Critical Care Testing - Quality Assurance

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3 Critical Care Testing Quality Assurance This book describes the various quality assurance procedures at all stages in the patient testing cycle and how they contribute towards obtaining the correct patient result.
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Transcript of Critical Care Testing - Quality Assurance

Critical Care TestingQuality AssuranceThis book describes the various quality assurance procedures at all stages in the patient testing cycle and how they contribute towards obtaining the correct patient result.

3

Critical Care TestingQuality Assurance

Andrew St John

Roche Diagnostics1

Impressum by Roche Diagnostics, Mannheim, Germany Cover: !Now Werbeagentur AG, CH-4051 Basel Artwork & Layout: Eva Baumgartner, CH-8200 Schaffhausen Printed by: stamm+co, CH-8226 Schleitheim First Edition April 2001

Preface

Quality Assurance & Critical Care Testing

PrefaceThis book provides an overview of quality assurance as applied to the critical care testing process and it is intended for a broad audience. First and foremost that audience includes those people who have received no formal training in laboratory practices such as clinicians, nurses and paramedical staff but who are now using diagnostic devices. While laboratory professionals almost live and breathe quality assurance, the topics of pre-analytical and post analytical quality assurance have not perhaps received the attention they deserve in the past but are especially important to the critical care testing process. Therefore I would hope that my scientific colleagues will also find new and relevant information in this booklet. Last but by no means least I would encourage my company colleagues to use this book to help them provide some of the answers to the growing number of questions that customers now direct to the suppliers of diagnostic devices, many of which are related to issues of quality. As with the previous books many people, both colleagues and customers, have made contributions to this book. First and foremost, my appreciation goes to Dr Jean-Francois Mollard, formerly of AVL France and Dr Sharon Ehrmeyer of the University of Wisconsin, USA whose previous publications in the area of quality assurance I have drawn on extensively for this book. My thanks also to Miles Sykes of the Bradford Royal Infirmary, UK for his critical comments and to my usual prooof-readers, Les Watkinson of Roche Australia and Regina Herz from Roche Diagnostics, Graz. Finally of course, I must acknowledge Eva Baumgartner who as with the previous books has converted my writing into the professional publication that you have in front of you today. Dr. Phd. Andrew St John Roche Diagnostics, Mannheim, Germany3

Quality Assurance & Critical Care Testing

Contents

Contents:

Chapter I IntroductionQuality assurance & the critical care testing cycle

1

Chapter II Pre-Analytical Quality Assurance 11

Steps in pre-analytical quality assurance Collection device or container Anticoagulants Patient preparation Sample site Sample collection Sample treatment and transport Immediate pre-analysis Summary of pre-analytical quality assurance procedures

Chapter III Analytical Quality AssuranceAspects of analytical quality assurance Terminology, types & principles of quality control Internal quality control using control materials Internal quality control using patient data Special aspects of internal quality control on Roche instruments External quality control using control materials Factors affecting analytical quality

41

Contents

Quality Assurance & Critical Care Testing

Chapter IV Post-Analytical Quality AssuranceStages in post-analytical quality assurance Combining results with patient information Critical or panic values Interpretation of data Reporting of data and information

83

Chapter V Management of testing outside the laboratoryProfessional & local guidelines

97

References List of figures & tables Index

102 106 109

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Quality Assurance & Critical Care Testing

Chapter I

6

Chapter I

Quality Assurance & Critical Care Testing

Chapter I

Introduction

1

Quality Assurance & Critical Care Testing

Chapter I

Quality and Critical Care TestingThere are many definitions of quality but in relation to diagnostic testing a quality service can be defined as one which meets the needs and expectations of the users (doctors & nurses) or customers (patients). In plain terms this means providing the right result accompanied by the right interpretation for the right test at the right time on the right specimen from the right patient. As part of the evolution of quality systems in healthcare many laboratories have adopted the principles of Total Quality Management (TQM) which is a structured approach to meeting quality standards. TQM as shown in the diagram opposite is a feedback cycle which comprises a number of distinct processes called Quality Planning, Quality Laboratory Processes, Quality Control, Quality Assurance and lastly Quality Improvement. In order to provide a concise account of the quality processes and potential errors in critical care testing this book will concentrate on the Quality Assurance and Quality Control aspects. For more details of the principles of TQM, readers should consult a laboratory textbook such as Tietz (1). Quality Assurance (QA) can be defined as the management process by which the quality of the complete testing process is both maintained and improved. Quality Control (QC) is just one part of QA and is concerned with analytical quality ie obtaining the right result.

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Chapter I

Quality Assurance & Critical Care Testing

Quality in Critical Care TestingQuality Planning

Quality Improvement

TQM processes in Critical Care Testing

Quality Laboratory Processes

Quality Assurance

Quality Control

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Quality Assurance & Critical Care Testing

Chapter I

Quality Assurance and Critical Care TestingThe critical care testing process or patient testing cycle commences by the clinician asking a question about the patient which is answered by performing a laboratory analysis and providing a diagnostic answer. A simple approach to assessing and improving the quality of critical care testing is to consider the testing cycle in three phases as shown in the diagram opposite. The first pre-analytical stage of the cycle involves collection and transport of the patient specimen. Although the movement of critical care testing closer to the patient has reduced the potential length of the pre-analytical phase, the lability of many critical care parameters still means that preanalytical procedures are especially important to monitor and control. The second phase is the actual analysis of the specimen. This analytical phase requires conventional quality control procedures such as internal and external quality control which are similar to those for any analytical device. The third and final phase is called the post-analytical phase and involves processes such as integration of patient information with analytical results, comparison to reference and critical values, interpretation and finally the reporting of information the diagnostic answer to the clinician and into the patient record.

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Chapter I

Quality Assurance & Critical Care Testing

Quality Assurance & Critical Care TestingDiagnostic answer ! Reporting of Information Clinical question ? Specimen Collection

Patient Patient Testing Cycle

Post-Analysis

Pre-Analysis

Adding Value to Data

AnalysisQuality Control

Specimen Transport

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Quality Assurance & Critical Care Testing

Chapter I

Potential Errors in Critical Care TestingThe consequences of not delivering a quality critical care testing service are many but they include: Making the wrong diagnosis in a patient Patients receiving the wrong treatment Patients not receiving treatment or receiving it at the wrong time Conducting the wrong investigations in a patient Poor quality is often due to errors occurring in the critical care testing process and the diagram opposite shows the major errors associated with each of the 3 phases which make up the patient testing cycle. The fact that more errors are associated with the pre-analytical phase is primarily a reflection of the fact that more manual interventions are required compared to the other two phases where a degree of automation exits. Ideally each laboratory should conduct a systems analysis of its testing process to document all the processes and identify all the potential errors which may occur. Quality assurance procedures are then designed to prevent or minimise these errors. More details of the potential errors in each phase of the critical care testing cycle are described in the following sections of the booklet.

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Chapter I

Quality Assurance & Critical Care Testing

Major Potential Errors in Critical Care TestingPatient Post-Analysis Patient Testing Cycle Analysis Instrument not calibrated correctly Insufficient sample Unstable precision of instrument Interfering substances present

Pre-Analysis

Result not reported or report delayed Transcription error in written report No clinical details with result Critical value not highlighted

Incorrect container No or wrong anticoagulant Wrong patient or wrong identification Excessive delay before analysis

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Quality Assurance & Critical Care Testing

Chapter I

Key Aspects of Quality ManagementThere are a number of important aspects of quality management which apply universally to all parts of the critical care testing cycle. Documentation The involvement of many different people in critical care testing demands that all procedures are documented in step by step, easy to understand fashion. Guidelines for what should be contained in such documents are available from accreditation bodies and the NCCLS. Some laboratories have adopted the term Standard Operating Procedure (SOP) for such documents. They should be reviewed regularly and revised whenever changes are implemented. Training and Education Training and education assumes even greater importance when testing involves personnel who are not trained laboratory professionals. Training needs to be monitored so that new staff are incorporated into the program and the program should be revised as procedures change in response to the need for quality improvement or the development of new services. Audit and Accreditation Several countries now have fully accredited laboratory services where all laboratories are regularly inspected by an external agency and granted a license to carry out diagnostic tests. Even in those countries where accreditation is not yet established, audit procedures should exist which allow internal and external staff to regularly review diagnostic services. Such a review process should also occur when service problems are identified and need to be resolved as part of the quality planning and improvement process.8

Chapter I

Quality Assurance & Critical Care Testing

Key Aspects of Quality ManagementDocumentationAll processes associated with critical care testing should be documented

Training/ EducationAll staff carrying out critical care testing should receive regular training and education

Audit/ Accreditation

All processes associated with critical care testing should be reviewed by service users or external bodies

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Quality Assurance & Critical Care Testing

Chapter I

10

Chapter II

Pre-Analytical Quality Assurance

Chapter I I

Pre-Analytical Quality Assurance

11

Pre-Analytical Quality Assurance

Chapter II

Steps in Pre-Analytical Quality AssuranceThe pre-analytical phase of critical care testing starts with the request to perform an analysis and finishes with the introduction of the specimen into the analyser. The diagram opposite shows that several distinct stages exist in the pre-analytical process where errors can occur that will affect the patient result and this may lead to misinterpretation and incorrect treatment. While the development of testing nearer the patient has reduced the time taken to transport specimens to the instrument, there remain several manual steps where there is the potential for significant errors to occur. Thus pre-analytical variation in critical care parameters is often greater than analytical variation. The aim of pre-analytical quality assurance is to remove or minimise these sources of variation or error. A quality assurance programme should involve the following processes: i. ii. iii. Documentation of step by step procedures. Training and supervision of all people involved in pre-analytical procedures. Monitoring important pre-analytical variables such as turnaround times and the incidence of problems such as specimen errors. Identify and implement solutions for problems that occur.

iv.

The following pages will highlight the most important errors which can occur in the pre-analytical phase. For a more detailed discussion of pre-analytical quality assurance users should consult textbooks on the subject (1, 2), documents from professional bodies such as NCCLS (3-4) or IFCC (5) and the various references cited in the following pages..

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Chapter II

Pre-Analytical Quality Assurance

Steps in Pre-Analytical Quality AssurancePerformance of AnalysisPre-Analysis

Request for AnalysisCollection Device

Sample Transport

Seven steps to Pre-Analytical Quality

Anticoagulants

Sample Collection

Patient Preparation Sample Site

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Pre-Analytical Quality Assurance

Chapter II

Collection Device or ContainerThe ideal collection device for blood gas analysis would be gas tight, minimise bubble formation during sampling, have a high ratio of volume to surface area and have a plunger that requires a minimum of injection pressure. All-glass syringes are impermeable to gases so iced samples will show minimal changes after 1 - 2 hours as shown in Figure 1 opposite. In addition they require less heparin and have a low resistance plunger. The disadvantage is that they are expensive and inconvenient. Plastic syringes are inexpensive and disposable. Their disadvantage is that they are permeable to gases allowing gas tensions in the sample to move towards atmospheric pressure in the time between sampling and analysis. This is a significant problem for samples with P O2 values > 150 mmHg (Figure 1). Capillaries are available from Roche in glass or plastic and are useful for neonatal samples from the heal or from the ear in the case of adults. However to obtain a clean sample, free of bubbles, requires considerable skill. The Roche Microsampler is a disposable glass capillary device in a plastic container which has the advantages of glass and plastic devices. From the data shown in Figure 1 it can also be seen that the P O2 in an iced microsampler is stable for up to one hour. Data in Figure 1 is from dOrtho et al (6).

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Chapter II

Pre-Analytical Quality Assurance

Collection Device/Container

Glass SyringeAdvantage: No leakage of gases Low resistance plunger Disadvantages: Inconvenience Cost

Plastic SyringeAdvantage: Convenience Cost Disadvantages: Leakage of gases (P O2 > 150)

Glass or Plastic CapillaryAdvantage: Ideal for neonates Disadvantages: More demanding technique

MicrosamplerAdvantage: Convenience No leakage of gases Disadvantages: None

400 390

v

v v

v

P O2 (mmHg)

380 370 360 350 340 0 10 20

Glass Syringes Plastic Syringes

v Microsampler

30

40

50

60

70

Time (mins)Figure 1. Change in PO2 levels with time in Microsamplers, glass & plastic syringes kept at 4 C. Data from d`Ortho et al (6).

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Pre-Analytical Quality Assurance

Chapter II

Anticoagulant - which one?Almost all critical care tests require the sample to be anticoagulated. The exception is Coagulation tests which are measured on whole blood without any anticoagulant or additive. In some cases, coagulation tests may be measured on citrated (sodium citrate) blood but this will interfere with electrolyte measurements such as sodium and calcium. The best universal anticoagulant is heparin, usually the lithium salt. If this is standard, unbalanced lithium heparin then the only parameters that cannot be measured on such a sample are Coagulation tests and Lithium. Alternatives to lithium heparin include the sodium salt but the use of standard, unbalanced sodium heparin means that such samples cannot be used for sodium measurement. Note that Roche make devices containing specially formulated lithium and sodium heparins which can be used for both lithium and sodium estimations (see page 20). A number of other common anticoagulants and preservatives are used in the laboratory including flouride oxalate and EDTA, sometimes in combination. Fluoride directly interferes with glucose, lactate and urea sensors and is not suitable for critical care testing samples. Potassium EDTA binds or chelates ions, particularly calcium so that an EDTA sample will show a characteristic set of results with an undetectable or low ionised calcium and a grossly elevated potassium level.

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Chapter II

Pre-Analytical Quality Assurance

Anticoagulants Which one?NO Anticoagulant Standard Heparin Anticoagulant Other Anticoagulants eg EDTA, Oxalate Should not use for any parameters

Only for Coagulation & Lithium

For all parameters except Coagulation & Lithium

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Pre-Analytical Quality Assurance

Chapter II

Anticoagulant - which Heparin ?Liquid heparin is usually supplied as the lithium salt at a concentration of 1000 IU/l. Only 50l of this solution is required to anticoagulate a 1ml blood sample and this volume is easily mixed with the sample. The main disadvantage of liquid heparin is that it dilutes all the parameters 50l in 1ml corresponds to a 5% dilution. Unfortunately more than this volume is often drawn up into the syringe and the excess is not evacuated after coating the walls of the syringe. In such cases significant dilution of parameters can occur as shown in Figure 2 opposite. The data in Figure 2 indicates that if heparin makes up 10% or more of the total blood gas sample, there will be significant decreases in the measurement of P CO2 and also bicarbonate and base excess. The data shown is from Hutchison et al who also showed that significant errors in diagnosis and treatment could occur from the results obtained on samples containing excessive heparin (7). To overcome this problem for those who wish to continue using liquid heparin, Roche supply a syringe with a limited volume of liquid heparin which avoids dilution problems.

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Chapter II

Pre-Analytical Quality Assurance

Anticoagulants Which Lithium Heparin?Liquid Heparin Dry Heparin Dry, Balanced HeparinAdvantage: No dilution effects No chelation of ions Disadvantages: None

Advantage: Easy to dissolve

Advantage: Avoids dilution problems Disadvantages: Chelation of ions

Disadvantages: Dilution effects Chelation of ions

60 50

% Change in P CO2

40 30 20 10 0 0 10 20 30 40 50 60

% Heparin in SampleFigure 2. Effects of excess heparin on PCO2 levels. Data from Hutchison et al (7).

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Pre-Analytical Quality Assurance

Chapter II

Anticoagulant - which Heparin ?Another solution to overcome the problem with dilution due to excessive liquid heparin, has been for manufacturers of collection devices including Roche, to also supply syringes, capillaries or microsamplers with dry, lyophilised heparin included in the device. Dry heparin avoids dilution problems, but needs more mixing to ensure that it is dissolved. However an additional problem with standard heparin, whether liquid or dry, is that it binds electrolytes, particularly calcium. Figure 3 opposite shows the decrease in ionised calcium levels due to standard dry heparin, which causes a significant decrease of 0.08 mmol/l in Ca++, even with the minimum anticoagulant requirement of 50l of standard heparin per ml of sample. Larger amounts of heparin cause a corresponding greater decrease in Ca++. Data from MllerPlathe et al (8). The problem associated with binding of electrolytes by heparin can be overcome by using a specially formulated electrolyte-balanced heparin. Figure 4 opposite shows the ionised calcium results from capillaries containing balanced heparin compared to reference levels of ionised calcium. While there is a difference between the two sets of results, the differences are clinically insignificant. Data from Sachs et al (9). All Roche syringes, capillaries and Microsamplers contain electrolyte-balanced heparin which avoids the problems of excessive dilution of all parameters and binding of certain electrolyte parameters.

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Chapter II

Pre-Analytical Quality Assurance

Decrease in Ion Ca++ (mmol/l)

0.00 0.050.08

0.10 0.15 0.20 0.25 0.30 0 20 4050

60

80

100 120 140 160 180 200

Heparin (lU/ml)Figure 3. Effects of unbalanced dry heparin on ionised Ca++ levels. Data from Mller-Plathe et al (8).

Roche capillary Ion Ca++ (mmol/l)

3 2.5 2 % deviation 0 % 1.5 % deviation + 0.9 % 1 % deviation + 6.4 % 0.5 0 0 0.5 1 1.5 2 2.5 3 % deviation - 2.3 %

Reference Ion Ca++ (mmol/l)Figure 4. Ionised Ca++ levels in balanced heparin capillaries compared to reference levels. Data from Sachs et al (9).

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Pre-Analytical Quality Assurance

Chapter II

Patient PreparationBefore taking the blood sample consideration should be given to the clinical condition of the patient. Relatively steady states in blood gases occur quicker in healthy individuals than in patients with disease. Thus even spontaneously breathing patients should rest for 5 mins before the blood sample is collected. Many critical care testing samples are taken from patients who are receiving treatment. Depending upon the urgency to make measurements, appropriate times should be allowed for a steady state to be achieved after a treatment change and before sampling. For example: After intubating a patient, allow 20 min before sampling. When weaning a patient from a ventilator, allow 10 min before sampling. Taking an arterial blood sample can be a painful and stressful procedure resulting in undue patient anxiety. This anxiety can cause hyperventilation and affect the blood gas and pH results. Typical results in such a situation will be a lower than expected P CO2 and increased pH. Such results, which are not due to any pathological process, may cause misdiagnosis and the wrong treatment. Good blood collection techniques by highly trained and skilled staff can avoid this problem and are discussed in more detail on Page 26.

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Chapter II

Pre-Analytical Quality Assurance

Patient PreparationRestTreatment Equilibrium

Anxiety

Spontaneously breathing patients should rest 5 min before sampling

Allow appropriate time after treatment changes before sampling

Avoid pain and anxiety to prevent effects on steady state of respiration

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Pre-Analytical Quality Assurance

Chapter II

Sample SiteArterial samples are by far the most common sample for critical care testing because only arterial blood gives a true indication of oxygenation and acid-base status. Arterial blood also has the advantage that its composition does not change from the aorta to the peripheral circulation. Thus a variety of sites can be used for sampling (see Figure 5) but the commonest sampling sites are the radial or femoral arteries. In some cases arterialised capillary blood can be used as a substitute for arterial blood. This is most often used in the case of premature babies and neonates when the sample is usually taken from the heel. Capillary samples can provide similar values to arterial blood for all parameters except oxygenation, where significant differences may exist between arterial and capillary P O2. This difference can be reduced by arterialisation or warming the vasculature prior to sampling (see Page 26). Peripheral venous samples may be used for certain critical care parameters such as electrolytes, coagulation tests, glucose and cardiac markers. Peripheral venous blood is not suitable for special oxygenation parameters such as mixed venous P O2 which are used to calculate additional parameters such as arterio-venous oxygen difference. Mixed venous P O2 requires sampling from a catheter in the pulmonary artery. Repeated sampling from an artery or vein is best provided via an in-dwelling catheter.

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Chapter II

Pre-Analytical Quality Assurance

Sample Site

Artery

Capillary

Vein

Catheter/ Cannula

Most common sampling site Can be used for all critical care parameters

Often used in neonates Requires arterialisation to give correct P O2 results

Used to assess shunts Peripheral blood not suitable for oxygenation parameters

Cannula convenient for multiple samples Catheters used for mixed venous samples

Sample Site

Axilary artery Brachial artery Ulnar artery Radial artery

Femoral artery

Dorsalis pedis artery

Figure 5. Preferred sites of the radial, brachial and femoral arteries for arterial blood sampling

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Pre-Analytical Quality Assurance

Chapter II

Sample CollectionCollection of blood is a specialised technique which requires considerable training and skill. Only the most important requirements will be mentioned here and users must consult the documented collection procedures in their own institution for more details. The most important requirement is that all samples must be collected in a way that minimises discomfort and trauma to the patient. This is particularly important in the case of arterial samples where access to arterial blood can sometimes be difficult. Other important requirements for arterial sampling are avoiding contamination with air and venous blood. If capillary sampling is required, the heel or ear must be warmed prior to collection in order to dilate the arterioles and achieve a degree of arterialisation. The higher the degree of arterialisation, the closer should be the agreement between capillary and arterial P O2 but there is controversy in the literature about whether arterialised capillary blood is a satisfactory substitute for arterial blood (2). Figure 6 illustrates the techniques for collecting blood from the heel in the case of the neonate or the ear for adults. For capillary samples avoiding contamination of the sample with ambient air can be difficult but can be facilitated by keeping the capillary close to the puncture site. When the capillary is full and depending upon its size, the use of a metal flea may be required to ensure mixing of the sample with the heparin. Sampling from peripheral veins should avoid venous occlusion for longer than 2 mins.

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Chapter II

Pre-Analytical Quality Assurance

Sample CollectionAvoid pain, trauma and contamination with air

ArteryAvoid contamination with venous blood

CapillaryRequires warming to achieve arterialisation

VeinAvoid venous occlusion

Catheter/ CannulaAvoid contamination with flush fluid

Expel air, Mix, Label

Sample Collection

(a)

(b)

Figure 6. Sites of arterialised capillary sampling from the ear lobe (a) and the heel (b)

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Pre-Analytical Quality Assurance

Chapter II

Sample CollectionWhen sampling from an in-dwelling cannula or catheter, care must be taken to ensure that this is purged of flush solution before sampling blood. Figure 7 shows the effect on haematocrit and pH results when insufficient volume is flushed or discarded before taking a sample for analysis. The effect in both cases is significantly lower results due to dilution of the blood with flush solution. The volume that needs to be discarded should be determined for individual cannulas and catheters. Data from Dennis et al (10). When a conventional syringe is used, once collection is complete, it is vital to dispose of the needle safely according to documented procedures. Air bubbles must be removed from the collection device prior to transport. Such bubbles will affect both the P O2 and P CO2 but the effects on P O2 are greater and an example of these is shown in Figure 8 opposite. Generally the effects are proportional to the size of the air bubble and increase in proportion to the length of time that the air bubble is in place. Data from Biswas et al (11). The placement of analysers nearer to the patient with consequent reductions in the time between collection and analysis has reduced this problem but good collection technique should still include removal of all significant air bubbles immediately after collection. Finally it is important to mix the sample to ensure that it is anticoagulated and it must be labelled clearly by hand or with a barcode containing the patient details.

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Chapter II

Pre-Analytical Quality Assurance

True result

40 35 30 Haematocrit pH

7.60 7.40 7.20 7.00 6.80 6.60 6.40 6.20 6.00

Haematocrit

25 20 15 10 5 0 0-2 2-4 4-6 6-8 8-10 10-12

Aliquot VolumeFigure 7. Effects on pH & Hct of contamination with flush solution Data from Dennis et al (10 ).Page 1

18 1610 % air bubble 20 % air bubble

% Increase in PO2

14 12 10 8 6 4 2 0 0

1

2

3

4

5

Time (mins)Figure 8. Effects on P O2 levels of contamination with air. Data from Biswas et al (11).

pH

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Pre-Analytical Quality Assurance

Chapter II

Sample Treatment and Transport Effect on PO2Many critical care parameters are labile and analysis should be completed as soon as possible after sample collection. If there is a significant delay in analysis, the major changes which can occur in a whole blood sample left at room temperature are as follows: The presence of air bubbles and permeability of plastic to gases leads to gas changes (see Figure 1). Metabolism of blood cells leads to changes in pH, gases and metabolites. Leakage of electrolytes, particularly potassium, from cells into plasma, leads to spuriously increased potassium levels. Figure 9 opposite shows the effects of metabolism on P O2 levels in samples collected in glass Microsamplers, one group kept at ambient temperature and the other group kept at 4 C; the original P O2 level was 390 mmHg (50 kPa). The use of glass collection devices minimises any changes in P O2 level due to the diffusion effects which take place in plastic devices (see Figure 1). The changes after 15 mins in both samples are not significant but after 30 mins, the fall in the P O2 levels of uncooled samples are significant and reflect the metabolism of blood cells. However these changes can be prevented if the syringe is cooled with ice. These metabolic effects are insignificant at P O2 levels below 150 mmHg and such samples do not need to be cooled for up to one hour after collection. Data from dOrtho et al (6).

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Chapter II

Pre-Analytical Quality Assurance

Sample Treatment & Transport

Analysis