- Picture, courtesy of Martha Hanssens Hospital in Oslo, Norway
The Problem
Operation Theatre staff in hospitals are put at risk daily not only from anaesthetic agents, but also from other substances used during operations. Many orthopedic surgeons use an acrylester plasticcement when they are replacing joints (i.e. hip, knee and elbow) with synthetic ones. Due to the type of plastic-cement and the importance of sterile handling, the plastic-cement is produced during the operation by mixing the acrylate with the monomer Methyl Methacrylate (MMA). Work of this kind with the acrylester often leads to the theatre staff complaining of headaches, as well as soreness in eyes and noses. MMA is a volatile liquid. Its fumes have a strong and characteristic smell and are known to irritate mucous membranes, such as those in the eyes and nose, even when the concentration levels are far below the permitted levels.
The Monitoring Need
In order to evaluate how much MMA personnel are exposed to, it is necessary to know both the average dose and the peak value of the MMA while they are working in the fumes. It is also necessary to evaluate the settings and efficiency of the ventilation system. Traditional methods of measuring MMA make it difficult to document the problem as it is not always possible to measure the peak levels or short term dosing levels of MMA during joint replacement operations. In addition to the MMA fumes, it is more than likely that the theatre staff are also exposed to anaesthetic gases.
The Solution
The Photoacoustic Multi-gas Monitor - INNOVA 1312 is well suited for this type of measurement. The monitor can measure both average, short-term and peak exposure levels of MMA. Furthermore, it only requires a few hours of training before it can be operated by hospital staff. The instrument was configured to measure Nitrous Oxide, Halothane, Enflurane, Isoflurane, 2-propanol, Carbon Dioxide and MMA. The filters used and the detection limits for these gases are shown in the table overleaf. Halothane, Enflurane and Isoflurane are all measured using the same filter. As they are not all present at the same time, this does not cause a problem. As one filter is sensitive to a number of gases, sometimes you need to compensate the readings obtained. The monitor is able to do this automatically if the interfering gases are measured separately with other filters (Cross Compensation) Carbon Dioxide was measured in order to compensate for interference on the Nitrous Oxide measurement, and 2-propanol is measured to compensate for interference to the anaesthetic gases.
The results in this application note were obtained during a hip replacement operation at Martha Hanssens Hospital in Oslo. The measurements were made in the area around the surgeons face during 2 consecutive, traditional hip replacement operations (two portions of MMA-plastic were used; one for securing the ball on the femur and the second for securing the socket on the pelvis). The operating room was normally ventilated (the air being completely changed approximately 20 times every hour; no special laminar airflow system is installed). The patient, during both operations, was under spinal anaesthetic, which does not require gaseous anaesthesia – thus simplifying measurements.
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