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Ординатура / Офтальмология / Учебные материалы / Vitreoretinal Surgery Farenc Kuhn Springer.pdf
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192

21 Sclerotomies and the Cannulas

 

 

Pearl

A narrow palpebral opening often causes an intraoperative problem too. As the eye is rotated, the lower lid can crimp the infusion line. You do not see this in the dark; only note that during vitreous removal, the eye collapses (you suspect the infusion bottle is empty). This may not be preventable since the eye must be rotated; simply stop and wait until the IOP normalizes.

21.6Checking the (Infusion) Cannula

The consequences of suprachoroidal (occasionally even subretinal) infusion can range from the inconvenient to the extremely serious.

Q&A

Q Can the VR surgeon actually kill his patient during surgery?

AYes. If F-A-X is performed and the infusion cannula is in the suprachoroidal space, the air can enter the bloodstream by tearing the choroid from the vortex vein ampullae. The air embolus will stop the heart.

21.6.1 Cannula Under the Choroid/Retina: Prevention

Even if it is “only” BSS that infuses the suprachoroidal space, it can rapidly lead to a choroidal detachment. To prevent this complication, the surgeon should do the following:

Before the infusion is opened, the tip of the cannula must be checked.

A brief peek does not suffice. The choroid and ciliary epithelium may be depigmented19; the quick peek will not allow the surgeon to detect that something is covering the tip of the cannula.

Even an initially properly placed infusion cannula may be but pulled out intraoperatively. It is easy to detect if the line is completely out but more difficult if only partially so.

Periodically check the position of the infusion cannula’s external position (i.e., is it pushed into the cannula all the way?) during surgery, but especially during scleral indentation and before switching to air.

19 Or appear to be so, due to tissue stretching.

21.6 Checking the (Infusion) Cannula

193

 

 

The position of the working-sclerotomy cannulas should also be checked. These do not represent the same danger, but iatrogenic damage can still be caused if they are partially out.

21.6.2 Cannula Under the Choroid/Retina: Management

If during the initial cannula insertion the tip of the cannula cannot be advanced all the way through the tissue, there are several options.

Push a needle through the cannula itself; this will create a small opening in the choroid, which may slide back.

If this does not work,20 introduce another cannula, insert a needle21 through that one, indent the sclera by pushing the first cannula in, and slice open the tissue around it so that you have a clear view of the tip. Once you created an opening, push the infusion cannula through it and then open the infusion and only then let the cannula, slowly, back into its normal position.

21.6.3 Infusion Going Under the Choroid/Retina: Management

If fluid did get under the choroid, the following usually restores the normal anatomy:

Close the infusion immediately.

Pull out the infusion line.

Put the infusion line through another cannula – and check its position before opening it.

Drain the suprachoroidal fluid through the infusion cannula.

If no fluid is coming or not all fluid has drained, pull out the cannula and enlarge the sclerotomy. Once the fluid has been drained, suture this sclerotomy and reinsert the infusion cannula at a different location.

Q&A

Q Is it possible to drain suprachoroidal fluid internally?

AIn principle, yes; in reality, it is very difficult. The choroid shrinks when diathermized (see Sect. 59.2). If the pressure in the suprachoroidal space is high and the fluid not viscous (BSS, not blood), a simple needle/blade puncture may work.

20It may not since the choroid is elastic, and the opening may immediately close.

21Bleeding is extremely rare from this. Do not use diathermy because it may shrink the tissue.

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