Pectoral Nerve Blocks

A. Analgesia lasted longer with the PECS II block (mean 295 vs 198 minutes) and 24-hour morphine was lower with it (3.9 vs 5.3 mg)

In this single trial the PECS II block outlasted the paravertebral block by roughly an hour and a half and saved about 1.4 mg of morphine over 24 hours. Seventeen of 20 PECS II patients had T2 dermatomal spread against four of 20 in the paravertebral group — a difference in coverage that sits well with the analgesic result for an operation reaching the axilla, though the trial reports the two findings alongside each other rather than showing that one produced the other.

Against systemic analgesia alone the PECS II block reduced 24-hour opioid consumption by about 13.6 mg oral morphine equivalents (95% CI -21.2 to -6.1) and lowered acute pain scores at every interval in the first 24 hours. Against a thoracic paravertebral block it was no better: opioid consumption differed by 8.7 mg oral morphine equivalents with a confidence interval crossing zero (-18.2 to 0.7, p = 0.07), and pain scores were similar after the first measurement. So the honest description is that PECS II clearly beats no block and is a comparable alternative to a paravertebral block, not an improvement on one.

Two comparisons in one paper answer two different questions. "Better than nothing" is not "better than the standard", and the confidence interval crossing zero is what separates them here.

It was negative. Pain score in recovery was a median of 3.0 in both the bupivacaine and the saline groups (p = 0.55), and cumulative morphine consumption up to 24 hours did not differ. Only in the subgroup having major surgery — mastectomy or tumourectomy with axillary clearance, 29 patients — was there a difference, and the authors describe it as statistically significant although not clinically significant. The design is the point: against a background of multimodal analgesia plus surgical infiltration, a block that covers only the pectoral nerves has very little left to add. Note what the authors themselves conclude from the subgroup — not that PECS I is worthwhile for extensive operations, but that its role in extended breast surgery may warrant further investigation.

In this trial the comparator was not nothing: every patient, in both arms, also received multimodal analgesia and surgeon-administered local infiltration. Read what else the patient is already getting before concluding from a negative trial that the block does not work.