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KEY CONCEPTS
Any factor that increases intraocular pressure in the setting of an open globe may cause drainage of aqueous or extrusion of vitreous through the wound, serious complications that can permanently worsen vision.
Succinylcholine increases intraocular pressure by 5 to 10 mm Hg for 5 to 10 min after administration, principally through prolonged contracture of the extraocular muscles. However, in studies of hundreds of patients with open eye injuries, no patient experienced extrusion of ocular contents after administration of succinylcholine. Thus, succinylcholine is not contraindicated in cases of open eye injuries.
Traction on extraocular muscles, pressure on the eyeball, administration of a retrobulbar block, and trauma to the eye can elicit a wide variety of cardiac arrhythmias ranging from bradycardia and ventricular ectopy to sinus arrest or ventricular fibrillation.
Complications involving the intraocular expansion of gas bubbles injected by the ophthalmologist can be avoided by discontinuing nitrous oxide at least 15 min prior to the injection of air or sulfur hexafluoride, or by avoiding the use of nitrous oxide entirely.
Medications applied topically to mucosa are absorbed systemically at a rate intermediate between absorption following intravenous and subcutaneous injection.
Echothiophate is an irreversible cholinesterase inhibitor used in the treatment of glaucoma. Topical application leads to systemic absorption and an inhibition of plasma cholinesterase activity. Because succinylcholine is metabolized by this enzyme, echothiophate will prolong its duration of action.
The key to inducing anesthesia in a patient with an open eye injury is controlling intraocular pressure with a smooth induction. Coughing and gagging during intubation is avoided by first achieving a deep level of anesthesia and profound paralysis.
The postretrobulbar block apnea syndrome is probably due to injection of local anesthetic into the optic nerve sheath, with spread into the cerebrospinal fluid.
Regardless of the anesthetic technique, American Society of Anesthesiologists standards for basic monitoring must be employed, and equipment and drugs necessary for airway management and resuscitation must be immediately available.
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Ophthalmic surgery poses unique problems, including regulation of intraocular pressure, control of intraocular gas expansion, prevention of the oculocardiac reflex and management of its consequences, and management of systemic effects of ophthalmic drugs. Mastery of general and sedation anesthesia techniques for ophthalmic surgery and a thorough understanding of potentially complicating issues—including the comorbidities of an increasing geriatric patient population—are necessary for optimal perioperative outcomes. In addition, the majority of ophthalmic procedures are performed under topical or regional anesthesia. The anesthesiologist must be familiar with their potential complications, including those of the accompanying sedation, even if not personally administering the topical anesthetic or the block.
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INTRAOCULAR PRESSURE DYNAMICS
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Physiology of Intraocular Pressure
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The eye can be considered a hollow sphere with a rigid wall. If the contents of the sphere increase, the normal intraocular pressure of 12 to 20 mm Hg will rise. For example, glaucoma is caused by an obstruction to aqueous humor outflow. Similarly, ...