We thank Drs Unterbuchner and Werkman1 for highlighting some important issues regarding our study investigating the effect of deep neuromuscular blockade in combination with low-pressure pneumoperitoneum on the occurrence of shoulder pain.2 We have revisited our data and here provide the requested additional results along with comments to their letter.
At application of pneumoperitoneum (insertion of Veress needle), 46 (83.6%) patients had a train-of-four count of at least 4 (recovery of neuromuscular blockade).3 Five (9.1%) patients had a moderate neuromuscular blockade (train-of-four count 1 to 3).3 In four (7.2%) patients, neuromuscular blockade never reached a moderate level (train-of-four count of at least 4) after administration of 0.3 mg kg−1 rocuronium. Average operating time (from insertion of Veress needle to last suture) in the group with the institute's standard-pressure pneumoperitoneum was 70 (range, 42 to 148) min. In mean, 87% (range, 59 to 100%) of the operating time was performed without neuromuscular blockade (train-of-four ratio >0.9) in the group with standard-pressure pneumoperitoneum. Forty-one out of 55 patients (75%) in the group with standard-pressure pneumoperitoneum had at least 80% of surgery performed without neuromuscular blockade. According to these results, patients were, as suggested by Drs Unterbuchner and Werkman,1 only receiving a very shallow level of neuromuscular blockade and only a moderate neuromuscular blockade (train-of-four count 1 to 3) during a minor initial part of the surgery.
We identified two patients reporting shoulder pain at days 11 and 12 after surgery.2 One patient reported both incisional, lower abdominal and overall pain as well as shoulder pain within a period of 7 to 12 days after surgery with visual analogue scale scores between 29 and 71. This patient reported no use of opioids within this period. We speculate that the shoulder pain could be referred pain from the lower abdomen. It seems, however, unlikely that at this time, the pain should be because of the residual carbon dioxide in the abdomen which is speculated to be one cause of shoulder pain.4 The second patient reported pain (visual analogue scale, 81) in the lower abdomen at day 11 because of muscle tensions in the pelvic region stretching out to the back and up to the shoulders. Visual analogue scale scores for shoulder and incisional pain was at this time 38 and for overall pain was 81. The patient took paracetamol 1000 mg and oxycodone 5 mg at day 11.
Drs Unterbuchner and Werkman1 ask if moderate neuromuscular blockade or even shallow neuromuscular blockade could be sufficient. In this matter, they refer to the observational study by Lindekaer et al.5 reporting that employment of deep neuromuscular blockade (posttetanic count <2) increased the size (distance from sacral promontory to skin surface) of the insufflated abdomen with differences of more than 10 mm. However, it is important to underline that in a randomised, cross-over and blinded design, which we conducted during the present study,2 it was only possible to find differences of approximately 3 mm.6 Nevertheless, our study may indicate that deep neuromuscular blockade compensates the lower insufflation pressure allowing the surgeons to complete surgery without requiring increased pneumoperitoneum pressure. However, the 100% completion rates in our study may also be because of the very experienced surgeons performing the hysterectomies. It is possible as Drs Unterbuchner and Werkman1 state that less experienced surgeons may have perceived surgical overview differently and may have been more prone to use rescue interventions.
There are most probably differences in the need for neuromuscular blockade during different types of laparoscopy. Drs Unterbuchner and Werkman refer to a recent study7 on laparoscopic cholecystectomies reporting that deep neuromuscular blockade only marginally improved surgical conditions during low-pressure pneumoperitoneum. In laparoscopic hysterectomies, the vast majority of the operation is performed within the pelvic region where muscle tensions may not have the same influence on surgical conditions as in laparoscopic cholecystectomies that are performed in close proximity of the diaphragm. Also there is most probably a difference in surgeons’ perceptions of what characterises sufficient surgical overview. To prevent such differences, evaluations of the quality of the surgical overview should ideally be performed using validated assessment tools although this is a challenging task.
Finally, Drs Unterbuchner and Werkman question if the investigation of shoulder pain at all was relevant. For example, visual analogue scale scores for mean shoulder pain during 14 postoperative days did not exceed 14. We agree that the patients in our study on average had relatively low pain scores. However, the aim of our study was to investigate the occurrence of patients with clinically relevant shoulder pain (visual analogue scale score >20) not the average of pain scores. As previously discussed,2 we believe that our findings are mainly because of a multimodal pain regimen in combination with surgery performed during a relatively low standard pressure (12 mmHg) involving pulmonary recruitment manoeuvres.2
In conclusion, we agree with Drs Unterbuchner and Werkman that more studies are needed to investigate the effect of moderate neuromuscular blockade through closure of the fascia compared with deep neuromuscular blockade on both surgical conditions and patient outcomes. Our present study is not able to provide such evidence of the effect of moderate neuromuscular blockade through closure of the fascia. Instead, our study revealed that deep neuromuscular blockade in combination with low-pressure pneumoperitoneum (8 mmHg) was better than a standard neuromuscular blockade regimen in combination with standard-pressure pneumoperitoneum (12 mmHg).
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. Unterbuchner C, Werkmann M. Postoperative shoulder pain after laparoscopic hysterectomy with deep neuromuscular blockade and low-pressure pneumoperitoneum. 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. Fuchs-Buder T, Claudius C, Skovgaard LT, et al. 8th International Neuromuscular Meeting. Good clinical research practice in pharmacodynamic studies of neuromuscular blocking agents II: the Stockholm revision. Acta Anaesthesiol Scand
4. Tsai HW, Chen YJ, Ho CM, et al. Maneuvers to decrease laparoscopy-induced shoulder and upper abdominal pain: a randomized controlled study. Arch Surg
5. Lindekaer AL, Springborg HH, Istre O. Deep neuromuscular blockade leads to a larger intraabdominal volume during laparoscopy. J Vis Exp
6. 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
7. Staehr-Rye AK, Rasmussen LS, Rosenberg J, et al. Surgical space conditions during low-pressure laparoscopic cholecystectomy with deep versus moderate neuromuscular blockade: a randomized clinical study. Anesth Analg