Annals of the Royal College of Surgeons of England (1991) vol. 73, 219-222

Audit of attitudes to and use of postoperative thromboembolic prophylaxis in a regional health authority David R Jones

MCh FRCS FRCSEd

Registrar

Countess of Chester Hospital, Liverpool Road, Chester

Key words: Deep vein thrombosis, postoperative; Thromboembolism; Pulmonary embolus

A survey of usage and attitudes to thromboembolic prophylaxis among 46 general surgeons in the Mersey Region found that 87% use either low-dose heparin, graduated compression stockings or both on a regular basis for their major cases. However, there was a wide variation of usage: 9 (19.6%) always used heparin in combination with thromboembolic stockings, 4 (8.7%) always used heparin alone, no surgeon used thromboembolic stockings alone. A total of 18 (39%) used thromboembolic stockings in combination with heparin, one-half of them selectively. A further 24% of surgeons used either low-dose heparin or thromboembolic stockings or both on selected patients. Current literature beliefs concerning the efficacy of low-dose heparin and thromboembolic stockings showed a similar variation, with 13% of surgeons believing that the efficacy of low-dose heparin against postoperative deep vein thrombosis has not been shown, 22% believing that thromboembolic stockings were ineffective against postoperative deep vein thrombosis, and 24% believing that low-dose heparin was of no value as a prophylactic agent against postoperative pulmonary embolism. Published meta-analysis has shown these beliefs to be wrong.

The Confidential Enquiry into Perioperative Deaths (1) identified a significant increase in deaths from pulmonary embolism in those patients who were not given deep vein thrombosis prophylaxis. The Enquiry stated that the general surgical assessors 'seemed to support a consensus that prophylaxis (against pulmonary embolism) was valuable'. This language is careful and reflects the fact that there is a diversity of opinion among surgeons regarding Present appointment: Hon Registrar, Vascular Studies Unit, Bristol Royal Infirmary Correspondence to: Mr D R Jones, 556 Pensby Road, Thingwall, Wirral L61 7UE

the necessity, efficacy and safety of thromboembolic prophylaxis. How is this uncertainty manifested in surgical practice and can such a diversity of opinion be justified? Current practice relating to prophylaxis of postoperative thromboembolism has been surveyed among general surgeons working in the Mersey Region.

Questionnaire design Consultant surgeons working in the Mersey Region were asked to complete a questionnaire principally asking for a yes or no answer to the question: 'Do you regularly use prophylaxis against deep vein thrombosis in major cases'. Supplementary questions under this heading asked which major cases received prophylaxis, and if the answer to the initial question was 'no' then to explain the reasons.

A midsection of the questionnaire asked whether lowdose heparin, thromboembolic stockings or another method was used and whether usage applied to all cases, selected cases or none. An invitation was given to discuss which selected cases received prophylaxis and what percentage of major cases had prophylaxis. A further four questions were asked concerning each surgeon's beliefs from the current literature regarding the benefits of each agent against postoperative deep vein thrombosis or pulmonary embolism. A supplementary question for low-dose heparin asked surgeons whether the benefits of prophylaxis outweighed the risk. A stamped addressed envelope and covering letter was included with each questionnaire asking for any additional comments to be written on the reverse of the paper. Initial non-responders were recirculated after 1 month.

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D R Jones

Table I. Use of prophylactic agents against postoperative thromboembolism by general surgeons (n = 46) Heparin + TED stockings in all patients Heparin + TED stockings selectively Heparin alone TED stockings + heparin selectively TED stockings alone Heparin selectively and/or TED stockings selectively No regular prophylaxis used

9 7 4 9

(19.6%) (15.2%) (8.7%) (19.6%)

0 11 (23.9%) 6 (13.0%)

Table III. Literature beliefs among surgeons. Nonregular users of prophylaxis (n = 6) Yes No Don't know Heparin has anti-DVT activity Heparin has anti-PE activity Does benefit outweigh risk? TED stockings have anti-DVT activity TED stockings have anti-PE activity

4 3 1 3 2

2 3 4 2 3

0 0 1 1 1

DVT = Deep vein thrombosis PE = Pulmonary embolism

Results A total of 46 completed questionnaires were returned (90%). In response to the initial question concerning the regular use of prophylaxis in major cases, 40 (87%) replied yes. Twenty-nine surgeons (63%) replied that some form of prophylaxis was used in all cases. The variation within this group regarding choice and usage of prophylactic agent was widespread (Table I). Thus only 20 surgeons (43%) always used heparin; nine of them always used TED® thromboembolic stockings as well, whereas four never did. A total of 18 surgeons (39%) always used thromboembolic stockings, including the nine who always used them with heparin. The other nine used heparin in a selective manner in combination with thromboembolic stockings. A further 11 surgeons were selective in their use of prophylaxis, using either heparin or thromboembolic stockings, or both in selected patients. Selection criteria differed in each case. Most surgeons included patients with malignancy, obesity, a history of previous thromboembolic disease, or who were taking the contraceptive pill. Several used age as a selection criterion, but the cutoff point ranged from 45 years to 60 years. Reasons for non-regular prophylaxis included a terse 'not necessary' and 'not convinced of benefit or efficacy' by two surgeons, 'early ambulation is most important', and use of a high degree of selectivity aimed at those patients on the oral contraceptive pill, with gastrointestinal malignancy or with previous thromboembolism, by another two surgeons. Overall replies to the questions regarding current literature beliefs are shown in Table II. Although some

four out of five surgeons believe heparin has been shown to be of benefit against postoperative deep vein thrombosis, nearly one-quarter believe this not to have been proved for pulmonary embolism. Beliefs concerning the available literature for the use of thromboembolic stockings were not as firm as for heparin, with 72% of surgeons holding the view that they are of benefit for postoperative deep vein thrombosis prophylaxis. The majority thought that this had not yet been shown to be true for the prevention of postoperative pulmonary embolism (59%), but 28% disagreed and there were 13% 'don't knows'. The small group of six surgeons who do not regularly use prophylaxis each had diverse beliefs (Table III). Beliefs were much firmer in the 29 surgeons who always used prophylactic measures (Table IV).

Discussion Prophylaxis for postoperative thromboembolism has remained controversial in surgical practice for over 20 years. This is partly due to a large body of clinical research which has given uncertain or, in some cases, contradictory results (2-7). An attempt to make some sense of these conflicting reports has been undertaken recently in two articles which use the statistical device of meta-analysis (8,9). All available true randomised trials have been reassessed and the numbers of patients in each arm of the trial combined. The numbers involved are impressive: 15 598 patients in the article by Collins et al. (8). While there are some statistical drawbacks to the conclusions that can be

Table II. Literature beliefs among surgeons. All surgeons (n = 46)

Table IV. Literature beliefs among surgeons. Surgeons who always use prophylaxis (n = 29)

Yes No Don't know

Yes No Don't know

Heparin has anti-DVT activity Heparin has anti-PE activity Does benefit outweigh risk? TED stockings have anti-DVT activity TED stockings have anti-PE activity DVT = Deep vein thrombosis PE = Pulmonary embolism

39 33 38 33 13

6 11 6 10 27

1 2 2 3 6

Heparin has anti-DVT activity Heparin has anti-PE activity Does benefit outweigh risk? TED stockings have anti-DVT activity TED stockings have anti-PE activity DVT = Deep vein thrombosis PE = Pulmonary embolism

25 23 27 25 9

3 4 1 3 16

1 2 1 1 4

Use ofpostoperative thromboembolic prophylaxis

drawn from this type of overview, the authors have been careful to avoid bias wherever possible and to minimise errors and false-negative results (10). Results and conclusions from these two analyses are similar. Prophylaxis with heparin will reduce about onehalf of all postoperative pulmonary emboli and about two-thirds of deep vein thromboses. The International Multicentre Trial (11), the single largest study considered, showed a decrease in the number of fatal pulmonary emboli but was unable to show an overall improvement in postoperative mortality. Meta-analysis shows a highly significant decrease in deaths attributable to pulmonary embolism in those patients given prophylactic heparin. Given that heparin has a significant benefit against deep vein thrombosis, fatal, and non-fatal pulmonary embolism, do these advantages outweigh the known risks of haemorrhage and wound haematoma formation? Overview trials have been less successful in answering this question as the analysis of bleeding complications is incomplete in most trials. The analysis of Clagett and Reisch (9) identified 21 trials with suitable data. Heparin significantly increased wound haematoma incidence to 6.3% from 4.1% in controls. The overall incidence of major haemorrhage was 1.8% in heparin-treated patients against 0.8% in controls in a separate analysis of four double-blind assessment trials. Reports on the prophylactic value of graduated compression thromboembolic stockings are fewer than for heparin. The United States meta-analysis identified a total of 500 patients for analysis. The incidence of deep vein thrombosis was decreased from a control rate of nearly 25% to just over 9%, a clearly significant benefit. The data, however, are too small to allow an assessment of postoperative pulmonary embolism and no conclusions can be drawn from the current literature. These findings have recently been confirmed by Jeffery and Nicolaides (12). They identified a 60% reduction in the incidence of deep vein thrombosis using graduated compression stockings alone. In combination with low-dose heparin the incidence was reduced by 85%. Graduated compression stockings are relatively inexpensive, are easy to use and do not suffer the complication of haemorrhage, although care should be taken to see that they are properly applied and maintained in position. The consensus of reviews of the available literature show that considerable benefit is obtained by the routine prophylactic use of heparin for prevention of deep vein thrombosis, fatal and non-fatal pulmonary embolism at the expense of bleeding complications in a small percentage of patients. Graduated compression stockings also have a definite protective effect against postoperative

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deep vein thrombosis, but the available literature does not at present show this to be true for postoperative pulmonary embolism. In the Mersey Region there would appear to be room for improvement in the use of prophylactic measures. There would be a cost-effective benefit if all patients undergoing major abdominal surgery wore graduated compression stockings. The addition of heparin would significantly decrease the incidence of fatal and non-fatal pulmonary embolism. Those who are concerned about haemorrhagic complications should consider giving heparin prophylaxis in high-risk patients unless there is a specific contraindication.

References 1 Buck N, Devlin HB, Lunn JN. Report of the Confidential Enquiy into Peri-operative Deaths. London: Nuffield Provincial Hospitals Trust and the King's Fund, 1987. 2 Dalen JE, Paraskos JA, Ockene IS, Alpert JS, Hirsh J. Venous thromboembolism: scope of the problem. Chest

1986;89:Suppl:370S-373S. 3 Kakkar VV. Deep vein thrombosis. Detection and prevention. Circulation 1975;51:8-19. 4 Bergqvist D. Prevention of postoperative deep vein thrombosis in Sweden: results of a survey. World J Surg 1980;4:489-95. 5 Morris GK. Prevention of venous thromboembolism: a survey of methods used by orthopaedic and general surgeons. Lancet 1980;2:572-4. 6 Conti S, Daschbach M. Venous thromboembolism prophylaxis. Arch Surg 1982;117:1036-40. 7 Van Ooijen B. Subcutaneous heparin and postoperative haematomas: a prospective, double-blind, randomized study. Arch Surg 1986;121:937-40. 8 Collins R, Scrimgeour A, Yusuf S, Peto R. Reduction in fatal pulmonary embolism and venous thrombosis by perioperative administration of subcutaneous heparin. N EnglJ Med 1988;318: 1162-73. 9 Clagett GP, Reisch JS. Prevention of venous thromboembolism in general surgical patients. Ann Surg 1988;208: 227-40. 10 Collins R, Gray R, Godwin J, Peto R. Avoidance of large biases and large random errors in the assessment of moderate treatment effects: the need for systematic overviews. Stat Med 1987;6:245-50. 11 Prevention of fatal postoperative pulmonary embolism by low doses of heparin: an international multicentre trial. Lancet 1975;2:45-51. 12 Jeffery PC, Nicolaides AN. Graduated compression stockings in the prevention of postoperative deep vein thrombosis. BrJI Surg 1990;77:380-3.

Received 25 October 1990

Audit of attitudes to and use of postoperative thromboembolic prophylaxis in a regional health authority.

A survey of usage and attitudes to thromboembolic prophylaxis among 46 general surgeons in the Mersey Region found that 87% use either low-dose hepari...
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