- Email: [email protected]
OR radiation hazards
John L Day, PhD David A Lightfoot, MA
OR radiation hazards Exposure to radiation in the operating room has been a matter of prime concern to the OR nurse. Constant vigilance for her own safety and strict adherence to all the precautionary rules can minimize problems. Fear of radiation has grown with the realization of its hazards. At the time of the discovery of x-rays by Wilhelm Conrad Roentgen in 1895 and of the radioactivity of pitchblend by Antoine Henri Becquerel in 1896, few if any persons had reasons
John L Day, PhD, a member of the Ionizing Radiation Control Committee at Hahnemann Medical College and Hospital, Philadelphia, is assistant professor in the Department of Radiation Therapy and Nuclear Medicine. He is a graduate o f the University of Michigan. David A Lightfoot, M A , is a certified radiological physicist and an assistant professor in the Department of Radiation Therapy and Medicine at Hahnemann. He is a graduate of Temple University, Philadelphia. This paper was supported b y the National Cancer Institute, the Alperin Foundation, and Friends of the Radiation Therapy Center.
to fear radiation. Perhaps the most widespread concern or fear then was whether peeping toms could use x-rays to see the naked flesh modestly hidden beneath layers of fashionable garments. As knowledge of the characteristics of x-rays and radioactivity expanded, this foolish concern was replaced by a wellfounded respect for the real hazard of radiation-its ability to modify molecules within body cells. The alteration of molecular structures may cause cell dysfunction, an alteration, delay, or permanent halt in cell replication, or cellular lysis. The observable effect of this depends on the nature of the cells affected and the nature and extent of the radiation exposure. For example, depending on the amount, a dose of radiation to the abdomen may cause death through intestinal bleeding or may cause no symptoms at all. This is because normally cells lining the intestine are being replaced constantly by newly formed cells. If a large dose of radiation temporarily halts new cell formation, the cells normally leaving the intestinal lining will not be replaced. Within a few days, as cells continue to leave the intestinal sur-
AORN Jozlmal, August 1974, Vol 20, No 2
249
face, too few cells will be left to spread over the walls of the intestine and bleeding will occur through seepage into the intestine. Infection and death may ensue. With a lower dose of radiation, fewer cell-forming centers will be affected and the loss of blood will not be enough to cause death. Recovery may be complete within a few days after new cell-formation resumes. In this case the radiation effect would not be much different than ordinary diarrhea. Small doses of radiation effecting only a few cell-formation centers may produce no noticeable symptoms a t all. In explaining radiation effects, scientists have relied on such descriptive terms as direct and indirect effects, latency, dose-effect relationships, threshold effects, equivalent dose, somatic and genetic effects, tolerance, and recovery and repair. These concepts are briefly defined as follows: Direct and indirect effects. The immediate damage within cells caused directly by the radiation or indirectly by the altered chemical molecules within the cells.
Latency. The damage remains hidden until some later time. Experience with radiation effects indicates radiation damage may remain latent or hidden for several years after exposure. Dose-effect relationships. The effect of radiation exposure is related to the amount and length of time of exposure. Too much exposure t o radiation may cause serious damage. Below certain levels of radiation exposure, there may be no noticeable damage even if the exposure is repeated for a working lifetime.
250
Threshold effects. Some types of radiation damage may never occur unless exposure exceeds a critical level called the dose threshold. If the critical level is extremely low (practically zero), the effect is referred to as a non-threshold effect. Once the dose-threshold is exceeded, the probability of damage increases as the dose is increased. Equivalent dose. This term applies to the quantity which expresses all radiations on a common scale for the purpose of calculating their biological effects. The unit of the equivalent dose is the rem. Equivalent doses cause equal damage regardless of the type of radiation responsible. Government regulations concerning permissible doses of radiation are based on units of equivalent dose. Somatic and genetic effects.Radiation damage observable in the exposed individual is a somatic effect. Radiation damage passed on to future generations is a genetic effect. The possibility of defective future generations is unlikely unless a major portion of the population receives a significant exposure. The probability of transmitting radiation damage to offspring also is lower than commonly feared since radiation damage to all cells is unlikely. An altered gene has only a 50% chance of being passed on if the ovum or sperm comes from the cell with the altered gene and may not even be observable in the offspring. There are several causes of genetic mutation other than radiation. Even with no radiation exposure, 4% to 5% of all births show congenital defects. It has been estimated that a radiation dose of 50-80 rem will increase the rate of genetic mutations to double its natural rate.
AORN Journal, August 1974, Vol 20, N o 2
Tolerance. Radiation tolerance, a term most appropriately used by radiation therapists, is somewhat analogous to the critical level in threshold effects. However, i t normally means a dosage level above which radiation effects become medically serious in a significant percentage of patients rather than a level below which no radiation effect is observable. Generally, highly differentiated cells which normally do not divide have a higher tolerance to radiation than rapidly dividing lessdifferentiated cells.
Recovery and repair. There are many indications that cells are able to recover from radiation damage. For example, cells which cease dividing because of radiation exposure may renew dividing in a few days if exposure is not too high. Repair occurs only if those cells able to escape or recover from radiation damage form new cells. These new cells, in turn, replace damaged cells. Are the risks caused by radiation balanced by the benefits? It is a difficult question to answer. Defining the risks and benefits is equally as difficult. For the critically ill patient, the risk of imminent death without x-ray examination may far exceed any imaginable risk created by radiation. The prevailing philosophy of the risk to the occupationally exposed worker is given in National Council on Radiation Protection and Measurements (NCRP) Report No 39: “The only statement that can be made a t the present time about the lifetime exposure of persons to penetrating radiation a t a permissible level considerably higher than the background radiation level, but within the range of radiological experience, is that appreciable injury
manifestable in the lifetime of the individual is extremely unlikely. It is, however, necessary to assume that any practical limit of exposure that may be set up today will involve some risk of possible harm. The problem is to make this risk so small that i t is readily acceptable to the average individual: that is, to make the risk essentially the same as is present in ordinary occupations not involving exposure to radiation.” Some ask, “Why not make the permissible dose zero?” Zero dose is impossible to achieve since man always has been subject to radiation from natural sources such as cosmic rays and naturally occurring radioactive materials. The medical use of x-rays and radioactive materials produced by nuclear reactors and nuclear bombs causes man to receive additional radiation dose. Arguments about the hazards of man-made sources of radiation sometimes ignore the hazards of alternatives. Until such time as suitable alternatives of lesser risk are available, eliminating the medical use of radiation would be more harmful than beneficial. However, some alternatives are better, such as, tuberculosis skin tests rather than chest x-rays. Generally, the government established limits of permissible radiation dose as 5 rem per year for occupationally exposed workers 18 years of age and older, and 0.5 rem per year for everyone else. The limits are over and above any radiation dosage received for medical reasons. A dose of 0.17 rem per year per person frequently is referred to as the average dose permissible from nuclear reactors and other sources. The intent of the complex government regulations is to limit occupa-
AORN Journal, August 1974, Vol 20, No 2
251
tional exposure to a level resulting in no noticeable effects during the lifetime of the exposed individual and to limit the exposure of the remainder of the population t o as low a level as is deemed possible. Occasional doses somewhat higher than the permissible level are termed “technical overexposures.” The concern of many nurses is what effect does working with radiation have on pregnancy. Government regulation sets the maximum permissible dose (MPD) to the fetus at 0.5 rem. Women of child-bearing age who are occupationally exposed to radiation normally receive less than 2 to 3 rem total per year a t a fairly steady rate and, hence, would probably be aware of pregnancy before reaching the 0.5 rem value. A radiation worker who is pregnant may ask the radiation safety officer or other qualified expert to compute the probable dose to the fetus. Efforts should be made to keep radiation exposure of the fetus as low as possible. Two sources of radiation hazard frequently are present in the operating room-diagnostic x-rays and gamma rays from radium and radium substitutes. Diagnostic x-rays are present briefly during such procedures as hip pinning and foreign body localization. Gamma rays from radium or its substitutes are emitted continuously. However, lead shields absorb the emitted rays so that no significant hazard exists in the OR until the sources are removed from the shield and placed within the patient. A third, less frequent, source of radiation hazard arises from patients containing millicurie quantities of iodine-131 or phosphorus-32 who require surgery subsequent to the administration of the radioactive substances within their bodies.
252
Radiation from an x-ray tube is present only as long as the x-ray tube is energized. As soon as the tube is turned off, the radiation level decreases to the level normally present and not to zero because cosmic radiation and radiation released by naturally radioactive substances within the air, building materials, and human body are always present. This is called background radiation. Although radiation is impossible to hear, see, taste, smell, feel, or otherwise sense, audible and visible indications are given by most modern x-ray units when they are energized. When an x-ray tube is energized, proper caution directs the technician to stand aside from the direction towards which the tube is aimed and to remain six feet or more from the patient until after the exposure is made. Typical exposure levels at this distance are 0.5 millirem per film. Other than the patient, all who remain in the OR during an exposure should be provided with film badges. If the badge is worn properly, radiation striking the worker will expose the film. The film, with a useful life of approximately one month, must be evaluated consistently to determine the radiation dose to the wearer. Potentially hazardous practices may be detected by having the reported film exposures reviewed by a qualified ex-
pert. Hence, the protective nature of a film badge is to provide warning of a dangerous situation before the total dose becomes too high. Studies at many institutions demonstrated the unlikelihood of significant radiation exposure t o OR personnel and so no film badges are provided or necessary. Film badges are not foolproof. If they are worn on the outside of pro-
AORN Journal, August 1974, Vol 20, N o 2
tective lead aprons, they do not measure radiation dose to the body. Those worn inside an apron do not measure dose to the head and neck. It is not possible to specify a place to wear the badge that is proper for all situations. Wearing a badge at waist or chest level inside protective lead aprons is the most commonly recommended location. There are several “do’s and don’ts’’ concerning the proper use of the badge. Although some of these may seem trivial, it is surprising how many people ignore the self-evident. Do 1. Wear the film badge when working. 2. Wear the film badge only during month indicated on the film badge. 3. Change the film badge every month. 4. Keep the film badge dry. 5. Report loss or damage of a badge to the radiation safety office. Don’t 1. Wear the film badge while being exposed to x-rays for personal medical purpose (chest films, dental x-ray examinations, etc) . 2. Lose the film badge. 3. Let the film badge go through the laundry. 4. Leave the film badge in the OR when it is not being used. 5. Write on the film badge. 6. Wear the film badge in such a manner that radiation striking it does not strike you or vice versa. 7. Let others wear your badge.
Two final warnings concerning x-ray hazards should be observed. If strange sounds or burning odors are emitted from an x-ray unit, the diagnostic radiology department should be notified immediately. Also, some old capacitor discharge portable units may remain energized even after being unplugged. Not having adequate protection devices, they are discharged only through electrical leakage or radiation exposure. Medically useful radium sources contain a series of elements in a sealed tube. Any cracks that allow radon, a radioactive gas, to escape will upset the decay equilibrium and cause improper treatment through reduced gamma emission. It is important to avoid crushing or breaking radium sources since radium easily spreads over large areas and is hazardous if ingested because of its alpha emissions. The permissible limit for radium permanently within the body is 0.1 microgram. To lessen the chance of loose radium entering and remaining within the body, modern sources are made with an insoluble radium salt, radium sulfate. Gamma rays released by some of the elements in a radium source penetrate the metal capsules t o deliver radiation dosage. Radium and its substitutes used in the treatment of cancers are measured in milligram quantities and are normally double-sealed within two platinum or platinum-iridium metal tubes. These tubes look like short lengths of finishing nails and may be 1 to 5 mm in diameter and 10 to 60 mm long. They may be shiny or dull, partially or completely silver or gold colored, have one end pointed and an eyelet on the other end, or have both ends flat or rounded. They may be
AORN Journal, August 1974, Vol 20, N o 2
253
Radioactive materials used for permanent implants
radionuclide
approximate activity which will produce 0.25 R/hr 0.002 R/hr at 25 cm at 100 cm
physicaI half-1if e ~
_
~~~
_
~
~
___
gold- 198
2.7
days
70 mCi
9 mCi
iodine-131
8.04 days
70 mCi
9 mCi
iridium-192
74.4 days
30 mCi
4 mCi
radon-222
3.83 days
20 mCi
2.5 mCi
tantalum-182
115 days
20 mCi
2.5 rnCi
phosphorus-32
14.3 days
housed in a larger plastic or metal tube with or without a string or braided metal wire attached. Radium, which remains radioactive for a long time, has a half-life of 1620 years. After one half-life, the radioactivity is only one half the original level. After two half-lives, the radioactivity is only one fourth the original level. Since the process continues indefinitely, sources remain potentially hazardous for thousands of years. Loss of sources should, therefore, be avoided. Radium decays by alpha emission into radon. The metal tubes into which the radium is sealed absorb the alpha rays and prevent the escape of radon. It is necessary to contain the radon until it decays into radium A which decays into radium B which decays into radium C, etc until radium G (uranium lead) finally is produced. The radium is placed as close as possible to, the cancerous tissue so that it will receive the highest dose. The dose to healthy tissue is lower because of the greater distance from the radium. Radium needles are sometimes inserted into the tumor mass or the radium is placed against
254
(not applicable)
the tumor within a body cavity such as the mouth, vagina, uterus, etc, or against an external cancer such as a skin cancer. After the radium has remained in place long enough to deliver a few thousand rem to the cancerous tissue, the sources are removed and prepared for future use in another patient. The radium normally is in place for three to five days. The average dose rate to the cancerous tissue is 60 to 20 rem per hour a t a distance of 0.5 to 2.0 cm from the sources. The proper exercise of caution for the OR nurse when radium or its substitutes are present is to stay several arm’s length away from the sources. This normally will reduce the radiation dose to the nurse to a small fraction of the permissible occupational dose. For brief periods of time when it is necessary to closely attend patients with radium in place, it may be helpful to realize that 15 minutes a t a half-arm’s length is no more hazardous than an hour at one arm’s length from the radium. The protective effect of distance is best illustrated by example. The dose
AORN Journal, August 1974, Vol 20, N o 2
rate is inversely proportionate to the square of the distance from the radiation source. Hence a dose rate of 60 rem per hour at 0.5 cm from a source drops to 1.5 millirem (1millirem = 0.001 rem) per hour at 100 cm from the source due t o distance alone. Absorption of the gamma rays by a patient’s body will make the actual dose rate somewhat lower. The amount of radium normally used in patients ranges from 12 to 120 milligrams. A radium source dropped in the OR should be picked up and replaced in the lead container with a pair of long forceps, being careful not to squeeze the source too hard. If a lead container is not available, an empty emesis basin located several feet from everyone makes a good temporary receptacle. The source should not be touched directly because of the very high dose rates at the surface. Lead aprons and gloves for radium handling usually increases exposure by increasing the time it takes to do the work. They usually are thick enough only to offer protection against x-ray radiation, not against radium radiation.
An important precaution to radiation exposure is to ensure that no radium is lost in the OR. The normally efficient housekeeping practices in operating rooms result in the immediate removal of trash and linen to the laundry, incinerator, or trash location. Checking the linen and trash with a radiation detector prior to removal will prevent accidental hazardous loss and breakage. Radium substitutes, such as iridium-192, cesium-137 and cobalt-60, are less hazardous in some respects than radium. Their emitted radiations are reduced to an equal extent
by distance and to a greater extent by absorption within the patient’s body. The radium substitutes normally remain radioactive for only a few years and are less likely to cause problems if accidentally dumped into a land fill. Greater quantities can be stored because their emitted radiations have less ability to penetrate lead than those of radium. In recent years, the hazard to personnel from the placement or implantation of radium and radium substitutes has been greatly reduced by the development of afterloading techniques. In such techniques, hollow plastic or metal tubes or applicators are inserted into or adjacent to the cancerous tissue. Hollow access tubes from the locations for the radium to the patient’s exterior are inserted with non-radioactive dummy sources. After the source locations are checked by radiography, the dummy sources are removed in the patient’s room rather than the OR and the radioactive sources are inserted. Thus, OR personnel receive no radiation dose from afterloading techniques. Precautions to be observed by recovery room nurses and unit nurses when caring for patients containing radium or radium substitutes follow the same general pattern suggested for OR nurses. The time spent close to the patient must be kept to a minimum, consistent with good nursing care. Lengthy conversations should be postponed until after the removal of the radium. Visitors, especially younger ones, should not be allowed in the room for more than a few minutes during the days the radium is in place. Normally, other patients should not be closer than 200 em.
AORN Journal, August 1974, Vol 20, N o 2
255
Once the radium sources are removed, the hazard is over. There is no residual radiation. However, it is advisable to have the room and all trash and linen checked for lost sources before relaxing precautions. At least one major institution has a restriction that no trash, linen, or food trays, may be removed from a radium patient's room unless first checked for lost radium sources. Rather than placing long-lived sealed radiation sources within the patient for a limited time, as in treatments with radium, some treatments consist of the permanent placement of short-lived sealed radioactive sources or unsealed radioactive solutions. If such patients require surgery before the short-lived material has decayed to a very low level, the OR nurse may receive a dose of radiation. Precautions, in addition to those suggested for radium patients, should be observed. Radioactive fluids or
tissues removed in surgery could contaminate the OR. Bottles used to aspirate fluids should be strong and must be handled carefully to avoid dropping and breaking. Linens and wastes must be set aside from the ordinary trash until checked for contamination. The physician, licensed to place the sources into the patient, will give specific instructions to minimize the likelihood of contamination and to keep the radiation dose to all personnel as low as possible. All the rules, regulations and advice that can be made are worthless if a nurse does not exercise judgment and concern for her own safety. Time, distance, and barriers are the three key safety elements. By planning ahead and being familiar with the required techniques, a nurse can lessen her exposure time. Keeping as reasonable a distance as possible from the source of radiation and good use of protective barriers also will minimize the radiation dose.
Urea ineffecfive in sickle cell crises Earlier publicized claims that urea infusions might be of special value in the treatment of sickle cell crises have not been borne out by the results of a two-year clinical trial recently completed at six participating institutions. The trial, which evaluated and compared three modes of therapy, was supported by contracts from the Sickle Cell Disease Branch of HEW'S National Heart and Lung Institute.
The results of the double blind controlled study indicated that urea offered no advantages over therapeutic measures to correct
256
dehydration or excess blood acidity. Except for a few instances of headache and vein irritation, urea caused no crpparent significant side effects in this trial. Its use, however, required meticulous technique and careful attention to the patient's fluid and blood electrolyte balance, which could be upset as a result of the vigorous diuresis frequently induced by large doses of the agent. None of the regimens proved satisfactory for controlling the painful, frequently disabling crises that pose a continuous threat to some 50,000 Americans, most of them black, who are affected by sickle cell anemia.
AORN Journal, August 1974, Vol 20, N o 2
OR radiation hazards Exposure to radiation in the operating room has been a matter of prime concern to the OR nurse. Constant vigilance for her own safety and strict adherence to all the precautionary rules can minimize problems. Fear of radiation has grown with the realization of its hazards. At the time of the discovery of x-rays by Wilhelm Conrad Roentgen in 1895 and of the radioactivity of pitchblend by Antoine Henri Becquerel in 1896, few if any persons had reasons
John L Day, PhD, a member of the Ionizing Radiation Control Committee at Hahnemann Medical College and Hospital, Philadelphia, is assistant professor in the Department of Radiation Therapy and Nuclear Medicine. He is a graduate o f the University of Michigan. David A Lightfoot, M A , is a certified radiological physicist and an assistant professor in the Department of Radiation Therapy and Medicine at Hahnemann. He is a graduate of Temple University, Philadelphia. This paper was supported b y the National Cancer Institute, the Alperin Foundation, and Friends of the Radiation Therapy Center.
to fear radiation. Perhaps the most widespread concern or fear then was whether peeping toms could use x-rays to see the naked flesh modestly hidden beneath layers of fashionable garments. As knowledge of the characteristics of x-rays and radioactivity expanded, this foolish concern was replaced by a wellfounded respect for the real hazard of radiation-its ability to modify molecules within body cells. The alteration of molecular structures may cause cell dysfunction, an alteration, delay, or permanent halt in cell replication, or cellular lysis. The observable effect of this depends on the nature of the cells affected and the nature and extent of the radiation exposure. For example, depending on the amount, a dose of radiation to the abdomen may cause death through intestinal bleeding or may cause no symptoms at all. This is because normally cells lining the intestine are being replaced constantly by newly formed cells. If a large dose of radiation temporarily halts new cell formation, the cells normally leaving the intestinal lining will not be replaced. Within a few days, as cells continue to leave the intestinal sur-
AORN Jozlmal, August 1974, Vol 20, No 2
249
face, too few cells will be left to spread over the walls of the intestine and bleeding will occur through seepage into the intestine. Infection and death may ensue. With a lower dose of radiation, fewer cell-forming centers will be affected and the loss of blood will not be enough to cause death. Recovery may be complete within a few days after new cell-formation resumes. In this case the radiation effect would not be much different than ordinary diarrhea. Small doses of radiation effecting only a few cell-formation centers may produce no noticeable symptoms a t all. In explaining radiation effects, scientists have relied on such descriptive terms as direct and indirect effects, latency, dose-effect relationships, threshold effects, equivalent dose, somatic and genetic effects, tolerance, and recovery and repair. These concepts are briefly defined as follows: Direct and indirect effects. The immediate damage within cells caused directly by the radiation or indirectly by the altered chemical molecules within the cells.
Latency. The damage remains hidden until some later time. Experience with radiation effects indicates radiation damage may remain latent or hidden for several years after exposure. Dose-effect relationships. The effect of radiation exposure is related to the amount and length of time of exposure. Too much exposure t o radiation may cause serious damage. Below certain levels of radiation exposure, there may be no noticeable damage even if the exposure is repeated for a working lifetime.
250
Threshold effects. Some types of radiation damage may never occur unless exposure exceeds a critical level called the dose threshold. If the critical level is extremely low (practically zero), the effect is referred to as a non-threshold effect. Once the dose-threshold is exceeded, the probability of damage increases as the dose is increased. Equivalent dose. This term applies to the quantity which expresses all radiations on a common scale for the purpose of calculating their biological effects. The unit of the equivalent dose is the rem. Equivalent doses cause equal damage regardless of the type of radiation responsible. Government regulations concerning permissible doses of radiation are based on units of equivalent dose. Somatic and genetic effects.Radiation damage observable in the exposed individual is a somatic effect. Radiation damage passed on to future generations is a genetic effect. The possibility of defective future generations is unlikely unless a major portion of the population receives a significant exposure. The probability of transmitting radiation damage to offspring also is lower than commonly feared since radiation damage to all cells is unlikely. An altered gene has only a 50% chance of being passed on if the ovum or sperm comes from the cell with the altered gene and may not even be observable in the offspring. There are several causes of genetic mutation other than radiation. Even with no radiation exposure, 4% to 5% of all births show congenital defects. It has been estimated that a radiation dose of 50-80 rem will increase the rate of genetic mutations to double its natural rate.
AORN Journal, August 1974, Vol 20, N o 2
Tolerance. Radiation tolerance, a term most appropriately used by radiation therapists, is somewhat analogous to the critical level in threshold effects. However, i t normally means a dosage level above which radiation effects become medically serious in a significant percentage of patients rather than a level below which no radiation effect is observable. Generally, highly differentiated cells which normally do not divide have a higher tolerance to radiation than rapidly dividing lessdifferentiated cells.
Recovery and repair. There are many indications that cells are able to recover from radiation damage. For example, cells which cease dividing because of radiation exposure may renew dividing in a few days if exposure is not too high. Repair occurs only if those cells able to escape or recover from radiation damage form new cells. These new cells, in turn, replace damaged cells. Are the risks caused by radiation balanced by the benefits? It is a difficult question to answer. Defining the risks and benefits is equally as difficult. For the critically ill patient, the risk of imminent death without x-ray examination may far exceed any imaginable risk created by radiation. The prevailing philosophy of the risk to the occupationally exposed worker is given in National Council on Radiation Protection and Measurements (NCRP) Report No 39: “The only statement that can be made a t the present time about the lifetime exposure of persons to penetrating radiation a t a permissible level considerably higher than the background radiation level, but within the range of radiological experience, is that appreciable injury
manifestable in the lifetime of the individual is extremely unlikely. It is, however, necessary to assume that any practical limit of exposure that may be set up today will involve some risk of possible harm. The problem is to make this risk so small that i t is readily acceptable to the average individual: that is, to make the risk essentially the same as is present in ordinary occupations not involving exposure to radiation.” Some ask, “Why not make the permissible dose zero?” Zero dose is impossible to achieve since man always has been subject to radiation from natural sources such as cosmic rays and naturally occurring radioactive materials. The medical use of x-rays and radioactive materials produced by nuclear reactors and nuclear bombs causes man to receive additional radiation dose. Arguments about the hazards of man-made sources of radiation sometimes ignore the hazards of alternatives. Until such time as suitable alternatives of lesser risk are available, eliminating the medical use of radiation would be more harmful than beneficial. However, some alternatives are better, such as, tuberculosis skin tests rather than chest x-rays. Generally, the government established limits of permissible radiation dose as 5 rem per year for occupationally exposed workers 18 years of age and older, and 0.5 rem per year for everyone else. The limits are over and above any radiation dosage received for medical reasons. A dose of 0.17 rem per year per person frequently is referred to as the average dose permissible from nuclear reactors and other sources. The intent of the complex government regulations is to limit occupa-
AORN Journal, August 1974, Vol 20, No 2
251
tional exposure to a level resulting in no noticeable effects during the lifetime of the exposed individual and to limit the exposure of the remainder of the population t o as low a level as is deemed possible. Occasional doses somewhat higher than the permissible level are termed “technical overexposures.” The concern of many nurses is what effect does working with radiation have on pregnancy. Government regulation sets the maximum permissible dose (MPD) to the fetus at 0.5 rem. Women of child-bearing age who are occupationally exposed to radiation normally receive less than 2 to 3 rem total per year a t a fairly steady rate and, hence, would probably be aware of pregnancy before reaching the 0.5 rem value. A radiation worker who is pregnant may ask the radiation safety officer or other qualified expert to compute the probable dose to the fetus. Efforts should be made to keep radiation exposure of the fetus as low as possible. Two sources of radiation hazard frequently are present in the operating room-diagnostic x-rays and gamma rays from radium and radium substitutes. Diagnostic x-rays are present briefly during such procedures as hip pinning and foreign body localization. Gamma rays from radium or its substitutes are emitted continuously. However, lead shields absorb the emitted rays so that no significant hazard exists in the OR until the sources are removed from the shield and placed within the patient. A third, less frequent, source of radiation hazard arises from patients containing millicurie quantities of iodine-131 or phosphorus-32 who require surgery subsequent to the administration of the radioactive substances within their bodies.
252
Radiation from an x-ray tube is present only as long as the x-ray tube is energized. As soon as the tube is turned off, the radiation level decreases to the level normally present and not to zero because cosmic radiation and radiation released by naturally radioactive substances within the air, building materials, and human body are always present. This is called background radiation. Although radiation is impossible to hear, see, taste, smell, feel, or otherwise sense, audible and visible indications are given by most modern x-ray units when they are energized. When an x-ray tube is energized, proper caution directs the technician to stand aside from the direction towards which the tube is aimed and to remain six feet or more from the patient until after the exposure is made. Typical exposure levels at this distance are 0.5 millirem per film. Other than the patient, all who remain in the OR during an exposure should be provided with film badges. If the badge is worn properly, radiation striking the worker will expose the film. The film, with a useful life of approximately one month, must be evaluated consistently to determine the radiation dose to the wearer. Potentially hazardous practices may be detected by having the reported film exposures reviewed by a qualified ex-
pert. Hence, the protective nature of a film badge is to provide warning of a dangerous situation before the total dose becomes too high. Studies at many institutions demonstrated the unlikelihood of significant radiation exposure t o OR personnel and so no film badges are provided or necessary. Film badges are not foolproof. If they are worn on the outside of pro-
AORN Journal, August 1974, Vol 20, N o 2
tective lead aprons, they do not measure radiation dose to the body. Those worn inside an apron do not measure dose to the head and neck. It is not possible to specify a place to wear the badge that is proper for all situations. Wearing a badge at waist or chest level inside protective lead aprons is the most commonly recommended location. There are several “do’s and don’ts’’ concerning the proper use of the badge. Although some of these may seem trivial, it is surprising how many people ignore the self-evident. Do 1. Wear the film badge when working. 2. Wear the film badge only during month indicated on the film badge. 3. Change the film badge every month. 4. Keep the film badge dry. 5. Report loss or damage of a badge to the radiation safety office. Don’t 1. Wear the film badge while being exposed to x-rays for personal medical purpose (chest films, dental x-ray examinations, etc) . 2. Lose the film badge. 3. Let the film badge go through the laundry. 4. Leave the film badge in the OR when it is not being used. 5. Write on the film badge. 6. Wear the film badge in such a manner that radiation striking it does not strike you or vice versa. 7. Let others wear your badge.
Two final warnings concerning x-ray hazards should be observed. If strange sounds or burning odors are emitted from an x-ray unit, the diagnostic radiology department should be notified immediately. Also, some old capacitor discharge portable units may remain energized even after being unplugged. Not having adequate protection devices, they are discharged only through electrical leakage or radiation exposure. Medically useful radium sources contain a series of elements in a sealed tube. Any cracks that allow radon, a radioactive gas, to escape will upset the decay equilibrium and cause improper treatment through reduced gamma emission. It is important to avoid crushing or breaking radium sources since radium easily spreads over large areas and is hazardous if ingested because of its alpha emissions. The permissible limit for radium permanently within the body is 0.1 microgram. To lessen the chance of loose radium entering and remaining within the body, modern sources are made with an insoluble radium salt, radium sulfate. Gamma rays released by some of the elements in a radium source penetrate the metal capsules t o deliver radiation dosage. Radium and its substitutes used in the treatment of cancers are measured in milligram quantities and are normally double-sealed within two platinum or platinum-iridium metal tubes. These tubes look like short lengths of finishing nails and may be 1 to 5 mm in diameter and 10 to 60 mm long. They may be shiny or dull, partially or completely silver or gold colored, have one end pointed and an eyelet on the other end, or have both ends flat or rounded. They may be
AORN Journal, August 1974, Vol 20, N o 2
253
Radioactive materials used for permanent implants
radionuclide
approximate activity which will produce 0.25 R/hr 0.002 R/hr at 25 cm at 100 cm
physicaI half-1if e ~
_
~~~
_
~
~
___
gold- 198
2.7
days
70 mCi
9 mCi
iodine-131
8.04 days
70 mCi
9 mCi
iridium-192
74.4 days
30 mCi
4 mCi
radon-222
3.83 days
20 mCi
2.5 mCi
tantalum-182
115 days
20 mCi
2.5 rnCi
phosphorus-32
14.3 days
housed in a larger plastic or metal tube with or without a string or braided metal wire attached. Radium, which remains radioactive for a long time, has a half-life of 1620 years. After one half-life, the radioactivity is only one half the original level. After two half-lives, the radioactivity is only one fourth the original level. Since the process continues indefinitely, sources remain potentially hazardous for thousands of years. Loss of sources should, therefore, be avoided. Radium decays by alpha emission into radon. The metal tubes into which the radium is sealed absorb the alpha rays and prevent the escape of radon. It is necessary to contain the radon until it decays into radium A which decays into radium B which decays into radium C, etc until radium G (uranium lead) finally is produced. The radium is placed as close as possible to, the cancerous tissue so that it will receive the highest dose. The dose to healthy tissue is lower because of the greater distance from the radium. Radium needles are sometimes inserted into the tumor mass or the radium is placed against
254
(not applicable)
the tumor within a body cavity such as the mouth, vagina, uterus, etc, or against an external cancer such as a skin cancer. After the radium has remained in place long enough to deliver a few thousand rem to the cancerous tissue, the sources are removed and prepared for future use in another patient. The radium normally is in place for three to five days. The average dose rate to the cancerous tissue is 60 to 20 rem per hour a t a distance of 0.5 to 2.0 cm from the sources. The proper exercise of caution for the OR nurse when radium or its substitutes are present is to stay several arm’s length away from the sources. This normally will reduce the radiation dose to the nurse to a small fraction of the permissible occupational dose. For brief periods of time when it is necessary to closely attend patients with radium in place, it may be helpful to realize that 15 minutes a t a half-arm’s length is no more hazardous than an hour at one arm’s length from the radium. The protective effect of distance is best illustrated by example. The dose
AORN Journal, August 1974, Vol 20, N o 2
rate is inversely proportionate to the square of the distance from the radiation source. Hence a dose rate of 60 rem per hour at 0.5 cm from a source drops to 1.5 millirem (1millirem = 0.001 rem) per hour at 100 cm from the source due t o distance alone. Absorption of the gamma rays by a patient’s body will make the actual dose rate somewhat lower. The amount of radium normally used in patients ranges from 12 to 120 milligrams. A radium source dropped in the OR should be picked up and replaced in the lead container with a pair of long forceps, being careful not to squeeze the source too hard. If a lead container is not available, an empty emesis basin located several feet from everyone makes a good temporary receptacle. The source should not be touched directly because of the very high dose rates at the surface. Lead aprons and gloves for radium handling usually increases exposure by increasing the time it takes to do the work. They usually are thick enough only to offer protection against x-ray radiation, not against radium radiation.
An important precaution to radiation exposure is to ensure that no radium is lost in the OR. The normally efficient housekeeping practices in operating rooms result in the immediate removal of trash and linen to the laundry, incinerator, or trash location. Checking the linen and trash with a radiation detector prior to removal will prevent accidental hazardous loss and breakage. Radium substitutes, such as iridium-192, cesium-137 and cobalt-60, are less hazardous in some respects than radium. Their emitted radiations are reduced to an equal extent
by distance and to a greater extent by absorption within the patient’s body. The radium substitutes normally remain radioactive for only a few years and are less likely to cause problems if accidentally dumped into a land fill. Greater quantities can be stored because their emitted radiations have less ability to penetrate lead than those of radium. In recent years, the hazard to personnel from the placement or implantation of radium and radium substitutes has been greatly reduced by the development of afterloading techniques. In such techniques, hollow plastic or metal tubes or applicators are inserted into or adjacent to the cancerous tissue. Hollow access tubes from the locations for the radium to the patient’s exterior are inserted with non-radioactive dummy sources. After the source locations are checked by radiography, the dummy sources are removed in the patient’s room rather than the OR and the radioactive sources are inserted. Thus, OR personnel receive no radiation dose from afterloading techniques. Precautions to be observed by recovery room nurses and unit nurses when caring for patients containing radium or radium substitutes follow the same general pattern suggested for OR nurses. The time spent close to the patient must be kept to a minimum, consistent with good nursing care. Lengthy conversations should be postponed until after the removal of the radium. Visitors, especially younger ones, should not be allowed in the room for more than a few minutes during the days the radium is in place. Normally, other patients should not be closer than 200 em.
AORN Journal, August 1974, Vol 20, N o 2
255
Once the radium sources are removed, the hazard is over. There is no residual radiation. However, it is advisable to have the room and all trash and linen checked for lost sources before relaxing precautions. At least one major institution has a restriction that no trash, linen, or food trays, may be removed from a radium patient's room unless first checked for lost radium sources. Rather than placing long-lived sealed radiation sources within the patient for a limited time, as in treatments with radium, some treatments consist of the permanent placement of short-lived sealed radioactive sources or unsealed radioactive solutions. If such patients require surgery before the short-lived material has decayed to a very low level, the OR nurse may receive a dose of radiation. Precautions, in addition to those suggested for radium patients, should be observed. Radioactive fluids or
tissues removed in surgery could contaminate the OR. Bottles used to aspirate fluids should be strong and must be handled carefully to avoid dropping and breaking. Linens and wastes must be set aside from the ordinary trash until checked for contamination. The physician, licensed to place the sources into the patient, will give specific instructions to minimize the likelihood of contamination and to keep the radiation dose to all personnel as low as possible. All the rules, regulations and advice that can be made are worthless if a nurse does not exercise judgment and concern for her own safety. Time, distance, and barriers are the three key safety elements. By planning ahead and being familiar with the required techniques, a nurse can lessen her exposure time. Keeping as reasonable a distance as possible from the source of radiation and good use of protective barriers also will minimize the radiation dose.
Urea ineffecfive in sickle cell crises Earlier publicized claims that urea infusions might be of special value in the treatment of sickle cell crises have not been borne out by the results of a two-year clinical trial recently completed at six participating institutions. The trial, which evaluated and compared three modes of therapy, was supported by contracts from the Sickle Cell Disease Branch of HEW'S National Heart and Lung Institute.
The results of the double blind controlled study indicated that urea offered no advantages over therapeutic measures to correct
256
dehydration or excess blood acidity. Except for a few instances of headache and vein irritation, urea caused no crpparent significant side effects in this trial. Its use, however, required meticulous technique and careful attention to the patient's fluid and blood electrolyte balance, which could be upset as a result of the vigorous diuresis frequently induced by large doses of the agent. None of the regimens proved satisfactory for controlling the painful, frequently disabling crises that pose a continuous threat to some 50,000 Americans, most of them black, who are affected by sickle cell anemia.
AORN Journal, August 1974, Vol 20, N o 2