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Bloedgas	Workshop 		 Laura Kater Bloedgas	Workshop 		 Laura Kater

Bloedgas Workshop Laura Kater - PowerPoint Presentation

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Bloedgas Workshop Laura Kater - PPT Presentation

Emergency Physician Rode Kruis Ziekenhuis Beverwijk ROD 17012013 What will we discuss Warming up Aa gradient Arterial ID: 785014

venous pao2 gradient arterial pao2 venous arterial gradient abg mmhg pco2 clinical po2 blood agreement gas bic difference sat

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Slide1

Slide2

Bloedgas Workshop

Laura Kater

Emergency

Physician

Rode Kruis Ziekenhuis, Beverwijk

ROD

17.01.2013

Slide3

What will we discussWarming up

Aa gradient

Arterial

vs

venous

blood gas

Slide4

1kPa = 7.5 mmHg

Slide5

Warming up

Slide6

35 yo femaleDyspneaFiO2 100%

ABG: pH 6.76

pCO2 72

Bic 10

BE -26.0

pO2 24 Sat 94

Slide7

31 yo maleDyspneaFiO2 100%ABG:

pH 6.72 pCO2 87

Bic 11

BE -28.7

pO2 301

Sat

97

Slide8

94 yo femaleDyspneaFiO2 4

ltr O2 = ongeveer 30%?

ABG:

pH 7.15

pCO2 55

Bic 19

BE -10.2

pO2 62 Sat 83

Slide9

Aa

Gradient

Slide10

Aa gradient = alveolar minus arterial

oxygen pressure

pAO2 – paO2

Slide11

pAO2: calculationpaO2: measurement in arterial

blood gas

Slide12

Why is this important?

Slide13

pAO2pAO2 (mmHg) = 7x %O2 – paCO2 – 10So at room air

: 7x21 – 40 – 10 = 97 mmHg

Slide14

Example65 yo, room air (FiO2 21%) ABG 7.44 / 29 / 88 / 19 / -3 / 95

%

pAO2 =

7x21 – 29 – 10 =

108

mmHg

paO2

in ABG = 88 mmHg

Difference = Aa gradient = 20 mmHg

Slide15

Is that normal???

Slide16

Aa gradientAa max = age / 3 + pAO2 / 5 – 23

Our pt

: 65

/ 3 + 108 / 5 – 23

=

21.67

+ 21.6 – 23 = 20.27Calculated gradient was 20.

Slide17

Another one 61 yo, FiO2 30%

ABG 7.02 / 22 / 146 / 6 / -24 / 98%

pAO2

= 7x30 – 22 – 10 = 178

mmHg

paO2

= 146

Aa gradient = 32 Aa max for

this age: 61/3 + 178/5 – 23 = 20.3 + 35.6 – 23 = 32.9Conclusion: normal

Aa

gradient

Slide18

En nu?30 yo, non rebreather (FiO2 +/-80%)

ABG: 7.40 / 40 / … / 25 / 0 / 100%What

pO2 do

you

expect

?

pAO2 = 7x80 – 40 – 10 = 510 mmHgMax Aa gradient =

30/3 + 510 / 5 – 23 = 10 + 102 – 23 = 89Expected paO2 in ABG is about 421 mmHg

Slide19

Last…74 yo, room airABG: 7.42 / 39 / 62 / 25 / 1 / 90%pAO2

= 7x21 – 39 – 10 = 98 mmHg

paO2

=

62

Aa

gradient = 36Aa max = 74/3 + 98/5 – 23 = 24.7 + 19.6 – 23

= 21Aa gradient 15 mmHg to high = low paO2 Pulm.problem?, shunt / VQ mismatch?

Slide20

Lifeinthefastlane.com

Slide21

Arterial

or

Venous

Slide22

Use

bloodgas

in

ED

acid-base

status

pH, bicarbonaatrespiratory functionpCO2, sometimes pO2

Slide23

Why venous?Painful arterial

punction

Hematoma

after

art.punction

Easy to sample a

venous one when you’re already drawing blood for standard labs

Slide24

BUTIs a venous bloodgas clinical

equivalent

to

arterial

?????

Slide25

EMRAP

june

2008

summarizes

a few

publications

:

(www.emrap.org)

Slide26

A few

publications

in:

Annals of EM april 1998

In diabetic ketoacidosis in adults the venous blood gas measurements accurately demonstrate the degree

of acidosis.

Mean

difference

between

arterial

and

venous

pH was 0.03 (range 0.0-0.11

)

Slide27

EM Journal sept 2001

strong

correlation

between

arterial and venous pH, difference 0.4.

Slide28

Journal

EM jan

2002

Very

good

agreement in pH

with

venous samples being -/-34 units lower than arterial samples. pCO2 on average 5.8 mmHg higher in venous

samples

Slide29

Canadian Journal EM 2002

pH art

an

venous

difference

0.36

pCO2 6 mmHgHCO3- 1.5

Slide30

Annals

of EM 2005

very

good

correlation

between arterial and venous pH and HCO3-

Slide31

EM

Australasia

feb 2006

in

pts

with

DKA the

weighted average differences between arterial and venous

pH was 0.02

bic -1.88

Slide32

For details look at the studies

Slide33

Resus.meCliff Reid:

Slide34

Professor

Anne-

Maree

Kelly,

June

2009

pH

- Close enough agreement for clinical purposes in DKA, isolated metabolic disease; more

work

needed

in shock, mixed

disease

Bicarbonate

-

Close

enough

agreement

for

clinical

purposes

in most cases; more

work

needed

in shock, mixed

disease

,

calculated

vs

measured

gap

pCO2 –

NOT

enough

agreement

for

clinical

purposes

;

potential

as a screening test

Base

excess

Insufficient

data

Slide35

Lim

and

Kelly

Eur

J of EM 2010

Available evidence suggests that there is good agreement for pH and HCO3 values between arterial

and

pVBG

results

in

patients

with

COPD, but

not

for

pO2 or pCO2.

Widespread

clinical

use

is

limited

because

of the

lack

of

validation

studies on

clinical

outcomes

Slide36

Questions

???

Slide37

Slide38

Take home

message

When

in

doubt

of a

pulmonary

problem causing hypoxia, use the Aa gradient to calculate if the oxygen you

give

your

patiënt

correlates

with

the paO2 in the ABG

Think

before

you

ask

for

an

ABG.

What

do

you

need

to

know

,

will

a

venous

blood

gas do?

When

in

need

of

an

ABG:

local

anesthesia

.

Slide39

Thank

you

!