Experimental Encephalography with Anesthetic Gases. ∗

Abstract

Dogs prepared by previously performed lumbar laminectomies were found, most suitable for experimental encephalography studies. Intravenous sodium amytal was given in sufficient amount to quiet the animal so that it could be handled and X-rayed easily, but not in high enough dosage to obscure painful or possible deeper narcotic effects of the anesthetic gases used for encephalographic injection. A lateral skull plate was first obtained. Then the dog was strapped on its side to a special table, the head end of which could be tilted to a 42° angle and which in all positions allowed maximum opportunity both to manipulate and observe the animal's reactions. Next with aseptic technique and local anesthesia a lumbar puncture was performed. The table was elevated and intermittently between collections of spinal fluid the gas to be tested was injected slowly by syringe into the subarachnoid spaces. Rotation of the head aided drainage. A 3-way petcock attached to the injecting syringe and connected by tubing to the controlling valve of the gas tank afforded a simple and convenient closed system for handling the gases. Replacement of the spinal fluid by the gas was carried as far as possible—usually until bubbles returned through the needle. Then the needle was withdrawn and another lateral skull plate was taken. If the ventricular outline appeared, other views were taken to follow the course of the injection. Throughout the entire procedure, pulse, respiration, color, reflexes, tonus, etc., were observed closely and recorded. Repeated encephalograms were obtained on the same animal to compare under as nearly identical conditions as possible the effects of the various gases. Air injections were initially performed in all cases as a standard by which the results obtained with the anesthetic gases could be compared.