Diagnostics: ABG Flashcards by Bryan Edwards

Arterial Blood Gas testing is used to determine…

pH, PaCO2, PaO2

How well did you know this?

Not at all

Perfectly

What is an Allen’s test used to assess?

Whether blood flow is patent in both the radial and ulnar arteries

How well did you know this?

Not at all

Perfectly

Normal pH? Acidotic pH? Alkalotic pH?

Acidic – Below 7.35
Normal – 7.4
Alkalemia – Above 7.45

How well did you know this?

Not at all

Perfectly

Normal PaCO2. Differences in PaCO2 indicate…

40.

Ventilatory Problems

How well did you know this?

Not at all

Perfectly

Normal PaO2. Differences in PaO2 indicate…

100

Oxygenation problems

How well did you know this?

Not at all

Perfectly

For teaching purposes, the HH equation can be shortened to…

pH = (HCO3/PaCO2)

How well did you know this?

Not at all

Perfectly

Four kinds of primary acid-base disorders?

Metabolic/Respiratory Alkalosis/Acidosis

How well did you know this?

Not at all

Perfectly

Explain compensation

Changes in bicarb or PaCO2 that result from the primary event.

How well did you know this?

Not at all

Perfectly

Important rule about compensation

You NEVER over compensate

How well did you know this?

Not at all

Perfectly

Explain Respiratory Alkalosis

A primary disorder caused by lowering PaCO2
Kidney helps control by getting rid of bicarb
Caused by Anxiety/Hyperventilation

How well did you know this?

Not at all

Perfectly

Explain Respiratory Acidosis

Elevation of PaCO2, resulting in decreased pH
Kidneys retain bicarb to compensate
Heroin OD/Not breathing, Breathing high CO2 air

How well did you know this?

Not at all

Perfectly

Explain Metabolic Acidosis

Loss of HCO3
Compensation by hyperventilation
Causes vary with anion gap

How well did you know this?

Not at all

Perfectly

Explain Metabolic Alkalosis

Retention of too much HCO2
Slowed breathing rate
Contraction alkalosis, diuretics, steroids, gastric suctioning, VOMITING
Also – Cl resistant – hyperaldosterone

How well did you know this?

Not at all

Perfectly

How to calculate Anion Gap

Na - (Cl + CO2)

The CO2 is mostly Bicarb

How well did you know this?

Not at all

Perfectly

Normal Anion Gap value?

10-12 mEq/L

How well did you know this?

Not at all

Perfectly

Causes of increased anion gap metabolic acidosis?

MUDPILES

Methanol, Uremia, Diabetic Ketoacidosis, Paraldehyde, Infection, Lactic Acidosis, Ethylene Glycol, Salicyclates.

How well did you know this?

Not at all

Perfectly

Causes of normal anion gap metabolic acidosis

HARDUP
(Hyperchloraemia, Acetazolamide, Addison’s disease, Renal tubular acidosis, Diarrhea/Vomiting, Ureteroenterostomies, Pancreatoenterostomies)

How well did you know this?

Not at all

Perfectly

Expanded list of respiratory acidosis causes…

CNS Depression (Drug OD)
Chest Bellows Dysfunction (Guillian Barre, myasthenia)
Lung Disease (COPD, Severe Asthma, Severe Pulm. Edema)

How well did you know this?

Not at all

Perfectly

Expanded list of respiratory alkalosis causes..

Hypoxemia
Anxiety
Sepsis
Acute Pulm. Insult (Pneumonia, Mild Asthma Attack, Early pulm edema, pulm embolism)

In ACUTE respiratory situations, a pH drop of .08 correlated with a PaCO2 rise of…

In CHRONIC respiratory situations, a pH drop of 0.03 is correlated with a PaCO2 rise of…

Enough time for the kidneys to compensate by retaining bicarb

Co2 travels between the tissues and the lungs as…

bicarb

What is the Haldane effect?

Oxygenation of Hb promotes dissociation of H+, shifting equilibrium toward CO2 formation

What is…

FiO2, PaO2, SpO2, SaO2, Pi02

FiO2 = Fraction of inspired oxygen in the air (ex. 21%)
PaO2 = Arterial oxygen conc. (dissolved)
SpO2 = Bound Oxygen % via finger probe
SaO2 = Bound Oxygen % measured directly
PiO2 = Pressure of inspired oxygen in the trachea

First step in understanding a patient's oxygenation failures?

A-a gradient

What is an A-a gradient? | What does it mean when its high?

Alveolar Oxygen - Arterial Oxygen | Elevated with gas diffusion is impaired

Expected normal A-a gradient?

(Patient's Age/4) + 4

What kinds of hypoxia have a normal A-a gradient?

Pure Hypoventilation | Altitude

How do you calculate A-a gradient without Arterial Oxygen numbers?

PiO2 -(PaCO2/R) - PaO2 | R= Ration of Co2 produced to O2 consumed (.8)

PiO2 for folks around sea level

150

To qualify the degree of diffusion impairment or hypoxemia, you need to know what two (other than A-a gradient) relationships?

SpO2:PaO2 PaO2:FiO2

Oxygen Dissociation Curve Mneumonic

CADET, FACE RIGHT | Co2, Acidosis, 2,3 DPG, Exercise, Temperature

PaO2 should be about __x FiO2 | Normal PaO2:FiO2?

5X | 475

As severity of diffusion impairment increases, what happens to PaO2:FiO2 ratio?

The ratio decreases

Problem with the sigmoidal nature of the oxygen dissociation curve?

Because the slope is so shallow at saturations above 90, large diffusion defects can happen without notice

What to use A-a gradient vs. P:F ratio?

A-a gradient -- Works best on room air | P:F -- Works best with supplemental oxygen

What is indicated by a decreased V/Q?

Areas in the lung that are better perfused then ventilated

What is indicated by increased V/Q?

Areas that are better ventilated then perfused

V/Q mismatching occurs when?

In normal lungs based on lung zones

V/Q in the upper vs. lower lobes?

Upper -- 3 | Lower -- 0.6

With exercise, how does lung perfusion change in the lungs?

Vasodilation of apical capillaries | V/Q approaches 1

Causes of increase in V/Q

Pulmonary Embolism | Trachea

Causes of decreased V/Q

Emphyzema (non-functioning alveoli) Fibrosis (Poor diffusion of air) Secretions/Edema (Blocks diffusion of air)

What is a shunt? What are the two types?

Venous blood mixes with arterial blood, bypassing circulation. Extrapulmonary and Intrapulmonary

Examples of extrapulmonary shunts

Tetralogy of Fallot, PFO

Examples of intrapulmonary shunts

Blood transported thru lung w/out gas exchange. | Atelectasis, Pneumonia, Hepatopulmonary syndrome, AVM