Urinary Pharmacology Flashcards
What % of body weight is water in adults and neonates?
60% of adult
80% of neonate
What proportion of body water is intracellular and extracellular fluid?
1/3 is extracellular
2/3 is intracellular
What is the major cation of extra and intracellular fluid?
Na+ is extracellular
K+ is intracellular
What % of ECF is blood plasma?
25%
What does dehydration trigger?
Decrease in blood volume then blood pressure activating the baroreceptor and activates RAAS
How can fluid be given enterally and parenterally?
Enteral- oral, tube
Parenteral- IV, Intra-osseous, intra-peritoneal, sub-cutaneous
When should oral rehydration therapy be used?
When the GI tract is functional with mild/moderate fluid volume disturbances
What is in oral fluids and what was added from 1st gen to 4th gen?
1st generation- enough sodium and equimolar glucose to correct dehydration
2nd generation- addition of bicarbonate which is lost in diarrhoea
3rd generation- high glucose- adresses nutritional demands
4th generation- contains glutamine- promoting villus repair and regeneration
How should an oral fluid be chosen?
Rehydration ability
Ability to correct acidosis
How much glucose
Nutritional ability and prevention of villus atrophy (glutamine)
What are crystalloids?
Salt solutions that freely cross capillary walls- quickly pass into extracellular fluid compartment
What are colloids?
Non-crystalline substances consisting of large molecules diluted in a crystalloid- capillary impermeable to these large molecules
Is 0.9% sodium chloride as colloid or crystalloid?
Crystalloid- has similar tonicity to plasma but is not physiological
What do physiological crystalloid contain?
HCO3- for buffer or acetate/gluconate/lactate which are metabolised by the liver with net production of HCO3-
Balanced with electrolytes of Na, Cl, K, Mg, Ca
What concentration of solution can crystalloids be?
Isotonic
Hypertonic
Hypotonic
Why are isotonic crystalloids poor plasma expanders?
Water freely moves by osmosis between blood plasma and interstitial fluid
Why are hypertonic crystalloids considered plasma expanders?
Their tonicity causes water to move from interstitial and intracellular to intravascular
e.g 7.2% NaCl solution
What is an example of a hypotonic crystalloid and what happens when administered into circulation?
5% dextrose in water
Lower concentration of electrolytes but isosmotic when administered- dextrose enters cells and is metabolised, therefore hypotonic as effectively water
What is used for maintenance solution and why?
4% glucose and 0.18% NaCl
ICF contains less Na and more K, can’t put high K into ECF
What is the result of isotonic, hypotonic and hypertonic crystalloids?
Isotonic- within 1 hour 75% of isotonic moves into ECF
Hypotonic- result in fluid accumulation in intracellular space
Hypertonic- draws fluid into the intravascular space
What is the effect of colloids?
Plasma volume expanders- increase colloidal osmotic pressure of the plasma and ‘pull’ water from the interstitial space
When are colloids used?
When it is difficult to administer sufficient volume of fluids rapidly enough to resuscitate a patient
When decreases oncotic pressure is suspected
What are used as colloids?
Natural- whole blood, plasma, albumen
Synthetic- starches, gelatins, dextrans
What are the potential adverse effects of colloids?
Anaphylactic reactions, coagulopathies, oedema
What are the 5 types of diuretics?
Osmotic Carbonic anhydrase inhibitors Loop Thiazides Potassium sparing
Why are diuretics classed as cardiovascular drugs?
Used to reduce sodium and water retention (oedema) and are therefore usually classified as cardiovascular
What is an example of a osmotic diuretic and what are their mechanisms of action?
Mannitol
MOA- filtered but not reabsorbed so excreted unchanged by the kidney and maintain osmotic pressure within filtrate
Mainly effects permeable parts of nephron
Increased filtrate in PCT also decreases Na+ reabsorption
How are osmotic diuretics administered, what are they used for and their adverse effects?
Admin- IV (fast acting)
Use- forced diuresis- poisoning, oliguric renal failure to stimulate urine output, cerebral oedema and glaucoma
Adverse effects- initial increase in ECF so may worsen pulmonary oedema or CHF
What is the mechanism of action of carbonic anhydrase inhibitors?
Distributed to tissues with high carbonic anhydrase activity (eye, kidney, RBCs)
Reversible inhibit CA enzyme leading to less H+ production and reduced Na/H exchange
Bicarbonate reabsorption from PCT is decreases and excretion increases
Results in diuresis and alkaline urine, Cl is therefore maintained for balance
How is carbonic anhydrase inhibitors administered, what are they used to treat and what are their adverse effects?
Oral administered- acetazolamide
Treat- glaucoma, metabolic alkalosis, weak diuretics
Adverse- hypercholraemic metabolic acidosis, liver disease means NH4 not lost in urine, PUPD for glaucoma
What is the MOA of loop diuretics?
Secreted into the PCT
Inhibit the NaKCl2 transported in LOH
Increase delivery of NA to the DCT
Increased excretion of K, H, Mg, Ca
Name an example of a loop diuretic, administration, use and adverse effects?
Feurosemide
Oral or parenteral administation
Treatment of oedema- udder, essential in management of CHF
Adverse- Excessive Na and water can cause dehydration and hypovolaemia, hypokalaemia
What is the mechanism of action of thiazides?
Secreted into PCT
Increase Na, Cl, Mg, K excretion
Decrease calcium excretion
What is an example of thiazides, how are they administered, what are they used to treat and what are there adverse effects?
Hydrochlorothiazide
Orally administered
Used for treatement of oedema and dissolution of Ca containing kidney stones
Adverse- dehydration and hypovolaemia, hypokalaemia
What is the mechanism of action of potassium sparing diuretics?
Act on principal cells of DCT and CD
Competitive inhibitors of aldosterone
Inhibition of Na reabsorption therefore NaKATPase activity
How are potassium sparing diuretics administered, used and what are there adverse effects?
Orally administered
Treatment of oedema, prevention of hypokalaemia
Adverse effects- hyperkalaemia, don’t use two different, don’t use with renal impairment
What are the most powerful and used diuretics?
Loop diuretics
