Watching the needle beats marking the spot at lower thoracic epidural puncture

Design

Randomised controlled trial, single centre

Population

64 patients undergoing abdominal surgery requiring lower thoracic epidural anaesthesia

Primary outcome

First-pass success rate at epidural puncture

Effect

81 per cent (26/32) with real-time guidance vs 47 per cent (15/32) with pre-procedural scanning (P = 0.008); fewer passes and punctures; procedure time unchanged

Sixty-four patients scheduled for abdominal surgery requiring thoracic epidural anaesthesia were randomised to real-time in-plane ultrasound guidance throughout needle advancement, or to a pre-procedural scan that identified and marked the target level before insertion. Both groups had the preliminary scan; the difference was whether the probe stayed on the back.

First-pass success was 26 of 32 (81 per cent) with real-time guidance against 15 of 32 (47 per cent) with pre-procedural scanning alone (P = 0.008). Fewer passes and fewer punctures were needed in the real-time group. Procedure time did not differ, which is the finding that removes the usual objection.

Two caveats before adopting it. Sixty-four patients is small, and a first-pass success rate of 47 per cent in the comparator arm is lower than many operators would expect from marking alone, which suggests either a difficult population or a technique-dependent result. And real-time in-plane guidance at the thoracic level is a genuinely harder skill than marking a level, requiring a second operator or a well-practised one-handed technique. The finding is worth acting on where that skill exists or can be built; it is not a reason to attempt an unfamiliar technique on a difficult back.

• Keep the probe on during needle advancement rather than only marking the level, where the skill exists.
• Do not expect it to take longer; procedure time was unchanged.
• Note the small sample and the low comparator success rate before quoting the 81 per cent figure.
• Plan for a second pair of hands, or practise the one-handed technique, before attempting it in theatre.
• The preliminary scan was done in both arms and remains worthwhile regardless.

The statistics, in plain English

A difference of 34 percentage points in 64 patients gives P = 0.008, so the effect is unlikely to be chance, but with 32 patients per arm the confidence interval around it is wide and the true difference could be considerably smaller. Single-centre procedural trials also carry an operator effect that no randomisation removes: the result describes what these operators achieved with these techniques. Fewer passes and punctures are consistent secondary findings, which strengthens the primary result.

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