SM 199: IVF + Diuretics

Question 1

Types of IVF - how much does plasma volume change if you add one L of each IVF?

Answer 1

1. D5W: Sugar gets metabolized, water distributes to all compartments (1L = +1/12 L to plasma)
2. Normal Saline: 0.9% NaCl = 154mEq Na, adds all to ECF isoosmotically (1L = +1/4 L to plasma)
3. Half Normal Saline: 0.45% NaCl (50% NS, 50% Water), adds 50% to ECF and 50% distributes like water (1L = +1/8plasma + 1/24 = +1/6 plasma)
4. Lactated Ringers: more physiologic ion concentrations (130mEq Na) = (90% to ECF ~ 1/4 L to plasma for every 1L)

Question 2

What do you use for Maintenance fluid? Volume Resuscitation? Euvolemic and Hyperosmotic? Hypovolemic and Hyperosmotic?

Answer 2

Maintenance: Estimate amount from insensible losses - D5W good choice

Volume Resusc: if deplete - needs Na (NS or lactated ringers good), rate depends on clinical scenarios

Euvolemic + Hyperosmotic: give IV D5W (water)

Hypovolemia + Hyperosmotic: replace volume FIRST (Normal Saline)

Question 3

PT diuretics (name, how, side effects, use)

Answer 3

Acetazolamide
Inhibits CA in PT - decreases bicarb reabsorption and H secretion = decreases Na reabsorption (less Na/bicarb cotransport activity, less Na/H exchange)
SE: non-gap metabolic acidosis (USEDCARS)
Use: weak diuretic b/c rest of kidney can compensate; good for metabolic alkalosis when volume overloaded

Question 4

Loop Diuretics (Name, Fx, SE, Use)

Answer 4

Furosemide (Lasix), Torsemide, Bumetanide
Inhibits NKCC2 in TAL = also decreases paracellular reabsorption of Na, Ca, Mg due to decreased lumenal positivity
SE: fluid/electrolyte abnormalities (HypoK, hypoCa, hypoMg), volume depletion, ototoxicity
Use: rapid diuresis in fluid overload, HTN in CKD

Question 5

DCT Diuretics (Name, Fx, SE, Use)

Answer 5

Thiazides
Inhibit NCCT in DCT = increases Ca reabsorption through increasing Na/Ca Exchanger activity
SE: Fluid/Electrolyte imbalance (hypoK, hypoNa, HYPER-Ca)
Use: 1st line HTN tx (lower CV morbidity/mortality in HTN)

Question 6

K Sparing Diuretics (Location, Name, Fx, SE, Use)

Answer 6

Late DT/CD
Triamterene/Amiloride: ENaC blockers in Principal Cells = less K secretion, less Na Reabsorption
SE: HyperK, N/V
Eplerenone/Spironolactone: block Aldo-R in Principal Cells
SE: HyperK, gynecomastia (Spiro only)
Use: adjunctive tx to avoid hypo-K