Acid-Base Disorders Flashcards

1
Q

What does pH represent?

A

The [ ] of free hydrogen ions (protons) in circulation

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2
Q

What is normal human pH?

A

7.4

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3
Q

What pH level of extracellular fluid must be maintained for optimal functioning of body cells?

A

7.35-7.45

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4
Q

What is pH > 7.4?

A

alkalosis

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5
Q

What is pH < 7.4?

A

acidosis

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6
Q

What is an acid?

A

A molecule that releases hydrogen ions in solution

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7
Q

What is a base?

A

Any substance that can accept a hydrogen ion (removes free protons from solution)

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8
Q

What are 3 ways the body eliminates acids?

A

(1) pulmonary excretion of CO2
(2) metabolic utilization of organic acids
(3) renal excretion of nonvolatile acids (H+ + buffers)

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9
Q

Excess CO2 causes a(n) (inc/dec) in H+ leading to an (acidic/alkalotic) pH level in the body.

A

Inc in H+ → acidic

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10
Q

Excess HCO3- causes a(n) (inc/dec) in H+ leading to an (acidic/alkalotic) pH level in the body.

A

Dec in H+ → alkalotic

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11
Q

What are 4 sources of H+ gain?

A

(1) inc CO2
(2) production of phosphoric and sulfuric acids-metabolism of proteins and other organic molecules
(3) loss of bicarb from GI losses
(4) loss of bicarb from urine

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12
Q

What are 2 sources of H+ loss?

A

(1) loss of H+ in vomit

(2) loss of H+ in urine

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13
Q

Hypoventilation or respiratory diseases result in what?

A

Retention of CO2→ respiratory acidosis

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14
Q

Hyperventilation results in what?

A

Blowing off CO2→ respiratory alkalosis

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15
Q

What are 3 common causes of metabolic acidosis?

A

(1) excess production of lactic acid (>4 mEq/L): severe exercise or seizure, shock/hypoxia
(2) formation of ketone bodies: uncontrolled DM, fasting states
(3) loss of bicarbonate: diarrhea

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16
Q

What is the anion gap?

A

Difference b/w the plasma [ ] of the major cation (Na+) and the sum of the measured anions (Cl- and HCO3-) → AG = Na+ - [Cl- + HCO3-]

17
Q

What does the difference of the anion gap represent?

A

The [ ] of unmeasured anions such as phosphates, sulfates, organic acids and proteins

18
Q

What is responsible for a normal anion gap?

A

Excessive bicarbonate loss either intestinally or renally

19
Q

What 2 things are responsible for an elevated anion gap?

A

Excess metabolic acid production and impaired elimination of metabolic acids; kidney dysfunction

20
Q

What is the most common cause of metabolic acidosis in hospitalized pts?

A

Lactic acidosis

21
Q

What are the 2 types of lactic acidosis? Describe each and say which is the most common.

A

Type A (hypoxic): most common

  • Dec tissue perfusion→ inc lactic acid production
  • Ex: cardiogenic, septic, hemorrhagic shock, carbon monoxide or cyanide poisoning

Type B (metabolic causes):

  • Impaired cellular metabolism or tissue ischemia w/o systemic hypoperfusion
  • Ex: DKA, alcoholism, infxns, malignancy, metformin, bowel necrosis
22
Q

What does the AG metabolic acidosis mnemonic MUDPILES stand for?

A
Methanol 
Uremia 
DKA 
Propylene glycol Isoniazid 
Lactic acidosis 
Ethylene glycol and ethanol 
Salicylates (aspirin) and starvation
23
Q

What are 4 causes of metabolic alkalosis?

A

(1) ingestion or admin of alkali
(2) stomach loss of H+
(3) renal loss of H+
(4) diuretic use

24
Q

What are 4 causes of contraction alkalosis?

A

(1) loss of large volumes of bicarb free fluid
(2) bicarb [ ] remains constant
(3) admin of IV loop diuretics is the most common cause
(4) NaCl loss in cystic fibrosis

25
Q

What causes impaired chloride reabsorption?

A

Diuretics block Cl reabsorption and further enhance NaHCO3 reabsorption

26
Q

What affect does hypercalcemia have on bicarbonate?

A

Hypercalcemia reduces GFR→ inc bicarb reabsorption

27
Q

A respiratory problem is suspected when there is a change in what?

A

pCO2

28
Q

A metabolic problem is suspected when there is a change in what?

A

HCO3-

29
Q

What are 3 renal responses to acidosis?

A

(1) bicarb in kidneys binds up as much H+ as possible
(2) additional H+ are excreted bound to other buffers
(3) new bicarb is formed during tubular glutamine metabolism

30
Q

What are 3 renal responses to alkalosis?

A

(1) H+ binds as much bicarb as possible
(2) bicarb is excreted in urine
(3) tubular glutamine metabolism is decreased to lower new bicarb production

31
Q

What are the initial 3 steps to interpreting ABG?

A

1: acidosis vs. alkalosis (look at pH)
2: does pCO2 explain the problem? (elevated in acidosis, dec in alkalosis)
3: yes pCO2 explains problem= respiratory, no= metabolic