Madsen et al.1 report an absolute risk reduction in the occurrence of shoulder pain of 31% after laparoscopic hysterectomy with the combination of deep neuromuscular blockade (NMB, posttetanic count ≤1) and low-pressure pneumoperitoneum (8 mmHg) in comparison to ‘moderate’ neuromuscular blockade with the institute's standard-pressure pneumoperitoneum (12 mmHg).
This trial is an important contribution to the question how to minimise shoulder pain after laparoscopic procedures. Nevertheless, there are some issues that deserve discussion.
First, in both the groups, intubation was performed after the administration of 0.3 mg kg−1 rocuronium. In the group with low-pressure pneumoperitoneum, a profound to deep neuromuscular blockade (posttetanic count ≤1) was maintained using a bolus of rocuronium 0.7 mg kg−1 just after intubation and infusion of rocuronium 0.3 to 0.4 mg kg−1 h−1 during the surgical procedure. In the group with standard-pressure pneumoperitoneum, there was no further protocol-based muscle relaxant application (also no rescue dose of rocuronium) and neuromuscular function was allowed to recover spontanously.1 Anaesthesia was maintained with propofol 3 mg kg−1 h−1 and remifentanil 0.25 to 0.5 μg kg−1 min−1 (entropy target, 30 to 50) in both the groups.1
Owing to the low dose of rocuronium (0.3 mg kg−1) and the corresponding shortened neuromuscular recovery times (DUR 25% = 16 ± 5 min, DUR train-of-four 80% = 34 ± 7 min) one may assume that during a large part of the surgical procedures (42 to 148 min) in the group with the standard-pressure pneumoperitoneum, there was actually no moderate neuromuscular blockade (train-of-four 1 to 2).2,3 Thus, the authors probably compared deep versus very shallow (train-of-four ratio, 50 to 90%) or no neuromuscular blockade. In this context, more information concerning the lag time between low-dose rocuronium neuromuscular blockade and application of pneumoperitoneum, the level of muscle paralysis during surgery in the group with standard-pressure pneumoperitoneum and the doses of propofol and remifentanil would be helpful in interpreting the results.
Although no rating was performed, the operation conditions seemed to be good and not relevantly different in both the groups during total intravenous anaesthesia with relatively low doses of propofol (3 mg kg−1 h−1). All surgical procedures were finished according to group allocation.1 This is in accordance with Lindekaer et al.4, demonstrating that intra-abdominal space (distance from the promontory to the surface of the umbilical skin) at 8 mmHg with deep neuromuscular block (posttetanic count <2) is comparable to the intra-abdominal space at 12 mmHg without neuromuscular block. So one may speculate that during total intravenous anaesthesia with a real moderate level of relaxation (train-of-four 1 to 2) or during balanced anaesthesia using the muscle relaxing effect of volatile agents (sevoflurane, desflurane) with moderate-to-shallow neuromuscular block (train-of-four 3 to 4), good operation conditions and reduction of shoulder pain could also be achieved by using low-pressure pneumoperitoneum (<10 mmHg).3,5,6
In contrast to Madsen et al.,1 a trial in laparascopic cholecystectomy demonstrated a success rate of just 60% in finishing surgical procedures with low-pressure pneumoperitoneum (8 mmHg) and deep neuromuscular block (posttetanic count ≤1). They found no significant difference in outcome parameters (postoperative pain, oxycodone consumption, time delay to normal activity, nausea). The authors concluded that deep versus moderate neuromuscular block (actually shallow neuromuscular block in the study) improved surgical space conditions just marginally during low-pressure laparoscopic cholecystectomy.7
In accordance with these results, Madsen et al.1 also identified no difference in the area under the curve of visual analogue scale ratings of shoulder pain, incisional pain, lower abdominal pain and overall pain for 4 and 14 days. Furthermore, opioid use and other recovery parameters were not different between deep neuromuscular blockade with low-pressure pneumoperitoneum and moderate neuromuscular blockade with standard-pressure pneumoperitoneum. They found only a significant reduction in the incidence of shoulder pain during the 14 days after laparoscopic hysterectomy in the group with low-pressure pneumoperitoneum. The authors judged the pain ratings of less than 20/100 on the visual analogue scale as clinically not relevant. If the scaling of the mean shoulder pain ratings in Figure 2 is correct,1 the shoulder pain (mean visual analogue scale <14) would have been irrelevant across the whole observational period (14 days) in both the groups. Furthermore, it is unexpected that in the group with moderate neuromuscular blockade, an estimated 2 to 3% of the patients reported on shoulder pain on days 11 and 12 (see Figure 3 in the original article), on days 7 to 10 nobody indicated shoulder pain.1 Was there another origin of shoulder pain? For daily clinical practice, we should also recall the possible role of the duration of surgery in the development of postoperative shoulder pain after laparoscopic interventions and the possible prolongation of laparoscopies using low-pressure pneumoperitoneum in the hand of inexperienced surgeons.6
Finally, this randomised, controlled, double-blinded trial reveals a lot of unresolved issues in the management of laparascopic surgery. The peer-reviewed literature is still lacking studies of operating field conditions in different surgical procedures comparing deep versus moderate muscle relaxation and their consecutive effects on outcome parameters. So future trials should investigate these issues, keeping a watching brief on the real level of neuromuscular blockade.
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1. Madsen MV, Istre O, Staehr-Rye AK, Springborg HH, Rosenberg J, Lund J, Gätke MR. Postoperative shoulder pain after laparoscopic hysterectomy with deep neuromuscular blockade and low-pressure pneumoperitoneum: a randomised controlled trial. Eur J Anaesthesiol
2. Schlaich N, Mertzlufft F, Soltesz S, Fuchs-Buder T. Remifentanil and propofol without muscle relaxants or with different dose of rocuronium for tracheal intubation in outpatient anaesthesia. Acta Anaesthesiol Scand
3. Fuchs-Buder T, Claudius C, Skovgaard LT, et al. Good clinical research practice in pharmacodynamic studies of neuromuscular blocking agents II: the Stockholm revision. Acta Anaesthesiol Scand
4. Lindekaer AL, Halvor Springborg H, Istre O. Deep neuromuscular blockade leads to larger intraabdominal volume during laparascopy. J Vis Exp
5. Paul M, Fokt RM, Kindler CH, et al. Charakterization of the interactions between volatile anaesthetics and neuromuscular blockers at the muscle nicotinic acetylcholine receptor. Anesth Analg
6. Donatsky AM, Bjerrum F, Gögenur I. Surgical technique to minimize shoulder pain after laparascopic cholecystectomy. A systemic review. Surg Endosc
7. Staehr-Rye AK, Rasmussen LS, Rosenberg J, et al. Surgical space conditions during low-pressure laparascopic cholecystectomy with deep versus moderate neuromuscular blockade: a randomized clinical study. Anesth Analg