WHAT THIS REPORT ADDS:

• Because the threat of terrorism remains a reality in this country, all health care professionals should be prepared to assist in the provision of emergency care.

ORLANDO, FLA—Sadly, the threat of another terrorist attack is never far from most Americans’ minds. But this threat is particularly pertinent for health professionals, who must grapple with a number of important questions: How can emergency health care systems better prepare for such events? What should physicians and nurses who are not part of these systems know in case they have to lend assistance during an emergency? And what can be done to increase readiness for disasters that are thought likely to occur sooner or later, such as the detonation of a “dirty bomb” or the release of chemical agents in populated areas?

Multiple presenters addressed these questions during the annual meeting of the American College of Chest Physicians in Orlando, Florida.[1] They all agreed that health professionals not usually involved in providing emergency care should be ready to lend a hand during disasters since first-response systems may be stretched beyond their limits.

INHALATION INJURIES

Pulmonary and critical care physicians, for example, may be needed to help deal with inhalation injuries. Such injuries are common during building collapses and fires, but they may also result from explosions or release of poisonous gas, noted Dorsett D. Smith, MD.

Immediate corticosteroid therapy is probably not indicated for patients with inhalation injury, said Dr. Smith, an expert in disaster medicine and a practicing physician in Everett, Washington. “Corticosteroids are unlikely to be helpful during the acute phase of alveolar damage because of the nature of the damage,” he said. In fact, most cases of mild inhalation injury resolve with no medical therapy. However, patients with more severe injuries that do not improve much after three or four days of supportive care may benefit from 60 mg of prednisone daily for 10 days.

During a disaster, physicians may want to consider treating more severe inhalation injuries during the acute phase with agents that are not necessarily approved for such use. Some of the choices include N-acetylcysteine, xanthine oxidase inhibitors, phosphodiasterase inhibitors, tumor necrosis factor alpha (TNF-alpha) inhibitors, nitric oxide synthase inhibitors, angiotensin-converting enzyme (ACE) inhibitors, and vitamin E. These agents may improve acute lung injury (ALI) through various mechanisms. The ACE inhibitor losartan, for example, has been shown to decrease collagen deposition in the lungs of rats with ALI. Treatment with a TNF-alpha inhibitor may reduce the lung inflammation associated with inhalational injury.

Dr. Smith also offered advice on providing mechanical ventilation to victims of inhalational injury: “Do not do it unless you absolutely have to and always use lung-protective ventilation,” he said.

CHEMICAL AGENTS

The agents most likely to be used in a chemical weapons assault on civilian populations are commonly delivered in canisters, in smoke grenades, or with conventional explosives. A number of different agents could be used, said James A. Geiling, MD, Chief of Medical Service at the VA Medical Center in White River Junction, Vermont. One possibility is a vesicant such as mustard gas, which irritates the skin, eyes, and respiratory tract and suppresses bone marrow.

A chemical weapons attack could also deliver large quantities of opioids and barbiturates similar to those used by Chechen rebels to take more than 800 hostages in a Moscow theater in October 2002. Interestingly, the Russian military incapacitated the rebels with an aerosolized derivative of fentanyl, a calmative agent.

The chemical weapon that physicians have probably heard of most often is sarin nerve gas, the anticholinesterase agent that the Japanese cult group Aum Shinrikyo released into a Tokyo subway in 1995. Sarin is an organophosphorous cholinesterase inhibitor, a class of compounds which are essentially “super bug killers that work just like insecticides,” noted Dr. Geiling. Exposure can cause respiratory failure and death by paralyzing the muscles used in respiration. Exposure to these agents can also result in long-term neuropsychologic sequelae (such as anxiety, tenseness, and chronic memory decline) and also persistent peripheral neuropathy characterized by proximal muscle weakness and areflexia.

Phosgene gas is not as well known, but it can also cause respiratory failure within 48 hours (by triggering fluid build-up in the lungs), as well as irreversible lung fibrosis and emphysema.

Medical management of exposure to chemical weapons often begins with “dry decontamination,” which is simply getting victims out of their contaminated clothing and into a clean hospital gown. However, caregivers should be aware of the risk of “off gassing”—exposure to a chemical agent trapped in the victim’s clothes—at this time. Victims exposed to skin irritants require thorough cleansing, usually with plain soap and water.

The classic antidote for nerve agent exposures is the cholinergic receptor antagonist atropine; 2 mg of this drug “blocks the effect of the acetylcholine that is floating around,” Dr. Geiling said. Another common antidote, pralidoxime chloride, works by breaking the bond between nerve agents and acetylcholinesterase enzymes.

CONVENTIONAL EXPLOSIVES

Despite extensive media coverage of the threat of chemical and biological weapons, Americans are more likely to be injured in attacks with conventional explosives, claimed Pascal O. Udekwu, MBBS. “You must be involved in the disaster planning process at your hospital so that you can best care for and save as many of these people as possible,” stressed Dr. Udekwu, an Associate Professor of Surgery at the University of North Carolina in Raleigh.

Initially, the blast from a conventional explosive is most likely to damage the ears, gastrointestinal tract, and respiratory tract. Further trauma often occurs from burns and from propelled debris, such as dirt, stones, other natural material, shell casings, and body parts.

“In addition to the standard acute lung injury, you can also have significant air embolism,” Dr. Udekwu warned. Bronchoscopy may reveal large air leaks; it can also be used to guide the surgical repair of such leaks.

Quick action may be necessary to provide an airway for those with severe respiratory distress, said Dr. Udekwu. He suggested conventional mechanical ventilation in these cases because “pulmonary injuries can be rapidly progressive” and lead to death.

Notably, blast victims may present with colonic perforation that must be found early to prevent sepsis. “Perforated hollow viscous or other injuries will have a significant impact on morbidity and mortality in these patients after you have managed their initial airway and oxygenation issues,” Dr. Udekwu noted.

—Timothy Begany

Reference
1. Lazarus AA, Devereaux AV, Mohr LC, et al. Basic disaster medicine: beyond the first response. Presented at: annual meeting of the American College of Chest Physicians; October 26, 2003; Orlando, Fla.

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