BLOOD GAS - AACB

BLOOD GAS (ARTERIAL AND VENOUS

Gus Koerbin

Adjunct Professor, University Of Canberra, Faculty of Health

Visiting Fellow, ANU, College of Health and Medicine

AACB Harmonisation meeting 10-11 May 2018, Sydney

WHAT ARE WE GOING TO DISCUSS?

• Gus Koerbin • Introduction and some recapping of 2017

• Roger Ashton • ABG • The New Zealand data

• Gus Koerbin • Australian ABG flagging rates

• Rita Horvath • VBG • The NSW Health Pathology experience

• Gus Koerbin • Some additional venous data • Summary


Some introductory questions


Some introductory questions

• Question 1

• Who has VBG reference intervals?

• Question 2

• Who has different ABG and VBG reference intervals?

• Question 3

• Is it appropriate to report Arterial intervals for venous gases?


What are we going to work through today?

• Is there enough data to decide whether to harmonise RI?

• What are the flagging rates?

• Are the RI that will be discussed suitable ?

• We will not discuss all the analytes that are produced when a blood gas is requested but concentrate on a few such as:

• pH,

• pCO2

• pO2

• bicarb,

• iCa,


Is there any instrument related reason not to harmonise a group of analytes?

• Ideally we would use a bias study using commutable material (Human) • Is this feasible?

• Is it possible?

• RCPA QAP • Not human material

• But does give us an idea of how instruments perform relative to each other

• Consider pH, pCO2, pO2 and iCa


Recap of 2017

• RCPA QAP

• Survey of labs and industry arterial RI’s


pH ARTERIAL > 18 Y Possible RI RADIOMETER ISTAT IL SIEMENS

RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

pH 7.35-7.45 7.35-7.45 7.35-7.45 7.35 - 7.45 7.35-7.45 7.35-7.45 7.35 - 7.45 7.34 - 7.44 7.35-7.45 7.35-7.43 7.35-7.45 7.36-7.44

pCO2 ARTERIAL > 18 Y Possible RI RADIOMETER ISTAT IL

SIEMENS RAPIDLAB

PATH QLD (all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

PCO2 [mmHg] 35-45 35-48 (M) 32-45 (F)

35-45 35 - 45 35-45 32-48 35-45 35-45 35-45 32-45 35-45 35-45

pO2 ARTERIAL > 18 Y Possible RI RADIOMETER ISTAT IL SIEMENS

RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

PO2 [mmHg] 83-108 83-108 80-105 75 - 100 80-100 83-108 75 - 100 75 - 100 75 - 100 69-116 80-105 80-100

iCa ARTERIAL > 18 Y Possible RI RADIOMETER ISTAT IL

SIEMENS RAPIDLAB

PATH QLD (all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

iCa++ [mmol/L] 1.15-1.30 1.15-1.29 1.12-1.32 1.15 - 1.32 1.1-1.4 1.15-1.32 1.12 - 1.30 1.04 - 1.24 1.15-1.30 1.1-1.3 1.12-1.32 1.15-1.29

Arterial Blood Gas

• We have seen some of the NSW data last year and it was based on survey results. • Note: This has been updated in 2018 after consultation

• NSW Reference intervals – by consensus

• ABG state of the art, flag rates 10-20% (later) • Ken Sikaris has produced some Melbourne Pathology 2011-2017 flag rates

differences


Venous Blood Gas

• In NSW in some instances there were no VBG RI’s • caused incidents in NSW

• Is it better to have something that is OK than nothing at all

• ISO requirements: • must have some way of interpreting (not necessarily RI)

but you must have soothing to support the interpretation.

• Some more VBG flagging rates


Over to Roger


Arterial blood gas (Flagging rates)

Gus Koerbin




Flagging rates

• Excess flagging of results can lead to inappropriate testing due to decreased specificity of the RI.

• The flagging rates provided in this review are those when community samples are considered.



Arterial (>19 years) RI Source pH 7.35-7.45 Consensus decision (Clinical Streams members)

PO2 [mmHg] 75-105 Consensus decision (Clinical Streams members)

PCO2 [mmHg] 35-45 Consensus decision (Clinical Streams members)

HCO3- [mmol/L] 22-28 Consensus decision (Clinical Streams members) APUTS, QLD RI

NSW Health Pathology Agreed ABG Reference Interval

Arterial (>19 years) RI AACB/RCPA Source

Electrolytes: Sodium [mmol/L] 136-146 135-145 Consensus decision (Clinical Streams members) APUTS

Potassium [mmol/L] 3.7-4.7 3.5-5.2 Consensus decision (Clinical Streams members) APUTS

Chloride [mmol/L] 101-110 95-110 Consensus decision (Clinical Streams members) APUTS

Ionised Ca++ [mmol/L] 1.15-1.30 Consensus decision (Clinical Streams members)

BGAS Database (Melbourne Pathology) 2001-2017

Art Ven Ven% Total

DanEmerg 1,888 262 12.2% 2,150

DanICUf 32,054 1,045 3.3% 32,054

DanICUm 37,659 947 2.5% 37,659

EpwEmerg 871 8 0.9% 871

EpwICU 29,519 0 0.0% 29,519

FreeCCU 57,593 3,215 5.6% 57,593

FreeICU 43,514 109 0.3% 43,514

OutPat 5,317 39 0.7% 5,317

Ward 27,435 81 0.3% 27,435

All 235,850 5,706 2.4% 236,112 Courtesy K.Sikaris


Location (Sick) Melbourne Pathology: 2001-17

Courtesy K.Sikaris


Median Age = 71 y/o (Old)

Courtesy K.Sikaris

Art pH Distributions Outpatients have much tighter pH distribution. Less acidosis than hospital patients

Courtesy K.Sikaris

Art pH Cumulative (Flag Rate)

7.35-7.45 gives 10% flag rate in OP, but 30% flag rate for acidosis in inpatients Alkalosis flag rate is the same in IP and OP – around 10% (NZ,NSW ABG RI – red dashed lines)

ARTERIAL > 18 Y Possible RI RADIOMETER ISTAT IL SIEMENS

RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

pH 7.35-7.45 7.35-7.45 7.35-7.45 7.35 - 7.45 7.35-7.45 7.35-7.45 7.35 - 7.45 7.34 - 7.44 7.35-7.45 7.35-7.43 7.35-7.45 7.36-7.44

Courtesy K.Sikaris

Art pCO2 Distributions pCO2 distributions similar in IP and OP

Courtesy K.Sikaris

Art pCO2 Cumulative (Flag Rate)

pCO2 flag rate is much higher using 35-45 mmHg 15% for resp alkalosis and 25% for resp acidosis (NZ,NSW ABG RI – red dashed lines)


RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

PCO2 [mmHg] 35-45 35-48 (M) 32-45 (F)

35-45 35 - 45 35-45 32-48 35-45 35-45 35-45 32-45 35-45 35-45

Courtesy K.Sikaris

Art pO2 Distributions

pO2 distribution shows biphasic distribution with probable contamination from venous samples Very few samples lie between 80-100 mmHg in IP or OP

Courtesy K.Sikaris

Art pO2 Cumulative (Flag Rate)

Flag Rate for arterial pO2 is 60% for lower limit (80mmHg) and around 10% for upper limit in OP Much higher high pO2 flags in IP (>50%) due to oxygen and assisted ventilation (NZ,NSW ABG RI – red dashed lines)


RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

PO2 [mmHg] 83-108 83-108 80-105 75 - 100 80-100 83-108 75 - 100 75 - 100 75 - 100 69-116 80-105 80-100

Courtesy K.Sikaris

Art iCa Distributions Ionised calcium shows broad distribution.

Courtesy K.Sikaris

Art iCa Cumulative (Flag Rate)


RAPIDLAB PATH QLD

(all devices)

Pathology North

Radiometer ISTAT

Pathology North GEM

Pathology West

Radiometer, ISTAT

SEALS Radiometer

SEALS ISTAT

SSWPS Radiometer,

Siemens iSTAT

iCa++ [mmol/L] 1.15-1.30 1.15-1.29 1.12-1.32 1.15 - 1.32 1.1-1.4 1.15-1.32 1.12 - 1.30 1.04 - 1.24 1.15-1.30 1.1-1.3 1.12-1.32 1.15-1.29

Flag Rate using 1.10 – 1.25 would be 30% at LRL and 5% at URL (NZ,NSW ABG RI – red dashed lines)

Courtesy K.Sikaris

Art SBIC Distributions SBIC is lower in inpatients (appropriate?)

Courtesy K.Sikaris

Art SBIC Cumulative (Flag Rate)

Flag rate for metabolic acidosis using 22 mmol/L cutoff is 10% for OP and 25% in inpatients Flag Rate for metabolic alkalosis is 15% for OP and <10% in inpatients. (NZ,NSW ABG RI – red dashed lines)

Courtesy K.Sikaris

• How are the ABG RI’s used • diagnosis and monitoring (sick people – not

surprised at high flag rates)

• not used for screening generally

• what is the cut off with flag rates – what is the clinical response to the gas result?

• Who can contribute • What is the ideal clinician group

• Respiratory, ED.

• Clinical decision points may be different to the RI Interpreted as part of a pattern • don’t interpret pCO2 without pH and bicarbonate


What now?

• Roger has presented the New Zealand ABG data

• We have seen some of the NSW data last year based on survey results.

• ABG state of the art, flag rates 10-20% or greater • Melbourne Pathology 2011-2017 flag rates differences

• NSW Reference intervals – by consensus

• For Discussion

NZ and NSW ABG RI’s are now the same

Are these values candidates for harmonised RI’s?


VENOUS BLOOD GAS

Gus Koerbin




WHAT ARE WE GOING TO DISCUSS?

• Some additional venous data

• New Zealand and NSW VBG RI • pH: 7.3-7.4

• pCO2: 40-50 mmHg

• Bicarbonate: 22-28 mmol/L

• iCa: 1.15-1.30 mmol/L

• Summary


BGAS Database 2001-2017

Art Ven Ven% Total

DanEmerg 1,888 262 12.2% 2,150

DanICUf 32,054 1,045 3.3% 32,054

DanICUm 37,659 947 2.5% 37,659

EpwEmerg 871 8 0.9% 871

EpwICU 29,519 0 0.0% 29,519

FreeCCU 57,593 3,215 5.6% 57,593

FreeICU 43,514 109 0.3% 43,514

OutPat 5,317 39 0.7% 5,317

Ward 27,435 81 0.3% 27,435

All 235,850 5,706 2.4% 236,112

Courtesy K.Sikaris

Venous pH Cumulative (Flag Rate)

Insufficient Outpatient venous data for pH distribution. 60% flag rate at 7.35 (ABG LRL) for venous OP gases Red dashed lines NZ/NSWHP VBG RI: 7.30-7.40 Green dashed lines NSW RI study: 7.29-7.41

Courtesy K.Sikaris

Venous pCO2 Cumulative (Flag Rate)

If using the same 35 – 45 mmHg limits, the resp acidosis flag rate would increase from 25% (arterial) to 45% (venous) To maintain a similar rate rate to arterial flag rate (25%), the upper pCO2 limit would need to be increase from 45 to 50. Conversely, to maintain arterial resp alkalosis arterial flag rate (15%), the lower limit would need to increase from 35 to about 37 mmHg.

Red dashed lines NZ/NSWHP VBG RI: 40-50 mmHg Green dashed lines NSW RI study: 38-61 mmHg

Courtesy K.Sikaris

Venous pO2 Cumulative (Flag Rate)

Flag Rate for 25-55 mmHg would be about 10% at each end. NZ/NSWHP VBG RI: N/A Green dashed lines NSW RI study:15-64 mmHg

Courtesy K.Sikaris

Venous SBIC Cumulative (Flag Rate)

Flag Rate for metabolic acidosis will increase from 10% to 20% is using the same cut-off for venous as arterial. Red dashed lines NZ/NSWHP VBG RI: 22-28 mmol/L (=HRI for plasma) Green dashed lines NZ/NSW RI study: 22-32 mmol/L

Courtesy K.Sikaris

VBG Reference Interval Study on Radiometer ABL800 series analysers (NSW Health Pathology, Prince of Wales Hospital)

Dixon-Reed

(Non-Para)

Flagging rate (Melbourne

Pathology patients)

pH 7.29 – 7.41 ~ 10% at both limits

pO2 15 - 64 <5%

pCO2 38 – 61 15% LRL, 10% URL

Bicard 23.4 – 30.8 ~5% at both limits

iCa 1.16 – 1.32 20% LRL, <5% URL


Courtesy R Horvath

Summary – where to now?

• Are there any significant method differences?

• CLSI: • if population and analysers similar then can adopt harmonised RI’s

• Venous • Is it better to have some reference intervals that are venous specific, than none at all or using

inappropriate arterial RI’s?

• How much more work needs to be done for adoption of harmonised RI’s (venous and arterial)? • Have we got enough data to suggest RI’s for some analytes undertaken in ABG analysis?

Are the NZ/NSW ABG and VBG reference intervals suitable as candidates for harmonised RI’s


BLOOD GAS - AACB

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