Fluid-Electrolye Balance And Disturbances

Question 1

Threshold control

Answer 1

Freely available ionized Ca controls RMP threshold

Question 2

Resting membrane potential control

Answer 2

Controlled by leaky K channels

Question 3

RMP number in cardiac muscle

Answer 3

-90 mV

Question 4

Threshold number

Answer 4

-60 mV

Question 5

Acute hypokalemia

Answer 5

Resting membrane becomes more negative
Decreased excitability
Hyperpolarized
Increased automatic firing of Purkinje fibers causes arrhythmias

Question 6

Acute hyperkalemia

Answer 6

Resting membrane potential becomes more positive (closer to threshold)
More excitable
Hypopolarized

Question 7

Cardioplegic solution

Answer 7

K solution 15-40 mEq/mL
RMP is past the threshold
VGNaC stuck inactive state without repolarization

Question 8

Hypercalcemia

Answer 8

Ca problem raises threshold
Decreased excitability
Threshold becomes less negative

Question 9

Hyperkalemia with treatment

Answer 9

Ionized Ca Chloride treatment
RMP increased with increased K
Threshold also increased in Ca Chloride

Question 10

Hypocalcemia (in nerve)

Answer 10

Decreased threshold by calcium problem

Increased excitability

Question 11

RMP number is nerve cells

Answer 11

-70 mV

Question 12

Clinical application of hypocalcemia

Answer 12

1. Parathyroid glands removed causes decreased Ca
   Tetany can occur- motor nerves to muscles is hyperexcitable and fires APs spontaneously
2. Ca decreases when alkalosis develops
   Binds more to proteins in alkalosis
   Reduces freely ionized Ca
   Causes functional hypocalcemia (total number doesn’t change)

Question 13

Treatment of hyperkalemia

Answer 13

1. Give Ca (fastest treatment but doesn’t correct K)
2. Give bicarbonate- H+ concentration in plasma decreases (metabolic alkalosis), H+ shifts out of cells to buffer and K goes into cells
3. Hyperventilate- H+ concentration in plasma decreases (respiratory alkalosis) and same as above happens
4. Loop diuretics
5. Insulin and glucose- insulin stimulates Na K pump and drives K into cells, glucose treats hypoglycemia
6. A adrenergic agonist- stimulates Na K pump
7. Kayexalate
8. Dialysis

Question 14

Hyperventilation changes in K

Answer 14

For each 10mmHg decrease in PaCO2, serum K decreases by 0.5 mEq/L

Question 15

How hyperventilation lowers Ca

Answer 15

Normally both H+ and Ca bind plasma proteins
With hyperventilation, H+ decreases, proteins release H+, proteins are freed up and bind ionized calcium
Lowers plasma ionized calcium but not total

Question 16

Normal pH

Answer 16

7.35-7.45

Question 17

Normal HCO3

Answer 17

22-27 mEq/L

Question 18

Normal PaCO2

Answer 18

35-45 mmHg

Question 19

Determine acid base status

Answer 19

1. From pH, decide if pt is acidotic or alkalotic
2. From PaCO2 and HCO3, decide if its respiratory or metabolic
3. Determine if compensatory response has occurred

Question 20

Compensation

Answer 20

Respiratory acidosis and alkalosis can be completely compensated for
Metabolic can not reach complete compensation

Question 21

Normal anion gap

Answer 21

12 mM

Question 22

Anion gap formula

Answer 22

Anion gap= ([Na] + [K] - ([Cl] + [HCO3])

Question 23

Unmeasured anions

Answer 23

Proteins
HPO4
SO4

Question 24

Anion gap analysis

Answer 24

When non chloride acids are added to body fluids, there will be an increase in the anion gap. Cl does not change

When HCO3 is lost, Cl replaces HCO3. Anion gap does not decrease because Cl increases.

Elevated anion gap usually indicates metabolic acidsosis