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SUMMARY A method of local cerebral hypothermia with circulatory arrest of one or more of the major vessels of the neck is described. Ten clinical cases have been operated upon, and much has been learned of the operative difficulties including an increased operating time and a high complication rate. There were four post-operative deaths, in one (case 1) there was some evidence that the technique protected the perfused part of the brain from anoxic damage. In case 9 the method itself caused particularly bad operating conditions and eventually the patient died. Case 2 and case 4, like case 1, were patients who were severely ill and who might well have died whatever technique had been used in operating upon them. Of the survivors, one patient (case 3) had a post-operative intracerebral clot which developed during closure and another (case 6) had an intracerebral clot which required removal after 24 hours. Another patient (case 8) had some delay in return to full mental function. In the light of this experience we cannot regard the method in its present form as satisfactory for general use. In our view, its further development requires the discovery of a more effective means of neutralizing the anticoagulants, or doing without anticoagulants altogether. It is also necessary to develop a method of monitoring parts of the brain distant from those directly perfused to give warning of threatened anoxia. Until such time as these problems can be solved we have returned to other procedures but are publishing our results in the hope that other workers will be able to improve upon them.Since the work of Drew (1959), neurological surgeons have been interested in using the ability of the brain to withstand complete circulatory arrest for over 30 minutes at temperatures of the order of 15°C, on the basis that the difficult aneurysm or arteriovenous malformation might be easier to treat under such conditions.From the beginning it seemed probable that the full Drew technique might be too much for a patient who had sustained one or more recent subarachnoid haemorrhages. Despite the difficulties, a large number of neurosurgical operations were carried out in the early 1960s and clinical reports came from

Large infusions of a 10% solution of dextran of molecular weight 40,000 were given to dogs during 3 min using a specially designed apparatus. The initial expansion of plasma volume was about twice the volume of solution injected. Plasma volume then fell rapidly (with a half life of about 2 hr), more rapidly than the fall in dextran concentration (half‐life of about 4.5 hr). Fluctuations in plasma volume and protein concentration were repeatedly observed during the return towards normal values. At 5 to 6 hr renal excretion accounted for 40% of the infused dextran, about 20% was intravascular and the remaining 40% was presumably extra vascular. No dextran was found in the cerebrospinal fluid.

Kimoto and Vishnevsky used the method for cardiac surgery and were not therefore concerned with carotid occlusion, Kristiansen normally stops his pump if necessary but does not occlude any other vessels. Gott has occluded the opposite carotid ,and lowered the systemic pressure to lessen bleeding through vertebral anastomoses. Connolly has occluded the vertebrals and the opposite carotid after the brain was cool to control bleeding for aneurysm surgery. The present work started with the intention of perfusing one carotid with cooled blood at a pressure above the mean systemie, and when the brain is cooler, taking advantage of the diminished oxygen requirements, and clamping the remaining vessels one by one. Cooling of the brain is thereby rendered more efficient and the maintainance of a temperature gradient between the heart and the brain made easier.This method is dangerous if the anastomosis is poor between the carotid and vertebral circulations. Slowing of flow from any cause is likely to be injurious since not only will the efficiency of cooling be lessened but capillaries will become blocked with "white emboti" and later with aggregates of blood cells. This phenomenon is increased by slow flow rates and in its turn must cause further diminution in flow, Anoxic damage may

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