Intrathecal catheters after dural puncture – some unanswered questions

Abstract

We read with interest the comprehensive survey carried out by Drs Baraz and Collis and congratulate the authors on the discipline to repeat the survey after 10 years to clearly demonstrate the change in practice over the years [1]. We agree that placement of an epidural catheter intrathecally has been shown to be a simple and effective alternative to re-siting an epidural following an accidental dural puncture during labour. This has the advantage of providing almost immediate analgesia and reduces the chances of a second dural puncture. A reduction in the need for subsequent epidural blood patch due to the inflammatory process around the catheter is an additional bonus. However, the incidence of post dural puncture headache is only reduced and not abolished after insertion of the spinal catheter [2]. A number of side-effects of intrathecal and epidural catheter placements have been reported and include cauda equina syndrome (as well as toxicity from hyperbaric local anaesthetic, another proposed mechanism is direct trauma by a looped epidural catheter) [3], infection, meningitis and breakage of the catheter (necessitating surgical extraction) [4]. Portex epidural catheters, which are widely used, have been shown in one study to have a higher incidence of paraesthesia and vessel damage [5]. Another issue is the propensity to misidentify the lumbar intervertebral space used to perform the spinal or epidural analgesia, even by experienced anaesthetists [6]. The spinal cord has been known to extend beyond the textbook level of the ‘lower border of L1 to upper border of L2’. The artery of Adamkiewicz also has enough variations in its anatomy to be affected by insertion of spinal catheter [7]. There is also an issue concerning consent. The Bolam vs. Friern case in 1957, later backed up by the Sidaway case in 1985, which was considered a standard to avoid liability in the event of a malpractice case, has been insidiously eroded through more recent court judgments such that it is no longer applicable. The Department of Health recognises the recent changes and comments that ‘judgment in a number of negligence cases have shown that courts are willing to be critical of a responsible body of medical opinion’[8]. These changes have great implications on how much information we impart to a reasonable patient to obtain an informed valid consent. Given all the above considerations, we invite comments and answers to the following questions. Is there a recommendation to only insert epidurals for labour analgesia at or below L2-L3? What information should be given to the patient to obtain informed consent for insertion of an intrathecal catheter in the event of an accidental dural puncture? Should we have guidelines on the quality and quantity of information which includes most (if not all) of the complications of insertion of an intrathecal catheter? Should the same principle of inserting spinal catheters be applied to dural punctures while attempting thoracic epidural analgesia? Assuming that the thoracic epidural was definitely indicated, would the risk of a spinal catheter causing nerve damage be justified, when the risk of postdural puncture headache (after inadvertent thoracic dural puncture) is not high? Finally, should we re-visit the recommendations to insert spinal catheters for accidental dural punctures, especially as the majority of the accidental dural punctures occur with inexperienced trainees, and out of normal working hours?