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Arterial Blood Gas Analysis

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What is an ABG?

•  The Components• pH / PaCO2 / PaO2 / HCO3 / O2sat / BE

• Desired Ranes• pH ! "#3$ ! "#%$

• PaCO2 ! 3$!%$ mmH

• PaO2 ! &'!('' mmH

• HCO3 ! 2(!2"• O2sat ! )$!(''*

• Base E+,ess ! -/!2 mE./

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Why Order an ABG?

• Aids in esta0lishin a dianosis

• Helps 1ide treatment plan

• Aids in entilator manaement• mproement in a,id/0ase manaement

allo4s 5or optimal 51n,tion o5medi,ations

• A,id/0ase stat1s may alter ele,trolyteleels ,riti,al to patient stat1s/,are

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oisti,s

• When to order an arterial line !!• 6eed 5or ,ontin1o1s BP monitorin

• 6eed 5or m1ltiple ABGs• Where to pla,e !! the options• Radial

• 7emoral

• Bra,hial• Dorsalis Pedis

• A+illary

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A,id Base Balan,e

•  The 0ody prod1,es a,ids daily• ($8''' mmol CO2

• $'!('' mE. 6onolatile a,ids

•  The l1ns and 9idneys attempt to

maintain 0alan,e

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A,id Base Balan,e

• Assessment o5 stat1s ia0i,ar0onate!,ar0on dio+ide 01:er

system

• CO2 + H2O <--> H2CO3 <--> HCO3- + H+

• ph = 6.10 + log ([HCO3] / [0.03 x PCO2])

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 The Terms

•  ACID

•  A!"#$%"&

•  A!"#o'"'• $'p"&*o

  ↑CO2

• ,$*&ol"!

  ↓HCO3

• A

•  Al&l$%"&

•  Al&lo'"'• $'p"&*o

  ↓CO2

• ,$*&ol"!

  ↑HCO3

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Step One - Assessing pH

oo &* pH &# #$*$%"$ " "* "' acidotic 

(<4.35) normal (4.35 - 4.75) o alkalotic 

(> 4.75).

pH "' *h$ $'* o8$&ll "#"!&*o "

#$*$%""g *h$ &!"#-&'$ '*&*9' o *h$p&*"$*.

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Step Two - Determine

respiratory involvementPaCO2:

Normal: 35 - 75 %%Hg (7.6 - 6 P&)

Respiratory acidosis: > 75 %%Hg (> 6P&)

Respiratory alkalosis: <35 %%Hg (< 7.6

P&)

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Step Tree - Determine

meta!olic involvementHCO"-

--------------------------

Normal: 22 - 26 %;/#eta!olic acidosis: <22 %;/

#eta!olic alkalosis: > 26 %;/

[*&#&# "!&o&*$: C&l!9l&*$# 8&l9$."%"l& *o *h$ &'$ $x!$''. I* "' #$"$# &' *h$

!&l!9l&*$# "!&o&*$ !o!$*&*"o o *h$

'&%pl$ !o$!*$# *o & PCO2 o 5.3P&

(70%%Hg).

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Step $o%r - Assess &or

compensationI p9$ $'p"&*o &!"#o'"' (h"gh P&CO2 o%&l

[HCO3-] &# lo pH) $ o9l# $xp$!* & $8$*9&l

!o%p$'&*o "!$&'$ " pl&'%& [HCO3-] *h&* o9l#

o *o $'*o$ *h$ pH *o o%&l. "%"l&l $ $xp$!*$'p"&*o &l&lo'"' *o $l"!"* & $8$*9&l !o%p$'&*o

#$!$&'$ " pl&'%& [HCO3-]. A p9$ %$*&ol"! &!"#o'"'

(lo [HCO3-] o%&l P&CO2 &# & lo pH) 'ho9l#

$l"!"* & !o%p$'&*o #$!$&'$ " P&CO2 &# & p9$%$*&ol"! &l&lo'"' (h"gh [HCO3-] o%&l P&CO2 &#

h"gh pH) 'ho9l# !&9'$ & !o%p$'&*o "!$&'$ "

P&CO2. All !o%p$'&*o $'po'$' o *o $'*o$

*h$ pH *o *h$ o%&l &g$ (4.35 - 4.75)

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$%rter analysis in cases o&

#'TA(O)*C AC*DOS*SAnion gap = &+ - [C- + HCO3-]

D"$$!$ $*$$ !&l!9l&*$# '$9% &"o' &#

!&*"o'.&'$# o *h$ p"!"pl$ o $l$!*"!&l $9*&l"* *h$ '$9%

!o!$*&*"o o !&*"o' (po'"*"8$ "o') 'ho9l# $;9&l *h$

'$9% !o!$*&*"o o &"o' ($g&*"8$ "o').

Ho$8$ '$9% &+ "o !o!$*&*"o "' h"gh$ *h&*h$ '9% o '$9% Cl- &# HCO3- !o!$*&*"o.

&+ = C- + HCO3- + 9%$&'9$# &"o' (g&p).

Normal anion gap: 12 %%ol/ (10 - 17 %%ol/)

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Normal anion gap acidosis

D"'$&'$ po!$''$' *h&* !& l$&# *o o%&l &"o g&p

(hp$!hlo$%"!) &!"#o'"'. '$9l %$%o"!

(DHA,):

&) D"&h$& (HCO3- &# &*$ "' lo'*).) +$*$&l #"8$'"o.

!) R$&l *99l& &!"#o'"'

#) Hp$&l"%$*&*"o

$) A!$*&?ol&%"#$) #"'!$ll&$o9' !o#"*"o': @h$ "!l9#$ p&!$&*"!

"'*9l& !hol$'*&%"$ &# !&l!"9% !hlo"#$ (C&Cl)

"g$'*"o &ll o h"!h !& "!$&'$ *h$ g&'*o"*$'*"&l

&'*&g$ o HCO3-.

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*ncreased anion gap

meta!olic acidosis#etanol poisoning

+remia: I $#-'*&g$ $&l &"l9$ " h"!h glo%$9l& "l*&*"o &*$ &ll'

$lo 1020 %l/%" &!"#' o% po*$" %$*&ol"'% &$ o* $x!$*$# &#

&!!9%9l&*$ " loo#.

Dia!etic ketoacidosis: "!o%pl$*$ ox"#&*"o o &** &!"#' !&9'$' & 9"l#9p o $*&-h#ox9*"! &# &!$*o&!*"! &!"#' ($*o&!"#').

Paraldeyde poisoning.

*scemia.

)actic acidosis: &!*"! &!"# "' *h$ $# po#9!* o gl9!o'$ $&#o "

p98"! &!"# *h$ $# po#9!* o &&$o"! gl!ol'"' "' o* ox"#"?$# *o

CO2 &# H2O 8"& *h$ @"!&oxl"! A!"# C!l$. (C&9'$': hpox"&

"'!h$%"& hpo*$'"o '$p'"').

'tylene glycol poisoning: *hl$$ "' %$*&ol"?$# &l!ohol

#$h#og$&'$ *o ox&l"! &!"# " *h$ l"8$. '9&ll *h$$ "' &l'o & !o$x"'*"g

l&!*"! &!"#o'"'.

Salicylate poisoning

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