Urinary Pharmacology

Question 1

What % of body weight is water in adults and neonates?

Answer 1

60% of adult

80% of neonate

Question 2

What proportion of body water is intracellular and extracellular fluid?

Answer 2

1/3 is extracellular

2/3 is intracellular

Question 3

What is the major cation of extra and intracellular fluid?

Answer 3

Na+ is extracellular

K+ is intracellular

Question 4

What % of ECF is blood plasma?

Answer 4

25%

Question 5

What does dehydration trigger?

Answer 5

Decrease in blood volume then blood pressure activating the baroreceptor and activates RAAS

Question 6

How can fluid be given enterally and parenterally?

Answer 6

Enteral- oral, tube

Parenteral- IV, Intra-osseous, intra-peritoneal, sub-cutaneous

Question 7

When should oral rehydration therapy be used?

Answer 7

When the GI tract is functional with mild/moderate fluid volume disturbances

Question 8

What is in oral fluids and what was added from 1st gen to 4th gen?

Answer 8

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

Question 9

How should an oral fluid be chosen?

Answer 9

Rehydration ability
Ability to correct acidosis
How much glucose
Nutritional ability and prevention of villus atrophy (glutamine)

Question 10

What are crystalloids?

Answer 10

Salt solutions that freely cross capillary walls- quickly pass into extracellular fluid compartment

Question 11

What are colloids?

Answer 11

Non-crystalline substances consisting of large molecules diluted in a crystalloid- capillary impermeable to these large molecules

Question 12

Is 0.9% sodium chloride as colloid or crystalloid?

Answer 12

Crystalloid- has similar tonicity to plasma but is not physiological

Question 13

What do physiological crystalloid contain?

Answer 13

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

Question 14

What concentration of solution can crystalloids be?

Answer 14

Isotonic
Hypertonic
Hypotonic

Question 15

Why are isotonic crystalloids poor plasma expanders?

Answer 15

Water freely moves by osmosis between blood plasma and interstitial fluid

Question 16

Why are hypertonic crystalloids considered plasma expanders?

Answer 16

Their tonicity causes water to move from interstitial and intracellular to intravascular
e.g 7.2% NaCl solution

Question 17

What is an example of a hypotonic crystalloid and what happens when administered into circulation?

Answer 17

5% dextrose in water
Lower concentration of electrolytes but isosmotic when administered- dextrose enters cells and is metabolised, therefore hypotonic as effectively water

Question 18

What is used for maintenance solution and why?

Answer 18

4% glucose and 0.18% NaCl

ICF contains less Na and more K, can’t put high K into ECF

Question 19

What is the result of isotonic, hypotonic and hypertonic crystalloids?

Answer 19

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

Question 20

What is the effect of colloids?

Answer 20

Plasma volume expanders- increase colloidal osmotic pressure of the plasma and ‘pull’ water from the interstitial space

Question 21

When are colloids used?

Answer 21

When it is difficult to administer sufficient volume of fluids rapidly enough to resuscitate a patient
When decreases oncotic pressure is suspected

Question 22

What are used as colloids?

Answer 22

Natural- whole blood, plasma, albumen

Synthetic- starches, gelatins, dextrans

Question 23

What are the potential adverse effects of colloids?

Answer 23

Anaphylactic reactions, coagulopathies, oedema

Question 24

What are the 5 types of diuretics?

Answer 24

Osmotic 
Carbonic anhydrase inhibitors 
Loop 
Thiazides
Potassium sparing

Question 25

Why are diuretics classed as cardiovascular drugs?

Answer 25

Used to reduce sodium and water retention (oedema) and are therefore usually classified as cardiovascular

Question 26

What is an example of a osmotic diuretic and what are their mechanisms of action?

Answer 26

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

Question 27

How are osmotic diuretics administered, what are they used for and their adverse effects?

Answer 27

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

Question 28

What is the mechanism of action of carbonic anhydrase inhibitors?

Answer 28

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

Question 29

How is carbonic anhydrase inhibitors administered, what are they used to treat and what are their adverse effects?

Answer 29

Oral administered- acetazolamide Treat- glaucoma, metabolic alkalosis, weak diuretics Adverse- hypercholraemic metabolic acidosis, liver disease means NH4 not lost in urine, PUPD for glaucoma

Question 30

What is the MOA of loop diuretics?

Answer 30

Secreted into the PCT Inhibit the NaKCl2 transported in LOH Increase delivery of NA to the DCT Increased excretion of K, H, Mg, Ca

Question 31

Name an example of a loop diuretic, administration, use and adverse effects?

Answer 31

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

Question 32

What is the mechanism of action of thiazides?

Answer 32

Secreted into PCT Increase Na, Cl, Mg, K excretion Decrease calcium excretion

Question 33

What is an example of thiazides, how are they administered, what are they used to treat and what are there adverse effects?

Answer 33

Hydrochlorothiazide Orally administered Used for treatement of oedema and dissolution of Ca containing kidney stones Adverse- dehydration and hypovolaemia, hypokalaemia

Question 34

What is the mechanism of action of potassium sparing diuretics?

Answer 34

Act on principal cells of DCT and CD Competitive inhibitors of aldosterone Inhibition of Na reabsorption therefore NaKATPase activity

Question 35

How are potassium sparing diuretics administered, used and what are there adverse effects?

Answer 35

Orally administered Treatment of oedema, prevention of hypokalaemia Adverse effects- hyperkalaemia, don't use two different, don't use with renal impairment

Question 36

What are the most powerful and used diuretics?

Answer 36

Loop diuretics