Does deep neuromuscular blockade provide better operating conditions?

Influence of deep neuromuscular block on the surgeon’s assessment of surgical conditions during laparotomy: a randomized controlled double blinded trial with rocuronium and sugammadex  –  M.V. Madsen et al British Journal of Anaesthesia, 119 (3): 435–42 (2017)

 

“Opinion is the medium between knowledge and ignorance.” – Plato

Clinical question

  • Does deep neuromuscular blockade (NMB) improve surgical conditions and / or reduce surgical complications in patients undergoing laparotomy?

Background

  • Abdominal wall muscle tension causes difficult surgical conditions at laparotomy
  • Inadequate neuromuscular blockade (NMB) during closure could potentially contribute to adverse outcomes such as wound dehiscence or incisional hernia
  • Diaphragm and abdominal muscles are most resistant to NMB and peripheral neuromuscular monitoring will underestimate central neuromuscular recovery

Hypothesis

  • Deep NMB via continuous infusion of rocuronium offers improved surgical conditions vs standard neuromuscular blockade via intermittent bolus dosing

Study population

  • 128 patients aged over eighteen undergoing elective open upper abdominal surgery at Aarhus University Hospital in Denmark
  • A further 141 patients were assessed for eligibility but excluded (of this group 82 were due to logistical reasons and 42 due to inability to consent)

Methodology

  • Double-blinded randomised controlled trial with block randomisation to either group DEEP or group STANDARD
  • Group STANDARD received 0.6mg/kg rocuronium at induction then, if conditions were assessed as poor, a first line intervention of propofol and second line intervention of rocuronium 10mg were given
  • Group DEEP received 0.6mg/kg rocuronium at induction then and infusion of rocuronium titrated to a post-tetanic count of 0-1 – with same interventions as above if conditions assessed as poor
  • Neuromuscular monitoring was via “TOF-Watch” at the ulnar nerve
  • Assessment of surgical conditions was made every half hour and after any intervention via 5-point subjective scale (that 5 surgeons had been trained in pairs to use prior to the study) ranging from 1 (extremely poor) to 5 (optimal)

Outcomes

  • Primary outcome was surgical condition scores averaged over whole procedure
  • Secondary outcomes included incidences of poor surgical conditions and postoperative complications

Results

  • Average surgical ratings were better in group DEEP at 4.75 vs 4.0 (out of max 5)
  • Fewer anaesthetic interventions were required in the DEEP group
  • All patients in group DEEP were reversed with suggamadex vs 14% requirement in group STANDARD
  • No change in postoperative complications was detected

Strengths

  • Similar groups with appropriate randomisation and blinding
  • Demonstrated a statistically significant treatment effect between the two groups using study’s own (albeit non-validated) scale
  • All patients randomised were accounted for in final analysis

Weaknesses

  • Large group (82) assessed for eligibility but excluded for ‘logistic reasons’
  • Subjective nature of scoring system
  • Inadequately powered for detecting secondary outcomes
  • It is possible that infusion kinetics titrated to a less deep level of block would produce the same improvement in conditions
  • The ‘STANDARD’ group arguably does not reflect standard anaesthetic practice – giving only a single dose of NMB, not using NM monitoring, and giving a further dose (after first trialing propofol) only if surgical conditions are poor
  • Small overall difference in primary outcome (average score of good vs average score approaching optimal) may not justify the significant increase in suggamadex usage

Summary by Dr Alex Bennett

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