Portal de Periódicos da CAPES

Editorial I

2002; Elsevier BV; Volume: 89; Issue: 2 Linguagem: Inglês

10.1093/bja/aef180

1471-6771

David J. Baker,

Zoonotic diseases and public health

Following the attacks in New York in September 2001, the spectre of urban attack by terrorists using chemical and biological warfare (CBW) agents again raised its head and led to a wave of speculation and near panic on both sides of the Atlantic Ocean. Newspaper articles about ‘weapons of mass destruction’ abounded, and emergency and hospital medical services made provisions for the management of large numbers of casualties. In the United States, mass ingestion of prophylactic antibiotics began and gas masks were purchased in large numbers. Television pictures of emergency personnel clad in protective suits (many of them totally inappropriate for the real degree of risk) were widely transmitted and for several weeks the public awaited a world-wide chemical/biological Armageddon. In the event, the reality was confined to the distribution of anthrax spores through the US postal system, which fortunately claimed only a few lives.1Borio L Frank D Mani V. Death due to bioterrorism‐related anthrax. Report of two patients.JAMA. 2001; 286: 2554-2559Crossref PubMed Scopus (150) Google Scholar Nevertheless this attack, coming after the use of a military organophosphate nerve agent by terrorists in Japan in 1995,2Morita H Yariagisawa N Nakaji T et al.Sarin poisoning in Matsumoto, Japan.Lancet. 1995; 345: 290Google Scholar 3Okumura T Suzuki K Fukada A et al.The Tokyo subway Sarin attack. Disaster management, part 2: hospital response.Acad Emerg Med. 1998; 5: 618-624Crossref PubMed Scopus (230) Google Scholar demonstrated that urban chemical and biological attack was possible and posed a problem for emergency and hospital medical services around the world. The risk of deliberate urban release of chemical and biological agents persists and is not new.4Sidell FR. Chemical agent terrorism.Ann Emerg Med. 1996; 28: 223-224PubMed Google Scholar From the point of view of casualty management, it is important that the momentum generated by the events of last autumn should be sustained. The appearance in this issue of a review5White SM. Chemical and biological weapons: implications for anaesthetic and intensive care.Br J Anaesth. 2002; 89: 306-324Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar concerning the implications of chemical and biological agents for anaesthesia and intensive care is therefore very appropriate. Many clinical specialities may be involved in the management of CBW casualties, but that of anaesthesia and intensive care has a critical role to play since the speciality, more than most others, has the academic background in physiology, applied pharmacology and pathophysiology, and is able to understand the injuries provoked by CBW agents. More importantly, it is able to respond with immediate and continuing life support. It is therefore essential that anaesthetists should be closely involved in the management of CBW casualties and should be properly informed about the risks and the special handling procedures required. Most busy anaesthetists do not have ready access to information about CBW agents. White has produced a useful, comprehensive document detailing a wide range of chemicals, toxins and organisms that have been proven or suspected to be agents of warfare, and more recently of urban terrorist attack.5White SM. Chemical and biological weapons: implications for anaesthetic and intensive care.Br J Anaesth. 2002; 89: 306-324Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar Two points about the extensive range of hazards presented in the review are particularly important. First, despite widespread public and political belief, biological and chemical agents are not strictly weapons of mass destruction but weapons of mass injury, a point recognized by a number of clinical experts including an ex-Soviet source.6Alibek K. Biohazard. Arrow Books, London1999: 22Google Scholar In this respect, they may lead to mass fatalities where medical resources are limited or non-existent, but with properly organized and equipped medical services the picture may be quite different. Unlike nuclear weapons, biological and chemical agents do not cause mass destruction of material and physical trauma. Biological and chemical agents should therefore be viewed in their own pathophysiological context. The persistence of the Nuclear, Biological and Chemical (NBC) classification owes more to diplomatic manipulation and the balance of military power than medical reality. White has appropriately classified CBW agents as weapons of mass injury rather than destruction,5White SM. Chemical and biological weapons: implications for anaesthetic and intensive care.Br J Anaesth. 2002; 89: 306-324Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar which is a more realistic term for anaesthetists used to the business of supporting life in difficult circumstances. This does not alter the fact that, untreated, CBW agents may lead to substantial loss of life. However, advanced life support and guidelines for longer term treatment do exist,7Baker DJ. Advanced life support for toxic injuries (TOXALS).Eur J Emerg Med. 1996; 3: 327-348Crossref Scopus (31) Google Scholar 8Baker DJ. Management of respiratory failure in toxic disasters.Resuscitation. 1999; 42: 125-131Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar and can radically alter the clinical picture. Secondly, it is important to realize that not all the hazards listed in the review are equally likely to be used by terrorists. A few have been identified and used, such as sarin and anthrax.1Borio L Frank D Mani V. Death due to bioterrorism‐related anthrax. Report of two patients.JAMA. 2001; 286: 2554-2559Crossref PubMed Scopus (150) Google Scholar, 2Morita H Yariagisawa N Nakaji T et al.Sarin poisoning in Matsumoto, Japan.Lancet. 1995; 345: 290Google Scholar, 3Okumura T Suzuki K Fukada A et al.The Tokyo subway Sarin attack. Disaster management, part 2: hospital response.Acad Emerg Med. 1998; 5: 618-624Crossref PubMed Scopus (230) Google Scholar 9Abramova FA Grinberg LM Yampolskaya OV Walker DH. Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979.Proc Natl Acad Sci USA. 1993; 90: 2291-2294Crossref PubMed Scopus (338) Google Scholar Most, however, are still confined to the area of speculation (sometimes backed by intelligence information). The existence of a hazard does not necessarily imply a threat, a term which implies a means of delivery and intention on the part of the assailant, apart from possession of a hazard. In terms of planning and training, it is more realistic and less nihilistic to build from experience of chemical hazards that have or could be used by terrorists, backed by experience gained from industrial toxic release. Knowledge of the management of naturally occurring epidemics is equally valuable for the management of a deliberately induced epidemic (a biological weapon attack). For those clinicians who feel they have a lack of experience in such cases, it is worth noting that considerable clinical analogous experience exists, which can be used in the management of unfamiliar pathology.10Moles TM Baker DJ. Clinical analogies for the management of toxic trauma.Resuscitation. 1999; 42: 125-131Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar For anaesthetists in particular, the essential life support procedures involved are very familiar from more conventional areas of practice. In civil life, populations are at constant risk from accidental exposure to toxic substances, as they are from naturally occurring epidemics. These are the natural equivalents of the intentional toxic release and epidemics that constitute CBW. Accidental civil toxic releases are managed according to the United Nations-controlled, hazardous materials control system (HAZMAT), which provides detailed information to emergency services about the properties and management of toxic substances at their place of use or while they are in transit.11Borak J Callan M Abbott W. Hazardous Materials Exposure: Emergency Response and Patient Care. Prentice Hall Inc., New Jersey1991Google Scholar, 12Moles TM. Emergency Medical Services Systems and HAZMAT major incidents.Resuscitation. 1999; 42: 103-116Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar, 13Organisation of Economic Co‐operation and Development (OECD) Health Aspects of Chemical Accidents: Guidance on Chemical Accident Awareness, Preparedness and Response for Health Professionals and Emergency Responders. OECD Environment Monograph No. 81 (OCDE/GD(94)1), Paris1994Google Scholar HAZMAT databases provide information for protection and decontamination, and clinical management protocols.14Bronstein AC Currance PL. Emergency Care for Hazardous Materials Exposure. 2nd Edn. 1994Google Scholar 15US Dept of Health and Human Services (Agency for Toxic Substances and Disease Registry) Managing Hazardous Materials Incidents – Vols 1–3. 1996Google Scholar The system is designed to manage accidental releases but provides a valuable framework for the management of casualties from deliberate releases. The difference between accidental and deliberate (terrorist) releases is that the identity of the toxic agent may not be known with certainty in the case of the latter, and so measures must be put into place that cover the worst case scenario of the agent being highly toxic, persistent and transmissible. Most HAZMAT incidents involve small numbers of casualties with varying degrees of exposure. Some of these may have the effects of both toxic and conventional trauma, for example after an explosion, such as that which occurred at a chemical factory in Toulouse, France in September 2001. The notion of mass casualties may not always therefore be appropriate, although both chemical and biological accidental releases have occurred in the past, giving rise to large numbers of injured and dead.9Abramova FA Grinberg LM Yampolskaya OV Walker DH. Pathology of inhalational anthrax in 42 cases from the Sverdlovsk outbreak of 1979.Proc Natl Acad Sci USA. 1993; 90: 2291-2294Crossref PubMed Scopus (338) Google Scholar 16Anonymous Calamity at Bho Pal.Lancet. 1984; ii: 1378-1379Google Scholar 17Mehta PS Mehta AS Mehta SJ et al.Bhopal tragedy’s health effects: a review of methyl isocyanate toxicity.JAMA. 1990; 264: 2781-2787Crossref PubMed Scopus (78) Google Scholar Much information exists about the management of HAZMAT incidents and the author has made good use of the internet sources that are now available. HAZMAT is a valuable model and all anaesthetists involved in disaster management should be aware of the stages in the overall management of a HAZMAT incident, and of the risks related to the toxicity, latency of action, persistency and transmissibility of the agents involved.18Baker DJ. Anesthesia in extreme environmental conditions, part 2: chemical and biologic warfare.in: Grande CG Textbook of Trauma Anesthesia and Critical Care. Mosby‐Year Book Inc., Baltimore1993: 1320-1354Google Scholar These four characteristics are common to both chemical and biological agents, and determine the degree of risk as well as the appropriate reponse. Toxicity is a familiar concept in anaesthesia, and toxic effects appear with a specific latency, which is important for the use of agents in deliberate release. In general, chemical agents and toxins have short periods of latency before specific signs and symptoms appear. In contrast, classical biological warfare agents have extended latency periods (usually familiar as incubation periods) before the effects of the induced disease begin to appear. Persistency relates to the ability of a toxic agent to remain in the environment into which it had been released and is a function of the physico-chemical properties of the agent. For chemical agents, the persistency may be variable but for most biological warfare agents, with the exception of spore-forming agents such as anthrax, persistency is usually very short. However, transmissibility may take place as a result of the physical contamination of the victim due to a persistent chemical agent or as a result of infection in the case of an airborne agent. Transmissibility is therefore a potential menace in the case of biological warfare agents because of infection down the casualty management line. Many known chemical agents (e.g. chlorine, phosgene and hydrogen cyanide) are readily available industrially and their properties are listed in standard sources and databases, which are cited in the review in this issue. Others, such as organophosphates, are familiar as pesticides but are also used by the military as nerve agents that may be synthesized in improvised laboratories. Certain biological warfare agents are recognized as being a more likely threat than others, given the difficulty of delivery and the sensitivity of the agents to meteorological conditions. Thus, anthrax is now an established threat that is more important than the rare viral haemorrhagic fevers, which are the domain of specialist physicians. It is important that biological attack should be viewed as a special case of an epidemic. Following CBW attack, anaesthetists may be involved at several points,18Baker DJ. Anesthesia in extreme environmental conditions, part 2: chemical and biologic warfare.in: Grande CG Textbook of Trauma Anesthesia and Critical Care. Mosby‐Year Book Inc., Baltimore1993: 1320-1354Google Scholar and are thus in danger of primary and secondary exposure. In some countries, anaesthetists form part of the primary emergency response and are familiar with the dangers of toxic exposure and the need for protection and decontamination. Anaesthetists may also be involved in management in the emergency room, operating theatre management and the intensive care unit. In France, special plans were put in place for the management of terrorist toxic release following the Japanese sarin attacks in 1995,19Laurent JF Richter F Michel A. Management of victims of urban chemical attack: the French approach.Resuscitation. 1999; 42: 141-149Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar which have been recently modified as Plan Biotox. The plans provide special mobile medical response teams (with training and protective suits) as well as protected medical teams to receive casualties who escape the HAZMAT cordon. Anaesthetists are involved at both these points and must have a good understanding of the importance of casualty decontamination.20Fisher J Morgan‐Jones D Murray V et al.Chemical Incident Management for Accident and Emergency Clinicians. The Stationery Office, London1999: 27-29Google Scholar In the hospital, anaesthetists must be aware of the effects of certain toxic agents on the conduct of general anaesthesia for the management of accompanying physical trauma. There are effects on the status of the patient before an operation and on the anaesthetic agents themselves.21Weinbroum AA Rudick V Paret G Kluger Y Abraham RB. Anaesthesia and critical care considerations in nerve agent trauma casualties.Resuscitation. 2000; 47: 113-123Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar A good example is the effects of exposure to organophosphate anticholinesterases on the action of neuromuscular blocking agents, which is covered by White.5White SM. Chemical and biological weapons: implications for anaesthetic and intensive care.Br J Anaesth. 2002; 89: 306-324Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar Many toxic hazards have long latency effects, which lead to the necessary management of patients in the ICU. Long-term ventilation may be required for neuromuscular problems, toxic pulmonary oedema and associated adult respiratory distress syndrome. Mass toxic casualties will place a heavy burden upon emergency and intensive care services as a result of the short and longer term actions of toxic agents. Attacks using bacterial and viral biological agents essentially pose the problem of epidemic infection, although intensivists are required for the management of the resulting complications, including multiple organ failure. There is a long latency in most cases, but there may be ultra-short and intermediate latency effects if a bacterial toxin is used as a toxic agent. Toxic agents may attack all somatic systems, but the respiratory system is the most vulnerable in the short and intermediate term, leading to fatality in some cases if resuscitation is not started early and continued. There are many pathophysiological processes leading to respiratory failure after toxic injury, affecting both the airway, and the control and mechanics of breathing.8Baker DJ. Management of respiratory failure in toxic disasters.Resuscitation. 1999; 42: 125-131Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar There may be, as in the case of organophosphates, failure of the respiratory centres and paralysis of the muscles of breathing through neuromuscular blockade. The review covers this in some detail.5White SM. Chemical and biological weapons: implications for anaesthetic and intensive care.Br J Anaesth. 2002; 89: 306-324Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar The more water-soluble toxic agents, such as chlorine, cause irritation and the production of secretions in the nasopharynx with laryngeal spasm. There may be blockage of the main airways with bronchial and bronchiolar constriction. Finally, many toxic substances act at the level of the alveoli causing toxic pulmonary oedema.17Mehta PS Mehta AS Mehta SJ et al.Bhopal tragedy’s health effects: a review of methyl isocyanate toxicity.JAMA. 1990; 264: 2781-2787Crossref PubMed Scopus (78) Google Scholar 22Matthew BB Krishna G. Phosgene poisoning.in: Somani SM Chemical Warfare Agents. Academic Press, New York1992: 237-250Google Scholar Both the central and peripheral nervous systems may be affected as in the case of sarin poisoning, where the respiratory centres are depressed and there is a depolarizing neuromuscular block. The airways may be affected at both the upper and lower levels with cough and laryngeal spasm, production of secretions and vomitus, bronchospasm, bronchiolitis and toxic pulmonary oedema. Many substances produce ciliary paralysis, which compounds the bronchial problem. Clinically, the combined effects are to produce increased airway resistance and reduced compliance. This leads to a failure of alveolar ventilation, a rise in end-tidal carbon dioxide, hypoxia and cardiac arrest. Anaesthetists clearly have a vital role to play in the management of CBW casualties, but in many countries their involvement with planning and provision of care has been relatively limited, particularly in the prehospital and emergency room areas. Many of the special government CBW advisers are from the public health, toxicology and pathology specialities. They do not have first hand experience of the emergency and intensive care life support measures required to break the link between mass injury and mass loss of life. It is important for anaesthetic professional bodies to take an interest in the subject and explain the role anaesthetists have to play in the management of chemical agent injury. For the general public, most of whom are still unaware that anaesthetists are medical practitioners, this may be something of a revelation. Training and close integration of anaesthetists into toxic emergency response teams is essential, but training by exercise is notoriously difficult for busy clinicians who have more than enough real problems to deal with. Nevertheless, it is vital that anaesthetists understand the real risks from CBW and the HAZMAT procedures to avoid becoming the next casualty. Above all, the speciality must give out a clear and positive message about the real dangers of CBW, and the appropriate planning and life support procedures that should form the medical response. This will not only serve to provide some comfort to a frightened general public, but will provide much needed focus for the rational management of casualties from a CBW attack.