The successful treatment of kidney failure patients depends on service technicians.
Dialysis patients, like the one pictured on the left, undergo hemodialysis because their own kidneys are ineffective. Dialysis technicians must properly maintain the systems to prevent patient blood cell loss or destruction.
Hemodialysis is a delicate process that depends on doctors, nurses, technicians, and the patients themselves. It also depends on the repair technicians who fix and maintain the dialysis machines—and the water purification systems that go with them. A fluid temperature too high or too low, a blood leak, or an air leak, and patients can find themselves in big trouble fast.
“Can we hurt somebody? Absolutely,” says Jack Crouch, biomedical engineering manager for dialysis units at Scott & White Hospital in Temple, Tex. “Say we don’t calibrate the temperature correctly or we don’t do it period, and the temperature goes too high on the bath. The only thing that separates that concentrate from the blood is a very thin membrane that lets impurities cross to the dialysate. If the temperature is too warm, that membrane is not going to protect that patient.”
The result, adds Crouch, could be “gross hemolysis causing (red) blood cells to burst.” Yet, for all the potential mishaps in dialysis they seldom happen, Crouch says, “because we make sure people know what they’re doing.”
How It Works
Hemodialysis is the application of an artificial kidney machine to cleanse urea and other impurities from the blood of people whose kidneys have failed or diminished in function. The failure can be temporary, due to trauma or drug overdose, or it can be permanent, brought on by a number of factors, including kidney inflammation, high blood pressure, diabetes, and inherited maladies. There are about 300,000 kidney dialysis patients in the United States, according to the American Association of Kidney Patients. Only about 12,000 patients per year receive a kidney transplant.
The typical end-stage renal disease (ESRD) patient undergoes three hemodialysis sessions per week, each lasting as long as 4 hours. Because the kidneys don’t work, ESRD patients cannot urinate, and all the impurities that would normally pass with urination are stored in the body and must be cleansed by dialysis. The water that is the bulk of urine also accumulates and must be drained away in the dialysis process. Patients are assigned a target “dry weight” that should be achieved with each dialysis session to assure that adequate excess water has been removed.
“Patients need to stay at their dry weight,” says Charles L. Jones, BMET, who works on dialysis equipment at St. Francis Hospital in Tulsa, Okla. “We will enter into the machine how much they are supposed to weigh, and it will remove the water down to the dry weight.”
The heart of the dialysis machine is the dialyzer or artificial kidney. The dialyzer is a complex filter that lets blood travel past a membrane—actually a collection of tiny strawlike membranes—through which impurities can pass, but through which blood cells, proteins, and other necessary blood elements are too big to pass. On the other side of the membrane is a cleansing fluid called a dialysate that contains sodium and other chemicals to help draw impurities and excess water out of the blood. The pressure on the dialysate side of the membrane is lower than the pressure on the blood side, so chemicals in the dialysate do not pass through the membrane back into the blood.
Because chlorines and other impurities in the dialysate could cause blood cell loss, the water used for dialysis has to be purified either through deionization (DI) or reverse osmosis (RO). Dialysis technicians often maintain water purification systems along with the dialysis machines. Like dialysis, RO purification makes use of a membrane to separate pure water from what flows out of a tap.
“We have to maintain a water-treatment plant,” Crouch says. “We use RO to force [city] water across a membrane. The good water makes it across. We have to have 8 gal a minute of good water, so we have to use 16 gal. The impurities stay in the 8 gal that remain behind. It’s a pretty expensive process. We are using over a million gallons of water per year.”
Crouch and his crew oversee nearly 80 dialysis machines, about half of them at the main 400-bed hospital and the rest at clinics in the nearby towns of Round Rock and Killeen, Tex.
Hydraulics and Electronics
Because dialysis machines use hydraulics as well as electronics to monitor various pressures and flows, they are different to work on than other equipment the biomedical engineer typically encounters.
“I have more problems with hydraulics and plumbing than with electronics,” Jones says. “The water is flowing through the machine at 700 mL per minute. That can make a big mess if you have a leak, and if it’s coming out of a certain part of the machine it may be patient waste.”
When machines are being rolled into position, snagged hoses can cause hydraulic leaks.
“The only time we have leaks is when the connector O-ring slips off or splits,” says Duff Burkes, team leader for biomedical engineering at Methodist Dallas Medical Center in Dallas, which has about 500 beds. “When we have a leak, it’s usually when the machine was being moved and the hose caught on something, but those are easily fixed.”
Burkes says it’s rare that electronics go out on the 14 machines that his group maintains. However, sometimes software that guides the electronics has to be rewritten.
While hemodialysis electronics tend to be reliable, their function is critical and is monitored carefully. If a needle slips from a patient’s vein, an alarm must sound to alert nurses or technicians. Other alarms are set off by blood leaks and changes in flow, pressure, and temperature of either blood or dialysate. And dialysates have to be mixed differently for each patient according to a physician’s prescription. The content of the dialysate determines what impurities and how much of them get pulled through the membrane and eliminated.
Because dialysis machines are complex and their function critical, they have self-testing systems that check the various monitoring devices.
“They can check for air in the venous chamber. There is a blood-leak alarm. The machine comes with heaters because we don’t want to send cold blood back to the patient,” Jones says. “Our policy is that before each patient is put on the machine it has to pass the self-test. That test takes about 5 minutes.”
By law, backup dialysis machines must be available at hospitals and treatment centers so that in the case of a failure, the patient can be switched to a working machine. At Scott & White Hospital in Temple there are seven spares, says Crouch, plus four additional spares at each of the outlying sites. The spares prevent scheduling disruptions and allow time for repairs to be made on machines that do fail.
“Some of the biggest problems we run into,” Crouch says, “are things that come up only periodically, intermittent problems. A nurse might say there is an intermittent flow alarm on a machine. We bring it into the shop and it runs fine for 2 days. We run all the tests and put it back out there. It runs for a week and the nurse says there’s a flow problem. OK, you know it’s a sticky valve, but how are you going to find it? You hope like heck you can find it, but sometimes you have to bring it back to the shop and let it run till it fails.”
The design of some machines can lead to headaches with fluids and electronics being so close together.
“A common mistake is to put the wet components over the dry components, and eventually there’s a leak,” says Philip Andrysiak, MBA, CHT, a dialysis consultant based in southern Florida. “They put huge transformers in the base and the hydraulic pump over that, and inevitably something leaks. You are constantly looking for leaks. Sometimes the O-rings go bad on the fluid side. All kinds of electronics go bad—pressure-sensitive systems, magnetic valves.”
Andrysiak says all manufacturers write preventive maintenance (PM) schedules for their machines. “The service manuals take you step-by-step. The O-rings are replaced every couple of months. Every year there is a complete maintenance check.”
Some service engineers like to service the machines well within the manufacturer’s schedule just to be extra safe.
“With the dialysis machines, the PMs are the key to making them work all the time,” Burkes says. “Every 1,000 hours is the first level, the O-rings and some rubber parts. At that time we also do an operations check. At 4,000 hours we do a replacement of all rubber goods and check valves to see if they need replacement. It usually takes more than 3 months to get to 1,000 hours, but we do it quarterly anyway, and the 4,000 once a year if it needs it or not. The only time we have a problem is when we have a high patient census. Once, maintenance had to wait for a month but it didn’t break the 1,000 hours. Sometimes we have a piece of equipment set up for PM and the nurses won’t let us have it.”
Service engineers are more careful working on dialysis machines than they used to be, Burkes says. “We used to work on the machines without gloves. It’s amazing we didn’t get sick. We used to handle patient waste with no hand washing. Now before we work on a machine, it’s required that it be wiped down, bleached, and disinfected. When we get into the waste side of the unit, we wear gloves and a jump suit or a disposable lab coat.”
To keep track of its dialysis machines, the Methodist Dallas dialysis team names each one, Burkes says. Some are named after cartoon characters or former physicians. Burkes even has one named after him. “It’s fun, but it also helps us identify problems with these machines,” he says.
Maintaining water treatment and dialysate systems may also be part of the dialysis service engineer’s job description. “I come in on Sundays to disinfect the bicarbonate system,” Jones says. “That way I can get to it when the staff is off.”
Richard Runyon, CBNT, oversees service at a DaVita’s dialysis clinic in Longview, Tex. DaVita is a national company that provides dialysis services. Part of Runyon’s job is to service the water-treatment equipment that purifies water for the dialysate.
“We have a softener, ionization tanks, and ultraviolet treatment,” Runyon says. “The RO machine is huge; that’s what actually purifies the water. It goes to the RO to take out the metals and salts and then the ultraviolet and deionization before it goes out to the treatment floor. You can do dialysis with DI or RO. We use both, as a backup. Our water is doubly purified.
“Every month we draw cultures to make sure we don’t have any bacteria. Then, within 3 days of drawing cultures we do a bleach disinfect on the whole loop. We’re taking proactive steps by drawing the cultures. We just want to monitor it and see if there is a problem developing.”
Tragedy and Duty
While dialysis service engineers do not interact directly with patients, they see them all the time. They get to know some of them and witness the often-tragic outcomes of their kidney disease.
Dialysis is rough on patients. A dialysis machine is not as efficient as a real kidney. The treatment places wear and tear on patients, who must have blood entrance and exit needles stuck into their bodies and go on the machine over and over, 4 hours a day three times a week, for as long as they live. Many patients are elderly diabetics who submit to dialysis only because loved ones insist upon it.
“They are trading quality for quantity of life,” Runyon says. “It happens quite frequently that people will say they’ve had enough, that they don’t want dialysis any more.” When that happens, Runyon says, the patient usually dies within a week or two. Their bodies build up with impurities and excess water.
“They basically drown,” Runyon says. “Dialysis is life support, literally.”
It is the life-support aspect that keeps dialysis service engineers motivated. People are staying alive because of the work that dialysis service technicians do. Younger patients have gone for 2 decades or more on dialysis, and there are no known upper limits of when the treatment loses effectiveness. The work done by dialysis service technicians helps people live.
“They say biomeds are typically the invisible teammate,” Runyon says. “But this is really a wonderful job field. There is always something interesting every day. I love the work.”
George Wiley is a contributing writer for 24×7.