Clotting a risk for all travellers

By KATHERINE HOBY

Deep vein thrombosis - better known as economy class syndrome - has captured headlines around the world.

But debate continues to rage between medical experts, airlines, and victims of blood clots over what causes the condition and what can be done to prevent it.

Auckland vascular surgeon Dr Peter Charlesworth has a special interest in diseases of the veins. He says a lot of the information about clotting is logical but not proven.

"It's a mixture of common sense and science from those in the medical fraternity."

Here, Your Health attempts to answer queries about blood clots.

What is "economy class syndrome"?


Deep vein thrombosis (DVT) is the name given to a type of blood clot - known medically as a thrombus - that commonly forms in the deep veins of the lower leg or pelvis. It has been linked to the low mobility of passengers on long-haul flights and other forms of protracted travel in cramped spaces such as on cars, buses and trains.

It was dubbed "traveller's thrombosis" or "travel-related thrombosis" by British surgeon Dr John Scurr in March this year, who felt it was a better name for the condition.

"Studies have shown it is a common travel problem," he said.

It is well known that it is not only economy flying, and indeed not only flying, that causes the potentially fatal blood clots.

But airlines such as Air New Zealand and Cathay Pacific have taken DVT seriously enough to have information available to passengers. Air New Zealand already stamps tickets, timetables, and itineraries with a notice advising passengers what they can do to reduce the risk.

Why does it occur?


DVT occurs when the flow of blood is restricted in a vein, and a clot forms. It can be caused by poor circulation because of problems such as heart disease, a recent heart attack or stroke, varicose veins, or from prolonged inactivity. Normally, movement of the calf muscle helps to pump blood from the legs to the heart. But if the leg remains still or if circulation is restricted, blood is more likely to form a clot in one of the leg's deep veins.

What can happen if it is not noticed?


Small clots localised to the calf veins might cause temporary pain and swelling of the leg, but no other serious complication.

The most common, serious complication of DVT is a pulmonary embolism, where a blood clot breaks free from a vein wall, travels to the lung and blocks an artery. The clots can break off and travel to the lungs, brain or heart. DVT can also cause a miscarriage or stillbirth if a clot breaks free and lodges in an artery in the placenta, reducing the oxygen supply to the foetus.

What are the risk factors?


Dr Charlesworth says these include obesity, age, pregnancy, immobility, heart failure, the use of oestrogen-containing hormones and a previous history of DVT.

What precautions can be taken?


Advice on this varies. Dr Charlesworth advocates three measures: static leg exercises and walking around where possible, minimising alcohol consumption but keeping up intake of other fluids, and wearing properly fitted compression stockings below the knee.

Others might include avoiding sedative medications, and not smoking. The use of aspirin before flight is controversial.

What are its symptoms? Watch for:


* Tenderness and warmth in one leg.

* Mild fever.

* Pitting oedema (extra fluid in the legs - when the area is pressed a dent is left in the leg).

* One leg swollen to more than 2-3cm compared with the other side.

* Rapid heart beat.

* Sudden coughing.

* Joint pain.

Auckland's Green Lane Hospital and Otago University's Wellington School of Medicine and Health Sciences are researching DVT. About 1000 volunteers will have blood tests before and after long-haul flights.

An Australian law firm has had inquiries from more than 100 New Zealand residents asking about taking action over travel-related clotting. The names have been passed to Wellington firm Johnston Lawrence, which has filed High Court claims against several airlines.