Easy ABG analysis

ABG normal values

pH= 7.35 - 7.45
PaO2 = 80-100mmHg
PaCO2 = 35 - 45mmHg
HCO3 = 22 - 26 mEq/L
SaO2 = 93-100%

Respiratory Acidosis
Respiratory Alkalosis

CO2 acts as acid in human body

Resp Acidosis = incr in PaCO2 in presence of acidosis (pH> 7.45)

Resp Alk= decr in PaCO2 in presence of alkalosis (ph<7.35)

Metabolic Acidosis
Metabolic Alkalosis

HCO3 = base solution

Metabolic acidosis = decr in HCO3 in acidotic state

Metabolic alkalosis=>HCO3 in alkalotic state

Compensation

In order to recognize compensation, look for changes in buffering system that is not part of the primary problem

Ex: DM pt in ketoacidosis
pH=7.29; HCO3=16 -- metabolic acidosis
ABGs show PaCO2=27; pt has incr RR to blow off CO2.
**This creates a resp alkalosis wh is opposite of meta acidosis

Compensation

Buffer system changes in same direction as primary problem

Ex: pH=7.25; PaCO2=58 = resp acid. HCO3= 30

the other buffering system is same direction as primary prob. PaCO2 is elevated and compensatory HCO3 is up!

Both are elevated, but we know resp acidosis because the pH =7.27!!!

ABG analysis

1) Is pH acidotic/alkalotic
2) What is the primary problem?
--if acidotic w/high PaCO2 then Respiratory
-- if acidotic w/low HCO3 then Metabolic
--if alkalotic w/low PaCO2 then Respiratory
-- if alkalotic w/high HCO3 then Metabolic

Case Studies

1) pH=7.17; PaCO2=68; HCO3=22 decreased LOC, postop, MSO4 for pain

2) pH=7.37; PaCO2=29; hCO3=17 diarrhea x4d, incr RR

3) pH=7.52, PaCO2=35; HCO3=29 POD 5, NGT w/output>900cc, decrease in MS

3)

Case Study answers

1) Uncompensation Resp acid

2) Compensated Meta acid

3) Uncompensated Meta alka

Clinical Manifestations:
Respiratory acidosis

*PaCO2; HCO3 nml or > c/renal compensation

*vasodilation; dysrhthmia; tachycardia; somnolence; < ventilation

Clinical Manifestations:
Respiratory Alkalosis

* pH; PaCO2; HCO3 nml or < secondary to compensation

*N/V; tingling fingers

Clinical Manifestations:
Metabolic acidosis

*hyperkalemia; shift of acid to ICF & K to ECF

* anorexia; N/V

* warm, flushed skin

*dysrhytmia; CNS dysfunction

*HA; diarrhea; tremors