Acute kidney injury drugs

Question 1

Frusemide: mode of action

Answer 1

Loop diuretic; blocked the sodium-chloride cotransport system so inhibits tubular reabsorption of sodium and chloride in the proximal and distal tubules as well as the thick ascending loop of henle.
Net action is excretion of water, sodium, chloride, magnesium and calcium.

Question 2

Frusemide; dose rates for bolus doses and CRI

Answer 2

2-8mg/kg bolus. Onset of action is about 30 minutes.

CRI 0.5-1mg/kg/hr. 0.66mg/kg/hr is a commonly used dose. CRI causes better diureis with lower cumulative doses.

Question 3

Frusemide rationale for action

Answer 3

Does not increase GFR or renal blood flow, but in patients where they increase urine output they allow more fluids and medications to be used.
Increases tubular flow rates, reduces vascular resistance

Question 4

Mannitol; mode of action and proposed benefits

Answer 4

Osmotic diuretic

• increase renal blood flow
• decrease cellular swelling
• disperse tubular debris
• scavenge free radicals

Question 5

Mannitol: risk of harm

Answer 5

Overhydrated or underhydrated patients;
Listed to cause osmotic tubular injury - which may be related to acute tubular necrosis.
If there is no GFR it cannot be excreted and is poorly metabolised; remains causing osmotic effects in the body.

Question 6

Mannitol doses

Answer 6

0.5-1.0g/kg, or CRI 60-120mg/kg/min.

Question 7

Diltiazem; Mode of action

Answer 7

Calcium channel blocker. decreases renal vasoconstriction, and decreases calcium cytotoxicity.

Question 8

Fendaldopam: mode of action

Answer 8

Selective dopamine-1 receptor agonist (in cats). Selectively increases cortical and medullary blood flow, sodium excretion and urine output.

Question 9

Discuss a treatment protocol for sodium bicarbonate in severe acidosis

Answer 9

0.3 x body weight x base deficit.

Dilute 1:3 and give 1/3 over 15 min, next 1/3 over 2-6 hours.

Question 10

When should bicarbonate be considered.

Answer 10

Should only be considered in pH <7.2, strongly considered in <7.1.

Question 11

What are contraindications to the use of bicarbonate

Answer 11

Hypernatremia, hypoventilation.

Question 12

Discuss treatment aims in hypertensive animals with AKI

Answer 12

Treat with a systolic BP over 180.

Avoid a precipitous decline (ie >25%) as hypotension is also harmful.

Question 13

List antihypertensive drugs in AKI

Answer 13

amlopidipine
nifedipine
hydralazine
Avoid ACE-i.

Question 14

List MoA for amlopidipe

Answer 14

angioselective calcium channel - inhibits the contraction of cardiac muscle and vascular smooth muscle cells.

Question 15

List MoA for nifedipine.

Answer 15

calcium channel blocker - prevents the influx of calcium ions through voltage gated channels.

Question 16

List MoA for hydralazine

Answer 16

peripheral vasodilator. unclear, probably multiple actions.

Question 17

Describe the use of phosphate binders in acute kidney injury.

Answer 17

IV fluids will initially lower phosphate. Phosphate binders cause inappetence and should be avoided until the patient is eating.

Question 18

What is the goal of fluid therapy in acute kidney injury?

Answer 18

To achieve and maintain hydration without creating overhydration

Question 19

What is the replacement rate for insensible losses?

Answer 19

22ml/kg/day.

5% glucose in water is the treatment of choice for insensible losses