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May 1997
Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia:
waste gas exposure during paediatric anaesthesia.
Hoerauf K, Funk W, Harth M, Hobbhahn J; Anaesthesia 52: 215-219, 1997.
[ see abstract below ]
In the course of taking care of our patients, we must remember also to care for ourselves. One potential source of injury to anesthesiologists and other operating room personnel is exposure to anesthetic gases. While no clear dose-effect relationships between chronic exposure to anesthetic gases and damage to neurological, psychomotor, reproductive or bone marrow function have been demonstrated, it seems prudent to know the extent of this exposure in order to minimize it.
Hoerauf and colleagues at the University Hospital in Vienna used a direct-reading multigas monitor, corrected for interference in the infrared region, to measure levels of nitrous oxide and halogenated agents
continuously from the breathing zones of the anesthesiologist and circulating nurse. The goal of their study was to quantify the concentrations during mask induction of anesthesia in pediatric patients and to determine their contribution to total exposure during procedures on these patients.
They found that during induction, the anesthesiologist was exposed on average to 100 ppm N2O on average, four times the upper limit of 25 ppm recommended by NIOSH. They also breathed 3-5 ppm halogenated agent, roughly twice the NIOSH recommendation of 2 ppm for halogenated agents used alone.
During induction, a circulating nurse standing on the other side of the room would be exposed to about half that amount. After tracheal intubation, contamination decreased and mean trace concentrations were as low as measured during adult anesthesia, resulting in overall low mean environmental concentrations.
The authors attribute their overall good results to:
- A relatively short period of high exposure (induction) and a relatively long period of low exposure (maintenance of anesthesia during eye muscle surgery).
- Good ventilation in the operating room with 20 air changes/hr and no recirculation.
- Low rate of leak from the breathing system.
- Central scavenging of waste gases.
- Turning off N2O flowmeter and anesthetic vaporizer during laryngoscopy and intubation.
- The presence of an anesthesiologist experienced in performing mask inductions in children.
Other factors that may also have contributed is the fact that relatively low concentrations of halogenated agents were used for induction (max. conc. Sevoflurane 3.2 vol% and halothane 1.6 vol%). The lack of preanesthetic medication in the patients in this study would likely have increased the amount of contamination present during induction. The fact that the ages of the patients studied were not presented in the report makes it difficult to gauge the relative contributions of these factors.
Return to the Current Literature Review Front Page, or read the abstract:
ABSTRACT
We report the findings of a study on exposure of operating room staff to sevoflurane, halothane and nitrous oxide during induction and maintenance of aneasthesia in children. Concentrations of anaesthetic agents in the operating theatre were measured directly by highly sensitive, photoacoustic infrared spectrometer during 20 aneasthetics.
Samples were taken from the breathing zones of the aneathetist and the circulating nurse. The operating theatre was of modern design with an airconditioning system providing 20 changes of air each hour. The threshold values of 100ppm N2O, 50 ppm isoflurane and 10ppm halothane recommended by the United Kingdom Committee for Occupational Safety and Health (COSH) were exceeded in several cases for a short time during mask induction.
After tracheal intubation, trace concentrations of sevoflurane, halothane and N2O were mostly under the recommended levels and comparable to levels measured during adult anaesthesia.
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