Propofol Concentration In The Ambient Air Of The Operating Room And In The Blood Of Anesthesia Care Providers

Overview

The pollution of the operating room environment by anesthetic agents had been questioned, studied and documented in the past. These investigations demonstrated the existence of teratogenic effects in animals and the possibility of a decrease in mental performance, reduced fertility, fetal loss, spontaneous abortion and addictive potential in humans with chronic exposure to trace amounts of anesthetic agents. These findings led to the establishment of exposure limits and industry standards by consumer protection agencies, such as National Institute for Occupational Safety and Health (NIOSH). However, these standards applied to inhalation anesthetic agents that were excreted from the lungs of patients during expiration. These concerns about operating room pollution weaned away with the introduction of intravenous anesthetic agents, such as propofol, because it was believed propofol was excreted by systems other than the lungs. Recent research points to the contrary and demonstrates the excretion of propofol vapor in the expired gases of patients. Furthermore, animal experiments in our laboratory establish the existence of a biological mechanism responsible for addiction in animals exposed to trace amounts of propofol. We propose to study the exposure levels of anesthesia care providers in the operating room, during propofol use, under standardized conditions. Our findings will help to establish preventive measures for propofol addiction in anesthesia care providers.

This clinical project will be carried out in the operating rooms of the University Hospital and the Doctors Office Center. The study will be done during routine surgery where a laryngeal mask airway will be used to maintain airway during general anesthesia in 20 adult patients with American Society of Anesthesiologists physical status I or II. Routine anesthetic care standards will be applied in intravenous line placement and monitoring of patients. General anesthesia will be induced with a bolus dose of propofol (2mg.kg-1) and maintained with an intravenous infusion of propofol (100-200 mcg.kg-1.min-1). Patients will be allowed to breathe spontaneously 40% oxygen in air. Adjuvant intravenous medications will be given for amnesia, analgesia and infection prophylaxis as per routine anesthetic practice. The ambient propofol concentration will be measured, using a proton transfer reaction mass spectrometer (PTR-MS), at a distance of 25cm from the patient's face. The measurement of ambient propofol concentration will begin before the administration of propofol to the patient and will continue till the patient leaves the operating room. The use of PTR-MS device will not interfere with the anesthetic management of patient. In an unforeseen circumstance, where the anesthesiologist determines the use of PTR-MS does interfere with the anesthetic care of the patient, the device will be immediately removed and the measurement of ambient propofol concentration will be suspended for the case. The set-up and usage of PTR-MS will be performed by a research team that does not take part in the clinical management of the patient. The PTR-MS is a device that depends on the proton transfer reaction to quantify, in parts per billion (ppb) by volume, volatile organic compounds in air at extremely low concentrations and in real time. The mean and peak ambient propofol concentration will be determined during each case and a time weighted average (TWA) will be calculated for an eight-hour period at the end of the study. In addition, after receiving written informed consent from anesthesia care providers, blood samples will be drawn from them and propofol concentrations will be measured by high-performance liquid chromatography (HPLC) within 24hr. The blood samples will constitute 3ml on two occasions, one early in the morning before anesthesia care starts and one after eight hours of anesthesia care. HPLC is a device that uses a spectrofluorometric detector to estimate trace amounts of propofol in blood in ng.ml-1. The blood estimation of propofol will also be conducted by a research team that does not take part in the clinical management of patients.