To the Editor:—
Our transesophageal echo probes started to leave tenacious gray-green stains on the mouths of our cardiac surgery patients. The problem began when we were required to change our probe-disinfecting procedures. We had been using glutaraldehyde, which did not stain the probes (Philips Omniplane models I and II, Philips Medical Systems, Andover, MA). Unfortunately, glutaraldehyde is volatile, and its fumes were polluting the air of our probe-cleaning workroom. Therefore, we adopted less-volatile ortho -phthalaldehyde (OPA) as a disinfecting agent. Ugly OPA-derived oral stains were forthcoming and were not reliably prevented by copious rinsing of the probes with water (four times, 2 l). Staining is prominent when, as is common in cardiac anesthesia, an OPA-treated probe (but not a glutaraldehyde-treated probe) remains in prolonged contact with a patient on whom an endotracheal tube is secured with cloth adhesive tape. The stain first appears on the tape (both the Kendall Curity, Mansfield, MA, and 3M Health Care, St. Paul, MN, products) and can be transferred to the lip through routine manipulation of the probe. The lip stain is initially difficult to scrub away, but it does fade in a few hours with no apparent sequelae.
OPA is well-known to form deeply colored dyes with other molecules. 1Prolonged exposure to saliva and tape elicit visibly detectable dye from minute traces of OPA residues remaining on copiously water-rinsed echo probes. Although water rinsing does not reliably remove chromogenic residues from the probes, no stains are elicited from OPA-treated probes that are gently wiped clean with 3% hydrogen peroxide solution after the OPA protocol.
Guidelines from one echo probe manufacturer mention that staining may occur if the standard OPA protocol is not performed “meticulously.” Rather than breaching protocol, we have encountered especially favorable chromogenic conditions that unmask otherwise invisible trace residues.
It is theoretically troubling to discover that traces of OPA residue can cling to echo probes and then be transferred to patients. We have not established the identity of the staining material, nor have we determined what happens when it is inactivated by peroxide. The peroxide may remove the residues or it may merely render them nonchromogenic. We note that, like OPA, peroxide is federally approved for disinfecting endoscopy equipment. However, the common 3% solution is too dilute to be relied on for high-level disinfection.