Fluids and Fluid Composition: Intravenous Therapy Notes

• Intravenous therapy (IV therapy) involves administering substances directly into a patient’s vein for rapid onset of medication or fluid.

  • Fluids

  • Electrolytes

  • Blood products

  • Nutrition

  • Medications

• IV therapy is often used to restore fluids and/or resolve electrolyte imbalances more efficiently than the oral route.

• Administering fluids via the venous system provides a quick way to correct fluid imbalances.

• Nurses must understand the nature of the solution and its effects on the patient’s condition.

• In cases of deficient fluid volume, IV fluids are often used to:

  • Restore fluid to the intravascular compartment

  • Facilitate fluid movement between compartments through osmosis

Isotonic Solutions

• Isotonic solutions have a similar concentration of dissolved particles as blood.

  • Examples: 0.9% NaCl (normal saline) or Lactated Ringers/Hartmanns

• The fluid stays in the intravascular space, and osmosis does not cause fluid movement between cells.

• Isotonic solutions are used to treat fluid volume deficit (hypovolemia) to replace extracellular fluid lost due to:

  • Bleeding

  • Dehydration

  • Shock

  • Burns

  • Trauma

  • Gastrointestinal tract fluid loss (e.g., diarrhea).

• IV therapy with isotonic fluids will increase a patient’s blood pressure.

• Excessive isotonic fluid infusion can cause hypervolemia, requiring caution in patients with:

  • Hypertension

  • Heart failure

  • Renal disease

  • Due to the potential for fluid overload

Hypotonic Solutions

• Hypotonic solutions have a lower concentration of dissolved solutes than blood.

  • Examples: 0.45% NaCl or 5% dextrose in water (D5W).

  • D5W is isotonic in the bag but becomes hypotonic after the dextrose is rapidly metabolized by the body.

• When hypotonic IV solutions are infused, it results in a decreased concentration of dissolved solutes in the blood compared to the intracellular space.

• This imbalance causes osmotic movement of water from the intravascular compartment into the intracellular space.

• Hypotonic fluids are used to treat cellular dehydration, such as during diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemia.

• Excessive fluid movement out of the intravascular compartment can cause:

  • Cerebral edema

  • Worsening hypovolemia

  • Hypotension

• Patient status should be monitored carefully when hypotonic solutions are infused.

Hypertonic Solutions

• Hypertonic solutions have a higher concentration of dissolved particles than blood.

  • Example: 3% NaCl.

• When infused, hypertonic fluids cause an increased concentration of dissolved solutes in the intravascular space compared to the cells.

• This causes osmotic movement of water out of the cells and into the intravascular space to dilute the solutes in the blood.

• Hypertonic solutions move water out of the cells of the body and into the bloodstream.

• They are commonly used for patients with:

  • Cerebral edema

  • Severe hyponatremia

  • Some types of post-op patients

• Hypertonic solutions must be used very cautiously due to potentially rapid side effects of fluid overload resulting in pulmonary edema, so they are typically administered in intensive care units (ICU).

• When administering hypertonic fluids, monitor for:

  • Significantly elevated blood pressure

  • Difficulties breathing

  • Closely monitor the patient’s serum sodium level.