Anemia and red cell transfusion in critically ill patients

Mechanisms of red blood cell transfusion-related immunomodulation

Red blood cell (RBC) transfusion is common in critically ill, postsurgical, and posttrauma patients in whom both systemic inflammation and immune suppression are associated with adverse outcomes. RBC products contain a multitude of immunomodulatory mediators that interact with and alter immune cell function. These interactions can lead to both proinflammatory and immunosuppressive effects. Defining clinical outcomes related to immunomodulatory effects of RBCs in transfused patients remains a challenge, likely due to complex interactions between individual blood product characteristics and patient-specific risk factors. Unpacking these complexities requires an in-depth understanding of the mechanisms of immunomodulatory effects of RBC products. In this review, we outline and classify potential mediators of RBC transfusion-related immunomodulation and provide suggestions for future research directions.

Blood transfusion in acute and chronic pediatric settings: beliefs and practices

BACKGROUND

Blood has been imbued with powerful connotations through history and across cultures. Currently bestowed with scientific meaning, blood nevertheless carries symbolic resonance. This study examines these representations among practitioners and sheds light on the clinical and nonclinical factors that guide blood transfusion (BT) decision-making in Quebec, Canada.

STUDY DESIGN AND METHODS

With a qualitative exploratory study design, data were collected in the pediatric intensive care unit and the hematology-oncology unit of Sainte-Justine Hospital in 2009. A total of fifteen 1-hour-long semistructured interviews were conducted with physicians.

RESULTS

Physicians affirm that the symbolic connotations of blood found in the lay population do not influence their transfusion decisions. However, there are other "social" and "cultural' aspects that influence these practices. Also, BT strategies remain diverse across units. Practitioners perceive these situations as resulting from insufficient training and by the existence of an "oral tradition" and a professional culture that are resistant to change.

CONCLUSION

BT practices differ within and across units. Many dimensions intervene in the decision to transfuse, from individual clinical appreciation and local unit "culture" to formal and ad hoc training. Consistent change in BT can only occur with the implementation of norms and guidelines that are endorsed by key influential figures. An extensive multicentered study is necessary to better understand how social and cultural factors affect BT practices. This knowledge will sustain an enlightened clinical practice and lead to the recognition that peer practices are also embedded in professional cultures.

Blood transfusions in septic shock: is 7.0 g/dL really the appropriate threshold?

OBJECTIVE

To evaluate the immediate effects of red blood cell transfusion on central venous oxygen saturation and lactate levels in septic shock patients with different transfusion triggers.

METHODS

We included patients with a diagnosis of septic shock within the last 48 hours and hemoglobin levels below 9.0 g/dL Patients were randomized for immediate transfusion with hemoglobin concentrations maintained above 9.0 g/dL (Group Hb9) or to withhold transfusion unless hemoglobin felt bellow 7.0 g/dL (Group Hb7). Hemoglobin, lactate, central venous oxygen saturation levels were determined before and one hour after each transfusion.

RESULTS

We included 46 patients and 74 transfusions. Patients in Group Hb7 had a significant reduction in median lactate from 2.44 (2.00 - 3.22) mMol/L to 2.21 (1.80 - 2.79) mMol/L, p = 0.005, which was not observed in Group Hb9 [1.90 (1.80 - 2.65) mMol/L to 2.00 (1.70 - 2.41) mMol/L, p = 0.23]. Central venous oxygen saturation levels increased in Group Hb7 [68.0 (64.0 - 72.0)% to 72.0 (69.0 - 75.0)%, p < 0.0001] but not in Group Hb9 [72.0 (69.0 - 74.0)% to 72.0 (71.0 - 73.0)%, p = 0.98]. Patients with elevated lactate or central venous oxygen saturation < 70% at baseline had a significant increase in these variables, regardless of baseline hemoglobin levels. Patients with normal values did not show a decrease in either group.

CONCLUSION

Red blood cell transfusion increased central venous oxygen saturation and decreased lactate levels in patients with hypoperfusion regardless of their baseline hemoglobin levels. Transfusion did not appear to impair these variables in patients without hypoperfusion. ClinicalTrials.gov NCT01611753.

Red blood cell transfusions worsen the outcomes even in critically ill patients undergoing a restrictive transfusion strategy

CONTEXT AND OBJECTIVE

Anemia and blood transfusions are common in intensive care. This study aimed to evaluate epidemiology and outcomes among critically ill patients under a restrictive transfusion strategy.

DESIGN AND SETTING

Prospective observational cohort study in an intensive care unit (ICU) at a tertiary hospital.

METHODS

All adults admitted to the ICU over a one-year period who remained there for more than 72 hours were included, except those with acute coronary syndrome, ischemic stroke, acute hemorrhage, prior transfusion, pregnant women and Jehovah's Witnesses. The restrictive strategy consisted of transfusion indicated when hemoglobin levels were less than or equal to 7.0 g/dl.

RESULTS

The study enrolled 167 patients; the acute physiology and chronic health evaluation II (APACHE II) score was 28.9 ± 6.5. The baseline hemoglobin level was 10.6 ± 2.2 g/dl and on day 28, it was 8.2 ± 1.3 g/dl (P < 0.001). Transfusions were administered to 35% of the patients. In the transfusion group, 61.1% did not survive, versus 48.6% in the non-transfusion group (P = 0.03). Transfusion was an independent risk factor for mortality (P = 0.011; odds ratio, OR = 2.67; 95% confidence interval, CI = 1.25 to 5.69). ICU stay and hospital stay were longer in the transfusion group: 20.0 (3.0-83.0) versus 8.0 (3.0-63.0) days (P < 0,001); and 24.0 (3.0-140.0) versus 14.0 (3.0-80.0) days (P = 0.002), respectively.

CONCLUSIONS

In critically ill patients, there was a reduction in hemoglobin with increasing length of ICU stay. Moreover, transfusion was associated with worse prognoses.

Determinants of red blood cell transfusions in a pediatric critical care unit: A prospective, descriptive epidemiological study*

OBJECTIVE

To determine the incidence and to characterize the determinants of red blood cell transfusions in critically ill children.

DESIGN

Prospective, descriptive epidemiologic study.

SETTING

A single-center, multidisciplinary, tertiary care level, university-affiliated, pediatric intensive care unit (PICU).

PATIENTS

Critically ill children.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 1,047 consecutive admissions over a 1-yr period, 985 were retained for study. At least one transfusion was given in 139 cases (14%). Incidence rate of transfusion was 304 transfusions/1,000 cases. Possible determinants of red blood cell transfusions were identified and prospectively monitored during PICU stay until a first transfusion event (transfused cases) or up until the time of death or discharge from PICU (nontransfused cases). Four significant determinants of a first red blood cell transfusion event were retained in the multivariate analysis (odds ratio, 95% confidence interval, p): a hemoglobin level <9.5 g/dL during PICU stay (13.26, 8.04-21.88, p < .001), an admission diagnosis of cardiac disease (8.07, 5.14-14.65, p < .001), an admission Pediatric Risk of Mortality score >10 (4.83, 2.33-10.04, p < .001), and the presence of multiple organ dysfunction syndrome during the stay (2.06, 1.18-3.57, p = .01).

CONCLUSION

A significant proportion of critically ill children receive at least one red blood cell transfusion during their PICU stay. Presence of anemia, cardiac disease, severe critical illness, and multiple organ dysfunction syndrome are the most significant determinants of red blood cell transfusions in PICU.

Evaluation of blood transfusion effects on mixed venous oxygen saturation and lactate levels in patients with SIRS/sepsis

PURPOSE

To evaluate the effects of red blood cell transfusion in patients with SIRS/sepsis who presented hemoglobin levels under 9.0 g/dL at intensive care unit admission, using two parameters of organ perfusion: mixed venous oxygen saturation and serum lactate levels.

METHODS

All patients admitted to the intensive care unit with SIRS/sepsis, as defined by Consensus Conference in 1992, and hemoglobin levels under 9.0 g/dL were included. Hemoglobin levels, mixed venous oxygen saturation, and lactate levels were collected before red blood cell transfusion (pre-T) and up to 1 hour after transfusion (post-T). These variables were analyzed through a paired t test, and results were considered significant if P < .05.

RESULTS

Twenty-nine patients (17 male, 12 female) with ages of 61.9 +/- 15.1 (mean +/- SD) years (range, 21-85 years) and a mean APACHE II score of 12.5 +/- 3.75 (7-21) were transfused with a mean of 1.41 packed red cell units. A significant increase in hemoglobin levels was reached by blood transfusion, from 8.14 +/- 0.64 g/dL (pre-T) to 9.4 +/- 0.33 g/dL (post-T), with P <.001. However, this was not accompanied by a significant change in lactate levels, from 1.87 +/- 1.22 mmol/l (pre-T) to 1.56 +/- 0.28 mmol/l (post-T), with P =.28, or in mixed venous oxygen saturation, from 64.3 +/- 8.52% (pre-T) to 67.4 +/- 6.74% (post-T), with P = .13. The results were similar even in patients with hemoglobin levels under 8.0 g/dL (n = 9). These results suggest that red blood cell transfusions, in spite of leading to a significant increase in hemoglobin levels, are not associated with an improvement in tissue oxygenation in patients with SIRS/sepsis and hemoglobin levels < 9 g/dL.

Progress in Postoperative ICU Management

The clinical case presented in this article illustrates how many of the more recent advances in the management of critically ill patients apply to current clinical practice. Simple cost-effective general measures (eg, optimal sterile precautions during procedures; hand washing; early goal-directed resuscitation with appropriate fluids, inotropes, and antibiotics; and surgical source control of infected foci) still should form the basis of clinical practice, however. There has been renewed interest in blood transfusion therapy and its associated risks. Lower tidal volume ventilation now is practiced almost universally in patients with ARDS, and several new selective pulmonary vasodilators have extended the armamentarium when taking care of these patients. High-frequency oscillatory ventilation and ECMO remain challenging options in patients with refractory hypoxemia. Appropriate patient selection is important when corticosteroid therapy is considered. Tight blood glucose control and monitoring improve outcome and should be part of ICU care of septic patients. The role of the PAC is controversial. Other techniques to measure cardiac output, hemodynamics, and perfusion are available and should be considered. Sedation and analgesia form an integral part of critical care. Because of its immediate and long-term risks, neuromuscular blockade should be used sparingly and only when all other options have been exhausted. Ongoing education regarding sedation protocols and the effect of sedation on outcome is needed among physicians and nurses caring for these patients.

Red cell requirements for intensive care units adhering to evidence-based transfusion guidelines

BACKGROUND

Anemia commonly complicates critical illness. Restrictive transfusion triggers are appropriate in this setting, but no large studies have measured red cell (RBC) requirements for intensive care patients when evidence-based transfusion guidelines are followed consistently.

STUDY DESIGN AND METHODS

Data were recorded daily for 1023 of 1042 sequential admissions to 10 intensive care units (ICUs) over 100 days. The sample comprised 44 percent of all ICU admissions in Scotland during this period. RBC transfusions and the occurrence of clinically significant hemorrhage were recorded for every ICU day. Transfusion episodes were classified as either associated with or not associated with hemorrhage. Measures of RBC use were derived for the cohort and for Scotland with national audit data.

RESULTS

A total of 39.5 percent (95% confidence interval [CI], 36.5%-42.5%) of admissions received transfusions. Eighteen percent of admissions received at least one transfusion associated with hemorrhage and 26 percent received at least one transfusion not associated with hemorrhage. The median (interquartile range) transfusion trigger in the absence of hemorrhage was 78 (73-78) g/L. The overall mean RBC use was 1.87 (95% CI, 1.79-1.96) units per admission or 0.34 (95% CI, 0.33-0.36) units per ICU-day. Forty-seven percent of RBCs administered were not associated with clinically significant hemorrhage. Mean RBC requirements for intensive care in Scotland were estimated to be 3950 (95% CI, 3780-4140) per million-adult-population per year. This represented 7 to 8 percent of the Scottish blood supply.

CONCLUSIONS

Despite evidence-based transfusion practice, 40 percent of ICU patients receive transfusions, which account for 7 to 8 percent of the national blood supply.

Improving glycaemic control in a metabolically stressed patient in ICU

This article describes a clinical experience where the careful application of problem-solving skills has resulted in positive changes in glycaemic care in a critical care environment. The metabolic stress response to trauma injuries leads to episodes of hyperglycaemia. The application of a problem-solving process has resulted in greater understanding of best practice of the management of this problem. The importance of strict control of blood glucose levels in the critically ill patient is highlighted. Although the practice areas in this article is a specialized intensive care environment, in light of recent government-led recognition that many patients in hospital are increasingly ill (Department of Health (DoH), 1998a), this situation may arise in many ward environments.