Graded coronary stenosis and coronary flow during acute normovolemic anemia

Six-month mortality and cardiac catheterization in non-ST-segment elevation myocardial infarction patients with anemia

BACKGROUND

It is unknown how anemia influences the invasive management of patients with non-ST-segment elevation myocardial infarction (NSTEMI) and associated mortality. We investigated whether receipt of cardiac catheterization relates to 6-month death rates among patients with different severity of anemia.

METHODS

We used data from the population-based Worcester Heart Attack Study, which included 2634 patients hospitalized with confirmed NSTEMI, from three percutaneous coronary intervention-capable medical centers in the Worcester (Massachusetts, U.S.A.) metropolitan area, during five biennial periods between 1997 and 2005. Severity of anemia was categorized using admission hematocrit levels: less than or equal to 30.0% (moderate-to-severe anemia), 30.1-39.0% (mild anemia), and more than 39.0% (no anemia). Propensity matching and conditional logistic regression adjusting for hospital use of aspirin, heparin, and plavix compared 6-month postadmission all-cause mortality rates in relation to cardiac catheterization during NSTEMI hospitalization.

RESULTS

Compared with patients without anemia, patients with anemia were less likely to undergo cardiac catheterization {adjusted odds ratio (AOR) 0.79 [95% confidence interval (CI): 0.67-0.95] for mild anemia and 0.45 (95% CI: 0.42-0.49) for moderate-to-severe anemia}. After propensity matching, cardiac catheterization was associated with lower 6-month death rates only in patients without anemia [AOR 0.26 (95% CI: 0.09-0.79)] but not in patients with mild anemia [AOR 0.55 (95% CI: 0.25-1.23)]. The small number of patients rendered data inconclusive for patients with moderate-to-severe anemia.

CONCLUSION

Anemia at the time of hospitalization for NSTEMI was associated with lower utilization of cardiac catheterization. However, cardiac catheterization use was associated with a decreased risk of dying at 6 months after hospital admission only in patients without anemia.

[Perioperative management of Jehovah's Witness patients. Special consideration of religiously motivated refusal of allogeneic blood transfusion]

The religious organization of Jehovah's Witnesses numbers more than 7 million members worldwide, including 165,000 members in Germany. Although Jehovah's Witnesses strictly refuse the transfusion of allogeneic red blood cells, platelets and plasma, Jehovah's Witness patients may nevertheless benefit from modern therapeutic concepts including major surgical procedures without facing an excessive risk of death. The present review describes the perioperative management of surgical Jehovah's Witness patients aiming to prevent fatal anemia and coagulopathy. The cornerstones of this concept are 1) education of the patient about blood conservation techniques generally accepted by Jehovah's Witnesses, 2) preoperative optimization of the cardiopulmonary status and correction of preoperative anemia and coagulopathy, 3) perioperative collection of autologous blood, 4) minimization of perioperative blood loss and 5) utilization of the organism's natural anemia tolerance and its acute accentuation in the case of life-threatening anemia.

Red blood cell transfusion in the treatment and management of anaemia: the search for the elusive transfusion trigger

Therapeutic red blood cell (RBC) transfusion is widely utilized in the management of anaemia. Critically ill intensive care unit (ICU) patients in particular, as well as medical and haematology-oncology patients, are among the largest groups of users of RBC products. While anaemia is common in these patients, its treatment and management, including appropriate thresholds for RBC transfusion, remain controversial. We review here the function of RBCs in oxygen transport and physiology, with a view to their role in supporting and maintaining systemic tissue oxygenation. Adaptive and physiological compensatory mechanisms in the setting of anaemia are discussed, along with the limits of compensation. Finally, data from clinical studies will be examined in search of evidence for, or against, a clinically relevant transfusion trigger.

[Tolerance to perioperative anemia. Mechanisms, influencing factors and limits]

Die zu erwartende Kostensteigerung im Transfusionswesen (steigender Fremdblutbedarf bei gleichzeitig rückläufiger Spendebereitschaft, Behandlungspflicht transfusionsassoziierter Folgeerkrankungen) erhöht den sozioökonomischen Stellenwert der Entwicklung institutionsspezifischer Transfusionsprogramme. Ein wesentlicher Bestandteil hierbei ist – neben einer schonenden Operationstechnik und der konsequenten perioperativen Anwendung fremdblutsparender Maßnahmen – die Ausschöpfung der natürlicherweise vorhandenen „Anämietoleranz“ des menschlichen Organismus (Toleranz größerer Blutverluste durch Verlust von „verdünntem“ Blut, Hinauszögern des Transfusionsbeginns bis nach chirurgischer Blutstillung, Gewinnung von autologem Blut). In der vorliegenden Übersicht werden die Mechanismen, Einflussgrößen und Grenzen dieser natürlichen Anämietoleranz für den Gesamtorganismus und für einzelne Organsysteme zusammengefasst und die sich daraus ergebende Indikation zur Erythrozytentransfusion abgeleitet. Unter kontrollierten Bedingungen (Narkose, strikte Aufrechterhaltung von Normovolämie, komplette Muskelrelaxierung, Hyperoxämie, Hypothermie) werden von kardiopulmonal gesunden Individuen kurzzeitig auch extreme Grade der Verdünnungsanämie [Hämoglobin- (Hb-)Wert <3 g/dl (<1,86 mmol/l)] ohne Transfusion toleriert. In der klinischen Routine bleibt diese Situation – nicht zuletzt in Ermangelung eines adäquaten Monitorings – jedoch auf spezielle Sonderfälle beschränkt (z. B. unerwartete große Blutverluste bei Zeugen Jehovahs, unerwarteter Engpass bei der Bereitstellung von Fremdblut). Die derzeit geltenden Empfehlungen verschiedener Expertenkommissionen decken sich dahingehend, dass perioperativ (1) bis zu einer Hb-Konzentration von 10 g/dl (6,21 mmol/l) auch bei alten Patienten und Patienten mit kardiopulmonalen Begleiterkrankungen eine Transfusion von Erythrozyten in der Regel nicht notwendig ist und (2) eine Transfusion bei jungen, gesunden Patienten ohne kardiopulmonale Vorerkrankungen (einschließlich Schwangeren und Kindern) erst ab einer Hb-Konzentration von <6 g/dl (<3,72 mmol/l) notwendig wird. Auch beatmete Intensivpatienten mit Polytrauma und Sepsis scheinen nicht von einer Transfusion auf Hb-Konzentration >9 g/dl (>5,59 mmol/l) zu profitieren. Bei massiven Blutverlusten und diffuser Blutungsneigung scheint ein Hb von 10 g/dl (6,21 mmol/l) zur Stabilisierung der Blutgerinnung beizutragen.

[Tolerance to perioperative anemia. Mechanisms, influencing factors and limits]

Die zu erwartende Kostensteigerung im Transfusionswesen erhöht den sozioökonomischen Stellenwert der Entwicklung institutionsspezifischer Transfusionsprogramme. Ein wesentlicher Bestandteil hierbei ist – neben einer schonenden Operationstechnik und der konsequenten perioperativen Anwendung fremdblutsparender Maßnahmen – die Ausschöpfung der natürlichen „Anämietoleranz“ des menschlichen Organismus. Im vorliegenden Beitrag werden die Mechanismen, Einflussgrößen und Grenzen dieser Anämietoleranz für den Gesamtorganismus und für einzelne Organsysteme zusammengefasst und die sich daraus ergebende Indikation zur Erythrozytentransfusion abgeleitet. Die derzeit geltenden Empfehlungen decken sich dahingehend, dass bis zu einer Hämoglobinkonzentration von 10 g/dl (6,21 mmol/l) auch bei alten Patienten oder kardiopulmonalen Begleiterkrankungen eine perioperative Transfusion in der Regel nicht notwendig ist und bei jungen, gesunden Patienten ohne kardiopulmonale Vorerkrankungen (einschließlich Schwangeren und Kindern) erst ab <6 g/dl (<3,72 mmol/l) notwendig wird. Auch beatmete Intensivpatienten mit Polytrauma und Sepsis scheinen nicht von einer Transfusion auf eine Hämoglobinkonzentration >9 g/dl (>5,59 mmol/l) zu profitieren. Bei massiven Blutverlusten und diffuser Blutungsneigung scheint ein Wert von 10 g/dl (6,21 mmol/l) zur Stabilisierung der Blutgerinnung beizutragen.

Anaemia and the heart

Anaemia is common in patients with congestive heart failure (CHF). Its prevalence increases with disease severity as a consequence of renal insufficiency, cytokine production, blood loss, iron deficiency, malnutrition and/or plasma volume overload. Anaemia can contribute to worsening of CHF. There is a nonlinear relationship (U-shaped curve) between haemoglobin and survival. Prevalence of anaemia among elderly people with acute myocardial infarction is high and is associated with more frequent in-hospital events, including death. Anaemia is also associated with higher in-hospital mortality rate after coronary bypass surgery and with all-cause and cardiac mortality after percutaneous coronary interventions. Patients with anaemia and cardiovascular disease have a higher mortality rate after cardiac/noncardiac surgery as compared to those with anaemia but without cardiovascular disease or those with cardiovascular disease but without anaemia. However, not all authors confirmed these findings. Therefore, multicentre trials to clarify this issue are urgently needed. Pleiotropic effects of recombinant human erythropoietin include reduction of myocardial and cerebral infarct size without an increase in haematocrit, neovascularization as well as mobilization of endothelial progenitor cells.

Acute Normovolemic Hemodilution

This article examines the technique of hemodilution and the consequences, benefits, efficacy, cost effectiveness, and future of acute normovolemic hemodilution.

Physiologic aspects of anemia

The most important adaptive responses from a physiological stance involved the cardiovascular system, consisting in particular of elevation of the cardiac output and its redistribution to favor the coronary and cerebral circulations, at the expense of the splanchnic vascular beds. The evidence regarding these physiological responses, especially in experimental studies that permit the control of many variables, is particularly powerful and convincing. On the other hand, there is a remarkable lack, in quality and quantity, of clinical studies addressing how normal physiological adaptive responses may be affected by a variety of diseases and conditions that often accompany and may complicate anemia, and interactions with other such compounding variables as age and different patient populations. For these reasons, it is not possible to offer guidelines on how to increase, maintain, or even to determine optimal DO2 in high-risk patients and how best transfusion strategies might be used under these conditions. From the brief review of physiological principles and the strong consensus in the literature, it is evident that cardiac function must be a central consideration in decisions regarding transfusion in anemia, because of the critical role it plays in assuring adequate oxygen supply of all vital tissues. Particular attention should be paid to the possible presence of CAD or incipient or cardiac failure, as these conditions may require careful transfusions to improve DO2 at levels that may not necessitate such interventions when cardiac disease is absent. Although the cerebral circulation also serves an obligate aerobic organ unable to tolerate significant hypoxia, there is little convincing evidence to support the notion that cerebral ischemia is aggravated by anemia and that this can be prevented by improved DO2 through rapid correction of anemia. Consequently, the arguments favoring transfusions in the presence of ischemic heart disease do not appear to apply to occlusive cerebrovascular disease. Because firm evidence is lacking on the interactions of concurrent diseases and anemia in various patient populations, understanding of the physiological consequences of anemia, and of the diseases concerned, is useful but not fully sufficient to provide firm and rational guidance to transfusion practice in specific complex clinical instances. A good deal of clinical and experimental investigation is required to support fully rational and comprehensive guidelines. In the meantime, prudent and conservative management, based on awareness of risks and sound understanding of the normal and pathological physiology, must remain the guiding principle.

Anemia in the critically ill

The anemia of critical illness is a distinct clinical entity with characteristics similar to that of chronic disease anemia. Several solutions to the processes of anemia, such as blunted erythropoietin production and erythropoietin response and abnormalities in iron metabolism have been developed. The transfusion of RBCs provides immediate correction of low hemoglobin levels, which may be of value in patients with life-threatening anemia. Avoidance of RBC and blood component transfusion, however, is becoming increasingly important as data of adverse clinical outcomes in critically ill patients become clearer. Although the optimal hemoglobin in critically ill patients is not determined, this organ system has a generous reserve. Short-term compensated anemia is tolerated well, while exogenous erythropoietin allows patients to achieve higher hemoglobin concentrations without exposure to transfused blood/blood components. A recent randomized trial enrolled over 1300 critically ill patients to receive either 40,000 units of exogenous erythropoietin or placebo. These authors found that patients randomized to erythropoietin received significantly less allogeneic RBC transfusions and had significantly greater increases in hemoglobin. Although no differences were found between groups in gross clinical outcomes (ie, death, renal failure, myocardial infarction), this study did not have the power to identify small differences in outcomes. This and other studies of exogenous erythropoietin therapy in critically ill patients clearly demonstrate that the bone marrow in many of these patients will respond to the administration of erythropoietin despite their illness, suggesting a blunted production of erythropoietin rather than a blunted response to erythropoietin. Exogenous erythropoietin therefore represents a therapeutic option for treating anemia in critical illness. Acute events in medicine and surgery often lead to many patients becoming anemic. Solutions to this process of anemia should be focused on preventing such events. Anemia after surgery represents an area for prevention. Blood conservation strategies can be performed with adequate results. Monk et al randomized 79 patients undergoing radical prostatectomy to preoperative autologous donation (PAD), preoperative exogenous erythropoietin therapy plus ANH immediately following induction of general anesthesia, and ANH alone. This study concluded that all three techniques resulted in similar hemostasis outcomes (eg, bleeding and transfusion rates), but ANH alone was the least expensive, and ANH plus exogenous erythropoietin and ANH alone resulted in a higher ICU hematocrit compared with PAD. Regardless of these prophylactic strategies, patients still become anemic after surgery or during critical illness. This acute event anemia usually is treated with RBC transfusion; however, autologous blood recovery (cell salvage systems) has been shown to be effective in patients with acute bleeding-related anemia, and this may reduce patients' exposure to allogeneic blood in these patients. There are no universally accepted treatment guidelines for managing anemia, and practice differs between clinicians, hospitals, regions, and countries. Transfusion medicine is evolving and incorporating many new pharmacological agents into the armamentarium of anemia and bleeding therapy. Accumulating evidence suggests that anemia in critically ill patients is common and correlated with poor outcomes. The management of anemia can improve outcomes; however, the optimal management of anemia is not performed universally. New approaches, continued research, and an understanding of anemia may result in more consistent and improved outcomes for critically ill patients.

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 "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.

Effect of anemia on 1-year mortality in patients with acute myocardial infarction

BACKGROUND

Limited data are available on the effect of anemia on mortality in patients with acute myocardial infarction (MI).

METHODS

We examined the association of anemia with mortality at 1 year among 30,341 patients hospitalized with acute MI in 1986 (prethrombolytic era, n = 15,584) and 1996 (thrombolytic era, n = 14,757). The records were obtained from the Myocardial Infarction Data Acquisition System, a database of all patients with MI admitted to nonfederal hospitals in New Jersey.

RESULTS

Anemia was present in 996 patients (6.4%) in 1986 and 1510 patients (10.2%, P <.0001) in 1996. In both years, patients with anemia were older, more frequently female and nonwhite, and more likely to have left ventricular dysfunction, non-Q MI and coronary artery bypass graft. In addition, in 1996, patients with anemia were more likely to undergo percutaneous transluminal coronary angioplasty and less likely to have a history of MI. One-year mortality was lower overall in 1996 compared with 1986 (1996 23.6%, 95% CI 22.9-24.3 vs 1986 24.9%, 95% CI 24.2-25.6, P =.0001). In both years, patients with anemia had significantly higher unadjusted risk for 1-year mortality (RR = 1.40, P =.0001 in both years). However, after controlling for demographics, left ventricular dysfunction, arrhythmias, Q versus non-Q MI, comorbid conditions, and revascularization procedures in a multivariable regression model, 1-year mortality in the anemia group was similar to the nonanemia group in both years.

CONCLUSION

In the Myocardial Infarction Data Acquisition System database, anemia appears to have no significant direct effect on 1-year mortality. The higher unadjusted mortality observed among patients with acute MI and anemia is probably the result of older age, higher comorbidity, and more left ventricular dysfunction.

Blood transfusion in elderly patients with acute myocardial infarction

BACKGROUND

Anemia may have adverse effects in patients with coronary artery disease. However, the benefit of blood transfusion in elderly patients with acute myocardial infarction and various degrees of anemia is uncertain.

METHODS

We conducted a retrospective study of data on 78,974 Medicare beneficiaries 65 years old or older who were hospitalized with acute myocardial infarction. Patients were categorized according to the hematocrit on admission (5.0 to 24.0 percent, 24.1 to 27.0 percent, 27.1 to 30.0 percent, 30.1 to 33.0 percent, 33.1 to 36.0 percent, 36.1 to 39.0 percent, or 39.1 to 48.0 percent), and data were evaluated to determine whether there was an association between the use of transfusion and 30-day mortality.

RESULTS

Patients with lower hematocrit values on admission had higher 30-day mortality rates. Blood transfusion was associated with a reduction in 30-day mortality among patients whose hematocrit on admission fell into the categories ranging from 5.0 to 24.0 percent (adjusted odds ratio, 0.22; 95 percent confidence interval, 0.11 to 0.45) to 30.1 to 33.0 percent (adjusted odds ratio, 0.69; 95 percent confidence interval, 0.53 to 0.89). It was not associated with a reduction in 30-day mortality among those whose hematocrit values fell in the higher ranges. In one of seven subgroup analyses (among patients who survived at least two days), transfusion was not associated with a reduction in mortality for patients with hematocrit values of 30.1 percent or higher.

CONCLUSIONS

Blood transfusion is associated with a lower short-term mortality rate among elderly patients with acute myocardial infarction if the hematocrit on admission is 30.0 percent or lower and may be effective in patients with a hematocrit as high as 33.0 percent on admission.

Debate: transfusing to normal haemoglobin levels will not improve outcome

Recent evidence suggests that critically ill patients are able to tolerate lower levels of haemoglobin than was previously believed. It is our goal to show that transfusing to a level of 100 g/l does not improve mortality and other clinically important outcomes in a critical care setting. Although many questions remain, many laboratory and clinical studies, including a recent randomized controlled trial (RCT), have established that transfusing to normal haemoglobin concentrations does not improve organ failure and mortality in the critically ill patient. In addition, a restrictive transfusion strategy will reduce exposure to allogeneic transfusions, result in more efficient use of red blood cells (RBCs), save blood overall, and decrease health care costs.

Anemia in the patient undergoing surgery and the transfusion decision. A review

The heightened awareness of the problems of transfusion reactions, disease transmission, and potential immunosuppression has led surgeons to reevaluate their reasons for transfusion. Current practice policies recommend that elective transfusion of allogeneic blood be avoided whenever possible in patients having surgery. If patients are to have appropriate transfusion, the basic pathophysiology and clinical response of the patient to anemia must be understood. This article reviews the physiologic response to anemia in the patient having surgery and explores the components of the decision to use transfusion.

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.

A prospective, randomized trial limiting perioperative red blood cell transfusions in vascular patients

BACKGROUND

Patients undergoing major arterial reconstruction have traditionally been transfused with red blood cells to keep hemoglobin concentrations above 10 g/dL in order to prevent anemia-induced myocardial ischemia. There are no data to support this practice. The hypothesis that vascular patients will tolerate a hemoglobin concentration of 9 g/dL was examined.

METHODS

Ninety-nine patients undergoing elective aortic and infrainguinal arterial reconstructions were prospectively randomized preoperatively to receive transfusions to maintain a hemoglobin level of either 10 g/dL or 9 g/dL.

RESULTS

Despite significantly different postoperative hemoglobin levels of 11.0 +/- 1.2 versus 9.8 +/- 1.3 g/dL (P <0.0001), there were no differences in mortality or cardiac morbidity rates or length of hospital stay. There were no differences in hemodynamic parameters. Oxygen delivery was lower in the group with lower hemoglobin levels, but there was no difference in O2 consumption between the groups.

CONCLUSIONS

A lower hemoglobin concentration was tolerated without adverse clinical outcome. Patients did not compensate for anemia by increased myocardial work, but by increasing O2 extraction in the peripheral tissues.

Limited intentional normovolemic hemodilution: ST-segment changes and use of homologous blood products in patients with left main coronary artery stenosis

OBJECTIVE

To assess and compare the effects of limited intentional normovolemic hemodilution (LINH) on ST-segment changes and to evaluate the need for homologous blood products.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PARTICIPANTS

Seventy-one patients with left main stenosis scheduled for semi-urgent coronary artery bypass grafting.

INTERVENTIONS

Patients in group A (n = 39) underwent LINH during the prebypass period until a hematocrit of 34% was obtained. Simultaneously, succinyl-linked gelatin was infused. In group B (n = 32), no hemodilution was performed. Mean arterial pressure and central venous pressure were kept as constant as possible. During the postbypass period, autologous blood was retransfused. The need for homologous blood products was noted intraoperatively and postoperatively.

MEASUREMENTS AND MAIN RESULTS

ST-segment analysis of lead II and chest lead was continuously performed in all patients. An ST-segment change was defined as a decrease from baseline of 1.0 mm (-0.1 mV). The appearance and degree of ST-segment depression were comparable in both groups (group A: 7 patients -0.1 mV, 1 patient -0.2 mV; group B: 5 patients -0.1 mV; 3 patients -0.2 mV). In group A, ST-segment depression occurred during and after the blood exchange. However, the mean duration of the ST-segment depression (group A: 33 +/- 18 minutes; group B: 20 +/- 10 minutes) was comparable between groups. In group A, a mean of 750 mL +/- 245 mL of blood was obtained. Total blood loss was significantly higher in group B (p < 0.052); 25 patients in group A (64%) and 12 patients in group B (38%) did not require homologous blood products (p < 0.03). Intraoperatively, only the need for packed red cells was greater in group B (p < 0.04). Postoperatively, the use of homologous blood products is higher than intraoperatively (p < 0.02).

CONCLUSIONS

LINH performed in patients with left main stenosis, scheduled for semi-urgent coronary bypass, is not associated with increases in frequency, degree, or duration of ST-segment changes. This procedure allowed a reduction in the number of patients who received homologous blood products.

Effect of anaemia and cardiovascular disease on surgical mortality and morbidity

BACKGROUND

Guidelines have been offered on haemoglobin thresholds for blood transfusion in surgical patients. However, good evidence is lacking on the haemoglobin concentrations at which the risk of death or serious morbidity begins to rise and at which transfusion is indicated.

METHODS

A retrospective cohort study was performed in 1958 patients, 18 years and older, who underwent surgery and declined blood transfusion for religious reasons. The primary outcome was 30-day mortality and the secondary outcome was 30-day mortality or in-hospital 30-day morbidity. Cardiovascular disease was defined as a history of angina, myocardial infarction, congestive heart failure, or peripheral vascular disease.

FINDINGS

The 30-day mortality was 3.2% (95% CI 2.4-4.0). The mortality was 1.3% (0.8-2.0) in patients with preoperative haemoglobin 12 g/dL or greater and 33.3% (18.6-51.0) in patients with preoperative haemoglobin less than 6 g/dL. The increase in risk of death associated with low preoperative haemoglobin was more pronounced in patients with cardiovascular disease than in patients without (interaction p < 0.03). The effect of blood loss on mortality was larger in patients with low preoperative haemoglobin than in those with a higher preoperative haemoglobin (interaction p < 0.001). The results were similar in analyses of postoperative haemoglobin and 30-day mortality or in-hospital morbidity.

INTERPRETATION

A low preoperative haemoglobin or a substantial operative blood loss increases the risk of death or serious morbidity more in patients with cardiovascular disease than in those without. Decisions about transfusion should take account of cardiovascular status and operative blood loss as well as the haemoglobin concentration.

Morbidity risk assessment in the surgically anemic patient

Clinicians have few data on which to base a decision to transfuse a surgical patient. We reviewed animal and human data to evaluate the effects that anemia and comorbidity have on surgical outcome. Experimental evidence consistently demonstrates increased cardiac output, decreased peripheral vascular resistance, and increased release of oxygen by red blood cells in response to anemia. Normal animals tolerate hemoglobin (Hb) levels down to approximately 5 g/dL. Below this level, cardiac ischemia and decreased ventricular function develop. In animals with experimental coronary artery stenosis, cardiac ischemia develops at Hb levels of 7-10 g/dL. Coexisting left ventricular hypertrophy, use of beta blockers, and hypoxemia also reduce animals' ability to tolerate anemia. The limited information on anemia tolerance of human surgical patients suggests that the presence of cardiac and pulmonary disease should influence transfusion decisions. A higher Hb threshold should be used in patients who have or are at risk of cardiac or pulmonary artery disease.

Blood conservation strategies to minimize allogeneic blood use in urologic surgery

Analysis of the net costs, efficacy, and cost-effectiveness of preoperative autologous blood donation (PAD), versus acute normovolemic hemodilution (ANH), in patients undergoing radical prostatectomy is presented. Currently, PAD is a standard of care for patients undergoing radical prostatectomy. Comparison of PAD with ANH showed no differences in risks or outcome, but ANH was less expensive. Hemodilution is a simple, safe, convenient, and effective alternative to PAD. The use of recombinant human erthropoietin in conjunction with PAD and ANH has optimized perioperative hematocrits and further minimized exposure to allogeneic blood. Intraoperative blood salvage, lower transfusion triggers, and other blood conservation strategies are discussed. The most cost-effective techniques currently available for decreasing allogeneic blood transfusions appear to be avoidance of blood loss, increased tolerance for decreased HCT levels, and autologous blood procurement via ANH.

Difficulties in demonstrating efficacy of blood substitutes

Currently, the fear of infectious disease transmission by allogenic blood transfusions has spurred interest in developing a blood substitute FDA approval requires that a sponsor demonstrate that the substitute is effective. The challenge in designing efficacy studies in man is proving that the substitute offers significant advantages over conventional therapies for acute blood loss. This task is complicated by the oxygen reserve and the response to hemodilution following treatment of acute blood loss in man. Paradoxically, the technique that relies on these protective physiologies-isovolemic perioperative hemodilution-many offer the best experimental model to establish efficacy of a blood substitute in man.

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.

Is a hemoglobin of 10 g/dL required for surgery?

The "10/30" (hemoglobin/hematocrit) rule has long been recognized and accepted in the medical community as the threshold for transfusion in the perioperative setting. However, an increasing number of publications suggest there is no absolute threshold for transfusion, and that this decision should be based on an assessment of the overall clinical picture presented by the patient. This article reviews the risks associated with blood transfusions, and the data in humans and animals that describe the benefits of transfusion. Recommendations on the trigger for red cell transfusion are provided.

Perioperative haemotherapy: I. Indications for blood component transfusion

The practice of transfusion medicine has undergone substantial change over the last decade. Much of the impetus for the change has come from the isolation of human immunodeficiency virus (HIV) and the linkage of HIV transmission to blood transfusion. The purpose of this paper is to collate and review the literature relating to the indications for blood transfusion and provide recommendations for the appropriate utilization of blood products. Peer-reviewed and published studies and reviews relating to aspects of clinical blood transfusion were identified through computer searches and searching of the bibliographies of identified articles. Emphasis was placed on the literature published within the last decade and particularly in the years 1985-91. Material was chosen which was of proved clinical importance and in which findings were consistent among different investigators or different centres. Less emphasis was placed on material reporting new findings of uncertain clinical relevance or findings that were not consistent with majority reports. It is concluded that the only indication for red cell transfusion is to increase the oxygen carrying capacity of the blood and that an adjustment downwards in the haemoglobin concentration at which blood is transfused (transfusion trigger) from the traditional level of 100 g.L-1 is supported by the physiological and clinical data. Perioperative haemoglobin concentrations of 80 g.L-1 are acceptable in otherwise healthy young patients. The transfusion trigger should be adjusted upwards from this in medically compromised patients and in the elderly (greater than 60 yr). Fresh frozen plasma (FFP) is only indicated when there are documented deficiencies of coagulation factors. Platelet concentrates (PC) are indicated for the treatment of clinical coagulopathy resulting from thrombocytopaenia or platelet dysfunction. Routine or prophylactic administration of either FFP or PC after cardiopulmonary bypass or during resuscitation from haemorrhage is not indicated.

Effect of a reduction in blood viscosity on maximal myocardial oxygen delivery distal to a moderate coronary stenosis

This study tested the hypothesis that a reduction in blood viscosity by means of isovolumetric hemodilution will permit an increase in maximal oxygen delivery to myocardium distal to a moderate coronary arterial stenosis. It is known that blood viscosity is a determinant of resistance to blood flow at both the stenotic and the arteriolar levels. Accordingly, a reduction in blood viscosity could exert a favorable influence on maximal myocardial oxygen delivery in the setting of stenosis, provided that the oxygen-carrying capacity of the blood is not compromised excessively. Closed-chest, sedated domestic swine (n = 8) were instrumented with an artificial coronary arterial stenosis that reduced vessel diameter by 64%. Measurements of hemodynamics, regional myocardial blood flow (microspheres), lactate and oxygen metabolism, and whole blood viscosity were made at control and after two successive 10 min intracoronary infusions of adenosine (400 and 800 micrograms/min) distal to the stenosis. Next, albumin/saline solution was given intravenously to reduce the animal's hematocrit by approximately 50%. Repeat measurements of all experimental variables were then made at a second control and again after two successive 10 min intracoronary infusions of adenosine (400 and 800 micrograms/min) distal to the stenosis. Myocardial blood flow (ml/min/g) distal to the stenosis increased from 1.52 +/- 0.21 (mean +/- 1 SD) to 4.10 +/- 0.86 in response to adenosine (peak dose) before hemodilution (p less than .01) and from 2.07 +/- 0.59 to 4.08 +/- 0.93 (p less than .01) after hemodilution.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of isovolemic hemodilution on abdominal aortic aneurysmectomy in high risk patients

Intraoperative isovolemic hemodilution might increase blood flow and tissue oxygenation in the periphery but there is concern that acute anemia may have deleterious effects on myocardium in patients with coronary artery disease. This study investigates the effects of intraoperative isovolemic hemodilution on morbidity, mortality and hemodynamics in 32 patients with significant cardiovascular disease undergoing elective abdominal aortic aneurysmectomy. The average hematocrit was lowered intraoperatively from 43% to 31% by withdrawing blood and replacing volumes with 1:3 Ringer's lactate. In ten patients myocardial function was evaluated during aortic cross-clamping and declamping in the face of hemodilution. There were two deaths: one myocardial infarction and one multiple organ failure. Aortic cross clamping did not change heart rate, vascular pressures (VP), vascular resistance (SVR), cardiac output (CO), and left ventricular stroke work (LVSW). Following declamping, VP, CO and LVSW decreased and SVR increased momentarily (p less than 0.05), but the myocardial function did not change. Isovolemic hemodilution had no apparent adverse effects on morbidity, mortality and cardiovascular performance in these patients.