acute radiation syndrome
Radiation exposure occurs when all or part of the body is irradiated. Three key factors affect exposure:
duration, distance and shielding. If the exposure time is halved, then the dose of radiation is halved. The inverse square law applies to distance: doubling the distance between the source and the body reduces the dose by a factor of four; trebling the distance between the source and the body reduces the dose by a factor of nine; and so on. In the same way that a patient who has had a radiograph presents no risk to others, radiation safety precautions are not needed for patients who have been exposed to radiation but are not contaminated.
Measurement of radioactivity and radiation → Box 10.5 on p. 146.
Types of ionising radiation → Box 10.4 on p. 146.
Many radiation accidents cause partial body injury:
early erythema followed by bullae and, if severe,
ulceration and necrosis (often of the hands). This may not necessarily progress to acute radiation syn-drome (ARS). ARS follows a large, usually external exposure of all or most of the body to penetrating radiation (gamma rays, high-energy X-rays or neu-trons) in a short time (seconds, minutes or hours).
Symptoms of ARS occur in four phases: prodromal phase → latent period → illness → recovery or death.
As the radiation dose increases, the prodromal and latent periods shorten and the severity of illness and the risk of mortality increase. Major trauma and radi-ation exposure interact synergistically on mortality.
Box 10.6 Dose-related features of acute radiation syndrome
<1 Sv: usually asymptomatic
• Mild symptoms in up to 10% of people of episodic nausea and vomiting for 48 h
• Slightly depressed white blood cell (WBC) count at 2–4 weeks post-exposure
• No fetal effects if the effective dose <100 mSv (100 000 mcSv) but counselling needed if pregnant and effective dose >100 mSv (100 000 mcSv)
1–8 Sv: haematopoietic syndrome
• Anorexia, nausea, vomiting and fatigue between 1 and 4 hours after exposure (the timing and severity are dose related)
• Latent period of between 2 days and 4 weeks and then
• Bone marrow depression (leukopenia and infection; low platelets and bleeding)
• Serial lymphocyte counts in the first 48 h predict the severity
• Hair loss after 2 or 3 weeks after a dose of
>3 or 4 Sv
• Lethal dose (LD) 50/60 is around 4.5 Sv without treatment
>6 Sv: gastrointestinal syndrome
• Early nausea, vomiting, diarrhoea, anorexia and fatigue
• Latent period of up to 1 week and then
• Severe gastrointestinal (GI) symptoms (fever, abdominal pain, watery diarrhoea, GI haemorrhage, electrolyte imbalance and dehydration)
• Bone marrow depression (leukopenia and infection; low platelets and bleeding)
• LD 100 is about 10 Sv; death usually occurs within 2 weeks
>20 Sv: central nervous system/cardiovascular system syndrome
• Burning sensation on the skin
• Almost immediate projectile vomiting and explosive bloody diarrhoea
• Headache, collapse, agitation, confusion and loss of consciousness
• May be a lucid interval (hours) and then
• Convulsions, coma, hypotension, shock and death within 2–3 days
If there are no symptoms (such as nausea or vomiting) in the first 6 h after a suspected exposure, then serious acute radiation sickness is unlikely.
Features suggestive of significant penetrating irra-diation that may progress to full rairra-diation sickness include the following:
• A history of loss of consciousness (this suggests a high dose of radiation with a bad prognosis)
• Transient erythema after 24 h
• Early nausea, diarrhoea and vomiting (especially within 1 h of exposure)
• An early and dramatic fall in the white cell count.
Dose-related symptoms and signs of ARS → Box 10.6.
Tx
Assume that all patients are contaminated until you know that they are not!
Initial symptoms of ARS are non-specific and rarely immediately life threatening; treatment of other inju-ries therefore takes priority.
• Commence standard resuscitation measures.
• Do not handle unfamiliar objects or embedded fragments directly.
• Relieve pain with morphine; give cyclizine or odansetron for nausea and vomiting.
• Obtain and record as much information as possible about the type and extent of the exposure in order to help assessment of the dose of radiation received.
ment of internal contamination. The development of radiation sickness is a delayed phenomenon and at-risk patients should be referred to the nearest oncol-ogy or haematoloncol-ogy unit after discussion with the local radiation protection adviser. A history of irradia-tion should not delay surgery. As a result of the immu-nosuppressive effect of the radiation, if the dose is more than 1 Sv, all surgery should be carried out as soon as possible and certainly within 36–48 h of the incident. If this is not possible, then recovery of the bone marrow must be awaited.
Comparative doses of radiation → Figure 10.3.
• Take routine blood samples including a baseline full blood count. Perform serial absolute lymphocyte counts every 3 or 4 h for the first 12 h after an acute exposure and then 6-hourly for the next 48 h.
• Arrange HLA typing and chromosome analysis (venous blood and nasal swabs).
• Test for internal contamination by faecal sampling or 24-hour urine collection.
Early expert advice (e.g. from departments of medical physics or nuclear medicine, the Health Protection Agency or the Ministry of Defence) is essential for formal radiation dose assessment and the manage-Figure 10.3 Comparative doses of radiation.
• Chest X-ray (PA) = 0.02 millisievert
• Limb or joint X-rays (AP and lateral) = 0.12 millisievert
• Cervical spine X-rays (3 views) = 0.27 millisievert
• Abdominal or pelvic X-ray (AP) = 0.7 millisievert
• Lumbar spine X-rays (AP and lateral) = 1.0 millisievert
• CT scan of the brain = 2.0 millisievert
• CT scan of the abdomen or thorax = 8 to 10 millisievert
• The average annual background radiation exposure in the UK = 2.2 millisievert
• The annual effective dose limit for a UK citizen = 1.0 millisievert
• Acute radiation sickness (whole body single dose) = 1,000 millisievert and above
• The LD 50/60 dose (50% mortality within 60 days if not treated) = approximately 4,500 millisievert
• The LD 100 dose (100% mortality) = around 10,000 millisievert
• The annual effective dose limit for a UK radiation worker = 20 millisievert
11
This chapter covers the essential theoretical and practical aspects of cardiac arrest and dysrhythmia management. However, it does not claim to equip the reader with all the skills necessary for leading a resuscitation team. To achieve such competence, it is essential to have participated in an Advanced Life Support or similar course.
The protocols and algorithms used in this chapter are taken from the guidelines published in 2010 by the Resuscitation Council (UK). As such, they are consistent with the European Resuscitation Council (ERC) Guidelines for Resuscitation 2010 and are based on the current recommendations of the International Liaison Committee on Resuscitation (ILCOR).