Anesthesia Student Survival Guide.pdf - Index of

PhysioloGy And AnesthesiA for neuroloGic, ent, And oPhthAlmoloGic surGery ● 297
Airway Surgery
Surgery to diagnose and treat airway disease (vocal cord polyp, oral cancer,
laryngeal mass) is a mainstay of ENT practice. These patients tend to have
multiple medical conditions, have a long history of smoking or heavy alcohol
consumption, and the potential for a difficult airway. Airway fire is a potential
intraoperative complication. Postoperative intubation and ventilation may be
considered in patients with significant residual airway disease, or procedures
in which significant surgery involving the airway may predispose to swelling,
recurrent laryngeal nerve injury, or bleeding with concomitant airway compromise.
Ophthalmology
The majority of ophthalmologic procedures are done on an outpatient, elective
basis. However, the patient population varies widely from healthy children having
strabismus surgery to sick, elderly patients presenting for cataract surgery.
Procedures generally require a cooperative patient and an immobile globe.
Intraocular pressure (IOP) is akin to ICP and is a primary physiologic
consideration in ophthalmologic surgery. It is particularly important in direct
injury to the globe and glaucoma, and IOP may be increased by severe hypertension,
valsalva, coughing, hypercapnia, succinylcholine-induced fasciculations,
and injection of fluid/anesthetic into the orbit.
Procedures such as Lasik ® and cataract surgery are conducted with sedation
accompanied by local infiltration or eye block. Others, including vitrectomy
and strabismus repair usually require general anesthesia. Sometimes choice of
anesthetic is influenced by co-existing conditions, such as inability to lay flat
or remain still. For the sedation technique, a bolus of a hypnotic agent such
as propofol, etomidate, or ketamine will facilitate block and injection of local
anesthetic. Following the injection, anesthetic requirements are minimal. The
head of the patient is usually fully covered and inaccessible once surgery has
commenced under the operating microscope. A nasal cannula with capnographic
monitoring capability is used.
Many ophthalmologists are accustomed to placing an eye block (retrobulbar,
peribulbar, Sub-Tenon’s injection).
For the retrobulbar block (Fig. 18.2), a 25G sharp needle (25 mm
length) is used to inject several milliliters of a mixture of bupivacaine 0.5%
with lidocaine 2% and hyaluronidase to facilitate diffusion and penetration.