Esketamine 0.2 mg/kg is the dose that buys block duration without the slow wake-up

Design

Prospective four-arm randomised controlled dose-comparison trial

Population

160 patients undergoing thoracoscopic radical resection for lung cancer with thoracoscopy-guided paravertebral block

Primary outcome

Time to first patient-controlled analgesia demand and postoperative pain scores

Effect

All esketamine doses prolonged analgesia over ropivacaine alone; 0.2 and 0.3 mg/kg longer than 0.1, with wake-up delayed only at 0.3 mg/kg

One hundred and sixty patients having thoracoscopic radical resection for lung cancer were randomised to a thoracoscopy-guided paravertebral block with 20 mL of 0.375 per cent ropivacaine alone, or with esketamine at 0.1, 0.2 or 0.3 mg/kg.

All three esketamine doses beat plain ropivacaine: longer to first patient-controlled analgesia demand, lower pain scores at 6, 12, 24 and 48 hours, less sufentanil in the first 24 hours, fewer rescue doses, and earlier ambulation and chest drain removal. The 0.2 and 0.3 mg/kg doses lasted longer than 0.1.

The ceiling is at the top. Wake-up time was longer with 0.3 mg/kg than with control, 0.1 or 0.2 — so the highest dose buys no extra analgesia over 0.2 and costs recovery time. That makes 0.2 mg/kg the dose to use, which is the kind of finding that changes a standard block mix rather than a policy.

• Where esketamine is added to a paravertebral block, 0.2 mg/kg is the dose these data support.
• Expect the gain in the first 48 hours, including earlier chest drain removal and ambulation.
• Watch recovery time if a higher dose is used; that is where the cost appeared.
• Screen for the usual ketamine cautions — psychotomimetic effects, raised intracranial or intraocular pressure, uncontrolled hypertension.
• The block here was placed under thoracoscopic vision by the surgeon; a percutaneous ultrasound-guided block is not the same technique.

Why it matters

It gives a specific dose for an adjuvant many units already add by habit at whatever dose the last person used.

Don't overread it

Single-centre dose-finding trial; the added benefit may be systemic rather than from the block itself.

The statistics, in plain English

This is a four-arm dose-finding trial with 40 patients per arm, and the results are reported as between-group differences without effect sizes for most outcomes — so the direction is clear and the magnitude is not. Multiple outcomes across four groups means many comparisons; the consistent pattern across time points and the separation between 0.1 and 0.2 mg/kg are more persuasive than any single P value. No placebo-controlled systemic esketamine arm was included, so a systemic rather than local mechanism cannot be excluded.

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