The effect of anaesthesia on intraocular blood flow

Endotracheal intubation (placement of a catheter through the mouth into the windpipe to maintain an airway) is performed during administration of general anesthesia for surgery. Endotracheal intubation can increase intraocular pressure (IOP). Administration of suxamethonium, a skeletal muscle relaxant that may be used during anesthesia, also can increase IOP; however, the main increase in IOP occurs after endotracheal intubation. A study was undertaken to determine the effect of suxamethonium and endotracheal intubation on ocular blood flow, a possible cause of increased IOP. Pulsatile ocular blood flow, IOP, heart rate, and blood pressure were measured in two groups of 15 patients. One group received pretreatment with lignocaine (lidocaine hydrochloride, a local anesthetic); the other group received a placebo. The four measurements were obtained simultaneously four times during the first four minutes of general anesthesia. Following administration of suxamethonium, there was a significant increase in IOP, but no associated rise in ocular blood flow. The lignocaine group did not show reduction of either response. Following intubation, both IOP and ocular blood flow increased significantly, as did blood pressure and heart rate. These responses reflect response to the stress associated with intubation. (Consumer Summary produced by Reliance Medical Information, Inc.)