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.2,9,12 Studies of the in vitro metabolism of brain tissue4,7 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 0.9 per cent NaCl) while others use other “Ringer” solutions of varying composition.
Hartmann10 (see also Sachs18) has described a solution resembling spinal fluid particularly in its content of bicarbonate, but this was apparently used only for filling the ventricles of hydrocephalic infants after drainage for electrocoagulation of the choroid lexus. In spinal fluid, and in all other body fluids, the concentration of the bicarbonate ion is exceeded only by those of sodium and chloride; it constitutes about 15 per cent of the total anionic concentration. Besides serving as the main physiological buffer it is concerned in other biochemical mechanisms. Any solution that lacks this ion is therefore highly unphysiological.
In the present communication the preparation and dispensation of sterile fluids closely resembling cerebrospinal fluid are described, general methods for the study of the effects of various fluids are outlined, and studies of the reaction of the cortex to the pH of irrigating solutions are reported. Studies on the effects of different irrigation fluids on the electrical activity of the cortex, the response to cortical stimulation, the development of edema, and the formation of adhesions and other aspects of the problem are in progress.
Dusser de BarenneJ. G.MarshallC. S.MccullochW. S.NimsL. F. Observations on the pH of the arterial blood, the pH and the electrical activity of the cerebral cortex. Amer. J. Physiol.1938124: 631–636.Dusser de BarenneMarshallMcCullochNimsAmer. J. Physiol.124: 631–636.
Some of our neurosurgical colleagues call this “artificial spinal fluid.”
This addition is best made by means of a sterile syringe with a thin glass tube, instead of a needle, attached by rubber tubing. In view of the strong buffering capacity of the bicarbonate, exact measurement of the acid solution is not critical.
The strong pink color of the alkaline salt solution makes it unlikely that un-neutralized fluid would ever be used by mistake.
This apparatus was designed and built with the able assistance of Mr. L. Geddes.
It was interesting to observe that, on asphyxiating the animal by constriction of the trachea, the pH of the cortex fell rapidly, reaching 5.9 in 20 minutes. Blood drawn from the heart of the animal killed in this manner had a pH of 6.8. The rapid fall in pH of the brain is presumably mainly due to anaerobic glycolysis (lactic acid production) at the expense of glucose remaining in the brain.