Renal + diuretics

Question 1

What is the difference between sensible and insensible fluid losses and what are some normal ranges of insensible losses for healthy dogs and cats in a thermoneutral environment?

Answer 1

Sensible fluid loss: quantifiable
Insensible fluid loss: not easily quantifiable

Dibartola insensible losses: sedentary, thermoneutral conditions
Dog: 20-26 ml/kg/day
Cats: 12-29 ml/kg/day

Question 2

Recall the equation to calculate osmolality and what are the units?

Answer 2

Calculated plasma osmolality= 2Na+ (Urea/2.8) + (BG/18) in mg/dL
Dogs: 290-310 mOsm/kg
Cat: 290-330 mOsm/kg

Question 3

What is the difference between effective and ineffective osmoles and name two examples of each

Answer 3

Effective osmolality= 2Na+ (BG/18)
Effective: do not readily cross cell memb= Na, K, glucose
Ineffective: readily cross memb= urea, ethylen glycole, methanole, ethanol, acetyl salicylic acid

Question 4

What are stimuli for thirst?

Answer 4

increased osmolality, reduced blood volume/pressure (via increased Ang II)

Thirst threshold is higher (295 mOsm/kg) than the threshold for ADH secretion (285 mOsm/kg)

Question 5

What are the major controllers of NaCl and water excretion?

Answer 5

• Renal sympathetic nervous innervation
• Natriuretic peptides
• RAAS
• ADH

Question 6

What stimulate and what suppress ADH production?

Answer 6

ADH production is increased in response to elevated plasma osmolality
or hypovolemia/hypotension and, to a lesser extent, to nausea and increased angiotensin II concentration. ADH production is suppressed
by atrial natriuretic hormone and ethanol.

Question 7

What are the potential benefits of mannitol in AKI?

Answer 7

• prostaglandin-induced renal vasodilation
• decreased tendency of
  erythrocytes to aggregate
• decreased renal vascular congestion
• decreased hypoxic cellular edema
• protection of mitochondrial function
• decreased oxidative damage
• renoprotection when administered
  before a toxic or ischemic insult.

Question 8

What is the MOA of Acetazolamide?

Answer 8

It’s a carbonic anhydrase inhibitor. It inhibits mostly the type II (cytoplasmic) and IV (membrane) proximal tubular CAs, decreasing the reabsorption of
sodium bicarbonate.

Question 9

How does Furosemide reduce renal O2 consumption?

Answer 9

Loop diuretic administration
decreases renal tubular cell metabolic demand by
blocking the NKCC transporter and thus turning off the need for ATPase pump activity.