Lecture 10 - Fluids & Electrolytes Flashcards
how to calculate mEq
( Mass (mg) X valence) / (molecular weight)
mOsm/L of NaCl?
308 mOsm/L
Normal plasma osmolality?
~ 270-295 mOsm/L
Isotonic Solutions
270-300 mOsm/L
Hypotonic solutions
< 270 mOsm/L
Hypertonic solutions
> 300 mOsm/L
Why should significantly hypotonic fluids ( < 154 mOsm/L) not be admin directly to patients?
can cause cellular swelling and cell death
What makes solutions Iso, Hypo, Hypertonic?
Hypertonic = due to Electrolyte balances Hypotonic = due to have fraction of electrolyte of normal solution
Total Body Water Calculation
~ 50% for women (of total body weight)
~ 60% for men (of total body weight)
also ~73% of Lean body mass
Osmolar Gap Calculation
Measured Na+ mEq/L + {[(measured glucose - 100)/100] X 1.6}
Osmolar Gap seen when pts have which symptoms?
Severe Hyperglycemia Hyperlipidemia Azotemia/uremia Mannitol infusion Toxic alcohols
Causes of Osmolar Gap
high glucose or low sodium
Neonate fluid replacement calc (< 10kg)
100ml/Kg
Pediatric fluid replacement calc ( 10-20kg)
1000ml + 50ml/each kg between 10-20kg
Adolescent/Adult fluid replacement calc (> 20kg)
1500ml + 20ml/each kg > 20kg
Mild Dehydration Therapy
Replace over 8-24hrs
Provide additional 6-8oz per episode of diarrhea
ORT = Oral rehydration therapy
too much glucose can cause osmotic diarrhea
Optimal mix of fluid, electrolytes, carbs
Examples of Oral Rehydration solutions
WHO/UNICEF ORT Ceralyte 50,70,90 (# = amount of sodium) Infalyte Naturalyte Pedialyte Liquid and Freezer pops Rehydrate
Moderate/Severe Dehydration Therapy
Req hospitalization and IV rehydration
Txm must include water deficit + maintenance fluid needs + ongoing abnormal/excessive losses
** Fluids will distribute into body fluid compartments based on osmolarity of the solution and the effective free water content**
Common causes of volume overload
HF
Liver cirrhosis
Nephrotic Syndrome
Acidemia
pH < 7.35 = higher amounts of bicarb, or lower lvls of C02
Alkalosis
pH > 7.45
Pulmonary & Metabolic Regulatory Mechanism
respiratory = if issue is in lungs Metabolic = if issue is in kidneys
General Na reference range?
135-146mEq/L
symptoms tend not develop until lvls are above/below by 10mEq/L
Hyponatremia
Na lvl < 135
Severe < 125
Where do Osmotic diuretics work?
PCT
Where do Loop diuretics work?
Loop of Henle
Where do ADH & Vasopressin antagonists work?
Collecting duct
Where do Thiazide diuretics work?
DCT
Examples of Osmotic diuretics
Mannitol, urea, glycerol
How do osmotic diuretics wok?
create osmotic gradient and inc water excretion
What are osmotic diuretics used for clinically?
reduce increased intracranial pressure, intraocular pressure, and promote removal of toxins
Example of Carbonic Anhydrase Inhibitor
Acetazolamide, acts mainly in proximal tubule
IV to PO furosemide?
20mg IV = 40 MG PO
Diuretic with risk of hyponatremia?
Thiazide diuretics
Spironolactone and eplerenone are antagonists for what?
Aldosterone
They’re potassium sparring diuretics
Generally weak activity
Conivaptan & Tolvaptan are….
Vasopressin Antagonists (ADH)
increase serum osmolality & Na but don’t alter Na excretion
Conivaptan receptor antagonist at….
V1a and V2
Tolvaptan receptor antagonist at…
Selective V2
preferred
Osmolarity of D5W only
252 = hypotonic
Osmolarity 0.9% NaCl
308 = isotonic
Osmolarity 0.45% NaCl
154 = hypotonic
Osmolarity D5W + 0.225% NaCl
329 = hypertonic
Osmolarity D5W + 0.45% NaCL
406 = hypertonic
Lactated Ringer
273 = Isotonic
Plasma-Lyte
294 = isotonic
causes of Hyponatremia
Loss of sodium, gain of water or both
Mild Hypoatremia
126-135
typically asymptomatic/non-specific
HA, Disorientation, mild confusion, blurry vison, N/V
Moderate Hyponatremia
120-125
range from mild-profound confusion, no concern of seizures
Severe hyponatremia
< 120
may include stupor/coma, severe neurologic changes
Hypovolemic Hyponatremia
Excessive electrolyte-rich solute loss relative to TBW loss
Euvolemic Hyponatremia
slight decrease/normal total body Na and normal/slightly elevated TBW (no fluid overload)
common due to SIADH
Hypervolemic Hyponatremia
excessive overload leads to dilution effect in the serum
endurance athletes
Correction rates for Hyponatremia
as low was 1-2 mEq/L per hour
Typical Max = 6 mEq/L in 6hrs, 12 mEq/L in 24hrs, 18 mEq/L in 48hrs
avoid rapid over correction, you’d avoid sodium based products if you do over correct
Hypovolemic Hyponatremia treatment
Mild/moderate = normal saline + lactated ringer
More severe = 3% hypertonic saline
concern with rapidly correcting patients sodium?
Osmotic Demylenation
Euvolemic or Hypervolemic Hyponatremia treatment
Mild/moderate = volume restriction
Severe = bolus hypertonic saline prioritized over volume restriction 1st 12-24hrs
If fluid restriction falls in Euvolemic/Hypervolemic then what….
Try loop diuretics, IV 20-40 Furosemide q6/12hrs
Vasopressin receptor antagonist
Only free water available in hospital?
Dextrose
Hypernatremia treatment
minimize sodium taking in
give them volume (“Free Water” = electrolyte free) = Dextrose infusion
want it to be sodium free
Hypovolemia Hypernatremia treatment
Isotonic solution over 2-4 days at a low rate
Hypervolemia Hypernatremia treatment
Loop diuresis elim excess fluid and sodium
hypochloremia lvls
< 97 mEq/L
hypochloremia treatment
chloride containing solution
Hyperchloremia lvls
> 108 mEq/L
Hyperchloremia treatments
D/c or reduce causative agent
little treatment options
sodiumbicarb can be given as buffer
Potassium range
3.5-5 mEq/L
Hypokalemia lvls
< 3.4 mEq/L
Give potassium, but less worrisome than Hyperkalemia
Hyperkalemia lvls
> 5 mEq/L
can cause arrhythmia when > 6
Hyperkalemia treatment
1st give Calcium gluconate 1-2g IV push if they are symptomatic or have ECG changes (stabilizes cardiac cell membranes)
Then reduce/remove the potassium
Acute Hyperkalemia Treatment
Reduce: Insulin, Sodium Bicarb, Albuterol
To remove: Kayexalate ( sodium polystyrene sulfonate)
Hemodialysis = last stop
Chronic Hyperkalemia Treatment
Patiromer (Veltassa) or sodium zirconium cyclosilicate (Lokelma)
Phosphorus range
2.7-4.5 mg/dL
Hypophosphatemia
< 2.6 mg/dL
Hyperphosphatemia
> 4.5 mg/dL
commonly seen with CKD
Hypophosphatemia treatment
Mild (2-2.5) or moderate (1-1.9) = oral supplements if functional GI
Severe (< 1) = IV
Hyperphosphatemia Treatment
Treat underlying conditions
give drugs that bind to phosphate and remove it
** tied to calcium, so if have hypercalcemia then avoid calcium binder **
Calcium ranges
8.5 - 10.2 mg/dL
Hypocalcemia
< 8.5 mg/dL
Hypocalcemia treament
Acute: Calcium glucoante > Calcium chloride
Chronic: 1-2g/elemental per day
Hypercalcemia
> 10.2 mg/dL
1st clinical thought = cancer
Hypercalcemia acute treatment
1st step = hydration
Severe: 200-300 ml/hr of NS for 2-6L
Bisphosphate & RANK therapy = store calcium back into bones
Hypercalcemia chronic treatment
Cincalcet
Frequent Bisphosphonates
Denosumab
Hypomagnesemia
< 1.5 or lower
Treatment: replace…the more severe the higher the dose
Oral = mild/moderate, IV = severe
Hypermagnesemia
can give Calcium chloride
