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Renal > Acid base imbalances > Flashcards

Acid base imbalances Flashcards

1
Q

Henderson Hasselbach Equation

A

pH = pK + log [HCO3]/alpha*pCO2

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2
Q

What dose H+ secretion result in? in terms of HCO3

A

HCO3 reabsorption

Generation of new HCO3. only after after all filtered HCO3 has been reabsorbed

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3
Q

Where does HCO3 reabsorption and H+ secretion occur?

A

In the proximal tubule and collecting duct

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4
Q

How does H+ secretion in the proximal tubule occur?

A

In the cell: CO2+H2O –> HCO3- + H+

Na/H exchanger absorbs Na, pushes out H+ into the urine

H+ + HCO3 (freely filtered from glomerulus) –> H2O + CO2

The CO2 can diffuse back into the cell! This is the CO2 that we use in the first equation

Then that HCO3 from the first equation can go into the blood with the Na/HCO3 cotransporter

Net = Na reabsorbed, H+ excreted, bicarb reabsorbed into blood

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5
Q

How does H+ secreiton occur in the collecting duct?

A

H2O + CO2 –> H+ + HCO3-

The H+ is pumped into the lumen with H+ ATPase

In the lumen, NH3 combines with the H+ to form NH4+, which stayis in the urine

The HCO3 from the first equation goes into the blood with a Cl:HCO3 exchanger

Net: reabsorb one HCO3, excrete one H+

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6
Q

Metabolic acidosis: pH, primary, and compensation

A

pH<7.4

Primary: low HCO3

Compensation: low pCO2

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7
Q

Respiratory acidosis: pH, primary, and compensation

A

pH < 7.4

Primary: high pCO2

Compensation: high HCO3

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8
Q

Metabolic alkalosis: pH, primary, and compensation

A

pH >7.40

Primary: high HCO3

Compensation: high pCO2

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9
Q

Respiratory alkalosis: pH, primary, and compensation

A

pH >7.40

Primary: low pCO2

Compensation: low HCO3

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10
Q

What can cause metabolic acidosis?

A

Increased metabolic acid production: lactic or ketoacids

HCO3 losses: renal, non-renal (GI)

Renal failure

Acid ingestion

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11
Q

Formula for net acid excretion

A

NH4 + Titratable acid - HCO3

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12
Q

How does acid ingestion increase ammonia synthesis and excretion?

A

As you ingest more acid, your body makes and excretes more NH3

Up to a point!! It’s saturable

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13
Q

Which type of renal disease decrease NH3 production?

A

In tubulo-interstitial diseases, where you have atrophic tubules; when you get <20% normal nephrons, the daily NH3 production is too low so they present as acidotic!

Not in glomerular diseases, where they have normal tubules

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14
Q

What is the anion gap?

A

Na - (Cl+HCO3)

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15
Q

What does a high anion gap mean?

A

That metabolic acidosis is due to the presence of some unmeasured anion

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16
Q

What can cause high anion gap metabolic acidosis?

A

Lactic acidosis (lactate)

Diabetic ketoacidosis (beta-OH butyrate)

Renal failure

Toxins: salicylate (lactate, salicylate), ethanol (formate), ethylene glycol (oxalate)

17
Q

What can cause lactic acidosis?

A

Ischemia/hypoxia: ischemia, hypoxia due to pulm dz, severe anemia

With normal pO2: can be: severe exercise, malignancies, thiamine deficiency, severe liver dz

Drugs: metformin

D-lactic acidosis

18
Q

What causes diabetic ketoacidosis?

A

Insulin leads to increased glucose uptake into muscle but also increases lipogenesis

Low insuiln –> increased free fatty acid levels from lipolysis

19
Q

What are the 3 components of diabetic ketoacidosis?

A

Hyperglycemia (osmotic diuresis, volume depletion)

Metabolic acidosis

High anion gap (beta-OH butyrate, acetoacetate, somewhat elevated lactate levels)

20
Q

What can cause normal anion gap metabolic acidosis?

A

It’s going to be hypercholoremic

Can be due to non-renal HCO3 loss: diarrhea (bc increased Cl delivery to colon –> HCO3 secretion via Cl: HCO3 exchanger), uretero-sigmoidostomy

Renal HCO3 wasting

21
Q

What can cause proximal renal tubular acidosis?

A

Hereditary: cystinosis, hereditary fructose intolerance, CLC5 mutations, Lowe’s syndrome, Wilson’s dz, phosphorylase kinase deficiency, pyruvate carboxylase deficiency, CAII

Toxins: lead, mercury, cadmium, outdated tetracycline

Multiple myeloma

Renal transplant rejection

Hyperparathyroidism

Auto-immune dz: sjogren’s syndrome

22
Q

What can cause distal renal tubular acidosis

A

Mutations in: AE1, H+ ATPase, CAII, Mineralocerticoid receptor, epithelial Na channel

Toxins: amphotericin B, Li, toluene

Nephrocalcinosis

Sickle cell dz

Urinary obstruction

Autoimmune dz: sjogren’s syndrome

23
Q

What can cause type IV renal tubular acidosis?

A

Interstitial renal dz

Hyperkalemia

Hypo-reninemic hypoaldosteronism

24
Q

How can you get metabolic alkalosis?

A

Generation of excess HCO3: acid loss (vomiting, upper GI suction), HCO3 generation from metabolizable anions e.g. lactate, citrate, or beta-OH butyrate, HCO3 ingestion

Maintenance of excess HCO3: increased renal H+ secretion due to:

  1. decreased filtration rate
  2. volume depletion encourages proximal HCO3 reabsorption by high filtration fraction and AII stimulates Na/H exchanger
  3. high aldosterone increases collecting duct H+ secretion and HCO3 generation
25
Q

How can you get high aldosterone levels that can contribute to the alkalosis?

A
  1. primary hyperaldosteronism
  2. secondary hyperaldosteronism: high renin, high ang II
    - volume depletion
    - diuretics
    - CHF
    - cirrhosis of the liver
26
Q

How do respiratory acid/base abnormalities cause changes in pH?

A

Primary event is change in rate of ventilation leading to a change in blood pCO2

CO2 diffuses into the cell changing the cell pH, which in turn changes the cell calcium

Increased Calcium causes exocytosis of H+ ATPase containing vesicles

Decreased calcium causes their endocytosis

27
Q

What can cause respiratory alkalosis?

A

Hyperventilation due to:

Hypoxia

Lung dz - pneumonia

Heard dz - pulm edema

Liver dz

Cerebral dz- encephalitis, meningitis

Drugs- aspirin

Hormones- progesterone

28
Q

What is the most common acid-base disorder?

A

Respiratory alkalosis

29
Q

What can cause respiratory acidosis?

A

Hypoventilation

Lung disease: emphysema, chronic bronchitis, asthma

Tracheal obstruction

CNS: coma, stroke, central hypoventilation with obesity

Generalized muscle weakness: ALS, myasthenia gravis

Drugs: morphine and opiates in general

30
Q

What is the effect of metabolic acidosis in renal failure?

A

Increases the progression of renal failure

Unknown mechanism

Correcting the acidosis reduces the rate of progression

Renal (21 decks)

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