acid base balance and arterial blood gas analysis

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Acid Base Balance and

Arterial Blood Gas Analysis

Gail Ross-Adjie

Emergency Nurse Educator

[email protected] All rights reserved. Except as

permitted under the Australian

Copyright Act !"# no part o$ the

attached material may %e

reproduced& stored in a retrieva%le

system& communicated or

transmitted in any $orm or %y any

means 'ithout o%taining the prior

'ritten permission o$ Gail Ross-

Adjie at [email protected]

mailto:[email protected]

mailto:[email protected]



Acid Base Balance

(verall acid-%ase %alance ismaintained %y controlling hydrogen

)*+, ion concentration p* is a measure o$ *+ concentration

and sho's the %loods acidity

al/alinity Complex mechanisms ensuremaintenance o$ the 0normal values



Normal Arterial Blood Gas

1alues

p* 2.34 5 2.64

p(7 )oxygen, #8 5 88 mm*g

pC(7 )car%on dioxide, 34 5 64 mm*g

*C(3 )%icar%onate, 77 5 7# mE9:l



ABG ;ites

<rom an arterial line i$ the patient has one (ther'ise $rom

Radial Brachial or <emoral artery

Apply $irm pressure to site $or 4 mins

=ade sure the re9uest $orm states 'hetherthe patient is %reathing room air orsupplemental (7 )either mas/ or ventilator,



>aC(7 re$lects ho' 'ell the %ody is

eliminating C(7

>a(7 re$lects ho' 'ell the %ody is

pic/ing up oxygen $rom the lungs

*C(3 re$lects the /idneys a%ility to

retain and excrete *C(3



E$$ect o$ p*

p* ? 2 causes depression o$ the

central nervous system )CN;, leading

to con$usion and coma >h 2." causes excita%ility o$ the CN;

leading to tremor& muscle spasm and

convulsions



Acidosis

ndicated %y a %lood p* value less

than 2.34

=ay go as lo' as ".#8



Al/alosis

ndicated %y a %lood p* value more

than 2.64

=ay go as high as #.88



Acidosis

'o types Respiratory acidosis

=eta%olic acidosis



Al/alosis

'o types Respiratory al/alosis

=eta%olic al/alosis



Causes

*ypoventilation o$ten 7 head injury or

overdose causing dro'siness

>ulmonary oedema

Respiratory arrest



reatment

reatment is aimed at increasing the

exhalation o$ C(7

=ay re9uire intu%ation ventilation

$ already ventilated& increase

respiratory rate

;uction the air'ay i$ excessive

secretions



Respiratory Al/alosis

)excess C(7 excretion,

Caused %y a decrease in pC(7

p* 2.64

pC(7 ? 34

*C(3 ? 77 mE9:l



Causes

*yperventilation usually due to anxiety or pain

RR too high on the ventilator =ay present 'ith spasm in $ingers Respiratory stimulation $rom

*ead injury

*ypoxia <ever ;ome drugs



reatment

Aim is to increase the pC(7

Get patient to %reath into a paper %ag

)re-inhaling their o'n C(7,

$ ventilated& D RR

<ix underlying cause



=eta%olic Acidosis)*C(3 loss or acid retention,

Caused %y an increase in acidic

meta%olic products )eg. /etones, and

a D in *C(3 p* ? 2.34

pC(7 ? 34

*C(3 ? 77mE9:l



Causes

Renal $ailure

*C(3 loss $rom diarrhoea

ia%etic /etoacidosis )FA,

;tarvation

ngestion o$ acid



reatment

Correct the underlying cause se o$ 1 *C(3 is controversial and

does not sho' any %ene$it in those'ith FA )Cooper cited in unn& 7888& p. 7"6,



=eta%olic Al/alosis)*C(3 retention& acid loss,

Caused %y an excess o$ *C(3 in the

%ody or a D in gastric acid

p* 2.64

*C(3 7" mE9:l



Causes

Caused %y a loss o$ acid in the %ody or

a high inta/e o$ al/alis

sually a result o$ excessive vomitingleading to a D in gastric acid or a high

inta/e o$ al/ali medicines )antacids,

Excessive gastric suctioning



reatment

reat the underlying cause



So…

$ p* ? 2.34 the patient has an acidosis

$ p* 2.64 the patient has an al/alosis

he pro%lem is meta%olic i$ *C(3 is

a%normal

he pro%lem is respiratory i$ the C(7 is

a%normal



;teps involved in analyHing

ABGs

. s the p* normalI

7. s the C(7 normalI

3. s the *C(3 normalI



Examples

37yo male motor%i/e rider hit %y car. No

helmet. GC; # on arrival to E. ABGJsK

p* 2.78 p(7 28 mm*g

pC(7 8 mm*g

Lhat is 'rong and ho' could 'e correct itI



6 yo girl 'ith 7 day history o$ diarrhoea

and vomiting. ABGsK

p* 2.48 p(7 !4

pC(7 68

*C(3 7! mE9:l



7# yo 'oman presents complaining o$

severe a%dominal pain and spasm in

her $ingers. ;he is anxious ++ p* 2.44

pC(7 7"

p(7 !"

*C(3 7 mE9:l



67 yo male is %ought in %y his $amily 'ith ahistory o$ insulin dependent dia%etes. *e isdro'sy and complains o$ a%dominal pain&excessive thirst and urination. *is B;M iselevated. ABGsK

p* 2.#

*C(3 ! p(7 "8 pC(7 ""



Re$erences

Respiratory Care Made Incredibly Easy . )7884,. >hiladelphiaKMippincott Lilliams Lil/ins.

unn& R. )7888,. Ma%oratory =edicine. n R. unn )Ed.,& The

Emergency Medicine Manual )7nd ed.,. AdelaideK 1enom.

=iller& . .& Munde& . R. )7883,. Ma%oratory ;pecimen Collection.n M. Ne'%erry )Ed.,& Sheehy's Emergency Nursing Principles andPractice )4th ed.,. ;t MouisK =os%y.

ortora& G. .& Anagnosta/os& N. >. )!!,. Principles of natomyand Physiology )6th ed.,. Ne' Oor/K *arper Ro'.

Lest& . B. )7884,. Respiratory Physiology! The Essentials )2th ed.,.>hiladelphiaK Mippincott& Lilliams Lil/ins.

acid base balance and arterial blood gas analysis

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