Hyperviscous fluids: Better treatment for severe blood loss

However, several medical research teams, including one led by Dr. Raul Coimbra, professor of surgery and chief, Division of Trauma, Surgical Critical Care and Burns at UC San Diego Medical Center, have investigated the effects of hypertonic saline for almost 20 years. “Our level-1 trauma center at UC San Diego is participating in a study of hypertonic saline as part of a multicenter trial sponsored by the National Institutes of Health,” said Coimbra. “Unfortunately, it will take us two to three more years to finish the trial and determine whether hypertonic saline is superior to conventional isotonic resuscitation.”

In Intaglietta’s study with hamsters in the Jacobs School of Engineering’s Department of Bioengineering, 90 minutes after hypertonic saline was given to blood-depleted hamsters about 30 percent of normal flow was reconstituted through skin arterioles, tiny branches of arteries that lead to the even smaller capillaries. The bioengineering researchers quantified blood flow with special microscopic procedures.

In blood-depleted hamsters given both hypertonic saline and a small volume of a commercially available viscosity enhancer called Hextend®, blood flow through arterioles improved to 40 percent of normal. When the hypertonic saline, Hextend®, and a small volume of another viscosity enhancer called alginate were given, arteriole blood flow improved to 55 percent of normal. Hextend® and alginate are plasma volume expanders, substances transfused to maintain the fluid volume of blood.

“Our findings suggest that elevating the viscosity of blood after severe blood loss is beneficial in resuscitation,” said Intaglietta. “In fact, our studies indicate that Hextend and similar plasma extenders could produce even greater benefit if they were formulated with higher viscosities.”

Arterioles regulate blood flow by constricting and dilating. A variety of factors in the body influence the process, including the viscosity of plasma, the fluid portion of blood. For example, higher viscosity plasma causes arterioles to dilate.

“For centuries, dating back to the time of the early Greeks, the idea has always been that blood is thick, so the sick should be treated by bleeding in order to thin the blood,” said Intaglietta. “Even as late as World War II and the Vietnam Way, it was thought that adding isotonic fluids to replace blood lost on the battlefield would be good because it lowered blood viscosity, making it easier for the heart to pump.”

Intaglietta said that while more research is needed, “Our findings and others suggest that the ATLS guidelines need to be modified.”

“Studies such as Intaglietta’s are important because it uses not only hypertonic saline,” said Coimbra, “but also other adjuncts which may increase the effects of hypertonic saline in treating those patients and in advancing our knowledge about shock resuscitation.”

Co-authors of the Resuscitation report with Intaglietta are Pedro Cabrales, a senior investigator at the La Jolla Bioengineering Institute, and Amy G. Tsai, a research professor in the Jacobs School’s Department of Bioengineering. The research was supported by the National Heart, Lung and Blood Institute and the U.S. Army. Dr. Coimbra’s research was supported by the National Institutes of Health.