Partial 6 - Acid-Base Disorders

Question 1

Hydrogen concentration in acidemia and alkalemia

Answer 1

Acidemia: H+ more than 45
Alkalemia: H+ less than 35

Question 2

If pCO2 doubles while HCO3 remains constant

Answer 2

pH will drop by 0.3 units

Question 3

If you reduce pCO2 by half

Answer 3

pH will rise by 0.3 units

Question 4

If HCO3 doubles while pCO2 remains constant

Answer 4

pH will rise by 0.3 units

Question 5

If you reduce HCO3 by half

Answer 5

pH will drop 0.3 units

Question 6

Henderson hasselback equation states that

Answer 6

pH is equal to pK plus the log of the ratio of the concentration of a base to its related acid.

Question 7

Normal concentration of bicarbonate

Answer 7

22-26 mmol/L

Question 8

Normal concentration of CO2

Answer 8

35-45 mmHg

Question 9

Normal concentration of hydrogen

Answer 9

40 nmol/L

Question 10

What happens to the potassium concentration in acidemia and alkalemia and why?

Answer 10

Acidemia produces hyperkalemia, and alkalemia produces hypokalemia due to potassium being exchanged for hydrogen between the cell and extracellular fluid

Question 11

Why can severe acidosis lead to osteodystrophy?

Answer 11

In severe acidosis the bones accept hydrogen and releases calcium

Question 12

Anion gap

Answer 12

The measured ions are sodium (Na+), chloride (Cl-) and bicarbonate.

The formula goes like this: Na + UC = Cl + HCO3 + UA.

Question 13

Unmeasured cations include

Answer 13

Potassium, calcium, and magnesium, and together these are 11 mEq/L.

Question 14

Unmeasured anions include

Answer 14

Sulfates, phosphates, Albumin, Lactic acid, and organic acids which together are 23 mEq/L

Question 15

Normal anion gap value

Answer 15

8-15

Question 16

Causes of increased anion gap

Answer 16

Accumulation of organic acids (ketones, lactate)

Toxic ingestions (methanol, ethylene glycol, salicylates)

Reduced inorganic acid excretion (phosphates, sulfates)

Decrease in unmeasured cations (decreased in unmeasured cations leads to increased measured cation because the blood is electroneutral).

Question 17

Increased anion gap value

Answer 17

more than 18

Question 18

Decreased/Negative anion gap causes

Answer 18

Decreased proteins (mainly albumin); There is 2-2.5 mEq/liter drop in AG for every 1 g drop in albumin.

Other etiologies; High potassium, magnesium, calcium, increased globulins
Lithium, bromide or iodine intoxication

Question 19

Increased globulins happens in which disease

Answer 19

Multiple myeloma

Increased lithium and bromide is also seen in multiple myeloma

Question 20

Compensation in acid-base disorders are rarely complete. In which cases are they complete?

Answer 20

High altitude and pregnancy (chronic respiratory alkalosis)

Question 21

Respiratory compensation to metabolic acidosis

Answer 21

Compensated by hyperventilation, called “kussmaul respiration” which is more deep than rapid, which means that it has high tidal volume

Question 22

Respiratory compensation to metabolic alkalosis

Answer 22

Hypoventilation, and is this is restricted by hypoxemia

Question 23

Metabolic compensation in acute hypercapnia

Answer 23

bicarbonate increases 1 mmol/L for each 10 mmHg increase in pCO2 more than 40

Question 24

Metabolic compensation in chronic hypercapnia

Answer 24

Bicarbonate increases 3.5 mmol/L for each 10 mmHg increase in pCO2 more than 40

Question 25

Metabolic compensation in acute hypocapnia

Answer 25

Bicarbonate decreases 2 mmol/L for every 10 mmHg decrease in pCO2 less than 40

Question 26

Metabolic compensation in chronic hypocapnia

Answer 26

Bicarbonate decreases 5 mmol/L for every 10 mmHg decrease in pCO2 less than 40

Question 27

Effects of metabolic acidosis

Answer 27

``` Vascular collapse Impaired cardiac contractility Increased pulmonary vascular resistance Inability to respond to catecholamines Decreased threshold for ventricular fibrillation Decreased hepatic and renal perfusion. ```

Question 28

Effects of alkalemia

Answer 28

Generalized and cerebral vasoconstriction Shift of oxyhemoglobin dissociation to left Hypokalemia Increased systemic vascular resistance Decreased contractility Cardiac arrhythmias refractory Seizures.

Question 29

Types of lactic acidosis

Answer 29

``` Type A (tissue hypoxia) Type B (normal oxygen, Paucity in NAD+, or excess NADH) ```

Question 30

Causes of Type A lactic acidosis

Answer 30

(1) Toxins such as iron, isoniazid, CN, methgb, CO, HS, and toluene (2) Shock states (3) Profound anemia (4) Massive catecholamines (5) Hypoxia (6) Anaerobic exertion, seizures, sprinting (7) Beriberi, total parenteral nutrition, and alcoholics

Question 31

Causes of Type B lactic acidosis

Answer 31

(1) Diabetes mellitus (2) Liver failure (3) renal failure (4) Carcinoma (5) Hypoglycemia (6) EtOH ingestion and many others Increased NADH leads to increased reduction of pyruvate to lactate.

Question 32

Causes of ketoacidosis

Answer 32

It can be due to increase in FFA load to liver, or increased conversion of FFA to ketoacids. Increased conversion of FFA to ketoacids may occur in diabetic ketoacidosis, in alcoholism, and to a lesser degree in prolonged starvation or a high-fat diet

Question 33

Causes of normal aniongap metabolic acidosis

Answer 33

(1) Loss of bicarbonate such as in chronic diarrhea, pancreatic fistulas, post-hypocapnia, uretroileostomy, acetazolamide (2) Failure to excrete hydrogen such as in renal tubular acidosis and adrenal insufficiency (3) Administration of hydrogen such as ammonium chloride, arginine hydrochloride, or aminoacidhydrochlorides

Question 34

Types of renal tubular acidosis

Answer 34

RTA1 involves failure of distal tubules to excrete hydrogen properly, while RTA2 involves bicarbonate wasting in proximal tubules, and both lead to normal AG metabolic acidosis, with hypokalemia. RTA4 is caused by lack of aldosterone and leads to hyperkalemia and acidemia.

Question 35

Causes of metabolic alkalosis

Answer 35

Hypochloremia Alkali ingestion Massive transfusion

Question 36

Causes of respiratory acidosis

Answer 36

Inadequate ventilation; (1) Head, chest, spinal cord trauma, (2) Sedative, hypnotics, (3) Neuropathy/myopathy, (4) Pulmonary disorder, (5) Airway obstruction, (6) Sleep apnea. Increased dead space ventilation; (1) COPD. Increased carbohydrate metabolism; (1) Total parenteral nutrition.

Question 37

Causes of respiratory alkalosis

Answer 37

1) Salicylates (stimulate medullary chemoreceptor) (2) increased intracranial pressure (3) Liver failure (due to NH3) (4) hypoxia, CHF, pericardial effusion, pulmonary embolus (5) hyperthyroidism (due to increased metabolism and CO2) (6) pregnancy (progesterone increases ventilation and lowers arterial pCO2 by as much as 5-10mmHG) (7) Sympathomimetics (amphetamines, cocaine, and phencyclidine) (8) Hyperventilation, in shock, sepsis, trauma/pain, psychogenic/anxiety (9) CNS disease.