From Strategic Blood Management - http://www.bloodmanagement.com/about-blood-management/10-facts-about-blood-transfusions.html
Objective:
To develop a clinical practice guideline for red blood cell transfusion in adult trauma and critical care.
Methods:
Comprehensive literature review of the topic and graded the evidence using scientific assessment methods employed by the Canadian and U.S. Preventive Task Force
A list of guideline recommendations was compiled by the members of the guidelines committees for the two societies.
Key Recommendations Including:
Indications for RBC transfusion in the general critically ill patient
RBC transfusion in sepsis
RBC transfusion in patients at risk for or with acute lung injury and acute respiratory distress syndrome
RBC transfusion in patients with neurologic injury and diseases
RBC transfusion risks
Alternatives to RBC transfusion
Strategies to reduce RBC transfusion.
Consider transfusion if Hb is 7g/dL in resuscitated critically ill trauma patients. There is no benefit of a “liberal” transfusion strategy (transfusion when Hb is 10g/dL) in resuscitated critically ill patients. (Level 2)
Consider transfusion if Hb is 7g/dL in critically ill patients with stable cardiac disease. No benefit ofa “liberal” transfusion strategy (transfusion when Hb is 10 g/dL)in critically ill patients with stable cardiac disease. (Level 2)
RBC transfusion may be beneficial in patients with acute coronary syndromes (ACS) who are anemic (Hb 8 g/dL) on hospital admission. (Level 3)
Notes for bullets
Indications for RBC transfusion in the general critically ill patient
RBC transfusion is indicated for patients with evidence of hemorrhagic shock. (Level 1)
RBC transfusion may be indicated for patients with evidence of acute hemorrhage and hemodynamic instability or inadequate D˙O2. (Level 1)
A “restrictive” strategy of RBC transfusion (transfuse when Hb is 7 g/dL) is as effective as a “liberal” transfusion strategy (transfusion when Hb is 10 g/dL) in critically ill patients with hemodynamically stable anemia, except in patients with acute myocardial infarction (MI) or unstable myocardial ischemia.(Level 1)
The use of only Hb level as a “trigger” for transfusion should be avoided. Decision for RBC transfusion should be based on an individual patient’s intravascular volume status, evidence of shock, duration and extent of anemia, and cardiopulmonary physiologic parameters. (Level 2)
In the absence of acute hemorrhage, RBC transfusion should be given as single units. (Level 2) Consider transfusion if Hb is 7 g/dL in critically ill patients requiring mechanical ventilation (MV). There is no benefit of a “liberal” transfusion strategy (transfusion when Hb is 10 g/dL) in critically ill patients requiring MV. (Level 2)
Consider transfusion if Hb is 7g/dL in resuscitated critically ill trauma patients. There is no benefit of a “liberal” transfusion strategy (transfusion when Hb is 10g/dL) in resuscitated critically ill patients. (Level 2)
Consider transfusion if Hb is 7g/dL in critically ill patients with stable cardiac disease. No benefit ofa “liberal” transfusion strategy (transfusion when Hb is 10 g/dL)in critically ill patients with stable cardiac disease. (Level 2)
RBC transfusion should not be considered as an absolute method to improve tissue V˙ O2 in critically ill patients. (Level 2)
RBC transfusion may be beneficial in patients with acute coronary syndromes (ACS) who are anemic (Hb 8 g/dL) on hospital admission. (Level 3)
RBC transfusion in sepsis
The transfusion needs for each septic patient must be assessed individually because optimal transfusion triggers in sepsis patientsare not known and there is no clear evidence that blood transfusion increases tissue oxygenation.(Level 2)
RBC transfusion in patients at risk for or with acute lung injury and acute respiratory distress syndrome
All efforts should be initiated to avoid RBC transfusion in patients at risk for ALI and ARDS after completion of resuscitation. (Level 2)
All efforts should be made to diagnose and report TRALI to the local blood bank because it has emerged as a leading cause of transfusionassociated morbidity and mortality, despite underdiagnosis and underreporting. (Level 2)
RBC transfusion should not be considered as a method to facilitate weaning from MV. (Level 2)
RBC transfusion in patients with neurologic injury and diseases
There is no benefit of a “liberal” transfusion strategy (transfusion when Hb is 10 g/dL) in patients with moderate-to-severe traumatic brain injury. (Level 2)
Decisions regarding blood transfusion in patients with subarachnoid hemorrhage (SAH) must be assessed individually because optimal transfusion triggers are not known and there is no clear evidence that blood transfusion is associated with improved outcome. (Level 3)
RBC transfusion risks
RBC transfusion is associated with increased nosocomial infection (wound infection, pneumonia, sepsis) rates independent of other factors. (Level 2)
RBC transfusion is an independent risk factor for MOF and SIRS. (Level 2)
There is no definitive evidence that prestorage leukocyte reduction of RBC transfusion reduces complication rates, but some studies have shown a reduction in infectious complications. (Level 2)
RBC transfusions are independentlyassociated with longer ICU and hospital lengths of stay, increased complications, and increased mortality. (Level 2)
There is a relationship between transfusion and ALI and ARDS. (Level 2)
Alternatives to RBC transfusion
Recombinant human erythropoietin (rHuEpo) administration improves reticulocytosis and hematocrit and may decrease overall transfusion requirements.(Level 2)
Hemoglobin-based oxygen carriers (HBOCs) are undergoing investigation for use in critically ill and injured patients but are not approved for use in the United States. (Level 2)
Strategies to reduce RBC transfusion
The use of low-volume adult or pediatric blood sampling tubes is associated with a reduction in phlebotomy volumes and a reduction in blood transfusion.(Level 2)
The use of blood conservation devices for reinfusion of waste blood with diagnostic sampling is associated with a reduction in phlebotomy volume. (Level 2)
Intraoperative and postoperative blood salvage and alternative methods for decreasing transfusion may lead to a significant reduction in allogeneic blood usage.(Level 2)
Reduction in diagnostic laboratory testing is associated with a reduction in phlebotomy volumes and a reduction in blood transfusion.(Level 2)
- Body Position and temporal effect of venous vs. capillary sampling on the result.
Body position is known to have a significant effect on venous Hb measurements due to decreases in plasma volume on assuming an upright position. Heart rate and blood pressure are higher when standing vs. sitting. The higher blood pressure associated with standing induces the movement of intravascular fluid such as plasma into interstitial compartments. This causes plasma volume to decrease and hematocrits and hemoglobin levels to rise (hemoconcentration).14 Gore and colleagues showed a 6% reduction on plasma volume which have a substantial impact on hematocrits (6 percentage points, or 2 g/dL.) 15
Screening Hb measurements used to determine blood donor eligibility obtained in the seated position at equilibrium may significantly underestimate circulating venous Hb values. Having the donor stand for at least one minute prior to obtaining a finger stick Hb may result in Hb readings that more closely approximate venous Hb levels. From seated to standing for 20 minutes may result in a change in Hb concentration by > 1.0 g/dL. 16 The converse is also true, indicating that patients who are ambulatory may require a period of equilibration of they change body position prior to the blood draw.
High within subject variability was identified when capillary blood from the left hand was compared with that from the right hand (reliability 69%) and when measurements were taken on 4 consecutive days (reliability 50%).10
INTRODUCTION:
Total hemoglobin (Hb) is one of the most frequently-ordered laboratory measurements in both acute
and outpatient settings. Current laboratory methods are invasive, time consuming, and can only provide
intermittent Hb measurements. Noninvasive and continuous Hb measurement would offer many advantages
in the assessment of both acute and chronic anemia in a variety of clinical settings. The purpose of this study
was to evaluate the accuracy of a new noninvasive Hb measurement technology called Pulse
CO-Oximetry® compared to invasive laboratory measurement of Hb.
METHODS:
All data were collected under institutional review board approval and all patients provided written,
informed consent. A self-calibrating Pulse CO-Oximeter (Masimo Rainbow SET, Masimo, Irvine, CA) with a
spectrophotometric sensor (Rainbow DCI) with multiple wavelengths of light was utilized. The Pulse
CO-Oximetry method discerns the distinctive light-absorption characteristics of different hemoglobin species
and applies proprietary algorithms to determine Hb levels. Study subjects consisted of healthy adults,
volunteers undergoing a hemodilution protocol, and surgery patients (liver transplant, caesarean section,
or exploratory laparotomy). The hemodilution protocol consisted of replacing one unit of blood with 30 ml/
kg of saline. Each SpHb measurement was matched with a corresponding invasive Hb measurement from
a laboratory CO-Oximeter (Radiometer model ABL-820). Bias, precision, and the average root mean square
(ARMS) were calculated.
RESULTS:
Data were collected at three sites, Loma Linda Medical Center (Loma Linda, CA), Mayo Clinic (Jacksonville,
FL), and Masimo Corporation (Irvine, CA). A total of 492 data pairs were collected from 59 subjects, 35 (59%)
healthy adults, 16 (27%) hemodilution subjects, and 8 (14%) from surgical subjects. A total of 43 subjects
(72%) were male and 53 subjects (90%) had light skin pigmentation. Collected invasive hemoglobin (tHb)
values had a range of 6 to 18 g/dL, with 220 (45%) tHb measurements <12 g/dL, 145 (29%) <11 g/dL, and
74 (15%) <10 g/dL. Tabular results are shown in Table 1, range accuracy is shown in Table 2, and a scatter
plot of tHb and SpHb measurements is shown in Figure 1.
CONCLUSION:
Pulse CO-Oximetry SpHb measurement provides clinically acceptable accuracy compared to laboratory
CO-Oximeter tHb measurement in the 8 to 18 g/dL range.
Dr. John Viljoen, clinical professor of anesthesiology at Loma Linda University School of Medicine in California, walked in to find his office cluttered with testing equipment being used in a clinical study validating Masimo’s new noninvasive total hemoglobin monitoring technology. His interest piqued, he asked one of the technicians to “stick one of those sensors on me.” After receiving a low hemoglobin reading of 10.6 from our device, Dr. Viljoen—who exhibited no prior symptoms—had the results validated by a laboratory blood test. He then had a series of additional tests done that ultimately led to a diagnosis of esophageal cancer that had metastasized in the upper part of his left arm. He had surgery to remove the tumor in his esophagus and replace his left shoulder, “and up to this point have had no complications. I even got out to play golf the other day.”“My life expectancy has been totally changed as a result of that random assessment of noninvasive total hemoglobin,” Dr. Viljoen explained. “If it were not for that procedure having been done, I would have had to wait for symptoms of thecancer to occur, at which time it would probably have been inoperable and the whole sequence of events would have been totally different—resulting in all probability in my not being here today.”