Comparison of waste anesthetic gases in operating rooms with or without an scavenging system in a Brazilian University Hospital / Comparação de resíduos de gases anestésicos em salas de operação com ou sem sistema de exaustão em hospital universitário brasileiro

Abstract Background and objectives Occupational exposure to waste anesthetic gases in operating room without active scavenging system has been associated with adverse health effects. Thus, this study aimed to compare the trace concentrations of the inhalational anesthetics isoflurane and sevoflurane in operating room with and without central scavenging system. Method Waste concentrations of isoflurane and sevoflurane were measured by infrared analyzer at different locations (near the respiratory area of the assistant nurse and anesthesiologist and near the anesthesia station) and at two times (30 and 120 min after the start of surgery) in both operating room types. Results All isoflurane and sevoflurane concentrations in unscavenged operating room were higher than the US recommended limit (2 parts per million), regardless of the location and time evaluated. In scavenged operating room, the average concentrations of isoflurane were within the limit of exposure, except for the measurements near the anesthesia station, regardless of the measurement times. For sevoflurane, concentrations exceeded the limit value at all measurement locations and at both times. Conclusions The exposure to both anesthetics exceeded the international limit in unscavenged operating room. In scavenged operating room, the concentrations of sevoflurane, and to a lesser extent those of isoflurane, exceeded the recommended limit value. Thus, the operating room scavenging system analyzed in the present study decreased the anesthetic concentrations, although not to the internationally recommended values.

Resumo Justificativa e objetivos A exposição ocupacional aos resíduos de gases anestésicos em salas de operação (SO) sem sistema ativo de exaustão tem sido associada a efeitos adversos à saúde. Assim, o objetivo do estudo foi comparar os resíduos dos anestésicos inalatórios isoflurano e sevoflurano em SO com e sem sistema de exaustão. Método Concentrações residuais de isoflurano e sevoflurano foram mensuradas por analisador infravermelho em diferentes locais (próximo à área respiratória do auxiliar de enfermagem e do anestesiologista e próximo à estação de anestesia) e em dois momentos (30 e 120 min após o início da cirurgia) em ambos os tipos de SO. Resultados Todas as concentrações de isoflurano e sevoflurano nas SO sem sistema de exaustão foram mais elevadas em relação ao valor limite recomendado pelos EUA (2 partes por milhão), independentemente do local e momento avaliados. Nas SO com sistema de exaustão, as concentrações médias de isoflurano ficaram dentro do limite de exposição, exceto para as mensurações próximas à estação de anestesia, independentemente dos momentos avaliados. Para o sevoflurano, as concentrações excederam o valor limite em todos locais de medição e nos dois momentos. Conclusões A exposição a ambos os anestésicos excedeu o limite internacional nas SO sem sistema de exaustão. Nas SO com sistema de exaustão, as concentrações de sevoflurano, e em menor extensão, as de isoflurano excederam o valor limite recomendado. Dessa forma, o sistema de exaustão das SO analisado no presente estudo diminuiu as concentrações dos anestésicos, embora não tenha reduzido a valores internacionalmente recomendados.

Monitoring of volatile anesthetics in operating room personnel using GC-MS

To estimate individual occupational exposure of operating room personnel to nitrous oxide, sevoflurane, isoflurane and halothane during regular working hours. Volatile anesthetics in urine and breathing area air samples were measured in forty subjects. Passive samplers were collected after continuous five-to-seven hours of exposure. Further, thirty air samples, using passive samplers, were collected from 14 operating rooms of the Jordan University Hospital. All air and urine samples were analyzed using static headspace sampler coupled to capillary column GC-MS system. The monitored anesthetic volatile agents values of breathing area air samples were as the following [mean +/- SEM, ppm]: 43.2 +/- 6.29, 4.16 +/- 2.38, 0.19 +/- 0.05 And 0.15 +/- 0.10 for nitrous oxide, sevoflurane, isoflurane and halothane, respectively. Whereas, values of the post- shift urine samples [mean +/- SEM, micro g/1] were: 1234 +/- 209, 4.3 +/- 0.82, 3.75 +/- 0.7 and 9.9 +/- 1.2 for nitrous oxide, sevoflurane, isoflurane and halothane, respectively. Concerning operating rooms contaminations, the median and the [range] values for N[2] O were 90.4 ppm [12.2 - 327], for sevoflurane they were 16.4 ppm [2.14-53.7], for isoflurane 10.7 ppm [0.41-24.9] and for halothane 0.71 ppm [0.00 8-6.05]. Based on the results of this study, it is obvious that operating rooms personnel were exposed to high level of anesthetic agents and therefore, it is recommended to install efficient scavenging systems inside the operating rooms beside the regular maintenance of anesthetic machines. Moreover, the awareness of operating room personnel should be increased in order to minimize possible health risk. MS= Mass Spectrometry; GC= Gas liquid Chromatography; NIOSH= United States Institute for Occupational Safety and Health; JUH: Jordan University Hospital; MeOH= Methanol; ug= microgram; v/v= Volume to volume; SIM; Single Ion Monitoring; ppm- one part per million parts; TWA= Time Weighted Average: r[2]. Correlation coefficient: SEM= Standard Error of the Mean

effect of different doses of oral tizanidine, on the minimum alveolar concentration of isoflurane and stress response

Alpha2-ADRENERGIC receptor agonists bind to peripheral and central nervous system sites modulating autonomio nervous system function. These effects may explain the clinically observed attenuation of sympathetically mediated responses to perioperative stress. They also have an antinociceptive effect in animals in humans premedicated with oral tizanidine an alpha2-adrenoceptor agonist, attenuated the increase in blood pressure associated with laryngoscopy and intubation and the amount of midazolam required for loss of consciousness was significantly reduced. We speculated that the oral administration of tizanidine might reduce the minimum alveolar anesthetic concentration [MAC] of isoflurane. Eighty ASA physical status patients, aged 24-56 yr, were randomly allocated into 4 groups [20 for each]: a Control group and a 2mg Tizanidine group, 4mg Tizanidine group, 10mg Tizanidine group. As premedication, the Control group received a placebo, and the Tizanidine groups received oral tizanidine 70 min. before surgical skin incision. Anesthesia was induced in all patients by propofol 2-2.5 mg/kg intravenously mixed with tidocaine 0.3 mg/kg, given over 30s. until loss of eyelid reflex [determined every 15 s]. After loss of consciousness, appropriate size of laryngeal mask was introduced by Brain method. Then administration of isoflurane was begun; the patients were spontaneously ventilated using a non-rebreathing system. MAC was determined by a technique adapted from the conventional up-down method for quanta! responses. The MAC of isoflurane was 1.3 +/- 0.13in the Control group, 1.24 +/- 0.1 in group It. 0.9 +/- 0.2 in grouplll and 0 7 +/- 0.2 in group IV. In group III and IV the plasma concentrations of epinephrine and norepinephrine were statistically significantly decreased during surgery and remained decreased thereafter. The oral administration of tizanidine successfully reduced the MA C of isoflurane, decreased the release of stress hormones and decreased the postoperative analgesic requirements in human adults

Efeitos cardiovasculares e respiratórios em cães anestesiados com diferentes concentrações de isoflurano / Cardiovascular and pulmonary effects of different isoflurane concentrations in dogs

No presente trabalho foram analisados os efeitos sobre os aparelhos cardiovascular e respiratório da anestesia inalatória com isoflurano em 3 (três) concentrações fixas (1, 1 ,5 e 2 CAM) no cão. Foram utilizados 6 (seis) cães machos, pesando 25 ± 2, 7 kg, com valores hematológicos e bioquímicas dentro da faixa de normalidade. Os parâmetros analisados foram: frequência cardíaca (FC), pressão arterial sistólica (PS), diastólica (PD) e média (PM), débito cardíaco (DC), índice cardíaco (IC), frequência respiratória (FR),volume corrente (VC) e volume minuto (VM). Observou-se que, baixas concentrações de isoflurano (1 e 1,5 CAM) produziram um aumento de FC. Com relação à pressão arterial, verificou-se um decréscimo dose-dependente, causado pela diminuição da resistência vascular periférica, o que explicaria a manutenção do DC e IC em baixas concentrações (1 e 1,5 CAM). A 2 CAM de concentração, o aumento da FC não foi capaz de compensar o menor volume de ejeção do coração. Devido a isso, observou-se queda do DC e IC. No sistema respiratório, encontrou-se diminuição da FR, VC e VM, dose-dependente.

Cardiovascular and pulmonary effexts of isoflurane anesthesia at 1, 1 ,5 and 2 minimum alveolar concentration (MAC) were studies in 6 male dogs, healty, weighting 25 ± 2.7 kg. Heart rate (HR), systolic arterial pressure (SAP), dyastolic arterial pressure rate (RR), tidal volume (TV) and minute ventilation (MV) were measured. Low isoflurane concentrations (1 and 1,5 MAC) increased the heart rate (HR). Arterial blood pressure decreased as the MAC increased, explaining the maintenance of the CO and the Cl at low concentrations of isoflurane (1 and 1,5 MAC). At 2 MAC the increase of the HR is not enough to compensate the low heart stroke volume, soa drop of CO an Cl was obseved. A dose-dependent decrease of the RR, TV and MV was also obseved.