Physiological Salt Solutions for Brain Surgery

I T IS common experience that simple exposure of the pia-arachnoid surface of the cerebral cortex during prolonged neurosurgical procedures, such as for an exploratory craniotomy, results in the formation of adhesions between the dura and arachnoid. In certain cases there may be transitory aphasia or paresis during the first week following a simple exploratory procedure. These transitory postoperative complications are usually attributed to edema. This explanation has received support in the experiments of Prados, Strowger, and Feindel, ~5,16 who demonstrated that marked edema does develop following simple exposure of the cortex in cats and that it is associated with vasodilatation and an increase in permeability of the bloodbrain barrier. They found that this reaction of the brain to exposure could be prevented, at least in part, by hormones (desoxycorticosterone, adrenal cortical extract) which tend to counteract the increase in vascular permeability. The physical factors (temperature, mild trauma, air, light, drying, etc.) acting upon the exposed brain to produce these undesirable reactions have not received systematic study. One of these factors may be the composition of the irrigation fluid. The study of irrigation fluids for use on the exposed brain, which forms the subject of the present report, is a part of a series of investigations on the general problem of the reaction of the brain to exposure which is being carried out under the direction of Professor Wilder Penfield. The importance of the composition of salt solutions in experimental studies of the nervous system has long been recognized? ,9,12 Studies of the in vitro metabolism of brain tissue 4,7 have shown that it is sensitive to the composition of the medium in which the tissue is bathed. Much recent work has shown the dependence of the physical condition of biological materials, and the activity of many enzymes, upon the presence of various ions, often in low concentration. Little consideration has been given to the possible significance of these findings in the selection of solutions most suitable for use as irrigation fluids during operations on the brain or elsewhere or for replacing spinal fluid or filling cavities. There is little uniformity of practice among neurosurgeons with regard to the type of solution employed except that it is usually made isotonic with serum. Some use normal saline (0.85 or