Hyponatremia
mild(130-135), mod(125-129), severe(<125
acute <48hr , chronic >48 hr or at home
-- SX: HA,D/N/V,AbdPain,tremor,cramps,fatigue,AMS,latharic,seizure,PO
-- Hx: CHF, cirrhosis, CKD, cancer, endocrine disorder,HLD,MM
-- PE: hypovolemic, euvolemic, hypervolemic,neuro))
-- DATA: base line Na, serum Osm: nlv (280-295), Hyper ≧295, Hypo <280 (true), urine osm : >100 or < 100, Urine Na <20 or >30–40, CBC,CMP,TSH
MEDS: ((Thiazides,SSRI,Antipsychotics,Carbamazepine))

DDX:
-- Normal Serum Osmolality (275–295) -> Pseudohyponatremia-> Hypertriglyceridemia or Paraproteinemia (MM, Waldenström)
-- Hypertonic (≥295)-> Translocational hyponatremia-> Hyperglycemia (MOST common), Mannitol, IVIG / contrast
-- Hypotonic (<275) → TRUE hyponatremia ->

  • Hypovolemic: GI losses, Diuretics: thiazides, Renal losses: adrenal insufficiency, salt wasting

  • Euvolemic: SIADH, Medications: SSRIs, carbamazepine, Hypothyroidism, Adrenal insufficiency, Polydipsia / low solute (beer potomania)

  • Hypervolemic: HF, Cirrhosis, nephrotic syndrom, ESRD
    -- Urine Osm <100-> ADH OFF, Primary polydipsia, Low solute intake (beer potomania)
    -- Urine Osm >100 -> ADH ON -> Now go to urine Na
    -- Urine Na <20 -> Kidney holding Na → hypovolemia (V/D/dehydration), also for (CHF, cirrhosis)
    -- Urine Na >30–40 -> SIADH (most common), Meds (SSRIs, thiazides), Adrenal insufficiency

ORDERS::serum osm, urine osm, urine Na, CBC,CMP,TSH, AM cortisol?, CXR(HF), CT chest (PNA,mass)?,

PLAN
--Rapid correction if symptomatic or acute or <120, 150 bolus 3% -> trend hourly -> x3 then gtt 25-100/hr until Increase 4-6 mEq/L within 1-2 hours (enough to stop symptoms)-> DC 3%-> trend Na q4hr -> Max 8 mEq increase daily until Na 130
-- recheck NA q1hr until Increase Na by 4–6 mEq then q4 hrs once stable q12 hrs and eventually daily
-- slow correction is used for asymptomatic, 8 mEq a day (if not autocorrecting)

  • hypovolemic- tx V/D, start 500 ns , recheck

  • Euvolemic (SIADH MC), Fluid restriction (≤1–1.5 L/day), Salt tabs (1 g PO TID) + loop diuretic (20 mg PO daily or BID), ↑ dietary solute (protein/salt), if Refractory urea (15–30 g PO daily or BID) and tolvaptan 15 mg PO dail – last resort

  • Hypervolemic (CHF, cirrhosis, nephrotic) Fluid restriction (≤1–1.5 L/day) + loop diuretic
    -- treat over correction first DC IVF then DDAVP (Desmopressin) 2-4 mcg IV, Can repeat q6–8 hrs, and IV D5W infusion (150–300 mL/hr) until Bring Na back into safe correction range

    -- can give DDAVP (Desmopressin) 2 mcg q6 if corrected too fast but still in range and check Na q4 or we can just monitor urine output and give same amount of D5W to keep it for not overcorrecting
    -- Hold Thiazides,SSRIs, carbamazepine, Loops (ok,helpful)
    -- strick I/O
    -- trend electrolytes nad replete
    -- treat underlying cause