The death toll from the earthquake that hit Syria and Turkey in February has surpassed 50,000.
Some fatalities have been from what doctors call "crush syndrome", which occurs when parts of the body have been compressed and starved of blood for too long. It causes significant tissue damage.
How does crush syndrome happen?
Patients may seem normal before their condition starts to deteriorate rapidly as extrication lifts the pressure off muscles and restores blood flow to the compressed organ or tissue, known as reperfusion.
This can lead to rhabdomyolysis, a medical condition which results when the damaged muscle tissue releases proteins and other substances into the blood in larger-than-normal quantities. Often called simply rhabdo, it can have other causes, including heat exposure and physical exertion.
This can sometimes cause kidney failure.
The condition was first described in 1941 and involved a patient who initially appeared to be in a good condition, but later suffered fatal kidney failure.
When blood flow is restored to the affected parts, many of the substances released are essential for cells to function but prove harmful when concentrations are very high.
For example, when there are large concentrations of the blood protein myoglobin, some may precipitate out of the blood and form a solid, potentially leading to blockages in the kidneys.
Other related chemicals released into the blood may be toxic to the kidneys.
Among other chemicals whose concentration may spike, potassium may affect the heart rhythm and patients are at risk of going into shock. This elevated concentration of potassium in the blood is called hyperkalaemia.
A variety of symptoms result from crush syndrome, including muscle aches and pains, irregular heartbeat, kidney failure, agitation, delirium, nausea and vomiting.
How is crush syndrome treated?
A key measure is giving patients large amounts of fluids intravenously as quickly as possible, including while they are being extricated — a process that may take several hours — before reperfusion begins.
Patients are typically transferred to hospital for further treatment.
In some cases, more than 25 litres of saline fluid have been given to a crush syndrome patient within a day, reported Prof Sujatha Rajagopalan, from the Armed Forces Medical College in Puna, India, in the Medical Journal Armed Forces India.
A variety of additional substances are also given intravenously. A glucose drip may limit the increase in potassium concentration in the blood.
As a result of the stress put on the kidneys, dialysis is often carried out and may be needed three times a day for up to about 15 days.
After the 1988 earthquake in Armenia, which killed tens of thousands of people, nearly one quarter of patients required dialysis, Prof Rajagopalan reported.
The compression that tissues have experienced can cause local harm as well as body-wide effects, so dead muscle tissue may have to be removed. Surgery may also be needed to relieve swelling.
How common is crush syndrome?
Up to 80 per cent of such patients die because of head injuries or asphyxiation, according to Prof Rajagopalan.
Of the remaining 20 per cent, about half will have "an uneventful recovery", while the other half go into crush syndrome.
Severe head and chest compression is often fatal in itself, so crush syndrome more often develops when other areas of the body have been compressed.
More than 17,000 people died after the 1999 earthquake in Izmit, in Turkey’s Eastern Marmara region, with some deaths the result of crush syndrome.
A study published several years later offered a snapshot of the issues related to crush syndrome an earthquake causes.
Writing in 2003 in the Emergency Medicine Journal, which is linked to the British Medical Journal, researchers went through the records of 18 of 783 patients who were taken to a university hospital.
Of the 18, six suffered hyperkalaemia and four underwent emergency dialysis. On arriving in the intensive care unit, one patient, the researchers wrote, died because of hyperkalaemia. Ventilators were needed by 12 patients.
In total, 13 suffered kidney failure and, as a result, underwent dialysis or a similar procedure called haemoperfusion. Two patients died from sepsis and five because of multiple organ failure.
"Crush syndrome is a life-threatening event," the researchers wrote.
"The authors believe that early transportation and immediate intensive care therapy would have improved the survival rate."