Canadian Consulting Engineer
Specialty Sinks for Burn Treatment UnitEngineering
The Walter C. Mackenzie Health Sciences Centre in Edmonton is a major hospital and learning centre for the University of Alberta. Within the hospital, the new 11-bed Firefighter's Burn Treatment Unit...
The Walter C. Mackenzie Health Sciences Centre in Edmonton is a major hospital and learning centre for the University of Alberta. Within the hospital, the new 11-bed Firefighter’s Burn Treatment Unit opened in 2000 for patients with severe burns.
Burn survivors are very prone to infection as their immune systems are compromised. Four patients in the burn unit became infected with a multi-drug resistant Pseudomonas aeruginosa infection. Three patients developed wound infections prolonging their hospitalization. One patient died as a result of complications from the infection.
The organism was traced to hand wash sinks used by the burn unit staff. Repeated attempts to disinfect the sinks over a period of six weeks while they were not used were not effective and tests continued to show positive cultures. The problem with the sinks seemed to be related to the traps where a poor design allowed standing water within an inch of the basin.
Hemisphere Engineering was asked to develop a special hand wash sink for the burn unit that would reduce or eliminate the opportunity for the Pseudomonas aeruginosa organism to flourish.
Research on the organism determined that it will multiply in warm standing water. The microscopic organism has multiple “legs” which allow it to cling onto mini cracks on surfaces and multiply in colonies. Attempts to disinfect using bleach or alcohol are effective in killing the outer members of the colony, but are ineffective in reaching the organisms within cracks and crevices of a “standard” stainless steel sink. Over time, the surviving organisms develop a resistance to the usual procedures for disinfecting these surfaces.
Considering how the colonies grow and considering the opportunity of splash back from the sink trap onto adjacent surfaces, a 316 stainless steel sink was designed with rounded corners and steep sloping surfaces to the drain. The “tailpiece” was welded onto the sink body and ground smooth to eliminate any cracks for colonies to attach to and propagate. Splash guards were extended up the side and back of the sink to prevent water from splashing onto adjacent countertop surfaces.
All the stainless steel surfaces exposed to water were highly polished to a mirror finish to eliminate opportunities for the organism to cling to microscopic cracks and propagate.
The water supply through the downspout was offset to avoid water directly falling into the trap, thereby avoiding splash back from water contained in the trap onto the sink surfaces. Also a soft aerator nozzle was used to avoid splashing and having a “hard” impact on water accumulated in the trap.
Special attention was given to the tailpiece configuration and trap assembly. The tailpiece was extended to provide maximum separation between the trap and the body of the sink to limit the geometry of any potential for splash back from the trap.
Research confirmed that Pseudomonas aeruginosa bacteria could be killed by exposure to ultraviolet light. Accordingly, in the specialty sink, the standard “P” trap was replaced by a horizontal ultraviolet tube. The tube acts as a trap for the sink and provides a delay time to irradiate the sink effluent, thereby eliminating an opportunity for the organism to multiply in the trap.
A trap primer was fitted in between the ultraviolet tube and the sink drain to allow a dribble of fresh water to continuously flow through the trap. This design eliminated stagnant pools and the opportunity for the bacteria to colonize.
To protect the plumbing contractors’ staff when they removed the existing sinks, they were required to follow special measures of gowning and washing. All their tools and materials were sterilized after use. During installation, the rooms containing the sinks were isolated and protected with plastic sheets. Ten sinks on the unit were replaced in pairs at a total installed cost of $83,570.
The concern with “super bugs” is becoming a reality in health care facilities everywhere. The unique design of the sink has application in health care facilities where patient resistance is severely compromised and where patients are vulnerable to infections that are becoming increasingly difficult to treat.
Since the sinks have been installed in the Walter C. Mackenzie Health Sciences Centre burn unit no environmental or patient nosocomial infections with the multi-drug resistant organism have occurred.
Name of project: Specialty Sinks, Firefighter’s Burn Treatment Unit, Walter C. Mackenzie Health Sciences Centre, Edmonton
Award-winning firm: Hemisphere Engineering, Edmonton (Robert A. Campbell, P.Eng.)
Role of award-winning firm: mechanical engineering consultant
Owner: Capital Health
Other key players: Edward E. Tredget, MD (medical expert)