Hypertonic resuscitation: physiologic mechanisms and recommendations for trauma care.

Hypertonic saline solutions, with or without added colloid, have received extensive evaluation as volume expanders in both animal studies and clinical trials. Most studies have used 7.5% NaCl/6% dextran 70 (HSD). HSD's primary mechanism of action is rapid osmotic mobilization of cellular water into the blood volume. The measured volume expansion efficiency of HSD is equal to 10 times that of lactated Ringer's solution. Part of HSD's effectiveness is because of the hyperosmotic vasodilation of both systemic and pulmonary vessels. Increased cardiac effectiveness occurs because of the combination of increased preload (venous return) and reduced afterload (vasodilation). Increased cardiac contractility also has been reported in several studies and may play a role, but other studies refute a direct effect on contractility. HSD has been shown to be effective and safe with preexisting dehydration. Animal studies of immune function suggest that increased osmolarity prevents T-cell depression and decreases neutrophil activation. Several perioperative and eight randomized, blinded trauma trials have shown safety and reduced volume needs and suggest increased survival, particularly in head- and penetrating-injury patients. Infusion rates for HSD of 10 to 20 minutes may be recommended for the initial resuscitation of hypotensive trauma.