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IOP range considered safe after vitrectomy with intraocular gas, travel at altitude
Patients would be permitted to return home immediately instead of remaining local for up to a month postoperatively.
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Patients traveling by land over mountainous elevations within a day of undergoing pars plana vitrectomy with intraocular gas had a mean final IOP that was within the safe range, according to a study.
“For years, I have been treating these patients from the so-called high desert — an area basically between Los Angeles and Las Vegas,” co-author Firas M. Rahhal, MD, a partner at Retina Vitreous Associates Medical Group in Los Angeles, said. “We see patients in clinics near their home but perform the surgeries down here in the Los Angeles Basin, at various hospitals and near sea level.”
Patients are sent home either the day of surgery or the next day. However, many surgeons around the country have difficulty deciding which patients should stay local and which patients should be allowed to return home or stay at higher elevations, Rahhal told Ocular Surgery News.
“It is arduous for the patient to come down for surgery and then remain locally for up to a month or more. Being able to immediately return home saves the patient money, time and hardship,” he said.
Predictable expansion
Rahhal said it has been widely known since the 1970s, when intraocular gases began being used, that decreased atmospheric pressure causes the gas bubble inside the eye to expand under fairly predictable physics principles.
“This expansion can induce massive elevation and sudden elevation of IOP, leading to potential blindness,” Rahhal said, crediting his mentor and teacher, Harvey A. Lincoff, MD, of New York-Presbyterian/Weill Cornell Medical Center, for developing the concepts and studies on how gas behaves at different altitudes in human and animal eyes.
In the retrospective study of 75 patients, published in Retina, all surgeries were performed at Good Samaritan Hospital in downtown Los Angeles between 2006 and 2010. Patients traveled up to 90 miles, principally from Victorville, Calif. On their way home, all patients stopped at a designated rest area at an altitude of 3,159 feet above sea level for at least 90 minutes.
“You want a patient to stop somewhere in the safety zone, high enough in elevation so that the bubble will have expanded but not to the point where the expansion can cause blindness or severe pain,” Rahhal said. “Try to select a halfway random spot.”
All patients reached a minimum height of 4,259 feet during their travel home.
Postoperative IOP
All postoperative visits — the first visit on postop day 1; the second visit a median of 10 days postop — took place at a clinic in Victorville at an altitude of 3,151 feet above sea level.
“The results of the study were very impressive,” Rahhal, an associate clinical professor of ophthalmology at the David Geffen School of Medicine at the University of California, Los Angeles, said. “None of these patients experienced a clinically relevant elevation of IOP that would cause sight-threatening complications that most of us fear by sending patients with gas bubbles up to a certain elevation.”
By the time patients arrived home, the intraocular gas was calculated to have expanded 11%, an apparently tolerable percentage, according to Rahhal.
There was a slight trend toward greater IOP change in patients who received C3F8 than in those who received SF6, as well as in patients who were phakic rather than pseudophakic. However, neither finding was thought to be clinically significant, Rahhal said.
“Surgeons should now feel comfortable administering gas rather than silicone oil, which is usually considered second-line therapy in a normal situation,” Rahhal said.
No patient had an IOP greater than 35 mm Hg on postop day 1.
“Based on anecdotal experience, the number of patients who had elevated IOP on day 1 through day 5 was about the same as we would expect in normal surgery performed at sea level,” Rahhal said. “This came as a surprise.” – by Bob Kronemyer