Sodium and Water Flashcards
what are U&E’s
urea and electrolytes
such as Na, K, Cl, HCO3, urea and creatinine
what are the basic subtypes of abnormal electrolyte disorders
can indicate primary state disease
secondary consequence of a multitude of diseases
why, physiologically, are electrolytes important
maintenance of cellular homeostasis
implications on cardiovascular physiology
implications on renal physiology
electrophysiology (CNS, heart)
what are some clinical examples of electrolyte disturbances
haemorrhage D&V poor intake increased losses DI DM diuretic therapy endocrine disorders (ADH, aldosterone)
what are the 5 concepts of electrolyte balance
concentrations, compartments, contents, volumes rates of gain and loss
what does the concentration of electrolytes depend on
water in and out
what is the normal Na+ plasma conc
140 mmol/L
what would happen to electrolyte conc in decreasing or increasing ECF/ICF fluid volume
decreasing ICF/ECF = increase conc of electrolyte in plasma
increasing ICF/ECF = decreased conc of electrolyte in plasma
what happens when you lose isotonic fluid
nothing as conc roughly same as blood, no change in conc and no fluid redistribution
cell shrink
what happens when you lose hypotonic solution
eg water and fluid of lower conc than blood
greater loss from ICF than ECF = increase in Na conc
cell shrink
what happens when you gain isotonic fluid
no change in conc but an increase in BP
cell oedema
what happens when you gain hypotonic fluid
greater gain to ICF than ECF
small decrease in Na
causes cell oedema
what are the three physical compensatory mechanisms of alter electrolyte balance
thirst
ADH
RAS
what is the role of ADH is electrolyte balance
produced by median eminence with increased water osmolality
decreases water loss and increase water retention
increases thirst
how does the RAS aid electrolyte balance
renin - angiotensin - aldosterone
activated by reduced vascular volume, sodium depletion or haemorrhage
causes renal sodium retention
what are two therapeutic techniques for electrolyte imbalance
IV therapy
diuretics
what is hyponatraemia, hypernataemia, dehydration in terms of water and sodium
hypo - small Na in ECF with excess water
hyper - large Na in ECF with small water
Dehy - na and water depletion
how is hyponatraemia caused by diuretics
decrease in urine Na re-absoprtion so more na released in urine which decreases GFR and increases plasma creat, urea and ADH
how is hyponatraemia caused by SIADH
syndrome of inappropriate ADH
stops water loss so dilutes Na in your system
describe how hypernatreamia is caused by decreased water intake
less water = more Na conc in blood, increase in urine osmolality and decrease in urine volume
increase in plasma creat and urea
describe how hypernatraemia is caused by osmotic diuresis
increase in plasma glucose which increases renal loss - this increase haemoconcentraiton and increases plasma Na conc
also increases plasma creat and urea
