The Senate voted overwhelmingly yesterday to extend the life of the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, which was created four years ago after revelations of abuses of research patients.

But it defeated, 48 to 30, a companion bill to try to make doctors investigate new operations and medical machines before they become established at a cost of billions of dollars and, sometimes, an unmeasured cost in harm to patients.

Both measures were sponsored by Edward M. Kennedy (D-Mass.), chairman of a Senate health subcommittee, and three health-minded colleagues - Richard S. Schweiker (R-Pa.), Harrison A. Williams (D-N.J.) and Jacob K. Javits (R-N.Y.). The bill to protect research subjects was cosponsored by Claiborne Pell (D-R.I.).

At least four years would be added to the life of a commission that so far has recommended tightened rules on research involving human fetuses - in effect, permitting few such studies - and measures to protect prisoners, the mentally ill and retarded and many ordinary patients whose doctors are conducting research studies.

The bill was passed 68 to 10 after Kennedy argued that it was needed to prevent overzealous researchers from ignoring human dignity.He and other supporters cited the case that helped lead to the commission's creation - the revelation that several black Alabamians with syphilis were denied treatment for 30 years, even after penicillin's discovery. The demand for more research on new medical methods was defeated after Bob Dole (R-Kan.), said that it would create a new, unneeded federal agency. It would have established a new set of National Institutes of Health Care Research - creating one new institute and expanding two study centers into research institutes - in the Department of Health, Education and Welfare.

This bill was inspired by recent proliferation of costly operations and devices. This includes "CAT scanners" (half-billion-dollar computerized X-ray machines), coronary artery operations, hysterectomies and Cesarean deliveries.

All have been under attack as vastly overused despite lack of studies establishing their proper place or their most economical use.

HEW Secretary Joseph A. Califano Jr. argued in a letter to the Senate that his department was already responding to the admitted need to give high priority to studies of new medical methods.

HEW officials plan to establish a new Office of Health Technology directly under Julius Richmond, assistant secretary for health.

A bill cleared by the House Commerce Committee would likewise create merely an Office of Health Technology in HEW. No bill has been introduced in the House on long-range protection of human subjects.