Metabolic acidosis

Question 1

What is metabolic acidosis ?

Answer 1

• a build up of acid in the blood

Question 2

How can metabolic acidosis can occur ?

Answer 2

• increased production of acid,
• ingestion of acid,
• body can’t get rid of acid,
• excessive HCO3- loss from the kidneys or GI tract

All result in decreased HCO3- concentration in the blood

Question 3

Classifications of metabolic acidosis

Answer 3

• High anion gap metabolic acidosis

- Normal anion gap metabolic acidosis: also called hyperchloremic metabolic acidosis

Question 4

High anion gap metabolic acidosis, pathomechanism

Answer 4

• there’s an increased amount of H+ in the body -> binds to HCO3-, decreasing its concentration -> decreasing PH

But because plasma maintains its neutrality, the new anions from the organic acids accumulate, and as they’re not part of the equation -> causes an increase in anion gap.

So an increased anion gap means an accumulation of H+

Question 5

State different conditions leading to high anion gap metabolic acidosis

Answer 5

• Lactic acidosis, ex in HF
• Diabetic ketoacidosis
• Chronic renal failure
• ingestion of acids: oxalic acid (ethylene glycol), formic acid (methanol), hippuric acid (toluene)

Question 6

High anion gap metabolic acidosis: Lactic acidosis

Answer 6

• Lactic acidosis: decreased O2 delivery to tissues -> increased anaerobic metabolism -> lactic acid build up, as cells can’t break down glucose (O2 missing)

Question 7

High anion gap metabolic acidosis: Diabetic ketoacidosis

Answer 7

• Diabetic ketoacidosis: uncontrolled diabetes -> lack of insulin -> no utilization of glucose -> cells use fat for energy -> fat converted to ketoacids

Question 8

High anion gap metabolic acidosis: Chronic renal failure

Answer 8

• Chronic renal failure: inability of kidney to eliminate uric acid/sulfur containing acid

Question 9

High anion gap metabolic acidosis: ingestion of acids

Answer 9

• ingestion of acids: oxalic acid (ethylene glycol), formic acid (methanol), hippuric acid (toluene)

Question 10

Normal anion gap metabolic acidosis: why is it called hyperchloremic metabolic acidosis, and why does the anion gap remains normal

Answer 10

• HCO3- concentration is decreased, and as compensatory mechanism to maintain the plasma neutrality, kidney reabsorbs more Cl-, which is part of the anion gap equation, so anion gap remains normal, and over reabsorption of Cl- can be called hyperchloremic metabolic acidosis

Question 11

State different conditions leading to normal anion gap metabolic acidosis

Answer 11

• severe diarrhea

- type II renal tubular acidosis

Question 12

Normal anion gap metabolic acidosis: severe diarrhea

Answer 12

HCO3- rich intestinal and pancreatic secretions are eliminated before being reabsorbed

Question 13

Normal anion gap metabolic acidosis: type II renal tubular acidosis

Answer 13

The prox convoluted tubule is unable to reabsorb HCO3- (can be caused by carbonic anhydrase inhibitor)

Question 14

Body regulatory mechanisms used

Answer 14

• movement of H+ from blood to the cells
• respiratory system
• kidney system

Question 15

Body regulatory mechanisms: movement of H+ from the blood to the cells

Answer 15

• cells exchange H+ for K+ -> helps with acidosis, but causes hyperkalemia

Question 16

Body regulatory mechanisms: respiratory system

Answer 16

• chemoreceptors located in carotid arteries + aortic arch -> gets stimulated when pH decreases -> stimulates the respiratory centers in the brain -> increases breathing rate + depth -> increases the minute ventilation (volume of air moving in and out of the lungs in a minute) -> decreases PCO2 -> increases PH

Question 17

Body regulatory mechanisms: Kidney system

Answer 17

• takes several days

- kidney reabsorbs HCO3-

Question 18

Metabolic acidosis with high anion gap: how can It occur ? state examples

Answer 18

if the concentration of HCO3- and chloride both decrease, because of a high buildup of unmeasured anions
- hyperphosphatemia
- hyperalbuminemia
- IgA producing multiple myeloma
all causes an increased in unmeasured anions, which as compensatory mechanism -> results in a decrease in chloride concentration and bicarbonate concentration.

Question 19

Metabolic acidosis with low anion gap: how can it occur ? state the examples

Answer 19

• hypoalbuminemia

more rarely from an increase in unmeasured cations
- hyperkalemia
- hypercalcemia
- hypermagnesemia
- IgG producing multiple myeloma
All result in a decrease in sodium concentration -> decreases in the anion gap