Assessment of cardiac index in anemic patients

Effects of red blood cell transfusion on global oxygenation in anemic critically ill patients

BACKGROUND

Consensus for transfusion in intensive care unit (ICU) patients recommends a restrictive strategy, based on a hemoglobin (Hb) concentration of 7 g/dL. Red blood cell (RBC) transfusion is used to prevent tissue hypoxia by improving oxygen transport (DO₂ ) and therefore oxygen consumption (VO₂ ). We studied the effects of RBC transfusion on systemic oxygenation parameters reflecting systemic oxygen extraction (EO₂ = DO₂ /VO₂ ): S(c)vO₂ , lactate level, venous-to-arterial carbon dioxide difference (Pv-aCO₂ ), and cardiac index/EO₂ (CI/EO₂ ) and evaluated their usefulness in guiding transfusion decisions in ICU patients.

STUDY DESIGN AND METHODS

Prospectively, all adult patients transfused were included except those with active bleeding or without a jugular or subclavian catheter. We measured O₂ parameters before and after transfusion. Patients were a priori grouped according to their initial S(c)vO₂ (< or ≥70%), treatment with vasopressors, cardiac function, and septic status.

RESULTS

A total of 62 patients received 105 RBC transfusions. For all, mean arterial pressure (77 [69-88] to 81 [73-91] mm Hg), Hb concentration (7.4 [7.0-7.8] to 8.4 [7.7-8.9] g/dL) and S(c)vO₂ (65% [59%-73%] to 69% [62%-75%]) increased after transfusion (all P < .001). S(c)vO₂ improved after transfusion only when initial S(c)vO₂ was less than 70% (62% [56%-65%] to 66% [61%-71%]; P < .001). In this group, Pv-aCO₂ , lactate concentrations, and CI/EO₂ did not change after transfusion. Cardiac function, sepsis, or vasopressor therapy did not affect these results.

CONCLUSIONS

Among systemic O₂ parameters, only a S(c)vO₂ < 70% in anemic ICU patients improves after transfusion. As S(c)vO₂ can reflect a DO₂ /VO₂ imbalance, it could be helpful when combined with the Hb concentration to decide whether to transfuse. However, the benefit on outcome should be further studied.

Systematic Review and Meta-Analysis of Effects of Transfusion on Hemodynamic and Oxygenation Variables

OBJECTIVES

RBC transfusions can increase oxygen availability to the tissues, but studies have provided conflicting results. The objectives of this study were, therefore, to evaluate, using systematic review and meta-analysis, the effects of transfusion on hemodynamic/oxygenation variables in patients without acute bleeding.

DATA SOURCES

PubMed, Scopus, Cochrane Database of Systematic Reviews, and Embase from inception until June 30, 2019.

STUDY SELECTION

All articles that reported values of prespecified hemodynamic or oxygenation variables before and after RBC transfusion.

DATA EXTRACTION

Publication year, number of patients, number of transfusions and the type of population studied, hemodynamic and oxygenation data (heart rate, cardiac index, mixed venous oxygen saturation or central venous oxygen saturation, oxygen delivery index, oxygen consumption index, oxygen extraction ratio, arteriovenous oxygen difference and arterial blood lactate) before and after transfusion. We performed a meta-analysis for each variable for which there were sufficient data to estimate mean differences. We also performed subgroup analyses comparing septic with nonseptic patients.

DATA SYNTHESIS

We retrieved 6,420 studies; 33 met the inclusion criteria, 14 of which were in patients with sepsis. In the meta-analysis, the estimated mean differences and 95% CIs comparing the periods before and after transfusion were -0.0 L/min/m (-0.1 to 0.1 L/min/m) (p = 0.86) for cardiac index; -1.8 beats/min (-3.7 to 0.1 beats/min) (p = 0.06) for heart rate; 96.8 mL/min/m (71.1-122.5 mL/min/m) (p < 0.01) for oxygen delivery index; 2.9% (2.2-3.5%) (p < 0.01) for mixed venous oxygen saturation or central venous oxygen saturation; -3.7% (-4.4% to -3.0%) (p < 0.01) for oxygen extraction ratio; and 4.9 mL/min/m (0.9-9.0 mL/min/m) (p = 0.02) for oxygen consumption index. The estimated mean difference for oxygen consumption index in the patients with sepsis was 8.4 mL/min/m (2.3-14.5 mL/min/m; p = 0.01).

CONCLUSIONS

Transfusion was not associated with a decrease in mean cardiac output or mean heart rate. The increase in mean oxygen delivery following transfusion was associated with an increase in mean oxygen consumption after transfusion, especially in patients with sepsis.

Transfusion Decision Making in Pediatric Critical Illness

Transfusion decision making (TDM) in the critically ill requires consideration of: (1) anemia tolerance, which is linked to active pathology and to physiologic reserve, (2) differences in donor RBC physiology from that of native RBCs, and (3) relative risk from anemia-attributable oxygen delivery failure vs hazards of transfusion, itself. Current approaches to TDM (e.g. hemoglobin thresholds) do not: (1) differentiate between patients with similar anemia, but dissimilar pathology/physiology, and (2) guide transfusion timing and amount to efficacy-based goals (other than resolution of hemoglobin thresholds). Here, we explore approaches to TDM that address the above gaps.

Anemia and red blood cell transfusion in critically ill cardiac patients

Anemia and red blood cell (RBC) transfusion occur frequently in hospitalized patients with cardiac disease. In this narrative review, we report the epidemiology of anemia and RBC transfusion in hospitalized adults and children (excluding premature neonates) with cardiac disease, and on the outcome of anemic and transfused cardiac patients. Both anemia and RBC transfusion are common in cardiac patients, and both are associated with mortality. RBC transfusion is the only way to rapidly treat severe anemia, but is not completely safe. In addition to hemoglobin (Hb) concentration, the determinant(s) that should drive a practitioner to prescribe a RBC transfusion to cardiac patients are currently unclear. In stable acyanotic cardiac patients, Hb level above 70 g/L in children and above 70 to 80 g/L in adults appears safe. In cyanotic children, Hb level above 90 g/L appears safe. The appropriate threshold Hb level for unstable cardiac patients and for children younger than 28 days is unknown. The optimal transfusion strategy in cardiac patients is not well characterized. The threshold at which the risk of anemia outweighs the risk of transfusion is not known. More studies are needed to determine when RBC transfusion is indicated in hospitalized patients with cardiac disease.

Red blood cell transfusion in the critically ill patient

Red blood cell (RBC) transfusion is a common intervention in intensive care unit (ICU) patients. Anemia is frequent in this population and is associated with poor outcomes, especially in patients with ischemic heart disease. Although blood transfusions are generally given to improve tissue oxygenation, they do not systematically increase oxygen consumption and effects on oxygen delivery are not always very impressive. Blood transfusion may be lifesaving in some circumstances, but many studies have reported increased morbidity and mortality in transfused patients. This review focuses on some important aspects of RBC transfusion in the ICU, including physiologic considerations, a brief description of serious infectious and noninfectious hazards of transfusion, and the effects of RBC storage lesions. Emphasis is placed on the importance of personalizing blood transfusion according to physiological endpoints rather than arbitrary thresholds.

Exercise capacity and cardiovascular changes in patients with ?-thalassaemia major

Despite the introduction of deferoxamine, 50% of thalassaemia major patients die before the age of 35 years predominantly from iron induced heart failure. Indeed, the assessment of myocardial performance may be of particular interest since it can reveal an early myocardial dysfunction. By using impedance cardiography and mass spectrometry, we studied the cardiac function and the oxygen extraction ratio (O(2)ER) of 14 thalassaemic patients and 15 control healthy subjects during an incremental cycle-ergometer test. The achieved mechanical power output and the relative O(2) uptake did not reach any significant difference between groups. At the highest workload, O(2)ER reached significantly higher values in thalassaemic patients versus control subjects while the relationship between cardiac index (CI) and O(2)ER (CI/O(2)ER) decreased showing a lower contribution of cardiovascular system to maintain O(2) uptake. Results of this study imply that CI/O(2)ER allows an early diagnosis of the iron induced myocardial dysfunction, whereas it is not clinically patent yet. To our knowledge, this is the first study revealing an O(2)ER pivotal role as compensatory mechanism to maintain a normal working capacity in subjects suffering from thalassaemia major.

Transfusion in the intensive care unit

OBJECTIVE

To summarize the incidences of anemia and blood transfusions in critically ill patients, assess their comparative risks and benefits, and briefly speculate on the possible effects of leukoreduction and blood storage on the need to reevaluate transfusion triggers.

DESIGN

A review of the current literature was performed.

RESULTS

Anemia is common in intensive care unit patients and is associated with increased mortality. Some 20-53% of intensive care unit patients will receive a blood transfusion during their stay, and these have also been associated with worse outcomes. Leukoreduction may limit some of the infectious and immunomodulatory risks associated with blood transfusion.

CONCLUSIONS

Data on the risks and benefits of blood transfusion are conflicting, and with recent changes in blood transfusion practice, including the widespread introduction of leukoreduction, it is time to reevaluate our transfusion triggers.

Differential cardiovascular responses during weaning failure: effects on tissue oxygenation and lactate

OBJECTIVE

To test the following two hypotheses during weaning failure: (a) mixed venous oxygen saturation (SvO2) does not decrease in patients whose oxygen consumption does not increase, and (b) blood lactate may increase in patients who demonstrate substantial decreases in SvO2.

DESIGN AND SETTING

A prospective observational and physiological study in a 30-bed university intensive care unit.

PATIENTS AND PARTICIPANTS

18 patients who failed weaning and 12 patients who succeeded weaning (controls).

MEASUREMENTS AND RESULTS

Hemodynamics, global tissue oxygenation, cardiovascular response (cardiac index/oxygen extraction diagram), and blood lactate were measured in ventilator-supported patients undergoing a spontaneous breathing trial. In patients who failed without having increased their oxygen consumption (n=9) the increase in oxygen delivery was accompanied by a decrease in oxygen extraction (by 15+/-4%). In patients who failed (n=9) having increased their oxygen consumption (by>10%) this increase was met mainly by an increase in oxygen extraction (by 30+/-7%). SvO2 increased by 2+/-1% in the former patients, whereas it decreased by 20+/-5% in the latter. Arterial lactate increased (range 2.3-3.1 mM/l) in only three patients who failed to have increased oxygen consumption and exhibited heart failure and the highest decreases in SvO2 (by 12-39%).

CONCLUSIONS

Patients whose SvO2 does not decrease during weaning failure do not have increased oxygen consumption probably due to respiratory center depression in some of them. Patients whose SvO2 decreases have increased oxygen consumption.

Correction of anemia in patients with congestive heart failure increases resting energy expenditure

BACKGROUND & AIM

Congestive heart failure (CHF) and anemia were reported to affect resting energy expenditure (REE). The aim of this study was to evaluate the effect of the correction of anemia on REE in subjects with CHF.

PATIENTS AND METHODS

Nine anemic patients with compensated CHF and CRF were studied before and after correction of anemia. REE was studied by an open circuit indirect calorimeter, body composition by dual-energy-X-ray absorption and total body and extracellular water by multi-frequency bioelectrical impedence. Four anemic and 5 non-anemic CHF patients who did not receive any new treatment served as controls.

RESULTS

After the correction of their anemia patients tended to increase weight (P<0.06), but no significant changes were observed in body composition. Daily caloric intake increased significantly (P<0.02). Ejection fraction increased (P<0.05) and pulse rate decreased significantly (P<0.001). REE and REEPP were in the normal range before correction but increased significantly afterwards (1402+/-256 vs. 1496+/-206 kcal/d, and 101+/-9 vs. 109+/-8, P<0.023 and P<0.006, respectively).

CONCLUSION

Correction of anemia in patients with CHF increases their REE. This can be related either to improved tissue oxygenation and/or to increased caloric intake.

Do All Nonsurvivors of Cardiogenic Shock Die With a Low Cardiac Index? *

STUDY OBJECTIVES

To characterize the hemodynamic course of cardiogenic shock and to relate the cause of death to ongoing cardiac failure or multiple organ dysfunction.

DESIGN

Retrospective study.

SETTING

A 31-bed department of intensive care in a university hospital.

PATIENTS

All patients admitted for cardiogenic shock from January 1999 to December 2000.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Charts were reviewed for demographic, clinical, hemodynamic, oxygen transport, inflammation, and organ dysfunction data. Of 62 patients with cardiogenic shock, 40 (65%) did not survive. Eight patients (20%) died from fatal arrhythmia, 14 patients (35%) died with low cardiac index (CI) [ie, < 2.2 L/min/m(2)], and 18 patients (45%) died with normalized CI (ie, > 2.2 L/min/m(2)) and a higher CI/oxygen extraction ratio. Of these 18 patients, 9 had evidence of infection. The patients with normalized CI were younger and stayed longer in the ICU than patients with low CI.

CONCLUSION

A substantial number of patients with cardiogenic shock die with a normalized CI, suggesting a distributive defect, in the absence of obvious infection. These patients are younger and have a longer ICU course. The release of mediators may be secondary to gut hypoperfusion.

The hematologic system as a marker of organ dysfunction in sepsis

Sepsis with acute organ dysfunction (severe sepsis) results from a systemic proinflammatory and procoagulant response to infection. Organ dysfunction in the patient with sepsis is associated with increased mortality. Although most organs have discrete anatomical boundaries and carry out unified functions, the hematologic system is poorly circumscribed and serves several unrelated functions. This review addresses the hematologic changes associated with sepsis and provides a framework for prompt diagnosis and rational drug therapy. Data sources used include published research and review articles in the English language related to hematologic alterations in animal models of sepsis and in critically ill patients. Hematologic changes are present in virtually every patient with severe sepsis. Leukocytosis, anemia, thrombocytopenia, and activation of the coagulation cascade are the most common abnormalities. Despite theoretical advantages of using granulocyte colony-stimulating factor to enhance leukocyte function and/or circulating numbers, large clinical trials with these growth factors are lacking. Recent studies support a reduction in the red blood cell transfusion threshold and the use of erythropoietin treatment to reduce transfusion requirements. Treatment of thrombocytopenia depends on the cause and clinical context but may include platelet transfusions and discontinuation of heparin or other inciting drugs. The use of activated protein C may provide a survival benefit in subsets of patients with severe sepsis. The hematologic system should not be overlooked when assessing a patient with severe sepsis. A thorough clinical evaluation and panel of laboratory tests that relate to this organ system should be as much a part of the work-up as taking the patient's blood pressure, monitoring renal function, or measuring liver enzymes.

The International Sepsis Forum's frontiers in sepsis: High cardiac output should be maintained in severe sepsis

Despite a usually normal or high cardiac output, severe sepsis is associated with inadequate tissue oxygenation, leading to organ failure and death. Some authors have suggested that raising cardiac output and oxygen delivery to predetermined supranormal values may be associated with improved survival. While this may be of benefit in certain patients, bringing all patients to similar, supranormal values, is simplistic. It is much preferable to titrate therapy according to the needs of each individual patient. A combination of variables should be used for this purpose, in addition to a careful clinical evaluation, including not only cardiac output but also the mixed venous oxygen saturation and the blood lactate concentrations. The concept is to assess the adequacy of the cardiac output in patients with severe sepsis, enabling management strategies aimed at optimizing cardiac output to be tailored to the individual patient.