202410102252
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Tags: Neuraxial block
Inadvertent dural puncture
the impact of intrathecal catheters on the incidence of postdural puncture headache (PDPH) and the requirement for an epidural blood patch when compared with subsequent epidural catheter insertion, continue to be debated
A greater degree of cervical dilatation and operator inexperience increases the risk of inadvertent dural puncture
Several techniques to distinguish CSF from saline have been suggested, including:
- testing for protein or glucose,
- temperature,
- pH
- changes in turbidity when mixed with thiopental
It has been estimated that around a third of inadvertent dural punctures are unrecognised
The Royal College of Anaesthetists' 7th National Audit Project investigating peri-operative cardiac arrest suggested that a test dose of 10 mg bupivacaine (or equivalent) allows recognition of an intrathecal catheter while minimising the risk of high- or total-spinal anaesthesia. This dose should produce clinically evident sensory, motor or autonomic effects.
For labour epidural analgesia, to minimise the risk of high- or total-spinal anaesthesia, a test dose of local anaesthetic solution should not exceed the equivalent of 10 mg bupivacaine
The ideal length of catheter insertion is not known, although most publications report advancement of 2–4 cm into the subarachnoid space
For initiation of labour analgesia via an intrathecal catheter, an initial bolus of 2.5 mg bupivacaine (or equivalent) may be used, with the addition of up to 15 μg fentanyl (or equivalent)
For maintenance of labour analgesia via an intrathecal catheter, bupivacaine 0.1–0.125% (or equivalent) with 2–2.5 μg.ml-1 fentanyl (or equivalent) are suitable solutions
Low-dose local anaesthetic solutions for maintenance of labour analgesia via an intrathecal catheter may be given either as intermittent boluses (up to 2.5 mg) by an anaesthetist, or as a continuous infusion (1–3 ml.h-1)