Your next patient is a 65-year-old woman scheduled for a complex ventral hernia repair. According to a recent study, which of the following outcomes is MOST likely if you use a higher dose of nitrous oxide as an adjunct to the general anesthetic instead of no nitrous oxide?
- □ (A) Higher risk of intraoperative hypotension
- □ (B) Higher total dose of intraoperative vasopressors
- □ (C) Shorter length of stay in the postanesthesia care unit
The authors of a recent retrospective study sought to determine whether patients receiving intraoperative nitrous oxide as an adjunct to general anesthesia had a shorter PACU length of stay. This single-center study included 148,284 adults undergoing noncardiothoracic surgery with general anesthesia between May 2008 and December 2018. Exclusion criteria were an ASA Physical Status of V or VI, intensive care unit admission prior to surgery, and more than one surgical procedure within the previous month. Intraoperative use of nitrous oxide as an adjunct to general anesthesia at any time from induction to emergence was categorized as lower dose (median end-tidal concentration ≤13.15%) or higher dose (median end-tidal concentration >13.15%). The primary outcome was PACU length of stay. The risk of intraoperative hypotension and use of vasopressors were secondary outcomes.
“In summary, intraoperative use of nitrous oxide as an adjunct to general anesthesia was associated with a decreased PACU length of stay in a dose-dependent fashion.”
The study cohort consisted of 67,403 patients in the no nitrous oxide group, 40,441 patients in the lower-dose nitrous oxide group, and 40,440 patients in the higher-dose nitrous oxide group. The median (interquartile range) PACU length of stay was 176 (132-251) minutes in the no nitrous oxide group, 181 (137-252) minutes in the lower-dose nitrous oxide group, and 158 (120-216) minutes in the higher-dose nitrous oxide group. After adjusting for a priori defined confounders, both the lower-dose and higher-dose nitrous oxide groups had a shorter PACU length of stay, compared with the no nitrous oxide group. The adjusted difference for the unmatched cohort was –4.3 minutes (95% CI, –5.6 to –3.0) for the lower-dose group and –9.1 minutes (95% CI, –10.5 to –7.7) for the higher-dose group.
The authors also established propensity score-matched no nitrous oxide and higher-dose nitrous oxide groups (n = 39,441 in each group). When these groups were compared, PACU length of stay continued to be shorter in patients who received higher-dose nitrous oxide than in those who received no nitrous oxide (adjusted difference, –11.4 minutes [95% CI, –12.9 to –9.9]). The effect of higher-dose nitrous oxide on PACU length of stay was most evident in patients who underwent complex surgery and received intraoperative antiemetic therapy.
Patients in the higher-dose nitrous oxide group had a lower risk of both short and prolonged duration of intraoperative hypotension than those in the no nitrous oxide group (adjusted odds ratio, 0.85 [95% CI, 0.83-0.88] and 0.76 [95% CI, 0.73-0.80], respectively). Patients who received higher-dose nitrous oxide also had a lower total intraoperative dose of vasopressors than those who did not receive nitrous oxide (adjusted difference, –0.04 mg of norepinephrine equivalents [95% CI, –0.06 to –0.01]).
In summary, intraoperative use of nitrous oxide as an adjunct to general anesthesia was associated with a decreased PACU length of stay in a dose-dependent fashion. The effect of higher-dose nitrous oxide on shorter PACU length of stay was most pronounced in patients who underwent complex surgical procedures and received intraoperative antiemetics.
Answer: C
Leave a Reply
You must be logged in to post a comment.