In order to maintain our health, the balance of fluids and electrolytes must remain constant in the intracellular and extracellular spaces. Fluid replacement is vital for homeostasis.
Types of Fluid Solutions
Intravenous fluid replacement solutions fall into two broad categories
- Crystalloids (isotonic, hypotonic, hypertonic)
- These solutions flow easily from in the bloodstream to cells and tissues.
- Colloids (always hypertonic)
- Given when patient blood volumes do not improve with crystalloids and the patient needs a volume expander
- Examples: albumin, plasma protein fraction, and whole human blood
What does isotonic mean?
- Iso = same/equal and Tonic = concentration of a solution
Isotonic solutions have equal concentration of dissolved particles inside the intracellular fluid (ICF) and extracellular fluid (ECF). Osmotic pressure is the same so cells don’t shrink or swell with fluid movement.
Types of Isotonic Solutions
- 9% Normal Saline
- NaCl: mixture of salt and water
- Contains the electrolytes sodium and chloride
- Lactated Ringers
- Contains the electrolyte sodium, potassium, calcium, and chloride
- Contains Lactate which is converted to sodium bicarbonate by the liver
- 5% Dextrose in Water (D5W) WHILE INSIDE THE BIG
- Dextrose metabolizes quickly. The body metabolizes the glucose molecules and acts like a hypotonic solution leaving water behind. Large amounts of this solution can lead to hyperglycemia.
Isotonic Solutions are administered to increase Extracellular Fluid Volume due to dehydration, blood loss, and surgery.
What does hypotonic mean?
- Hypo = low/under and Tonic = concentration of a solution
Hypotonic solutions have fewer dissolved particles (such as electrolytes) than found inside the cell. Hypotonic solutions are given cautiously because fluid moves from the extracellular space into the cells causing swelling.
When you think of hypotonic solutions, think of a hippo. Hypo = Hippo. Hippos are large and swollen. Just like hypotonic solutions, cells can swell and burst.
Types of Hypotonic Solutions
- 45% Normal Saline (1/2 NS)
- 225% Normal Saline (1/4 NS)
- 33% Normal Saline (1/3 NS)
Hypotonic solutions are administered when cells are dehydrated and fluids are needed for intracellular spaces.
- Diabetic Ketoacidosis
- Hyperosmolar hyperglycemic state
Contraindications for Hypotonic Solutions
- Cardiovascular collapse from vascular fluid depletion. Fluid shifting from extracellular space into intracellular space causing cells to burst.
- Increased Intracranial Pressure (ICP) from fluid shifting in the brain
- Change in level of consciousness, motor or sensory deficits, and changes in the size/shape/response to light of pupils
- Liver disease, burn, or trauma patients
- Patients already suffer from abnormal fluid shifts into the interstitial space or the body cavities (hypovolemic)
What does hypertonic mean?
- Hyper = too much/excessive and tonic = concentration of a solution
Hypertonic solutions have too many dissolved particles than what is found inside the cell. Hypertonic solution draws fluids out of the intracellular space causing the cell to shrink and the extracellular space to expand.
When you think of hypertonic solutions, think of a hyperactive person. When a person is hyperactive, they tend to be more physical active and lean. The cells when exposed to hypertonic solution tend to shrink in its presence. The hypertonic solution is the physical activity while the cells shrink from the excess solution.
Types of Hypertonic Solutions
- 3% Normal Saline
- 5% Normal Saline
- 10% Dextrose in Water (D10W)
- 5% Dextrose in 0.9% Normal Saline
- 5% Dextrose in 0.45% Normal Saline
- 5% Dextrose in Lactated Ringers
Hypertonic Solutions are administered for treatment of heat related disorders, hypotonic dehydration, and fresh water drowning.
Contraindications for Hypertonic Solutions
- Cardiac and renal disease patients are unable to tolerate extra fluid
- Patients at risk for cellular dehydration (diabetic ketoacidosis) should not receive hypertonic solutions