Emergency War Surgery NATO Handbook: Part I: Types of Wounds and Injuries: Chapter VII: Mass Causalties in Thermonuclear Warfare

Specific Medical Effects of Nuclear Weapons

United States Department of Defense

Proper management of radiation casualties of nuclear war requires an understanding of the medical problems to be expected. Nuclear weapons are sufficiently different in their casualty producing potential from conventional weapons that the types of injuries will be different. It is important to understand these differences if triage and medical treatment are to be accomplished effectively and quickly. As has been said, the biologic effects of nuclear weapons are due to thermal burns, blast, and radiation injuries.

Thermal Burns. The extremely high temperatures produced by a nuclear explosion cause release of a large part of the energy in the form of thermal radiation. This radiation travels at the speed of light and is capable of producing severe burns at great distances. In nuclear warfare, burn casualties will constitute a large fraction of the patient load. All echelons of medical care must plan for this increased burden of thousands of burn cases.

A major problem will occur during the initial evacuation of bum patients if massive numbers of casualties must be handled. Sorting will be essential to conserve medical resources and should be done in accordance with the following criteria:

1. Cases involving 20% or less of the body surface should be treated on a outpatient basis or at minimal care facilities. These patients can care for themselves with minimal supervision. They will not be fit for duty and should not remain with their units if those units are actively engaged in combat.

2. Patients whose burns involve certain critical areas, such as the head and neck, hands, or feet will require hospitalization even if the total body surface involvement is less than 20%.

3. Patients with more than 20% body surface involvement, or with associated blast injuries, will require hospitalization for resuscitative treatment and surgical care.

4. Cases with more than 50% involvement have a decreasing chance of survival with increasing degree of involvement and should be given a low priority for needed surgical care. They should be retained in a delayed status in the minimal care section of a medical facility where they will be available for more extensive treatment if resources and time allow. It must be realized that young healthy adults, without other injury or disease, may be more likely to survive such burns with adequate treatment; thus, a rigid classification system denying them available treatment is not desirable.

All patients should receive as much treatment as possible and the above criteria must be flexible. However, any treatment must be accomplished as efficiently and quickly as possible, and long, time consuming procedures may have to be delayed, or not performed. The greatest good for the greatest number is best achieved by treating each patient as quickly and simply as possible by doing first what is essential to save his life, then what may be possible to save limbs, and last what might be required to save and restore function.

Depending on the weapon yield, some burn patients will have associated radiation injury and will develop bone marrow depression during the course of their illness. These patients cannot be recognized upon admission, since the bone marrow depression does not become clinically evident until after a latent period of 2-6 weeks after the radiation exposure. A blood count in such cases during the first few days after exposure will show a variable leukopenia, particularly of lymphocytes. These patients will have high morbidity and mortality rates due primarily to infection. Unless a procedure is required to save life, these patients should not be subjected to surgery during the phase of bone marrow depression. If there is no evidence of bone marrow recovery, the patient will not survive with the treatment modalities presently available in the field.

Blast Injuries. Blast injuries caused by nuclear detonations are of two types: direct (due to overpressure effects) or indirect (due to drag forces of the winds accompanying the blast wave). This latter category includes a wide variety of missile and translational injuries.

Direct blast injuries will be rare, since persons close enough to the point of detonation to sustain significant direct overpressures will almost invariably sustain lethal thermal and indirect-blast injuries. However, those few patients who survive the direct blast should be managed the same as any other direct blast injury. Their injuries will be complicated by other trauma and they will suffer a high incidence of radiation-induced bone marrow depression during their post-injury phase, resulting in increased morbidity and mortality. Direct blast-induced internal injuries can easily be overlooked in a mass casualty situation.

The blast wave of a nuclear detonation is unlike conventional blast waves in that its formation is associated with the production of severe, transient winds from the violent movement of large masses of air to form the wave itself. These blast winds, perpendicular to the plane of the wave, have velocities reaching several hundred kilometers per hour. They last only a few seconds but can produce considerable damage through drag forces and by the production of large numbers of low-velocity secondary missiles, the size and nature of which depend on the environment. A high percentage of blast trauma will be caused by such missiles, and a large number of patients will have multiple missile injuries. Many Japanese at Hiroshima and Nagasaki had dozens of superficial wounds caused by flying glass and debris. These types of injuries will vary greatly in severity, but in general, there will be a relatively low incidence of deeply penetrating injuries. However, when massive numbers of casualties must be quickly sorted and prepared for evacuation and treatment, a significant number will have penetrating wounds which might be overlooked until clinical signs become obvious. Otherwise, the nonpenetrating missile injuries will not be severely disabling unless critical parts of the body are involved, such as the head, face, neck, or hands.

Radiation Injuries. The detonation of a nuclear weapon produces large amounts of ionizing radiation in two basic forms: electromagnetic (gamma) radiation, which travels at the speed of light and is highly penetrating, and particulate (alpha, beta, and neutron) radiation. Of the particulate radiations, only the neutron is highly penetrating, whereas the alpha and beta are not. All four types are present at the time of the detonation, but the gamma and neutron are by far the most important clinically. All but the neutron radiation are present in fallout and, in this instance, the gamma is the most important.

Ionizing radiation is emitted both at the time of the nuclear detonation and for a considerable time afterward. That which is emitted at the time of the detonation is termed "prompt radiation", and is produced by the nuclear reactions of fission and fusion. The significant part of prompt radiation consists of a mixture of gamma and neutron radiation, most of which is emitted within a few seconds of the onset of the detonation. However, the duration of significant emission may be longer, particularly with larger weapons. One minute has been established as a reasonable time parameter; after which there is no significant amount of prompt radiation, regardless of the type of weapon or circumstances of the detonation.

Residual radiation is that which persists beyond the first minute after detonation. Its source is the variable amount of residual radioactive material produced by a nuclear detonation. A nuclear fission reaction transforms uranium or plutonium into a large number (about 150) of radioactive isotopes, termed fission products, which constitute by far the most important source of residual radiation. In addition, small amounts of unfissioned bomb material, and material in which neutron radiation has induced radioactivity, are present. All of these residually radioactive materials will be found in fallout.

Fission products are the major radiation hazard in fallout, since a large number of them emit penetrating gamma radiation and, as a result, can be hazardous even at great distances. They have half lives varying from fractions of seconds to several years, but most have half lives in the range of days to weeks. As a result, the total amount of radiation emitted by a typical mixture of fission products is quite intense early and remains hazardous until the activity decays to negligible levels. This takes several days to several weeks, depending on the original level of activity; however, some isotopes with very long half lives will be present and detectable for many years.

Figure 19 shows that fallout activity decays down to 1/10 of its initial level within seven hours post detonation. At H plus one hour a significant part of the early fallout will have deposited itself close to the point of detonation. Deviation from this decay curve will be common, depending on the interplay between the various factors controlling the rate of deposition of fallout and the distance involved. At greater distances from the point of detonation, it may take several hours before fallout will be deposited and become detectable. A significant amount of radioactive decay will have already occurred while the radioactive material has been airborne and, as a result, the rate of decay, once all the fallout is on the ground, will be similar to the later part of the curve shown in Figure 19. If fallout in a given area is a mixture from several detonations at different times, the observed rate of decay may be quite different from this ideal example. Under these circumstances, the rule of thumb that fallout will have decayed to negligible values by two weeks may not be applicable. It should be obvious that instruments designed to measure fallout activity must be available and used to evaluate the true hazard.

Figure 19

Not all the uranium or plutonium in a weapon is fissioned, and fallout, which contains residual weapon material, will contain small amounts of these elements. They add little to the hazards of fallout since they are alpha emitters and are not an external hazard unless ingested or inhaled. They must be incorporated into boas tissue to do damage and their relative insolubility greatly minimizes this hazard. Obviously, ingestion or inhalation of contaminated material should be avoided.

Because of the exceedingly high temperatures generated in a nuclear detonation, all the fission products and the weapon residues are vaporized. As they cool and recondense, they solidify as extremely small particles. In an airburst, these particles will remain suspended in the upper atmosphere (stratosphere) for long periods of time descending slowly over a period of years and over large parts of the earth's surface. This occurred during the atmospheric testing of weapons. Under such circumstances, there is no significant early or local fallout. When a detonation occurs within a certain critical distance of the surface, however; severe updrafts cause large amounts of terrain debris to be sucked up into the fireball. As a result, as the radioactive materials cool and condense, they become affixed to relatively large particles of dirt and debris. These large particles, with their radioactive contamination attached tend to fall back to earth rapidly and locally, resulting in high levels of radioactivity downwind from the point of detonation. On occasion, this type of fallout is visible while it descends.

The major hazard in this type of fallout will be external wholebody irradiation from gamma-emitting isotopes, since they do not actually have to be on a person's skin to cause damage. Gamma radiation has a very long range in air, and large amounts of gamma-emitting material scattered uniformly over many square kilometers can produce a high level of penetrating radiation, which is a hazard to anyone occupying or passing through the area, even though he avoids direct contact with the fallout material. Even personnel traveling through in vehicles will be exposed, although vehicles can provide significant reduction of exposure because of the ability of most metals at least partially to scatter or absorb gamma radiation. The dose rate inside a tank, for ex ample, may be only 4-10% of that outside.

The potential injury incurred from gamma radiation is a function of the amount of time spent in the fallout field as well as the dose rate present, since these factors together determine the total dose absorbed.

The beta-emitting isotopes in fallout are not a significant hazard, unless a person is directly contaminated with or ingests them. External contamination can result in a moderate degree of skin damage somewhat similar to a thermal burn, and incorporation into body tissues can result in organ damage of long-term significance. These later effects - that is, interferences with specific organ functions, carcinogenesis, and accelerated aging changes - are not manifested for months or years, and acute whole body irradiation, with resulting radiation sickness, will not occur. Therefore, in combat situations, the beta-emitting components of fallout are not considered to be a serious hazard.

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Operational Medicine 2001

Health Care in Military Settings

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