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Evaluating an intermittent compression system for thromboembolism prophylaxis

Denise Van Blerk, RN, Dip Orthopaedics

Matron for Orthopaedics at Barts and The London NHS Trust

Venous thromboembolism (VTE) is a disease process with a multifactorial pathogenesis that has two major clinical manifestations, namely deep-vein thrombosis (DVT) and pulmonary embolism (PE) (Hyers, 1999). VTE contributes to longer hospital stays, chronic morbidity and mortality (Turpie et al, 2002). PE arising from DVT is the most common avoidable cause of death (Agu et al, 2000), and adequate prophylaxis in high-risk patients is highly cost-effective (Anderson and Spencer, 2003).

Venous thromboembolism (VTE) is a disease process with a multifactorial pathogenesis that has two major clinical manifestations, namely deep-vein thrombosis (DVT) and pulmonary embolism (PE) (Hyers, 1999). VTE contributes to longer hospital stays, chronic morbidity and mortality (Turpie et al, 2002). PE arising from DVT is the most common avoidable cause of death (Agu et al, 2000), and adequate prophylaxis in high-risk patients is highly cost-effective (Anderson and Spencer, 2003).

DVT incidence is estimated to be about five per 10,000 a year among the general population (Fowkes et al, 2003). However, among hospital inpatients, the incidence is much higher. Without the use of prophylaxis, the incidence ranges from 45% to 51% in trauma and orthopaedic patients (International Consensus Statement, 2001). There are several highly effective and safe methods of VTE prophylaxis, including low molecular weight heparin, unfractionated heparin, warfarin and intermittent pneumatic compression (IPC).

This article looks at the use of IPC as one method of prophylaxis in the context of a small evaluation study of a new IPC device undertaken at the Royal London Hospital.

The pathophysiology of DVT involves three interrelated factors, first described by Virchow in 1856, but which are still valid today. These are venous stasis, injury to the blood vessel wall and altered blood composition. It is generally accepted that two or more factors are needed to initiate thrombus formation.

Small deposits of fibrin form in the deep veins of the calf and/or the thigh as a result of slow blood flow, accompanied by a local activation of the blood-clotting cascade as a result of both local and systemic thrombogenic stimuli. These small deposits form the initial nidus of the thrombus, which attracts and entraps blood cells and further fibrin. If the thrombus becomes large enough, it may cause blood outflow problems, resulting in swelling and pain in the affected limb. In some cases, pieces of the thrombus can dislodge and occlude one or more of the pulmonary blood vessels, resulting in a PE.

Surgical procedures significantly increase the risk of DVT. This is due to factors such as immobility, the nature of the operation, anaesthesia, dehydration and sepsis (ICS, 2001). The risk is also increased by factors such as increased age, presence of malignancy, a history of thrombosis, obesity and thrombophilic states (SIGN, 2002).

Post-thrombotic syndrome develops in 20-50% of patients within two years of symptomatic DVT, while associated venous leg ulceration develops in up to a third of such patients (Kahn and Ginsberg, 2004). This is associated not only with patient morbidity but also with significant cost, estimated to be about £1400 per patient per treatment episode (Carr et al, 1999).

Management of DVT commonly involves treatment with anticoagulant drugs to prevent formation of further thrombus while allowing the body to naturally disperse the clot. Routine prophylaxis reduces morbidity, mortality and costs in hospitalised patients at risk of VTE (SIGN, 2002; ICS 2001). Yet, despite this, there are wide variations in practice.

All patients admitted to hospital should be assessed by a health-care professional to determine whether VTE prophylaxis is required. The decision also needs to be balanced against the potential complications of using prophylactic agents, such as the risk of bleeding and associated expense (Anderson and Spencer, 2003).

All modalities, including IPC, are used at the Royal London Hospital. IPC is a safe, cost-effective and complication-free alternative to anticoagulant therapy (Ginzburg et al, 2003; Morris and Woodcock, 2004). It acts directly on two of the three causative factors in Virchow's triad - venous stasis and blood coagulability.

The trial
The trauma and orthopaedic unit at Barts and the London NHS Trust decided to trial a new IPC device, the Flowtron(R) Universal DVT Prophylaxis System (Huntleigh Healthcare Ltd). The unit is spread over two wards, and has 26 elective beds and 27 trauma beds, covered by 10 consultants. Standard prophylaxis before the evaluation was achieved using graduated compression stockings and/or low molecular weight heparin. IPC was introduced to the protocol owing to the high risk in this patient group and following best practice (SIGN, 2002).

The evaluation aimed to discover whether nurses and patients found the new system easy to use and acceptable.

Methodology
Patients considered for inclusion were at high risk of DVT, were due to have elective joint replacement surgery and would normally have been prescribed prophylaxis The study was approved by the local research ethics committee and each patient gave informed consent. Data were collected by means of a questionnaire that included patient characteristics, risk factors, other prophylaxis and clinical outcome.

Garment type was determined depending on the size of the patient, size of limb and the type of surgical procedure to be undertaken. Patients were excluded if they were suspected to have a DVT, thrombophlebitis or PE, severe peripheral arterial disease, severe heart failure or any local condition in which the garments may interfere such as local infections, recent skin grafts or dermatitis.

Patients fulfilling the criteria participated in the evaluation until fully ambulant or were discharged/transferred from the unit.

Results
Thirty patients (10 men; 20 women) with a mean age of 68 years (range 23-97) completed the evaluation over a mean period of seven days. Twenty-seven (90%) had major orthopaedic surgery. Nineteen patients (64%) used a calf garment, 10 (33%) a foot garment, and one used both foot and calf garments: the foot garment on one limb and calf on another. A range of prophylactic measures were being used, with almost a quarter of patients receiving IPC alone. No patient developed a VTE during the study period.

Patient feedback Twenty-three (85%) of the twenty-seven patients who gave feedback reported the Flowtron Universal System to be comfortable or very comfortable. Three patients who reported discomfort or sleep disturbance had been allocated the foot garment. Although rare, this finding is not system specific (Pitto et al, 2004) and relates to the higher pressures required to compress the muscle surrounding the blood- filled plantar plexus.

Nurse feedback Twenty nurses were asked to rate the equipment on practical features, such as ergonomics, weight, vibration and noise, as well as a number of safety features - cable length, tubing length, alarm interpretation and the ability to decontaminate. The nurses were also asked to rate whether the operation of the device and the illuminated functional display were intuitive.

All nurses rated the device highly positively and said they would use it again.

Best practice
Best practice guidelines clearly state that prophylaxis reduces morbidity, mortality and costs in hospitalised patients at risk of deep-vein thrombosis and PE (SIGN, 2002). Choice of prophylactic modality is important, it should be free from clinically important side-effects, be easy to administer, be relatively inexpensive and require minimal intervention and monitoring.

In this small study, both patient and nurse satisfaction was high. This led to good compliance with the use of the system and positive clinical outcomes in patients: more than half the respondents (n=16) received mechanical prophylaxis only, either IPC in association with graduated compression stockings (n=9) or IPC alone (n=7); none developed VTE.

In addition, compared with chemical prophylaxis, IPC offers a cost-effective solution, while avoiding some of the potential complications associated with altered coagulation.

Risk factors for DVT
- Immobility

- Anaesthesia

- Dehydration

- Sepsis

- Presence of malignancy

- Age

- History of thrombosis

- Obesity

- Thrombophilic states

Source: ICS, 2001; SIGN, 2002

Authors contact details
Denise Van Blerk, Matron for Orthopaedics, The Royal London Hospital, Whitechapel, London E1 1BB. Email: denise.vanblerk@bartsandthelondon.nhs.uk

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