Electrolyte homeostasis Flashcards Preview

EMS - Mechanisms of disease > Electrolyte homeostasis > Flashcards

Flashcards in Electrolyte homeostasis Deck (23):
1

What is measured by U&Es?

Sodium

Potassium

(Chloride)

(Bicarbonate)

Urea

Creatinine

2

Why might a person have abnormal electrolytes?

Primary disease state

Secondary consequence of a multitude of diseases

Iatrogenic problems are very common

3

What is important in the correction of abnormal electrolytes?

Maintenance of cellular homeostasis

Cardiovascular physiology - BP

Renal physiology - GFR

Electrophysiology - heart, CNS

4

What are the physiological water electrolyte homeostasis mechanisms?

Thirst

ADH

Renin / Angiotensin system

5

What therapeutic interventions are available?

Intravenous therapy

Diuretics

Dialysis

6

Where is ADH produced?

Produced by median eminence and release increases when plasma solute concentration rises.

7

What are the actions of ADH?

Decreases renal water loss

Increases thirst

8

What tests may be used to ascertain ADH status?

Measure plasma & urine solute concentration

- urine > plasma suggests ADH is active

 

Measure plasma & urine urea

- urine >> plasma suggests water retention (ADH active)

9

What are possible triggers for the renin-angiotensin system?

Na depletion

Haemorrhage

10

What are the actions of the renin-angiotensin system?

Renal Na retention

11

What test can be used to ascertain renin-angiotensin status?

Measure plasma & urine Na

- If urine < 10 mmol/L suggests R/A/A active

12

What is hyponatremia?

Too little Na in ECF

Excess water in ECF

13

What is hypernatremia?

Too little water in ECF

Too much Na in ECF

14

What is dehydration?

Water deficiency

Fluid (Na and water) depletion

15

What potassium serum values are dangerous?

Values 6.0 mmol/L are potentially dangerous

- Cardiac conduction defects

- Abnormal neuromuscular excitability

16

What is the relationship between potassium and hydrogen ions?

Changes in pH cause shifts in the equilibrium

- acidosis - potassium moves out of cells -> hyperkalaemia

- alkalosis - potassium moves into cells -> hypokalaemia

17

What are the possible causes of hyperkalaemia?

Artefactual

- Delay in sample analysis

- Haemolysis

- Drug therapy

- Excess intake

 

Renal

- Acute Renal Failure

- Chronic Renal Failure Acidosis (intracellular exchange)

 

Mineralocorticoid Dysfunction

- Adrenocortical failure

- Mineralocorticoid resistance - eg spironolactone

 

Cell Death

- Cytoxic therapy

18

What treatment is given for hyperkalaemia?

Correct acidosis if this is cause

Stop unnecessary supplements / intake

Give glucose & insulin - Drives potassium into cells

Ion exchange resins - GIT potassium binding

Dialysis - short and long-term

19

What are the possible causes of potassium depletion?

Low intake Increased urine loss

- diuretics / osmotic diuresis

- tubular dysfunction

- mineralocorticoid excess

 

GIT losses

- vomiting/diarrhoea/laxatives

- fistulae Hypokalaemia without depletion

- alkalosis

- insulin / glucose therapy.

20

What is the effect of acute potassium depletion?

Acute changes in ICF/ECF ratios

Neuromuscular:

- lethargy, muscle weakness, heart arrhythmias

21

What is the effect of chronic potassium depletion?

Chronic losses from the ICF:

Neuromuscular:

- lethargy, muscle weakness, heart arrhythmias

 

Kidney:

- polyuria

- alkalosis

- increase renal HCO3 production

22

What is the treatment for potassium depletion?

Prevention

- Adequate supplementation

Replacement of deficit

- oral - 48 mmol/day + diet

- IV - < 20 mmol/L

23

When is is appropriate to monitor potassium levels?

Diuretic therapy

Digoxin use

Compromised renal function

In support of IV resuscitation (eg DM Ketacidosis)