplasty (MJA), assessed their transfusion requirements, and investigated factors associated with perioperative blood transfusion. METHODS: All admissions to a dedicated elective orthopaedic hospital during 2000-2001 were studied. The patients' database was merged with the haematology and transfusion databases. Population estimates for different types of anaemia and their blood transfusion requirements were generated using local reference ranges (males <130 g litre(-1); females <115 g litre(-1)). RESULTS: One thousand three hundred and twenty-two admissions were included; haematology data were complete for 1142 (544 primary hip, 490 primary knee, 77 revision hip, 31 revision knee). About 19.6% were anaemic [7.1% haemoglobin (Hb) <110 g litre(-1); 1.6% Hb<100 g litre(-1)]. Overall, 21.3% of admissions were transfused (mean 0.58 units per case: 95% CI 0.50-0.61). For anaemic admissions, 42.0% were transfused (mean 1.11 units per case: 95% CI 0.90-1.32). Mean red cell use for admissions with normocytic normochromic anaemia (12.7% of admissions) and hypochromic anaemia (4.6%) was 1.04 (95% CI 0.78-1.31) and 1.14 (95% CI 0.71-1.57) units per admission, respectively. Factors strongly associated independently with transfusion were preoperative haemoglobin

Rationalizing blood transfusion in cardiac surgery: preliminary findings with a red cell volume-based model.

BACKGROUND AND OBJECTIVES: Cardiac surgery, utilizing extracorporeal circulation, is associated with a heavy fluid load that may significantly depress haemoglobin concentration. Thus, considering haemoglobin alone may be an inaccurate method of replacing red cell volume loss. This study was designed to examine the impact on red cell transfusion of a red cell volume-based guideline. MATERIALS AND METHODS: Patients were randomized to receive red cells as dictated by the red cell volume-based guideline or a haemoglobin-based protocol. End-points considered were red cell transfusion and clinical outcome. RESULTS: Patients transfused as per the red cell volume-based guideline received significantly less red cells with no associated difference in clinical outcome. CONCLUSION: Considering haemoglobin concentration alone may significantly overestimate the requirement for red cell transfusion in elective cardiac surgery patients.

The EU optimal blood use project.

The EU optimal blood use project (EUOBUP) is co-funded by the European Commission and led by the Scottish National Blood Transfusion Service (SNBTS). Its purpose is to develop, evaluate and disseminate a manual that provides practical guidance and support for those seeking to improve the safety of the clinical transfusion process and the effectiveness of the prescribing of blood components. We define the optimal use of blood components as the safe, clinically effective and efficient use of the scarce resource of donated human blood. The project will build on the experience of a pilot project in optimal use of blood in the national health service in Scotland. This pilot developed training resources in the safe and effective use of blood and delivered training to a large number of practitioners. It has also developed systems to provide hospitals with comparative information on their use of blood components for specific clinical groups of patients to assist them in reviewing practice against that of their peers.

Factors predicting loss and gain of red cell volume in cardiac surgery patients.

Haemoglobin may be a poor indicator of changes in red cell volume (RCV) because of factors such as haemodilution. This study has been designed to analyse what peri-operative variables may be associated with loss or gain in RCV due to bleeding or transfusion. Prospective observational study. Single centre study based in a regional cardiac surgery centre. Twenty-nine elective adult cardiac surgery patients. Loss and gain of RCV were measured in theatre and for the first 24 h post-operatively. Patient and operative factors analysed were age, sex, height, weight, body surface area (BSA), induction haematocrit (Hct), estimated pre-operative RCV and antiplatelet therapy taken less than 7 days before operation, cardiopulmonary bypass (CPB) time, aortic occlusion time, minimum and maximum CPB temperatures and fluid administered. Age, sex, height, weight, BSA and induction Hct were found to predict red cell transfusion but not RCV loss. The total number of red cells transfused was significantly associated with RCV lost when expressed as a percentage reduction in the estimated pre-operative RCV but not the absolute RCV lost. Pre-operative RCV, as predicted by the variables outlined above, is more important than RCV lost in triggering red cell transfusion.

Appraisal of the evidence for the clinical use of FFP and plasma fractions.

Randomised, controlled trials of good quality are a recognised means to robustly assess the efficacy of interventions in clinical practice. A systematic identification and appraisal of all randomised trials involving fresh frozen plasma (FFP) indicates that most clinical indications for FFP, as currently recommended by practice guidelines, are not supported by evidence from randomised trials. This chapter will largely consider the implications of some of the findings from this systematic review. Many published trials on the use of FFP have enrolled small numbers of patients, and provided inadequate information on the ability of the trial to detect meaningful differences in outcomes between the two patient groups. Other concerns about the design of the trials include the dose of FFP used, and the potential for bias; no studies had taken adequate account of the extent to which adverse effects might negate the clinical benefits of treatment with FFP. In addition, there is little evidence for the effectiveness of the prophylactic use of FFP. There is a pressing need to consider how best to develop new trials to determine the effectiveness of FFP. How this can be achieved can be illustrated by reference to studies of albumin in critical care. A recent, large and well-designed randomised trial (Saline versus Albumin Fluid Evaluation study; SAFE) in critical care found no evidence of an increase in mortality with the use of albumin compared to saline, which had been hypothesised in an earlier systematic review. How the study findings will actually now influence the clinical use of albumin remains to be seen. Although the SAFE trial showed no increase in mortality with albumin compared with saline, it is difficult to justify its use in critical care given its considerably greater cost.

Is fresh frozen plasma clinically effective? A systematic review of randomized controlled trials.

Summary Randomized controlled trials of good quality are a recognized means to robustly assess the efficacy of interventions in clinical practice. A systematic identification and appraisal of all randomized trials involving fresh frozen plasma (FFP) has been undertaken in parallel to the drafting of the updated British Committee for Standards in Haematology guidelines on the use of FFP. A total of 57 trials met the criteria for inclusion in the review. Most clinical uses of FFP, currently recommended by practice guidelines, are not supported by evidence from randomized trials. In particular, there is little evidence for the effectiveness of the prophylactic use of FFP. Many published trials on the use of FFP have enrolled small numbers of patients, and provided inadequate information on the ability of the trial to detect meaningful differences in outcomes between the two patient groups. Other concerns about the design of the trials include the dose of FFP used, and the potential for bias. No studies have taken adequate account of the extent to which adverse effects might negate the clinical benefits of treatment with FFP. There is a need to consider how best to develop new trials to determine the efficacy of FFP in different clinical scenarios to provide the evidence base to support national guidelines for transfusion practice. Trials of modified FFP (e.g. pathogen inactivated) are of questionable value when there is little evidence that the standard product is an effective treatment.

Anaemia and red blood cell transfusion in the critically ill patient.

Anaemia is a common finding in critically ill patients. There are often multiple causes. Obvious causes include surgical bleeding and gastrointestinal haemorrhage but many patients have no overt bleeding episodes. Phlebotomy can be a significant source of blood loss. In addition, critically ill patients have impaired erythropoiesis as a consequence of blunted erythropoietin production and direct inhibitory effects of inflammatory cytokines. The ability of a patient to tolerate anaemia depends on their clinical condition and the presence of any significant co-morbidity; maintenance of circulating volume is of paramount importance. There is no universal transfusion trigger. Current guidelines for critically ill and perioperative patients advise that at Hb values <70 g/L red blood cell transfusion is strongly indicated and at Hb values >100 g/L transfusion is unjustified. For patients with Hb values in the range 70 to 100 g/L the transfusion trigger should be based on clinical indicators. Most stable critically ill patients can probably be managed with a Hb concentration between 70 and 90 g/L. Uncertainties exist concerning the most appropriate Hb concentration for patients with significant cardio-respiratory disease.

Red cell transfusion practice following the transfusion requirements in critical care (TRICC) study: prospective observational cohort study in a large UK intensive care unit.

BACKGROUND AND OBJECTIVES: The Transfusion Requirements In Critical Care (TRICC) study found that critically ill patients tolerate a restrictive haemoglobin transfusion threshold. We investigated red-cell transfusion practice since publication of the TRICC study in a large Scottish teaching hospital intensive care unit (ICU). MATERIALS AND METHODS: We prospectively collected daily data for a 6-month period on haemoglobin concentrations, red-cell transfusions and indications for transfusions, throughout ICU stay for all patients who stayed for longer than 24 h in the ICU. RESULTS: A total of 176 patients were studied, who utilized 1237 ICU days. Of these 176 patients, 52% received red-cell transfusions. A haemoglobin concentration of < or = 9 g/dl was measured in 55% of patients; this occurred by day 1 and day 2 in 52% and 77% of these cases, respectively. Overall the haemoglobin concentration was < or = 9 g/dl for 45% of all patient days. Total red-cell use was 3.1 units per admission (0.47 units per patient day). Only 18% of transfusion episodes were required as a result of haemorrhage. For 'non-haemorrhage' transfusion episodes, the median pretransfusion haemoglobin concentration was 7.8 g/dl (interquartile range: 7.4-8.4 g/dl), and 64% of transfusion episodes were for 2 units. CONCLUSIONS: Clinicians in our centre were conservative, in keeping with recent transfusion guidelines, but deviated from the TRICC protocol by transfusing at haemoglobin concentrations of between 7 and 9 g/dl, rather than below 7 g/dl, and by prescribing 2 unit transfusions. Significant numbers of red-cell units are still used in the critically ill.