kristalloide

Kristalloide, or crystalloids, are intravenous solutions composed of water with small solute molecules such as salts or sugars. These solutes freely diffuse across capillary membranes, so crystalloids influence both intravascular and interstitial fluid volumes. They are commonly used for fluid therapy in a variety of clinical settings and are distinct from colloids, which contain larger molecules that stay primarily within the vascular space.

Isotonic crystalloids have osmolality close to that of plasma and are the most widely used. Examples include 0.9% sodium chloride (normal saline), lactated Ringer’s solution, and Plasma-Lyte. Hypotonic crystalloids (for example 0.45% NaCl) have lower osmolality and are used with specific indications. Hypertonic crystalloids (such as 3% or 7.5% NaCl) are reserved for particular conditions, typically under close monitoring, such as severe hyponatremia or intracranial hypertension. Dextrose-containing solutions behave as crystalloids initially but become hypotonic after glucose is metabolized.

Indications for crystalloids include volume resuscitation in hypovolemia, dehydration, and shock, as well as maintenance fluids and replacement of ongoing losses. They are favored for being inexpensive, readily available, and versatile. Balanced crystalloids (e.g., lactated Ringer’s, Plasma-Lyte) are often preferred over 0.9% NaCl because they more closely resemble plasma electrolyte composition and may reduce the risk of hyperchloremic acidosis and kidney stress.

Risks of crystalloids include fluid overload, edema, electrolyte disturbances, and acid–base shifts, particularly with large volumes or inappropriate choices. Clinicians tailor type and amount to the patient’s hemodynamic status, electrolyte profile, and underlying conditions.