Electrolytes + Acid Base


Hyponatremia osmolarity 275 – 295 serum osmolarity 2 * Na, glucose / 18 BUN /2.8

High glucose, isotonic – pseudohyponatremia 275 – 295 proteins / lipids, low 

Check volume status BP, mucosa 

Hypovolemic dry mucosa

Hypervolemic – CHF, Cirrhosis, nephrotic syndrome 2/2 systemic edema

Normovolemic – SIADH, primary polydipsia

Hypovolemic – diarrhea vomiting / diuretics

ADH urine osmolarity

Urine Sodium cut off 20 < 20 or above indirect way of checking RAAS


Fena < 1 prerenal

Hypovolemic hypotonic hyponatremia – diuretics, 

Euvolemic SIADH sodium above 20, hyperosmolar or primary poldipsia

Urine Na > 20 think CHF, nephrotic, Cirrhosis

Urine Na < 20 think more ESRD, chronic kidney disease

Hypernatremia

Hypervolemic or euvolemic without symptoms – fluid restrict

Hypovolemic w/o symptoms – 0.9% NS

Hypovolemic w/ symptoms – hypertonic saline 3%, below 120 hypertonic saline lethargy, coma


Hypernatremia – euvolemic, hypovolemic

High to low the brain will blow – cerebral edema

Hypervolemic, euvolemic – free water

Hypovolemic with symptoms NS, most 

Hypovolemic – 1/2NS more gradual

Calcium

Blood transfusions – cause hypocalcemia citrate binds

Hypercalcemia – IV fluids

Potassium

Hyperkalemia – Calcium gluconate stabilizes cardiac membranes prevent arrhythmias, insulin pushes potassium into cells with glucose, Kaexelate binds potassium improves excretion


Magnesium

Hypermagnesemia – loss of dtr, IV calcium gluconate

PTH

PTH – bones increased calcium and phosphate, kidneys increase calcium and phosphate secretion, calidiol to calcitriol increase calcium and phosphate uptake

High PTH high calcium low phosphate treat with parathyroidectomy
High calcium and vitamin D3 shuts down
Kidney failure no calcidiol to calcitriol main function of kidney
Can’t absorb calcium and phosphate
Kidney tubules don’t work, can’t absorb calcium, can’t dump phosphate. Phosphate locked up in body. Bone increase phosphate and calcium, 
kidney failure results in elevated PTH, low calcium, and high phosphate
hyperparathyroid – high PTH, high Ca, low phosphate
Primary hypoparathyroid – low PTH, low ca, high phos
CKD: High pth, low ca, high phos
Vitamin D deficiency high PTH, low Calcium, low phosphorous (celiac, cystic fibrosis), pancreatic cancer
PTHRP like PTH increase Ca, decrease phosphate, low PTH
Mechanical ventilation: PCO2 Vt and RR
PaO2 PEEP and FiO2
PH 7.35 – 7.45
Bicarb 22 - 28

Acid Base


PCO2 35-45, <35 respiratory alkalosis > 45 respiratory acidosis
HCO3: 22-28 < 22 metabolic acidosis 28+ metabolic alkalosis
AG: Na – (Cl – HCO3) > 12 AGMA
MUDPILES < 12 NAGMA – diarrhea, RTA
Metabolic alkalosis HCO3 > 28 pH > 7.45 UCl > 20 Renal problem < 20 GI problem  
NAGMA RTA verse Diarrhea UAG Na + K – (Chlroide) NeGUTive (GI), Positive Kidney


#Anion-Gap Metabolic acidosis 
Most likely ***. Ddx includes MUDPILES (methanol, uremia, DKA, propylene, Fe, isoniazid, lactic acidosis, ethanol, salicylates), acute or chronic kidney disease. 
-NaHCO3- if severe acidosis pH < 7.1 or pH < 7.2 in severe AKI (avoid in CHF)
-RRT if pH < 7.1 and not responsive to bicarb tx
-trend BMP daily

#Hyperchloremic Non-Gap Metabolic acidosis
Most likely ***. Ddx includes HARDUPS: Hyperalimentation (started TPN), acetazolamide, RTA (Type I = distal; Type II = proximal; Type IV = hypoaldosteronism), diarrhea, uretosigmoid fistula, pancreatic fistula, normal saline excess.
-Urine Osm (Na, K, Cl). Calculate urine anion gap (urine AG = urine Na + urine K – urine Cl). If + RTA, If - diarrhea (neg GUT ive)
-NaHCO3- if severe acidosis pH < 7.1 or pH < 7.2 in severe AKI (avoid in CHF)
-RRT if pH < 7.1 and not responsive to bicarb tx
-trend BMP daily



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