acid-base

Question 1

ABG: where is blood drawn from

Answer 1

• usually radial artery
  
  • can be brachial or femoral

Question 2

what parameters are measured in ABG

Answer 2

• pO2
• O2 saturation
• pH
• pCO2
• HCO3

Question 3

normal pO2

Answer 3

80-100 mmHg

Question 4

normal O2 saturation

Answer 4

> 95%

Question 5

normal pH

Answer 5

7.35-7.45

Question 6

normal pCO2 values

Answer 6

35-45 mmHg

Question 7

normal HCO3 levels

Answer 7

22-26 mmol/L

Question 8

what two system can have a primary effect on arterial PaCO2 and cause abnormality in pH

Answer 8

• central nervous system
• respiratory system

Question 9

hyperventilation can cause

Answer 9

respiratory alkalosis

Question 10

hypoventilation can cause

Answer 10

respiratory acidosis

Question 11

which compensation method causes a rapid change

Answer 11

respiratory compensation

Question 12

full metabolic compensation for a respiratory process can take

Answer 12

3-5 days

Question 13

is the body able to fully compensate for primary acid-base disorders?

Answer 13

No

Question 14

if serum bicarbonate and arterial PCO2 move in opposite direction, what is going on?

Answer 14

mixed disorder

Question 15

clinical presentation

• hyperventilation
• ventricular arrhythmia
• altered mental status
• ABG: low pH, low bicarb, low PaCO2

Answer 15

• metabolic acidosis
• caused by: addition of H+ ions to serum or loss of bicarbonate

Question 16

how can you quickly determine what the PCO2 should be based on pH

Answer 16

• PCO2 same as decimal point of pH
  
  • pH=7.25 would have PCO2 = 25

Question 17

how is anion gap calculated? What is the normal range?

Answer 17

• AG= (Na + K) - (Cl) - (HCO3)
• normal = 8-12

Question 18

What are the conditions that can cause a high anion gap (AG >12)

Answer 18

MUDPILES

• methanol
• uremia (renal failure)
• DKA
• propylene glycol; paraldehyde
• iron/isoniazide
• lactic acidosis
• ethanol/ethylene glycol
• salicylate/starvation

Question 19

treatment of metabolic acidosis

Answer 19

• reverse underlying cause
• bicarbonate therapy

Question 20

What ion values maintains metabolic alkalosis

Answer 20

• hypokalemia
• hypocholemia

Question 21

clinical presentation

• lightheadedness, paresthesia
• orthostasis
• weakness
• polydypsia
• polyuria
• ABG: high pH, high bicarb, high PaCO2

Answer 21

metabolic alkalosis

Question 22

vomiting, nasogastic suction, thiazide and loop diuretics can cause what

Answer 22

• metabolic alkalosis
  
  • hypovolemic hypochloremic

Question 23

COPD, PE, myasthenia gravis, CNS dysfunction, and drug induced hypoventilation can cause

Answer 23

respiratory acidosis

Question 24

metabolic encephalopathy can cause

Answer 24

respiratory acidosis

Question 25

every 10mmHg increase in PaCO2 leads to what change in HCO3

Answer 25

1 mEq/L increase

Question 26

how can ABG help distinguish between acute and chronic respiratory acidosis

Answer 26

* acute: bicarb minimally changed * chronic: high bicarb

Question 27

anxiety, liver failure, gram negative sepsis, salicylate poisoning, pregnancy, and high altitude can lead to

Answer 27

respiratory alkalosis

Question 28

clinical presentation * lightheadedness * palpitations * circumoral paresthesias, acroparesthesias, carpopedal spasm * tachypnea

Answer 28

respiratory alkalosis

Question 29

every 10mmHg drop in PaCO2 causes what change in HCO3-

Answer 29

2 mEq/L drop in HCO3-

Question 30

what can you expect to see in chronic respiratory alkalosis

Answer 30

* high pH, low PaCO2, low bicarb * hyperchloremia * body's way of maintaining normal fluid volume in setting of bicarb loss * increased anion gap

Question 31

excessive vomiting with severe dehydration can cause

Answer 31

* mixed metabolic alkalosis and acidosis * hypochloremic alkalosis * lactic acidosis

Question 32

every 10 mmHg increase in PaCO2 has what effect on pH

Answer 32

pH drops 0.08 * ex: PaCO2 increased from 40-\>70 * 70-40 = 30: 3 (10) -\> 3 x 0.08 = .24 -\> 7.4-.24 = 7.16

Question 33

winters formula to calculate expected PCO2 compensation in metabolic acidosis

Answer 33

(1.5 x HCO3 + 8) +/- 2

Question 34

why is it important to differentiate between acute and chronic respiratory acidosis

Answer 34

* acute: may require emergent intubation and mechanical ventilation * chronic: often clinically stable (e.g. COPD)

Question 35

mineralocorticoid excess: primary aldosteronism, cushing, increased renin can cause

Answer 35

metabolic alkalosis

Question 36

to help determine cause of metabolic acidosis, look at

Answer 36

anion gap

Question 37

if the anion gap is \> or = 20, what does this indicate

Answer 37

* that a **primary metabolic acidosis** is present, regardless of pH or bicarb level

Question 38

if anion gap is increased, what should you calculate? What is it used for?

Answer 38

* **excess anion gap** * excess = total AG - normal AG (12) * add excess AG to measured HCO3 * **if the sum of the excess AG + measured HCO3 \> a normal HCO3- then an underlying metabolic alkalosis is present**, regardless of pH or measured bicarb