Thigh-length compression stockings and DVT after stroke

How can the pressure in anti-embolism stockings be maintained during use? Laboratory evaluation of simulated 'wear' and different reconditioning protocols

BACKGROUND

Deep vein thrombosis is a major global health issue, responsible for thousands of deaths each year. While thrombi can form under a variety of circumstances, lack of mobility significantly increases risk and therefore non-ambulant patients are frequently fitted with anti-embolism stockings on admission to hospital, to aid blood flow, prevent pooling and thus clotting. Anti-embolism stockings are the most widely used non-invasive medical device on the market and are believed to reduce the risk of deep vein thrombosis by 40%. Despite their widespread use in hospitals world-wide, there is remarkably little research addressing their use or reconditioning and a wide variety of different reconditioning protocols are used in hospitals.

OBJECTIVE

The objective of this study was to establish the impact of different wear and reconditioning protocols on the pressure delivering ability of anti-embolism stockings.

DESIGN/METHODS

A laboratory investigation was undertaken to evaluate the pressure delivering ability of 2 major global brands of anti-embolism stockings over 5-8days of simulated wear (extension on static cylinders) and 4 different reconditioning protocols. 1 set of samples was continuously 'worn' for 8days without reconditioning, 1 set of samples was 'worn' for 5days with a day of relaxation between each day of 'wear', 1 set was 'hand washed' and 1 set was machine washed and then allowed to relax between each day of 'wear'. The pressure was measured at the beginning and end of each period of 'wear'.

SETTING

This study was undertaken in a conditioned textile testing laboratory that complies with BS EN ISO 139:2005+A1:2011.

RESULTS

The pressure exerted by anti-embolism stockings reduced by between 15 and 24% after 24h of wear, it reduced by between 21 and 32% when worn continuously for 8days. Allowing stockings to rest for a day between days of wear allowed them to recover slightly but this recovery was only temporary. Washing stockings regenerated their pressure delivering potential significantly and machine washing allowed some to recover to exert more pressure than they had when new.

CONCLUSIONS

Different brands of anti-embolism stockings exert different pressures on the same size of leg, when correctly fitted. The pressure exerted by anti-embolism stockings decreases with use but the correct pressure gradient is maintained if correctly fitted. Washing stockings after 24h of wear is effective in restoring their pressure delivering abilities and in some cases can surpass their 'as new' pressure delivering ability.

Finite element analysis of the deformation of deep veins in the lower limb under external compression

Compression devices applied to the lower limb can help improve venous flow by deforming the muscles and veins. In this study, a two-dimensional finite element model using displacement boundary conditions was employed to simulate the deformations of deep veins in the calf under external compression. Magnetic resonance (MR) scans were performed on four healthy volunteers with and without compression stockings. The displacement boundary condition was extracted from the corresponding deformed (with stocking) and undeformed (without stocking) MR images by using a non-rigid image registration procedure. In the finite element model, soft tissues of the calf were simplified as a homogenous material with hyperelastic properties. The effective bulk modulus of the material was evaluated at a chosen transverse section for each subject, which was also applied to three other locations at 2mm, 6mm and 10mm below the original section. Comparison between the simulation and measurement showed good agreement in area reduction of deep veins (discrepancy=8.7±6.4%), especially for sections close to the chosen location where the effective bulk modulus was evaluated. Beyond a certain distance, the discrepancies increased and became quite variable. The reason for this is that the architecture and stiffness of the calf tissues vary along the leg. The results also showed considerable variation in effective bulk modulus among the four subjects examined.

Knee length versus thigh length graduated compression stockings for prevention of deep vein thrombosis in postoperative surgical patients

BACKGROUND

Graduated compression stockings (GCS) are a valuable means of thromboprophylaxis in hospitalised postoperative surgical patients. But it is still unclear whether knee length graduated compression stockings (KL) or thigh length (TL) stockings are more effective.

OBJECTIVES

The aim of this review was to systematically analyse the randomised, controlled trials that have evaluated the effectiveness of KL versus TL GCS as a thromboprophylaxis tool in hospitalised patients undergoing various types of surgery.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched February 2012) and CENTRAL (2012, Issue 1). The authors searched MEDLINE and EMBASE (until 27 February 2012) and they also searched the reference lists of relevant articles to identify additional trials.

SELECTION CRITERIA

Randomised controlled trials published in any language on KL versus TL GCS used as a thromboprophylaxis tool in hospitalised patients of any age and either gender.

DATA COLLECTION AND ANALYSIS

Data extraction was undertaken independently by two review authors using data extraction sheets and confirmed by the third review author.

MAIN RESULTS

Three studies, with a combined total of 496 patients, matched the inclusion criteria for this review. All three included studies evaluated the role of KL and TL in thromboprophylaxis among a group of postoperative patients. These studies showed no significant difference in the ability of the two modalities of leg compression to reduce the incidence of deep vein thrombosis in postoperative patients. In both the fixed-effect model (odds ratio (OR) 1.55, 95% confidence interval (CI) 0.78 to 3.07, P = 0.21) and random-effects model (OR 1.32, 95% CI 0.43 to 4.06, P = 0.63) KL graduated compression stockings were as effective as TL stockings in thromboprophylaxis. However, there was significant heterogeneity (Tau(2) = 0.50; Chi(2) = 4.12, df = 2 (P = 0.13); I(2) = 51%) among trials. Results of this review may be considered weak because there was significant heterogeneity among included trials resulting from inadequate randomisation techniques, allocation concealment, power calculations and the absence of intention-to-treat analysis.

AUTHORS' CONCLUSIONS

This review found that there is insufficient high quality evidence to determine whether or not KL and TL GCS differ in their effectiveness in terms of reducing the incidence of deep vein thrombosis (DVT) in hospitalised patients.  A major multicentre RCT is required to address this issue. In the meantime, the decision on which type of stocking to use in clinical practice is likely to be influenced by factors such as patient compliance, ease of use and cost implications.

Evaluation and management of stroke

In contrast to myocardial infarction, stroke is a heterogeneous disease with multiple different causes. Determination of stroke mechanism is critical to choosing optimal therapy to prevent recurrence. This article reviews the diagnostic approach to stroke and prognostic and treatment implications of specific stroke mechanisms. Data on the role of antiplatelet and anticoagulant therapy in secondary stroke prevention, as well as the role of these agents and thrombolytic therapy in acute stroke treatment are reviewed. Situations of particular relevance to the practicing hematologist—stroke in the young, patients with multiple recurrent strokes, patients with abnormal hypercoagulable laboratory testing, and treatment of intracerebral hemorrhage following thrombolytic therapy—are discussed.