ABG  Made  Easy

Dr.  Vishal  GuptaICU  Fellow

Nepean  Hospital

∗ To  establish  the  severity  of  an  oxygenation  abnormality

∗ To  evaluate  hyper-­ or  hypoventilation

∗ To  determine  acid-­base  status,  particularly  in  patients  with  metabolic  acidosis

∗ To  track  the  application  of  mechanical  ventilation  in  a  critically  ill  patient

Benefits  of  ABG

1. History

2. What is the Oxygenation status

3. What is the pH? Acidemia or Alkalemia?

4. What is the primary disorder present?

5. Is there appropriate compensation?

6. Is the compensation acute or chronic?

7. Is there an anion gap?

8. If there is a AG check the delta gap?

9. What is the differential for the clinical processes?

Practical  Approach  to  ABG

1. P/F  ratio2. A-­‐a  gradient

Oxygenation  Status

Normal  Lungs Sick  Lungs

Hypoventilation

Subnormal  PiO2

V/Q  mismatch

Shunt

Other

Respiratory  Disorders

Metabolic  Disorder

Metabolic  Disorder

Metabolic  Disorder

Interesting  ABGs

1).  A  29-­‐year-­‐old  female  is  admitted  to  ICU  extubated following  an  emergency  

appendicectomy and  failure  to  progress.  Comment  on  the  ABG  data  that  was  taken  

on  admission  to  ICU:

FiO2 0.4 pH 7.33 pCO2 42 mm Hg pO2 110 mm Hg Bicarbonate 22.0 Base Excess - 3.9

2).  A  29-­‐year-­‐old  female  is  admitted  to  ICU  extubated following  an  emergency  Caesarian

section  at  38  weeks  gestation  for  pre-­‐eclampsia and  failure  to  progress.  Comment  on  

the  ABG  data  that  was  taken  on  admission  to  ICU:

FiO2 0.4 pH 7.33 pCO2 42 mm Hg pO2 110 mm Hg Bicarbonate 22.0 Base Excess - 3.9

3).  A  72  year  old  lady  with  a  

background  of  CCF,  who  

underwent  a  laparotomy  and  

adhesiolysis in  the  context  of  a  

subacute  small  bowel  obstruction.  

Following  the  laparotomy,  patient  

was  extubated and  brought  to  

recovery.  ABG  was  done,  as  

patient`s  breathing    was  found  to  

be  shallow  &  rapid

4).  After  being  discovered  at  his  rural  

property   in  an  unconscious  state,  this  

elderly  gentleman  was  intubated  and  

brought  to  the  ICU.  Airway  ulceration  

was  noted  by  the  rescuers.  Apparently  

he  intentionally  drank  an  unknown  

amount  of  some  unknown  smelly  liquid.

S.  Osmolality  :  362,  Urea  12,  Albumin  40

5).  A  65-­‐year-­‐old  male  presented  

to  ED  with  fever  &  productive  

cough.  On  examination,  

tachycardiac,  hypotensive  &  

dehydrated.  Patient  was  

resuscitated  with  4  lts of  IV  fluid  

but  he  remained  hypotensive  &  

required  vasopressors.

6).  A  24-­‐year-­‐old  female  with  a  

history  of  depression  presents  

with  seizures  and  decreased  

consciousness. The  following  

ABG  was  taken  on  FiO2  0.3.  

7).  A  46-­‐year-­‐old  male  

presents  with  vomiting  for  

the  past  five  days.  His  

arterial  blood  gas  result  on  

room  air  is  shown  below:

8).  The  following  results  were  

obtained  from  a  23-­‐year-­‐old  

female  admitted  with  severe  

asthma.

9).  The  following  data  are  from  

the  arterial  blood  gas  analysis  of  

a  71-­‐year-­‐old  male  with  

necrotising fasciitis:

10).  A  35-­‐year-­‐old  male  has  

presented  to  the  Emergency  

Department  with  weakness  

and  constipation.  Whilst  in  the  

Emergency  Department  he  

had  the  following  results:

11).  A  79  year  old  lady  

with  history  of  AF  

admitted  with  nausea,  

vomiting  &  abdominal  

pain  and  found  to  be  in  

severe  shock.  

12).  No  History  available

∗ Acid  Base  physiology  :  Kerry  Brandis∗ CICM∗ Alex  Psirides (Wellington   ICU)  :  Diagrams∗ Deranged  physiology

References

Thanks