Deep neuromuscular block cut three-month chronic pain after lumbar fusion

Design

Randomised controlled trial

Population

178 adults having posterior lumbar interbody fusion

Primary outcome

Chronic postsurgical pain at 3 months

Effect

19.1% vs 34.8%; RR 0.6 (95% CI 0.3 to 0.9)

This randomised trial in China allocated 180 adults having posterior lumbar interbody fusion to deep or moderate neuromuscular block; 178 were analysed. The hypothesis was that deeper relaxation reduces retraction injury to the paraspinal muscles.

Chronic postsurgical pain at three months, the primary outcome, was 19.1% with deep block versus 34.8% with moderate block (RR 0.6, 95% CI 0.3 to 0.9). At six months the difference was smaller and not significant (14.6% vs 19.1%; RR 0.8, 0.4 to 1.5). Deep block was associated with lower early pain scores, less opioid use, higher surgeon satisfaction, lower creatine kinase, myoglobin and LDH on day 1, and better preserved paraspinal muscle on MRI at six months.

The mechanism is plausible and the biomarker and imaging findings point the same way. But the three-month benefit faded by six months, the trial is single-country, and deep block requires reliable reversal and quantitative monitoring. It is a reason to discuss block depth with spinal surgeons, not yet a standard.

• Consider deep neuromuscular block for posterior lumbar fusion where surgeons use extensive muscle retraction.
• Use quantitative neuromuscular monitoring throughout when maintaining deep block.
• Plan full reversal and confirm a train-of-four ratio of at least 0.9 before extubation.
• Expect less early opioid use; the chronic pain benefit may not persist beyond three months.

Why it matters

Block depth is usually chosen for surgical access, and this suggests it may also influence muscle injury and pain afterwards.

Don't overread it

The primary benefit was at three months only; the six-month result did not reach significance.

The statistics, in plain English

An RR of 0.6 at three months means about 40% fewer patients with chronic pain, an absolute drop of about 16 percentage points. The six-month interval crosses 1, so the trial cannot say whether any benefit lasts. With fewer than 90 patients per arm, the size of the effect is uncertain.

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