Page 11 - CASA Bulletin of Anesthesiology 2019 Vol 6 No 5

Vol.6, No.5, 2019

An ideal nerve block for shoulder surgeries is one that is as effective as an interscalene block
in providing surgical anesthesia, yet preserves diaphragmatic function and is associated with
minimal dyspnea . A promising approach is the superior trunk block, which targets the brachial
plexus at the level of the superior trunk just proximal to the exiting point of the suprascapular
nerve(14) . The technique was initially demonstrated in a case study in which a low volume (12
ml) of local anesthetics was administered to a patient with moderate chronic obstructive pul-
monary disease, resulting in enhanced analgesia and no worsening of pulmonary function . A

number of descriptive anatomic reviews followed(13,15,16,17), but no comparative study in
safety and efficacy was available. Therefore, we performed the first randomized, controlled trial
comparing the effects on pulmonary function and quality of surgical anesthesia and analgesia
between superior trunk blocks and interscalene blocks(30) .

A total of 126 patients undergoing arthroscopic ambulatory shoulder surgery were equally
randomized to either conventional interscalene block or superior trunk block . Fifteen millili-
ter of local anesthetics was used for the blocks and the primary outcome was the incidence of
hemidiaphragmatic paralysis, as assessed by ultrasonography . We found that the superior trunk

block had a lower incidence of hemidiaphragmatic paralyis, compared with the inerscalene
block (4 .8% vs 71 .4%) . Other pulmonary parameters also favored the superior trunk group;
there were minimal changes in minute ventilation and tidal volume compared with the inter-
scalene group . More importantly, no patients in the superior trunk group experienced dyspnea,
while 4 .8% of patients in the interscalene group reported labored breathing . No patients had to
be converted to general anesthesia and postoperative pain scores and opiate consumption were
similar between both groups . Thus, we are able to demonstrate that superior trunk block was
associated with better pulmonary function with equally efficacious anesthesia and analgesia than
interscalene nerve block .

Conclusions

Interscalene blocks are effective regional anesthesia technique to the shoulder, but carry a
significant risk for patients with poor pulmonary function. Among the alternatives for shoulder
surgery, the superior trunk block was associated with the greatest preservation of pulmonary
function while maintaining similar level of anesthesia and analgesia as interscalene block . Fu-
ture directions might include studies patients with limited pulmonary disease .

References:

1 . Fredrickson M, Krishnan S, Chen C: Postoperative analgesia for shoulder surgery: a critical appraisal and review of current tech-
niques. Anaesthesia 2010; 65: 608-24
2 . Abdallah F, Halpern S, Aoyama K, Brull R: Will the Real Benefits of Single-Shot Interscalene Block Please Stand Up? A System-
atic Review and Meta-Analysis . Anesth Analg 2015; 120: 1114-29
3 . Bowens C, Sripada R: Regional blockade of the shoulder: approaches and outcomes. Anesthesiol Res Pract 2012; 2012: 971963
4 . Urmey W, Talts K, Sharrock N: One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachi-
al plexus anesthesia as diagnosed by ultrasonography . Anesth Analg 1991; 72: 498-503
5 . Urmey W, McDonald M: Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and
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