BLOOD PRESSURE RESPONSES IN ACUTE COMPRESSION OF THE SPINAL CORD.

Thirty-six adult cats were studied. Two monkeys were also used to determine whether significant variations of species were present. Pentobarbital sodium (30 mg./kg.) was administered intraperitoneally and supplemented as required, and an endotracheal or tracheostomy tube was inserted. A catheter was placed in the abdominal aorta via the femoral artery and connected to a Statham strain gauge and in turn to an amplifier and pen-writing system. Laminectomies of varying lengths were performed at all levels. A slender, elongated latex balloon was introduced into the epidural space, covering a longitudinal extent of one or occasionally two or three segments; one or more laminae were left intact at the level where compression was to be applied, to afford counter resistance. The balloon was inflated by a syringe connected to a mercury manometer. Compression of the cord was obtained by raising the pressure in the balloon to levels of 50: 100, `200, and `250 mm. of mercury for periods ranging from 5 to `25 sec. and on occasion up to '2 rain. The responsiveness of the cord at different levels was studied. Various procedures were carried out to try to determine the factors responsible for the pressor activity and the role of certain vasomotor reflexes in this response. These included bilateral denervation of the carotid sinus and aortic nerves, bilateral division of the vagus nerve high in the neck, bilateral (chronic) division of the dorsal roots at T1 to T3, bilateral adrenalectomy, decerebration at the level of the superior colliculus performed under ether anesthesia (following which anesthesia was discontinued), transection of the cord rostral to the area to be compressed, and perfusion of upper