Urine Biochemistry of a Human Fetus with Urinary Tract Obstruction - A Case Report.

INTRODUCTION: Fetal lower urinary tract obstruction (LUTO) can be mild or severe with oligohydramnios, renal dysplasia and pulmonary hypoplasia. Fetal urine biochemical markers correlate with fetal prognosis and, if favorable, surgical intervention is feasible. METHODS: We report a patient in her 18th gestational week whose fetus was diagnosed with LUTO and underwent fetal urine sampling for calcium, sodium, chloride, beta2-microglobulin and total protein of the routine LUTO panel, with the addition of creatinine, glucose, phosphate, urea, ammonia, albumin, and NGAL. RESULTS: Although the routine fetal urine biochemistry seemed to be favorably trending favorably, sodium, beta2-microglobulin, glucose, and urea did not decrease to the reference ranges, and ammonia and creatinine were lower than the reference ranges. Ultrasound demonstrated no improvement of the obstruction. CONCLUSIONS: This case highlights the need to acquire further experience with biochemical fetal urine markers in order to better manage LUTO.

Monitoring surface contamination for thirty antineoplastic drugs: a new proposal for surface exposure levels (SELs).

BACKGROUND: Chemotherapy drugs are widely used to treat cancer, but their active compounds represent a danger for workers who could be exposed to them. However, they aren't yet included in directive CE No. 1272/2008 and the European Biosafety Network has only recommended a limit value of 100 pg/cm2 for surface contamination. Thus, it is crucial to assess surface contaminations in healthcare environments. Currently, the technique of choice is surface wipe test combined with liquid chromatography tandem mass spectrometry to achieve high sensibility. MATERIAL AND METHODS: A campaign involving Careggi University Hospital (Florence, Italy) was performed from January 2020 to December 2021, collecting 1449 wipe samples between administration units, preparation unit, and personnel gloves. From the obtained data, the 90th percentile was calculated for 30 antiblastic drugs and proposed as surface exposure levels (SELs); while from data concerning personnel glove contamination, weekly contamination was estimated. RESULTS: In the 2-year period only 417 wipe samples were found positive (28.8%), the majority of which regard samples coming from administration unit bathrooms. The proposed SELs are almost all <100 pg/cm2, except for few drugs which produce higher contamination on bathroom surfaces. Also, the estimation of pharmacy personnel's glove contamination highlighted very low results (ng/week). CONCLUSIONS: Deeply established protocols and procedures for safe handling of ADs allow for obtaining excellent cleaning results and thus a safer work environment, however, the risk of cytostatic contaminations cannot be avoided in healthcare workplaces, and thus a harmonization of classification and labeling of chemotherapy drugs throughout the European Union should be done. Med Pr. 2022;73(5):383-96.

Life-threatening pediatric poisoning due to ingestion of Bufo bufo toad eggs: A case report.

Bufo parotid glands and eggs contain cardiac glycosides also known as bufadienolides. This class of molecules can cause digoxin-like cardiac toxicity, as they can block the sodium potassium-adenosine triphosphatase (Na/K-ATPase) pump. Poisoning with these toxins is rare but carries a high mortality risk. There are only a few cases of toad poisoning that have been reported worldwide, mainly in the southern hemisphere. We will describe the case of a child on the autistic spectrum disorder who developed an acute and severe cardiac bradyarrhythmia soon after being in a mountain creek. The child ingested a large quantity of Bufo bufo toad eggs and developed bradycardia (35/min) associated with junctional rhythm with narrow QRS complexes. The poison control center (PCC) indicated the use of atropine on the way to the nearest hospital and the administration of antidotal therapy, i.e., anti-digoxine fragment antibodies (DigiFab), as soon as possible. The patient was transferred by air ambulance to the Regional Referral Pediatric Hospital (RRPH), tested for digoxin blood level by immuno-essay (0.68 ng/mL) and successfully treated with five vials of DigiFab, since atropine administration produced only a fleeting effect on the cardiac rhythm. Patient was discharged 48 hours after poisoning. The presence of bufadienolides in the toad eggs was also confirmed. To our knowledge, this is the first report of toad egg poisoning in Europe. The administration of Digifab helped to reverse the bufadienolide cardiac toxicity.

Advanced Solid-Phase Microextraction Techniques and Related Automation: A Review of Commercially Available Technologies.

The solid-phase microextraction (SPME), invented by Pawliszyn in 1989, today has a renewed and growing use and interest in the scientific community with fourteen techniques currently available on the market. The miniaturization of traditional sample preparation devices fulfills the new request of an environmental friendly analytical chemistry. The recent upswing of these solid-phase microextraction technologies has brought new availability and range of robotic automation. The microextraction solutions propose today on the market can cover a wide variety of analytical fields and applications. This review reports on the state-of-the-art innovative solid-phase microextraction techniques, especially those used for chromatographic separation and mass-spectrometric detection, given the recent improvements in availability and range of automation techniques. The progressively implemented solid-phase microextraction techniques and related automated commercially available devices are classified and described to offer a valuable tool to summarize their potential combinations to face all the laboratories requirements in terms of analytical applications, robustness, sensitivity, and throughput.

Improvement in estimation of time since death by albumin and potassium concentrations in vitreous humor.

The measurement of the potassium concentration (K+) in vitreous humor (VH) has been a well-known adjunct for the estimation of the post-mortem interval (PMI) since the early 1960s. For years, however, many authors have been using other biochemical markers in an attempt to improve predictions. In this paper we confirm the role of K+ in the determination of the PMI adopting a linear regression model and we investigate whether other biochemical markers could improve the model through a multiple regression analysis. Additionally, the research aims to confirm the data of the analytes of interest among different techniques and instrumentations. We deemed this as an important issue because a primary concern in the literature is that automated analytical methods are often calibrated and, for the most part, validated for serum or urine analysis. Our results confirmed the well-established role of K+ as well as highlighted Albumin as a novel marker to be considered for further improvement of prediction models, especially since 72 h after death.

Occupational exposure to antineoplastic drugs in hospital environments: potential risk associated with contact with cyclophosphamide- and ifosfamide-contaminated surfaces.

BACKGROUND: Cyclophosphamide (CP) and ifosfamide (IP) contaminations have been detected in hospital environments. This study was conducted to determine if there was any contamination in the spaces (floors and door handles) between the hospital exit and the antineoplastic drugs (ADs) preparation and administration units. At the same time, the authors proposed a new automation of the analytical procedure to considerably decrease the time needed for sample preparation and analysis. MATERIAL AND METHODS: To evaluate the ADs contamination of surfaces, 829 wipe tests were performed in a campaign involving 3 hospitals located in Italy. Sampling was performed using an innovative kit. The levels of ADs were measured in each wipe sample using liquid chromatography/triple quadrupole. RESULTS: On-line solid-phase extraction guarantees the construction of a robust and reproducible analytical method. The CP and IP recoveries from stainless steel, polycarbonate and polyvinyl chloride ranged >80%, and the wipe holders and the automation tested ensured desorption efficiencies close to 100% for both the ADs. Of the 552 wipes taken on the spaces between the hospital exit and the preparation, administration and pharmacy warehouse units, 22 were greater than or equal to the limit of quantification, all adjacent to the administration units. CONCLUSIONS: This study provides an insight into the exposure situation against ADs residues. In order to improve environmental monitoring programs, the authors propose to evaluate the ADs contamination also outside the preparation, administration and pharmacy warehouse units. Med Pr. 2020;71(5):519-29.

Identification of Amoxicillin Crystals in Urine: a Case Report.

BACKGROUND: The case concerns a 30-year-old woman in the 24th week of pregnancy presenting to the medical emergency room with fever and abdominal pain. Urine sediment microscopy revealed the presence of unknown needle-shaped crystals. METHODS: Crystals identification was performed by Fourier-Transform Infrared Spectroscopy coupled to Attenuated Total Reflectance (FTIR-ATR). RESULTS: Amoxicillin crystals were verified with semiquantitative results of 87.7%. CONCLUSIONS: Drug-induced crystalluria is a frequent finding in urine examination and it may be asymptomatic. FTIR spectroscopy is a rapid and specific tool in identification of crystals and could be useful supporting renal disease diagnosis and monitoring drug therapy.

Health risk assessment related to hydrogen peroxide presence in the workplace atmosphere - analytical methods evaluation for an innovative monitoring protocol.

OBJECTIVES: Hydrogen peroxide (HP) accounts for 15% of the total global chemical revenue. According to the National Institute of Occupational Safety and Health, the HP concentration immediately dangerous to human life or health is 75 ppm. Operators exposed to HP should pay attention when choosing the monitoring technique that should be specific and sensitive enough to discriminate the exposure levels from background concentrations. In order to assess the long- and short-term exposure to HP in disinfection processes, the authors compared 6 industrial hygiene monitoring methods to evaluate their efficiency in measuring airborne HP concentrations. MATERIAL AND METHODS: Airborne HP concentrations were evaluated using an on-fiber triphenylphosphine solid-phase microextraction method, and they were compared with those obtained using a 13-mm Swinnex titanium oxysulfate filter holder and 4 portable direct-reading electrochemical sensors. A survey carried out in wood pulp bleaching, food and beverage disinfection processing, and in a hospital department to reduce the risk of spreading nosocomial infections, was performed during routine operations to access the risk of HP occupational exposure. RESULTS: Through the generation of HP gaseous dynamic atmospheres (0.1-85 ppm), the authors evaluated the consistency of the results obtained using the 6 methods described. The monitoring campaigns showed that the increase in HP could be relatively high (until 67 ppm) in food and beverage processing. CONCLUSIONS: In the authors' opinion, the current 8-h time-weighted average limits of 1 ppm for HP do not reflect the actual risk; a short-term exposure limit would, therefore, provide a much better protection. 2020;33(2):137-50.

New fully automated gas chromatographic analysis of urinary S-phenylmercapturic acid in isotopic dilution using negative chemical ionization with isobutane as reagent gas.

The determination of urinary S-phenylmercapturic acid (S-PMA) represents the most reliable biomarker to monitor the intake risk of airborne benzene. Recently, the European Chemical Agency deliberated new occupational exposure limits for benzene and recommended an S-PMA biological limit value of 2-µg/g creatinine. This limit is an order of magnitude lower than the previous one, and its determination constitutes a challenge in the analytical field. We developed and validated a method that allows the fully automated and sensitive determination of S-PMA by the use of gas-chromatography negative chemical ionization tandem mass spectrometry in isotopic dilution. For negative chemical ionization, we selected a mixture of 1% isobutane in argon as reactive gas, by studying its chemical ionization mechanism and optimal parameters compared with pure isobutane or pure methane. This gas mixture produces a more abundant signal of the target analyte than isobutane or methane, and it extended the operative lifetime of the ion source, enabling us to start a high-throughput approach of the S-PMA analysis. Moreover, energy-resolved mass spectrometry experiments were carried out to refine the MS/MS analysis conditions, testing nitrogen and argon as collision gases. The method optimization was pursued by a chemometric model by using the experimental design. The quantification limit for S-PMA was 0.10 µg/L. Accuracy (between 98.3% and 99.6%) and precision (ranging from 1.6% to 6.4%) were also evaluated. In conclusion, the newly developed assay represents a powerful tool for the robust, reliable, and sensitive quantification of urinary S-PMA, and because of its automation, it is well suited for application in large environmental and biological monitoring.

Monitoring of Air-Dispersed Formaldehyde and Carbonyl Compounds as Vapors and Adsorbed on Particulate Matter by Denuder-Filter Sampling and Gas Chromatographic Analysis.

Carbonyl compounds (CCs) are products present both as vapors and as condensed species adsorbed on the carbonaceous particle matter dispersed in the air of urban areas, due to vehicular traffic and human activities. Chronic exposure to CCs is a potential health risk given the toxicity of these chemicals. The present study reports on the measurement of the concentrations of 14 CCs in air as vapors and 2.5 µm fraction PM by the ENVINT GAS08/16 gas/aerosol sampler, a serial sampler that uses annular denuder, as sampling device. The 14 CCs were derivatized during sampling prior to gas-chromatographic separation and multiple detection by mass spectrometry, nitrogen-phosphorus thermionic, electron capture detection. Outdoor air multiple samples were collected in four locations in the urban area of Florence. The results evidenced that formaldehyde, acetaldehyde, and acetone were the more abundant CCs in the studied areas. The data collected was discussed considering the particle to vapor ratio of each CC found. The CCs pollution picture obtained was tentatively related to the nature and intensity of the traffic transiting by the sampling sites. This approach allowed to determine 14 CCs in both concentrated and diluted samples and is proposed as a tool for investigating outdoor and indoor pollution.

[Determination of airborne formaldehyde and ten other carbonyl pollutants using programmed temperature vaporization-large volume injection-gas chromatography].

Long-term indoor-air limit for formaldehyde stipulated by the European Commission is 1 µg/m3, while the World Health Organization has set a threshold of 100 µg/m3 that should not be exceeded for more than 30 min. To date, however, only a few analytical techniques have been developed that can be used to detect formaldehyde at these very restrictive limits. Thus, there is a need to develop for comprehensive methods for analyzing airborne formaldehyde and other carbonyl pollutants in the ambient environment. The aim of this study is to develop a highly sensitive online automated preconcentration gas chromatographic method using large-volume injection with a programmed temperature vaporization injector for the analysis of airborne formaldehyde and ten other carbonyl compounds. The influence of several parameters, such as the maximum volume injected, programmed temperature vaporization transfer time and temperature, carrier gas flow rate, and type of packing material was investigated. After optimization, highly satisfactory results in terms of the absolute and methodological detection limits were achieved, i. e. as low as the µg/m3 level for all the carbonyl pollutants studied. A commercially available sampler, originally designed for active sampling, was evaluated as a passive sampling device; this optimized technique was applied to monitor the concentrations of carbonyl pollutants in the indoor air of ten public buildings in Florence. The strength of this methodology lies both in the low detection limits reached in the simultaneous analysis of a wide group of 2,4-dinitrophenylhydrazine derivatives, and the potential adaptability of this method to other gas chromatographic applications to achieve lower sensitivity.

An Integrated Air Monitoring Approach for Assessment of Formaldehyde in the Workplace.

The aim of this study is to validate an integrated air monitoring approach for assessing airborne formaldehyde (FA) in the workplace. An active sampling by silica gel impregnated with 2,4-dinitrophenylhydrazine, a passive solid phase microextraction technique using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine as on-fiber derivatization reagent, an electrochemical direct-reading monitor, and an enzyme-based badge were evaluated and tested over a range of 0.020-5.12 ppm, using dynamically generated FA air concentrations. Simple linear regression analysis showed the four methods were suitable for evaluating airborne FA. Personal and area samplings in 12 anatomy pathology departments showed that the international occupational exposure limits in the GESTIS database were frequently exceeded. This monitoring approach would allow a fast, easy-to-use, and economical evaluation of both current work practices and eventual changes made to reduce FA vapor concentrations.

Analytical strategies for assessing occupational exposure to antineoplastic drugs in healthcare workplaces.

BACKGROUND: Cytotoxic antineoplastic drugs (ADs), widely used in treating cancer, are considered hazardous in the workplace and thus require safe handling practices. An analytical protocol for environmental and biological AD monitoring in the healthcare environment has been developed, since Europe lacks clear guidelines and regulations for cytostatic preparation and handling. MATERIAL AND METHODS: Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for measuring contemporaneously 20 multi-class cytostatic compounds and urinary α-fluoro-ß-alanine, whereas platinum was detected by inductively coupled plasma mass spectrometry (ICP-MS). Sampling procedures and analytical conditions were optimized and the assays were validated. Environmental AD monitoring data, collected in 2009-2017, for a total of 3749 wipe tests and 57 720 determinations, was evaluated. RESULTS: The proportion of positive samples gradually decreased from 11.7% in 2010 to 1% in 2017, however, 2266 determinations were positive. No urine sample had detectable concentrations of any of the 4 drugs considered (0/398 samples). CONCLUSIONS: These improvements are so large that the key role played by the new, more stringent rules for preparing and administering ADs is evident. Hence, the analytical method involving multi-element determinations allows for a more thorough and complete investigation into the AD contamination of work environments. Med Pr 2018;69(6):589-604.

A new approach to assessing occupational exposure to antineoplastic drugs in hospital environments.

Cytotoxic antineoplastic drugs (ADs) pose occupational risk and therefore require safe handling practices. We created, optimised, and validated an innovative monitoring protocol for simultaneously assessing 21 ADs in the healthcare environment, and also proposed surface exposure levels (SELs) to facilitate the interpretation of monitoring results, as there are currently no occupational exposure limits for ADs. The environmental AD monitoring data were collected in nine Italian hospitals between 2008 and 2017 and include 74,565 measurements in 4,814 wipe samples. Excellent overall recovery and sensitivity of the analytical methods along with innovative desorption automation make this protocol useful for routine monitoring. AD contamination was found in 3,081 measurements, confirming potential exposure in healthcare workers. Samples taken at the beginning and the end of work shifts, allowed to calculate 75th and 90th percentile values for each ADs both in preparation and administration units and we created a traffic-light colour-coding system to facilitate interpretation of the findings. The introduction of SELs will provide a solid basis for improving occupational safety and focusing on contamination control.

High-Throughput Analysis of Selected Urinary Hydroxy Polycyclic Aromatic Hydrocarbons by an Innovative Automated Solid-Phase Microextraction.

High-throughput screening of samples is the strategy of choice to detect occupational exposure biomarkers, yet it requires a user-friendly apparatus that gives relatively prompt results while ensuring high degrees of selectivity, precision, accuracy and automation, particularly in the preparation process. Miniaturization has attracted much attention in analytical chemistry and has driven solvent and sample savings as easier automation, the latter thanks to the introduction on the market of the three axis autosampler. In light of the above, this contribution describes a novel user-friendly solid-phase microextraction (SPME) off- and on-line platform coupled with gas chromatography and triple quadrupole-mass spectrometry to determine urinary metabolites of polycyclic aromatic hydrocarbons 1- and 2-hydroxy-naphthalene, 9-hydroxy-phenanthrene, 1-hydroxy-pyrene, 3- and 9-hydroxy-benzoantracene, and 3-hydroxy-benzo[a]pyrene. In this new procedure, chromatography's sensitivity is combined with the user-friendliness of N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide on-fiber SPME derivatization using direct immersion sampling; moreover, specific isotope-labelled internal standards provide quantitative accuracy. The detection limits for the seven OH-PAHs ranged from 0.25 to 4.52 ng/L. Intra-(from 2.5 to 3.0%) and inter-session (from 2.4 to 3.9%) repeatability was also evaluated. This method serves to identify suitable risk-control strategies for occupational hygiene conservation programs.

Assessment of occupational exposure to gaseous peracetic acid.

OBJECTIVES: In order to assess short-term exposure to peracetic acid (PAA) in disinfection processes, the Authors compared 4 industrial hygiene monitoring methods to evaluate their proficiency in measuring airborne PAA concentrations. MATERIAL AND METHODS: An active sampling by basic silica gel impregnated with methyl p-tolyl sulfoxide (MTSO), a passive solid phase micro-extraction technique using methyl p-tolyl sulfide (MTS) as on-fiber derivatization reagent, an electrochemical direct-reading PAA monitor, and a novel visual test strip PAA detector doped with 2,2'-azino-bis (3-ethylbenzothiazoline)-6-sulfonate were evaluated and tested over the range of 0.06-16 mg/m3, using dynamically generated PAA air concentrations. RESULTS: The linear regression analysis of linearity and accuracy showed that the 4 methods were suitable for PAA monitoring. Peracetic acid monitoring in several use applications showed that the PAA concentration (1.8 mg/m3) was immediately dangerous to life or health as proposed by the National Institute of Occupational Safety and Health, and was frequently exceeded in wastewater treatment (up to 7.33 mg/m3), and sometimes during food and beverage processes and hospital high-level disinfection operations (up to 6.8 mg/m3). CONCLUSIONS: The methods were suitable for the quick assessment of acute exposure in PAA environmental monitoring and can assist in improving safety and air quality in the workplace where this disinfectant is used. These monitoring methods allowed the evaluation of changes to work out practices to reduce PAA vapor concentrations during the operations when workers are potentially overexposed to this strong antioxidant agent. Int J Occup Med Environ Health 2018;31(4):527-535.

The New MIRUS System for Short-Term Sedation in Postsurgical ICU Patients.

OBJECTIVES: To evaluate the feasibility and safety of the MIRUS system (Pall International, Sarl, Fribourg, Switzerland) for sedation with sevoflurane for postsurgical ICU patients and to evaluate atmospheric pollution during sedation. DESIGN: Prospective interventional study. SETTING: Surgical ICU. February 2016 to December 2016. PATIENTS: Postsurgical patients requiring ICU admission, mechanical ventilation, and sedation. INTERVENTIONS: Sevoflurane was administered with the MIRUS system targeted to a Richmond Agitation Sedation Scale from -3 to -5 by adaptation of minimum alveolar concentration. MEASUREMENTS AND MAIN RESULTS: Data collected included Richmond Agitation Sedation Scale, minimum alveolar concentration, inspired and expired sevoflurane fraction, wake-up times, duration of sedation, sevoflurane consumption, respiratory and hemodynamic data, Simplified Acute Physiology Score II, Sepsis-related Organ Failure Assessment, and laboratory data and biomarkers of organ injury. Atmospheric pollution was monitored at different sites: before sevoflurane delivery (baseline) and during sedation with the probe 15 cm up to the MIRUS system (S1) and 15 cm from the filter-Reflector group (S2). Sixty-two patients were enrolled in the study. No technical failure occurred. Median Richmond Agitation Sedation Scale was -4.5 (interquartile range, -5 to -3.6) with sevoflurane delivered at a median minimum alveolar concentration of 0.45% (interquartile range, 0.4-0.53) yielding a mean inspiratory and expiratory concentrations of 0.79% (SD, 0.24) and 0.76% (SD, 0.18), respectively. Median awakening time was 4 minutes (2.2-5 min). Median duration of sevoflurane administration was 3.33 hours (2.33-5.75 hr), range 1-19 hours with a mean consumption of 7.89 mL/hr (SD, 2.99). Hemodynamics remained stable over the study period, and no laboratory data indicated liver or kidney injury or dysfunction. Median sevoflurane room air concentration was 0.10 parts per million (interquartile range, 0.07-0.15), 0.17 parts per million (interquartile range, 0.14-0.27), and 0.15 parts per million (interquartile range, 0.07-0.19) at baseline, S1, and S2, respectively. CONCLUSIONS: The MIRUS system is a promising and safe alternative for short-term sedation with sevoflurane of ICU patients. Atmospheric pollution is largely below the recommended thresholds (< 5 parts per million). Studies extended to more heterogeneous population of patients undergoing longer duration of sedation are needed to confirm these observations.

Innovative Monitoring of Atmospheric Gaseous Hydrogen Fluoride.

Hydrogen fluoride (HF) is a basic raw material for a wide variety of industrial products, with a worldwide production capacity of more than three million metric tonnes. A novel method for determining particulate fluoride and gaseous hydrogen fluoride in air is presented herewith. Air was sampled using miniaturised 13 mm Swinnex two-stage filter holders in a medium-flow pumping system and through the absorption of particulate fluoride and HF vapours on cellulose ester filters uncoated or impregnated with sodium carbonate. Furthermore, filter desorption from the holders and the extraction of the pentafluorobenzyl ester derivative based on solid-phase microextraction were performed using an innovative robotic system installed on an xyz autosampler on-line with gas chromatography (GC)/mass spectrometry (MS). After generating atmospheres of a known concentration of gaseous HF, we evaluated the agreement between the results of our sampling method and those of the conventional preassembled 37 mm cassette (±8.10%; correlation coefficient: 0.90). In addition, precision (relative standard deviation for n = 10, 4.3%), sensitivity (0.2 µg/filter), and linearity (2.0-4000 µg/filter; correlation coefficient: 0.9913) were also evaluated. This procedure combines the efficiency of GC/MS systems with the high throughput (96 samples/day) and the quantitative accuracy of pentafluorobenzyl bromide on-sample derivatisation.

Occupational exposure to nitrous oxide during procedural pain control in children: a comparison of different inhalation techniques and scavenging systems.

BACKGROUND: Nitrous oxide (N2 O 50% in oxygen) is commonly used for painful procedures in children. Potential negative health effects associated with chronic workplace exposure limit its use. Safe occupational N2 O exposure concentrations are below 25 ppm environmental concentration as a time-weighted average (TWA) and below 200 ppm as a short-time exposure level (STEL) of 15 min. AIM: The aim was to assess occupational exposure of staff during nitrous oxide administration to children using different inhalation delivery devices and scavenging systems. METHODS: Staff nitrous oxide exposure during use of a double face mask (DFM) with or without a demand valve (DV) was compared with a conventional single face mask (FM). We also compared exposure using the hospital central scavenging system with a portable evacuation system. N2 O concentrations, representing exposure values, were monitored within proximity to staff. Urine N2 O concentration was measured in staff administering the N2 O at the end of the procedural session. RESULTS: The mean and median values of TWA and STEL within the working area were lower than recommended values in the DFM (10.8, 11.6 ppm for TWA; 13.9, 11.0 ppm for STEL) and DFM-DV groups (2.3, 2.8 ppm for TWA; 4.4, 3.5 ppm for STEL) using the portable evacuation system. The N2 O urine exposure in DFM-DV group was lower than DFM group: a mean difference of 9.56 ppm (95% CI 2.65-16.46). Staff N2 O urinary concentrations were within safe biological limits in both the DFM and DFM-DV groups. High exposure concentrations to N2 O were recorded in all FM and FM-DV environmental and biological samples. CONCLUSIONS: The DFM system, with or without a DV, connected to a portable evacuation system during N2 O administration to children for painful procedures kept N2 O levels within the local environment below recommended limits.