Millions of people in the workplace are exposed to potential injuries from vibrations caused by powered-tools. Past studies have shown that years of working with hand-held powered-tools could cause hand-arm vibration syndrome (HAVS), known as secondary Raynaud's disease of occupational origin.
HAVS is characterized by excessively reduced blood flow, limiting blood supply to the nerves, muscles, and tendons, and blanching of the fingers. The symptoms include pain, tingling and numbness of the hand, which progresses to loss of dexterity. All patients complain of excessive finger blanching when exposed to cold.
The researchers, led by Danny Riley, Ph.D., professor of cellular biology, neurobiology and anatomy, developed a new rat-tail vibration model for studying the early stages of vibration injury. The rat-tail, whose anatomy is comparable to that of the human hand, was an ideal model to study. Both contain blood vessels of similar size, have motor and sensory peripheral nerves and have muscles and tendons of intrinsic and extrinsic origin. This similarity permits researchers to extrapolate from what happens to cells during tail vibration to that expected in the arteries in the human hand.
By studying the structure of the blood vessels, researchers demonstrated that four hours of vibration causes blood vessel constriction and produces damage to arterial smooth muscle and the endothelial cells that line the vessels.
The researchers also showed that blocking vasoconstriction by premedicating the animal with nifedipine, a calcium blocker, to prevent smooth muscle contraction during vibration, prevented arterial damage.
Sandya Govindaraju, a graduate student in Riley's laboratory, presented the study April 19 at Experimental Biology 2004 as part of the scientific program of the American Association of Anatomists.
"These novel findings indicate that vibration and vasoconstriction act synergistically to damage arteries. The types of early morphological damage observed are likely to lead to vibration syndrome in the long term. Thus, our data suggest that medications and other countermeasures that prevent vibration-induced vasoconstriction may reduce the chances of hand-arm vibration syndrome," said Riley.
The management of HAVS is non-specific and symptomatic with little therapeutic advancement in the past few decades. While HAVS is well described in its last stages, when it is not reversible, there is very little information about the cellular events involved in the early development of the disease.
"Preventing vasoconstriction by pharmaceutical agents limits vibration-induced vascular damage. The potential for harm by vibrating tools is under-appreciated by the public and not well known. Knowing what happens early on, would not only aid awareness but also help formulate preventive strategies, better screening procedures and specific treatment of HAVS before it becomes irreversible," said Riley.