Influence of variations in arterial PCO2 on surgical conditions during laparoscopic retroperitoneal surgery

Abstract

Background: Although deep neuromuscular block (post-tetanic-count 1-2 twitches) improves surgical conditions during laparoscopic retroperitoneal surgery compared with standard block (train-of-four 1-2 twitches), the quality of surgical conditions varies widely, often related to diaphragmatic contractions. Hypocapnia may improve surgical conditions. Therefore we studied the effect of changes in arterial carbon dioxide concentrations on surgical conditions in patients undergoing laparoscopic surgery under general anaesthesia and deep neuromuscular block.

Methods: Forty patients undergoing elective laparoscopic surgery for prostatectomy or nephrectomy received propofol/remifentanil anaesthesia and deep neuromuscular block with rocuronium. Patients were randomized to surgery under hypocapnic or hypercapnic conditions. During surgery, the surgical conditions were evaluated using the 5-point Leiden-Surgical Rating Scale (L-SRS) ranging from 1 (extremely poor conditions) to 5 (optimal conditions) by the surgeon, who was blinded to group.

Results: Mean (sd) arterial carbon dioxide concentrations were 4.5 (0.6) [range: 3.8-5.6] kPa under hypocapnic and 6.9 (0.6) [6.1-8.1] kPa under hypercapnic conditions. The L-SRS did not differ between groups: 4.84 (0.4) [4-5] in hypocapnia and 4.77 (0.4) [3.9-5] in hypercapnia. Ninety-nine percent of ratings were good or excellent irrespective of treatment.

Conclusions: Deep neuromuscular block provides good to optimal surgical conditions in laparoscopic retroperitoneal urological surgery, independent of the level of arterial [Formula: see text].

Clinical trial registration: NCT01968447.

Keywords: carbon dioxide; hypercapnia; hypocapnia; laparoscopy; nephrectomy; neuromuscular block; prostatectomy; rocuronium; urological surgical procedures.

© The Author 2016. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Figures

Fig 1

Flow chart of the study.

Fig 2

(a) Individual end-tidal PCO2 values over time. Blue lines hypocapnia, orange lines hypercapnia. (b) Individual mean end-tidal and arterial PCO2 values and mean of the means (sd). *P<0.001. (c and d) Profiles of the arterial PCO2, end-tidal PCO2 and difference between arterial and end-tidal PCO2 (ΔPCO2) under hypocapnic (c) and hypercapnic conditions (d). Data are mean (95% confidence interval).

Fig 3

(a) Mean (95% confidence interval) Leiden-Surgical Rating Scale (L-SRS) scores against time under hypocapnic (blue symbols) and hypercapnic conditions (green symbols). (b) Individual mean L-SRS scores (each symbol is the mean L-SRS of one patient) and mean of the means (sd). In pink the results of the BLISS 1 study performed under normocapnic conditions (arterial PCO2 6 kPa or 45 mm Hg). (c) Distribution of the surgical ratings under hypocapnic (blue bars) and hypercapnic (green bars) conditions. (d) Individual mean L-SRS scores vs mean individual end-tidal PCO2 values in subjects treated with hypocapnia (blue symbol) and hypercapnia (green symbol). Pearson r=0.02, P=0.9.