Risk of gaseous residues
Dr. Daniel J. Sanchez Silva
Translation: Transworld, Language Solutions
http://www.portalesmedicos.com/traductores-medicina/transworld
Introduction:
Exposure to anesthetic gases is a typical example of non biological pollution in hospitals. The presence of high concentrations of anesthetic gases or vapors in the operating and resuscitation rooms ' environment air is very common, specially in all those cases in which measures to avoid this from happening are not taken. The health risks this exposure presents as a consequence are a cause of great controversy: because of being technically simple, measures to reduce risks’ environment concentrations are suggested to be taken.
In the 1840 - 1850 decade, the use of inhaled anesthetics was started. Ethyl ether, nitrous oxide and chloroform were the first inhaled anesthetics used. Many years later (1930 - 1940), cyclopropane and trichloroethylene were introduced as anesthetics and in the 1950 - 1960 decade, fluoroxene, halothane and metoxifluorane were started to be used. With the passing of time and as a consequence of research works, new halogenated anesthetic gases were developed, which were less flammable and toxic. Fluoroxene, halothane, metoxifluorane, enflurane and isoflurane were introduced in the ‘80s and desflurane was introduced in the ‘90s. By the end of the XX century, sevoflurane was already started to be used. It is considered to be the ideal inhaled anesthetic at the beginning of the XXI century. All these anesthetic gases, except for nitrogen protoxide – which is a gas - are liquids which are administered through vaporization. The quantities and mixtures administered to each patient depend on the patient’s nature and pathology, on the kind of anesthesia they want to obtain and on each anesthetist’s habit. The fact that the intravenous agents (pharmacological anesthesia) are more frequently used, allows the inhaled anesthetics’ concentrations used to be progressively lower. It certainly seems that, the arrival of inhaling anesthesia brought exposure to anesthetic gases and residues and their subsequent consequences.
Exposed staff
The number of workers professionally exposed to anesthetic gases is high, since it is not only the anesthesia’s specialized staff but also other people going into the operating room (surgeons, health technical assistants and aides), as well as dentists who perform dental interventions, delivery room’s staff and also vets. Also, the presence of anesthetic gases is detected in resuscitation rooms, where they are exhaled by patients in their recovery periods after having been anesthetized.
Effects on health
Acute toxicity of halogenated gases such as chloroform, halothane and enflurane is well documented. Exposure to high concentrations of these gases – for instance, concentration required for anesthesia induction - cause liver injuries and is harmful to the renal system. Research made on animals reinforces the evidence of the side effects on the liver and kidney as a consequence of exposure to these gases.
The new anesthetic gases introduced after the year 1977 are considered to be less toxic than the first ones (more “secure”), even though slight and temporary injuries have been mentioned in the bibliography. These injuries are associated with acute exposure to isoflurane, sevoflurane and desflurane at the concentration levels required by anesthesia (1000 to 10000 ppm, depending on the gas). Injuries or hepatic necrosis hardly ever occur. In charts 2 and 3, available toxicological data is summarized.
As from 1967, a great number of epidemiological works have been published. These works aim at studying anesthetic gases’ effects – usually nitrous oxide and halothane – on exposed people. The analyzed effects are: A rise in miscarriages in women exposed during or before pregnancy, and even in wives of exposed male workers, a rise in congenital malformation in children of exposed mothers, hepatic, renal and neurological problems signs, and also some kinds of cancer problems.
A. Y. Abisman, the Russian physician, was the first researcher who made people notice anesthetics’ abortion-tetratogenic action on women, in 1967. It was that year that he found a high miscarriages and premature deliveries incidence in female anesthesiologists in his country, with side effects on other systems. Subsequent studies revealed a similar relationship occurring in all the areas where this problem had been analyzed, including the operating room’s staff. It seems reasonable to ask this staff to avoid non unpolluted centers, at least during the first pregnancy quarter.
The possibility that the operating room’s staff is exposed to a higher risk of carcinogenesis must be analyzed by taking into consideration the following aspects: existence or non existence of immunological changes, evidence of tumors found in animals used for experiments and statistical analysis of exposed staff.
The effect of the nitrous oxide on the bone marrow after chronic exposure is well known. Also, the existence of biphenilic polibrominate compounds lead to the appearance of hepatic tumors. As previously stated, this is a controversial issue. It is true that statistics tend to show a rise in the different kinds of cancer affecting surgical area staff in relationship with the rest of the population; however, it is kind of risky to attribute such result to the action of anesthetic agents and its metabolites. It is more logical to think that the major morbility caused by neoplastic illnesses and which affects the surgical area staff, is originated by the addition of several effects such as stress and radiation in which chronic inhalation plays a major role. Chronic toxicity as a consequence of organic discutients produces an extraction of lipoid substances, whose consequences appear as headaches, asthenia, vertigo, sleepiness and emotional irritability, among other symptoms.
The possible toxic effect of pollution in the operating room increases psychic depression together with behavioral disorders which at the same time result in a great number of suicides among anesthesiologists in comparison with general population, although stress and work and life styles are considered to be the predominant factor leading to such suicides.
All the inhaled agents, even the most modern, produce a great amount of deleterious effects; however, an irrefutable cause-effect relationship is not always able to be confirmed.
Headache is the most common symptom and has a clear etiopathogenic correlation. Anesthetic agents would depress brain’s oxidative mechanisms in direct relationship with the drug concentration which is spread in the environment or by the brain flow’s hemodynamia modification. To sum up, we must think that if there were any damage, it would be more related to subanesthetic concentrations’ pharmacological action than to a toxic response.
Enzymatic induction generated by different kinds of drugs constitutes an alternative mechanism. Chronic administration of substances may increase the metabolic transformation of other substances used in anesthesia, thus modifying the drug’s enzymatic unfolding and altering response’s intensity and action’s duration.
Once all the research works have been analyzed, an acceptable relationship between exposure and risk increase, especially in the first mentioned effects, can be inferred. Cohen carried out some research for ASA (AAS- Anesthesiologists American Society). At first sight, his published works constitute a quite conclusive set in this sense. Subsequent revisions accept these correlations, although accompanied by a strong critic to the technical aspects of the performed samplings, especially regarding the appropriate choice of the control group, concentrations to which the exposed group has been subject to, false positive elimination, non controlled habits (tobacco and alcohol), previous gynecological history, voluntary infertility, etc.
Last turned up revisions are even more critical. They suggest that for those exposure-effects relationships to be accepted with guarantee, they should be checked through new epidemiologic studies, since the previous ones can not be considered as valid enough. Although a great concern and a deep conviction of the existence of an exposure-effect relationship on the side of the majority of the exposed people has been confirmed, it is very difficult, in light of the current available information, to specify these relationships between exposure and quantitative effect in a rigorous way and from the statistical point of view.