Pre-oxygenation using high-flow nasal oxygen in parturients undergoing caesarean section in general anaesthesia: A prospective, multi-centre, pilot study.

BACKGROUND: Parturients undergoing caesarean section in general anaesthesia have an increased risk of desaturating during anaesthesia induction. Pre- and peri-oxygenation with high-flow nasal oxygen prolong the safe apnoea time but data on parturients undergoing caesarean section under general anaesthesia are limited. This pilot study aimed to investigate the clinical effects and frequency of desaturation in parturients undergoing caesarean section in general anaesthesia pre- and peri-oxygenated with high-flow nasal oxygen and compare this to traditional pre-oxygenation using a facemask. METHODS: In this prospective, non-randomised, multi-centre study we included pregnant women with a gestational age ≥30 weeks undergoing caesarean section under general anaesthesia. All parturients were asked to participate in the intervention group consisting of pre-oxygenation using high-flow nasal oxygen. Parturients declining participation were pre-oxygenated with a traditional facemask. Primary outcome was the proportion of parturients desaturating below 93% from start of pre-oxygenation until 1 min after tracheal intubation. Secondary outcomes investigated end-tidal oxygen concentrations after tracheal intubation and the proportion of parturients with signs of regurgitation. RESULTS: A total of 34 parturients were included, 25 pre- and peri-oxygenated with high-flow nasal oxygen and 9 pre-oxygenated with facemask. No difference in patient or airway characteristics could be seen except for a higher BMI in the high-flow nasal oxygen group (31.4 kg m-2 [4.7] vs. 27.7 kg m-2 [3.1]; p = .034). No woman in any of the two groups desaturated below 93%. The lowest peripheral oxygen saturation observed, in any parturient, was 97%. There was no difference detected in end-tidal oxygen concentration after tracheal intubation, 87% (6) in the high-flow nasal oxygen group vs 80% (15) in the facemask group (p = .308). No signs of regurgitation, in any parturient, were seen. CONCLUSION: Pre- and peri-oxygenation with high-flow nasal oxygen maintain adequate oxygen saturation levels during induction of anaesthesia also in parturients. Regurgitation of gastric content did not occur in any parturient and no other safety concerns were observed in this pilot study.

Deep anaesthesia reduces postoperative analgesic requirements after major urological procedures.

BACKGROUND AND OBJECTIVE: There is evidence from previous studies that deeper anaesthetic levels reduce postoperative pain along with analgesic requirements. The aim of this study was to confirm this observation during major urological procedures under sevoflurane anaesthesia. METHODS: Seventy ASA I or II patients undergoing radical prostatectomy or nephrectomy were randomly allocated into two groups: the L-BIS group with BIS (bispectral index scale) values kept within a range of 20-30 and the H-BIS group with values within the range of 50-60. Sevoflurane was the main anaesthetic agent used, along with inhalation of nitrous oxide and continuous remifentanil infusion. Postoperative analgesia was achieved mainly through morphine and ketamine, which was continuously infused by pump, and intravenous parecoxib. Additional analgesics (paracetamol, parecoxib and morphine) were administered in persistent (continuous, lasting longer than predicted and requiring repeated doses of analgesics) postoperative pain. The number of patients who demanded additional analgesia during the first 24 h was recorded, as well as the number of administrations performed, along with visual analogue scale (VAS) scores at 8 and 24 h. RESULTS: Sixty patients completed the study, 30 in each group. VAS scores at 8 h were significantly higher in the H-BIS group, both at rest [1 (0-4) vs. 2 (0-8), P = 0.036] and on cough [1 (0-5) vs. 2 (2-9), P = 0.021], but at 24 h were similar between the two groups. Four patients in the L-BIS group and 17 patients in the H-BIS group demanded additional analgesia (P < 0.0009), although the patients in the L-BIS group needed significantly fewer additional doses of analgesics than those in the H-BIS group [0 (0-2) vs. 1 (0-5), P < 0.0008]. CONCLUSION: The results show that intraoperative deep anaesthetic levels during major urological procedures, achieved with high sevoflurane concentrations, lead to reduced postoperative analgesic requirements.