Crystalloids are generally considered the primary resuscitation fluid. The most commonly used crystalloid solutions are 0.9% saline (often colloquially and incorrectly called “normal” saline) and lactated Ringer’s solution, a balanced salt solution that contains small amounts of electrolytes other than sodium and chloride (Table 22.2). The anesthesiologist must consider the varying constituents of each solution when planning intravenous fluid therapy. For example, administering large volumes of 0.9% saline can lead to increased serum chloride levels and produce a metabolic acidosis. Alternatively, infusing large amounts of lactated Ringer’s solution can produce the opposite, a metabolic alkalosis, as the lactate in the solution is metabolized to bicarbonate. The provider must also consider the potassium content in the solution. Many patients present to the operating room with an increased baseline potassium level, and increasing it further could be hazardous. Of note, the presence of calcium in lactated Ringer’s solution prohibits its use as a “carrier” solution when administering citrated blood products. The reaction of citrate and calcium will cause red cells to aggregate.

While glucose can be added to intravenous solutions, such mixtures are usually avoided during the perioperative period. Increased serum glucose levels can lead to several unwanted
complications. Unless a patient is at risk for intraoperative hypoglycemia, glucose-containing solutions are not used. These solutions are reserved for long-term maintenance in hospitalized patients who are NPO for various reasons.