using blood gases
DESCRIPTION
Using Blood Gases. Dr. Jonathan R. Goodall M62 Coloproctology Meeting 2 nd April 2004. Teaching Grandma to suck eggs…. Introduction. The necessary basics Clinical examples of ABG use in ICU Newer considerations in interpretation of acid-base disturbances. The Basics - Normal Values. - PowerPoint PPT PresentationTRANSCRIPT
Using Blood Gases
Dr. Jonathan R. GoodallM62 Coloproctology Meeting
2nd April 2004
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Teaching Grandma to suck eggs…
JRG Hope Hospital April 2004
Introduction
The necessary basics
Clinical examples of ABG use in ICU Newer considerations in
interpretation of acid-base disturbances
JRG Hope Hospital April 2004
The Basics - Normal Values
pH 7.35 - 7.45 H+ 35- 45 nmol.l-1
pCO2 4.5 - 6 kPa pO2 11 -14 kPa Actual HCO3 22-26 mmol.l-1
Standard HCO3 22-26 mmol.l-1
Base Excess +/- 2.0 SaO2 ≥ 95 %
JRG Hope Hospital April 2004
The Basics - Interpretation
Oxygenation
PaO2
? SaO2 + Hb more important
Interpret only with knowledge of FiO2
JRG Hope Hospital April 2004
The Basics - Interpretation
Acid-Base Status
pH pCO2
HCO3 (actual or standard)
Base Excess
Oxygenation
PaO2
SaO2 + Hb more important?
Interpret only with knowledge of FiO2
JRG Hope Hospital April 2004
H2O + CO2 H2CO3 H+ + HCO3-
JRG Hope Hospital April 2004
H2O + CO2 H2CO3 H+ + HCO3-
JRG Hope Hospital April 2004
The Basics - Standard Bicarbonate
The amount of bicarbonate that would be present if:
PCO2 was 5.3 kPa Temp 37°C Blood fully oxygenated At sea level
JRG Hope Hospital April 2004
The Basics - Base Excess (Deficit)
The amount of base that needs to be added to or subtracted from each litre of blood (ecf) to return the pH to a value of 7.4 at:
pCO2 5.3 kPa Temp 37°C
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Ivor Lewis Oesophagectomy
54 year old lady No significant PMH 7 hour procedure Initial post op period stable
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Date 17/3 18/3 18/3 19/3
Time 22:30 08:00 19:30 10:45
FiO2 0.4 0.6 1.0 1.0
pH 7.40 7.43 7.36 7.35
pCO2 4.7 4.44 4.71 4.74
pO2 14.8 9.59 16.4 9.9
BE -2.0 -1.5 -4.5 -5.9
JRG Hope Hospital April 2004
Date 17/3 18/3 18/3 19/3
Time 22:30 08:00 19:30 10:45
FiO2 0.4 0.6 1.0 1.0
pH 7.40 7.43 7.36 7.35
pCO2 4.7 4.44 4.71 4.74
pO2 14.8 9.59 16.4 9.9
BE -2.0 -1.5 -4.5 -5.9
JRG Hope Hospital April 2004
Date 17/3 18/3 18/3 19/3
Time 22:30 08:00 19:30 10:45
FiO2 0.4 0.6 1.0 1.0
pH 7.40 7.43 7.36 7.35
pCO2 4.7 4.44 4.71 4.74
pO2 14.8 9.59 16.4 9.9
BE -2.0 -1.5 -4.5 -5.9
JRG Hope Hospital April 2004
Date 17/3 18/3 18/3 19/3
Time 22:30 08:00 19:30 10:45
FiO2 0.4 0.6 1.0 1.0
pH 7.40 7.43 7.36 7.35
pCO2 4.7 4.44 4.71 4.74
pO2 14.8 9.59 16.4 9.9
BE -2.0 -1.5 -4.5 -5.9
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Date 21/3 22/3 23/3
Time 11:00 19:40 08:00
FiO2 0.5 0.45 0.4
pH 7.29 7.4 7.43
pCO2 6.51 4.95 4.76
pO2 11.3 16.8 10.8
BE -3.0 -1.5 -0.1
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Cellulitis (?)
75 year old lady Established atrial flutter Admitted with spreading cellulitis
right calf Hypotension unresponsive to fluids
(and dobutamine!)
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Initial ABGs
Date 31/3 31/3 31/3
Time 02:15 04:40 08:50
FiO2 1.0 0.5 0.45
pH 7.21 7.44 7.56
pCO2 9.15 4.91 3.34
pO2 10.8 16.0 16.8
BE -0.6 1.5 0.8
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Date 31/3 31/3 31/3
Time 02:15 04:40 08:50
FiO2 1.0 0.5 0.45
pH 7.21 7.44 7.56
pCO2 9.15 4.91 3.34
pO2 10.8 16.0 16.8
BE -0.6 1.5 0.8
JRG Hope Hospital April 2004
Date 31/3 31/3 31/3
Time 02:15 04:40 08:50
FiO2 1.0 0.5 0.45
pH 7.21 7.44 7.56
pCO2 9.15 4.91 3.34
pO2 10.8 16.0 16.8
BE -0.6 1.5 0.8
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
JRG Hope Hospital April 2004
Hyperchloraemic acidosis
Base deficit traditionally used as marker for metabolic acidosis
Appropriate fluid resuscitation should decrease base deficit
Chloride rich solutions (0.9% NaCl) can potentiate metabolic acidosis www.anaesthetist.com/icu/elec/ionz/Stewart
If base deficit persists despite ‘adequate’ fluids in an otherwise well patient, check [Cl-]!
JRG Hope Hospital April 2004
Summary
Arterial blood gases can be used to guide therapy
Must be interpreted in the light of the clinical setting
Look at acid–base disturbances, then oygenation with FiO2
Remember the possibility that treatment may cause problems!
JRG Hope Hospital April 2004