A comparison of cerebrospinal fluid pressure and block height after spinal anaesthesia in the right and left lateral position in pregnant women undergoing Caesarean section

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Background and objectiveLittle information exists on cerebrospinal fluid pressures in non-labouring pregnant women. The technique of spinal anaesthesia means that inadequate levels of sensory blockade are difficult to manage. If the block is found to be inadequate after surgery has commenced, then conversion to general anaesthesia may be the only option. It is important that any manoeuvre altering the spread of local anaesthetic is considered at the time of subarachnoid injection. This study investigates the feasibility of using a fine bore needle with an electronic transducer to measure cerebrospinal fluid pressure and whether this was affected by either of the two lateral positions. We also sought to measure whether the right or left lateral position affected subsequent block height and requirements for supplementary analgesia.MethodsTwo groups of 17 women presenting for elective Caesarean section were allocated to receive spinal anaesthesia in either the right or left lateral position. Cerebrospinal fluid pressure was measured by use of a rapid response electronic transducer connected to the hub of the spinal needle. Anaesthetic levels to cold sensation were assessed at 5, 10 and 15 min after injection of hyperbaric bupivacaine. During surgery, requirements for supplementary analgesia were recorded.ResultsThere was no significant difference in cerebrospinal fluid pressure between the two positions. While there was a trend towards more rapid analgesia in the right lateral group, this did not reach statistical significance. Two blocks performed in the left lateral group were inadequate for surgery but this was not statistically significant. Overall, 39% of women required supplementary analgesia during surgery. The incidence was not significantly different between the two groups.ConclusionAdoption of either the right or left lateral position for placement of spinal anaesthesia results in no difference in cerebrospinal fluid pressure or quality of block. The technique described gives a reliable and reproducible method of cerebrospinal fluid pressure measurement.

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