Acid-Base Balance Flashcards

1
Q

What three mechanisms are used to defend against changes in body fluid pH?

A

Extra- and intracellular buffering

Adjustments in PCO2 by alterations in ventilatory rate

Adjustments in renal acid excretion

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2
Q

What is the most important extracellular buffer?

A

Bicarbonate buffering system, response is virtually instantaneous

*Other extracellular buffers are protein and Phosphate

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3
Q

What is intracellular buffering?

A

Involves H into and out of the cells

Inside the cells it is titrated by Phosphate and proteins

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4
Q

How is the respiratory mechanisms mediated?

A

Chemoreceptors sensing PCO2

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5
Q

What three things happen in the renal defense of acidosis?

A

Increase H secretion

Entire filtered load of bicarb is reabsorbed

Increased production and excretion of ammonia

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6
Q

What happens in the renal defense of alkalosis?

A

Decreased secretion of H

Decreased bicarb reabsorption

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7
Q

What is the primary alteration in metabolic acidosis/alkalosis?

A

Change in ECF bicarb concentration

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8
Q

Describe metabolic acidosis

A

Low plasma bicarb and low pH

Can develop by: addition of nonvolatile acid, Loss of nonvolatile alkali, failure of kidneys to excrete sufficient net acid

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9
Q

What is the anion gap?

A

Represents anions in the plasma that are not measured

Used to help in the differential diagnosis of metabolic acidosis

Normal is 16 (or 12 if K is not used in calculation)

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10
Q

What does metabolic acidosis with high anion gap indicate?

A

Decreased bicarbonate is replaced by unmeasured anions

DKA, salicylate poisoning, Lactic acidosis

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11
Q

What does metabolic acidosis with a normal anion gap indicate?

A

Decreased bicarb is replaced by Cl

Diarrhea, drainage of pancreatic juice

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12
Q

Describe metabolic alkalosis

A

Increased plasma bicarb and pH

Can develop by addition of noonvolatile alkali (antacid ingestion), loss of nonvolatile acid

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13
Q

What are the compensation mechanisms for metabolic alkalosis?

A

Hypoventilation, increased renal excretion of bicarbonate

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14
Q

Describe respiratory acidosis

A

Elevated PCO2 and reduced plasma pH

Can develop by, inadequate ventilation, impaired gas diffusion

Buffering occurs in the intracellular compartment only

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15
Q

What is the renal compensation for resp. acidosis?

A

Increase bicarb reabsorption and ammonium excretion

Takes several days, acute and chronic phases

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16
Q

Describe respiratory alkalosis

A

Reduced PCO2 and elevated plasma pH

Can develop by stimulation of the respiratory centers

Buffering is intracellular

17
Q

What is the renal compensation for resp. alkalosis?

A

Inhibition of bicarb reabsorption and reduced ammonium excretion

18
Q

What is a combined complex acid-base disorder?

A

Normal compensation for a primary acid/base disorder

19
Q

What is a combined simple disorder?

A

Describes a second acid/base disturbance compounding the first acid-base disturbance

E.g. respiratory failure followed by renal failure both resulting in acidosis (IRDS)

or a hyperventilating patient begins severe vomiting

20
Q

What is renal tubular acidosis?

A

Group of diverse conditions that cause non anion gap metabolic acidosis in the presence of normal GFR

Classified as type 1, 2, and 4

21
Q

What is type 1 RTA?

A

Distal RTA

Characteristics: impaired H secretion by the distal segments, urine pH>5.3

Renal defect: Decreased H-K ATPase, Increased tubule permeability, allowing H backflow

Etiology: Sjogren syndrome, Rheumatoid arthritis drugs

22
Q

What is type 2 RTA?

A

Proximal RTA

Characteristics: Impaired proximal Bicarb reabsorption, low plasma bicarb

Renal defect: Nonspecific tubule dysfunction or mutation in genes involved in bicarb reabsorption

Etiology: Fanconi syndrome, CA inhibitors

23
Q

What is type 4 RTA?

A

Hypoaldosteronism

Characteristics: impaired aldosterone release or response, urine pH < 5.3, hyperkalemia

Renal defect: Impaired Na reabsorption via epithelial Na channel

Etiology: Congenital hypoaldosteronism (addison disease), aldosterone resistance, diabetic nephropathy