SDL- Electrolyte Homeostasis Flashcards Preview

EMS- mod > SDL- Electrolyte Homeostasis > Flashcards

Flashcards in SDL- Electrolyte Homeostasis Deck (33):
1

What can an electrolyte imbalance cause a change in the following: Cardiovascular Physiology?

Blood pressure

2

What can an electrolyte imbalance cause a change in the following: Renal Physiology?

GFR

3

What can an electrolyte imbalance cause a change in the following: ElectroPhysiology?

Heart and CNS

4

What can cause Electrolyte imbalances?

Haemorrhage - accidents, surgery

D&V

Poor intake - elderly

Increased losses - pyrexia, heat

Diabetes insipidus

Diabetes mellitus

Diuretic therapy

Endocrine disorders - ADH, aldosterone

5

What would a Loss of 2L of isotonic fluid, e.g. blood, fistula fluid mean in teruuiui

Loss is from ECF

No change in [Na]

No fluid redistribution

6

What would a Loss of 3L of hypotonic fluid (dehydration) mean in terms for Sodium Conc?

Greater loss from ICF than ECF

Small increase in [Na]

Fluid redistribution between ECF & ICF

7

What would a Gain of 2L of isotonic fluid, e.g. saline drip do

Gain is to ECF

No change in [Na]

No fluid redistribution

8

What would a Gain of 3L of hypotonic fluid, e.g. water, dextrose do ?

Greater gain to ICF than ECF

Small decrease in [Na]

Fluid redistribution between ECF & ICF

9

Name some Physiological Compensatory mechanisms when electrolyte loss occurs?

Thirst
ADH
Renin / Angiotensin system

10

Name some Therapeutic Compensatory mechanisms when electrolyte loss occurs?

Intravenous therapy
Diuretics
Dialysis

11

What is ADH and its function?

Anti Diuertic Hormone (synthesised in Hypothalamus)

Produced by median eminence and release increases when osmolality rises
Decreases renal water loss
Increases thirst

12

Name some Simple tests to ascertain ADH status

measure plasma & urine osmolality
If the urine conc is higher than plasma suggests ADH is active

or

measure plasma & urine urea
urine >> plasma suggests water retention

13

What is the Renin-angiotensin system and its function?

Renin -> angiotensin -> aldosterone

Activated by reduced IVV (intravascular volume?)

Na depletion

haemorrhage

Causes renal Na retention

14

What are some Simple tests to ascertain R/A/A status?

measure plasma & urine Na
if urine

15

What would happen if you replaced lost fluid in a person with 2L isotonic fluid?

No change in [Na]
No fluid redistribution

16

What would happen if you replaced lost fluid in a person with 2L hypotonic fluid?

Fall in [Na]
Fluid redistribution
more fluid would move intracellular because [Na] would be higher?

17

Potential Clinical Problems : causes of Hyponatraemia?

Too little Na in ECF

Excess water in ECF

18

Potential Clinical Problems: causes of Hypernatreamia?

Too little water in ECF

Too much Na in ECF

19

What is Euvolaemia?

The presence of the proper amount of blood in the body

20

What is hypovolemia?

a decreased volume of circulating blood in the body

21

What is Hyponatraemia due SIADH

involves the excessive secretion of antidiuretic hormone (ADH) from the posterior pituitary gland or another source

causing the retention of water but not solute. Therefore ADH causes dilution of the blood which decreases the concentrations of solutes such as sodium

22

Hypernatraemia due to decreased water intake

Dec water intake ---> dec IVV ---> dec GFR ---> inc plasma [urea/creatine]

dec urine volume + inc urine Osmolality

Inc Renal {Na] reabsorption ---> dec urina [Na]

23

Hypernatraemia due to osmotic diuresis

glucose enter the kidney ---> inc urination ---> inc loss of water and Na

Because glucose does not penetrate cells in the absence of insulin , hyperglycemia further dehydrates the ICF compartment.

---> Less volume in blood = Haemoconcentration ---> inc Plasma [Na] + inc plasma Osmolality

24

What is the normal reference range of potassium

Potassium reference range - 3.6 to 5.0 mmol/L

Values 6.0 are potentially dangerous

Serum Potassium is measured

25

What can happen if a patients potassium is too low or too high?

Cardiac conduction defects
Abnormal neuromuscular excitability

26

Relationship of Potassium to Hydrogen Ions

K+ and H+ exchange across cell membrane

Both bind to negatively charged proteins (eg Hb)

Changes in pH cause shifts in the equilibrium

acidosis - potassium moves out of cells -> hyperkalaemia
alkalosis - potassium moves into cells -> hypokalaemia

27

What are causes of Hyperkalaemia?

Renal:
-Acute Renal Failure
-Chronic Renal Failure

Acidosis (intracellular exchange)

Mineralocorticoid Dysfunction:
-Adrenocortical failure
-Mineralocorticoid resistance - eg spironolactone

-Delay in sample analysis
-Haemolysis
-Drug therapy - Excess intake

Cell death
-Cytotoxic cell therapy

28

What would be the treatment 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 (bind potassium)

Dialysis
-short and long-term

29

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.

30

Effects of potassium depletion?

Acute changes in ICF/ECF ratios
-Neuromuscular:
-lethargy, muscle weakness, heart arrhythmias

Chronic losses from the ICF
-Neuromuscular:
-lethargy, muscle weakness, heart arrhythmias

Kidney:
-polyuria
-alkalosis - increase renal HCO3 production

31

How would you detect potassium depletion?

History:
-diarhoea, vomiting, drugs (diuretics, digoxin)
-symptoms of lethargy / weakness
-cardiac arythmias

Electrolytes investigation:
-hypokalaemia
-alkalosis - raised HCO3

32

Treatment of potassium depletion

Prevention
-Adequate supplementation

Replacement of deficit
-Oral/IV


Monitor plasma potassium regularly especially:
-Diuretic therapy
-Digoxin use
-Compromised renal function
-In support of IV resuscitation (eg DM Ketacidosis)

33

Hypernatreamia due to Aldosterone...

Aldosterone: increases reabsorption of ions and water in the kidney, to cause the conservation of sodium, secretion of potassium

---> can get Inc [Na] In the plasma