INTRAVENOUS FLUID THERAPY

An awareness of fluid balance has its beginnings in the writings of Claude Bernard, who in his final published work emphasized the importance of the extracellular fluid in the support of vital functions.^[176] In these writings, he stressed that blood and lymph bathe the cells of the body and that these fluids constitute the milieu interne, later called the fluid-matrix by Walter Cannon. These researchers pointed out that the organism's freedom from external disturbances such as hunger, thirst, and cold is brought about by mechanisms that maintain uniformity of the bodily fluids. The concept of the steady state maintained in this internal environment became known as homeostasis in the Cannon doctrine.^[177] During anesthesia, many of the homeostatic mechanisms are abolished or severely blunted, and the anesthesiologist must assume the role of maintaining a favorable milieu interne.

Crystalloids

In the late 19th century, the sodium content of serum was found to be roughly equivalent to an aqueous solution of 0.9% sodium chloride, and this became known as physiologic salt solution. Hartog J. Hamburger (1856–1924) showed a volume change in red blood cells at concentrations above and below 0.9% saline.^[178] As a result of these experiments, the value of sodium ions in the maintenance of osmotic pressure in the serum was realized. Ernest H. Starling^[179] (1866–1927) extended these observations to explain edema formation on the basis of hydrostatic and colloidal osmotic pressures.

Maintenance of fluid balance was not a priority or even a possibility for those who administered anesthetics during the 19th century. Without intravenous access, there was little the anesthesia provider could do if the surgeon was recklessly losing blood. The importance of intravenously administered salt in patients with dehydration

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The experimental introduction of saline infusions after surgery was based on work performed by Emil Schwarz^[181] (1852–1918), who observed that saline infusions could save the lives of bled rabbits. This work was recognized by Johann J. Bischoff^[182] (1841–1892), who reported that a salt infusion saved the life of a woman with severe post-partum hemorrhage. Treatment with salt infusions was generally adopted after surgical hemorrhage, but sepsis and failed attempts to revive the bleeding patient soon became apparent.

Alternative solutions to saline originated with Sydney Ringer ^[183] (1835–1910), Professor of Medicine at University College, London. Ringer observed that saline prepared from distilled water was not as effective as saline made from pipe water in maintaining the contractility of the isolated frog heart. After a careful analysis of the pipe water, he learned that it contained the impurities of calcium and potassium. Adding these cations to the saline made from distilled water proved his hypothesis that these ions played an important role in maintaining normal cardiac function.

In the first decades of the 20th century, there were substantial barriers to the successful use of parenteral electrolyte solutions during surgery. Closed sterile administration sets and intravenous cannulas were slow to develop, and alternative methods therefore were employed. Most patients received several liters of fluid, usually administered rectally; however, salt was administered, if possible, orally or by subcutaneous injection. With these ineffectual methods, the use of saline in the perioperative period fell into decline. In 1944, a syndrome was described as postoperative salt intolerance, caused ostensibly by the failure of the kidney to excrete a salt load.^[184] These ideas had the support of the influential Francis D. Moore, Chief of Surgery at Peter Bent Brigham Hospital in Boston. When intravenous therapy became more widely available, patients were often administered dextrose and water or dilute sodium-containing solutions. Carl Moyer^[185] (1908–1970) presented evidence in 1950 that sodium was avidly retained postoperatively and argued against the use of saline for perioperative fluid maintenance.

The reintroduction of perioperative saline therapy began in 1959, when G. Shires^{[186] [187]} and associates reported the redistribution of extracellular fluids into "third space" compartments during extensive surgical procedures. These reports encouraged preoperative fluid administration to compensate for the lack of oral intake and intraoperative sodium-containing fluid administration to replace translocation of extracellular fluid into edematous spaces such as gut and peritoneum. The increased use of saline reduced the incidence of postoperative renal failure and decreased the requirement for blood transfusions. As a result of these studies, fluid replacement today consists of saline-containing fluids, with the addition of colloid and blood when excessive blood loss occurs.^[188]