IV Therapy
Pharmacology Cheat Sheet

IV Fluids Crash Course: Isotonic, Hypotonic & Hypertonic

Understand osmolarity shifts, clinical indications, and life-saving nursing watch-outs at a glance.

Serum Osmolality 275 – 295 mOsm/kg
Key Rule Water Follows Solutes
Focus Fluid Shift Safety
Foundation
Physiologic Principle

How Fluids Move in the Body

Intracellular (ICF) ~2/3 Total Body Water
Extracellular (ECF) ~1/3 Total Body Water
Osmotic Memory Shortcut

• Isotonic: "Stay where I put it" (Vascular expansion).
• Hypotonic: "Go Out of the vessel" (Hydrates cells).
• Hypertonic: "Enter the vessel" (Draws fluid from cells).

Type 01
Volume Resuscitation

Isotonic Solutions: 0.9% NS & LR

Osmolality ~250 – 375 mOsm/L
Primary Types 0.9% NaCl, Lactated Ringer's
Clinical Applications

• 0.9% Normal Saline: ONLY fluid compatible with PRBC blood transfusions.
• Lactated Ringer's: Contains sodium, potassium, calcium, and lactate buffer. Ideal for trauma, surgical losses, and severe burns.

Type 02
Cellular Hydration

Hypotonic Solutions: 0.45% NS & 0.33% NS

Osmolality < 250 mOsm/L
Primary Indications DKA, HHS, Cellular Dehydration
Critical Contraindication

NEVER administer to patients with increased ICP (head trauma, stroke) or severe burn injuries! Fluid enters brain tissue causing life-threatening cerebral edema.

Type 03
Volume Expansion

Hypertonic Solutions: 3% NaCl & D10W

Osmolality > 375 mOsm/L
Common Types 3% Saline, 5% Saline, D10W, D5 0.9%
ICU Alert • Fluid Overload Risk

Draws water rapidly from cells into the intravascular space. Indicated for severe symptomatic hyponatremia. Monitor continuously for pulmonary edema, crackles, and bounding pulse.

Safety Protocol
Bedside Monitoring

4 Golden IV Nursing Safety Rules

1. Lung Auscultation Listen for bibasilar crackles
2. Site Inspection Assess phlebitis / infiltration
3. Strict I&O Track 1 kg = ~1,000 mL fluid
4. Pump Verification Double-check rate & VTBI
Clinical Practice
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