Nitrous oxide in ambulatory anaesthesia: does it have a place in day surgical anaesthesia or is it just a threat for personnel and the global environment?

Nitrous oxide-related postoperative nausea and vomiting depends on duration of exposure

BACKGROUND

Inclusion of nitrous oxide in the gas mixture has been implicated in postoperative nausea and vomiting (PONV) in numerous studies. However, these studies have not examined whether duration of exposure was a significant covariate. This distinction might affect the future place of nitrous oxide in clinical practice.

METHODS

PubMed listed journals reporting trials in which patients randomized to a nitrous oxide or nitrous oxide-free anesthetic for surgery were included, where the incidence of PONV within the first 24 postoperative hours and mean duration of anesthesia was reported. Meta-regression of the log risk ratio for PONV with nitrous oxide (lnRR PONVN2O) versus duration was performed.

RESULTS

Twenty-nine studies in 27 articles met the inclusion criteria, randomizing 10,317 patients. There was a significant relationship between lnRR PONVN2O and duration (r = 0.51, P = 0.002). Risk ratio PONV increased 20% per hour of nitrous oxide after 45 min. The number needed to treat to prevent PONV by avoiding nitrous oxide was 128, 23, and 9 where duration was less than 1, 1 to 2, and over 2 h, respectively. The risk ratio for the overall effect of nitrous oxide on PONV was 1.21 (CIs, 1.04-1.40); P = 0.014.

CONCLUSIONS

This duration-related effect may be via disturbance of methionine and folate metabolism. No clinically significant effect of nitrous oxide on the risk of PONV exists under an hour of exposure. Nitrous oxide-related PONV should not be seen as an impediment to its use in minor or ambulatory surgery.

Comparison of recovery profiles of propofol and sevoflurane anesthesia with bispectral index monitoring in percutaneous nephrolithotomy

BACKGROUND

The aim of the study was to evaluate the comparative effects of propofol infusion versus sevoflurane for maintenance of anesthesia with respect to hemodynamics, recovery characteristics, nausea and vomiting in patients undergoing percutaneous nephrolithotomy.

METHODS

Forty American Society of Anesthesiologists physical status I-II patients, aged between 22 and 65 years were randomly divided to receive either intravenous anesthesia with propofol (group P) or sevoflurane (group S). Cardiovascular variables, peripheral oxygen saturation (SpO2), end-tidal carbon dioxide (ETCO2), bispectral index (BIS) and train-of-four (TOF) values were recorded at intervals throughout the procedure. Time to spontaneous respiration, eye opening, extubation, obey commands, hand squeezing, Aldrete Score > 9 and the incidence of postoperative nausea and vomiting were recorded.

RESULTS

Early recovery times [spontaneous respiration (P = 0.002), eye opening (P = 0.006), extubation (P = 0.013), obey commands (P < 0.05), hand squeezing (P = 0.005)] were significantly longer in group P. The incidence of vomiting was significantly higher in group S (P < 0.05). Hemodynamic parameters, levels of SpO2, ETCO2, and BIS and TOF values were not significantly different between the groups (P > 0.05).

CONCLUSIONS

The present study which adjusted sevoflurane concentration and propofol infusion rate according to BIS values revealed that maintenance of anesthesia with sevoflurane is associated with faster recovery than anesthesia with propofol. Propofol resulted in a significantly lower incidence of postoperative nausea and vomiting. Hemodynamic parameters and levels of SpO2 and ETCO2 were comparable between the groups during percutaneous nephrolithotomy.

Nitrous oxide makes me sick: or does it? Nitrous oxide and postoperative nausea and vomiting

This article evaluates whether avoidance of nitrous oxide in general anaesthesia can improve clinical outcomes in surgical patients by reducing postoperative nausea and vomiting, and whether avoidance should become part of a routine clinical management strategy. Despite some controversy, the greatest strength of evidence suggests that avoidance of nitrous oxide may be justified as a pre-emptive perioperative strategy as part of a multimodal approach to postoperative nausea and vomiting, especially in those patients known to have a higher baseline risk.

Anaesthesia for day surgery

The Department of Health (DH) proposes that 75% of elective surgery should be performed as a day case procedure (NHS Plan 2000). To achieve this some modification of the traditional selection criteria may be required and careful thought given to the patient pathway, including the anaesthetic technique. Successful anaesthesia for day case surgery requires a balanced anaesthetic technique and multidisciplinary input which commences at booking, runs through preoperative assessment and continues to a nurse-led discharge. Suitable patients need to be selected (Digner 2007), prepared both physically and psychologically, undergo minimally invasive surgery with a suitable anaesthetic technique encompassing good pain relief and the avoidance of postoperative nausea and vomiting (PONV). Pain and PONV are the most common causes for a patient to require unplanned admission (Junger 2001).

When nitrous oxide is no laughing matter: nitrous oxide and pediatric anesthesia

Although often felt to be relatively innocuous, nitrous oxide can have significant metabolic effects in settings of abnormal vitamin B12 and B12-related metabolism in children. These conditions can be genetic or environmental. Symptoms may not appear until days to weeks after exposure to nitrous oxide. Although overt genetic diseases are relatively uncommon, the implications of nitrous oxide interactions with much more frequent but less symptomatically obvious single nucleotide polymorphisms are potentially more concerning. In addition, nitrous oxide can have direct and differing neurotoxic effects on both immature and aged brain, the clinical impact of which remains undetermined.