IPC FEN Week 1

Body Water Physiology

• Total Body Water = 60% of total body weight

  • 60% ICF

  • 40% ECF

• Intravascular a mix of both, 5L

  • RBC & Plasma

Normal body Tonicity

ICF → 280 mOsm/L K+

ECF → 280 mOsm/L Na+

Serum Osmolality Calculation

mOsm/kg = 2Na + Glucose/18 + BUN/2.8

ADH Pathway

• Brain → hypothalamus detects tonicity

  • Can release thirst signals or pituitary releases ADH

    • ADH binds to vasopressin-2 receptors in collecting duct of nephrons → inserts aquaporin-2 channels

      • collecting tubes reabsorb free water

Hypovolemia causes

• Poor PO intake

• Infection / fever

• Trauma, burn

• Blood loss (hemorrhage)

Hypovolemia clinical presentation

• Hypotension

• Tachycardia

• Dry mucus membranes

• Poor Turgor

• Slow capillary refill

• cool extremities

• Orthostasis

Isotonic Fluid Loss

• Blood, Diarrhea, vomiting, loop diuretic

Hypotonic Fluid Loss

• Sweating, insensible, urine, loop diuretic

Obligate Water Loss

800 mL insensible + 100 mL Sweat + 200 mL feces + 500 mL Urine = 1600 mL/day

Kidneys Role in Hypovolemia

• Decrease urine volume, decrease urine Na, increase urine concentration

• FeNa

  • Hypovolemia <1% FeNa

  • Normal 1-2%

• Loop Diuretic

  • FeUrea <35%

Hypovolemia → Hypotonic Loss

• Free water will shift from the ICF → ECF to maintain tonicity

Hypovolemia → Isotonic Loss

• Free water will not shift

Edema & Hydrostatic / Oncotic Pressures

• Hydrostatic is the pressure of the water on a vessel pushing it out

• Oncotic is the pulling force from large proteins (albumin) of water back into the blood vessels

• In an edematous state, hydrostatic pressure would be high and/or oncotic pressure would be low

Kidneys Role in Hypervolemia

• Increase urine volume, increase urine NA, decrease urine concentration

Hypervolemia Clinical Presentations

• Peripheral / Pulmonary Edema

• Hypertension

• Jugular Venous Distension

• Weight gain

• Shortness of breath

Kidney Stone Types

• Calcium (80%)

  • Oxalate (acidic), phosphate (alkaline)

• Uric Acid (10%)

  • Gout, hypovolemia, hyperuricosuria

• Struvite (5%)

  • Bacterial UTI, Urea breakdown

Kidney Stone Presentation

• Flank pain

• hematuria

• painful difficult urination

Drug Induced Kidney Stones

• Allopurinol

• Acyclovir

• Sulfamethoxazole

• Loop Diuretics

• Topiramate

Kidney Stone Risk Factors

• Dehydration

• High Protein diet

• High sodium diet

• Obesity

• Hypercalcemia

D5W

• 5g / dL Dextrose

• Hypotonic

• 1000mL of free water

• 60% ICF, 40% ECF

0.45 NaCl

• 77 mEq/L Na+ & Cl-

• Hypotonic

• 500mL of free water

• 37% ICF, 77% ECF

0.9% NaCl

• 154 mEq/L Na+ & Cl-

• Isotonic

• 0 mL of free water

• 100% ECF

3% NaCl

• 513 mEq/L Na+ & Cl-

• Hypertonic

• -2331 mL of free water

• 100% ECF

Lactated Ringers

• 130 Na+, 105 Cl-, lactate, K, Ca

• Isotonic

• 97% ECF, 3% ICF

• 0 mL free water

5% Albumin

• Isotonic

• 100% Intravascular

• 0% free water

What are Crystalloids & Colloids

• Crystalloids:

  • Electrolytes:

    • NS, ½ NS, 3% NS

  • Balanced:

    • Lactated Ringer, Plasma-lyte

    • mimic plasma electrolytes, closer to neutral pH, safer

• Colloid

  • 5% Albumin

Maintenance Fluid Calculation

• 30-35mL/kg per day

or

• 1500mL + 20mL/kg per kg >20kg

Typically around 100-125 mL per hour

1L of each solution will increase intravascular volume by:

• D5W = 100mL

• ½ NS = 175mL

• NS & LR = 250mL

• Albumin 5% = 1000mL

• 3% = 832mL

Complications with Fluids

• Volume overload

• Saline → hyperchloremic metabolic acidosis

• LR → alkalosis

• Electrolyte abnormalities

  • hyponatremia with D5W

  • hypernatremia with NS

  • hyperglycemia with diabetics

Treating Sepsis

At least 30 mL/kg of IV crystalloid fluid should be given within the first 3 hours of resuscitation

• NS, LR

KIDGO-Acute Kidney Injury

Volume expansion / flushing with crystalloids; isotonic sodium or bicarb solutions

• Not colloids, not balanced crystalloids

Common Incompatible Fluids

• Ceftriaxone + Calcium = precipitation

• Sodium Bicarb + Calcium = precipitation

• Sodium Bicarb + epinephrine = inactivation

• Diazepam + NaCl = precipitation

Loop Diuretic MOA

• Inhibits NKCC2 Channel

• In Thick ascending limb of loop of henle

• blocks 20-25% of filtered Na

Loop Diuretic ADR

• Hypokalemia, hypomagnesemia, hypochloremia

• contraction alkalosis

• Nephrolithiasis

• Hyperuricemia (gout)

• Rash (true sulfa allergy)

• Cochlear ototoxicity

Loop Diuretic Dosing

• IV

  • Furosemide → 20mg

  • Bumetanide → 1mg

  • Torsemide → 20mg

• PO

  • Furosemide → 40mg

  • Bumetanide → 1mg

  • Torsemide → 20mg

• Furosemide → most common

• Bumetanide → most potent

• Torsemide → longest acting

• Ethacrynic Acid → No sulfa moiety

Diuretic naive vs. experienced dosing

• Naive

  • 40mg IV Furosemide or any equivalent

  • If urine output still >500mL within 6 hours, double dose

  • Once goal achieved, lower dose to Q12hrs

• Experienced

  • Give double home dose as IV, then repeat as above

Thiazide MOA

• Inhibits NaCl symporter

• Distal convoluted tubule

• inhibits 5% of filtered Na

• Reduces blood pressure

Thiazide ADR

• Hyponatremia, hyperuricemia (gout), hypokalemia

• Hypercalcemia

MRA MOA & ADRs

• Competitive antagonist of MRA of principal cells of collecting duct

  • decrease Na absorption through ENaC and Na/K ATPase

• K+ and H+ does not get secreted → hyperkalemia & acidosis

Mineralocorticoid Receptor Antagonist’s

• Spironolactone & Eplerenone

  • Endocrine ADR’s

• Finerenone

  • Non-steroidal

Potassium Sparing Diuretic

• Amiloride, Triamterene

• Often used with thiazide diuretics to offset hypokalemia

• In collecting duct

Carbonic Anhydrase Inhibitors

• Acetazolamide

• Proximal convoluted tubule

• Often given with thiazides to offset hypokalemia

  • Can enhance loop diuretics in HF

Diuretic Resistance

• Decreased affect of loop diuretics after months-years of use

• Increase in DCT transporters

• Treatment → use of a thiazide, usually Metolazone

BUN / SCr Ratio

• Normal is 10:1 or 20:1

• Elevates is >20:1

  • Causes: dehydration, HF exacerbation, sepsis, pre-renal AKI

Urine Output

• >3000mL → Polyuria

• 3000-1000mL → Normal

• <400mL → oliguria

• <50mL → anuria

Proteinuria

• Marker of glomerular damage

• Dipstick method

  • 10-20 mg/dL = trace

  • 30 = +1

  • 100 = +2

  • 300 = +3

  • >1000 = +4

Albumin to Creatinine Ratio (ACR)

• Normal (A1) → <30 mg/day

• Microalbuminuria (A2) → 30-300 mg/day

• Macroalbuminuria (A3) → >300 mg/day

Cockcroft-Gault Equation

• (140 - age) x ABW / 72 x SCr

  • x 0.85 if female

• IBW

  • Male = 50 + 2.3 (inches >60)

  • Female = 45.5 + 2.3 (inches >60)

Creatinine vs. Cystatin C non-GFR determinants

• Creatinine

  • age, muscle, nutrition, amputation

• Cystatin C

  • obesity, cancer, RA, inflammation, steroids, smoking

KDIGO Heatmap

• G1 → >90

• G2 → 89-60

• G3A → 59-45

• G3B → 44 - 30

• G4 → 29-15

• G5 → <15