Intravenous fluids are additional fluids used in intravenous therapy to restore or maintain normal fluid volume and electrolyte balance in situations where oral route is not possible, or fluid volume needs to be restored immediately.

TYPES OF INTRAVENOUS FLUIDS

Intravenous fluids can be categorized into two main types namely, Crystalloids and Colloids.

CRYSTALLOIDS: these are solutions that contain small molecules that flow easily across semipermeable membranes, from the bloodstream into the cells and body tissues. Crystalloid solutions are distinguished by the relative tonicity (before infusion) in relation to plasma and are categorized as isotonic, hypotonic, or hypertonic.

Isotonic IV Fluids: Isotonic solutions have a concentration of dissolved particles like plasma, and an osmolality of 250 to 375 mOsm/L. These fluids remain within the extracellular compartment and are distributed between intravascular (blood vessels) and interstitial (tissue) spaces, increasing intravascular volume. They are used primarily to treat fluid volume deficit. Examples of isotonic iv fluids include: 0.9% NaCl (Normal Saline), Ringer’s Lactate (LR).

Hypotonic IV Fluids: Hypotonic solutions have a concentration of dissolved particles lower compared to plasma and an osmolality < 250 mOsm/L. Hypotonic fluids lower serum osmolality within the vascular space by causing fluid to shift out of the blood into the cells and tissue spaces. Typically used to treat conditions causing intracellular dehydration, such as diabetic ketoacidosis and hyperosmolar hyperglycemic states. Examples of hypotonic iv fluids include ½ (0.45%) Normal Saline (1/2 Ns)

Hypertonic IV Fluids: Hypertonic solutions have a concentration of dissolved particles higher than plasma and an osmolality > 375 mOsm/L. A higher solute concentration causes the osmotic pressure gradient to draw water out of cells, increasing extracellular volume. These fluids are often used as volume expanders and may be prescribed for hyponatremia (low sodium). They may also benefit patients with cerebral edema. Examples of hypertonic iv fluids include Dextrose 5% in 0.45% NaCl, Dextrose 50% in Water (D50W), Dextrose 5% in 0.9% NaCl (D5NS).

NORMAL SALINE (NS)

DESCRIPTION

• 0.9% NaCl in Water
• Crystalloid Solution
• Isotonic (308 mOsm)

USES

• Increases circulating plasma volume when red cells are adequate.
• Shock
• Fluid replacement in patients with diabetic ketoacidosis
• Hyponatremia
• Blood transfusions
• Resuscitation
• Metabolic alkalosis
• Hypercalcemia
• Replaces losses without altering fluid concentrations.

PRECAUTIONS

• Do not use in patients with heart failure, edema, or hypernatremia, because NS replaces extracellular fluid and can lead to fluid overload.

1/2 NORMAL SALINE (1/2 NS)

DESCRIPTION

• 0.45% NaCl in Water
• Crystalloid Solution
• Hypotonic (154 mOsm)

USES

• Water replacement
• Raises total fluid volume.
• DKA after initial normal saline solution and before dextrose infusion
• Hypertonic dehydration
• Sodium and chloride depletion
• Gastric fluid loss from nasogastric suctioning or vomiting.
• Useful for daily maintenance of body fluid but is of less value for replacement of NaCl deficit.
• Helpful for establishing renal function.

PRECAUTIONS

• Use cautiously; may cause cardiovascular collapse or increase in intracranial pressure.
• Don’t use in patients with liver disease, trauma, or burns

LACTATED RINGER’S (LR) OR RINGER’S LACTATE (RL)

DESCRIPTION

• Normal saline with electrolytes and buffer
• Isotonic (275 mOsm)

USES

• Replaces fluid and buffers pH.
• Hypovolemia due to thirdspace shifting.
• Dehydration
• Burns
• Lower GI tract fluid loss
• Acute blood loss

PRECAUTIONS

• Don’t use in liver disease because the patient can’t metabolize lactate; a functional liver converts it to bicarbonate; don’t give if patient’s pH > 7.5.
• Has potassium therefore don’t use to patients with renal failure as it can cause hyperkalemia.

D5W (5%DEXTROSE WATER) OR 5% DEXTROSE

DESCRIPTION

• Dextrose 5% in water Crystalloid solution
• Isotonic (in the bag)
• *Physiologically hypotonic (260 mOsm) (the dextrose is metabolized quickly so that only water remains – a hypotonic fluid).

USES

• Raises total fluid volume.
• Helpful in rehydrating and excretory purposes.
• Fluid loss and dehydration
• Hypernatremia
• Provides 170-200 calories/1,000cc for energy.

PRECAUTIONS

• Use in caution to patients with renal or cardiac disease, can cause fluid overload.

D5NS 

DESCRIPTION

• Dextrose 5% in 0.9% saline
• Hypertonic (560 mOsm)

USES

• Hypotonic dehydration
• Replaces fluid sodium, chloride, and calories.
• Temporary treatment of circulatory insufficiency and shock if plasma expanders aren’t available.
• SIADH (or use 3% sodium chloride).
• Addisonian crisis

PRECAUTIONS

• Do not use in patients with cardiac or renal failure because of danger of heart failure and pulmonary edema.
• Watch for fluid volume overload.

D5 1/2 NS 

DESCRIPTION

• Dextrose 5% in 0.45% saline
• Hypertonic (406 mOsm)

USES

• DKA after initial treatment with normal saline solution and half-normal saline solution – prevents hypoglycemia and cerebral edema.
• Most common postoperative fluid
• Useful for daily maintenance of body fluids and nutrition, and for rehydration.

PRECAUTIONS

In DKA, use only when glucose falls < 250 mg/dl.

D5LR

DESCRIPTION

• Dextrose 5% in Lactated Ringer’s
• Hypertonic (575 mOsm)

USES

• Same as LR plus provides about 180 calories per 1000cc’s.
• Indicated as a source of water, electrolytes, and calories or as an alkalinizing agent.

PRECAUTIONS

• Contraindicated in newborns (≤ 28 days of age), even if separate infusion lines are used (risk of fatal ceftriaxone-calcium salt precipitation in the neonate’s bloodstream).
• Contraindicated in patients with a known hypersensitivity to sodium lactate.

NORMOSOL-R 

DESCRIPTION

• Normosol
• Isotonic (295 mOsm)

USES

• Replaces fluid and buffers pH.
• Indicated for replacement of acute extracellular fluid volume losses in surgery, trauma, burns or shock.
• Used as an adjunct to restore a decrease in circulatory volume in patients with moderate blood loss.

PRECAUTIONS

• Not intended to supplant transfusion of whole blood or packed red cells in the presence of uncontrolled hemorrhage or severe reductions of red cell volume.

COLLOIDS

These are solutions that contains large molecules that do not pass through semipermeable membranes and therefore remain in the blood vessels. Also known as volume/plasma expanders, colloids expand intravascular volume by drawing fluid from the interstitial space into the vessels through higher oncotic pressure. Less total volume is required compared to IV fluids. Colloids are indicated for patients in malnourished states and patients who cannot tolerate large infusions of fluid. Examples of colloids are Albumin (5%), Albumin (25%) and Hetastarch (6%).