Transcript ABG Presentation

Arterial Blood Gas Analysis
What is an ABG?
• The Components
• pH / PaCO2 / PaO2 / HCO3 / O2sat / BE
• Desired Ranges
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pH - 7.35 - 7.45
PaCO2 - 35-45 mmHg
PaO2 - 80-100 mmHg
HCO3 - 21-27
O2sat - 95-100%
Base Excess - +/-2 mEq/L
Why Order an ABG?
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Aids in establishing a diagnosis
Helps guide treatment plan
Aids in ventilator management
Improvement in acid/base management allows for
optimal function of medications
• Acid/base status may alter electrolyte levels critical
to patient status/care
Logistics
• When to order an arterial line -• Need for continuous BP monitoring
• Need for multiple ABGs
• Where to place -- the options
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Radial
Femoral
Brachial
Dorsalis Pedis
Axillary
Acid Base Balance
• The body produces acids daily
•15,000 mmol CO2
•50-100 mEq Nonvolatile acids
• The lungs and kidneys attempt to maintain
balance
Acid Base Balance
•Assessment of status via bicarbonatecarbon dioxide buffer system
•CO2 + H2O <--> H2CO3 <--> HCO3- + H+
•ph = 6.10 + log ([HCO3] / [0.03 x PCO2])
The Terms
• ACIDS
• Acidemia
• Acidosis
•Respiratory
↑CO2
•Metabolic
↓HCO3
• BASES
• Alkalemia
• Alkalosis
• Respiratory
↓CO2
• Metabolic
↑HCO3
Respiratory Acidosis
• ↓ph, ↑CO2, ↓Ventilation
• Causes
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CNS depression
Pleural disease
COPD/ARDS
Musculoskeletal disorders
Compensation for metabolic alkalosis
Respiratory Acidosis
• Acute vs Chronic
• Acute - little kidney involvement. Buffering via
titration via Hb for example
• pH ↓by 0.08 for 10mmHg ↑ in CO2
• Chronic - Renal compensation via synthesis
and retention of HCO3 (↓Cl to balance charges
Ü hypochloremia)
• pH ↓by 0.03 for 10mmHg ↑in CO2
Respiratory Alkalosis
• ↑pH, ↓CO2, ↑Ventilation
• ↓ CO2 Ü ↓ HCO3 (↑Cl to balance charges Ü
hyperchloremia)
• Causes
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Intracerebral hemorrhage
Salicylate and Progesterone drug usage
Anxiety Ü ↓lung compliance
Cirrhosis of the liver
Sepsis
Respiratory Alkalosis
• Acute vs. Chronic
• Acute - ↓HCO3 by 2 mEq/L for every 10mmHg ↓
in PCO2
• Chronic - Ratio increases to 4 mEq/L of HCO3
for every 10mmHg ↓ in PCO2
• Decreased bicarb reabsorption and decreased
ammonium excretion to normalize pH
Metabolic Acidosis
• ↓pH, ↓HCO3
• 12-24 hours for complete activation of
respiratory compensation
• ↓PCO2 by 1.2mmHg for every 1 mEq/L
↓HCO3
• The degree of compensation is assessed
via the Winter’s Formula
Ü PCO2 = 1.5(HCO3) +8 ± 2
The Causes
• Metabolic Gap
Acidosis
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M - Methanol
U - Uremia
D - DKA
P - Paraldehyde
I - INH
L - Lactic Acidosis
E - Ehylene Glycol
S - Salicylate
• Non Gap Metabolic
Acidosis
• Hyperalimentation
• Acetazolamide
• RTA (Calculate urine
anion gap)
• Diarrhea
• Pancreatic Fistula
Metabolic Alkalosis
• ↑pH, ↑HCO3
• ↑PCO2 by 0.7 for every 1mEq/L ↑ in HCO3
• Causes
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Vomiting
Diuretics
Chronic diarrhea
Hypokalemia
Renal Failure
Mixed Acid-Base Disorders
• Patients may have two or more acidbase disorders at one time
• Delta Gap
Delta HCO3 = HCO3 + Change in anion gap
>24 = metabolic alkalosis
The Steps
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Start with the pH
Note the PCO2
Calculate anion gap
Determine compensation
Sample Problem #1
• An ill-appearing alcoholic male presents
with nausea and vomiting.
• ABG - 7.4 / 41 / 85 / 22
• Na- 137 / K- 3.8 / Cl- 90 / HCO3- 22
Sample Problem #1
•Anion Gap = 137 - (90 + 22) = 25
Ü anion gap metabolic acidosis
•Winters Formula = 1.5(22) + 8 ± 2
= 39 ± 2
Ü compensated
•Delta Gap = 25 - 10 = 15
15 + 22 = 37
Ü metabolic alkalosis
Sample Problem #2
• 22 year old female presents for
attempted overdose. She has taken an
unknown amount of Midol containing
aspirin, cinnamedrine, and caffeine. On
exam she is experiencing respiratory
distress.
Sample Problem #2
• ABG - 7.47 / 19 / 123 / 14
• Na- 145 / K- 3.6 / Cl- 109 / HCO3- 17
• ASA level - 38.2 mg/dL
Sample Problem #2
•Anion Gap = 145 - (109 + 17) = 19
Ü anion gap metabolic acidosis
•Winters Formula = 1.5 (17) + 8 ± 2
= 34 ± 2
Ü uncompensated
•Delta Gap = 19 - 10 = 9
9 + 17 = 26
Ü no metabolic alkalosis
Sample Problem #3
• 47 year old male experienced crush
injury at construction site.
• ABG - 7.3 / 32 / 96 / 15
• Na- 135 / K-5 / Cl- 98 / HCO3- 15 / BUN38 / Cr- 1.7
• CK- 42, 346
Sample Problem #3
•Anion Gap = 135 - (98 + 15) = 22
Ü anion gap metabolic acidosis
•Winters Formula = 1.5 (15) + 8 ± 2
= 30 ± 2
Ü compensated
•Delta Gap = 22 - 10 = 12
12 + 15 = 27
Ü mild metabolic alkalosis
Sample Problem #4
• 1 month old male presents with
projectile emesis x 2 days.
• ABG - 7.49 / 40 / 98 / 30
• Na- 140 / K- 2.9 / Cl- 92 / HCO3- 32
Sample Problem #4
•Metabolic Alkalosis, hypochloremic
•Winters Formula = 1.5 (30) + 8 ± 2
= 53 ± 2
Ü uncompensated