Transfusion of the Patient in Shock

During World War I, it was believed that vascular collapse in injured patients was caused by toxins (MacLean, 1985). Experiments in the 1930s showed that fluid was lost from the circulation into damaged tissues. In World War II, plasma became the resuscitation fluid of choice. Subsequent experimental work indicated that extracellular fluids shifted into the intracellular space after significant hemorrhage with shock (Canizaro, 1973). The provision of resuscitation fluid in a volume in excess of the volume of blood that had been shed then became an acceptable practice for the maintenance of adequate circulation.

During World War II, acute tubular necrosis was a common consequence of hypovolemic shock. Because fluid resuscitation became more prevalent during the Korean and Vietnam conflicts, the incidence of acute tubular necrosis dramatically decreased. Although acute tubular necrosis after hypovolemic shock became less of a problem with better fluid resuscitation, the shock lung syndrome (i.e., adult respiratory distress syndrome) became increasingly common. The lung injury in adult respiratory distress syndrome is a function of the shock state rather than the resuscitation solution used.

The goal of resuscitation from shock is prompt restoration of adequate per-fusion and transport of oxygen. Restoration of circulation allows the cell to clear the products of anaerobic metabolism and restore aerobic metabolism. The American College of Surgeons Committee on Trauma developed a classification of shock that permits useful guidelines for resuscitation (1997). Crystalloid is infused at a 3:1 ratio for every unit of red blood cells administered, and therapy is monitored by hemodynamic response. Because crystalloid solutions are universally available and some delay is required for the preparation of blood products, crystalloid is the proper initial resuscitation fluid. Resuscitation then proceeds with the use of blood products, depending on the patient's response. The choice of a colloid solution (e.g., albumin or plasma) or a crystalloid solution (e.g., lactated Ringer's solution) has been controversial. Both can expand the extracellular space and provide effective resuscitation. However, crystalloid solutions are favored because they are less expensive, need not be cross-matched with the patient, do not transmit disease, and probably create less fluid accumulation in the lungs. No experimental data indicate that colloid solutions are less apt to prevent pulmonary edema than are crystalloid solutions. Some work (Holcroft and Trunkey, 1975; Lewis et al., 1979), based on measurements of pulmonary extravascular water volume or lung water measurements, indicates that albumin, if used as a resuscitation fluid, moves across the cell membrane and draws in extracellular fluid by osmosis, thereby exacerbating the pulmonary edema.

Several crystalloid solutions are available for resuscitation, but isotonic solutions should be used to avoid overload of free water. Lactated Ringer's solution has been recommended as initial therapy. Metabolic alkalosis is common after successful resuscitation with lactated Ringer's solution and blood products, because the lactate in Ringer's solution and the citrate in banked blood are both



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