Chapter 30
Anesthetic Considerations for Ocular Disease
An eye for the details
Lesley J. Smith
Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, USA
- Q. What are some common reasons that animals present needing ocular surgery?
- A. Common reasons that dogs and cats present for ocular surgery include trauma, corneal ulcers, glaucoma or orbital cancer, cataracts (dogs), eyelid masses, entropion, and ectopic cilia. Depending on the disease state, the patient may be geriatric or quite young and healthy. Dogs with cataracts maybe be young with congenital cataracts or older with acquired cataracts due to diabetes or age. The underlying health status of the patient will largely dictate most details of its anesthetic management.
- Q. What are some common themes to be aware of when planning anesthesia for patients needing surgery of the eye?
- A. Some common themes will be dependent on the underlying ocular condition, but general considerations are to avoid struggling at induction and/or aggressive restraint during premedication or catheter placement, as these will increase intraocular pressure. Similarly, you want recovery to be smooth, with no thrashing or self-induced trauma to the post-operative eye. If surgical manipulation is likely to put pressure on the globe, then the anesthetist should be aware of the possibility of an oculocardiac reflex, i.e., increased vagal tone, and a sudden drop in heart rate. This usually resolves quickly with an IV dose of atropine or glycopyrrolate. In cases where an increase in intraocular pressure can be devastating (e.g., a descemetocele, deep corneal ulcer, corneal laceration), try to avoid drugs that can induce vomiting such as IM administration of pure μ agonist opioids. Some patients presenting for ocular surgery are geriatric, so underlying disease associated with old age should be considered and screened for. Acquired cataracts are often the result of chronic diabetes, so these patients require careful monitoring of blood glucose levels and judicious administration of insulin. Chapter 37 provides detailed discussion of the anesthetic management for diabetic patients.
- Q. Are there any concerns with positioning for eye surgery?
- A. Often, for ideal placement of the eye for surgery, the patient is positioned in dorsal recumbency with “chin on chest.” Standard commercially available endotracheal tubes can kink inside the trachea in this position. The anesthetist may notice a sudden decrease in chest compliance, or elevations in end-tidal CO2 or decreases in SpO2. The resultant hypoxia or hypercapnia can be severe and life-threatening! To avoid this complication, intubate the patient at induction with a reinforced or “guarded” tube. These are commercially available and have a wire reinforced wall that prevents the tube from kinking even when bent to > 120o
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- Q. Are there any concerns with positioning for eye surgery?
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