Effects of information on the reinforcing, subjective, and psychomotor effects of nitrous oxide in healthy volunteers

The efficacy and tolerability of inhaled nitrous oxide in major depressive disorder: a systematic review and meta-analysis

BACKGROUND

Nitrous oxide (N2O) has been initially confirmed by clinical trials to benefit to patients with major depressive disorder (MDD). However, there needs to be a meta-analysis to compare the efficacy and tolerability of N2O in MDD.

METHODS

PubMed, EMBASE, and Cochrane Library were searched for relevant studies up to Jan 1st, 2023. The meta-analysis mainly compared the outcome of the change in depression severity scores, response, remission, and adverse events in patients with MDD receiving 50% N2O and placebo.

RESULTS

Four studies with 133 patients were eventually identified. We found that the N2O group and control group showed an overall significant difference in the change in depression severity score for patients at 2 h, 24 h, and 2 weeks or more (2 h, SMD =  - 0.64, 95% CI - 0.01 to - 0.28, p < 0.0001) (24 h, SMD =  - 0.65, 95% CI - 1.01 to - 0.29, p < 0.0001) (2 weeks, SMD =  - 0.76, 95% CI - 1.16 to - 0.36, p < 0.0001). For the response and remission rate, the long-term effect of N2O was also statistically significant (for the response, RR = 2.33, 95% CI 1.23 to 4.44, p = 0.01) (for the remission, RR = 4.68, 95% CI 1.49 to 14.68, p = 0.008). For safety outcomes, patients treated with N2O had higher odds of nausea or vomiting (RR = 10.15, 95% CI 1.96 to 52.59, p = 0.009).

CONCLUSION

Our study suggested that N2O has a rapid and long-lasting antidepressant effect in patients with MDD. However, the efficacy of lower or titrated concentration of N2O should be further investigated.

Lack of sex differences to the subjective effects of nitrous oxide in healthy volunteers

BACKGROUND

Although numerous studies have assessed subjective effects of nitrous oxide, few studies have analyzed for sex differences. Since sex differences have been reported in subjective effects of several drugs such as opioids, nicotine and alcohol, we sought to determine if sex modulates the subjective effects of the inhalant, nitrous oxide, in healthy volunteers.

METHODS

Thirty-eight females and seventy-two males from nine studies that were conducted in our laboratory were included in this retrospective analysis. All experimental studies utilized randomized, placebo-controlled, repeated measures designs in which subjects inhaled 30% nitrous oxide in oxygen and 100% oxygen (placebo). Dependent measures in this analysis were subjective effects measured at baseline and 15 min into the inhalation period.

RESULTS

Nitrous oxide produced a number of subjective effects, including those that could be considered abuse liability-related ("elated," "having pleasant thoughts," drug liking), but sex did not modulate these effects.

CONCLUSIONS

Females and males showed similar subjective responses to 30% nitrous oxide. Future prospective studies might assess other concentrations, other measures (choice, analgesic response), and other inhaled general anesthetics to more comprehensively characterize the role of sex in response to inhalants.

A survey of inhalational anaesthetic abuse in anaesthesia training programmes

This study aims to assess the prevalence and outcomes of inhalational anaesthetic abuse among anaesthesia training programmes. Online surveys were completed by chairpersons of academic anaesthesia training programmes in the United States. The response rate was 84% (106/126 programmes). Twenty-two percent of the departments had had at least one incident of inhalational anaesthetic abuse. Forty-eight percent (15/31) of the persons abusing inhalational anaesthetics were sent for rehabilitation. Only 22% (7/31) of those found to be abusing inhalational anaesthetics were ultimately able to return successfully to anaesthesia practice with sustained recovery. The mortality rate among individuals found abusing inhalational anaesthetics was 26% (8/31). The majority of the anaesthesia departments (97/104, 93%) did not have any pharmacy accounting of inhalational anaesthetics. This is the first published survey of inhalational anaesthesia abuse. Inhalational anaesthetic abuse should be considered in at-risk individuals or those with a history of substance abuse. The concern about substance abuse is not unique to American anaesthetists. Countries around the world deal with similar substance abuse issues.

Preoperative dental anxiety and mood changes during nitrous oxide inhalation

BACKGROUND

An estimated 35 million Americans experience significant apprehension about dental procedures, while an additional 10 to 12 million are considered to be "dental phobic" and avoid needed dental care altogether. Nitrous oxide is a general anesthetic used at subanesthetic concentrations to reduce anxiety during dental procedures. The purpose of this study was to characterize mood changes during nitrous oxide inhalation in patients with different levels of preoperative dental anxiety.

METHODS

Forty-six patients who were to receive nitrous oxide during a dental procedure completed two anxiety scales. These patients were categorized into three groups: low anxiety, or LA, moderate anxiety, or MA, and high anxiety, or HA. They completed a visual analog scale of subjective effects before, during and after the dental procedure.

RESULTS

A number of visual analog ratings, the majority of which could be considered pleasant, increased during nitrous oxide administration. It is significant that this increase in pleasant mood occurred in the HA and MA groups to the same degree as it did in the LA group. Patients in the HA and MA groups had elevated preoperative visual analog ratings of "anxious" that were reduced during nitrous oxide administration to a level equivalent to that reported by patients who had low preoperative anxiety. Patients in the HA group also had elevated preoperative visual analog ratings of "having unpleasant thoughts" and "feel bad" compared with the LA group. These ratings were reduced in the HA group to a level equivalent to that reported by patients in the LA group.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Regardless of their preoperative anxiety level, patients experienced a number of mood-altering effects during nitrous oxide inhalation, the majority of which could be considered pleasant. Ratings of an unpleasant nature decreased markedly in patients with high anxiety. These findings suggest that nitrous oxide may be an effective therapy in reducing patient anxiety during dental procedures.