Kinetics of isoflurane and sevoflurane in a unidirectional displacement flow and the relevance to anesthetic gas exposure by operating room personnel.

International guidelines recommend the use of ventilation systems in operating rooms to reduce the concentration of potentially hazardous substances such as anesthetic gases. The exhaust air grilles of these systems are typically located in the lower corners of the operating room and pick up two-thirds of the air volume, whereas the final third is taken from near the ceiling, which guarantees an optimal perfusion of the operating room with a sterile filtered air supply. However, this setup is also employed because anesthetic gases have a higher molecular weight than the components of air and should pool on the floor if movement is kept to a minimum and if a ventilation system with a unidirectional displacement flow is employed. However, this anticipated pooling of volatile anesthetics at the floor level has never been proven. Thus, we herein investigated the flow behaviors of isoflurane, sevoflurane, and carbon dioxide (for comparison) in a measuring chamber sized 2.46 × 1.85 × 5.40 m with a velocity of 0.3 m/sec and a degree of turbulence <20%. Gas concentrations were measured at 1,728 measuring positions throughout the measuring chamber, and the flow behaviors of isoflurane and sevoflurane were found to be similar, with an overlap of 90%. The largest spread of both gases was 55 cm at 5.4 m from the emission source. Interestingly, neither isoflurane nor sevoflurane was detected at floor level, but a continuous cone-like spreading was observed due to gravity. In contrast, carbon dioxide accumulated at floor level in the form of a gas cloud. Thus, floor level exhaust ventilation systems are likely unsuitable for the collection and removal of anesthetic gases from operating rooms.

The impact of the anesthetic conserving device on occupational exposure to isoflurane among intensive care healthcare professionals.

BACKGROUND: Use of anesthetic conserving devices (ACD) for inhalational isoflurane sedation in Intensive Care Units (ICU) has grown in recent years, and healthcare professionals are concerned about isoflurane pollution and exposure-related health risks. Real-time measurements to determine isoflurane exposure in ICU personnel during short-term patient care procedures and ACD handling have not yet been performed. METHODS: Isoflurane concentrations in the breathing zones of ICU staff (25 cm around the nose and mouth) were measured, by photoacoustic gas monitoring, during daily practice including tracheal suctioning, oral hygiene, body care, and patient positioning. Isoflurane pollution was further determined during ACD replacement, syringe filling, and after isoflurane spillages. RESULTS: The average mean isoflurane concentration 25 cm above patients' tracheostoma was 0.3 ppm. Mean (cmean) and maximum (cmax) isoflurane exposure in personnel's breathing zones during patient care ranged from 0.4 to 1.9 ppm and 0.7 to 6.6 ppm, respectively. Isoflurane exposure during ACD replacement was cmean 0.5 to 17.4 ppm and cmax 0.8 to 114.3 ppm. Isoflurane concentrations during ACD syringe filling ranged from 2.4 to 9.1 ppm. The maximum isoflurane concentrations after spillage were dose-dependent. CONCLUSIONS: Use of ACDs and patient physical manipulation are accompanied by isoflurane pollution. Baseline concentrations did not exceed long-term exposure limits, but short-term limits were occasionally exceeded during patient care procedures and ACD handling. Spillages should be avoided, especially when air-conditioning and scavenging systems are unavailable.

The child's behavior during inhalational induction and its impact on the anesthesiologist's sevoflurane exposure.

BACKGROUND: Sevoflurane is commonly used for inhalational inductions in children, but the personnel's exposure to it is potentially harmful. Guidance to reduce gas pollution refers mainly to technical aspects, but the impact of the child's behavior has not yet been studied. AIMS: The purpose of this study was to determine how child behavior, according to the Frankl Behavioral Scale, affects the amount of waste sevoflurane in anesthesiologists' breathing zones. METHODS: Sixty-eight children aged 36-96 months undergoing elective ENT surgery were recruited for this prospective, observational investigation. After oral midazolam premedication (0.5 mg/kg body weight), patients obtained sevoflurane using a facemask with an inspiratory concentration of 8 Vol.% in 100% oxygen (flow 10 L/min). Ventilation was manually supported and a venous catheter was placed. The inspiratory sevoflurane concentration was reduced, and remifentanil and propofol were administered before the facemask was removed and a cuffed tracheal tube inserted. The child's behavior toward the operating room personnel during induction was evaluated by the anesthesiologist (Frankl Behavioral Scale: 1-2 = negative behavior, 3-4 = positive behavior). During induction mean (c¯mean) and maximum (c¯max), sevoflurane concentrations were determined in the anesthesiologist's breathing zone by continuous photoacoustic gas monitoring. RESULTS: Mean and maximum sevoflurane concentrations were c¯mean = 4.38 ± 4.02 p.p.m and c¯max = 70.06 ± 61.08 p.p.m in patients with positive behaviors and sufficient premedications and c¯mean = 12.63 ± 8.66 p.p.m and c¯max = 242.86 ± 139.91 p.p.m in children with negative behaviors and insufficient premedications (c¯mean: P < .001; c¯max: P < .001). CONCLUSION: Negative behavior was accompanied by significantly higher mean and maximum sevoflurane concentrations in the anesthesiologist's breathing zone compared with children with positive attitudes. Consequently, the status of premedication influences the amount of sevoflurane pollution in the air of operating rooms.

Occupational Chronic Sevoflurane Exposure in the Everyday Reality of the Anesthesia Workplace.

BACKGROUND: Although sevoflurane is one of the most commonly used volatile anesthetics in clinical practice, anesthesiologists are hardly aware of their individual occupational chronic sevoflurane exposure. Therefore, we studied sevoflurane concentrations in the anesthesiologists' breathing zones, depending on the kind of induction for general anesthesia, the used airway device, and the type of airflow system in the operating room. Furthermore, sevoflurane baselines and typical peaks during general anesthesia were determined. METHODS: Measurements were performed with the LumaSense Photoacoustic Gas Monitor. As we detected the gas monitor's cross-sensitivity reactions between sevoflurane and disinfectants, regression lines for customarily used disinfectants during surgery (Cutasept®, Octeniderm®) and their alcoholic components were initially analyzed. Hospital sevoflurane concentrations were thereafter measured during elective surgery in 119 patients. The amount of inhaled sevoflurane by anesthesiologists was estimated according to mVA = cVA × V × t × ρVA aer. RESULTS: Induction of general anesthesia stopped after tracheal intubation with the patient's expiratory sevoflurane concentration of 1.5%. Thereby, inhalational inductions (INH) caused higher sevoflurane concentrations than IV inductions (mean [SD]: (Equation is included in full-text article.)[ppm] INH 2.43 ± 1.91 versus IV 0.62 ± 0.33, P < 0.001; mVA [mg] INH 1.95 ± 1.54 versus IV 0.30 ± 0.22, P < 0.001). The use of laryngeal mask airway (LMA™) led to generally higher sevoflurane concentrations in the anesthesiologists' breathing zones than tracheal tubes ((Equation is included in full-text article.)[ppm] tube 0.37 ± 0.16 versus LMA™ 0.79 ± 0.53, P = 0.009; (Equation is included in full-text article.)[ppm] tube 1.91 ± 0.91 versus LMA™ 2.91 ± 1.81, P = 0.057; mVA [mg] tube 1.47 ± 0.64 versus LMA™ 2.73 ± 1.81, P = 0.019). Sevoflurane concentrations were trended higher during surgery in operating rooms with turbulent flow (TF) air-conditioning systems compared with laminar flow (LF) air-conditioning systems ((Equation is included in full-text article.)[ppm] TF 0.29 ± 0.12 versus LF 0.13 ± 0.06, P = 0.012; mVA [mg/h] TF 1.16 ± 0.50 versus LF 0.51 ± 0.25, P = 0.007). CONCLUSIONS: Anesthesiologists are chronically exposed to trace concentrations of sevoflurane during work. Inhalational inductions, LMA™, and TF air-conditioning systems in particular are associated with higher sevoflurane exposure. However, the amount of inhaled sevoflurane per day was lower than expected, perhaps because concentrations in previous measurements could be overestimated (10%-15%) because of the cross-sensitivity reaction.

Highly integrated system solutions for air conditioning.

Starting with the air handling unit, new features concerning energy efficient air treatment in combination with optimisation of required space were presented. Strategic concepts for the supply of one or more operating suites with a modular based air handling system were discussed. The operating theatre ceiling itself, as a major part of the whole integrated system, is no longer a simple air outlet: additional functions have been added in so-called media-bridges, so that it has changed towards a medical apparatus serving as a daily tool for the physicians and the operating staff. Last and not least, the servicing of the whole system has become an integral part of the facility management with remote access to the main functions and controls. The results are understood to be the basis for a discussion with specialists from medical and hygienic disciplines as well as with technically orientated people representing the hospital and building-engineering.