interpretation of arterial blood gases:traditional versus modern
TRANSCRIPT
![Page 1: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/1.jpg)
![Page 2: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/2.jpg)
Interpretation of Arterial Blood Gases
Traditional Vs Modern
By
Gamal Rabie Agmy , MD , FCCP Professor of Chest Diseases ,Assiut University
![Page 3: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/3.jpg)
Handerson Hasselbach
Equation
• PH= pKa+ Log HCO3/PaCo2
• PH= Log HCO3/PaCo2
• PH= HCO3
• PH= HCO3
• PH= PaCo2
• PH= PaCo2
![Page 4: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/4.jpg)
Co2+H2o=H2co3=Hco3- + H+
Hprotein=H+ + Protein-
![Page 5: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/5.jpg)
![Page 6: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/6.jpg)
• PH 7.35-7.45
• HCO3 22-26 mEq/L
• PaCo2 35-45 mmHg
• PaO2 97 mmHg
• BE/BD +2 to -2
• Haemoglobin 15 gram
• A-a O2 gradient N < 15
A-a O2 gradient OLDER PERSONS
– 2.5 +0.25*AGE
– eg. AGE 60, 2.5+15=17.5
– eg. AGE 80, 2.5+20=22.5
Normal Values
![Page 7: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/7.jpg)
![Page 8: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/8.jpg)
Definition of Respiratory Failure
Respiratory failure is a syndrome of
inadequate gas exchange due to
dysfunction of one or more essential
components of the respiratory system
![Page 9: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/9.jpg)
Types of Respiratory Failure
Type 1 (Hypoxemic ): * PO2 < 60 mmHg on room air.
Type 2 (Hypercapnic / Ventilatory): *PCO2 > 50
mmHg
Type 3 (Peri-operative): *This is generally a subset of
type 1 failure but is sometimes considered
separately because it is so common.
Type 4 (Shock): * secondary to cardiovascular
instability.
![Page 10: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/10.jpg)
FIO2
Ventilation without
perfusion (deadspace ventilation)
Diffusion abnormality
Perfusion without
ventilation (shunting)
Hypoventilation
Normal
![Page 11: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/11.jpg)
Brainstem
Spinal cord
Nerve root Airway
Nerve
Neuromuscular junction
Respiratory muscle
Lung
Pleura
Chest wall
Sites at which disease may cause ventilatory disturbance
![Page 12: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/12.jpg)
• Type 1:
A-Acute
B-Chronic
C-Acute on top of chronic
• Type 2: A-Acute
B-Chronic
C-Acute on top of chronic
Types of RF:
![Page 13: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/13.jpg)
• Type 1:
PaO2<60 mm Hg
PaCo235-45 mmHg
• Type 2: PaO2<60 mm Hg
PaCo2>50 mmHg
Types of RF:
![Page 14: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/14.jpg)
Type 1: • Acute:
Pao2<60mmHg HCO3 Normal
PaCo235-45mmHg PH > 7.45
• Chronic:
Pao2<60mmHg PaCo235-45mmHg
HCO3 <22mEq/L PH=7.40-7.45
• Acute on top of chronic:
Pao2<60mmHg HCO3 <22mEq/L
PaCo235-45mmHg PH > 7.45
Types of RF:
![Page 15: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/15.jpg)
Type 2: • Acute:
Pao2<60mmHg HCO3 Normal
PaCo2>50 mmHg PH<7.35
• Chronic:
Pao2<60mmHg PaCo2 >50 mmHg
HCO3 >26 mEq/L PH=7.35-7.40
• Acute on top of chronic:
Pao2<60mmHg HCO3 >26 mEq/L
PaCo2 >50 mmHg PH<7.35
Types of RF:
![Page 16: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/16.jpg)
![Page 17: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/17.jpg)
Uncompensated
Partially compensated
Compensated
Uncompensated
Partially compensated
Compensated
M acidosisM acidosis
![Page 18: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/18.jpg)
Uncompensated
*PH < 7.35
*PaCo2 normal
*HCO3 < 22 ml eq/L
![Page 19: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/19.jpg)
Partially compensated
*PH< 7.35
*PaCo2 < 36 mmHg
*HCO3 < 22 ml eq/L
![Page 20: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/20.jpg)
Compensated
PH 7.35-7.40
PaCo2 < 35 mmHg
HCO3 < 22 mleq/L
![Page 21: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/21.jpg)
Uncompensated
Partially compensated
Compensated
Uncompensated
Partially compensated
Compensated
M alkalosisM alkalosis
![Page 22: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/22.jpg)
Uncompensated
PH > 7.45
PaCo2 normal
HCO3 >26 ml Eq/L
![Page 23: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/23.jpg)
Partially compensated
PH >7.45
PaCo2 > 45 mmHg
HCO3 > 26 ml Eq/L
![Page 24: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/24.jpg)
Compensated
PH 7.40-7.45
PaCo2 > 45 mmHg
HCO3 > 26 mlEq/L
![Page 25: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/25.jpg)
![Page 26: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/26.jpg)
Combined acidosis:
PH<7.35 PaCO2>50 HCO3<22
Combined alkalosis:
PH >7.45 PaCo2<35 HCO3>26
![Page 27: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/27.jpg)
Blood Gas Analysis &
Acid-Base Disorders
Professor Gamal Rabie Agmy, MD, FCCP
Professor of Chest Diseases , Assiut
University
![Page 28: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/28.jpg)
Blood Gas Analysis
Arterial blood
Sea level (101.3kPa, 760mmHg)
Quiet
Anti-coagulate blood
Inspire air (Whether O2 supply)
![Page 29: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/29.jpg)
Why Order an ABG?
• 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
![Page 30: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/30.jpg)
Clinical Significance
To evaluate oxygen status
To evaluate ventilation
To evaluate acid-base disorder
![Page 31: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/31.jpg)
How to evaluate oxygen status?
PaO2:
Partial pressure of oxygen in Arterial
blood .
Normal: 95-98 mmHg (12.6-13 kPa)
Estimate formula of age:
PaO2=100mmHg-(age×0.33) ±5mmHg
![Page 32: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/32.jpg)
Hypoxaemia
Mild: 80-60mmHg
Medorate: 60-40mmHg
Severe: <40mmHg
![Page 33: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/33.jpg)
Respiratory Failure
PaO2<60mmHg respiratory failure
Notice: sea level, quiet, inspire air
rule off other causes (Congenital
cyanotic heart disease and abnormal
types of Hg)
![Page 34: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/34.jpg)
Classification of Respiratory Failure
PaCO2: The carbon dioxide partial
pressure
of arterial blood
Normal: 35-45mmHg (4.7-6.0kPa)
mean: 40mmHg
![Page 35: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/35.jpg)
Classification of Respiratory Failure
Type Ⅰ TypeⅡ
PaO2 (mmHg) <60 <60
PaCO2 (mmHg) ≤35-45 >50
![Page 36: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/36.jpg)
Other Parameters
SaO2: Saturation of arterial blood
oxygen
Normal: 0.95-0.98
Significance: a parameter to evaluate
hypoxaemia, but not sensitive
ODC ( Dissociation curve of
oxygenated hemoglobin): “S” shape
![Page 37: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/37.jpg)
SaO2%
PO2
Oxygen dissociation curve
![Page 38: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/38.jpg)
PH 2,3DPG temperature CO2
ODC to right deviation
Oxygenated hemoglobin release oxygen
to tissue, prevent hypoxia of the tissue.
But absorbed oxygen of hemoglobin is
decreased from the alveoli.
Bohr effect: movement of ODC place is
induced by PH.
![Page 39: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/39.jpg)
PA-aO2: Difference of alveoli-arterial
blood oxygenic partial pressure.
Normal: 15-20mmHg (<30mmHg in the
old)
Significance: a sensitive parameter in
gas exchange
![Page 40: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/40.jpg)
PvO2: Partial pressure of oxygen in
mixed venous blood.
Normal: 35-45mmHg
mean: 40mmHg
Significance: Pa-vO2 is to reflect the
tissue absorbing oxygen.
![Page 41: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/41.jpg)
CaO2: The content of the oxygen of the
arterial blood.
Normal: 19-21mmol/L
Significance: a comprehensive
parameter to evaluate arterial
oxygen.
![Page 42: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/42.jpg)
Parameters in acid-basic disorder evaluation
PH: negative logarithm of
Hydrogen ion concentration.
Normal: 7.35-7.45
mean: 7.4
PH=Pka+log 〔HCO3
- 〕
0.03PaCO2
=6.1+log 20
1
![Page 43: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/43.jpg)
HCO3- (bicarbonate):
SB (standard bicarbonate)
AB (actual bicarbonate)
SB: the contents of HCO3- of serum of arterial
blood in 37℃, PaCO2 40mmHg, SaO2 100%.
Normal: 22-26 mmol/L
mean: 24mmol/L
AB: The contents of HCO3- in actual condition.
In normal person: AB=SB
![Page 44: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/44.jpg)
AB and SB are parameters to reflect
metabolism, regulated by kidney.
Difference of AB-SB can reflect the
respiratory affection on serum HCO3- .
Respiratory acidosis: AB>SB
Respiratory alkalosis: AB<SB
Metabolic acidosis: AB=SB<Normal
Metabolic alkalosis: AB=SB>Normal
![Page 45: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/45.jpg)
Buffer bases(BB):
is the total of buffer negative ion of blood.
BB: HCO3-
hemoglobin
plasma proteins
HPO42- (phosphate)
Normal: 45-55mmol/L
mean: 50mmol/L
Significance: Metabolic acidosis: BB
Metabolic alkalosis: BB
![Page 46: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/46.jpg)
Bases excess (BE):
the acid or bases used to regulate blood PH 7.4 . ( in 38℃,PaCO2 40mmHg, SaO2 100%)
Normal: 0±2.3 mmol/L
Significance:
add acid: BE(+), BB
add base: BE(-), BB
![Page 47: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/47.jpg)
Total plasma CO2 (T-CO2):
total content of the CO2 .
Normal: HCO3- >95%
![Page 48: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/48.jpg)
Logistics
• When to order an arterial line -- – Need for continuous BP monitoring
– Need for multiple ABGs
– COP measurement by thermodilution method
• Where to place -- the options – Radial
– Femoral
– Brachial
– Dorsalis Pedis
– Axillary
![Page 49: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/49.jpg)
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
![Page 50: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/50.jpg)
Acid Base Balance
• Assessment of status via bicarbonate-carbon dioxide buffer system
– CO2 + H2O <--> H2CO3 <--> HCO3- + H+
– ph = 6.10 + log ([HCO3] / [0.03 x PCO2])
![Page 51: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/51.jpg)
The Terms
• ACIDS
– Acidemia
– Acidosis
• Respiratory
CO2
• Metabolic
HCO3
• BASES
– Alkalemia
– Alkalosis
• Respiratory
CO2
• Metabolic
HCO3
![Page 52: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/52.jpg)
Respiratory Acidosis
• ph, CO2, Ventilation
• Causes
– CNS depression
– Pleural disease
– COPD/ARDS
– Musculoskeletal disorders
– Compensation for metabolic alkalosis
![Page 53: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/53.jpg)
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 hypochloremia) • pH by 0.03 for 10mmHg in CO2
![Page 54: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/54.jpg)
Respiratory Alkalosis
• pH, CO2, Ventilation
• CO2 HCO3 (Cl to balance charges hyperchloremia)
• Causes – Intracerebral hemorrhage
– Salicylate and Progesterone drug usage
– Anxiety lung compliance
– Cirrhosis of the liver
– Sepsis
![Page 55: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/55.jpg)
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
![Page 56: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/56.jpg)
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
PCO2 = 1.5(HCO3) +8 2
![Page 57: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/57.jpg)
The Causes
• Metabolic Gap Acidosis – 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
![Page 58: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/58.jpg)
Metabolic Alkalosis
• pH, HCO3
• PCO2 by 0.7 for every 1mEq/L in HCO3
• Causes
– Vomiting
– Diuretics
– Chronic diarrhea
– Hypokalemia
– Renal Failure
![Page 59: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/59.jpg)
Mixed Acid-Base Disorders
• Patients may have two or more acid-
base disorders at one time
• Delta Gap
Delta HCO3 = HCO3 + Change in anion gap
Delta HCO3 >24 = metabolic alkalosis
![Page 60: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/60.jpg)
The Steps
• Start with the pH
• Note the PCO2
• Calculate anion gap
• Determine compensation
![Page 61: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/61.jpg)
Sample Problem #1
• An ill-appearing alcoholic male presents
with nausea and vomiting.
– ABG – 7.25 / 34 / 85 / 16
– Na- 137 / K- 3.8 / Cl- 90 / HCO3- 16
![Page 62: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/62.jpg)
Sample Problem #1
• Anion Gap = 137 - (90 +16) =31
anion gap metabolic acidosis
• Winters Formula = 1.5(16) + 8 2
= 32 2
compensated
• Delta Gap =( 31 – 12) + 16 = 35
metabolic alkalosis
![Page 63: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/63.jpg)
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.
![Page 64: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/64.jpg)
Sample Problem #2
• ABG - 7.47 / 19 / 123 / 14
• Na- 145 / K- 3.6 / Cl- 109 / HCO3- 14
• ASA level - 38.2 mg/dL
![Page 65: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/65.jpg)
Sample Problem #2
• Anion Gap = 145 - (109 + 14) = 22
anion gap metabolic acidosis
• Winters Formula = 1.5 (14) + 8 2
= 29 2
uncompensated
• Delta Gap = 22 - 12 = 10
10 + 14 = 24
no metabolic alkalosis
![Page 66: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/66.jpg)
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 /
BUN- 38 / Cr- 1.7
• CK- 42, 346
![Page 67: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/67.jpg)
Sample Problem #3
• Anion Gap = 135 - (98 + 15) = 22
anion gap metabolic acidosis
• Winters Formula = 1.5 (15) + 8 2
= 30 2
compensated
• Delta Gap = 22 - 10 = 12
12 + 15 = 27
mild metabolic alkalosis
![Page 68: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/68.jpg)
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
![Page 69: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/69.jpg)
Sample Problem #4
• Metabolic Alkalosis, hypochloremic
• Winters Formula = 1.5 (30) + 8 2
= 53 2
uncompensated
![Page 70: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/70.jpg)
SVCC Respiratory Care
Programs
ABG Analysis, Introduction
• pH, PaCO2, PaO2 are measured directly
by special electrodes contained in a
device made for that purpose
• Other indirect measurements can be
made or calculated from the above
measurements i.e., HCO3-, O2 Sat.
![Page 71: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/71.jpg)
SVCC Respiratory Care
Programs
QA in Blood Gas Analysis
• ABG lab must be able to assure
accurate and reliable results
• The above is accomplished by applying
protocols in 3 areas:
- pre-analytic error
- calibration
- quality control
![Page 72: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/72.jpg)
SVCC Respiratory Care
Programs
Pre-analytic Error • All factors that cause variance in lab results
prior to the sample arriving in the ABG lab.
• 4 factors assoc. with signif. P. E. are:
- air bubbles in sample
- time delay (iced sample with more than
60 min. or uniced with more
than 10 min.)
- blood clots in sample
- small sample size where excessive
anticaogulation is suspect
![Page 73: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/73.jpg)
SVCC Respiratory Care
Programs
Calibration
• Purpose is assure consistency
• Def.: the systemic standardization of the
graduation of a quantitative measuring
instrument
• Calibrating standards for blood gas analyzers
should simulate the physical properties of
blood and meet manuf. specs.
• When 2 standards are used ---> 2-point
calibration, performed after 50 blood gases or
at least every 8 hours
![Page 74: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/74.jpg)
SVCC Respiratory Care
Programs
Calibration (cont’d)
• A “one-point calibration” is an
adjustment of the electronic response of
an electrode to a single standard and is
performed more freq. than a 2 pt. cal.,
ideally prior to each sample analysis
![Page 75: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/75.jpg)
SVCC Respiratory Care
Programs
Quality Control
• Refers to a system that documents the
accuracy and reliability of the blood gas
measurements and is essential to assure
accuracy in the blood gas lab
• Media available as blood gas controls
include:
- aqueous buffers
- glycerin soltn.
- human/animal serum and blood
- artificial blood
• A QC system must ID problems and specify
corrective action, document. of accept. oper.
![Page 76: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/76.jpg)
SVCC Respiratory Care
Programs
QC (cont’d)
• Documentation of QC is usu. on Levy-
Jennings Chart which shows measured
results on the y axis versus time of
measurement on the x axis
• SD is used to summarize a mass of data: the
difference between a number in a data set
and the mean of the data set is called a
deviation. A deviation shows how much a
number varies from the mean
![Page 77: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/77.jpg)
SVCC Respiratory Care
Programs
QC (cont’d)
• A properly functioning electrode that
repeatedly analyzes a known value will
produce results within a rel. small range, e.g.,
a PaCO2 electrode that analyzes a 40 mmHg
standard 100 times will produce results where
2/3 of the measurements are 39 - 41 mmHg
and nearly all measurements fall in 38 - 42
range
• 95% of the control measurements should fall
within 2 SD
![Page 78: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/78.jpg)
SVCC Respiratory Care
Programs
QC (cont’d)
• Random errors indicates a value outside of 2
SD of the mean: a single random error has
minor signif., but if number increased the
machine and techniques must be evaluated
• Systematic errors is recurrent measurable
deviation from the mean
• Causes of systematic errors:
- contaminated standard
- variations in electrode temp.
- inconsistent introduction of standard
![Page 79: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/79.jpg)
SVCC Respiratory Care
Programs
QC (cont’d)
• Causes of systematic error (cont’d)
- inconsistent calibration
technique - change in QC
standard storage or prep. - electrode
problems, e.g., protein contamin.,
membrane malfunction,
contamin. electrolyte, or electrical
problems
![Page 80: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/80.jpg)
SVCC Respiratory Care
Programs
QC Levels
• Level 1 simulates a patient
hypoventilating
• Level 2 simulates a patient with normal
ventilatory status
• Level 3 simulates a patient
hyperventilating
![Page 81: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/81.jpg)
HCO3- (bicarbonate):
SB (standard bicarbonate)
AB (actual bicarbonate)
SB: the contents of HCO3- of serum of arterial
blood in 37-38℃, PaCO2 40mmHg, SaO2 100%.
Normal: 22-27mmol/L
mean: 24mmol/L
AB: The contents of HCO3- in actual condition.
In normal person: AB=SB
![Page 82: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/82.jpg)
AB and SB are parameters to reflect
metabolism, regulated by kidney.
Difference of AB-SB can reflect the
respiratory affection on serum HCO3- .
Respiratory acidosis: AB>SB
Respiratory alkalosis: AB<SB
Metabolic acidosis: AB=SB<Normal
Metabolic alkalosis: AB=SB>Normal
![Page 83: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/83.jpg)
8 Sequential Rules:
• Rule #1
– Must know the pH; pH determines whether the
primary disorder is an acidosis or an alkalosis
• Rule #2
– Must know the PaCO2 and serum HCO3-
• Rule #3
– Must be able to establish that the available data
(pH, PaCO2, and HCO3-) are consistent
![Page 84: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/84.jpg)
Are the data consistent?
• The Henderson Equation:
3
2
24HCO
PaCOH
![Page 85: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/85.jpg)
Convert [H+] to pH:
• Subtract calculated [H+] from 80; this gives
the last two digits of a pH beginning with 7
– example: calculated [H+] of 24 converts to pH
of (80-24)~7.56
– example: calculated [H+] of 53 converts to pH
of (80-53)~7.27
• Refer to table 1 in handout for more precise
conversion, or if calculated [H+] exceeds 80
![Page 86: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/86.jpg)
Relationship between [H+] & pH
![Page 87: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/87.jpg)
Relationship between [H+] & pH
pH [H+] pH [H
+]
7.80
7.75
16
18
7.30
7.25
50
56
7.70
7.65
20
22
7.20
7.15
63
71
7.60
7.55
25
28
7.10
7.00
79
89
7.50
7.45
32
35
6.95
6.90
100
112
7.40
7.35
40
45
6.85
6.80
141
159
![Page 88: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/88.jpg)
![Page 89: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/89.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 90: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/90.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 91: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/91.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 92: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/92.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 93: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/93.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 94: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/94.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 95: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/95.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 96: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/96.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 97: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/97.jpg)
Simple Acid-Base Disorders:
T ype of D isorder pH PaC O 2 [H C O 3]
M etabolic A cidosis
M etabolic A lkalosis
A cute R espiratory A cidosis
C hronic R espiratory A cidosis
A cute R espiratory A lkalosis
C hronic R espiratory A lkalosis
![Page 98: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/98.jpg)
Simple Acid-Base Disorders:
• The compensatory variable always changes
in the SAME DIRECTION as the
primarily deranged variable
• Compensation is always more pronounced
in CHRONIC RESPIRATORY disorders
than in acute respiratory disorders
![Page 99: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/99.jpg)
8 Sequential Rules:
• Rule #4:
– must know if compensation is appropriate
– compensation never overshoots
• Must have known “rules of thumb” to
interpret appropriateness of compensation
![Page 100: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/100.jpg)
Rules of Compensation:
• Metabolic Acidosis
– PaCO2 should fall by 1 to 1.5 mm Hg x the fall
in plasma [HCO3]
• Metabolic Alkalosis
– PaCO2 should rise by .25 to 1 mm Hg x the rise
in plasma [HCO3]
![Page 101: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/101.jpg)
Rules of Compensation:
• Acute Respiratory Acidosis
– Plasma [HCO3] should rise by ~1mmole/l for
each 10 mm Hg increment in PaCO2
• Chronic Respiratory Acidosis
– Plasma [HCO3] should rise by ~4mmoles/l for
each 10 mm Hg increment in PaCO2
![Page 102: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/102.jpg)
Rules of Compensation:
• Acute Respiratory Alkalosis
– Plasma [HCO3] should fall by ~1-3 mmole/l for
each 10 mm Hg decrement in PaCO2, usually
not to less than 18 mmoles/l
• Chronic Respiratory Alkalosis
– Plasma [HCO3] should fall by ~2-5 mmole/l for
each 10 mm Hg decrement in PaCO2, usually
not to less than 14 mmoles/l
![Page 103: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/103.jpg)
Case #1:
• A 24 years old with chronic renal failure
presents to ER with history of increasing
azotemia, weakness, and lethargy. Exam
reveals the patient to be modestly
hypertensive, and tachypneic. Labs reveal
BUN=100 mg, and Creatinine=8 mg.
![Page 104: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/104.jpg)
Case #1:
• Steps 1&2: must know pH, PaCO2, HCO3
• pH=7.37, PaCO2=22, and HCO3=12
• Step 3: are the available data consistent?
3
2
24HCO
PaCOH
![Page 105: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/105.jpg)
Case #1:
• [H+]=44, equates to pH~7.36; data are thus
consistent
• What is the primary disorder?
• “_________Acidosis”
• Which variable (PaCO2, HCO3) is deranged
in a direction consistent with acidosis?
• Primary disorder is “Metabolic Acidosis”
![Page 106: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/106.jpg)
Is compensation appropriate?
• HCO3 is decreased by 12 mmoles/l
• PaCO2 should decrease by 1 to 1.5 times the
fall in HCO3; expect PaCO2 to decrease by
12-18 mm Hg or be between 22-28 mm Hg
• Since PaCO2 is 22 mm Hg, compensation is
appropriate, and the data are consistent with
a simple metabolic acidosis with respiratory
compensation
![Page 107: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/107.jpg)
8 Sequential Rules:
• Rule #5:
– If the data are consistent with a simple disorder,
it does not guarantee that a simple disorder
exists; need to examine the patient’s history
• Rule #6:
– When compensatory responses do not lie within
the accepted range, by definition a combined
disorder exists.
![Page 108: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/108.jpg)
Case #2:
• A 16 year old male with sickle cell anemia,
hemochromatosis, & subsequent cirrhosis,
presents with a several day history of
emesis. At presentation to the pedes ER, he
is hypotensive, orthostatic, and confused.
• What acid-base disorders might be
anticipated based on the above information?
![Page 109: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/109.jpg)
Case #3:
• 16 yo male with sickle cell anemia, hemo-
chromatosis, & subsequent cirrhosis, and
several days of emesis. In the pedes ER, he
is hypotensive, orthostatic, and confused.
• Emesis-loss of H+ (HCl)-metabolic alkalosis
• Orthostatic hypotension-?lactic acidosis
• SCD-decreased O2 delivery-?lactic acidosis
• Cirrhosis-decreased lactate metabolism
![Page 110: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/110.jpg)
Case #3:
• What baseline information is available?
• pH=7.55, PaCO2=66
• „lytes: Na+=166, K+=3.0, Cl-=90, HCO3=56
• Are the data internally consistent?
3
2
24HCO
PaCOH
![Page 111: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/111.jpg)
Case #3:
• [H+]~28, equates to pH~7.55; consistent
• What is the primary abnormality?
• “_________ Alkalosis”
• PaCO2ed, HCO3 ed, therefore…….
• “Metabolic Alkalosis” presumed due to
emesis
• Is compensation appropriate?
![Page 112: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/112.jpg)
Case #3:
• Metabolic Alkalosis
– PaCO2 should rise by .25 to 1 mm Hg x the rise
in plasma [HCO3]
• HCO3 ed by 32; PaCO2 should by 8-32
• PaCO2 ed by 26, so compensation appears
appropriate
• What about multiple risk factors for lactic
acidosis?
![Page 113: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/113.jpg)
Case #3:
• Could there be a concealed lactic acidosis?
• What is the anion gap?
• Na+- (Cl- + HCO3), normally 12-14
• Anion gap here is 166 - (90 + 56) = 20
• ed anion gap implies metabolic acidosis
• Combined metabolic alkalosis &
metabolic acidosis therefore present
![Page 114: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/114.jpg)
8 Sequential Rules:
• Rule #7: Always calculate the anion gap
• Often it is the only sign of an occult
metabolic acidosis
– acidotic patients partially treated with HCO3
– acidotic patients with emesis
• May be the only sign of metabolic acidosis
“concealed” by concomitant acid-base
disorders
![Page 115: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/115.jpg)
Causes of Anion Gap Acidosis:
• Endogenous acidosis
– Uremia (uncleared organic acids)
– Ketoacidosis, Lactic acidosis (increased organic
acid production), Rhabdomyolosis
• Exogenous acidosis
– ingestions: salicylate, iron; paraldehyde use
• Other Ingestions:
– Methanol toxicity, Ethylene Glycol toxicity
![Page 116: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/116.jpg)
Causes of normal Anion Gap Acidosis:
• Diarrhea
• Isotonic saline infusion
• Renal tubular acidosis
• Acetazolamide
• Ureterocolic shunt
![Page 117: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/117.jpg)
Anion Gap:
• Based on the concept of electroneutrality; the
assumption that the sum of all available cations=
the sum of all available anions. Restated as:
• Na+ + Unmeasured Cations (UC) = Cl- + HCO3 +
Unmeasure Anions (UA); conventionally restated:
• Na+-(Cl-+HCO3)=UA-UC=Anion Gap=12 to 14
![Page 118: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/118.jpg)
Anion Gap:
• Na+-(Cl-+HCO3)=UA-UC
• Serum albumin contributes ~1/2 of the total anion
equivalency of the “UA” pool. Assuming normal
electrolytes, a 1gm/dl decline in serum albumin
decreases the anion gap factitiously by 3 mEq/L.
Therefore an anion gap of 12 mEq/L is corrected
to 17-18 mEq/L when the serum albumin is half of
normal; this is an important correction factor in
settings of chronic illness or malnourished patients
![Page 119: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/119.jpg)
Case #3:
• A 3 year old is brought to the pedes ER at
~3am, stuporous and tachypneic. History is
remarkable for his parents having cleaned
out their medicine cabinet earlier that day.
An ABG and electrolytes have been
accidentally drawn by the nurse.
![Page 120: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/120.jpg)
Case #4:
• Available data: pH=7.53, PaCO2=12;
Na+=140, K+=3.0, Cl-=106, HCO3=10
• Are the data internally consistent?
3
224HCO
PaCOH
![Page 121: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/121.jpg)
Case #4:
• [H+]~29, so pH~7.51; data consistent
• What is the primary disturbance?
• “__________ Alkalosis”
• Which variable (PaCO2, HCO3) is deranged
in a direction consistent with alkalosis?
• ed PaCO2, ed HCO3; so “Respiratory
Alkalosis”
![Page 122: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/122.jpg)
Case #4:
• Is compensation appropriate?
• Acute respiratory alkalosis
– Plasma [HCO3] should fall by ~1-3 mmole/l for
each 10 mm Hg decrement in PaCO2, usually
not to less than 18 mmoles/l
• PaCO2 ed by ~30 mm Hg; HCO3 should
fall by 3-9 mmole/l; HCO3 is too great, so
superimposed metabolic acidosis
![Page 123: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/123.jpg)
Case #4:
• What is the anion gap?
• 140 - (106 + 10) = 24; elevated anion gap
consistent with metabolic acidosis
• What is the differential diagnosis?
• Combined (true) respiratory alkalosis and
metabolic acidosis seen in sepsis, or
salicylate intoxication
![Page 124: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/124.jpg)
Case #5:
• A 5 year old with Bartter‟s Syndrome is
brought to clinic, where she collapses. She
has recently been febrile, but history is
otherwise unremarkable. An ABG and
serum electrolytes are obtained: pH=6.9,
PaCO2=81; Na+=142, K+=2.8, Cl-=87,
HCO3=16
![Page 125: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/125.jpg)
Case #5:
• Are the data consistent?
• [H+]=122, pH~6.9; data are consistent
3
224HCO
PaCOH
![Page 126: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/126.jpg)
Case #5:
• What is the primary disturbance?
• “_________ Acidosis”
• Which variable (PaCO2, HCO3) is deranged
in a direction consistent with acidosis?
• Both; pick most abnormal value--
• “Respiratory Acidosis”
• Is compensation appropriate?
![Page 127: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/127.jpg)
Case #5:
• Acute Respiratory Acidosis
– Plasma [HCO3] should rise by ~1mmole/l for
each 10 mm Hg increment in PaCO2
• Since HCO3 is inappropriately depressed,
compensation is not appropriate, and there
is a concomitant metabolic acidosis as well
• What is the anion gap?
• AG=39, confirms metabolic acidosis
![Page 128: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/128.jpg)
Case #5:
• Combined Respiratory Acidosis and
Metabolic Acidosis; are there other
disorders present?
• What about the dx of Bartter‟s Syndrome?
• Bartter‟s Syndrome characterized by
hypokalemic metabolic alkalosis
• Does this patient have a concealed
metabolic alkalosis?
![Page 129: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/129.jpg)
Case #5:
• Anion gap is 39, or 25-27 greater than
normal
• Typically, increases in anion gap correlate
with decreases in HCO3
• Assuming a 1:1 relationship, as anion gap
increases by 25, HCO3 should fall by 25
• Starting HCO3 must have been 16 + 25 = 41
![Page 130: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/130.jpg)
Case #5:
• Therefore, starting HCO3 was ~41 mmol/l,
consistent with expected chronic metabolic
alkalosis. This metabolic alkalosis was
“concealed” by the supervening profound
metabolic and respiratory acidoses
associated with her arrest event.
• Final diagnosis: Metabolic alkalosis,
metabolic acidosis, & respiratory acidosis
![Page 131: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/131.jpg)
8 Sequential Rules; Rule #8
• Rule #8: Mixed Acid-Base Disorders
• Coexistant metabolic acidosis and
metabolic alkalosis may occur. Always
check the change in the anion gap vs.
decrement in bicarbonate to rule out a
concealed metabolic disorder.
![Page 132: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/132.jpg)
Case #6:
• A 3 year old toddler is brought to the ER at
3 am after being found unarousable on his
bedroom floor, with urinary incontinence.
EMS monitoring at the scene revealed sinus
bradycardia. One amp of D50W and 5 mg
of naloxone were given IV without
response. Vital signs are stable; respiratory
effort is regular, but tachypneic. He is
acyanotic.
![Page 133: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/133.jpg)
Case #6:
• Initial lab studies (lytes, ABG & urine tox
screen) are sent. Initial dextrostick is >800.
• Initial available data are:
• Na+=154, K=5.6, Cl=106, HCO3=5,
BUN=6 creatinine=1.7, glucose=804,
PO4=12.3, Ca++=9.8, NH4=160, serum
osms=517
• pH=6.80, PaCO2=33, PaO2=298
![Page 134: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/134.jpg)
Case #6:
• What is the primary disturbance?
• ________ Acidosis
• Metabolic Acidosis
• Is compensation appropriate?
• No; PaCO2 level is inappropriately high
• Are other disorders present?
• Respiratory acidosis (due to evolving coma)
![Page 135: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/135.jpg)
Case #6:
• What is our differential thus far?
– Anion gap vs. non-anion gap metabolic acidosis
– DKA, lactic acidosis, renal failure, ingestion
• The urine tox screen comes back negative
– What does urine tox screen actually screen for?
• The patient‟s IV falls out. He then has a
seizure, is incontinent of urine, and fills the
specimen bag you placed on ER arrival.
![Page 136: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/136.jpg)
Case #6:
• What is the calculated serum osmolality,
and does an osmolal gap exist?
• 2(Na) + BUN/2.8 + Glucose/18
– Calculated=355, Measured=517
• What is the most likely diagnosis?
• How can this be confirmed definitively?
– Review of urinalysis
– Serum ethylene glycol level
![Page 137: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/137.jpg)
Case #6:
Anion gap metabolic acidosis
Osmolal gap
Methanol, ethylene glycol
ethyl alcohol, isopropyl alcohol
![Page 138: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/138.jpg)
Gap-Gap
*AG excess/HCO3 deficit=
(Measured AG-12)/ (24-measured HCO3)
*Ratio <1 in presence of high AG acidosis means coexistance of normal AG metabolic acidosis
*Ratio >1 in presence of high AG acidosis means coexistance of metabolic alkalosis
![Page 139: Interpretation of arterial blood gases:Traditional versus Modern](https://reader034.vdocument.in/reader034/viewer/2022052218/554b568db4c905e9388b4c9b/html5/thumbnails/139.jpg)