Lesson of the week: Pneumatic compression boots for prophylaxis against deep vein thrombosis: beware occult arterial disease

BMJ 1998;316:454-455 (7 February)

Clinical review

Lesson of the week: Pneumatic compression boots for prophylaxis against deep vein thrombosis: beware occult arterial disease

M J Oakley, specialist registrar,^a E F Wheelwright, consultant,^b P J James, consultant ^a

^a Orthopaedic Directorate, Glasgow Royal Infirmary, Glasgow G4 0SF, ^b Orthopaedic Directorate, Stobhill Hospital NHS Trust, Glasgow G21 3UW

Correspondence to: Mr James

Introduction

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Introduction
Guidelines
Case review
Discussion
References

Prophylaxis against venous thromboembolism after joint replacementremains contentious.¹ The incidence of deep vein thrombosisis between 45% and 75%.² ³ ⁴ ⁵ The rate of fatal pulmonary embolismis considered to be 1-3%,² ³ ⁴ ⁵ but this is a gross overestimate.¹Pharmacological techniques for preventing deep vein thrombosis(such as dextran 40, aspirin, warfarin, and heparins) are effectivein reducing its incidence but are associated with importantcomplications such as haemorrhage, wound haematoma, and haemarthrosis.³ ⁶ ⁷ ⁸

Mechanical methods such as intermittent pneumatic compressiondevices have been developed to avoid these problems. These providesimilar prophylaxis against deep vein thrombosis ⁸ ⁹ ¹⁰ andare considered free of important complications.⁸ We report theoccurrence of ulcers in patients using these devices accordingto approved guidelines.

Guidelines

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Introduction
Guidelines
Case review
Discussion
References

Consideration of the evidence led the orthopaedic directorateof Glasgow Royal Infirmary and Stobhill NHS Trust to changeits policy on prophylaxis against deep vein thrombosis at theend of 1995. Under the previous protocol heparin had been usedin combination with graduated compression stockings. All patientshaving elective surgery who are at moderate or high risk ofdeep vein thrombosis now wear graduated compression stockingson both legs under pneumatic compression boots (AV Impulse System,Novamedix, Andover) (fig 1). Their design is based on the foot'sphysiological pumping mechanism.¹¹ The boot applies pulsatilecompression to the sole of the foot (fig 2). Patients receivepneumatic compression treatment on the ward until they are fullymobile; treatment is interrupted for physiotherapy. The compressionboots do not interfere with the operative site and are effectiveprophylaxis against deep vein thrombosis. ¹² ¹³ ¹⁴ ¹⁵

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Fig1 Pneumatic compression boot (top); as worn by patient (bottom)

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Fig 2 Inflation cycle at two pressure settings of pneumatic compression boot. Boot inflates for 1 s during every full cycle of 20 s

The contraindications described by the manufacturer are congestiveheart failure, pre-existing deep vein thrombosis, thrombophlebitis,and pulmonary embolism. The manufacturer also includes adviceon care of the patient's skin and advises that extra attentionshould be given to patients with poor circulation, fragile skin,insensitive extremities, diabetes, and problems with tissueviability, and to those taking anticoagulants. These conditionsare not regarded as contraindications.

Case review

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Introduction
Guidelines
Case review
Discussion
References

The new protocol was implemented in December 1995 and the firstproblem occurred two months later. The compression boots wereused on about 200 patients over the five months analysed. Fivepatients developed foot ulcers. These were deep and situatedon patients' heels or bunions, or both. In four cases the ulcersoccurred on one foot and in one case on both feet. The ulcerswere not necessarily on the leg that had been operated on. Allulcers healed slowly over 3-10 months.

Causes of ulcers
We considered that the ulcers had four possible causes. Firstly,the ulcers may have been due to poor nursing care. The fivepatients were, however, operated on by four different consultantsworking in the two separate trusts with a common orthopaedicdirectorate. Nursing care was provided by experienced staffin three wards dedicated to elective orthopaedic surgery atthe two sites.

Secondly, the patients could have had occult vascular insufficiency,but all of them had palpable foot pulses before surgery andnone had a history that suggested vascular claudication. However,one patient (case 1) had a diagnosis of neurogenic claudicationsecondary to spinal stenosis and another (case 2) took quininesulphate for cramps at night. In two cases (3 and 4) postoperativeangiography revealed lesions amenable to treatment. We retrospectivelyreviewed the ratio of ankle to brachial pressure in the otherthree patients. In one (case 2) it was significantly reducedat 0.55 (normal value is about 1; significant insufficiencyis <0.7). Thus three patients (cases 2, 3, and 4) had vascularinsufficiency that, because of poor exercise tolerance relatedto the problem in the joint, was not identified earlier. Incases 1 and 5 the index was inconclusive, and without furtherinvestigation vascular insufficiency cannot be proved.

Thirdly, the boots could have caused ulceration through chafing,for example. Two patients (cases 3 and 4) reported discomfortwhile using them. The skin looked normal on close inspectionand they continued to use the boots but with more frequent checkingof the skin. Postoperative confusion in two further patients(cases 1 and 5) may have reduced their ability to communicatetheir discomfort.

Finally, other associated diseases could have resulted in ulcers.The patients had osteoarthritis, rheumatoid arthritis, and avascularnecrosis, but no other common factors could be found.

Discussion

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Case review
Discussion
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We had had no similar postoperative problems before the introductionof the new regimen for prophylaxis against deep vein thrombosis,and we have been unable to find reports of problems with thenew protocol in the published work. We believe that these fivecases are not an unrelated flurry of unfortunate cases. Thereview of the cases has led us to conclude that the problemis multifactorial. Occult vascular insufficiency seems to beimportant but was not detected preoperatively because of thelow demand these patients place on their blood system. In twopatients (cases 3 and 4) a severely diseased vessel might havebecome occluded during the manipulation required for joint replacement.

Inflation in the pneumatic compression boot lasts only for 1second in a cycle of 20 seconds. In some cases this may be sufficientfor the stocking to be gradually tightened with each pulse,which may lead to a build up of pressure. This constant pressurecould be much more important in the aetiology of the ulcersthan the pulsatile pressures generated by the boots themselves.

In retrospect some ulcers could have been avoided by removingthe compression boots at the first indication of discomfort.Medical and nursing staff now use a specially designed algorithmto aid decision making about continuing treatment with the pneumaticcompression boots when patients experience discomfort (fig 3).This has prevented further cases of ulcers developing in patients.

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Fig 3 Algorithm used in management of patients experiencing discomfort while using pneumatic compression boots

Both medical and nursing staff have a greater awareness of theproblems of occult vascular disease, and there is now a lowerthreshold for removing the boots and changing management strategies.Because this seems to have controlled the problem we have notimplemented routine Doppler ultrasound examinations. We remaincommitted to this method of prophylaxis against deep vein thrombosisbut will continue to monitor our results.

References

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Introduction
Guidelines
Case review
Discussion
References