Liposomal bupivacaine in knee-block analgesia: small gain, big price

Design

Single-centre, assessor-blinded randomised controlled trial

Population

60 total knee replacement patients (adductor canal plus iPACK blocks)

Primary outcome

Resting visual analogue pain score at 24 hours

Effect

VAS 2.4 vs 2.9, mean difference -0.52 (95% CI -1.01 to -0.02); less rescue analgesia

Liposomal bupivacaine is promoted for longer-lasting regional analgesia but costs far more than plain bupivacaine, and head-to-head data in modern knee blocks are limited. This single-centre randomised trial compared it with bupivacaine plus dexamethasone, both given through combined adductor canal and iPACK blocks in 60 total knee replacement patients.

At 24 hours, resting pain was slightly lower with liposomal bupivacaine (VAS 2.4 vs 2.9, mean difference -0.52, 95% CI -1.01 to -0.02), with significant group-by-time effects and better quadriceps strength at 12 hours. Rescue analgesia was less frequent in the liposomal group overall (risk ratio 2.40 favouring it, and 3 vs 11 patients at 48 hours).

The honest reading is a real but small early benefit. Half a point on a 10-point pain scale is below what most patients notice, so the more persuasive signal is the lower rescue-analgesia requirement. Given the large cost difference, this does not establish liposomal bupivacaine as the default; weigh the modest benefit against price and local availability.

• Randomised trial of 60 knee-replacement patients comparing liposomal bupivacaine with bupivacaine plus dexamethasone in ACB and iPACK blocks.
• Resting pain at 24 hours was slightly lower with liposomal bupivacaine (VAS 2.4 vs 2.9, mean difference -0.52).
• Rescue analgesia was less frequent with liposomal bupivacaine (3 vs 11 patients at 48 hours).
• Quadriceps strength favoured the liposomal group at 12 hours.
• Weigh the small analgesic benefit against the much higher cost and availability.

Why it matters

It tests whether an expensive agent earns its price against a cheap, effective alternative, and the margin is narrow.

Don't overread it

With 60 patients at one centre and a sub-perceptible pain difference, this does not justify defaulting to a far more costly drug.

The statistics, in plain English

A 0.52-point difference on a 10-point scale is below the roughly 1 to 2 points patients typically perceive, so the pain benefit may not be clinically meaningful; the lower rescue-analgesia rate is a more tangible signal, but this is a small single-centre trial.

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