FROM 7 H t IIbPT. OE SURGICAL NEUROLOGY, ROYAL INFIRMARY, EVINBURGH.THE problem of bleeding during operations has long exercised the minds of surgeons. This problem has two aspects: first, the danger to life from loss of blood, and second, the inconvenience to the surgeon of a blood-obscured operation field. With the ready availability of stored blood, the first part of t4e problem is no longer so formidable. The second, that of bleeding in the field of operation, still awaits a satisfactory solution. In surgery of the brain, ease of access and the avoidance of surgical trauma depend considerably on a low intracranial tension, which, in turn, is dependent in marked degree upon arterial blood pressure.In neurosurgery the Halstead-Cushing operative technique, the use of suction and diathermy and of absorbable haemostatics partly meet the difficulties occasioned by bleeding in the operation field. Modern anaesthetic methods, too, influence the amount of operative bleeding and lower intracranial tension by preventing venous congestion of the brain. Nevertheless intracranial surgery is still considerably hampered and limited by operational blood loss, by obscuration of the field by blood and by inconveniently high intracranial pressure.In order to minimise blood loss in operations on particularly vascular cerebral tumours, Gardner introduced into clinical practice the method of "controlled induced hypotension by arteriotomy", and our experience with this method is the subject of the present paper.Briefly, the procedure is to bleed the patient from an artery into bottles containing an anti-coagulant, until the blood pressure is stabilised at a suitably low level, and subsequently to return the blood to the patient by the same route. The experimental basis on which this clinical practice is founded is that of Kohlstaedt and Page2 who used an arterial cannula to bleed animals for the purpose of studying shock, returning the blood through the same cannula. These workers found that it was possible to maintain a given level of circulatory hypotension by judicious small bleedings and re-infusions. They also found that, in animals which had been thus kept in extreme hypotension for periods up to 135 minutes, if the shed blood was returned by the arterial route, a more rapid and certain recovery ensued than in those treated by intravenous re-infusion.
ApparatusThe apparatus used is similar to that described by Hale3, and has proved satisfactory and reliable in use (see Fig.). It consists of a Y-shaped glass cannula which is introduced into the radial artery.
