IN 1967 HITCtICOCK proposed intrathecaI infusions of cold saline as a therapeutic method for relieving intractable pain. 1 Hitchcock's technique for preparing cold saline ensured that the solution was also appreciably hypertonic, and further work led to the view that success depends upon the hypertonicity of the solution injected, rather than on its temperature. 2,a Unfortunately, the presence of hypertonie saline in the delicate precincts of the subarachnoid space is an insult that produces some undesirable effects. First, severe pain and muscle cramps occur in the affected segments. 4 Second, a brisk sympathetic response causes arterial hypertension z,6 and occasionally cardiac arrhythmias2: even pulmonary oedema 7 and cerebral infarction ~ have been reported. Heavy sedation or general anaesthesia is commonly used to control these side effects during the period of intense stimulationJ ,s and Neilsen has used epidural analgesia to block sympathetic fibres2In this communication we show that simple and apparently safe control of the painful and potentially dangerous neural discharge can be achieved by using subarachnoid anaesthesia. We have observed the effects in man of intrathecal injections of limited volumes of strongly hypertonic saline, mixed with a weak concentration of a local anaesthetic agent. Serial measurements of cerebrospinal fluid osmolality were made to confirm that the technique produced a significant degree of hypertonicity.Experiments in dogs involving intrathccal injections of hypertonic saline with and without local anaesthetic are in progress, in an attempt to elucidate the serial changes which occur in arterial and cerebrospinal fluid pressures. M ETHODSTwenty millilitre vials of eight per cent sodium chloride in distilled water with 4 mg of lidocaine hydrochloride per millilitre, that is, 0.4 per cent, were prepared by the hospital pharmacy, and autoclaved prior to use. The calculated osmolality of the mixture was 2788 m.Osmols/Kg, and the measured osmolality was 2700-2900 m.Osmols/Kg, that is, approximately ten times the osmolality of normal cerebrospinal fluid. The specific gravity was 1.050 at 20~Observations were made of 14 subarachnoid injections in 9 patients suffering from intractable pain of the trunk and lower extremities. Subarachnoid puncture was made at an appropriate interspace using a 22-gauge spinal needle. The levc] of injection and the position of the patient were chosen to favour distribution of the hypertonic solution to the affected segments.Fifteen millilitres of cerebrospinal fluid were aspirated, and 15 ml of the hypertonic mixture were injected at room temperature, with the patient sitting

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