Acid Base Disorders

Question 1

Is pH and pCo2 calculated or measured?

Answer 1

Measured using electrodes in an analyzer

Question 2

Is HCO3 and BE calculated or measured?

Answer 2

Calculated from measured pH and pco2

Question 3

What knowledge do you need to determine acid-base status?

Answer 3

patient history, pH, pco2, HCO3

Question 4

What does calculating base excess do?

Answer 4

quantifies a metabolic disorder

Question 5

What is purpose of anion gap?

Answer 5

helps determine the metabolic source. (MUDPILES and FUSEDCARS)

Question 6

What does the “base” mean in base excess?

Answer 6

Sum of weak acid anions in plasma (hemoglobin, plasma proteins, phosphate, and bicarbonate)

Question 7

What is the same as base excess?

Answer 7

Strong ion difference (SID)

Question 8

How do you calculate base excess?

Answer 8

BE = calculated HCO3 - 24mEq/L (normal HCO3)

Question 9

What are our standard conditions?

Answer 9

37 degrees C, pH 7.40, Pco2 40

Question 10

What is our base excess at standard conditions?

Answer 10

0mmol/L !

Question 11

What can base excess be a useful predictor for?

Answer 11

severity of critical illness associated with hypovolemic shock and consequent metabolic acidosis

Question 12

What is normal base excess?

Answer 12

-2 to 2

Question 13

3 possible mixed acid-base disorder scenarios

Answer 13

1. pH 7.4 where respiratory and metabolic have opposite effects
2. pH <7.35 and both derangements contribute to acidosis
3. pH >7.45 and both derangements contribute to alkalosis

Question 14

Respiratory acidosis

Answer 14

pH <7.40, paco2 > 45 (ROME)

Question 15

Respiratory alkalosis

Answer 15

pH >7.4 paco2 <35 (ROME)

Question 16

Metabolic acidosis

Answer 16

pH <7.4 HCO3 <22 (ROME)

Question 17

Metabolic alkalosis

Answer 17

pH >7.4 HCO3 >26 (ROME)

Question 18

If both HCO3 and Paco2 are not outside their normal ranges is the disorder compensated, partially compensated, or uncompensated?

Answer 18

uncompensated!

Question 19

If both HCO3 and paco2 are both outside their normal ranges and pH is not in normal range changed in the same direction are they compensated, partially compensated or uncompensated?

Answer 19

partially compensated!

Question 20

if both HCO3 and paco2 are outside their normal ranges and changed in the same direction and pH was in normal range is the disorder compensated, partially compensated, or uncompensated?

Answer 20

fully compensated!

Question 21

if HCO3 and PaCO2 change in opposite directions outside their normal ranges and pH is 7.4 what does that indicate?

Answer 21

Mixed disorder!

Question 22

How do you calculate anion gap?

Answer 22

AG =. Na - Cl - HCO3

Question 23

What acid base disorder would you increase RR/Vt on the vent?

Answer 23

respiratory acidosis

Question 24

What acid base disorder would giving Naloxone (Narcan) benefit?

Answer 24

respiratory acidosis

Question 25

Which acid base disorder would you give bronchodilators?

Answer 25

respiratory acidosis d/t bronchoconstriction (asthma, COPD exacerbation)

Question 26

Which acid base disorder would you give Dantrolene?

Answer 26

metabolic acidosis d/t malignant hyperthermia

Question 27

Which acid base disorder would you give NaHCO3?

Answer 27

metabolic acidosis

Question 28

aerobic metabolism produces what kind of acids?

Answer 28

volatile acids (carbonic acid)

Question 29

anerobic metabolism produces what kind of acids?

Answer 29

nonvolatile acids (lactic acid, hydrogen phosphate)

Question 30

physiological effects of acidemia

Answer 30

myocardial and smooth muscle depression 1. reduction of contractility (decrease Co and BP- vasodilation) 2. reduced peripheral vascular resistance 3. less responsive to endogenous catecholamines 4. threshold for vfib decreased 5. coronary dilate, pulmonary constrict! tissue hypoxia: despite rightward shift of Hgb affinity for O2 progressive hyperkalemia 1. .6 mEq for .1 pH 2. K+ out, H+ in 3. risk for dysrhythmias cns depression: increased CBF and intracranial HTN (CO2 narcosis)

Question 31

what makes up majority of anion gap?

Answer 31

albumin (4mg/dL)

Question 32

physiological effects of alkalemia

Answer 32

K+ in, H+ out (hypokalemia) increases number of binding sites on plasma proteins for Ca2+ which decreases Ca2+ (circulatory depression and neuromuscular irritability) decreases CBF (vasoconstriction) increases SVR precipitate coronary vasospasm increase bronchial smooth muscle tone (bronchoconstriction) decrease pulmonary vascular resistance (vasodilation)

Question 33

anesthetic considerations for respiratory alkalosis

Answer 33

prolong the duration of opioid induced respiratory depression, general ischemia can occur with reduction in CBF especially if hypotensive

Question 34

how long does max respiratory compensation for metabolic disorder to occur?

Answer 34

12-24 hours

Question 35

how long does max renal compensation for respiratory disorder to occur?

Answer 35

3-5 days