Supraclavicular Brachial Plexus Block

A. About one-third after the supraclavicular block versus about 3% after the infraclavicular block

Eleven of 32 versus 1 of 32 for complete paralysis; counting partial paralysis too, 44% versus 13%. About a third of supraclavicular patients still lost the hemidiaphragm, so the approach is not phrenic-sparing in any absolute sense, and the authors' own reading is that the infraclavicular approach greatly reduced the risk without eliminating it. Note the comparison this trial actually made: supraclavicular against infraclavicular. It says nothing about how either compares with an interscalene block.

Four patients had a symptomatic, radiologically confirmed pneumothorax — 0.06% (95% CI 0.001 to 0.124) — against a historical rate reported as high as 6.1% without ultrasound monitoring. The detail that matters is that three of the four presented after a two-day latency period. A pneumothorax from a supraclavicular block is not reliably apparent before the patient goes home, so discharge advice has to name breathlessness and pleuritic chest pain over the following days as reasons to seek help, rather than relying on a normal immediate recovery.

A complication with a delayed presentation is a communication problem as much as a technical one. Note too that all the anaesthetists involved in these four complications had previously performed fewer than 20 of these blocks, though the study could not confirm an experience of 20 blocks or fewer as a statistically significant risk factor.

Analgesia was comparable: 24-hour pain scores differed by -0.34 (95% CI -0.75 to 0.07) and morphine equivalent consumption by 1.84 mg per 24 hours (95% CI -0.00 to 3.69), neither reaching significance. On adverse effects the supraclavicular approach was better for two of the three — hemidiaphragmatic paresis risk ratio 0.56 (95% CI 0.39 to 0.82) and Horner's syndrome risk ratio 0.29 (95% CI 0.19 to 0.44) — with no significant difference in hoarseness (risk ratio 0.73, 95% CI 0.48 to 1.13). How firmly can you act on it? Not very: the authors' own wording is that the supraclavicular approach might be an efficient alternative, but that the available evidence is inadequate and prevents a firm conclusion. Read the numbers at their true strength — a risk ratio of 0.56 is a reduction in hemidiaphragmatic paresis, not abolition of it, and the meta-analysis reports no respiratory outcomes in patients with limited respiratory reserve, so it cannot tell you how the two blocks behave in the patient for whom that reduction would matter most.

"Fewer adverse effects, equal analgesia, inadequate evidence" is a common shape in regional anaesthesia meta-analyses. Read the reviewers' own confidence statement before you change practice on the point estimate.