Continuous vs single injection interscalene block for major shoulder surgery?

 

Should continuous rather than single-injection interscalene block be routinely offered for major shoulder surgery? A meta-analysis of the analgesic and side-effects profiles. Vorobeichik, R. et al. Br J Anaesth. 2018 Apr;120(4):679-692. doi: 10.1016/j.bja.2017.11.104.

 

Major shoulder surgery is associated with moderate to severe pain. Single injection Interscalene blocks (SISB) offers good perioperative analgesia, but continuous catheter based interscalene blocks (CISB) may provide better analgesia into the post op period.

The authors of this paper hypothesised that CISB provides superior analgesia for major shoulder surgery. They conducted a meta-analysis of the currently available data to determine if there was sufficient evidence available to support their hypothesis.

 

METHOD

A database search for any Randomised Controlled Trial (RCT) comparing the effect of CISB to SISB on analgesic outcome and side effects after major shoulder surgery was conducted. Major surgery was defined by the authors of this paper to include procedures such as arthroplasty and rotator cuff repair. The quality of the reviewed RCTs was assessed using the Cochrane Collaboration Risk of Bias tool.

 

OUTCOMES

Primary outcome – the cumulative analgesic consumption in the first 24h postop (expressed as oral morphine equivalents).

Secondary outcomes included: 24-48h analgesia consumption, 48-72h analgesia consumption, Rest pain and dynamic pain severity, patient satisfaction, time to first analgesic request, risk of PONV, respiratory dysfunction, block related complications, and time to discharge.

 

HETEROGENIETY

The authors identified that different characteristics of the individual RCTs may have been a source of error in their calculations. The degree to which these factors impacted on the primary outcome was evaluated using meta-regression analysis.

 

STATISTICAL ANALYSIS

Analysed data on intention to treat basis. Meta-analytic techniques (Revman 5.3.5) and OpenMeta (Analyst) were used to combine the data.

Odds Ratio (OR) and 95% Confidence Interval (CI) were reported for dichotomous outcomes while the weighted mean difference (WMD) and 95% CI used for continuous outcomes. Strength of pooled evidence was assessed using the GRADE guidelines.

 

RESULTS

15 RCTs included in final analysis, 793 patients – 395 CISB and 398 SISB.

Primary OutcomeCISB reduced the cumulative oral morphine equivalent consumption at 24h postoperatively by 50.9mg ( -81.6, -20.2) p=0.001. Three confounders were significant (p<0.001) predictors of the primary outcome results – i) type of Local anaesthetic used ii) CISB loading dose  iii) duration of CISB infusion. Patients having rotator cuff repair had the largest reduction in cumulative opioid consumption.

Secondary Outcomes of significance were:

24-48h analgesic consumption – patients with CISB used 44.7mg oral morphine equivalent less than those who had SISB.

48-72h analgesic consumption – only one trial reported this data. CISB reduced analgesia consumption by 50%.

Pain at rest – no difference within 8h post op, but compared with SISB, CISB reduced pain at rest at 12,16,24, and 48h.

Dynamic pain – CISB patients had significantly reduced pain scores at 24, 48 and 72h

Patient satisfaction – patients who had CISB reported higher levels of satisfaction (p<0.00001).

PONV – Administering CISB reduced the odds of PONV by an OR 0.3.

Respiratory function – CISB patients had worse spirometry results at 24h compared to SISB patients.

Complications – Low incidence. 11 dislodged catheters, 5 unable to insert catheter.

 

DISCUSSION

CISB patients had better pain scores up to 48h post op , less PONV and higher satisfaction scores.

Side effects were minimal.

 

LIMITATIONS

Small number of relevant RCTs.

Evolving clinical practice – US guided SISB makes blocks safer and more reliable, use of adjuvants may prolong SISB effects.

Safety data collated from only two trials. May account for low incidence of complications.

Preop pain scores not considered in analysis.

 

IMPACT

Thorough review of existing literature. Clearly defined parameters for this review. Confounders analysed alongside data.

We felt on discussing this paper that it would not change our current practice for two main reasons:

  1. Limited safety data produced by this review
  2. Considerable resources required to introduce and manage a post op local anaesthetic catheter service locally.

 

Summary by Dr Ozair Hasnain

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