Body Fluids & Electrolytes Flashcards
What is the 42L of water found in humans made up of ?
- 28L = Intracellular fluid
- 14L = extracellular fluids
What are the subdivisions of extracellular fluids ?
3.5L = blood
10.5L = interstitial fluids
What are some of the impacts of dehydration ?
- increased strain on heart
- headache/nausea
- fatigue
- slow reactions
What are some factors that affect sweat rate ?
- external temp
- clothing
- exercise
What are the basic steps of water balance in the body when there’s too much water ?
- 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
What is the amount of water reabsorbed in the renal collection ducts proportional to ?
ADH release
What occurs when ADH levels are low ?
- most of water in collecting ducts is not reabsorbed
- leading to large quantities of dilute urine
What is ADH promotion/inhibition regulated by ?
the hypothalamus - responds to changes in solute conc. in extracellular fluid or large changes in blood pressure/volume of vascular baroreceptors
Define plasma osmolality
refers to the conc. of all the solutes in the plasma
Define hypo-osmolality
- swollen, ruptured cells
Define hyper-osmolality
dried out, shrunken cells
Why are the overall numbers of solute particles in body fluid the same ?
because the compartments are separated by semi-permeable membranes through which water moves to - this keeps osmolality the same
What is osmolality expressed as ?
mmol/Kg
What are Ion Selective Electrodes ?
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
What is the reference range for sodium ?
- 135-145 mmol/L
Define Hyponatraemia
- decreased sodium level
Define hypernatraemia
increased sodium levels
What are the symptoms of Hyponatraemia ?
- level of consciousness altered
- orthostatic hypotension
- weak muscles
- seizures
- diarrhoea
What causes hypervolaemic hyponatraemia ?
- congestive heart failure
- liver failure
- renal dysfunction
What causes Euvolaemic hyponatraemia ?
- inappropriate ADH
- glucocorticoid deficiency
- water overload
- hypothyroidism
- post surgery
What are some symptoms of Hypernatraemia ?
- flushed skin
- restless, irritable
- increased bp
- edema
- decreased urine output & dry mouth
Describe the lab checklist for raised potassium
- check for evidence of haemolysis
- check for evidence of delayed arrival of specimen/centrifugation
- ensure correct collection tube
Describe Hyperkalaemia
- increase in plasma potassium (severe > 7nmol/L)
- Affects heart as its made of muscle/nerves –> causes arrhythmia
What is the most common cause of hyperkalaemia ?
- renal impairment
Define pseudohyperkalaemia
- Artificial increase in serum potassium levels
Describe hypoadlosteronism
- aldosterone deficiency , resistance or antagonism results in loss of sodium & water
What is hypoaldosteronism commonly associated with ?
- Angiotensin - converting enzyme inhibitors
- Angiotensin receptor blockers
- Aldosterone antagonists (spironolactone)
Define Rhabdomyelosis
- potassium is released from damaged cells
Describe metabolic acidosis
- as conc. of hydrogen ions increases inside the cell the potassium ions are displaces from the cell into the plasma
- this establishes electrochemical neutrality
What can insulin deficiency lead to ?
- hyperkalaemia
What can cause increased intake of potassium ?
- potassium salts of drugs
- intravenously given potassium
- blood products - stored red cells release potassium
What is the reference range for plasma calcium ?
2.2 - 2.6 mmol/L
What are some common causes of hypocalcaemia ?
- hypoparathyroidism
- vitamin D deficiency
- diseases affecting kidney/liver
- medications
Define hypocalcaemia
low levels of calcium
What are some symptoms of hypocalcaemia
- muscle cramps
- dry skin
- brittle nails
What are some causes of hypercalcaemia (>3.5 mmol/L) ?
- calcium supplementation
- hyperparathyroidism
- multiple myeloma
-alcohol - neoplasm
What are some functions of magnesium ?
- essential co-factor in formation of substrates of many enzymes
- allosteric activator of many enzyme systems
- membrane stabilisation
- nerve conduction
What can cause a magnesium deficiency ?
- inadequate dietary intake
- GI diseases
- alcoholism
- cytotoxic drugs
What are some symptoms of magnesium deficiency ?
- muscle spasms
- weakness
- numbness
- stiffness
- twitching
- loss of appetite
What are some causes for pseudohyperkalaemia relating to collection of sample ?
- difficulty in collecting sample
- patient clenched fist when sample was taken
- contamination with anticoagulant
-cooling of sample - deterioration due to length of storage
