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

Beyond surgery: Repurposing anesthetics for treatment of central nervous system disorders

The development of new drugs is a complex, expensive, and time-consuming process, often fraught with a high likelihood of failure. Amid these obstacles, drug repurposing, which identifies new therapeutic applications for already existing medications, offers a more economical and time-saving approach, particularly in the challenging field of neurological and psychiatric disorders. This narrative review explores both preclinical and clinical studies to examine the potential of anesthetics such as ketamine, nitrous oxide, isoflurane, sevoflurane, propofol, dexmedetomidine, and sodium oxybate in treating central nervous system disorders. Various research highlights the potential of anesthetics to provide rapid antidepressant effects, enhance learning and memory, improve synaptic plasticity, and offer neuroprotective benefits, demonstrating promise for treating depression, post-traumatic stress disorder, cognitive decline, traumatic brain injury, and neurodegenerative disorders. Anesthetics appear to alleviate symptoms in neurological conditions, likely by modulating GABAergic and glutamatergic pathways. However, challenges such as dose-dependent neurotoxicity, variability in preclinical and clinical outcomes, as well as environmental concerns remain significant issues. Future research is essential to optimize dosing strategies, ensure long-term safety, and gain a deeper understanding of the precise mechanisms of action. The concept of anesthetics' repurposing presents a unique solution to tackle the challenges in neurological and psychiatric therapy by providing a platform for the development of new and improved therapies.

More than just joy: A qualitative analysis of participant experiences during nitrous oxide sedation

BACKGROUND

Nitrous oxide use is shifting from general anesthesia to sedation and pain control. Interest in novel uses of nitrous oxide in psychiatry is also growing. Thus, understanding the consequences of using nitrous oxide remains relevant. Previous quantitative research might not have fully captured the whole spectrum of nitrous oxide, whereas qualitative analysis can provide a more comprehensive description. This qualitative study aims to describe the subjective experiences of nitrous oxide use in healthy volunteers who have no prior history of recreational substance misuse.

METHODS

Twenty healthy male volunteers inhaled 50% nitrous oxide for 20 min. Females were excluded due to higher incidence of nausea with nitrous oxide. Afterwards, all participants answered an open-ended question about their experiences during sedation. The answers were then analyzed with inductive qualitative content analysis to identify emergent subcategories, categories, and overarching themes.

RESULTS

We identified two themes: nitrous oxide is mind-altering and produces sensory overload. The mind-altering properties were represented by dreamlike states and heightened emotions. Dreamlike states comprised changes in consciousness and scary, bizarre, or transcendental dreams. Pleasant dreams were not reported. Heightened emotions included euphoria, anxiety, and fear of losing control. Sensory overload consists of distorted perception, bodily sensations, and a heightened sense of surroundings.

CONCLUSIONS

Experiences under nitrous oxide sedation are extremely variable and not always pleasant. These findings can improve our understanding of the likes/dislikes of patients undergoing nitrous oxide sedation. Further qualitative studies should focus on the experiences of other groups, such as children or women in labor.

Does nitrous oxide addiction exist? An evaluation of the evidence for the presence and prevalence of substance use disorder symptoms in recreational nitrous oxide users

BACKGROUND

Prevalence of nitrous oxide (N2 O) use appears to be increasing in numerous countries worldwide, and excessive use has been associated with physical and mental problems. Because there currently is no consensus whether N2 O has addictive potential, we aimed to evaluate the evidence for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in N2 O users.

ANALYSIS

A literature search was conducted to assess the evidence for the presence of any of the 11 DSM-5 SUD symptoms in N2 O users and the prevalence experiencing those symptoms. A substantial part of the studied N2 O users use more than intended (i.e. 46% to 98%) and spend a substantial amount of time using N2 O. At least some of the studied N2 O users experience interpersonal problems (i.e. 13% to 80%) and use N2 O in risky situations, such as driving under the influence. Evidence for the other criteria is either insufficient or inconclusive.

CONCLUSIONS

The literature base for the presence and prevalence of DSM-5 substance use disorder (SUD) symptoms in nitrous oxide (N2 O) users is limited and largely consists of qualitative studies and case studies, but it provides consistent evidence for the presence of at least four SUD criteria in heavy N2 O users. N2 O could well be addictive and should be treated as a potentially addictive substance until systematic assessments can provide evidence-based guidance to users, healthcare professionals and legislators.

Comparative Assessment of Anxiety during Inferior Alveolar Nerve Block under Nitrous Oxide + Oxygen and Oxygen Inhalation Sedation in Children Aged 3-12 Years: A Randomized Clinical Trial

Aim

A comparative evaluation of children's anxiety with the use of nitrous oxide-oxygen (N2O-O2) inhalation sedation during the administration of inferior alveolar nerve block (IANB).

Materials and methodology

A total of 60 children between 3 and 12 years of age, with Frankl's behavior rating of 2-3 requiring IANB for any dental procedure were enrolled in this randomized clinical study. Group I (n = 30) received N2O and oxygen inhalation sedation at a concentration in the range of 25-50%, whereas group II (n = 30) received 100% O2 as a placebo. The physiological parameters like pulse rate, respiration, blood pressure, and O2 saturation were measured at the baseline, intraoperatively [during and after administration of local anesthesia (LA)] and postoperatively after the termination of the gases in both groups. The sedation level was measured intraoperatively (before administration of LA) using the Ramsay Sedation Score (RSS). The discomfort and anxiety were measured at the baseline, intraoperatively, and postoperatively using the Face, Legs, Activity, Cry, Consolability (FLACC) behavior scale. The data were evaluated using the statistical software International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS) statistics 20.0.

Results

There was a significant difference in the FLACC scores between the two groups, intraoperatively (p-value-0.002), and postoperatively (p-value-0.049). The mean of the RSS for group I was 2.80 + 1.03, and for group II was 1.80 + 0.81. All the physiological parameters recorded were within the normal range.

Conclusion

The use of N2O-O2 inhalation improved the anxiety levels in children while receiving the IANB and showed significant anxiolytic and sedative effects as compared to O2 inhalation.

Clinical significance

Nitrous oxide-oxygen (N2O-O2) inhalation can be used as a nonpharmacological behavior management adjunct for invasive treatments for children with utmost comfort for the child.

How to cite this article

Thomas PS, Dave BH, Shah DJ, et al. Comparative Assessment of Anxiety during Inferior Alveolar Nerve Block under Nitrous Oxide + Oxygen and Oxygen Inhalation Sedation in Children Aged 3-12 Years: A Randomized Clinical Trial. Int J Clin Pediatr Dent 2023;16(1):30-36.

Comparative Evaluation of Changes in Physiological and Psychomotor Effects in Pediatric Patients during Extraction under Different Concentrations of Nitrous Oxide-Oxygen Inhalation Sedation

Introduction:

Nonpharmacological behavioral management techniques are routinely used to create an environment that facilitates and builds a rapport between the child and the dentist to carry out procedures with minimal disruption. However, the discomfort associated with oral injections produces varying degrees of stress in all patients. Nitrous oxide (N₂O)–oxygen (O₂) inhalation sedation is one of the most widely used modalities for the management of fear and anxiety in children.

Objective:

The objective was to evaluate changes in physiological and psychomotor effects in pediatric patients during extraction under different concentrations of N₂O–O₂ inhalation sedation.

Materials and Methods:

A total of 300 healthy patients in the age range of 6–12 years (mean 8.9 years), who needed extraction of primary tooth, were included in the study. Pulse rate, SpO_2, blood pressure (BP), and temperature were recorded at baseline, 30% N₂O concentration, 50% N₂O concentration, and again postoperatively. In addition, anxiety levels and neuromuscular coordination were recorded at the respective intervals.

Results:

The results revealed a mean decrease in pulse rate and BP from baseline and an increase in temperature and O₂ saturation during the sedation procedure. The findings were statistically significant. Significant impairment of coordination and psychomotor ability was seen at each step. Anxiety had significantly reduced after the onset of sedation due to the anxiolytic effect of N₂O.

Conclusion:

N₂O–O₂ inhalation sedation under different concentrations reduces the anxiety of the patient and produces adequate sedation with vital signs within normal limits along with temporary impairment of psychomotor ability and coordination.

Rewarding Subjective Effects of the NMDAR Antagonist Nitrous Oxide (Laughing Gas) Are Moderated by Impulsivity and Depressive Symptoms in Healthy Volunteers

BACKGROUND

Nitrous oxide (N2O) is an anesthetic gas with both therapeutic and abuse potential. Because N2O is an NMDA receptor (NMDAR) antagonist, its effects are expected to resemble those of the prototypical NMDAR antagonist, ketamine. In this study, we examined the subjective rewarding effects of N2O using measures previously employed in studies of ketamine. We also tested for moderation of these effects by bipolar phenotype, depressive symptoms, and impulsivity.

METHODS

Healthy volunteers were randomly assigned to either 50% N2O (n = 40) or medical air (n = 40). Self-reported rewarding (liking and wanting), and alcohol-like effects were assessed pre-, peri- and post inhalation.

RESULTS

Effect sizes for the various rewarding/alcohol-like effects of N2O were generally similar to those reported in studies of moderate-dose ketamine. Impulsivity moderated the subjective reinforcing (liking) effects of inhaled gas, while depressive symptoms moderated motivational (wanting [more]) effects. However, depression and impulsivity had opposite directional influences, such that higher impulsivity was associated with higher N2O liking, and higher depression, with lower N2O wanting.

CONCLUSION

To the extent that static (versus longitudinal) subjective rewarding effects are a reliable indicator of future problematic drug use, our findings suggests that impulsivity and depression may predispose and protect, respectively, against N2O abuse. Future studies should examine if these moderators are relevant for other NMDAR antagonists, including ketamine, and novel ketamine-like therapeutic and recreational drugs. Similarities between moderate-dose N2O and moderate-dose ketamine in the intensity of certain subjective effects suggest that N2O may, at least to some extent, serve as substitute for ketamine as a safe and easily implemented experimental tool for probing reward-related NMDAR function and dysfunction in humans.

Does environmental exposure to the greenhouse gas, N2O, contribute to etiological factors in neurodevelopmental disorders? A mini-review of the evidence

BACKGROUND

Neurodevelopmental disorders are increasing in prevalence worldwide. Previous work suggests that exposure to the environmental air pollutant and greenhouse gas - nitrous oxide (N₂O) - may be an etiological factor in neurodevelopmental disorders through the targeting of several neural correlates.

METHODOLOGY

While a number of recent systematic reviews have addressed the role of general anesthesia in the surgical setting and neurodevelopmental outcomes, a narrative mini-review was conducted to first define and characterize the relevant variables (i.e., N₂O, attention-deficit hyperactivity disorder [ADHD] and autism spectrum disorders [ASD]) and their potential interactions into a coherent, hypothesis-generating work. The narrative mini-review merges basic principles in environmental science, anesthesiology, and psychiatry to more fully develop the novel hypotheses that neurodevelopmental impairment found in conditions like ADHD and ASD may be due to exposure to the increasing air pollutant, N₂O.

RESULTS

The results of the present mini-review indicate that exposure to N₂O, even at non-toxic doses, may modulate central neurotransmission and target many neural substrates directly implicated in neurodevelopmental disorders, including the glutamatergic, opioidergic, cholinergic, and dopaminergic systems. Epidemiological studies also indicate that early and repeated exposure to general anesthesia, including N₂O, may contribute to later adverse neurodevelopmental outcomes in children.

CONCLUSIONS

The current evidence and subsequent hypotheses suggest that a renewed interest be taken in the toxicological assessment of environmental N₂O exposure using validated biomarkers and psychiatric endpoints. Given the relevance of N₂O as a greenhouse gas, societies may also wish to engage in a more robust monitoring and reporting of N₂O levels in the environment for climactic benefit as well.

The drug effects questionnaire: psychometric support across three drug types

RATIONALE

The Drug Effects Questionnaire (DEQ) is widely used in studies of acute subjective response (SR) to a variety of substances, but the format of the DEQ varies widely across studies, and details of its psychometric properties are lacking. Thus, the field would benefit from demonstrating the reliability and validity of the DEQ for use across multiple substances.

OBJECTIVE

The current study evaluated the psychometric properties of several variations of DEQ items, which assessed the extent to which participants (1) feel any substance effect(s), (2) feel high, (3) like the effects, (4) dislike the effects, and (5) want more of the substance using 100-mm visual analog scales.

METHODS

DEQ data from three placebo-controlled studies were analyzed to examine SR to amphetamine, nicotine, and alcohol. We evaluated the internal structure of the DEQ for use with each substance as well as relationships between scale items, measures of similar constructs, and substance-related behaviors.

RESULTS

Results provided preliminary psychometric support for items assessing each DEQ construct (feel, high, dislike, like, and more).

CONCLUSIONS

Based on the study results, we identify several common limitations of extant variants of the DEQ and recommend an improved version of the measure. The simplicity and brevity of the DEQ combined with its promising psychometric properties support its use in future SR research across a variety of substances.

Sex and gender aspects in anesthetics and pain medication

The influence of sex and gender on anesthesia and analgesic therapy remains poorly understood, nevertheless the numerous physiological and pharmacological differences present between men and women. Although in anesthesiology sex-gender aspects have attracted little attention, it has been reported that women have a greater sensitivity to the non-depolarizing neuroblocking agents, whereas males are more sensitive than females to propofol. It has been suggested that men wake slower than women after general anesthesia and have less postoperative nausea and vomiting. Sexual hormones seem to be of importance in the onset of differences. Nevertheless, in the last years, sex-gender influences on pain and analgesia have become a hot topic and data regarding sex-gender differences in response to pharmacologic and non-pharmacologic pain treatments are still scanty, inconsistent, and non-univocal. In particular, females seem to be more sensitive than males to opioid receptor agonists. Women may experience respiratory depression and other adverse effects more easily if they are given the same doses as males. Evidently, there is an obvious need for more research, which should include psychological and social factors in experimental preclinical and clinical paradigms in view of their importance on pain mechanism, in order to individualize analgesia to optimize pain relief.