Fluids & Electrolytes

Question 1

what is the percentage of body fluid compartments?

Answer 1

• ICF= 60%
• ECF= 40%; 1/4 is plasma, 3/4 interstitial

Question 2

how do compartments interact?

Answer 2

• semipermeable membranses separate compartment
• water moves freely between compartments
• effective osmolality is the same

Question 3

what changes ICF volume?

Answer 3

sodium

Question 4

how do you assess ICF?

Answer 4

osmolality= total osmoles in body/Total water in body

• changes in sodium concentration change ICF volume

Question 5

Major properties of ECF?

Answer 5

• all fluid outside the cell
• major solues include Na, Cl-, and HCO3
• changes in sodium content (not concentration) affect ecf

Question 6

How to asscess ECF?

Answer 6

Symptoms

• thirst
• lightheadedness
• palpitations

Signs

• orthostasis
• urine output
• dry mouth/moist membranes
• dry axilla
• low JVP/high JVP
• skin turgor/edema

Question 7

What is hypernatremia?

Answer 7

too little water

Question 8

what is hyponatremia?

Answer 8

Too much water

Question 9

how do you treat hyponatremia?

Answer 9

• hyponatremia- headache, nausea, confusion, falls, seizures
• excess water in cells includes brain cells which are confined in limited space
• Treatment with hypertonic solution to draw water out of cells- most commonly hypertonic saline

Question 10

major causes of hypernatremia

Answer 10

• comes in two varieties
• central DI: neurosurgery, trauma
• nephrogenic DI: lithium, hypokalemia, hypercalcemia

Question 11

what happens with too much sodium?

Answer 11

total body volume overloaded

• CKD/inability of kidney to excrete sodium intake
• CHF
• cirrhosis

Question 12

which diuretics block different parts of the nephron?

Answer 12

proximal tubule: no clincal diuretic
thick ascending limb: loop diuretics
distal tubule: thiazide diuretics
collecting duct: aldosterone antagonists, ENaC blockers

Question 13

how do you assess volume status ?

Answer 13

• thirst
• JVP
• skin turgor and presence/absence of edema (interstitial bed)
• low BP (arterial bed)
• Urine sodium and chloride for effective circulating volume

Question 14

treatment of volume contraction?

Answer 14

Volume contraction = loss of sodium
treatment= give back sodium

• usually given as isotonic fluids (lactated ringers or 0.9% normal saline)

Question 15

treatment of volume overload

Answer 15

volume overload= overload of sodium
treatment= remove sodium
removal of extra sodium is by; decrease intake of sodium, increase output of sodium

Question 16

Extracellular Fluid (ECF)

• Influences cell membrane potential
• regulated in narrow window (3.5-5mmol/L)
• GI reabsorption and ICF uptake
• renal excretion

Answer 16

potassium function

Question 17

• delayed repolarization of the ventricle
• ventricular instability
• arrhythmias

Answer 17

hypokalemia

Question 18

• sustained subthreshold depolarization
• delayed depolarization
• EKG changes
• arrhythmias
• death

Answer 18

Hyperkalemia

Question 19

causes of hyperkalemia?

Answer 19

transcelluar shift

• tissue breakdown
• acidosis
• insulin deficiency
• use of B-blockers

Increased intake

• would need to be > 5500mg to overwhelm a normal functioning kidney
• IV replacement can overwhelm balance

Question 20

Treatment of Hyperkalemia

Answer 20

1. restore excitability of cardiac myocyte: calcium gluconate or calcium chloride, antagonize potassium effect
2. shift potassium into the ICF: GIve insulin and glucose; if acidosis then give bicarb, B2 agonist (30-60min)
3. sodium polystyrene sulfonate: decrease uptake of potassium in the gut, given with sorbitol to increase bowel movement
4. enhance urine output-> IV fluids to increase tubular flow, diuretics –> dialysis (low potassium concentration in dialysate)