Evidence of addiction by anesthesiologists as documented by hair analysis

Electromembrane extraction of drugs of abuse and prescription drugs from micropulverized hair

Hair analysis can provide chronological insights into past drug use for months to years after drug administration. In comparison to analyses from other biological matrices, such as blood and urine, sample pretreatment is often tedious and not environmental friendly. In this study, we present a more environmental friendly approach to hair analysis using micropulverized hair and electromembrane extraction for the efficient extraction of 15 drugs of abuse, prescription drugs, and metabolites from hair. The optimized extraction method, involving micropulverization, demonstrated comparable yields to the standard approach of cutting and overnight incubation. A 15-min extraction method using a commercial electromembrane extraction prototype was developed and validated according to forensic guidelines, using only 10 µL of organic solvent per sample. The final method, employing HPLC-MS-MS with a biphenyl column, exhibited good linearity, precision, and sensitivity. An AgreePrep assessment comparing the environmental impact of our method with the standard routine method, involving overnight incubation and conventional liquid-liquid extraction, was conducted. This is the first time micropulverized hair has been subjected to electromembrane extraction.

Abuse potential of fentanyl and fentanyl analogues

Introduction

In this perspective review, we evaluated the clinical management of fatal fentanyl overdose in several routes of administration, concentrating on both legally prescribed and illegally produced formulations.

Methods

A literature search was conducted on Web of Science, PubMed, and Google Scholar databases, using the following keywords: fentanyl, illicit fentanyl, deaths, misuse, abuse, and naloxone. We included only articles whose abstracts were available in English. All articles were screened using their abstracts to determine their relevance to the current review.

Results

The gold standard for treating both acute and chronic pain is fentanyl, but abuse of the drug has exploded globally since the late 2000s. Fentanyl abuse has been shown to frequently result in serious harm and even death.

Conclusion

By educating patients and physicians, making rescue kits easily accessible, developing vaccines to prevent opioid addiction, and perhaps even creating new tamper-resistant fentanyl formulations, it may be possible to prevent fentanyl misuse, therapeutic errors, and the repercussions that follow.

Risk of mortality and suicide associated with substance use disorder among healthcare professionals: A systematic review and meta-analysis of observational studies

BACKGROUND

Previous studies have suggested that healthcare professionals may be susceptible to substance use disorders, and among the medical specialties, anaesthesia providers appear to be overrepresented.

OBJECTIVE

We aimed to compare the prevalence of substance use-related mortality and suicides between anaesthesia and nonanaesthesia professionals.

DESIGN

Systematic review of observational studies with meta-analyses. We defined anaesthesia providers as any healthcare professionals belonging to the specialty, regardless of age and duration of employment. Other healthcare professionals served as the control group.

DATA SOURCES

Ovid Medline, EMBASE, Web of Science, Scopus, Scielo, LILACS and ProQuest databases up to March 2020.

RESULTS

Thirty-nine studies were included, 31 cross-sectional studies involving 13 819 participants and eight cohorts with a total 129 811 participants proved eligible. Results suggested a higher rate of drug-related mortality with odds ratio (OR) 2.69 [95% confidence interval (CI), 1.80 to 4.00; P < 0.001; I2 = 0%, P = 0.55; high-certainty evidence] and suicide (OR 2.18, 95% CI, 1.33 to 3.58; P = 0.002; I2 = 0%, P = 0.68; moderate-certainty evidence) for anaesthesia providers compared with other healthcare professionals.

CONCLUSION

High-to-moderate-certainty evidence shows that there is more than a two-fold increased rate of substance use-related mortality and suicide among anaesthesia providers compared with other healthcare professionals. Investigations examining substance abuse between healthcare professionals, with particular attention to working conditions and exposure are essential to further develop preventive strategies.

The Role of Alcohol Biomarkers in Detecting a Physician's COVID-19-Related Acute Stress Response: A Case Report

OBJECTIVES

Alcohol biomarkers are used to detect alcohol exposure in clinical and forensic settings. This includes professional health program (PHP) monitoring of healthcare workers in recovery from substance use disorders. Here we present the case of a physician whose positive alcohol biomarker test result was complicated by a traumatic stress response to frontline work during COVID-19.

METHODS

An anesthesiologist under PHP monitoring for substance use disorder and depression was interviewed extensively, urine and blood biomarkers were obtained, and longitudinal structured and semi-structured interviews related to anxiety, depression, posttraumatic stress, and cravings were used to monitor responses to the unanticipated death of a patient who succumbed to COVID-19.

RESULTS

After an initial positive ethylglucuronide (EtG) and ethylsulfate (EtS) toxicology test result, all subsequent testing was negative. Standardized assessments and clinical interviews provided documentation of a post-traumatic stress reaction. The physician described compulsive sanitizing of hands/arms and mask with highly concentrated ethanol-based products.

CONCLUSIONS

Inhalation of ethanol vapors is a possible explanation for the initial positive EtG/EtS results. To our knowledge, this case represents the highest reported levels of EtG/EtS likely due to workplace exposure. The importance of rapid intervention to thoroughly assess positive toxicology testing and its source(s) cannot be overstated, particularly as it relates to frontline healthcare workers during the pandemic. The PHP monitoring process provides an opportunity to promptly detect healthcare workers in distress, allowing for efficient connection to supportive resources and/or treatment when indicated, and possibly preventing escalation of symptoms or disease recurrence.

The Anesthesiologist's Armamentarium: From Recreation to Medication and Back

For millennia, mankind has sought a means of altering consciousness, often aided by naturally occurring elements. Psychotropic substances have been an integral part of spiritual, medicinal, and recreational aspects of life. The origin of anesthesiology stems directly from the use of recreational drugs; early inhaled anesthetics were first used as a means of entertainment. Hence, it is no surprise that many medications in the anesthesiologist's armamentarium are diverted for recreational use. In the 172 years following the first successful public demonstration of ether anesthesia, many drugs with abuse potential have been introduced to the practice of anesthesia. Although anesthesiologists are aware of the abuse potential of these drugs, how these drugs are obtained and used for recreational purposes is worthy of discussion. There are articles describing the historical and recreational use of specific drug classes. However, to the best of our knowledge, this is the first comprehensive review focusing on the breadth of drugs used by anesthesiologists.

Abuse of Licit and Illicit Psychoactive Substances in the Workplace: Medical, Toxicological, and Forensic Aspects

About one-third of adult life is spent in the workplace. The use of psychoactive substances is a major preventable cause of morbidity and mortality. The consumption of psychoactive substances during or outside working hours greatly increases the frequency and severity of labor accidents, as well as the workers’ poor general state of health and productivity, implying higher costs for enterprises. It is the responsibility of organizations to ensure the safety and health of their workers. These cannot be limited to traditional routine clinical exams, as other aspects also have an impact on health. Thus, prevention and intervention in the consumption of psychoactive substances (e.g., ethanol, opioids, central nervous system stimulants or depressants, hallucinogens, Cannabis derivatives, dissociative substances, and inhalants) in labor activity should be considered as an investment of organizations and not as a cost, in view of the professional, personal, and family advantages for workers and employers, with a potential impact on productivity, security, health, and quality of life at work. Despite the extensive literature on the subject, each article generally focuses on one or another aspect of a very specific nature, not tackling the problem in a holistic way by confronting clinical, safety, and legal issues. This article presents a reflection on the legal, laboratorial, clinical, ethical, forensic, and safety concerns related to the consumption of psychoactive substances in the workplace, and can be a cross-cutting contribution to occupational medicine, forensic medicine, and insurance medicine, as well as for entrepreneurs, lawyers, judges, workers, and technicians from the public and private sectors that develop projects in this area. This discussion is based on general principles established internationally and highlights the role of the occupational healthcare system and other decision-making actors in the prevention and supervision of workplace psychoactive consumption.

Determination of Selected Opiates in Hair Samples Using Microextraction by Packed Sorbent: A New Approach for Sample Clean-up

In this article the development and validation of an analytical method using microextraction by packed sorbent (MEPS) to determine tramadol (TRM), codeine (COD), morphine (MOR), 6-acetylcodeine (6-AC), 6-monoacetylmorphine (6-MAM) and fentanyl (FNT) in hair samples by gas chromatography coupled to tandem mass spectrometry (GC–MS-MS) is presented. The MEPS used a mixed mode sorbent, and the steps for sample cleanup were conditioning (three cycles of 250 μL of methanol and three cycles of 250 μL formic acid 2%); sample load (15 cycles of 150 μL); wash (150 μL of 3.36% formic acid); and elution (eight cycles of 100 μL of ammonium hydroxide 2.36% (in methanol)). Linearity was obtained from the lower limit of quantitation (LLOQ) up to 5 ng/mg, with all target compounds revealing determination coefficients >0.99. The LLOQs achieved were 0.01 ng/mg for TRM, COD and 6-AC, and 0.025 ng/mg for MOR, 6-MAM and FNT. The recoveries ranged from 74 to 90% (TRM), 51 to 59% (COD), 22 to 36% (MOR), 69 to 99% (6-AC), 53 to 61% (6-MAM) and 75 to 86% (FNT). Precision and accuracy revealed coefficients of variation typically below 15% and relative errors within a ±15% interval, respectively. This new approach has proven to be an excellent alternative to classic procedures, reducing the volumes of organic solvents required.

DARK Classics in Chemical Neuroscience: Fentanyl

Fentanyl rose to prominence as an alternative analgesic to morphine nearly 50 years ago; today, fentanyl has re-emerged as a dangerous recreational substance. The increased potency and analgesic effect of fentanyl are advantageous in the treatment of pain but are also responsible for the rise in unintentional opioid overdose deaths. In response to this crisis, fentanyl, its analogues, and even precursors are under heightened regulatory scrutiny. Despite this controversial history, derivatization of fentanyl has resulted in numerous synthetic analogues that provide valuable insights into opioid receptor binding and signaling events. In this review, the impact of fentanyl on chemical neuroscience is shown through its synthesis and properties, manufacturing, metabolism, pharmacology, approved and off-label indications, adverse effects, and the responsibility it has in the opioid epidemic.

Compulsive-Like Sufentanil Vapor Self-Administration in Rats

Opioid misuse is at historically high levels in the United States, with inhalation (ie, smoking and vaping) being one of the most common routes of consumption. We developed and validated a novel preclinical model of opioid self-administration by inhalation that does not require surgery and reliably produces somatic and motivational signs of dependence. Rats were trained to perform an operant response (nosepoke) to receive 10 s of vaporized sufentanil, a potent opioid, in 2 h daily sessions. Rats readily and concentration-dependently self-administered vaporized sufentanil. Rats exhibited a significant increase in responding for sufentanil when given the preferential μ-opioid receptor inverse agonist naloxone, suggesting the participation of μ-opioid receptors in the reinforcing properties of sufentanil vapor. Serum sufentanil concentrations significantly correlated with the number of sufentanil vapor deliveries. Rats that were given long access (LgA; 12 h/day) but not short access (ShA; 1 h/day) to vaporized sufentanil escalated their drug intake over time and exhibited both naloxone-precipitated somatic signs of opioid withdrawal and spontaneous withdrawal-induced mechanical hypersensitivity. After 6 months of forced drug abstinence, LgA rats returned to pre-escalation baseline levels of responding for sufentanil and mechanical sensitivity. Upon subsequent re-escalation (ie, after the return to extended access to sufentanil vapor), LgA rats again developed naloxone-precipitated somatic signs of withdrawal and spontaneous withdrawal-induced mechanical hypersensitivity. These findings demonstrate that the operant sufentanil vapor self-administration model has both face and construct validity and therefore will be useful for investigating the neurobiological basis of opioid addiction.

Fentanyl, fentanyl analogs and novel synthetic opioids: A comprehensive review

Deaths from opioid use are increasing in the US, with a growing proportion due to synthetic opioids. Until 2013, sporadic outbreaks of fentanyl and fentanyl analogs contaminating the heroin supply caused some deaths in heroin users. Since then, fentanyl has caused deaths in every state and fentanyl and its analogs have completely infiltrated the North American heroin supply. In 2014, the first illicit pills containing fentanyl, fentanyl analogs, and other novel synthetic opioids such as U-47700 were detected. These pills, which look like known opioids or benzodiazepines, have introduced synthetic opioids to more unsuspecting customers. As soon as these drugs are regulated by various countries, new compounds quickly appear on the market, making detection difficult and the number of cases likely underreported. Standard targeted analytical techniques such as GC-MS (gas chromatography mass spectrometry) and LC-MS/MS (liquid chromatography tandem mass spectrometry) can detect these drugs, but novel compound identification is aided by nontargeted testing with LC-HRMS (liquid chromatography high resolution mass spectrometry). Fentanyl, fentanyl analogs and other novel synthetic opioids are all full agonists of varying potencies at the μ-opioid receptor, leading to typical clinical effects of miosis and respiratory and central nervous system depression. Due to their high affinity for μ-opioid receptors, larger doses of naloxone are required to reverse the effects than are commonly used. Synthetic opioids are an increasingly major public health threat requiring vigilance from multiple fields including law enforcement, government agencies, clinical chemists, pharmacists, and physicians, to name a few, in order to stem its tide. This article is part of the Special Issue entitled 'Designer Drugs and Legal Highs.'

A review: Fentanyl and non-pharmaceutical fentanyls

BACKGROUND

Fentanyl and non-pharmaceutical fentanyls (NPFs) have been responsible for numerous outbreaks of overdoses all over the United States since the 1970s. However, there has been a growing concern in recent years that NPFs are contributing to an alarming rise in the number of opioid-related overdoses.

METHODS

The authors conducted a narrative review of the published and grey literature on fentanyl and NPFs in PubMed, Google Scholar, and Google using the following search terms: "fentanyl", "non-pharmaceutical fentanyl", "fentanyl analogs", "fentanyl laced heroin" and "fentanyl overdose". References from relevant publications and grey literature were also reviewed to identify additional citations for inclusion.

RESULTS

The article reviews the emergence and misuse of fentanyl and NPFs, their clinical pharmacology, and the clinical management and prevention of fentanyl-related overdoses.

CONCLUSIONS

Fentanyl and NPFs may be contributing to the recent rise in overdose deaths in the United States. There is an urgent need to educate clinicians, researchers, and patients about this public health threat.

Hair as a Biological Indicator of Drug Use, Drug Abuse or Chronic Exposure to Environmental Toxicants

In recent years hair has become a fundamental biological specimen, alternative to the usual samples blood and urine, for drug testing in the fields of forensic toxicology, clinical toxicology and clinical chemistry. Moreover, hair-testing is now extensively used in workplace testing, as well as, on legal cases, historical research etc. This article reviews methodological and practical issues related to the application of hair as a biological indicator of drug use/abuse or of chronic exposure to environmental toxicants. Hair structure and the mechanisms of drug incorporation into it are commented. The usual preparation and extraction methods as well as the analytical techniques of hair samples are presented and commented on. The outcomes of hair analysis have been reviewed for the following categories: drugs of abuse (opiates, cocaine and related, amphetamines, cannabinoids), benzodiazepines, prescribed drugs, pesticides and organic pollutants, doping agents and other drugs or substances. Finally, the specific purpose of the hair testing is discussed along with the interpretation of hair analysis results regarding the limitations of the applied procedures.

Non-opioid anesthetic drug abuse among anesthesia care providers: a narrative review

PURPOSE

The objective of this narrative review is to provide an overview of the problem of non-opioid anesthetic drug abuse among anesthesia care providers (ACPs) and to describe current approaches to screening, therapy, and rehabilitation of ACPs suffering from non-opioid anesthetic drug abuse.

SOURCE

We first performed a search of all literature available on PubMed prior to April 11, 2016. The search was limited to articles published in Spanish and English, and the following key words were used: anesthesiology, anesthesia personnel, AND substance-related disorders. We also searched Ovid MEDLINE^® databases from 1946-April 11, 2016 using the following search terms: anesthesiology OR anesthesia, OR nurse anesthetist OR anesthesia care provider OR perioperative nursing AND substance-related disorders.

PRINCIPAL FINDINGS

Despite an increased awareness of drug abuse among ACPs and improvements in preventive measures, the problem of non-opioid anesthetic drug abuse remains significant. While opioids are the most commonly abused anesthesia medications among ACPs, the abuse of non-opioid anesthetics is a significant cause of morbidity, mortality, and professional demise.

CONCLUSION

Early detection, effective therapy, and long-term follow-up help ACPs cope more effectively with the problem and, when possible, resume their professional activities. There is insufficient evidence to determine the ability of ACPs to return safely to anesthesia practice after rehabilitation, though awareness of the issue and ongoing treatment are necessary to minimize patient risk from potentially related clinical errors.

[Patron saints of anesthesia]

Patron saints act as facilitators between God and humans. Humans appeal to patron saints for support in devastating, often futile situations in life. Patron saints may intercede for trade and professional guilds, every so often they hold a protective hand over objects. Saint Barbara is venerated as the patron saint of surgeons. In anesthesia she also oversees barbiturates, protects anesthetized patients, anesthetists and anesthesia nursing personnel. Within the Anglo-American language area Saint René is venerated by anesthetists and anesthesia nursing personnel. During anesthesia or critical care treatment patient safety and welfare are entirely in the hands of anesthetists and intensivists. Especially in the borderland of critical illness and imminent death, it may be reassuring for religiously or spiritually orientated physicians and nurses that they can turn to "their" patron saints to intercede so that upcoming anesthetic procedures or intensive care interventions will meet with success. Hereby, the heavy burden of responsibility may be borne more easily and equanimously.

Ketamine dependence in an anesthesiologist: an occupational hazard?

Substance abuse among medical professionals is a cause for concern. Certain psychotropic substances such as ketamine are at easy dispense to anesthesiologists increasing the likelihood of misuse and dependence and raise several issues including safety of patients. We discuss a case demonstrating ketamine dependence in an anesthesiologist from India. The reported psychotropic effects of ketamine ranged from dissociation and depersonalization to psychotic experiences. There was also development of significant tolerance to ketamine without prominent physical withdrawal symptoms and cyclical use of very high doses was observed. Issues related to management of health professionals are also discussed.

Occupational hazards and diseases related to the practice of anesthesiology

BACKGROUND AND OBJECTIVES

The practice of anesthesiology is not without risks to the anesthesiologist. The operating room (OR), in which anesthesiologists spend most of their time, is regarded as an unhealthy workplace due to the potential risks it offers. In this review, we propose an analysis of the occupational hazards that anesthesiologists are exposed in their daily practice.

CONTENT

We present a classification of risk and its relationship to occupational diseases.

CONCLUSION

Control of occupational hazards to which anesthesiologists are exposed daily is necessary in order to develop an appropriate workplace and minimize risks to the good practice of anesthesiology. This contributes to decrease absenteeism, improve patients' care and quality of life of anesthesiologists.

[Life-threatening fentanyl and propofol addiction: interview with a survivor]

Anesthesiologists have a well-known increased risk of substance abuse including the intravenous administration of opioids and propofol. However, katamnestic reports from the point of view of propofol-addicted anesthesiologists themselves are missing which would aid a better understanding of the dynamics and progress of addiction. This article presents an interview with a formerly addicted female anesthesiologist who after long-term abuse with oral tilidine combined with naloxone switched to intravenous administration of fentanyl and later on propofol. Several life-threatening incidents occurred but after some severe setbacks occupational rehabilitation outside the field of anesthesiology was successful following inpatient treatment. This case shows exemplarily in accordance with the current literature that warning signs in addicted physicians are often ignored by colleagues and supervisors and rehabilitation is possible under professional therapy and continuous surveillance. Additionally, this case emphasizes the necessity of controlling the distribution of propofol to reduce the life-threatening professional risk to anesthesiologists.

Development of a simultaneous analytical method for selected anorectics, methamphetamine, MDMA, and their metabolites in hair using LC-MS/MS to prove anorectics abuse

Owing to the tight control of methamphetamine, it is presumed that phentermine, an amphetamine-type anorectic, has recently been considered a supplement for methamphetamine abusers in Korea. In addition, the abuse of other anorectics obtained by inappropriate means has become a social issue. Hair is a useful specimen to prove chronic drug use. Therefore, an analytical method for the simultaneous detection of phentermine, phendimetrazine, amfepramone, fenfluramine, mazindol, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA), as well as their metabolites, which covers the major amphetamines and anorectic agents in Korea, in hair was established and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The drugs and their metabolites in hair were extracted using 1 % HCl in methanol and then filtered and analyzed by LC-MS/MS with electrospray ionization in positive mode. The validation results for selectivity, linearity, matrix effect, recovery, process efficiency, intra- and interassay precision and accuracy, and processed sample stability were satisfactory. The limits of detection ranged from 0.025 to 1 ng/10 mg hair and the limits of quantification were 0.25 ng/10 mg hair for every analyte except mazindol and phentermine, for which they were 10 ng/10 mg hair. The method was successfully applied for the segmental determination of selected anorectics, methamphetamine, MDMA, and their metabolites in hair from 39 drug suspects. Among the anorectics, phentermine and/or phendimetrazine were identified with or without methamphetamine in the hair samples. Closer supervision of the inappropriate use of anorectics is necessary. Also, hair analysis is useful for monitoring the abuse potential of unnoticed drugs.

Hair: a complementary source of bioanalytical information in forensic toxicology

Hair has been used for years in the assessment and documentation of human exposure to drugs, as it presents characteristics that make it extremely valuable for this purpose, namely the fact that sample collection is performed in a noninvasive manner, under close supervision, the possibility of collecting a specimen reflecting a similar timeline in the case of claims or suspicion of a leak in the chain of custody, and the increased window of detection for the drugs. For these reasons, testing for drugs in hair provides unique and useful information in several fields of toxicology, from which the most prominent is the possibility of studying individual drug use histories by means of segmental analysis. This paper will review the unique role of hair as a complementary sample in documenting human exposure to drugs in the fields of clinical and forensic toxicology and workplace drug testing.

Bioanalytical procedures and recent developments in the determination of opiates/opioids in human biological samples

The use and abuse of illegal drugs affects all modern societies, and therefore the assessment of drug exposure is an important task that needs to be accomplished. For this reason, the reliable determination of these drugs and their metabolites in biological specimens is an issue of utmost relevance for both clinical and forensic toxicology laboratories in their fields of expertise, including in utero drug exposure, driving under the influence of drugs and drug use in workplace scenarios. Most of the confirmatory analyses for abused drugs in biological samples are performed by gas chromatographic-mass spectrometric methods, but use of the more recent and sensitive liquid chromatography-(tandem) mass spectrometry technology is increasing dramatically. This article reviews recently published articles that describe procedures for the detection of opiates in the most commonly used human biological matrices, blood and urine, and also in unconventional ones, e.g. oral fluid, hair, and meconium. Special attention will be paid to sample preparation and chromatographic analysis.

Physician views regarding substance use-related participation in a state physician health program

Physician Health Programs (PHPs) safeguard the public by monitoring impaired physicians, but participation is not always voluntary, and many physicians resist referral. In this study, 80 physicians (85.1% male) who were referred to a state PHP for substance use-related problems completed an anonymous online survey regarding their experiences in the program. Results indicated that 78.1% of program completers had a 5-year contract, with 100% including random drug screening. In addition, 84.8% continued participation in 12-step fellowships after the required monitoring period. Participants were generally satisfied with the program, and 92.5% indicated that they would recommend it to others. They provided suggestions to increase the acceptability and efficacy of PHPs for physicians. 

Analytical methods for abused drugs in hair and their applications

Hair has been focused on for its usability as an alternative biological specimen to blood and urine for determining drugs of abuse in fields such as forensic and toxicological sciences because hair can be used to elucidate the long intake history of abused drugs compared with blood and urine. Hair analysis consists of several pretreatment steps, such as washing out contaminates from hair, extraction of target compounds from hair, and cleanup for instrumental analysis. Each step includes characteristic and independent features for the class of drugs, e.g., stimulants, narcotics, cannabis, and other medicaments. In this review, recently developed methods to determine drugs of abuse are summarized, and the pretreatment steps as well as the sensitivity and applicability are critically discussed.

Intravenous fentanyl is exhaled and the concentration fluctuates with time

Previous studies have reported that fentanyl is eliminated predominantly by hepatic biotransformation, and that some is eliminated unchanged in urine and stools. No reports have described the elimination of fentanyl via the lungs. In this study, exhaled gas samples from eight anaesthetized patients undergoing cardiac surgery were analysed using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Results confirmed that fentanyl was exhaled by patients after intravenous administration, that the concentration of exhaled fentanyl fluctuated with time and peak concentrations were reached approximately 15 - 20 min after intravenous fentanyl administration. Thus, in addition to hepatic biotrans formation and elimination via urine and faeces, fentanyl is also eliminated unchanged by the lungs. The potential risk to operating theatre personnel from long-term exposure to low levels of exhaled anaesthetic agents following intravenous administration to patients during surgery warrants further research.