Acids & Bases

Question 1

Henderson-Hasselbalch Equation

Answer 1

ph = pka + log [A-]/[HA]
pka = unique to each buffer system/acid

Question 2

Intracellular buffers

Answer 2

• organic phosphates
• proteins
• hemoglovin

Question 3

Extracellular buffers

Answer 3

• proteins
• albumin
• phosphate
• bicarbonate <==

Question 4

Bicarbonate Buffering System

Answer 4

H2CO3 H+ + HCO3-

H2CO3 H20 + CO2 (via carbonic anhydrase)

Question 5

Bicarb henderson-hassel

Answer 5

pH = 6.1 + log [HCO2-]/[.03*Paco2]

Question 6

Normal pH range

Answer 6

7.38 - 7.43 (~7.4)

Question 7

Acidemia

Answer 7

more acid in blod than normal (lower pH)

Question 8

Alkalemia

Answer 8

more base ==> higher pH

Question 9

Acid-base disturbances

Answer 9

• body try to compensate for pH disturbances: lungs regulate CO2 (minutes) & kidneys regulate bicarb (hours/days)
• compensation will NEVER completely correct to normal pH

Question 10

Respiratory acidosis

Answer 10

• increased CO2 ==> lower pH
• usually ineffective ventilation
• acute (before renal compensation) or chronic

Question 11

Compensation rules for respiratory acidsos

Answer 11

• acute: every 10 Torr increase in CO2 ==> pH decrease by 0.08
• chronic: every 1 torr increase ==> bicarb increase by 0.4

Question 12

Acute causes of Respiratory acidosis

Answer 12

• CNS depressants (opiates, alcohol)

- respiratory muscle fatigue (increased work of breathing)

Question 13

Chronic causes of Respiratory acidsosis

Answer 13

• central hypoventilation (e.g. obesity hypoventilation syndrome)
• neuromuscular disease (e.g. ALS)
• chronic lung disease (emphysema, bronchiectasis)
• hypothyroidism

Question 14

Respiratory Alkalosis

Answer 14

• too little CO2 ==> increased pH
• due to increased ventilation
• can

Question 15

Compensation rules for respiratory alkalosis

Answer 15

• acute: every 10 Torr decrease in CO2 ==> pH increase by 0.08
• chronic: every 1 torr decrease ==> bicarb decrease by 0.4

Question 16

Acute causes of Resp Alk

Answer 16

• pain
• anxiety/panic
• fever
• mechanical ventilation

Question 17

Chronic causes of Resp Alk

Answer 17

• living at altitude
• brain injury
• chronic salicylate toxicity
• pregnancy

Question 18

Metabolic acidosis

Answer 18

• increased acid ==> decreased HCO3- ==> lower pH
• respiratory compensation ==> increased ventilation resulting in decreased pCO2
• compensation rules:
• expected pCO2 = 1.5[HCO3-] + 8 +/-2 ==> “winter’s formula”

Question 19

Major categories of metabolic acidosis

Answer 19

• anion gap = [Na+] - ([Cl-] + [HCO3-]) ==> elevated anion gap indicates additional acid that is being buffered by bicarb ==> increased amount of unmeasured anions
• non-anion gap = loss of bicarbonate (e.g. via GI losses or renal losses)

Question 20

Causes of metabolic acidosis (anion gap)

Answer 20

• pneumonic: MUD PILES
• Methanol
• Uremia
• DKA
• propylene Glycol
• INH
• Lactate
• Ethylene Glycol
• Salicylates

Question 21

Causes of metabolic acidosis (non-anion gap)

Answer 21

• GI losses (i.e. diarrhea)
• Renal losses (RTA)
• Too much IV saline (increase Cl- w/loss of bicarb)

Question 22

Metabolic Alkalosis

Answer 22

• excess HCO3- results in higher pH
• rapid respiratory compensation w/decreased ventilation ==> increased pCO2
• will not hypoventilate to point of hypoxemia; thus not completely
• compensation rule: increased [HCO3-} of 1mEq/L increases PaCO2 by 0.7 Torr

Question 23

Causes of metabolic alkalosis

Answer 23

• vomiting or NG tube suction (via loss of gastric acid)
• ingestion of NaHCO3
• ingestion of other alkali
• hypovolemia
• diuretics

Question 24

Summary of Acid-Base Disturbances

Answer 24

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