Clinical Acid Base

Question 1

how to determine pH of the body

Answer 1

ratio of serum HCO3 and PCO2

henderson hasselbach:
pH=6.1 + log (HCO3/CO2)

Question 2

respiratory acidosis

Answer 2

insufficient CO2 excretion by the lungs, high CO2 and low pH

Question 3

respiratory alkalosis

Answer 3

excess CO2 excretion, low CO and high pH

Question 4

metabolic acidosis

Answer 4

excess metabolic acids consume HCO3, normal CO2

Question 5

metabolic alkalosis

Answer 5

loss of metabolic acids causes excess HCO3, normal CO2

Question 6

cause of respiratory acidosis/alkalosis

Answer 6

hypoventilation/hyperventilation

Question 7

cause of metabolic acidosis/alkalosis

Answer 7

hypoxia, exercise, diabetes, EtOH, diarrhea

emesis, diuretics, excess ingestion of HCO3

Question 8

anion gap equation

Answer 8

Na- (Cl+HCO3)

Question 9

meaning of abnormal anion gap

Answer 9

abnormal is high, it means HCO3 is being consumed and other anions are in excess

helps identify acid-base insult

Question 10

what is Winter’s formula? and its purpose?

Answer 10

to determine if there has been a predictable respiratory compensation to metabolic acidosis

PCO2=1.5 (HCO3) +8 (+or - 2)

Question 11

compensation for respiratory acidosis

Answer 11

renal secretion of H+, increase HCO3

takes longer than respiratory compensation

Question 12

compensation for respiratory alkalosis

Answer 12

renal retention of H+ and decrease of HCO3

Question 13

compensation for metabolic acidosis

Answer 13

increased ventilation increases CO2 excretion, decreases PaCO2

Question 14

compensation for metabolic alkalosis

Answer 14

decreased ventilation increases PaCO2

Question 15

indications for invasive positive pressure ventilation

Answer 15

hypoxemic respiratory failure- improves V/Q mismatch, reduces work of breathing

hypercarbic respiratory failure

unstable airway in coma or uncontrolled seizure

Question 16

role of PEEP in mechanical ventilation

Answer 16

prevent alveolar collapse at end expiration- “positive end expiration pressure”

Question 17

differentiate volume vs pressure modes of mechanical ventilation

Answer 17

volume- fixed tidal volume, uses enough pressure to get there

pressure- fixed pressure, tidal volume variable

Question 18

mandatory vs non in mechanical ventilation

Answer 18

mandatory- set RR, can be either volume or pressure limited

non- no fixed RR, breaths are pt initiated
-can give pressure support in phases or continuously

Question 19

which settings to focus on for hypoxemia? hypercarbia?

Answer 19

FiO2 and PEEP for hypoxemia

minute ventilation (TV and RR) for hypercarbia

Question 20

normal ABG values, bicarb

Answer 20

7.4 (+ or - 0..05)/40/85-100, bicarb=24