prone positioning and pt. blindness

[EmeraldNYL, BSN, RN]

Today we were doing a repair of a popliteal aneurysm on an elderly gentleman with a cardiac history. He needed to be placed prone for the procedure, and we were having trouble keeping an adequate BP. Pre-op his BP was in the 130's/90's, and intraop his systolic kept dipping down into the 90's, despite repeated doses of neo and ephedrine. Anyway, we ended up doing a Neo drip. The MDA in this case was especially concerned about keeping the BP up d/t the prone positioning, citing risk of blindness as a reason. He was even so concerned as to put this risk on the patient's consent for surgery. My question is, why does prone positioning increase the risk of blindness? Is it because placing the patient prone increases intraocular pressure and therefore decreases perfusion even further if you don't have an adequate BP? I'm still a newbie so I haven't seen too many prone cases.

[Pete495]

here's some info. off a site I saw recently:

The eyes are also susceptible to injury if operating room staff do not take precautions. Anesthetized patients' eyelids should be taped shut to avoid being scratched by overhanging equipment and surgical drapes. Head positioning is also important; in the prone position, pressure on the eyes from headrests can cause thrombosis of the central retinal artery, even leading to permanent blindness. The chance of thrombosis is increased during anesthetic hypotension (accidental or deliberate), and the anesthesiologist should ensure that no external pressure is exerted on the eyes during the procedure.

Here's a good article off of Medscape, which you hopefully belong to. Read the Discussion part. It is pretty informative. This type of injury is rather rare, but nevertheless possible:

The Incidence of Vision Loss due to Perioperative Ischemic Optic Neuropathy Associated With Spine Surgery

The Johns Hopkins Hospital Experience

Shu-Hong Chang, MD; Neil R. Miller, MD

http://www.medscape.com/viewarticle/506675

[nilepoc]

What Pete said. I have heard that the MAP should be maintained altleast greater than 60, and preferably greater than 70. Personally, I use goggles, and a foam head block on all of my prone patients.

Craig

[rn29306]

One of our spine docs likes to angle the bed with head down and feet up while prone and I'm not talking about a little positioning either. This adds further pressure to the eyes than just regular prone position. I shoot for a MAP of 70, with whatever pharmacologic agent has best risk/benefit. MDA thought I was nuts until I told him my reasoning and then was cool with it.

At our hospital, seniors are treated as staff but most times, whenever a prone case comes up, a CRNA is attached to the case, regardless of age, just for the specific risk of blindness.

[jwk]

There are a lot of theories about blindness after surgery in the prone position (pressure on the eyes, low BP, etc.) but there don't appear to be enough common denominators in the cases that have been studied to point to any single cause or group of causes. It's a pretty rare complication, and the numbers aren't there to do an adequate analysis.

I think keeping pressure off the eyes and avoiding hypotension are the two biggies and also the most common sense approach, but there are reported cases where there was no hypotension noted and no pressure on the eyes.

Just a personal opinion about the goggles - I assume you're talking about the kind that stick-on to the patient. I don't like 'em. I've seen at least one patient where the plastic had gotten depressed, formed a permanent fold, and pressed against the patent's closed eye. Fortunately we noticed this prior to the start of the procedure.

For prone cases, I'd rather use a good foam headrest with adequate eye cutouts (checked frequently during the case). I've also seen them used during sitting/semi-sitting position cases like shoulder scopes. For those, I'd rather use some foam over the entire upper face (C-foams), and for all cases, remind the idiot surgeon/resident/assistant that it's the patients face, not a table, that they're resting their arm on.

[piper77]

Emerald, I would guess that the anesthesiologist was concerned about ischemic optic neuropathy secondary to hypotension; prone positioning has been widely implicated. Short prone cases (a couple of hours or less) are of less concern. ION is well reported; a good literature search can give you more info than you need. Good luck!

[yoga crna]

I think the issue is retinal artery flow and perfusion, but I am not sure why it is more common in the prone position. I do know there have been several malpractice suits on this issue and believe they have been reported on the ASA Closed Claims reports. A new student should know how to research this in the literature. Hint--Medline search.

Yoga