Spinal analgesic agents

Abstract

Spinal analgesia in the United Kingdom has depended for several years on the use of cinchocaine. When the availability of this drug became uncertain', it was clear that an alternative should be sought: ideally this alternative should be at least as effective as the well-known cinchocaine. Also, to avoid ditficulties which might be encountered by those using a simple and established technique, the behaviour of the preparations should be comparable. Consequently, and with the approval of the Committee on Safety of Drugs, a limited study of 5 % lignocaine with 7.5 % glucose was undertaken. This was used as if the agent under trial had been the familiar heavy cinchocaine. The results were both disappointing and, in a few instances, alarming. It appeared that the preparation, already widely accepted in many parts of the world, travelled through the cerebrospinal fluid with unexpected rapidity. Thus, not infrequently, there was an area of analgesia limited to the lower sacral roots following lumbar intrathecal injection with the patient sitting. On the other hand, a few instances of respiratory arrest followed the cephalad spread of the block when the injection was made with the patient in the lateral position. On reflection, it was realised that this had occurred only in obese women, who, when placed on their sides, had a distinct 'head-down' spinal slope2. It was assumed that the behaviour of the spinal analgesic solution could be explained by the relatively high specific gravity (1035 compared with 1024 of heavy cinchocaine). The purpose of this investigation was to study the behaviour and efficiency of three different preparations for spinal analgesia. METHODEven when a standard technique is followed, the results will be subject to variations in the response of the individual. It was therefore decided to administer spinal analgesia to patients likely to undergo several operative procedures of a similar nature and in whom this form of pain relief might be considered suitable. Each patient would thus provide her own control and the effects of the different agents could be compared.