Nuclear, Biologic, & Chemical Agents; Weapons of Mass Destruction

INTRODUCTION

For centuries, military forces have utilized nonconventional weapons using various chemical and biologic agents. During World War I, powerful chemical weapons were developed that affected hundreds of thousands of soldiers. Nuclear weapons were first created during World War II with devastating results. Today, thousands of these nuclear, biologic, and chemical weapons of mass destruction are stored in facilities throughout the world. An accident at any of these facilities could result in a large number of civilian casualties. In addition, many terrorist organizations are now actively attempting to purchase, steal, or develop such weapons for their use. As with most mass casualty situations, emergency physicians will be at the forefront of patient care. This chapter attempts to provide specific information regarding the management of nuclear, biologic, and chemical weapons injuries.

NUCLEAR WEAPONS

Introduction

A terrorist attack utilizing a nuclear weapon would most likely involve the detonation of a nuclear bomb or the detonation of a conventional explosive that also dispersed radioactive material (so-called dirty bomb).

General Considerations

The detonation of a nuclear weapon results in a much larger blast area and much hotter fireball than that produced by conventional explosives. If victims survive the blast trauma and thermal burns, they are at risk for radiation injuries. There are four types of radioactive particles that may cause damage when they interact with body tissue:

1. Alpha particles are large particles that are stopped by the epidermis and cause no significant external damage. Internal contamination, from the inhalation or ingestion of contaminated particles, may cause local tissue injury.

2. Beta particles are small particles that can penetrate the superficial skin and cause mild-burn-type injuries.

3. Gamma rays are high-energy particles that can enter tissues easily and cause significant damage to multiple body systems.

4. Neutrons are large particles that are typically produced only during nuclear detonation. Like gamma rays, they cause significant tissue injury.

The effect that radiation will have on the body depends on the type of radiation, the amount of exposure, and the body system involved. Tissues that display higher rates of cellular mitosis, such as the gastrointestinal and hematopoietic systems, are more severely affected. At very high radiation doses, neurovascular effects will also be seen. Radiation injury may cause either abnormal cell function or cell death.

Clinical Findings

A. Symptoms and Signs

The symptoms and signs of radiation exposure occur in three phases: prodromal, latent, and symptomatic.

1. Prodromal phase—Patients will develop nonspecific symptoms of nausea, vomiting, weakness, and fatigue. Symptoms generally last no longer than 24-48 hours. With higher radiation exposures, symptoms will occur earlier and last longer.

2. Latent period—The length of the latent period depends on the dose of radiation and the body system involved (neurologic, several hours; gastrointestinal, 1-7 days; hematopoietic, 2-6 weeks).

3. Symptomatic phase—Symptoms will depend largely on the body system affected, which will depend on the radiation dose. At doses of 0.7-4 gray (Gy), the hematopoietic system will begin to manifest signs and symptoms of bone marrow suppression. Because of their long life span, erythrocytes are less severely affected than are the myeloid and platelet cell lines. Neutropenia and thrombocytopenia may be significant and lead to infectious and hemorrhagic complications. At doses of 6-8 Gy, gastrointestinal symptoms develop. Nausea, vomiting, diarrhea (bloody), and severe fluid and electrolyte imbalances will occur. The neurovascular system becomes affected at doses of 20-40 Gy. Symptoms include headache, mental status changes, hypotension, focal neurologic changes, convulsions, and coma. Exposures in this range are uniformly fatal.

B. Laboratory and X-ray Findings

Obtain a complete blood count with differential for all patients sustaining a radiation injury. Although symptomatic bone marrow suppression may not be evident for some weeks, a drop of the absolute lymphocyte count of 50% at 24-48 hours is indicative of significant exposure. Monitor electrolytes in patients with gastrointestinal symptoms.

Treatment

In the absence of aggressive medical therapy, the LD50 (the dose of radiation that will kill 50% of those exposed) is approximately 3.5 Gy. Aggressive medical care affords improved survival. Treat all life-threatening injuries associated with blast or thermal effects according to standard advanced trauma life support protocols. Perform surgical procedures early to avoid the electrolyte and hematopoietic effects that will occur. Clean wounds extensively and close them as soon as possible to prevent infection. Treat nausea and vomiting with standard antiemetic medications (prochlorperazine, promethazine, ondansetron). Treat fluid and electrolyte abnormalities with appropriate replacement. Anemia and thrombocytopenia can be treated with transfusion therapy. Leukopenia may be treated with hematopoietic growth factors such as sargramostim and filgrastim. In some instances, bone marrow transplantation may be utilized. Follow neutropenic precautions at absolute neutrophil counts below 500. Some authors recommend prophylactic antibiotics at counts below 100. Use broad-spectrum antibiotics to treat infections. Infection is the most common cause of death in radiation patients.