Body Fluids & Electrolytes

Question 1

What is the 42L of water found in humans made up of ?

Answer 1

• 28L = Intracellular fluid
• 14L = extracellular fluids

Question 2

What are the subdivisions of extracellular fluids ?

Answer 2

3.5L = blood
10.5L = interstitial fluids

Question 3

What are some of the impacts of dehydration ?

Answer 3

• increased strain on heart
• headache/nausea
• fatigue
• slow reactions

Question 4

What are some factors that affect sweat rate ?

Answer 4

• external temp
• clothing
• exercise

Question 5

What are the basic steps of water balance in the body when there’s too much water ?

Answer 5

• hypothalamus detects water level
• pituitary glad releases ADH
• Less water is absorbed by kidneys
• results in more water lost in urine
• blood water level returns to normal

Question 6

What is the amount of water reabsorbed in the renal collection ducts proportional to ?

Answer 6

ADH release

Question 7

What occurs when ADH levels are low ?

Answer 7

• most of water in collecting ducts is not reabsorbed
• leading to large quantities of dilute urine

Question 8

What is ADH promotion/inhibition regulated by ?

Answer 8

the hypothalamus - responds to changes in solute conc. in extracellular fluid or large changes in blood pressure/volume of vascular baroreceptors

Question 9

Define plasma osmolality

Answer 9

refers to the conc. of all the solutes in the plasma

Question 10

Define hypo-osmolality

Answer 10

• swollen, ruptured cells

Question 11

Define hyper-osmolality

Answer 11

dried out, shrunken cells

Question 12

Why are the overall numbers of solute particles in body fluid the same ?

Answer 12

because the compartments are separated by semi-permeable membranes through which water moves to - this keeps osmolality the same

Question 13

What is osmolality expressed as ?

Answer 13

mmol/Kg

Question 14

What are Ion Selective Electrodes ?

Answer 14

they measure the activity of Na & K, which is related to conc.
- acitivity measurement is based on voltage established on the ISE in the presence of the specific ion

Question 15

What is the reference range for sodium ?

Answer 15

• 135-145 mmol/L

Question 16

Define Hyponatraemia

Answer 16

• decreased sodium level

Question 17

Define hypernatraemia

Answer 17

increased sodium levels

Question 18

What are the symptoms of Hyponatraemia ?

Answer 18

• level of consciousness altered
• orthostatic hypotension
• weak muscles
• seizures
• diarrhoea

Question 19

What causes hypervolaemic hyponatraemia ?

Answer 19

• congestive heart failure
• liver failure
• renal dysfunction

Question 20

What causes Euvolaemic hyponatraemia ?

Answer 20

• inappropriate ADH
• glucocorticoid deficiency
• water overload
• hypothyroidism
• post surgery

Question 21

What are some symptoms of Hypernatraemia ?

Answer 21

• flushed skin
• restless, irritable
• increased bp
• edema
• decreased urine output & dry mouth

Question 22

Describe the lab checklist for raised potassium

Answer 22

• check for evidence of haemolysis
• check for evidence of delayed arrival of specimen/centrifugation
• ensure correct collection tube

Question 23

Describe Hyperkalaemia

Answer 23

• increase in plasma potassium (severe > 7nmol/L)
• Affects heart as its made of muscle/nerves –> causes arrhythmia

Question 24

What is the most common cause of hyperkalaemia ?

Answer 24

• renal impairment

Question 25

Define pseudohyperkalaemia

Answer 25

- Artificial increase in serum potassium levels

Question 26

Describe hypoadlosteronism

Answer 26

- aldosterone deficiency , resistance or antagonism results in loss of sodium & water

Question 27

What is hypoaldosteronism commonly associated with ?

Answer 27

- Angiotensin - converting enzyme inhibitors - Angiotensin receptor blockers - Aldosterone antagonists (spironolactone)

Question 28

Define Rhabdomyelosis

Answer 28

- potassium is released from damaged cells

Question 29

Describe metabolic acidosis

Answer 29

- as conc. of hydrogen ions increases inside the cell the potassium ions are displaces from the cell into the plasma - this establishes electrochemical neutrality

Question 30

What can insulin deficiency lead to ?

Answer 30

- hyperkalaemia

Question 31

What can cause increased intake of potassium ?

Answer 31

- potassium salts of drugs - intravenously given potassium - blood products - stored red cells release potassium

Question 32

What is the reference range for plasma calcium ?

Answer 32

2.2 - 2.6 mmol/L

Question 33

What are some common causes of hypocalcaemia ?

Answer 33

- hypoparathyroidism - vitamin D deficiency - diseases affecting kidney/liver - medications

Question 34

Define hypocalcaemia

Answer 34

low levels of calcium

Question 35

What are some symptoms of hypocalcaemia

Answer 35

- muscle cramps - dry skin - brittle nails

Question 36

What are some causes of hypercalcaemia (>3.5 mmol/L) ?

Answer 36

- calcium supplementation - hyperparathyroidism - multiple myeloma -alcohol - neoplasm

Question 37

What are some functions of magnesium ?

Answer 37

- essential co-factor in formation of substrates of many enzymes - allosteric activator of many enzyme systems - membrane stabilisation - nerve conduction

Question 38

What can cause a magnesium deficiency ?

Answer 38

- inadequate dietary intake - GI diseases - alcoholism - cytotoxic drugs

Question 39

What are some symptoms of magnesium deficiency ?

Answer 39

- muscle spasms - weakness - numbness - stiffness - twitching - loss of appetite

Question 40

What are some causes for pseudohyperkalaemia relating to collection of sample ?

Answer 40

- difficulty in collecting sample - patient clenched fist when sample was taken - contamination with anticoagulant -cooling of sample - deterioration due to length of storage