Gas-forced infusion: A solution for surge

An air pump helps to prevent posterior capsular rupture in bimanual surgery.

Issue: September 1, 2006

ByAmar Agarwal, MS, FRCS, FRCOphth

The main problem we originally had in bimanual phaco/phakonit was the destabilization of the anterior chamber during surgery. We solved it to a certain extent by using an 18-gauge irrigating chopper. Then Sunita Agarwal, MD, suggested the use of an air pump, which injects air into the infusion bottle (Figure 1). This pushes more fluid into the eye through the irrigating chopper and also prevents surge. Thus, we were able to use a 20-gauge or 21-gauge irrigating chopper, as well as solve the problem of destabilization of the anterior chamber during surgery. Now with microphakonit, because of gas forced infusion, we are able to remove cataracts with a 0.7-mm irrigating chopper. Subsequently we use this system in all our coaxial phaco cases to prevent complications like posterior capsular ruptures and corneal damage.

Surge

Amar Agarwal

A well-maintained anterior chamber without intraocular fluctuations is one of the prerequisites for safe phacoemulsification and phakonit. When an occluded fragment is held by high vacuum and then abruptly aspirated, fluid rushes into the phaco tip to equilibrate the built up vacuum in the aspiration line, causing surge. This leads to shallowing or collapse of the anterior chamber. Different machines employ a variety of methods to combat surge. These include usage of noncompliant tubing, small bore aspiration line tubing, microflow tips, aspiration bypass systems, dual linear foot pedal control and incorporation of sophisticated microprocessors to sense the anterior chamber pressure fluctuations.

The surgeon dependent variables to counteract surge include good wound construction with minimal leakage and selection of appropriate machine parameters depending on the stage of the surgery. An anterior chamber maintainer has also been described by Michael Blumenthal, MD, to prevent surge.

Diagrammatic representation of the connection of the air pump to the infusion bottle.

Images: Agarwal A

Air pump

A simple and effective method to prevent anterior chamber collapse during phacoemulsification and phakonit is by increasing the velocity of the fluid inflow into the anterior chamber. This is achieved by an automated air pump, which pumps atmospheric air through an air filter into the infusion bottle, thereby preventing surge. This can be used with any phacoemulsifier to minimize surge. This air pump is an automated device, used in aquariums to supply oxygen and is utilized to forcefully pump air into the irrigation bottle. This pump is readily available in aquarium shops. A micropore air filter is used between the air pump and the infusion bottle so that the air pumped into the bottle is clean of particulate matter.

An IV set connects the air pump to the needle, which is normally fixed for air in the infusion bottle. When the air pump is switched on, it pumps air into the infusion bottle. This air goes to the top of the bottle and because of the pressure, it pumps the fluid down with greater force. With this, the fluid now flows from the infusion bottle to reach the phaco handpiece or irrigating chopper (Figure 2). The amount of fluid coming out is much more than what would normally come out and with more force. An air filter is connected between the air pump and the infusion bottle so that the air, which is being pumped into the bottle, is sterile. This extra amount of fluid coming out compensates for the surge that would otherwise occur.

Continuous infusion

Before we enter the eye, we fill the eye with viscoelastic. Then, once the tip of the phaco handpiece for phaco or irrigating chopper for phakonit is inside the anterior chamber, we shift to continuous irrigation. This is very helpful especially for surgeons who are starting phaco or phakonit. This way, the surgeon never comes to position zero and the anterior chamber never collapses. This is helpful, even for experienced surgeons.

Advantages

There are several advantages to using this pump:

With the air pump, the posterior capsule is pushed back and there is a deep anterior chamber.
The phenomenon of surge is neutralized. This prevents posterior capsular rupture.
Striate keratitis post-operatively is reduced, as there is a deep anterior chamber.
One can operate hard cataracts (Figure 3) also quite comfortably, as striate keratitis does not occur post-operatively.
The surgical time is shorter as one can emulsify the nuclear pieces much faster as surge does not occur.
One can easily operate microphakonit with the 700 micron cataract surgical system (MST) (Figure 4).

Flow of fluid through the irrigating chopper with an air pump. When the air pump is on, the amount of fluid coming out of the irrigating chopper is much more than what would normally come out and with more force.

Phakonit being performed in a mature brown cataract. Such difficult cases can be operated upon by phakonit because of the air pump. It deepens the chamber and prevents any surge.

Microphakonit – 700 µm cataract surgery (MST, USA). Note the nucleus has been removed using this system.

Topical or no anesthesia cataract surgery

When one operates under topical or no anesthesia, the main problem is sometimes the pressure is high especially if the patient squeezes the eye. In such cases, the posterior capsule comes up anteriorly and one can produce a posterior capsular rupture. To solve this problem, the surgeon tends to work more anteriorly, performing supracapsular phacoemulsification. The disadvantage of this is that striate keratitis tends to occur.

With the air pump, this problem does not occur. When we use the air pump, the posterior capsule is quite posterior, as if we are operating a patient under a block. In other words, there is a lot of space between the posterior capsule and the cornea, preventing striate keratitis and inadvertent posterior capsular rupture.

Internal gas forced infusion

Arturo Pérez-Arteaga from Mexico started using internal gas forced infusion in for phakonit. The anterior vented gas forced infusion system of the Alcon Accurus surgical system can be used. This is a system incorporated in the Accurus machine that creates a positive infusion pressure inside the eye. One can also use the Bausch & Lomb Millennium.

For more information:

Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Group of Eye Hospitals. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; e-mail: dragarwal@vsnl.com; Web site: www.dragarwal.com.

References:

Agarwal A, Handbook of Ophthalmology. Thorofare, NJ: SLACK Incorporated; 2005.

Agarwal A. Phaco Nightmares: Conquering Cataract Catastrophes. Thorofare, NJ: SLACK Incorporated; 2006.

Agarwal S, Agarwal A, Agarwal A. Phacoemulsification. 3rd ed. Thorofare, NJ: SLACK Incorporated; 2004.