[Rischi lavorativi in ambiente sanitario]




     

Anaesthetics


Technical prevention

The regulation of the Ministry of Health n.5 of 1989 lists a number of technical interventions to be adopted in order to keep N2O pollution within 100 ppm:

  1. The employment of inhalation anaesthetics must be avoided before orotracheal intubation.
  2. Should it become necessary to employ sedation by use the inhalation anaesthetics, the perfect adhesion of the mask to the face must be assured, in order to prevent the dispersion of the anaesthetic in the environmental air.
  3. It is necessary to carry out a careful check of leakages:
    • From high pressure circuits (connections between the outlets of the centralized distribution system and the anaesthesia apparatus). The check must be carried out by carefully examining the leak proof of the pressing tubes bails, the tube thread and the spring clips.
      The most common leakage points are represented by:
      • the tubes for the connection to the centralized system
      • the high pressure circuit of the respirator.

Once the connection to the centralized system for the delivery of the protoxide has been opened, the pressure must be checked on the manometer of the anaesthesia apparatus. The pressure must be checked again one hour after the connection of the apparatus to the centralized system has ended; a drop in the pressure indicates a leakage.

    • From low pressure circuits (circuits of the anaesthesia apparatus, from the flowmeters to the patient). The check must be carried out by carefully examining the leak proof of the system.
      The most common leakage points are represented by:
      • Y connectors
      • non leak proof valve domes
      • circuit tubes leaky or wrongly assembled
      • absorption system
      • soda lime basket
      • by-pass tubes
      • thermal relief.

The functionality of the system can be verified by closing the bleed valve and junction Y. The oxygen (O2) stream required to maintain the pressure of the system stable at 40 cm H2O should not exceed 100 ml/min. The inspection must be carried out daily and, in any case, whenever the soda lime replacement takes place.

    • Should any component of the anaesthesia circuit not work properly, it is necessary to have spare parts ready available.
    • Evaporators with a closed charging system should be preferred rather then open systems. The charging operations should be carried out outside the operating theatre and, possibly, under a fume cupboard.
    • A prolonged oxygenation of the patient before extubation is desirable, in order to limit the emission of gas in environmental air.
    • It is advisable to close the rotameter gas at the end of the anaesthesia.
    • Furthermore, it is necessary to adopt suitable systems for the collection and outdoor disposal of the expired gases and of the gases deriving from the circuit. It is also necessary to periodically verify the efficiency of such systems.
    • It is necessary to supply an adequate number of air change: Torri recommends at least 8 air change per hour.
    • Programmed periodical servicing will be necessary to control the parameters that allow the evaluation of the efficiency of the machinery.



Medical prevention

According to the laws in force in our country, the health personnel exposed to inhalation anaesthetics should undergo health surveillance by occupational physician. Main reference rules, in Italy, are the regulation of the Ministry of Health n.5 of 14 March 1989, 384/90, 626/94 e 242/96.
Checks should be carried out according to the following criteria, as established by a special committee of the Società Italiana di Medicina del lavoro e Igiene industriale:

  • The first sanitary inspection should be carried out before exposure, in order to assess the operator's health and his/her fitness for work before employment. Attention should be paid to any existing pathology of the haematopoietic system and of the other systems usually involved in disorders arising from occupational exposure to anaesthetics. The first assessment should include a detailed history taking and examination; in particular, it is very important to assess the functionality of the Central and Peripheral Nervous System. Laboratory investigations should include a full blood count with differential white cell count and platelets, liver function tests and an ECG.
  • Further sanitary inspections should be carried out periodically.

The regulation of the Ministry of Health n.5 of 1989 suggests that the inspections be carried out every three months in order to assess the health condition of the operating theatre personnel. However, at present the best periodicity for the surveillance is considered to be annual. The blood tests and the liver function tests should be carried out again during the periodical checks. Should any test result be abnormal, this result will address further diagnostic procedures: for example, should a disorder of the peripheral nervous system be suspected, an electromyography would be recommended.

Suggested periodicity for the environmental and biological surveillance of the health personnel exposed to anaesthetic gases, on the basis of intensity of exposure.*

N2O ambientale (ppm)

N2O urinary (mcg/l)

Periodicity of sanitary inspections
<100 >

 

 <55 >

 

annual

100-300

55-160

biannual

>300

>160

quaterly


*(Study Group on the environmental monitoring, biological monitoring and health surveillance of hospital workers in Lombardy)

 

[collegamenti]




Operating theatres


Operating theatres


Anaesthetics