 Blood loss due to severe trauma is one of the leading causes of death in Americans 1 to 44 years old. When too little blood flows through a person’s organs, the heart begins beating rapidly, the skin becomes cold and pale, blood pressure plummets, and patients exhibit mental confusion. Treating severe blood loss, therefore, is vitally important to physicians worldwide. It also is the research focus of UC San Diego bioengineering professor Marcos Intaglietta, whose team made an astonishing discovery while performing fluid resuscitation experiments on hamsters.
The Advanced Trauma Life Support (ATLS) guidelines, the worldwide standard for emergency medical care, calls for intravenous administration of isotonic fluids for severe blood loss. (Isotonic fluids have the same salt concentration as the normal cells of the body and the blood). But building on earlier studies in humans, Intaglietta tested a resuscitation hypertonic fluid that contained saline that was eight times saltier than normal, combined with viscosity enhancers that actually thicken blood.
“Trauma physicians want to get the blood flowing as soon as possible, and increasing the viscosity of blood may not make any sense to them,” says Intaglietta. “However, our results are highly suggestive that increasing viscosity and partially restoring blood volume is a better way to increase blood flow through tissues.”
Very small arteries called arterioles regulate blood flow by constricting and dilating. Intaglietta’s team carefully measured the effect of various fluids on blood flow through arterioles and even smaller vessels called capillaries. The team found that hypertonic saline combined with viscosity enhancers was much better than isotonic fluids in dilating small blood vessels.
“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,” says Intaglietta. “Even as late as World War II and the Vietnam War, 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.”
|
