multi class comparison
IV Solution Types: Isotonic vs Hypotonic vs Hypertonic — When and Why
Hanging the wrong IV tonicity can kill brain cells — literally. Hypotonic fluid in a head injury patient causes fatal cerebral edema. The NCLEX will hand you a clinical scenario and expect you to predict which direction fluid shifts based on solution tonicity alone.
Comparison
Side-by-side3 compared
Comparevs
Dimension
Isotonic
Hypotonic
Hypertonic
Tonicity (mOsm/L)
- 250–375 mOsm/L
- < 250 mOsm/L
- > 375 mOsm/L
Fluid shift
- No net shift; stays in vasculature
- Shifts INTO cells → cells swell
- Pulls fluid OUT of cells (cellular dehydration)
Examples
- 0.9% NS, LR, D5W (isotonic in bag)
- 0.45% NS, 0.225% NS
- 3% saline, D10W, D5NS, TPN
When to use
- Volume resuscitation, shock, blood loss
- Cellular dehydration; hypernatremia
- ↑ ICP / cerebral edema; severe hyponatremia
Avoid / caution
- Heart failure, renal failure (overload risk)
- ★Avoid in ↑ ICP / head injury — worsens edema
- ★Central line + pump; 3% NS ≤ 100 mL/hr
Monitoring
- I&O, lung sounds, daily weight
- Neuro checks q1–2h; serum Na⁺
- Serum Na⁺ q2–4h; correct ≤ 8–12 mEq/L/24h
Tonicity (mOsm/L)
Isotonic
- 250–375 mOsm/L
Hypotonic
- < 250 mOsm/L
Fluid shift
Isotonic
- No net shift; stays in vasculature
Hypotonic
- Shifts INTO cells → cells swell
Examples
Isotonic
- 0.9% NS, LR, D5W (isotonic in bag)
Hypotonic
- 0.45% NS, 0.225% NS
When to use
Isotonic
- Volume resuscitation, shock, blood loss
Hypotonic
- Cellular dehydration; hypernatremia
Avoid / caution
Isotonic
- Heart failure, renal failure (overload risk)
Hypotonic
- ★Avoid in ↑ ICP / head injury — worsens edema
Monitoring
Isotonic
- I&O, lung sounds, daily weight
Hypotonic
- Neuro checks q1–2h; serum Na⁺
★ marks the fact that sets a column apart.
Clinical Pearl
Isotonic stays, hypotonic swells cells, hypertonic shrinks cells — never give hypotonic to a swollen brain.
⚡ Speed Sort This Table
Swipe to sort 36 clinical items into the right bucket