Limitations of blood conservation

Restrictive Transfusion in Geriatric Trauma Patients

To determine whether a restrictive strategy of red cell transfusion was safe in elderly trauma patients, we compared those treated with a restrictive transfusion strategy versus those who were liberally transfused. We performed a retrospective study of elderly (age ≥ 70 years) trauma patients admitted to our Level I trauma center from 2005 to 2013. Patients with a hemoglobin (Hg) < 10 g/dL after 48 hours were included. We excluded patients with an Injury Severity Score > 25 or active cardiac ischemia. Patients who were transfused for an Hg < 10 g/dL (liberal group) were compared to those who were transfused for an Hg< 7 g/dL (restrictive group). There were 382 patients included, 229 and 153 in the liberal and restrictive transfusion groups, respectively. All patients in the liberal group and 20 per cent of patients in the restrictive group received a transfusion ( P < 0.0001). Patients in the liberal group had more overall complications (52 vs 32%, P = 0.0001). On multivariate analysis, receiving a transfusion was an independent risk factor to develop a complication [odds ratio = 2.3 (1.5–3.6), P < 0.0001]. For survivors, patients in the liberal group spent more days in the hospital (nine versus seven days, P = 0.007) and intensive care unit (two versus one day, P = 0.01). There was no difference in mortality (3 vs 4%, P = 0.82). In conclusion, restrictive transfusion appears to be safe in elderly trauma patients and may be associated with decreased complications and shortened length of stay.

Exploring mechanisms of excess mortality with early fluid resuscitation: insights from the FEAST trial

BACKGROUND

Early rapid fluid resuscitation (boluses) in African children with severe febrile illnesses increases the 48-hour mortality by 3.3% compared with controls (no bolus). We explored the effect of boluses on 48-hour all-cause mortality by clinical presentation at enrolment, hemodynamic changes over the first hour, and on different modes of death, according to terminal clinical events. We hypothesize that boluses may cause excess deaths from neurological or respiratory events relating to fluid overload.

METHODS

Pre-defined presentation syndromes (PS; severe acidosis or severe shock, respiratory, neurological) and predominant terminal clinical events (cardiovascular collapse, respiratory, neurological) were described by randomized arm (bolus versus control) in 3,141 severely ill febrile children with shock enrolled in the Fluid Expansion as Supportive Therapy (FEAST) trial. Landmark analyses were used to compare early mortality in treatment groups, conditional on changes in shock and hypoxia parameters. Competing risks methods were used to estimate cumulative incidence curves and sub-hazard ratios to compare treatment groups in terms of terminal clinical events.

RESULTS

Of 2,396 out of 3,141 (76%) classifiable participants, 1,647 (69%) had a severe metabolic acidosis or severe shock PS, 625 (26%) had a respiratory PS and 976 (41%) had a neurological PS, either alone or in combination. Mortality was greatest among children fulfilling criteria for all three PS (28% bolus, 21% control) and lowest for lone respiratory (2% bolus, 5% control) or neurological (3% bolus, 0% control) presentations. Excess mortality in bolus arms versus control was apparent for all three PS, including all their component features. By one hour, shock had resolved (responders) more frequently in bolus versus control groups (43% versus 32%, P <0.001), but excess mortality with boluses was evident in responders (relative risk 1.98, 95% confidence interval 0.94 to 4.17, P = 0.06) and 'non-responders' (relative risk 1.67, 95% confidence interval 1.23 to 2.28, P = 0.001), with no evidence of heterogeneity (P = 0.68). The major difference between bolus and control arms was the higher proportion of cardiogenic or shock terminal clinical events in bolus arms (n = 123; 4.6% versus 2.6%, P = 0.008) rather than respiratory (n = 61; 2.2% versus 1.3%, P = 0.09) or neurological (n = 63, 2.1% versus 1.8%, P = 0.6) terminal clinical events.

CONCLUSIONS

Excess mortality from boluses occurred in all subgroups of children. Contrary to expectation, cardiovascular collapse rather than fluid overload appeared to contribute most to excess deaths with rapid fluid resuscitation. These results should prompt a re-evaluation of evidence on fluid resuscitation for shock and a re-appraisal of the rate, composition and volume of resuscitation fluids.

TRIAL REGISTRATION

ISRCTN69856593.

[Erythrocyte transfusions: an evidence-based approach]

Few randomized controlled studies, the only trial design where causality can be established between an intervention and the benefits or harms thereof, have been published on the benefits and risks of a restrictive vs a liberal transfusion strategy. We review the 19 controlled studies on erythrocyte transfusion thresholds published since the eighties. These studies suggest that, overall, morbidity (including cardiac morbidity) and mortality, along with hemodynamic, respiratory and oxygen transport variables, are similar when a restrictive transfusion strategy (transfusion threshold between 7 and 8 g/dL) or a liberal strategy (transfusion threshold of 10 g/dL) are used. In fact, a restrictive strategy can even be associated with a number of benefits. The relevance of a higher transfusion threshold in view of avoiding morbidity in patients presenting a cardiovascular risk is unlikely, at least uncertain. Finally, anaemia has little or no impact on functional recovery and on quality of life, whether in the immediate or late postoperative period. It is clear that a restrictive strategy is associated with a reduced exposure to red cell transfusions, allowing a reduction in transfusion-related adverse events. Thus, all red cell transfusions must be tailored to the patient's needs, at the time the need prevails. In conclusion, most recommendations on transfusion practice are limited by the lack of evidence-based data and reveal our ignorance on the topic. High quality clinical trials in different patient populations must become available in order to determine optimal transfusion practices. Since then, a restrictive strategy aiming for a moderately anaemic threshold (7-8 g/dL) is appropriate under most circumstances.

Perioperative blood transfusion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and The Society of Cardiovascular Anesthesiologists clinical practice guideline

BACKGROUND

A minority of patients having cardiac procedures (15% to 20%) consume more than 80% of the blood products transfused at operation. Blood must be viewed as a scarce resource that carries risks and benefits. A careful review of available evidence can provide guidelines to allocate this valuable resource and improve patient outcomes.

METHODS

We reviewed all available published evidence related to blood conservation during cardiac operations, including randomized controlled trials, published observational information, and case reports. Conventional methods identified the level of evidence available for each of the blood conservation interventions. After considering the level of evidence, recommendations were made regarding each intervention using the American Heart Association/American College of Cardiology classification scheme.

RESULTS

Review of published reports identified a high-risk profile associated with increased postoperative blood transfusion. Six variables stand out as important indicators of risk: (1) advanced age, (2) low preoperative red blood cell volume (preoperative anemia or small body size), (3) preoperative antiplatelet or antithrombotic drugs, (4) reoperative or complex procedures, (5) emergency operations, and (6) noncardiac patient comorbidities. Careful review revealed preoperative and perioperative interventions that are likely to reduce bleeding and postoperative blood transfusion. Preoperative interventions that are likely to reduce blood transfusion include identification of high-risk patients who should receive all available preoperative and perioperative blood conservation interventions and limitation of antithrombotic drugs. Perioperative blood conservation interventions include use of antifibrinolytic drugs, selective use of off-pump coronary artery bypass graft surgery, routine use of a cell-saving device, and implementation of appropriate transfusion indications. An important intervention is application of a multimodality blood conservation program that is institution based, accepted by all health care providers, and that involves well thought out transfusion algorithms to guide transfusion decisions.

CONCLUSIONS

Based on available evidence, institution-specific protocols should screen for high-risk patients, as blood conservation interventions are likely to be most productive for this high-risk subset. Available evidence-based blood conservation techniques include (1) drugs that increase preoperative blood volume (eg, erythropoietin) or decrease postoperative bleeding (eg, antifibrinolytics), (2) devices that conserve blood (eg, intraoperative blood salvage and blood sparing interventions), (3) interventions that protect the patient's own blood from the stress of operation (eg, autologous predonation and normovolemic hemodilution), (4) consensus, institution-specific blood transfusion algorithms supplemented with point-of-care testing, and most importantly, (5) a multimodality approach to blood conservation combining all of the above.

Transfusion in the intensive care unit

BACKGROUND

Anemia is a common complication of critical illness. Because tissue hypoxia is a prominent factor in the development of organ dysfunction in the critically ill, conventional wisdom has argued that the transfusion of packed red blood cells can attenuate tissue hypoxia and so improve outcome.

METHODS

Review of pertinent English-language literature.

RESULTS

The empiric evidence supporting the benefit of transfusion to treat tissue hypoxia is sparse; indeed, a body of recent work suggests that moderate anemia is not only well-tolerated by the critically ill patient, it is associated with improved clinical outcomes. The primary biologic rationale for transfusion of the critically ill is to maximize oxygen delivery to tissues. However, because of reflex compensatory mechanisms, and because of alterations in microvascular flow and endothelial permeability, the impact of transfusion is much less than would be predicted. Retrospective studies suggest that transfusion is immunosuppressive, and associated with an enhanced infectious risk. The large Transfusion Requirements in Critical Care (TRICC) Trial conducted by the Canadian Critical Care Trials Group demonstrated reduced mortality and organ dysfunction when a transfusion trigger of 7 g/dL is used, without an increase in infectious complications.

CONCLUSIONS

A conservative transfusion strategy appears safe in nearly all critically ill patients without active hemorrhage, including patients with cardiovascular disease. Whether a lower transfusion threshold could be adopted is unknown.

Current status of transfusion triggers for red blood cell concentrates

Clinical practice guidelines on red blood cell transfusion (RBC) are based on expert opinion, animal studies and the few human trials available. Twelve randomized controlled trials on the benefits of RBC transfusions in humans have been published. In the absence of definitive outcome studies, numerous theoretical arguments have been put forward in favor or against the classic transfusion threshold of 100 g/l. However, data from randomized controlled trials suggest that overall morbidity (including cardiac) and mortality, hemodynamic, pulmonary and oxygen transport variables are not different between restrictive (transfusion threshold between 70 and 80 g/l) and liberal transfusion strategies and that a restrictive transfusion strategy is not associated with increased adverse outcomes. In fact, a restrictive strategy may be associated with decreased adverse outcomes in younger and less sick critical care patients. The majority of existing guidelines conclude that transfusion is rarely indicated when the hemoglobin concentration is greater than 100 g/l and is almost always indicated when it falls below a threshold of 60 g/l in healthy, stable patients or more in older, sicker patients. In anesthetized patients, this threshold should be modulated by factors related to the dynamic nature of surgery such as uncontrolled hemorrhage, microvascular bleeding, etc. Another important role of RBC relates to primary hemostasis and higher triggers may be appropriate in coagulopathic patients. RBC concentrates are administered to correct inadequate oxygen delivery and/or to sustain primary hemostasis. Reliable monitors of tissue oxygenation and hemostasis will be required to study the benefits (or lack thereof) of RBC transfusions. The quest for a universal transfusion trigger, i.e., one that would be applicable to patients of all ages under all circumstances, must be abandoned. All RBC transfusions must be tailored to the patient's needs, at the moment the need arises. In conclusion published recommendations are commensurate with existing knowledge and, unfortunately, their conclusions are limited. Future research and development should focus on the determination of optimal transfusion strategies in various patient populations and on reliable monitors to guide transfusion therapy.

The effect of perioperative anemia on clinical and functional outcomes in patients with hip fracture

OBJECTIVES

To describe the epidemiology of perioperative anemia in patients with hip fracture and assess the relationship between the hemoglobin measurements and clinical outcomes.

DESIGN

Prospective observational cohort study.

SETTING

Four university and community teaching hospitals.

PATIENTS

A consecutive cohort of 550 patients who underwent surgery for hip fracture and survived to discharge from August 1997 and August 1998 were evaluated and followed prospectively.

MAIN OUTCOME MEASURES

Deaths, readmissions and Functional Independence Motor mobility scores within 60 days of discharge.

RESULTS

Anemia (defined as hemoglobin <12.0 g/dL) was present in 40.4% of patients on admission, 45.6% at the presurgery nadir, 93.0% at the postsurgery nadir, and 84.6% near discharge. The mean drop in hemoglobin after surgery was 2.8 +/- 1.6 g/dL. In multivariate analyses, higher hemoglobin levels on admission were associated with shorter lengths of hospital stay and lower odds of death and readmission even after controlling for a broad range of prefracture patient characteristics, clinical status on discharge, and use of blood transfusion. Admission and preoperative anemia was not associated with risk-adjusted Functional Independence Motor mobility scores. In multivariable analyses, higher postoperative hemoglobin was associated with shorter length of stay and lower readmission rates, but did not effect rates of death or Functional Independence Motor mobility scores.

CONCLUSIONS

Substantial declines in hemoglobin were common in patients with hip fracture. Higher preoperative hemoglobin was associated with shorter length of stay and lower odds of death and readmission within 60 days of discharge. Postoperative hemoglobin was also related to length of stay and readmission rates.

Effects of blood transfusion on clinical and functional outcomes in patients with hip fracture

BACKGROUND

Anemia and transfusion are common among elderly patients requiring surgery. The effects of transfusion on morbidity and mortality are controversial. The influence of transfusion on risk-adjusted mortality, readmissions, and functional mobility was examined.

STUDY DESIGN AND METHODS

A consecutive cohort of 551 patients undergoing surgery for hip fracture at four hospitals was prospectively studied. Outcomes were death, readmission, and functional independence measure-locomotion scores within 60 days of discharge. The trigger Hb level was defined as the lowest value before the first postoperative transfusion. Multivariate analyses adjusted for a validated, hip-fracture-specific risk model and predictors of transfusion.

RESULTS

Overall, 54.4 percent of patients received transfusions after surgery. Seventy-two percent of patients with a lowest postoperative Hb level of less than 10.0 g per dL received transfusions compared to 19.6 percent of those whose lowest measurement was at least 10.0 g per dL (p < 0.0001). In the 60 days after discharge, 3.8 percent of patients died and 16.9 percent were readmitted. Transfusion was associated with lower risk-adjusted odds of readmission (OR, 0.54; 95% CI, 0.30-0.97), but it did not influence mortality or mobility functioning. In subgroups analyses, the benefit of transfusion on readmission rates appeared to be concentrated among patients with a trigger Hb level of less than 10.0 g per dL. For patients with a trigger Hb level of at least 10.0 g per dL, transfusion did not affect risk-adjusted rates of death or readmission, but was associated with better risk-adjusted functional mobility scores (p < 0.01).

CONCLUSIONS

Postoperative transfusion reduced the risk of readmission but did not decrease mortality or improve mobility. Randomized controlled trials of different transfusion strategies will be needed to clarify the true benefits and risks of transfusion in surgical patients.

Red cell transfusion "trigger": a review

Despite the publication of several consensus guidelines that set forth recommendations for the transfusion of red cells, actual clinical practice continues to vary widely. Animal data and studies in human volunteers and patients support a red cell transfusion threshold of 7 to 8 g/dl in most patients. However, conflicting data, particularly in cardiac patients and in the elderly, suggest that it may be impossible to define a single red cell "trigger" for all patients. A well-designed, randomized, controlled trial is still needed to establish a safe threshold for red cell transfusion in adults with coronary artery disease.

New mathematical model for the correct prediction of the exchangeable blood volume during acute normovolemic hemodilution

BACKGROUND

The blood volume that has to be exchanged for crystalloids and/or colloids during acute normovolemic hemodilution (ANH) in order to reach a preset target hemoglobin concentration (hb) is usually predicted by the Bourke and Smith formula developed in 1974. This formula systematically overestimates the 'true' exchangeable blood volume (EBV), a fact that may potentially endanger patients because the target hb will be missed and the normovolemic anemia might turn out to be more severe than a priori intended. Our objective was to develop a more accurate mathematical model of hemodilution kinetics and to validate this new model in animals and in patients undergoing ANH.

METHODS

Twenty-two anesthetized beagle dogs and 18 patients under balanced anesthesia underwent isovolemic hemodilution with hydroxyethyl starch (HAES 6%, 200 000) to a target hb of 7 g dl-1 or 9 g dl-1, respectively. Exchangeable blood volume predicted by use of the different mathematical models was compared with the blood volume actually exchanged to meet the preset target hb.

RESULTS

Calculation of EBV by the Bourke and Smith formula (EBVB + S) systematically overestimated the volume actually exchanged (overestimation: dogs 15%, patients 20%), whereas our new iterative model predicted EBV (EBViterative) more reliably (overestimation: dogs 1%, patients 8%). In both cases EBVB + S differed significantly from the EBViterative.

CONCLUSION

Exchangeable blood volume is predicted more accurately by the new iterative model than by the Bourke and Smith formula. The iterative model leads to an improvement in patient safety and provides a physiologically adequate basis for future studies investigating the efficacy of ANH in reducing allogenic blood transfusions.

Transfusion triggers for blood components

Whereas there are general guidelines for acceptable transfusion therapy, optimal transfusion therapy has not been determined for most clinical settings. Recent research has focused on controlled studies of red cell transfusion in specific clinical settings. Better determinations of oxygen delivery and consumption are needed to guide clinicians in determining whether transfusion is justified for patients during the perioperative period, those with coronary artery disease, and those in intensive care units. For sickle cell disease, the role of transfusion for acute complications can be life saving; however, the role of chronic transfusion regimens awaits further research into efficacy. Finally, whereas criteria for the prophylactic transfusion of platelets in hematologic diseases are well described, relatively little information is available on the value of platelet transfusion where the absolute count is less than 100,000 but greater than 50,000. The value of fresh frozen plasma components, both standard and sterilized, also requires elucidation.

Is a low transfusion threshold safe in critically ill patients with cardiovascular diseases?

OBJECTIVE

To compare a restrictive red blood cell transfusion strategy with a more liberal strategy in volume-resuscitated critically ill patients with cardiovascular disease.

SETTING

Twenty-two academic and three community critical care units across Canada.

STUDY DESIGN

Randomized controlled clinical trial.

STUDY POPULATION

Three hundred fifty-seven critically ill patients with cardiovascular diseases from the Transfusion Requirements in Critical Care trial who had a hemoglobin concentration of <90 g/L within 72 hrs of admission to the intensive care unit.

INTERVENTIONS

Patients were randomized to a restrictive strategy to receive allogeneic red blood cell transfusions at a hemoglobin concentration of 70 g/L (and maintained between 70 and 90 g/L) or a liberal strategy to receive red blood cells at 100 g/L (and maintained between 100 and 120 g/L).

RESULTS

Baseline characteristics in the restrictive (n = 160) and the liberal group (n = 197) were comparable, except for the use of cardiac and anesthetic drugs (p <.02). Average hemoglobin concentrations (85 +/- 6.2 vs. 103 +/- 6.7 g/L; p <.01) and red blood cell units transfused (2.4 +/- 4.1 vs. 5.2 +/- 5.0 red blood cell units; p <.01) were significantly lower in the restrictive compared with the liberal group. Overall, all mortality rates were similar in both study groups, including 30-day (23% vs. 23%; p = 1.00), 60-day, hospital, and intensive care unit rates. Changes in multiple organ dysfunction from baseline scores were significantly less in the restrictive transfusion group overall (0.2 +/- 4.2 vs. 1.3 +/- 4.4; p =.02). In the 257 patients with severe ischemic heart disease, there were no statistically significant differences in all survival measures, but this is the only subgroup where the restrictive group had lower but nonsignificant absolute survival rates compared with the patients in the liberal group.

CONCLUSION

A restrictive red blood cell transfusion strategy generally appears to be safe in most critically ill patients with cardiovascular disease, with the possible exception of patients with acute myocardial infarcts and unstable angina.

Hematologic management of gastrointestinal bleeding

The hematologic management of gastrointestinal (GI) bleeding requires evaluation of the underlying cause of bleeding, associated diseases that can exacerbate the bleeding, and identification of related and unrelated coagulation abnormalities. Erythrocyte transfusions are given to increase oxygen carrying capacity; however, there is limited information on the level of anemia that places a patient at increased risk of adverse events after a GI bleed and when patients should receive erythrocyte transfusion. Isolated thrombocytopenia is uncommon in patients with GI bleeding, and there is little evidence documenting the degree of thrombocytopenia associated with an increased risk of bleeding. Platelets are often administered when the count is 50,000 per cu/mL in a bleeding patient. The coagulopathy of liver disease is the most common abnormality seen in the setting of GI bleeding. Fresh-frozen plasma (FFP) should be given in a dose equivalent to the underlying abnormality and the common practice of administering 2 units of FFP is often insufficient in a bleeding patient.

Important role of nondiagnostic blood loss and blunted erythropoietic response in the anemia of medical intensive care patients

OBJECTIVE

To determine incidence, severity, characteristics, and causes of anemia and transfusion requirements in medical intensive care patients.

DESIGN AND SETTING

Open prospective clinical study in a 24-bed medical intensive care unit in a tertiary-care university hospital.

PATIENTS

Patients (N = 96) treated in the intensive care unit for >3 days.

INTERVENTIONS

None.

MEASUREMENTS

Parameters of erythropoiesis and red blood cell metabolism, including hemoglobin, reticulocyte counts, serum iron, transferrin, ferritin, haptoglobin, vitamin B12, folic acid, and erythropoietin concentrations were determined serially. Diagnostic blood loss and red blood cell transfusions were recorded, and the total blood loss was estimated from changes in hemoglobin concentrations and the amount of hemoglobin transfused.

MAIN RESULTS

The median hemoglobin concentration was 12.1 g/dL at admission and 11.2 g/dL at the end of the intensive care unit stay. A total of 74 patients (77%) suffered from anemia and received 257 red blood cell units, approximately half of which were given within the first 5 days. Three patients who received 19 red blood cell units were admitted with acute gastrointestinal bleeding, but in the remainder, a median total blood loss of 128 mL/d was not (n = 60) or not solely (n = 11) a result of overt bleeding. Diagnostic blood loss declined from a median of 41 mL on day 1 to <20 mL after 3 wks and contributed 17% (median) to total blood loss. Acute renal failure, fatal outcome, and simplified acute physiology score >38 on admission were associated with a 5.8-, 7.0-, and 2.8-fold increase in total blood loss. Reticulocyte counts and erythropoietin concentrations were inappropriately low for the degree of anemia, and plasma transferrin saturation was mostly <20%.

CONCLUSIONS

Anemia is frequent and results in a high requirement for red blood cell transfusions in the medical intensive care setting. A major proportion of blood loss is not caused by overt bleeding or diagnostic blood sampling but, rather, may result from various other reasons, e.g., occult gastrointestinal bleeding and renal replacement therapy. The erythropoietic response to anemia is blunted, probably as a consequence of an inappropriate increase in erythropoietin production and diminished iron availability. (Crit Care Med 1999; 27:2630-2639)

The effect of postoperative normovolaemic anaemia and autotransfusion on blood saving after internal mammary artery bypass surgery

The efficacy of two blood conservation techniques in decreasing and in preventing the use of homologous blood products was retrospectively studied in 150 patients undergoing internal mammary artery bypass surgery. Patients were matched according to prebypass blood haemoglobin (Hb) content and body surface area and were allocated to one of three groups: in the patients of group 1 (n = 50), normovolaemic anaemia (NA) was accepted postoperatively (haematocrit [Hct] was accepted to a minimum level of 25%); the patients of group 2 (n = 50) were treated with postoperative autotransfusion (AT) of mediastinal shed blood and acceptance of NA. Group 3 (n = 50) contained control patients, not treated with NA or with AT (Hct was accepted to a minimum level of 30%). Patients of group 1 required 3.0 +/- 0.3 units of homologous blood products, but the patients of groups 2 and 3 received significantly more (p less than 0.01) units: 3.9 +/- 0.2 and 4.5 +/- 0.3 units. No donor blood products were needed in 36%, 9% and 5% of the patients in groups 1, 2 and 3 respectively. The net postoperative blood loss was similar in the groups: 1229 +/- 92 ml in group 1, 1098 +/- 74 ml in group 2 and 1243 +/- 72 ml in group 3. However, total blood loss (1982 +/- 135 ml), including the retransfused part (954 +/- 89 ml), was significantly larger (p less than 0.01) in group 2, than in groups 1 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group

BACKGROUND

To determine whether a restrictive strategy of red-cell transfusion and a liberal strategy produced equivalent results in critically ill patients, we compared the rates of death from all causes at 30 days and the severity of organ dysfunction.

METHODS

We enrolled 838 critically ill patients with euvolemia after initial treatment who had hemoglobin concentrations of less than 9.0 g per deciliter within 72 hours after admission to the intensive care unit and randomly assigned 418 patients to a restrictive strategy of transfusion, in which red cells were transfused if the hemoglobin concentration dropped below 7.0 g per deciliter and hemoglobin concentrations were maintained at 7.0 to 9.0 g per deciliter, and 420 patients to a liberal strategy, in which transfusions were given when the hemoglobin concentration fell below 10.0 g per deciliter and hemoglobin concentrations were maintained at 10.0 to 12.0 g per deciliter.

RESULTS

Overall, 30-day mortality was similar in the two groups (18.7 percent vs. 23.3 percent, P= 0.11). However, the rates were significantly lower with the restrictive transfusion strategy among patients who were less acutely ill -- those with an Acute Physiology and Chronic Health Evaluation II score of < or =20 (8.7 percent in the restrictive-strategy group and 16.1 percent in the liberal-strategy group; P=0.03) -- and among patients who were less than 55 years of age (5.7 percent and 13.0 percent, respectively; P=0.02), but not among patients with clinically significant cardiac disease (20.5 percent and 22.9 percent, respectively; P=0.69). The mortality rate during hospitalization was significantly lower in the restrictive-strategy group (22.3 percent vs. 28.1 percent, P=0.05).

CONCLUSIONS

A restrictive strategy of red-cell transfusion is at least as effective as and possibly superior to a liberal transfusion strategy in critically ill patients, with the possible exception of patients with acute myocardial infarction and unstable angina.

In search of the transfusion trigger

Red blood cell transfusions are used commonly in orthopaedic surgery and cost billions of dollars annually. The goals of transfusion are to reduce mortality and morbidity and improve functional status that result from anemia and inadequate O2 delivery. Risks of infections from transfusion are low and continue to decline, but evidence is growing that red cell transfusions are immunosuppressive and predispose patients to postoperative infections. However, there actually are very little data on when transfusion is indicated. Observational data suggest that transfusion does not reduce mortality in patients with preoperative or postoperative hemoglobin levels 8 g/dL or greater, although no conclusions could be drawn about the effect of transfusion in patients with hemoglobin 8 g/dL or less. Large, well performed randomized clinical trials are needed to establish the efficacy of transfusion. Until better data are available, orthopaedic surgeons will have to rely on clinical judgement in decisions regarding transfusions. Using a higher transfusion threshold in patients with cardiovascular disease is recommended.

Perioperative red cell transfusion: evidence, guidelines and practice

Although we still do not know enough about the influence of anaemia and transfusion on outcomes for the surgical patient, it is possible to develop a general consensus about many aspects of management. A quality programme to improve consistency of practice in these consensus areas is feasible. (Table 6) This should be linked with further randomised trials to evaluate the clinical effectiveness of alternative regimes.

A Canadian survey of transfusion practices in critically ill patients. Transfusion Requirements in Critical Care Investigators and the Canadian Critical Care Trials Group

OBJECTIVES

To characterize the contemporary red cell transfusion practice in the critically ill and to define clinical factors that influence these practices.

DESIGN

Scenario-based national survey.

STUDY POPULATION

Canadian critical care practitioners.

MEASUREMENTS AND MAIN RESULTS

We evaluated transfusion thresholds before transfusion and the number of red cell units ordered, under the given conditions. Of 254 Canadian critical care physicians, 193 (76%) responded to the survey. The primary specialty of most respondents was internal medicine (56%). Internal medicine respondents were in practice for an average of 8.4 +/- 5.7 (SD) yrs, and worked most often in combined medical/surgical intensive care units. Baseline hemoglobin transfusion thresholds averaged from 8.3 +/- 1.0 g/dL in a scenario involving a young stable trauma victim to 9.5 +/- 1.0 g/dL for an older patient after gastrointestinal bleeding. Transfusion thresholds differed significantly (p< .0001) between all four separate scenarios. With the exception of congestive heart failure (p> .05), all clinical factors (including age, Acute Physiology and Chronic Health Evaluation II score, preoperative status, hypoxemia, shock, lactic acidosis, coronary ischemia, and chronic anemia) significantly (p< .0001) modified the transfusion thresholds. A statistically significant (p< .01) difference in baseline transfusion thresholds was noted across four major regions (with a maximum of five academic centers per region) of the country. Low physician numbers in two of the regions did not allow for further investigation of regional variations.

CONCLUSIONS

There is significant variation in critical care transfusion practice, with many intensivists adhering to a 10.0-g/dL threshold, while other physicians described a much more restrictive approach to red cell transfusion. Also, many physicians opted to administer multiple units, despite published guidelines to the contrary. Additionally, the administration of red cells was strongly influenced by a number of clinical factors, many unique to intensive care unit patients. There is a need for prospective studies to define optimal practice in the critically ill.

Current red blood cell transfusion practices

The appropriate use of blood transfusions remains variable among health-care institutions and patient populations. Transfusion practices are discussed in this article in relation to medical practice guidelines and utilization review. Specific transfusion practices in the settings of intensive care, orthopedic surgery, and open heart surgery are reviewed. A new, promising approach to improving transfusion outcomes is the use of transfusion algorithms. Transfusion algorithms may prove especially useful if they incorporate point-of-care testing that is both physiologic and patient-specific for transfusion decisions. Transfusion algorithms are discussed and data presented for cardiac surgical adults.

Establishing practice guidelines for surgical blood management

Medical practice guidelines have been promoted as a way to improve the cost-effectiveness of medical care. Algorithms for the transfusion of red blood cells, plasma, and platelets may be especially useful in the surgical setting if they incorporate point-of-care information that is both physiologic and patient-specific for transfusion decision making. Therefore, the goals of guidelines for surgical blood management should be twofold. They should (1) acknowledge patient-specific variability while addressing physician- and institution-dependent variables; and (2) improve blood component management by developing more physiologic clinical indicators of the need for allogeneic red blood cell transfusion.

On the need for improved transfusion indicators in cardiac surgery

Guidelines for transfusion practice have had limited impact in altering physician transfusion behavior in patients undergoing cardiac operations. This may be due to a lack of consensus on the relative risks and benefits of blood in these patients who are anemic, limited access to timely data that are necessary on which to base transfusion decisions, the recognition that empiric hemoglobin/hematocrit thresholds are limited clinical indicators of the need for blood, or a combination of these. We present an overview of current transfusion and blood conservation practices in this setting, along with possible approaches to guide the decision-making process by coupling the use of transfusion algorithms with point of care testing to use more physiologic indicators of the need for blood transfusion.

Does hemoglobin concentration affect perioperative myocardial lactate flux in patients undergoing coronary artery bypass surgery?

Increasing concern over complications related to blood transfusions has prompted a reevaluation of what constitutes an "adequate" perioperative hemoglobin concentration, particularly in patients undergoing coronary artery bypass graft (CABG) surgery. Data from 224 patients with preserved ventricular function (ejection fraction > 50%), undergoing CABG surgery, previously studied under a variety of anesthetic protocols, were reexamined to determine the effect of hemoglobin (HGB) concentration on myocardial lactate flux (MLF) (as an index of ischemia). The interaction of MLF and HGB concentration, anesthetic technique (ANES), and hemodynamic variables (including systemic and pulmonary arterial pressures (SAP and PAP), cardiac output (CO), and myocardial oxygen consumption (MVO2) was determined from a pool of 1598 data sets obtained from 224 patients. Data were collected from just prior to induction of anesthesia until 24 h postoperatively. Univariate analysis revealed a statistically significant relationship between MLF and HGB concentration (P < 0.001) but the correlation coefficient was only 0.09. Multiple regression analysis did not determine HGB concentration to be a significant independent term affecting MLF in either the overall group or in a subgroup of 22 patients having an adverse outcome (myocardial infarction, stroke, or death). For patients undergoing CABG surgery, HGB concentrations within the range of 58-172 g/L were not a significant variable in production of global myocardial ischemia as evidenced by MLF. This suggests that HGB concentrations as low as 60-70 g/L in the perioperative period are well tolerated and are not associated with an increased incidence of myocardial ischemia.

Safety and therapeutic effectiveness of reinfused shed blood after open heart surgery

This prospective study was designed to determine whether use of nonwashed shed mediastinal blood exacerbated platelet and related hematologic dysfunctions after cardiopulmonary bypass, compared with the alternative use of autologous and homologous standard liquid preserved blood for volume support. Thirty-two patients undergoing cardiopulmonary bypass for open heart operations were randomized to receive either nonwashed shed mediastinal blood (group 1; n = 16) or liquid preserved packed red blood cells (group 2; n = 16) for transfusion therapy in the management of postoperative bleeding. Patient blood samples and bleeding times were obtained preoperatively, after cardiopulmonary bypass but before transfusions, 2 and 24 hours after transfusion, and on postoperative days 2, 3, and 7. Group 1 patients received an average of 710 +/- 90 mL (range, 300 to 1,700 mL) of nonwashed shed mediastinal blood containing significantly greater (p < 0.0001) amounts of fibrin degradation products and D-dimer protein. Of the hematologic, microaggregate, and plasma protein measurements performed, only the protein C level was significantly greater in group 1 (p < 0.05) after transfusion. Patient bleeding times were not significantly different between the groups at any of the time points, and the total postoperative blood loss was not different between the groups. There was a trend toward less need for homologous transfusion in group 1 (p < 0.1). This study documents the safety and ease of using nonwashed shed mediastinal blood as a primary blood volume support after an open heart operation.

Transfusion and surgery

In this survey of transfusion in surgery, we have attempted to provide the surgeon with an understanding of the problems associated with homologous transfusion and a practical knowledge of treatment strategies and alternatives designed to reduce homologous blood exposure. Such a review cannot be encyclopedic. Our hope is that it will serve the reader as a stimulus to examine his or her transfusion practices and as a guide for future self-learning.

Intraoperative predonation contributes to blood saving

The merits of reinfusing prebypass-removed autologous blood (intraoperative predonation) to salvage blood and improve postoperative hemostasis are still debated, specifically for patients at a higher risk for bleeding. To evaluate the effect of intraoperative predonation on the platelet count, blood hemoglobin content, and blood saving postoperatively, we retrospectively studied 100 matching patients. All patients underwent internal mammary artery bypass surgery resulting in a considerable blood loss postoperatively. Intraoperative predonation (800 ml), reinfusion of the residual volume of the extracorporeal circuit, autotransfusion of shed blood, and acceptance of normovolemic anemia postoperatively was the approach adopted in 50 patients (group 1). A similar blood salvage program, excluding intraoperative predonation, was carried out in the other 50 patients (group 2), and these served as the control group. The platelet counts and blood hemoglobin content were significantly higher postoperatively (p < 0.01) in the predonated patients than in the control patients. However, the net blood loss, the amount of retransfused shed blood, and the blood requirements postoperatively were significantly less (p < 0.01) in the predonated patients than in the control patients, whereas 65% of the predonated patients versus 10% of the control patients did not need any donor blood products. In conclusion, predonation reduces the postoperative blood loss and thereby importantly ameliorates the blood-saving effect of a blood salvage program after IMA procedures.