Anaesthetic gases and the environment: Is it time for a rethink?

BACKGROUND

General anaesthesia is in common use for patients undergoing surgical procedures, with the option of both inhalational and intravenous anaesthetic techniques. Anaesthetic gases are often excluded from discussions on sustainable healthcare delivery, despite being a significant contributor to the overall environmental impact of healthcare services.

METHODS

A literature review was carried out on previously published papers on the impact anaesthetic gases have on our environment and at ways to reduce their impact in current anaesthetic practice. The aim was to write a narrative review detailing the areas of concern as well as the current clinical situation in the European setting.

SUMMARY/CONCLUSIONS

The two classes of inhaled anaesthetic agent most frequently used are nitrous oxide and volatile agents (most commonly sevoflurane, isoflurane and desflurane). Both are recognised greenhouse gases that contribute to climate change. Minor modifications in the use of anaesthetic gases can have a significant environmental impact. These modifications include avoiding nitrous oxide whenever possible, avoiding desflurane (and using sevoflurane instead), using low flow anaesthesia during maintenance, swapping volatile-based anaesthesia for a TIVA technique when clinically appropriate and considering the use of central neuraxial or regional anaesthesia in place of general anaesthesia when possible.

Nitrous oxide splurge in a tertiary health care center and its environmental impact: No more laughing stock

Background

Nitrous oxide has been an integral part of surgical anesthesia for many years in the developed world and is still used in developing countries such as India. The other main concerns in low-resource countries are the lack of an advanced anesthesia gas-scavenging system and modular surgical theatres. As a greenhouse gas that has been present in the atmosphere for more than 100 years and damages the ozone layer, nitrous oxide is three times worse than sevoflurane. Here, we conducted an observational study to quantify the annual nitrous oxide consumption and its environmental impact in terms of carbon dioxide equivalence in one of busiest tertiary health care and research centers in Northern India.

Methods

Data related to nitrous oxide expenditure' from the operation theatre and manifold complex of our tertiary care hospital and research center from 2018 to 2021 were collected monthly and analyzed. The outcomes were extracted from our observational study, which was approved by our institutional ethics board (INT/IEC/2017/1372 Dated 25.11.2017) and registered prospectively under the Central Registry (CTRI/2018/07/014745 Dated 05.07.2018).

Results

The annual nitrous oxide consumption in our tertiary care hospital was 22,081.00, 22,904.00, 17,456.00, and 18,392.00 m3 (cubic meters) in 2018, 2019, 2020, and 2021, respectively. This indicates that the environmental impact of nitrous oxide (in terms of CO2 equivalents) from our hospital in 2018, 2019, 2020, and 2021 was 13,016.64, 13,287.82, 10,289.94, and 10,841.24 tons, respectively.

Conclusion

This huge amount of nitrous oxide splurge is no longer a matter of laughter, and serious efforts should be made at every central and peripheral health center level to reduce it.

Analysis of the annual changes in dental institutions that claimed dental sedatives in Korea and the types of sedatives using health care big data

Background

Dentists make various efforts to reduce patients' anxiety and fear associated with dental treatment. Dental sedation is an advanced method that dentists can perform to reduce patients' anxiety and fear and provide effective dental treatment. However, dental sedation is different from general dental treatment and requires separate learning, and if done incorrectly, can lead to serious complications. Therefore, sedation is performed by a limited number of dentists who have received specific training. This study aimed to investigate the proportion of dentists who practice sedation and the main sedatives they use in the context of the Republic of Korea.

Methods

We used the customized health information data provided by the Korean National Health Insurance. We investigated the number of dental hospitals or clinics that claimed insurance for eight main sedatives commonly used in dental sedation from January, 2007 to September, 2019 at the Health Insurance Review and Assessment Service. We also identified the changes in the number of dental medical institutions by region and year and analyzed the number and proportion of dental medical institutions prescribing each sedative.

Results

In 2007, 302 dental hospitals prescribed sedatives, and the number increased to 613 in 2019. In 2007, approximately 2.18% of the total 13,796 dental institutions prescribed sedatives, increasing to 3.31% in 2019. In 2007, 168 institutions (55.6%) prescribed N₂O alone, and in 2019, 510 institutions (83.1%) made claims for it. In 2007, 76 (25.1%) hospitals made claims for chloral hydrate, but the number gradually decreased, with only 29 hospitals (4.7%) prescribing it in 2019. Hospitals that prescribed a combination of N₂O, chloral hydrate, and hydroxyzine increased from 27 (8.9%) in 2007 to 51 (9%) in 2017 but decreased to 38 (6.1%) in 2019. The use of a combination of N₂O and midazolam increased from 20 hospitals (6.6%) in 2007 to 51 hospitals (8.3%) in 2019.

Conclusion

While there is a critical limitation to the investigation of dental hospitals performing sedation using insurance claims data, namely exclusion of dental clinics providing non-insured treatments, we found that in 2019, approximately 3.31% of the dental clinics were practicing sedation and that N₂O was the most commonly prescribed sedative.

Reclamation intensifies the positive effects of warming on N2O emission in an alpine meadow

Climatic warming can alter grassland nitrous oxide (N₂O) emissions due to soil property alterations. However, how the reclamation affect grassland N₂O flux under warming conditions remains unclear in alpine meadow ecosystems. We conducted a long-term manipulative warming experiment in a natural alpine meadow and a cultivated grassland on the Qinghai-Tibetan Plateau to explore the separate and interactive effects of warming and reclamation on the soil N₂O emission flux. N₂O fluxes were measured under four treatments including control (CK), warming (W), reclamation (R) and warming under reclamation (WR) from August 2018 to July 2019. We measured the content of soil C, N nutrients and 5 enzymatic activities in 2018 and 2019. Correlation analysis and structural equation modeling were used to clarify how soil N availability and soil enzyme activities affect N₂O emission. Our results indicated that compared to the ambient conditions for the growing and non-growing seasons, soil N₂O flux was significantly increased 59.1% and 152.0% by warming and 28.4% and 142.4% by reclamation, respectively. Compared with W, WR significantly increased N₂O flux by 18.9% and 81.1% during the growing and non-growing seasons, respectively. Soil moisture was negatively correlated to enzymatic activity and N₂O flux. Both warming and reclamation promoted soil nitrification by increasing related enzymatic activities that acted to increase the N₂O flux. Reclamation resulted in a greater sensitivity of the activity of ammonia monooxygenase and hydroxylamine oxidoreductase to warming, thus enhancing the effects of warming on increasing the N₂O flux. Our research indicated that reclamation can additionally increase the effects of warming on N₂O emissions for alpine meadows. Therefore, excessive expansion of arable land should be avoided, and new reclamation sites should be planned scientifically, as warming is expected to intensify in the future.

Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors

Nitrous oxide (N₂ O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N₂ O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N₂ O to the climate neutral product N₂ . Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N₂ O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N₂ O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N₂ O removal in ambient, aqueous conditions.

Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors

Nitrous oxide (N2O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N2O to the climate neutral product N2. Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N2O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N2O removal in ambient, aqueous conditions.

Nitrous oxide occupational exposure in conscious sedation procedures in endoscopic ambulatories: a pilot retrospective observational study in an Italian hospital

SUMMARY

Introduction. Nitrous oxide (N2O) is widely used to induce sedation also outside of operating rooms; there is a chance of workplace exposures for the operators engaged in the outpatient use of nitrous oxide. The aim of this research is to assess nitrous oxide exposure in gastroenterology outpatient settings. Methods. We performed an observational study marked by N2O environmental testing in a gastroenterology outpatient care; environmental research was supported by biological monitoring with urinary N2O analysis in exposed operators. The research was conducted both without and using a collective security device (NIKI mask). Results. The study was rolled out in 10 sessions of day shift procedures, totaling 4105 samples. The average N2O concentration in the environment was 27.58 (SD 1.76) and 449.59 (SD 35.29), respectively with and without NIKI Mask; the distribution of gases in the environment under investigation was not homogeneous (Anovatest P=0.001). Biological testing revealed a substantial rise in urinary concentration of 8.97 (p=0.001) between the start and the end of the shift, and the use of the NIKI-mask was effective (p=.003). Discussion. The exposure levels reported exceed the limits of 50 ppm (Italy operating rooms threshold value) as well as the value of 25 ppm (NIOSH threshold-value), indicating a significant issue in the outpatient use of N2O. Technical measures are needed to contain the occupational risk from N2O exposure outside of operating rooms; for the exposure results detected in this research, it is also evident that workers exposed to N2O must be subject to adequate health surveillance accounting for this occupational risk.

Possible impact of the COVID-19 pandemic on the recreational use of nitrous oxide in the Paris area, France

INTRODUCTION

Recreational use of nitrous oxide (N₂O) is increasing in Western countries, including France. During the COVID-19 pandemic, some authors warned that recreational N₂O use could increase further as the supply of illicit drugs was impacted by various containment measures.

METHODS

We retrospectively analyzed N₂O exposures reported to the Paris Poison Control Center (France) from 2010/01/01 to 2021/04/15. The Poison Severity Score was used to grade severity.

RESULTS

During the study period, 93 cases of N₂O recreational exposures were reported (male/female ratio: 1.1; median age: 20.9 years range: [14.8-49.0]). The first case was reported in 2012, 84/93 (90%) and 65/93 (70%) were reported since 2019 and March 17^th 2020 (first lockdown in France) respectively. Most of the patients were symptomatic (88/93; 95%) and developed neurological symptoms (78/93; 84%). Among the fourteen patients who developed moderate to severe symptoms, eleven were reported after March 2020.

CONCLUSION

Despite a marked increase in recreational N₂O exposures during the COVID-19 pandemic, the exact impact of COVID-19 on this increase remains to be determined as it was observed from 2019.

Success rate of nitrous oxide-oxygen procedural sedation in dental patients: systematic review and meta-analysis

The aim of this systematic review was to determine the success rate of nitrous oxide-oxygen procedural sedation (NOIS) in dentistry. A systematic digital search was conducted for publications or reports of randomized controlled trials evaluating the clinical performance of NOIS. Abstracts of research papers were screened for suitability, and full-text articles were obtained for those who met the inclusion and exclusion criteria accordingly. The quality of the studies was assessed using the revised Cochrane risk-of-bias tool (RoB 2). A total of 19 articles (eight randomized clinical trials with parallel intervention groups and 11 crossover trials), published between May 1988 and August 2019, were finally selected for this review. The studies followed 1293 patients reporting NOIS success rates, with a cumulative mean value of 94.9% (95% CI: 88.8–98.9%). Thirteen trials were conducted on pediatric populations (1098 patients), and the remaining six were conducted on adults (195 patients), with cumulative efficacy rates of 91.9% (95% CI: 82.5–98.1%) and 99.9% (95% CI: 97.7–100.0%), respectively. The difference was statistically significant (P = 0.002). Completion of treatment and Section IV of the Houpt scale were the most used efficacy criteria. Within the limitations of this systematic review, the present study provides important information on the efficacy rate of NOIS. However, further well-designed and well-documented clinical trials are required and there is a need to develop guidelines for standardization of criteria and definition of success in procedural sedation. Currently, completion of treatment is the most used parameter in clinical practice, though many others also do exist at the same time. To maximize NOIS efficacy, clinicians should strictly consider appropriate indications for the procedure.

Nitrous oxide-induced predominantly motor neuropathies: a follow-up study

OBJECTIVES

Recreational nitrous oxide (N₂O) abuse is increasingly popular among youth. We report a systematic clinical, electrophysiological and biological follow-up of patients with neuropathy caused by N₂O.

METHODS

We retrospectively report seven patients with neuropathy attributed to N₂O abuse and their comprehensive follow-up. Demographic, toxicological, clinical, biological and electrophysiological data were collected at first and second examination. Functional data were collected at the last evaluation.

RESULTS

Seven patients aged 18-30, consuming more than 140 gas-filled balloons (one balloon is filled with approximately 8 g of N₂O) per week for over a month, developed a severe, predominantly motor, length-dependent, progressive neuropathy over 3 to 6 weeks. Two-thirds presented associated signs of myelopathy. Distal lower limbs motor deficit and ataxia led to moderate disability. Spinal cord imaging was frequently normal. Nerve conduction studies disclosed an almost exclusively motor axonal neuropathy affecting the lower limbs with active denervation. Homocysteine plasma level was systematically elevated, whereas cobalamin plasma levels were normal in almost all patients. At short-term follow-up after intoxication discontinuation, ataxia and motor deficit only partially resolved despite vitamin B12 supplementation, while active denervation and homocysteinemia decreased. At last follow-up (median 9.2 months, IQR 7.5-10.75), mean ONLS was 2.0 (IQR 2.0-2.0).

DISCUSSION

Young patients, with induced N₂O motor neuropathy remain disabled after 5 to 14.5 months of gas withdrawal, despite vitamin B12 supplementation. A longer follow-up is needed to fully appraise the severity of these toxic neuropathies.

Drug-Induced Peripheral Neuropathy: Diagnosis and Management

Peripheral neuropathy comes in all shapes and forms and is a disorder which is found in the peripheral nervous system. It can have an acute or chronic onset depending on the multitude of pathophysiologic mechanisms involving different parts of nerve fibers. A systematic approach is highly beneficial when it comes to cost-effective diagnosis. More than 30 causes of peripheral neuropathy exist ranging from systemic and auto-immune diseases, vitamin deficiencies, viral infections, diabetes, etc. One of the major causes of peripheral neuropathy is drug induced disease, which can be split into peripheral neuropathy caused by chemotherapy or by other medications. This review deals with the latest causes of drug induced peripheral neuropathy, the population involved, the findings on physical examination and various workups needed and how to manage each case.

The relationship between early administration of morphine or nitrous oxide gas and PTSD symptom development

BACKGROUND

Posttraumatic Stress Disorder (PTSD) is a debilitating mental health disorder. Certain drugs, such as morphine and nitrous oxide gas (N₂O), are administered to individuals who just experienced a traumatic event (e.g., soldiers, injured civilians). It is therefore crucial to understand if they incidentally affect PTSD symptom development. Furthermore, such observations could pave the way for the development of pharmacological prevention strategies of PTSD.

METHODS

In this prospective population-based cohort study (n = 2,070), we examined the relationship between morphine or N₂O administration during childbirth, and subsequent childbirth-related PTSD symptoms at eight weeks postpartum. Pain during labour, prior PTSD symptoms, and birth medical severity were included as covariates in the analyses.

RESULTS

In women who developed PTSD symptoms, N₂O administration during childbirth predicted reduced PTSD symptom severity (p < .001, small to medium effect size). A similar tendency was observed for morphine, but was not significant (p < .065, null to small effect size). Both drugs predicted increased PTSD symptoms when combined with severe pain during labour.

LIMITATIONS

This study was observational, thus drug administration was not randomised. Additionally, PTSD symptoms were self-reported.

CONCLUSIONS

Peritraumatic N₂O administration may reduce subsequent PTSD symptom severity and thus be a potential avenue for PTSD secondary prevention. This might also be the case for morphine. However, the role of severe peritraumatic pain in context of drug administration deserves further investigation.

[Extra hospital use of nitrous oxide for recreational purposes]

Extra hospital use of nitrous oxide. FOR RECREATIONAL PURPOSESThe problematic recreational consumption of nitrous oxide is increasing in the adolescent population and its harms are little publicized and / or trivialized. This therefore represents a public health issue. In high doses, nitrous oxide becomes a dissociative anesthetic. It can lead to hypoxia and even asphyxia causing loss of consciousness. A chronic consumption is addictive and is characterized by megaloblastic anemia, dysfunction of the reproductive system and sensitivomotor myeloponeuropathy. After review of the previously cases, we note that the symptomatology is variable in intensity, presents a centripetal sensory impairment with dysesthesia and a deficit in the vibratory sense. Nitrous oxide alters vitamin B12 and increases the blood levels of homocysteine and methylmalonyl CoA. The magnetic resonance of the spinal cord shows abnormalities in the majority of cases. The treatment consisted of high doses of vitamin B12 for most of the cases described. In view of the good prognosis and the uncomplicated treatment, it is essential to quickly detect the impact of nitrous oxide on health.

Identifying a Personalized Anesthetic with Fuzzy PROMETHEE

Objective

During an anesthetic evaluation, the individual's medical history and overall fitness for the whole medical procedure should be carefully examined. The objective of this study was to apply a multi-criteria decision-making technique to determine the proper anesthetic agent for specific patients.

Methods

The fuzzy PROMETHEE (Preference Ranking Organization Method for Enrichment of Evaluations) method was applied to determine the most appropriate agent. Minimum alveolar concentration, blood:gas and oil:gas partition coefficients, onset of action, recovery time, duration, induction and maintenance doses, and washout time were used as the criteria for the analysis. After defining the values of each criteria, the criteria weights and the preference function were set, and finally the results for two different examples, one for general ranking and one for a specific individual were obtained.

RESULTS

The results show that nitrous oxide and xenon are among the preferred inhaled anesthetics in the ranking of the inhaled anesthetics, whereas midazolam was identified as the preferred injected agent. When the weights are selected according to a specific patient's condition, namely a 70-year-old woman to undergo an emergent laparoscopic appendectomy with comorbidities, including severe chronic obstructive pulmonary disease as a consequence of a life-long smoking habit, morbid obesity, and type II diabetes, the results changed significantly. In this case, desflurane and etomidate come first in the ranking of inhaled and injected anesthetics, respectively, while nitrous oxide is the least preferred anesthetic agent.

Conclusion

Expert opinion is always needed. Assigning weights to criteria and grading alternatives are the major challenges in multi-criteria decision-making studies. Fuzzy PROMETHEE is proposed to solve a multi-criteria decision-making problem in selecting a general anesthetic.

Oxygen Saturation and Pulse Rate Change in Children during Sedation with Oral Midazolam and Nitrous Oxide

OBJECTIVE

We aimed to examine if changes in oxygen saturation and pulse rate of pediatric patients during conscious sedation with midazolam and nitrous oxide are associated with child's behavior, midazolam dose, the type and duration of the treatment and demographic parameters.

STUDY DESIGN

This study was a retrospective chart review of consecutive pediatric patients, aged 2.5-12.5 years, who had undergone conscious sedation for dental treatment with oral midazolam (with or without nitrous oxide) between January 2011 and September 2015 at the Department of Pediatric Dentistry of Tel Aviv University. Oral midazolam was administered according to the patients' weight, either at 0.4 mg/kg, 0.5 mg/kg or at a maximum dose of 10 mg. In all cases pulse rate and oxygen saturation were monitored every 15 minutes during treatment, Results: 147 sedation sessions (82 of females and 65 of males) were included in the study. Sedation was successful in 80% of cases. Children with poor behavior scores had statistically significant different mean saturation levels, albeit within normal range, during the treatment (p<0.012) as well as a clinically significant higher mean pulse rate (p=0.0001), compared to children with good or excellent behavior scores. Treatment duration, the type of dental procedure or the patients' weight were not correlated with the change in oxygen saturation or pulse rate during the treatment.

CONCLUSIONS

Poor behavior of pediatric patients does not affect oxygen saturation, but it increases the pulse rate of children under sedation with midazolam and nitrous oxide.

From Dental to Mental Institutions: A Quadruple Threat of Nitrous-Oxide Administration Before and During Mental Asylum Admission

During the 19^th century, patients undergoing anesthesia for surgical and dental procedures were at risk of being given hypoxic or dilute nitrous oxide on four separate occasions. Primary and secondary saturation during surgery could account for two administrations of 100% nitrous-oxide anesthesia, while both diagnostic and therapeutic doses of dilute nitrous oxide were frequently administered in mental asylums.

Complications caused by nitrous oxide in dental sedation

The first clinical application of nitrous oxide (N₂O) was in 1844, by an American dentist named Horace Wells who used it to control pain during tooth extraction. Since then, N₂O has shared a 170-year history with modern dental anesthesia. N₂O, an odorless and colorless gas, is very appealing as a sedative owing to its anxiolytic, analgesic, and amnestic properties, rapid onset and recovery, and, in particular, needle-free application. Numerous studies have reported that N₂O can be used safely and effectively as a procedural sedation and analgesia (PSA) agent. However, N₂O can lead to the irreversible inactivation of vitamin B12, which is essential for humans; although rare, this can be fatal in some patients.

Drug-induced regulatory overcompensation has motivational consequences: Implications for homeostatic and allostatic models of drug addiction

Initial administration of 60% nitrous oxide (N₂O) at 21°C ambient temperature reduces core temperature (Tc) in rats, but tolerance develops to this hypothermic effect over several administrations. After additional N₂O administrations, a hyperthermic overcompensation (sign-reversal) develops such that Tc exceeds control levels during N₂O inhalation. This study investigated whether rats would employ behavioral thermoregulation to facilitate, or oppose, a previously acquired hyperthermic overcompensation during N₂O administration. To establish a hyperthermic sign-reversal, male Long-Evans rats (N = 12) received 10 3-h administrations of 60% N₂O while housed in a gas-tight, live-in, “inactive” thermal gradient (∼21°C). Following the tenth N₂O exposure, the thermal gradient was activated (range of 10–37°C), and rats received both a control gas session and a 60% N₂O test session in counterbalanced order. Mean Tc during N₂O inhalation in the inactive gradient was reliably hypothermic during the first exposure but was reliably hyperthermic by the tenth exposure. When subsequently exposed to 60% N₂O in the active gradient, rats selected a cooler Ta, which blunted the hyperthermic sign-reversal and lowered Tc throughout the remainder of the N₂O exposure. Thus, autonomic heat production effectors mediating the hyperthermia were opposed by a behavioral effector that promoted increased heat loss via selection of a cooler ambient temperature. These data are compatible with an allostatic model of drug addiction that suggests that dysregulatory overcompensation in the drugged-state may motivate behaviors (e.g., drug taking) that oppose the overcompensation, thereby creating a vicious cycle of escalating drug consumption and recurring dysregulation.

Data Build-up for the Construction of Korean Specific Greenhouse Gas Emission Inventory in Livestock Categories

Many studies on methane (CH₄) and nitrous oxide (N₂O) emissions from livestock industries have revealed that livestock production directly contributes to greenhouse gas (GHG) emissions through enteric fermentation and manure management, which causes negative impacts on animal environment sustainability. In the present study, three essential values for GHG emission were measured; i.e., i) maximum CH₄ producing capacity at mesophilic temperature (37°C) from anaerobically stored manure in livestock category (B_0,KM, Korean livestock manure for B₀), ii) EF_3(s) value representing an emission factor for direct N₂O emissions from manure management system S in the country, kg N₂O-N kg N⁻¹, at mesophilic (37°C) and thermophilic (55°C) temperatures, and iii) N_ex(T) emissions showing annual N excretion for livestock category T, kg N animal⁻¹ yr⁻¹, from different livestock manure. Static incubation with and without aeration was performed to obtain the N₂O and CH₄ emissions from each sample, respectively. Chemical compositions of pre- and post-incubated manure were analyzed. Contents of total solids (% TS) and volatile solid (% VS), and the ratio of carbon to nitrogen (C/N) decrease significantly in all the samples by C-containing biogas generation, whereas moisture content (%) and pH increased after incubation. A big difference of total nitrogen content was not observed in pre- and post-incubation during CH₄ and N₂O emissions. CH₄ emissions (g CH₄ kg VS⁻¹) from all the three manures (sows, layers and Korean cattle) were different and high C/N ratio resulted in high CH₄ emission. Similarly, N₂O emission was found to be affected by % VS, pH, and temperature. The B_0,KM values for sows, layers, and Korean cattle obtained at 37°C are 0.0579, 0.0006, and 0.0828 m³ CH₄ kg VS⁻¹, respectively, which are much less than the default values in IPCC guideline (GL) except the value from Korean cattle. For sows and Korean cattle, N_ex(T) values of 7.67 and 28.19 kg N yr⁻¹, respectively, are 2.5 fold less than those values in IPCC GL as well. However, N_ex(T) value of layers 0.63 kg N yr⁻¹ is very similar to the default value of 0.6 kg N yr⁻¹ in IPCC GLs for National greenhouse gas inventories for countries such as South Korea/Asia. The EF_3(s) value obtained at 37°C and 55°C were found to be far less than the default value.

Trends and Projected Estimates of GHG Emissions from Indian Livestock in Comparisons with GHG Emissions from World and Developing Countries

This study presents trends and projected estimates of methane and nitrous oxide emissions from livestock of India vis-à-vis world and developing countries over the period 1961 to 2010 estimated based on IPCC guidelines. World enteric methane emission (EME) increased by 54.3% (61.5 to 94.9 ×10⁹ kg annually) from the year 1961 to 2010, and the highest annual growth rate (AGR) was noted for goat (2.0%), followed by buffalo (1.57%) and swine (1.53%). Global EME is projected to increase to 120×10⁹ kg by 2050. The percentage increase in EME by Indian livestock was greater than world livestock (70.6% vs 54.3%) between the years 1961 to 2010, and AGR was highest for goat (1.91%), followed by buffalo (1.55%), swine (1.28%), sheep (1.25%) and cattle (0.70%). In India, total EME was projected to grow by 18.8×10⁹ kg in 2050. Global methane emission from manure (MEM) increased from 6.81 ×10⁹ kg in 1961 to 11.4×10⁹ kg in 2010 (an increase of 67.6%), and is projected to grow to 15×10⁹ kg by 2050. In India, the annual MEM increased from 0.52×10⁹ kg to 1.1×10⁹ kg (with an AGR of 1.57%) in this period, which could increase to 1.54×10⁹ kg in 2050. Nitrous oxide emission from manure in India could be 21.4×10⁶ kg in 2050 from 15.3×10⁶ kg in 2010. The AGR of global GHG emissions changed a small extent (only 0.11%) from developed countries, but increased drastically (1.23%) for developing countries between the periods of 1961 to 2010. Major contributions to world GHG came from cattle (79.3%), swine (9.57%) and sheep (7.40%), and for developing countries from cattle (68.3%), buffalo (13.7%) and goat (5.4%). The increase of GHG emissions by Indian livestock was less (74% vs 82% over the period of 1961 to 2010) than the developing countries. With this trend, world GHG emissions could reach 3,520×10⁹ kg CO₂-eq by 2050 due to animal population growth driven by increased demands for meat and dairy products in the world.

Nitrous oxide effect on relieving anxiety and pain in parturients under spinal anesthesia for caesarean section

Background:

Anxiety is an unpleasant experience that may have adverse effects on the process of anesthesia, cesarean delivery, recovery period and postoperative pain. Anxiety can also affect maternal satisfaction of the medical cares that provided by the medical team.

Objectives:

To compare the effects of inhalational 50% nitrous oxide (N₂O) with oxygen on reducing anxiety and pain in parturients who have undergone caesarean section under spinal anesthesia.

Patients and Methods:

In this double-blind clinical trial, 56 primigravid parturients were randomly assigned into two groups according to the operating list schedule. The experimental group received inhalational 50% N₂O three minutes before spinal anesthesia to the end of delivery. The control group received only oxygen. Flow meters were covered by a dark shield and monitored by an experienced nurse anesthetist. Pain and anxiety of patients were measured using visual analogue scale (VAS) by another nurse who was neither involved in the anesthetic process nor aware of the participants' allocation and inhalation agents. Data regarding sedation level, ephedrine use, nausea, vomiting, and neonate Apgar score were recorded as well.

Results:

Overall mean ± SD of anxiety VAS scores was 1.77 ± 1.5 in the experimental group and 3.12 ± 1.73 in the control groups (P = 0.003). The mean ± SD of pain VAS scores of the experimental and control groups were 0.82 ± 1.5 and 1.64 ± 1.45, respectively (P = 0.042). No significant differences were seen regarding blood oxygen saturation, neonate Apgar scores, total used ephedrine, operation time, delivery time, nausea, and vomiting between the two studied groups.

Conclusions:

Inhalation of 50% N₂O can significantly decrease anxiety (without clinically significant side effects) compared with O₂ inhalation in parturients who have undergone caesarean section under spinal anesthesia.

The effects of nitrous oxide on controlled hypotension during low flow anesthesia

BACKGROUND AND OBJECTIVES

We investigated the effect of Nitrous Oxide (N2O) on controlled hypotension in low-flow isoflurane-dexmedetomidine anesthesia in terms of hemodynamics, anesthetic consumption, and costs.

METHODS

We allocated forty patients randomly into two equal groups. We then maintained dexmedetomidine infusion (0.1 μg.kg-1.min-1) for 10 minutes. Next, we continued it until the last 30 minutes of the operation at a dose of 0.7 μg.kg(-1).hour(-1). We administered thiopental (4-6 mg. kg(-1)) and 0.08-0.12 mg.kg(-1) vecuronium bromide at induction for both groups. We used isoflurane (2%) for anesthesia maintenance. Group N received a 50% O2-N2O mixture and Group A received 50% O -air mixture as carrier gas. We started low-flow anesthesia (1 L.min(-1)) after a 10-minute period of initial high flow (4.4 L.min(-1)). We recorded values for blood pressure, heart rate, peripheral O2 saturation, inspiratory isoflurane, expiratory isoflurane, inspiratory O2, expiratory O2, inspiratory N2O, expiratory N2O, inspiratory CO2, CO2 concentration after expiration, Minimum Alveolar Concentration. In addition, we determined the total consumption rate of fentanyl, dexmedetomidine and isoflurane as well as bleeding.

RESULTS

In each group the heart rate decreased after dexmedetomidine loading. After intubation, values were higher for Group A at one, three, five, 10, and 15 minutes. After intubation, the patients reached desired hypotension values at minute five for Group N and at minute 20 for group A. MAC values were higher for Group N at minute one, three, five, 10, and 15 (p < 0.05). FiO2 values were high between minute five and 60 for Group A, while at minute 90 Group N values were higher (p < 0.05). Fi Iso (inspiratuvar isofluran) values were lower in Group N at minute 15 and 30 (p < 0.05).

CONCLUSION

By using dexmedetomidine instead of nitrous oxide in low flow isoflurane anesthesia, we attained desired MAP levels, sufficient anesthesia depth, hemodynamic stability and safe inspiration parameters. Dexmedetomidine infusion with medical air-oxygen as a carrier gas represents an alternative anesthetic technique.

The effects of xenon and nitrous oxide gases on alcohol relapse

BACKGROUND

In recent years, the glutamate theory of alcoholism has emerged as a major theory in the addiction research field and N-methyl-d-aspartate (NMDA) receptors have been shown to play a major role in alcohol craving and relapse. The NMDA receptors are considered as the primary side of action of the anesthetic gases xenon (Xe) and nitrous oxide (N2 O). Despite the rapid on/off kinetics of these gases on the NMDA receptor, a brief gas exposure can induce an analgesic or antireward effect lasting several days. The aim of this study was to examine the effect of both Xe and N2 O on alcohol-seeking and relapse-like drinking behavior (measured as the alcohol deprivation effect) in Wistar rats.

METHODS

We used 2 standard procedures-the alcohol deprivation model with repeated deprivation phases and the cue-induced reinstatement model of alcohol seeking-to study the effect of 2 brief gas exposures of either Xe, N2 O, or control gas on relapse-like drinking and alcohol-seeking behavior.

RESULTS

Here, we show that exposure to Xe during the last 24 hours of abstinence produced a trend toward reduced ethanol intake during the first alcohol re-exposure days. In addition, Xe gas exposure significantly decreased the cue-induced reinstatement of alcohol-seeking behavior. N2 O had no effect on either behavior.

CONCLUSIONS

Xe reduces alcohol-seeking behavior in rats and may therefore also interfere with craving in human alcoholics.

Reexamination of the Direct Electrochemical Reduction of S-Nitrosothiols

We report here on the electrochemical reduction of S-nitrosothiol species (RSNO). Nitric oxide (NO) is the reported common product from electrochemically reduced RSNOs at physiological pH. However, studies here at pH 7.4 show that during the reduction of RSNOs (-0.6 V to -0.9 V, vs. Ag/AgCl), no significant amount of NO is detected. Gas analysis suggests RSNO are reduced to nitrous oxide (N2O) at pH 7.4 and can only be converted back to NO at more oxidizing voltages. Interestingly, at pH 4.0, a direct one-electron reduction of RSNOs appears to occur and generates significant amounts of NO from RSNO species.

Clinical and MRI manifestations of nitrous oxide induced vitamin B12 deficiency: A case report

A 50 year-old man was referred with history of acute ataxia and lower extremity paresthesia 10 days after general anesthesia with nitrous oxide. Cervical MRI showed long hypersignal lesion in posterior segment of the cord. Blood analysis revealed vitamin B12 deficiency. Nitrous oxide-induced myelopathy should be considered in patients who develop acute neurological manifestation after general anesthesia. It is recommended for physicians to think about symptoms and signs of B12 deficiency when evaluating patients in postoperative visits.