The LONFLIT4--Concorde Deep Venous Thrombosis and Edema Study: prevention with travel stockings

BACKGROUND: The LONFLIT1+2 studies have established that in high risk subjects after long flights (> 10 hours) the incidence of deep venous thrombosis (DVT) is between 4% and 6%. The LONFLIT4 study was designed to evaluate the control of edema and DVT in low-medium risk subjects. The aim of this study was to evaluate edema and its control with specific stockings (ankle pressure between 20 and 30 mm Hg) in long-haul flights. The first part of the study included flights lasting 7-8 hours and the second part included flights lasting 11-12 hours. Ultrasound scans were used to assess thrombosis before and after the flights and a composite edema score was used to evaluate edema and swelling. A group of patients with microangiopathy associated to edema (diabetes, venous hypertension, anti-hypertensive treatment) were also included to evaluate the preventive effects of stockings during flight. Part I: DVT evaluation: Of the 74 subjects in the stocking group and 76 in the control group (150), 144 completed the study. Dropouts were due to low compliance or traveling and connection problems. Age and gender distribution were comparable in the 3 groups as was risk factor distribution. In this part of the study there were no DVTs. Edema Evaluation: The level of edema at inclusion was comparable in the two groups of subjects. After the flight there was an average score of 6.9 (1) in the control group. In the stocking group, the score was on average 2.3 (1), three times lower than in the control group (p < 0.05). Part II: DVT evaluation: Of the 66 included subjects in the stocking group and 68 in the control group (134), 132 completed the study. Dropouts were due to low compliance or connection problems. Age and gender distribution were comparable in the two groups. In the stocking group no DVT was observed. In the control group, 2 subjects had a popliteal DVT and 2 subjects had superficial venous thrombosis (SVT); in total 4 subjects (6%) in the control group had a thrombotic event; the incidence of DVT was 3%. The difference (p < 0.02) is significant. EDEMA EVALUATION: The composite edema score at inclusion was comparable in the two groups. After the flight there was a score of 7.94 (2) in the control group, while in the treatment group the score was 3.3 (1.2). MICROANGIOPATHY STUDY: In all these subjects, the level of edema was very high in the control group and significantly lower in the compression stocking group. Stockings are effective in controlling edema during flights even in subjects with microangiopathy and edema. Compression was well tolerated in normal subjects and in patients. CONCLUSION: The Kendall Travel Socks (Tyco Healthcare, Mansfield, MA, USA) which provide 20-30 mm Hg pressure at the ankle, are effective in controlling edema and reducing the incidence of DVT in both low-medium-risk subjects and in patients with microangiopathy and edema in long-haul flights (7-11 hours).