Academic Day Seminars

ADS – Fluids and Sodium balance Part 2

This ADS focussed predominantly on the effects of sodium disturbances. This was a bit challenging for me to wrap my head around, as it required me to incorporate the fluid disturbances taught last week and build on that with sodium disturbances. However, we were provided with cases to practice which I plan to do, and hope to become more proficient at coming up with the therapeutic recommendation for fluid replacement or restriction or diuresis therapies.

Below are the notes that I found most useful from the ADS that I intend on being mindful of when I interact with patients with fluid and electrolyte disturbances.

Hyponatremia Serum Na+ <135 mmol/L

  • S/Sx: Cerebral edema, nausea/malaise, headache, lethargy, non-cardiogenic pulmonary edema, seizure, coma, death
  • Usually see s/sx in 125 mmol/L… its clinically relevant depending to how fast they dropped, and what their baseline.
    • Speed of the change is really important
  • Reverse what you can reverse…deal with the underlying cause!

3 types:

– Hypovolemic hyponatremia

  • Causes: vomiting, diarrhea, diuretics, burns (severe) – b/c ur skin is ur ultimate rain coat (keeps water in), addison’s disease (deficiency in mineralocorticoid)
  • Tx:
    • Fluid replacement: D5NS or 0.9% NaCl
      • Do not use hypertonic (3%), b/c it will draw out water from the ICF?
    • Reverse reversible causes

– Euvolemic hyponatremia

  • Causes: SIADH, diuretic use, glucocorticoid deficiency, hypothyroidism, beer-drinker’s potomania, psychogenic polydipsia, primary polydipsia (kidney still works here)
  • SIADH: depending on when you catch it you (it fluctuates as you develop it until your body eventually re-equilibrate)
    • Tx: fluid restriction, identify and reverse any cause, sodium supplementation (+/- furosemide)… should suppress ADH secretion, tolvaptan (blocks vasopressin receptor), demeclocycline
      • Goal is to increase Na+ slowly…otherwise cell shrinks and can cause a physical demyelination
      • Na+ supplementation: 1-2 mmol/L/h for symptomatic
      • Na+ supplementation: ½ mmol/L/h for asymptomatic

– Hypervolemic hyponatremia

  • Causes: Excess water intake (dilution), CHF, Ascites, Acute kidney injury (renal failure), psychogenic polydipsia
  • Tx:
    • Diuresis: Furosemide (loop), ethocrinic acid, bumetamide, metozalone
      • Goal is to excrete more water than sodium
    • Fluid restriction: usually the DOC, 50-70% maintenance, works quicker than diuresis

Hypernatremia Serum Na+ >145mmol/L

  • Rupture of cerebral veins, lethargy, weakness, irritability, twitching, thirsty, decreased urine output
  • Seizure, coma, death
  • More tolerability of high Na+ … survivable, compared to hyponatremia (e.g. 190 is ok’ish compared to 105)

3 types:

– Hypovolemic hypernatremia

  • Causes: zero fluid intake, dehydration, diuretics (losing more water than sodium)
  • Tx:
    • D/C offending agents (e.g. diuretics)
    • Administer free water (D5W) or D51/2NS (don’t want to drop their sodium too quickly)
    • Drink water
    • Sodium restrict them (e.g. for antibiotics they can be attached to Na+)

– Euvolemic hypernatremia

  • Causes: Diabetes insipidus
    • Primary polydipsia
    • Central/neurogenic diabetes insipidus (deficiency in ADH/vasopressin) à increasing aquaporins in the collecting tubule (causes you to excrete more water)
    • Nephrogenic (kidneys have a resistance to ADH) à usually due to a genetic/family Hx
  • Tx:
    • DDVAP (desmopressin) à decreases urine output 1-2 hrs, effect lasts 6-24 hrs
    • Can use NSAIDs as a last line (probs b/c of vasoconstriction)

– Hypervolemic hypernatremia

  • Causes: hypertonic saline, hyperaldosteronism, renal failure (your kidneys don’t excrete sodium and water), tube feeds and TPN (concentrated electrolytes),
  •  Tx:
    • Fluid restrict
    • Sodium restrict
    • Diuretics (loop)
    • Spironolactone can be very useful for this.


Notes about hypertonic (3%) Na+ – has ~514mmol of Na/L: if you put 1 L of 3% NaCl (e.g. in a 45kg person) you will increase the sodium by 20.5mmol/L… this is huge and can cause mortality! We usually aim for 0.5-2 mmol/L



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