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Delicate balance of fluid and electrolytes
and acids and bases required to maintaingood health?
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Homeostasis
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Fluid within cells of body is known as?
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ICF
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K+
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Fluid located outside of cell is known as?
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ECF
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Major cation of ECF?
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Na+
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Movement of H2O across cell membranes
from less concentrated to moreconcentrated?
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Osmosis
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Substances dissolved in a liquid are known
as?
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Solutes
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The concentration within a fluid is known as?
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Movement of molecules in liquids from an
area of higher concentration to an areaof lower concentration is known as?
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Diffusion
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Fluid and solute move together across a
membrane from an area of psi to anarea of lower psi?
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Filtration
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Substance moves across cell membranes
from less concentrated solution to moreconcentrated solution – requires a
carrier?
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Active transport
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List some routes of fluid loss?
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Urine
Insensible fluid loss Feces
Perspiration
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List major electrolytes?
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Sodium
Potassium Chloride
Phosphate
Magnesium
Calcium
Bicarbonate
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Acid base balance is the regulation of ____
ions?
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Hydrogen
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The acidity or alkalinity of a solution is
measured as ____?
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pH
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The more ____ a solution the lower the pH?
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Acidic
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The more ____ the solution the higher the
pH?
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Alkaline
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7
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The ____ hydrogen ions, the more acidic the
solution and the lower the pH?
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More
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The lower the hydrogen concentration, the
more ____ the solution and the higher thepH?
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Alkaline
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Most important buffer system?
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Bicarbonate-carbonic acid buffer system?
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Lungs help regulate acid-base balance by
eliminating or retaining ____?
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Carbon dioxide
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Normal CO2 level?
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Kidneys are the ____ regulators of acid base
balance?
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Long-term
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Kidneys maintain pH balance by excreting or
conserving ____ and ____ ions?
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Bicarbonate, hydrogen
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Normal bicarbonate levels?
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Factors affecting homeostasis?
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Age
Gender Body size
Environment
Lifestyles
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List the acid base imbalances?
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Respiratory acidosis
Respiratory alkalosis Metabolic acidosis
Metabolic alkalosis
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Signs and symptoms of respiratory acidosis?
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Dyspnea
Disorientation Coma
Dysrythmias
Ph <7.35
PaCo2 >45
Hypokalemia Hyporemia
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Treatment for respiratory acidosis?
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Causes/etiology of respiratory acidosis?
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Respiratory alkalosis may be caused by
hyperventilation due to?
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Anxiety
Pain
Increased body temp
Overventilation with ventilator
Hypoxia
ASA overdose
Hypoxemia
CNS trauma/tumor
Emphysema Pneumonia
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Signs and symptoms of respiratory alkalosis?
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Tachycardia
SOB
CP
Syncope
Coma
Seizures
Numbness/tingling of extremities
Blurred vision
pH >7.45 CO2 < 35
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Treatment for respiratory alkalosis?
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Treat underlying cause
Assist client to breathe more slowly Breath in paper bag
Sedation
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Conditions that may lead to metabolic
acidosis?
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Renal failure
DKA Starvation
Lactic acidosis
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____ diarrhea may lead to metabolic
acidosis?
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Prolonged
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Signs and symptoms of metabolic acidosis?
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Kussmal’s respirations
Lethargy HA
Weakness
N/V
pH <7.35
Bicarb <22 CO2 >38
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Acid loss due to vomiting and gastric suction
may lead to ____ alkalosis?
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Metabolic
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Overuse of ____ may lead to metabolic
alkalosis?
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Signs and symptoms of metabolic alkalosis?
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Hyperventilation
Dysrhythmias Dizziness
Hypertonic muscle tetany
pH >7.45
Bicarb >26
Hypokalemia
hypocalcemia
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Treatment metabolic alkalosis?
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Give K+
Treat underlying cause
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List the normal values for
Ph
PaCO2
HCO3
PaO2
O2 sat
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7.35-7.45
35-4522-26
80-100
95-98%
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ROME stands for?
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R – respiratory
O – oppositeM – metabolic
E – equal (arrows go same direction as pH
arrow)
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ABG INTERPRETATION
Obj ti
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Objectives
What’s an ABG?
Understanding Acid/Base Relationship
General approach to ABG Interpretation
Clinical causes Abnormal ABG’s
Case studies
Take home
Wh t is ABG
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What is an ABG
Arterial Blood Gas
Drawn from artery- radial, brachial, femoral
It is an invasive procedure.
Caution must be taken with patient on anticoagulants.
Helps differentiate oxygen deficiencies from primary
ventilatory deficiencies from primary metabolic acid-base
abnormalities
What Is An ABG?
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What Is An ABG?
pH [H+
]
PCO2 Partial pressure CO2
PO2 Partial pressure O2
HCO3 Bicarbonate
BE Base excess
SaO2 Oxygen Saturation
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Case St d No 1
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Case Study No. 1
60 y/o male comes ER c/o SOB.
Tachypneic, tachycardic, diaphoretic and
Cyanotic. Dx acute resp. failure and ABG’s
Show PaCO2 well below nl, pH above nl,
PaO2 is very low. The blood gas document
Resp. failure due to primary O2 problem.
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Buffers
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There are two buffers that work in pairs
H2CO3 NaHCO3
Carbonic acid base bicarbonate
These buffers are linked to the respiratory
and renal compensatory system
Buffers
Respiratory Component
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Respiratory Component
function of the lungs
Carbonic acid H2CO3
Approximately 98% normal metabolites are in the form
of CO2
CO2 + H2O H2CO3
excess CO2 exhaled by the lungs
Metabolic Component
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Metabolic Component
Function of the kidneys
base bicarbonate Na HCO3
Process of kidneys excreting H+ into the urine and reabsorbing
HCO3- into the blood from the renal tubules
1) active exchange Na+ for H+ between the tubular
cells and glomerular filtrate
2) carbonic anhydrase is an enzyme that accelerates
hydration/dehydration CO2 in renal epithelial cells
Acid/Base Relationship
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H2O + CO2 H2CO3 HCO3 + H+
Acid/Base Relationship
Normal ABG values
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Normal ABG values
pH 7.35 – 7.45
PCO2 35 – 45 mmHg
PO2 80 – 100 mmHg
HCO3
22 – 26 mmol/L
BE -2 - +2
SaO2 >95%
Acidosis Alkalosis
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Acidosis Alkalosis
pH < 7.35
PCO2 > 45
HCO3 < 22
pH > 7.45
PCO2 < 35
HCO3 > 26
Respiratory Acidosis
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Respiratory Acidosis
Think of CO2 as an acid
failure of the lungs to exhale adequate CO2
pH < 7.35
PCO2 > 45
CO2 + H2CO3 pH
Causes of Respiratory Acidosis
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Causes of Respiratory Acidosis
emphysema
drug overdose
narcosis
respiratory arrest
airway obstruction
Metabolic Acidosis
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Metabolic Acidosis
failure of kidney function
blood HCO3 which results in availability of renaltubular HCO3 for H+ excretion
pH < 7.35
HCO3 < 22
Causes of Metabolic Acidosis
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Causes of Metabolic Acidosis
renal failure
diabetic ketoacidosis
lactic acidosis
excessive diarrhea
cardiac arrest
Respiratory Alkalosis
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Respiratory Alkalosis
too much CO2 exhaled (hyperventilation)
PCO2 , H2CO3 insufficiency = pH
pH > 7.45
PCO2 < 35
Causes of Respiratory Alkalosis
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Causes of Respiratory Alkalosis
hyperventilation
panic d/o
pain
pregnancy
acute anemia
salicylate overdose
Metabolic Alkalosis
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Metabolic Alkalosis
plasma bicarbonate
pH > 7.45 HCO3 > 26
Causes of Metabolic Alkalosis
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Causes of Metabolic Alkalosis
loss acid from stomach or kidney
hypokalemia
excessive alkali intake
How to Analyze an ABG
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How to Analyze an ABG1. PO2 NL = 80 – 100
mmHg
2. pH NL = 7.35 – 7.45
Acidotic <7.35
Alkalotic >7.45
3. PCO2 NL = 35 – 45 mmHg
Acidotic >45
Alkalotic <35
4. HCO3 NL = 22 – 26 mmol/L
Acidotic < 22
Alkalotic > 26
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F t ABG I t t ti
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Step 2:
pH acidosis <7.35alkalosis >7.45
Four-step ABG Interpretation
F st ABG I t t ti
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Step 3:
study PaCO2 & HCO 3
respiratory irregularity if PaCO2 abnl & HCO3 NL
metabolic irregularity if HCO3
abnl & PaCO2
NL
Four-step ABG Interpretation
F st ABG I t t ti
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Step 4:
Determine if there is a compensatory mechanism working
to try to correct the pH.
ie: if have primary respiratory acidosis will have increased
PaCO2 and decreased pH. Compensation occurs when
the kidneys retain HCO3.
Four-step ABG Interpretation
~ PaCO – pH Relationship
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~ PaCO2 – pH Relationship
80 7.20
60 7.30
40 7.40
30 7.50
20 7.60
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ABG Interpretation
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Compensated
Respiratory
Alkalosis
CO2
More Abnormal
Respiratory
Alkalosis
CO2
Expected
Mixed
Respiratory
Metabolic
Alkalosis
CO2
Less Abnormal
CO2 Change
c/w
Abnormality
Metabolic
Alkalosis
CO2
Normal
Compensated
Metabolic
Alkalosis
CO2 Change
opposes
Abnormality
Alkalosis
ABG Interpretation
Respiratory Acidosis
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Respiratory Acidosis
pH 7.30
PaCO2 60
HCO3 26
Respiratory Alkalosis
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Respiratory Alkalosis
pH 7.50
PaCO2 30
HCO3 22
Metabolic Acidosis
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Metabolic Acidosis
pH 7.30
PaCO2 40
HCO3 15
Metabolic Alkalosis
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Metabolic Alkalosis
pH 7.50
PCO2 40
HCO3 30
What are the compensations?
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Respiratory acidosis metabolic alkalosis
Respiratory alkalosis metabolic acidosis
In respiratory conditions, therefore, the kidneys will
attempt to compensate and visa versa.
In chronic respiratory acidosis (COPD) the kidneys increase
the elimination of H+ and absorb more HCO3. The ABG
will Show NL pH, CO2 and HCO3.
Buffers kick in within minutes. Respiratory compensation
is rapid and starts within minutes and complete within 24
hours. Kidney compensation takes hours and up to 5 days.
Mixed Acid-Base Abnormalities
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Mixed Acid Base Abnormalities
Case Study No. 3:
56 yo neurologic dz required ventilator support for several
weeks. She seemed most comfortable when hyperventilated
to PaCO2 28-30 mmHg. She required daily doses of lasix to
assure adequate urine output and received 40 mmol/L IV K+
each day. On 10th day of ICU her ABG on 24% oxygen & VS:
ABG Results
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ABG Results
pH 7.62 BP 115/80 mmHg
PCO2 30 mmHg Pulse 88/min
PO2 85 mmHg RR 10/minHCO3 30 mmol/L VT 1000ml
BE 10 mmol/L MV 10L
K+ 2.5 mmol/L
Interpretation: Acute alveolar hyperventilation
(resp. alkalosis) and metabolic alkalosis with corrected
hypoxemia.
Case study No. 4
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Case study No. 4
27 yo retarded with insulin-dependent DM arrived at ER
from the institution where he lived. On room air ABG & VS:
pH 7.15 BP 180/110 mmHg
PCO2 22 mmHg Pulse 130/min
PO2 92 mmHg RR 40/min
HCO3 9 mmol/L VT 800ml
BE -30 mmol/L MV 32L
Interpretation: Partly compensated metabolic acidosis.
Case study No. 5
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Case s dy o. 5
74 yo with hx chronic renal failure and chronic diuretic therapywas admitted to ICU comatose and severely dehydrated. On
40% oxygen her ABG & VS:
pH 7.52 BP 130/90 mmHgPCO2 55 mmHg Pulse 120/min
PO2 92 mmHg RR 25/min
HCO3 42 mmol/L VT 150ml
BE 17 mmol/L MV 3.75L
Interpretation: Partly compensated metabolic
alkalosis with corrected hypoxemia.
Case study No. 6
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s s y
43 yo arrives in ER 20 minutes after a MVA in which he
injured his face on the dashboard. He is agitated, has mottled,
cold and clammy skin and has obvious partial airway obstruction.
An oxygen mask at 10 L is placed on his face. ABG & VS:
pH 7.10 BP 150/110 mmHgPCO2 60 mmHg Pulse 150/min
PO2 125 mmHg RR 45/min
HCO3 18 mmol/L VT ? ml
BE -15 mmol/L MV ? L
.Interpretation: Acute ventilatory failure (resp. acidosis) and
acute metabolic acidosis with corrected hypoxemia
Case study No. 7
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s s y
17 yo, 48 kg with known insulin-dependent DM came to ERwith Kussmaul breathing and irregular pulse. Room air
ABG & VS:
pH 7.05 BP 140/90 mmHg
PCO2 12 mmHg Pulse 118/min
PO2 108 mmHg RR 40/min
HCO3 5 mmol/L VT 1200ml
BE -30 mmol/L MV 48L
Interpretation: Severe partly compensated metabolic
acidosis without hypoxemia.
Case No. 7 cont’d
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s
This patient is in diabetic ketoacidosis.
IV glucose and insulin were immediately administered. A
judgement was made that severe acidemia was adversely
affecting CV function and bicarb was elected to restore pH to
7.20.
Bicarb administration calculation:Base deficit X weight (kg)
4
30 X 48 = 360 mmol/L Admin 1/2 over 15 min &4 repeat ABG
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Case study No. 8
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y
47 yo was in PACU for 3 hours s/p cholecystectomy. She
had been on 40% oxygen and ABG & VS:
pH 7.44 BP 130/90 mmHgPCO2 32 mmHg Pulse 95/min, regular
PO2 121 mmHg RR 20/min
HCO3 22 mmol/L VT 350ml
BE -2 mmol/L MV 7LSaO2 98%
Hb 13 g/dL
Case No. 8 cont’d
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Oxygen was changed to 2L N/C. 1/2 hour pt. ready to be D/C
to floor and ABG & VS:
pH 7.41 BP 130/90 mmHgPCO2 10 mmHg Pulse 95/min, regular
PO2 148 mmHg RR 20/min
HCO3 6 mmol/L VT 350ml
BE -17 mmol/L MV 7LSaO2 99%
Hb 7 g/dL
Case No. 8 cont’d
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What is going on?
Case No. 8 cont’d
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If the picture doesn’t fit, repeat ABG!!
pH 7. 45 BP 130/90 mmHg
PCO2 31 mmHg Pulse 95/min
PO2
87 mmHg RR 20/min
HCO3 22 mmol/L VT 350ml
BE -2 mmol/L MV 7L
SaO2 96%
Hb 13 g/dL
Technical error was presumed.
Case study No. 967 yo who had closed reduction of leg fx without incident.
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67 yo who had closed reduction of leg fx without incident.
Four days later she experienced a sudden onset of severe
chestpain and SOB. Room air ABG & VS:
pH 7.36 BP 130/90 mmHg
PCO2
33 mmHg Pulse 100/min
PO2 55 mmHg RR 25/min
HCO3 18 mmol/L
BE -5 mmol/L MV 18L
SaO2 88%
Interpretation: Compensated metabolic acidosis with
moderate hypoxemia. Dx: PE
Case study No. 1076 yo with documented chronic hypercapnia secondary to
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76 yo with documented chronic hypercapnia secondary to
severe COPD has been in ICU for 3 days while being tx for
pneumonia. She had been stable for past 24 hours and wastransferred to general floor. Pt was on 2L oxygen & ABG &VS:
pH 7.44 BP 135/95 mmHg
PCO2 63 mmHg Pulse 110/minPO2 52 mmHg RR 22/min
HCO3 42 mmol/L
BE +16 mmol/L MV 10L
SaO2 86%
.Interpretation: Chronic ventilatory failure (resp. acidosis)
with uncorrected hypoxemia
Case No. 10 cont’d
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She was placed on 3L and monitored for next hour. She
remained alert, oriented and comfortable. ABG wasrepeated:
pH 7.36 BP 140/100 mmHg
PCO2 75 mmHg Pulse 105/min
PO2 65 mmHg RR 24/minHCO3 42 mmol/L
BE +16 mmol/L MV 4.8L
SaO2 92%
.
Pt’s ventilatory pattern has changed to more rapid and shallow breathing. Although still acceptable the pH and
CO2 are trending in the wrong direction. High-flow
oxygen may be better for this pt to prevent intubation
Take Home Message:
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Valuable information can be gained from an
ABG as to the patients physiologic condition
Remember that ABG analysis if only part of the patient
assessment.
Be systematic with your analysis, start with ABC’s as always
and look for hypoxia (which you can usually treat quickly),
then follow the four steps.
A quick assessment of patient oxygenation can be achievedwith a pulse oximeter which measures SaO2.
It’s not magic understanding
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It’s not magic understanding
ABG’s, it just takes a littlepractice!
Any Questions?
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References
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1. Shapiro, Barry A., et al; Clinical Application of Blood
Gases; 1994
2. American Journal of Nursing1999;Aug99(8):34-6
3. Journal Post Anesthesia Nursing1990;Aug;5(4)264-72
4. Irvine, David;ABG Interpretation, A Rough and Dirty
Production
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Answers to Practice ABG’s
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1. Respiratory alkalosis
2. Respiratory acidosis
3. Metabolic acidosis4. Compensated Respiratory acidosis
5. Metabolic alkalosis
6. Compensated Respiratory acidosis
7. Compensated Metabolic alkalosis
8. Metabolic acidosis
9 Respiratory acidosis