SURGICAL PEARLS

Fluid-Air Exchange Do’s and Don’ts

BY FLAVIO REZENDE, MD, PHD

A crucial step in vitreoretinal surgery, fluid-air exchange sometimes poses substantial challenges. In this article, I discuss some common and not-so-common challenges and how to manage them.

MICROINCISION VITRECTOMY SURGERY

Many surgeons perform fluid air exchanges routinely in microincision vitrectomy surgery (MIVS) to allow the air to help “tamponade” the inner lip of the sutureless sclerotomies, but this is not necessary in all MIVS. For instance, I don’t recommend fluid-air exchange — even just a partial exchange — for iris- or scleral-fixation of intraocular lenses (IOLs) or when implanting an anterior chamber IOL. Fixating the IOL may take some time, and placement may appear acceptable until you inject air and the IOL moves or the anterior chamber flattens. If you’re not sure about your sclerotomies, I recommend placing transconjunctival sutures.

IMPAIRED VISIBILITY

For a dropped or subluxated IOL and retinal detachment, fluid-air exchange is usually necessary unless perfluorocarbon liquid (PFCL)-oil exchange is performed. In this situation, or simply in pseudophakic eyes with posterior capsulotomy, IOL condensation may significantly impair visibility. Coating the posterior surface of the IOL with a dispersive viscoelastic substance is the most efficient way to resolve this problem, although you can start by aiming the infusion line on air toward the IOL. Sometimes this maneuver works (and it is less costly), but often it does not.

The most inconvenient episodes of decreased visibility during fluid-air exchange occur when PFCL droplets are left behind. If all of your attempts to manage IOL condensation are ineffective, consider reverting to fluid, removing residual PFCL and draining subretinal fluid through the retinal breaks, tilting the eye toward the breaks. If residual fluid accumulates posteriorly, place the patient face down to decrease the risk of postoperative retinal folds.

FLAT ANTERIOR CHAMBER

If the anterior chamber flattens after fluid-air exchange, I avoid placing viscoelastic in it. Although intraocular pressure usually doesn’t rise significantly, when it does, a substantial spike can occur, especially with a gas tamponade, and you will need to remove the viscoelastic postoperatively, risking optic disc damage and even artery occlusion.

For a flat anterior chamber, try reforming with acetylcholine chloride intraocular solution (Miochol-E; Bausch + Lomb) (closing the pupil will also help keep the IOL in place), balanced salt solution or filtered air. Surgical pearl: Regardless of what you choose to inject into the anterior chamber, do so with a 30-gauge needle, decreased air infusion pressure (20 mmHg) and one small-gauge cannula open. If you used a valved cannula, either remove the valve or simply “eat” it with the vitrector.

CHOROIDECTOMY CONSIDERATIONS

When performing a choroidectomy or in cases with an open globe injury, a very slow fluid-air exchange with low infusion pressure is required. In addition, make sure arterial blood pressure isn’t too low (less than 100 x 70 mmHg). Although extremely rare, venous and pulmonary air embolisms have occurred in these instances.^1,2

Also, make sure the infusion line is properly placed in the vitreous cavity to avoid inadvertent suprachoroidal air infusion. Air in the suprachoroidal space increases the risk of presumed air by vitrectomy embolization (PAVE).³ If a patient becomes agitated or if vital signs change during fluid-air exchange despite your precautions, immediately revert to fluid.

BE PREPARED FOR TOUGH CASES

Remember, you can’t rely on removing vitreous floaters to build up your practice. Take on the tough cases now, so you’ll be ready whenever one hits. Scrub in! NRP

REFERENCES