The decision on whether to allow Alexandria Hospital to open an eight-bed kidney dialysis center has been postponed until September. The action came this week after Northern Virginia's regional health planning agency was stalemated by a tie vote.

At the same time, the planning group, the Health Systems Agency (HSA) of Northern Virginia, rejected another request to allow an existing dialysis center in Annandale to expand. The center, operated by Bio-Medical Applications of Arlington, had sought the addition of three beds to the Annandale center, but was denied the request primarily because the center has "closed" staffing.

The controversial policy of closed staffing does not allow patients to have their own doctors supervise the dialysis, but requires them to use a clinic's staff of doctors. The treatments -- usually three-hour sessions three times a week to cleanse the blood of persons with malfunctioning kidneys -- cost $20,000 to $25,000 a year in doctors' fees and clinic charges, most of it paid by federal Medicare funds.

"There's a lot of money in dialysis, and we'll have another application in here" before long, said Mark Melcher, an HSA board member from Prince William County who opposed the creation of a $350,000 dialysis center at Alexandria Hospital as "too expensive."

However, the planning agency staff has said the start-up costs of the hospital clinic are comparable to those of the four existing clinics in Northern Virginia and its proposed charges are actually lower, although the hospital could subsequently raise its rates.

The agency staff has urged approval of the hospital center, proposed to open in the fall of 1981, because it anticipates an increase in the number of patients needing dialysis. About 200 local residents now visit Northern Virginia's clinics regularly and others are using dialysis equipment at home.

A tie vote among 18 of the planning agency members present at this week's meeting would have left the Alexandria Hospital decision up to Virginia's commissioner of health and would have been the first time in the seven-year history of the regional health agency that it had failed to take a position on the issue.

The hospital application, which must be acted upon within 90 days, or before early October, will come up again at the health agency's Sept. 8 meeting when most of the 27 board members are expected to be present. Nine board members, including two of Alexandria's three members, were on vacation during this week's meeting.