Blood conservation in acute care and critical care

What blood conservation practices are effective at reducing blood sampling volumes and other clinical sequelae in intensive care? A systematic review

OBJECTIVES

The objective of this study was to critically appraise and synthesise evidence for blood conservation strategies in intensive care. Blood sampling is a critical aspect of intensive care to guide clinical decision-making. Repeated blood sampling can result in blood waste and contamination, leading to iatrogenic anaemia and systemic infection.

REVIEW METHOD USED

Cochrane systematic review methods were used including meta-analysis, and independent reviewers.

DATA SOURCES

A systematic search was conducted in Medline, CINAHL, PUBMED and EMBASE databases. The search was limited to randomised controlled trials (RCTs) and cluster RCTs, published in English between 2000 and 2021.

REVIEW METHODS

Paired authors independently assessed database search results and identified eligible studies. Trials comparing any blood conservation practice or product in intensive care were included. Primary outcomes were blood sample volumes and haemoglobin change. Secondary outcomes included proportion of patients receiving transfusions and infection outcomes. Quality appraisal employed the Cochrane Risk of Bias tool. Meta-analysis using random effects approach and narrative synthesis summarised findings.

RESULTS

Eight studies (n = 1027 patients), all RCTs were eligible. Six studies included adults, one studied paediatrics and one studied preterm infants. Seven studies evaluated a closed loop blood sampling system, and one studied a conservative phlebotomy protocol. Studies were of low to moderate quality. Meta-analysis was not possible for interventions targeting blood sample volumes or haemoglobin. Decreased blood sample volumes reported in four studies were attributable to a closed loop system or conservative phlebotomy. No study reported a significant change in haemoglobin. Meta-analysis demonstrated that use of a closed system (compared to open system) reduced the proportion of patients receiving transfusion [Risk Ratio (RR) 0.65, 95% CI 0.46-0.92; 287 patients] and reduced intraluminal fluid colonisation [RR 0.25, 95% CI 0.07-0.58; 500 patients].

CONCLUSIONS

Limited evidence demonstrates closed loop blood sampling systems reduced transfusion use and fluid colonisation. Simultaneous effectiveness-implementation evaluation of these systems and blood conservation strategies is urgently required.

PROSPERO PROTOCOL REGISTRATION REFERENCE

CRD42019137227.

'True Blood' The Critical Care Story: An audit of blood sampling practice across three adult, paediatric and neonatal intensive care settings

BACKGROUND

Anaemia is common in critically ill patients, and has a significant negative impact on patients' recovery. Blood conservation strategies have been developed to reduce the incidence of iatrogenic anaemic caused by sampling for diagnostic testing.

OBJECTIVES

Describe practice and local guidelines in adult, paediatric and neonatal Australian intensive care units (ICUs) regarding blood sampling and conservation strategies.

METHODS

Cross-sectional descriptive study, conducted July 2013 over one week in single adult, paediatric and neonatal ICUs in Brisbane. Data were collected on diagnostic blood samples obtained during the study period, including demographic and acuity data of patients. Institutional blood conservation practice and guidelines were compared against seven evidence-based recommendations.

RESULTS

A total of 940 blood sampling episodes from 96 patients were examined across three sites. Arterial blood gas was the predominant reason for blood sampling in each unit, accounting for 82% of adult, 80% of paediatric and 47% of neonatal samples taken (p<0.001). Adult patients had significantly more median [IQR] samples per day in comparison to paediatrics and neonates (adults 5.0 [2.4]; paediatrics 2.3 [2.9]; neonatal 0.7 [2.7]), which significantly increased median [IQR] blood sampling costs per day (adults AUD$101.11 [54.71]; paediatrics AUD$41.55 [56.74]; neonatal AUD$8.13 [14.95]; p<0.001). The total volume of samples per day (median [IQR]) was also highest in adults (adults 22.3mL [16.8]; paediatrics 5.0mL [1.0]; neonates 0.16mL [0.4]). There was little information about blood conservation strategies in the local clinical practice guidelines, with the adult and neonatal sites including none of the seven recommendations.

CONCLUSIONS

There was significant variation in blood sampling practice and conservation strategies between critical care settings. This has implications not only for anaemia but also infection control and healthcare costs.

What factors influence arterial blood gas sampling patterns?

STUDY OBJECTIVE

To investigate if patterns of arterial blood gas (ABG) sampling were influenced by values of fractional inspiratory oxygen (FiO2), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2) and oxygen saturation (%SaO2).

SETTING

An intensive care unit (ICU) in a university teaching hospital located in the North of England, UK.

DESIGN

A retrospective, descriptive, correlation study based on patient records.

PARTICIPANTS

All patients admitted to the ICU for 24 hours or greater and who had an arterial line in situ.

MEASUREMENTS AND RESULTS

The study included the records of 65 patients consecutively admitted to the ICU. Patients in this study had more blood gases taken than reported elsewhere in the literature. While consistent correlation was found between values of FiO2, PCO2, PO2 and %SaO(2), values of PO2 were the most consistent.

CONCLUSIONS

Values of PO2 are associated with frequency of ABG sampling and to a lesser extent on FiO2. Nurses in this study opted to track changes in oxygenation using ABGs despite continuous monitoring of %SaO2.

Blood Conservation Strategies in Cardiovascular Surgery

Blood conservation is a measurable intervention in which clinical and financial outcomes may be tracked. This article describes a systems approach to blood conservation for a cardiac surgery population. Four key areas are discussed: needs assessment, committee construction, blood conservation strategies, and outcome measurement. Specific evidenced-based blood conservation strategies include, but are not limited to, transfusion risk index, phlebotomy techniques, management of hemostasis and hemoglobin levels which includes blood testing, pharmacologic agents, and blood transfusion prescription guidelines.

Point-of-care testing

Point-of-care testing technology rapidly is changing the way physicians practice medicine by facilitating the availability of biochemical parameters immediately or almost immediately. The constant evolution and developments in [figure: see text] microchemistry and computer technology will make this area a dynamic part of medicine with the constant emergence of improved and newer technologies. Clinicians must not forget, however, that the best analyzer and monitor is the physician, nurse, or other health care worker in direct contact with the patient, constantly reassessing, re-examining, and integrating all of the physiologic and biochemical data in the context of the history and physical examination. If POC testing is implemented, its goal should be to improve and assist in patient care.

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 laboratory-clinical interface: point-of-care testing

POC testing provides an opportunity for clinicians and laboratorians to work together to consider how best to serve the patients within an individual institution. Each health system has unique characteristics relative to patient population, as well as a unique laboratory structure. If physicians, nurses, laboratorians, and pathologists work collaboratively, the best interests of patients will be served. In some institutions that cater to specific patient groups, POC testing may offer clear and distinct advantages. In other institutions with sophisticated transport systems and established rapid response capabilities, the quality resulting from central laboratory testing may outweigh any advantages of bedside testing. Clearly, attention to regulatory issues, QC issues, the importance of proper documentation, proficiency testing, performance enhancement, and cost-effectiveness is requisite. As the technology for diagnostic testing advances through more microcomputerization, microchemistry, and enhanced test menus, the concept of POC testing will need perpetual revisiting. We hope that the information provided here will aid clinicians, laboratorians, and administrators in their quest to best serve their patients.