Patients with a haemoglobin of greater than 8 g/dl may travel without problems assuming there is no coexisting condition such as cardiovascular or respiratory disease. If the haemoglobin is less than 7.5 g/dl, special assessment should be made and the use of supplemental oxygen should be considered.
Individuals with chronic renal insufficiency or other medical condition predisposing to anaemia, which is chronic in nature, will usually tolerate a lower haemoglobin level than if the anaemia is of acute onset. Sickle cell trait does not present a particular problem at normal cruising altitude. However, patients with sickle cell anaemia should travel with supplemental oxygen and should defer travel for approximately 10 days following a sickling crisis.
Deep Venous Thrombosis (DVT)
Deep venous thrombosis is not intrinsically dangerous but the complications of pulmonary embolism can be life threatening. It has been shown that DVT can occur in many other forms of travel, as described by Homans in 1954. The World Health Organisation Research into Global Hazards of Travel (Wright) Project recently reported and the key determinant for deep venous thrombosis is immobilisation and the risk of thrombosis is increased by travel of greater than 4 hours. Therefore “travellers’ thrombosis” is the most appropriate term to use, rather than “economy class syndrome”. There is no evidence that the cabin environment activates the coagulation system of normal individuals. The absolute risk, as shown in the Wright Study, was one in 4656 flights of more than 4 hours duration.
The risk factors for thrombosis are well known and are listed below:
- Thrombophilia enhancing clotting activity
- Recent major surgery
- Trauma or surgery of the lower limbs
- Family history of deep vein thrombosis
- Age over 40 years
- The oral contraceptive pill
Prophylactic measures should be undertaken according to the degree of risk. Simple, effective measures are to move about the aircraft cabin and to carry out the lower limb exercises shown in airline videos and in-flight magazines.
Any specialised prophylaxis should be targeted at those at the highest risk and include:
- properly fitted anti-embolism stockings giving graduated compression to the limb,
- subcutaneous low molecular weight heparin, which is highly effective and has a low risk of bleeding and in extremely high risk cases oral anticoagulation.
It is important to emphasise that the risk of side effects from the use of aspirin outweigh any potential anti-thrombotic effect and its use is not recommended.