Pulmonology Labs/ABGs- Schoenwald final exam Flashcards
What is the main function of arterial blood gases?
Maintenance of normal pH required for normal organ function
Arterial blood gases (ABGs) measure arterial pH, pO2, pCO2, bicarbonate and __ saturation
O2
Name the primary buffer system of the body
Carbonic acid/bicarbonate system
CO2=
acid
CO2 concentration is regulated by the ______
lungs
Bicarb=
base
Bicarbonate concentration is regulated by the _____
kidneys
Equation of Life
HCO3¯+H+«—-»H2CO3«—-»CO2+H2O
Bicarb + hydrogen–> carbonic acid–>Co2 and water (note arrows can go either direction
Equation of life is controlled by which organs?
lungs and kidney
Pathology in the lungs and kidneys is associated with _____ disorders
acid/base
Lungs excrete ____
CO2
Increased blood CO2 levels=
respiratory acidosis
Decreased blood CO2 levels=
respiratory alkalosis
Increased blood bicarbonate=
metabolic alkalosis
Decreased blood bicarbonate=
metabolic acidosis
When should you order ABGs?
on critically ill patients
ABGs help monitor _______ patients
ventilated
Normal pH range
7.36-7.44
A pH above 7.45 is ______
alkalotic
normal pCO2 range
35-45 mmHg
pCO2 provides info about ___
lung function & CO2 excretion
pCO2 represents the ____ part of the equation of life
acid. It’s a measurement of ventilation
elevated pCO2 level implies ______ ventilation
inadequate
Describe normal blood carriage
10% plasma
90% RBCs
Venous blood has higher levels of _____
pCO2
Normal pO2 range
80-100 mmHg
pO2 provides info on…
oxygenation of blood
normal pO2 provides _____ _____ delivery to tissues
adequate O2
What level of pO2 suggests significant reduction in hgb saturation and impaired O2 delivery?
levels <60
What causes decreased pO2 due to poor O2 gas diffusion?
pneumonia, CHF
pO2 is low in ______ blood
venous
Normal Bicarb range
22-26 mEg/L
Total ____ value is actually the bicarb measurement
CO2 (from electrolyte panel)
Some labs report the base deficit which represents the amount of:
buffering anions in the blood (HCO3+hgb, phosphate, proteins
Negative base excess=
metabolic acidosis
Positive base excess=
metabolic alkalosis or compensation to respiratory acidosis
Causes of Respiratory Alkalosis (list 3)
- Hyperventilation
- Anxiety
- Overventilation of patients on ventilators
Respiratory alkalosis:
pH?
pCO2?
pH would be increased (>7.45) and pCO2 would be decreased
Causes (or conditions associated with) Respiratory acidosis
- COPD
- Asthma
- Drug overdose
- Pneumonia-due to poor gas exchange
- Hypoventilation
Respiratory Acidosis:
pH?
pCO2?
pH= low, pCO2= increased
Metabolic alkalosis is caused by a loss of ______
gastric acid (i.e. vomiting), or from diuretic usage
Metabolic alkalosis
pH is elevated, HCO3 is slightly increased
Which conditions are associated with metabolic acidosis?
- Diabetics-ketoacidosis
- Starvation
- Alcoholics
- Lactic acidosis
Metabolic Acidosis:
pH?
HCO3?
pH= low
HCO3=low
MUDPILES
M-Methanol U-Uremia D-Diabetic Ketoacidosis P-Propylene glycol I-INH or Iron L-Lactic Acid E-Ethanol S-Salicylates
–>Anion gap metabolic acidosis (AGMA) is a common scenario in critically ill patients. Common causes are often implied by the acronym, MUDPILES
Electrolyte panel (list the normal ranges): Na (norm \_\_\_\_\_ meq/l) K (norm \_\_\_\_\_\_\_ meq/l) CL (norm \_\_\_\_\_ meq/l) CO2 (\_\_\_\_\_ meq/l)
Na: 135-145
K: 3.5-4.5
CL: 98-106
CO2: 23-30
_____ is the main regulator of water and sodium
Kidney
Electrolyte panel can be used to measure the _____
anion gap
Normal anion gap range
3-11 mEq/L
The anion gap= the difference b/w cations and ____ in the extracellular space
anions
Anion gap equation
Na- (Cl+CO2)
A higher anion gap (above 11) is indicative of..
If increased, indicates increase in negatively charged, weak acids
=metabolic acidosis
Important for body to remain ______ _______- ie numbers of positive and electric charges should be equal
electrically neutral
Interpreting ABGs (4 steps)
- Look at the pH
is the primary problem acidosis (low) or alkalosis (high) - Check the CO2 (respiratory indicator)
is it less than 35 (alkalosis) or more than 45 (acidosis) - Check the HCO3 (metabolic indicator)
is it less than 22 (acidosis) or more than 26 (alkalosis) - Which is primary disorder (Resp. or Metabolic)?
If the pH is low (acidosis), then look to see if CO2 or HCO3 is acidosis (which ever is acidosis will be primary).
If the pH is high (alkalosis), then look to see if CO2 or HCO3 is alkalosis (which ever is alkalosis is the primary).
The one that matches the pH (acidosis or alkalosis), is the primary disorder.
Normal pH range=
Normal PCO2 range=
Normal HCO3 range=
pH –> 7.35-7.45
PCO2–> 35-45
HCO3 –> 22-26
pH of 7.9=
alkalosis
pH of 7.3=
slight acidosis
PCO2 of 29=
alkalosis
HCO3 of 33=
alkalosis
The Respiratory system and Renal systems _______ for each other
compensate (attempt to return the pH to normal)
ABG’s show that compensation is present when:
the pH returns to normal or near normal
If the nonprimary system is in the normal range (CO2 35 to 45) (HCO3 22-26), then:
that system is not compensating for the primary.
For example:
In respiratory acidosis (pH<7.35, CO2>45), if the HCO3 is >26, then the kidneys are compensating by retaining bicarbonate.
If HCO3 is normal, then not compensating.
When obtaining ABGs, -Ensure ______ vs venous collection
arterial
Common sites to obtain ABGS
Brachial and radial arteries
What is the Allen test used to evaluate?
Used for evaluation of collateral circulation of radial artery
Allen test– this is NOT on Schoenwald’s slides! This sums up what the test measures and how it’s performed
Allen test:
Instruct the patient to clench his or her fist; if the patient is unable to do this, close the person’s hand tightly.
Using your fingers, apply occlusive pressure to both the ulnar and radial arteries, to obstruct blood flow to the hand.
While applying occlusive pressure to both arteries, have the patient relax his or her hand, and check whether the palm and fingers have blanched. If this is not the case, you have not completely occluded the arteries with your fingers.
Release the occlusive pressure on the ulnar artery only to determine whether the modified Allen test is positive or negative.
Positive modified Allen test – If the hand flushes within 5-15 seconds it indicates that the ulnar artery has good blood flow; this normal flushing of the hand is considered to be a positive test.
Negative modified Allen test: – If the hand does not flush within 5-15 seconds, it indicates that ulnar circulation is inadequate or nonexistent; in this situation, the radial artery supplying arterial blood to that hand should not be punctured.