A pain-control catheter is a simple technique developed to address more effectively the significant postoperative pain associated with enucleation, while new strategies such as magnetic coupling are improving the motility of prostheses.
Baltimore-Enucleation can result in significant postoperative pain and considerable emotional trauma, especially when an eye injury swiftly escalates to enucleation. Such patients are often given little time to prepare psychologically.
Yet over the past decade, doctors have worked to improve patient comfort postoperatively and to enhance prosthesis motility for these patients. Advances in pain management and implant technology are furthering these goals, said Shannath Merbs, MD, PhD, FACS, here at the Current Concepts in Ophthalmology meeting.
Improved prosthesis motility was also a topic in Dr. Merbs' presentation. She explained that porous orbital implants currently are the standard of care and are preferred to solid implants. These implants, made of either hydroxyapatite or porous polyethylene, improve stabilization. The prosthesis is not physically attached to the implant; as the implant moves, it drags the conjunctiva and the eyelids.
Dr. Merbs discussed a novel method of pain control in which a family member may repeatedly deliver local anesthetic through an indwelling catheter placed at the time of enucleation. This allows patients to return home rather than spend the night in the hospital. Dr. Merbs and her colleagues at the Wilmer Eye Institute conducted a retrospective review of a series of patients who received this pain control during enucleation. Family members were given syringes of lidocaine mixed with bupivacaine and taught how to inject the mixture through the catheter into the orbit, thereby directly anesthetizing the source of postoperative discomfort and reducing the need for narcotic medications.
Of 67 patients treated on an outpatient basis from Jan. 1, 1998 to Dec. 31, 2001, 58 (87%) reported using the catheter at least once. Ten of these patients reported mild discomfort with the catheter such as slight burning, but none discontinued its use, according to a retrospective analysis published in 2004 in Archives of Ophthalmology.
All of the individuals who used the catheter told investigators that they experienced relief from the postoperative pain of enucleation for periods of 1.5 to more than 4 hours. On average, they kept the catheter in for 3 days, Dr. Merbs said. There were no postoperative complications such as infection or hemorrhage.
"The advantage of that approach is that it's simple and inexpensive," Dr. Merbs said.
The outcomes of this study suggest that the catheter system is effective and accomplishes the objective of enabling patients to recover from surgery in familiar surroundings, Dr. Merbs said.
"The most common surgery-related reason for unexpected hospital admission is pain. By combining an oral agent with delivery of a local anesthetic through the indwelling catheter, you get better analgesia than with either modality alone. In addition, the pain-control catheter allows patients to recover at home after surgery," she added.
Dr. Merbs and her colleagues are also evaluating a magnetic coupling system intended to improve motility by coupling the orbital implant to the prosthetic eye. The implant contains a steel screw coated with titanium; the screw is designed to be attracted to one or more magnets that the surgeon places on the posterior surface of the prosthetic eye.
The investigators studied the motility of prostheses with and without a magnet and found a statistically significant increase in motility with the magnet, according to Dr. Merbs. There was also a statistically significant relationship between the motility of the prosthesis before the magnet was added and the subsequent difference in movement. Greater motility before placement of the magnet was associated with greater increases in movement afterward. In other words, if substantial preoperative muscular damage limits the implant motility, the use of the coupling system would be of little benefit.
In their studies so far, the investigators have observed a couple of instances of screw exposure that required patching. "We have learned that it's important to contour the back of the prosthesis around the magnet so that there's no direct contact between the magnet and the screw. With proper contouring, the pressure is distributed around the screw where the conjunctiva is vascularized. This avoids focal pressure on the conjunctiva over the screw and minimizes the risk of pressure necrosis or exposure," Dr. Merbs advised.