Origin of TASS outbreak still in question

San Francisco-Identifying the cause of toxic anterior shock syndrome (TASS) was investigated in two trials, one performed by Simon P. Holland, MD, and colleagues and a second done by Liliana Werner, MD, PhD, and associates.

The two groups, who reported their findings at the annual meeting of the American Society of Cataract and Refractive Surgery, identified different culprits, namely, short-cycle sterilization and an ointment, respectively. (See related article, "Cause of recent TASS outbreak unknown," Ophthalmology Times, May 15, 2006, Page 1.)

Dr. Holland and colleagues undertook a retrospective study to determine the origin of long-term TASS outbreaks in two clinics. In the first multi-surgeon clinic, in which 4,500 procedures were performed annually, various methods of sterilization were used, but predominantly short-cycle sterilization, to cut down on the time between cases, and Statum tabletop sterilizers.

During the outbreak of TASS, which occurred over 12 months, four cases were identified in months 6 and 7. An infection control investigation in the hospital recommended that the surgeons switch from multi-use to single-use phacoemulsification tips; this change was implemented during month 9. Another recommendation was that the amount of short-cycle sterilization be reduced. Gram-negative bacteria were cultured from the tabletop sterilizers at that point, but no action was taken.

During months 13 to 17, another 10 cases of TASS developed. At this time, disposable cannulas were used and full cycles of wrapped sterilization were instituted. Short-cycle sterilization was still used for the surgeon's own instruments, according to Dr. Holland.

Specimens from the tabletop sterilizers were cultured twice and showed heavy growth in all three sterilizers, with strongly endotoxin-forming bacteria; Pseudomonas, Sphingomonas, and Ralstonia were the most predominant. In addition, contaminated sites were found, namely, the ultrasound bar and the reservoirs of the sterilizers had never been cleaned. The sterilizers were exchanged and a cleaning protocol was instituted that consisted of daily cleaning and use of ammonia.

"When the changes were made, the outbreaks resolved with the final step of the change in the cleaning protocol," Dr. Holland reported.

Cultures were positive in only one of the 12 patients in whom TASS developed. The incidence of TASS was about 1.5 per 1,000 procedures.

"The control measure that was ineffective was switching to single-use phacoemulsification tips," he said. "The positive steps were limiting the short-cycle sterilization, increased use of disposable cannulas, and reservoir cleaning."

In the second, more recent, TASS outbreak, the clinic also had a high number of procedures (in excess of 4,000 annually) performed by multiple surgeons. The TASS outbreak occurred over 24 months. The cases developed in multiple small clusters, with a total of 23 days of surgery affected. One to six cases developed daily. The incidence was 2.1 per 1,000 cases. Five cases developed during the first month.