Drs Warlé and Dahan1 raise some interesting suggestions regarding what caused the results in our study investigating the effect of deep neuromuscular blockade in combination with low insufflation pressure on postoperative shoulder pain.2
As a starting point it is important to underline that we investigated a combination of two interventions (i.e. deep neuromuscular blockade and low-pressure pneumoperitoneum) and therefore only are able to reach conclusions about this combination. Whether one intervention contributed more than another therefore remains speculation. In this matter we speculate that the effect was mainly because of the lower insufflation pressure as we are uncertain that there exists a rational explanation of an analgesic effect of either deep neuromuscular blockade or sugammadex based on the current evidence. Warlé and Dahan refer to an interesting study reporting an analgesic effect of a patient group receiving sugammadex after bariatric laparoscopy.3 The study found an analgesic effect on visual analogue scale scores within 30 to 60 min postoperatively in patients administered sugammadex 2 mg kg−1 compared with patients receiving neostigmine 0.05 mg kg−1 along with atropine 0.02 mg kg−1.3 When interpreting the results from this study3 some important issues must be highlighted. In their discussion the authors suggest that their findings may be because of the effect of neostigmine on gastrointestinal motility which may promote movements through the anastomosis causing pain. The results may therefore not be because of an analgesic effect of sugammadex but instead it might be neostigmine causing the pain. Nevertheless, the results are interesting findings, but based on this study we still do not believe that sugammadex per se has an analgesic effect. Finally, it is important to underline that the study does not report the level of neuromuscular blockade under which the laparoscopy was performed. The authors only report that the neuromuscular blockade was reversed when train-of-four counts exceeded two. Also it is unclear if patients and assessors were blinded to the intervention.
Warlé and Dahan suggest that deep neuromuscular blockade may have an analgesic effect as deep neuromuscular blockade facilitates maximum stretching of the abdominal muscles. In theory this may lead to an increased abdominal wall compliance that may reduce pressure-related postoperative shoulder pain. It was because of this hypothesis, based on preliminary observations,4 that we conducted our study.2 While performing our study we also performed another study investigating the effect of deep neuromuscular blockade on the size of the abdominal wall during gynaecologic laparoscopy.5 In a blinded, randomised, cross-over design, we found that deep neuromuscular blockade increases the size of the insufflated abdomen by approximately 3 mm (when measuring from the edge of trocar to the sacral promontory) during a pneumoperitoneum of 8 and 12 mmHg, respectively.5 The clinical effect of this increase is still unknown. However, in our study the employment of deep neuromuscular blockade may have allowed a reduction in the pneumoperitoneum pressure to 8 mmHg which led to a reduced incidence of postoperative shoulder pain.
In conclusion, we agree that low insufflation pressure reduces pain after laparoscopy. However, we are uncertain based on the current evidence that either sugammadex or deep neuromuscular blockade has an analgesic effect per se.
Acknowledgements relating to this article
Assistance with the reply: none.
Financial support and sponsorship: the original study was supported in part by a research grant from the Investigator Initiated Studies Program of Merck Sharp & Dohme Corp, USA. The opinions expressed in this reply are those of the authors and do not necessarily represent those of Merck Sharp & Dohme Corp.
Conflicts of interest: MRG, OI and MVM have received research grants from Merck. MVM, MRG, JR and OI have received speakers’ fees and honoraria from Merck. None of the authors have shares or options in any pharmaceutical company.
1. Warlé MC, Dahan A. Does deep neuromuscular block affect pain after laparoscopic surgery? Eur J Anaesthesiol
2. 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
3. Castro DS, Leão P, Borges S, et al. Sugammadex reduces postoperative pain after laparoscopic bariatric surgery: a randomized trial. Surg Laparosc Endosc Percutan Tech
4. Lindekaer AL, Springborg HH, Istre O. Deep neuromuscular blockade leads to a larger intraabdominal volume during laparoscopy. J Vis Exp
5. Madsen MV, Gätke MR, Springborg HH, et al. Optimising abdominal space with deep neuromuscular blockade in gynaecologic laparoscopy: a randomised, blinded crossover study. Acta Anaesthesiol Scand