- Design
- Randomised, double-blind, controlled trial
- Population
- 160 adults having elective laparoscopic cholecystectomy
- Primary outcome
- Pain on a visual analogue scale at 6 hours
- Effect
- Median 3 vs 4 (p=0.221); paracetamol use 1.04 vs 1.35 (p=0.014, secondary)
A double-blind randomised trial in 160 patients having elective laparoscopic cholecystectomy compared 8 mmHg with 14 mmHg pneumoperitoneum. The primary outcome was pain on a visual analogue scale at 6 hours.
Median scores were 3 against 4 at 6 hours (p=0.221), 2 against 3 at 12 hours (p=0.074) and 1 against 2 at 24 hours (p=0.128), none significant. Mean paracetamol use in the first 24 hours was lower with low pressure, 1.04 against 1.35 doses (p=0.014). Operative time was similar and there were no conversions or major morbidity.
The trial establishes feasibility, not benefit: the primary outcome was negative, and the analgesic finding was secondary and unadjusted for multiple comparisons. Rare complications cannot be assessed in 160 patients, so low pressure is an option for the surgeon who is comfortable with the exposure, not a standard.
- Low pressure was feasible without a longer operation in this trial.
- The primary pain outcome at 6 hours was not significantly different.
- The lower analgesic use was a secondary result; treat it as hypothesis-generating.
- Keep a low threshold to raise the pressure if exposure is poor.
Why it matters
A widely adopted tweak to reduce pain did not clearly do so in a registered, blinded trial.
Don't overread it
The significant paracetamol result was secondary and the trial was too small for rare complications.
The statistics, in plain English
A p-value above 0.05 on the primary outcome means no difference was shown, not that none exists; a 160-patient trial is small. A single significant secondary result among several is weaker evidence, because testing many outcomes makes a chance finding likelier.
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