Venous thromboembolism prophylaxis used by consultant general surgeons in Scotland

Introduction Methods Results

Discussion Conclusion References

Background: Venous thromboembolism (VTE) is a common source of morbidity and mortality in general surgical patients. Guidelines have been produced to help guide doctors through the complex issue of VTE prophylaxis. This study intended to examine the use of VTE prophylaxis amongst general surgeons in Scotland, with reference to nationally produced guidelines. Method: A postal questionnaire was sent to all consultant general surgeons in Scotland. They were asked to give their opinion on the best means of VTE prophylaxis in six different clinical scenarios. The responses were evaluated with reference to the guidelines from the Scottish Intercollegiate Guidelines Network (SIGN). Results: A 69% response rate was achieved. There was a wide variance in the suggested prophylaxis in each of the scenarios. With reference to SIGN guidelines, 35% of responses represented undertreatment, 16% overtreatment and 49% appropriate treatment. Conclusion: Despite the publication of VTE guidelines, there is still a wide variety of opinions amongst consultant general surgeons with regards to VTE prophylaxis. Many of the responses were not consistent with such guidelines and represent suboptimal prophylaxis for patients.

Keywords: venous thromboembolism, prophylaxis

J.R.Coll.Surg.Edinb., 46, December 2001, 329-333 

INTRODUCTION

Venous thromboembolism (VTE) remains an important complication in hospital patients. As many as 25% will develop a deep venous thrombosis (DVT) as in-patients and around 0.9% of all hospital admissions will suffer a fatal pulmonary embolism (PE).^1,2 The use of prophylaxis has been examined in patients dying as a consequence of VTE, highlighting its omission in 56% of cases.³ This problem has been addressed through national guidelines which have been designed and widely distributed to the profession through both The Scottish Intercollegiate Guidelines Network (SIGN) and Thromboembolic Risk Factor Consensus Group (THRIFT).^2,4 These demand the early assignment of patients into low, moderate or high-risk categories with specific recommendations for prophylaxis. This encourages targeting of prophylaxis to those likely to benefit most, while avoiding unnecessary expense and potential side effects. This study reports on the use of VTE prophylaxis by general surgeons in Scotland in the wake of the SIGN guidelines. Six scenarios with patients at three levels of VTE risk were described and the recommended prophylactic regimens of consultant general surgeons recorded using a postal questionnaire.

METHODS

Consultant general surgeons practising in Scotland were identified from the Medical Directory and a postal questionnaire sent along with a pre-paid envelope. The questionnaire consisted of six scenarios in which surgical patients may require prophylaxis for VTE. Consultants were asked to give their choice of VTE prophylaxis for each scenario from a list of: unfractionated heparin (UFH), low molecular weight heparin (LMWH), graduated compression hosiery (GCH) or intermittent pneumatic compression (IPC). Respondents were also given the opportunity to provide additional comments. Details of the scenarios are presented in Table 1.

Table 1: Scenarios presented to consultant surgeons

RESULTS

One hundred and seventeen replies were received from a total of 169 questionnaires sent out (69% response rate). The responses for each scenario are presented in Table 2. In addition, in response to scenario 1, 16 respondents (9%) indicated they would only perform the operation after the patient had stopped the oral contraceptive pill. In response to scenario 4, 13 respondents (8%) commented that they would use pharmacological methods only if they were haemodynamically stable.

The results were analysed with reference to SIGN guidelines to determine whether responses represented undertreatment, overtreatment or appropriate treatment. The results of this analysis are shown in Figure 1.

Table 2: Responses given by consultant general surgeons to six clinical scenarios UFH: unfractionated heparin; LMWH: low molecular weight heparin; GCH: graduated compression hosiery; IPC: intermittent pneumatic compression

Figure 1: Responses from surgeons, and whether they represent undertreatment, overtreatment or appropriate VTE prophylaxis with reference to SIGN guidelines.

DISCUSSION

The cornerstone of both the SIGN and THRIFT guidelines is the early identification of VTE risk with the application of appropriate prophylaxis. Risk assessment should occur routinely at the earliest opportunity, either in the clinic or ward preoperatively for elective patients or at the time of initial assessment of emergency patients. It should be a core detail included formally in patient documentation and as routine recording of personal details and vital signs. The scenarios presented in this study represent a spectrum of VTE risk that can be categorised with relative ease. Certain of the more important considerations in risk assessment are detailed in Table 3 along with the appropriate level of prophylaxis (Table 4). The response rate of 69% is acceptable, although some selection bias is likely as a consequence. Although most surgeons employed similar strategies in VTE prophylaxis, there was a marked spectrum of responses.

Scenario 1 described unilateral varicose vein surgery in a 32-year-old female taking the combined oral contraceptive pill (COCP) which is a known risk factor for VTE.5 Fifteen percent of the surgeons did not offer a suggestion regarding prophylaxis and 34% preferred to stop the oral contraceptive pill prior to surgery. It is generally accepted that the potential problems from unwanted pregnancy negate the benefits of stopping the COCP and this practice is not supported by formal guidelines. Despite the anticipated short duration of surgery and the likelihood of early mobilisation it would be appropriate to assess this patient as having a moderate risk of VTE in view of the use of COCP. A single form of prophylaxis should be considered and graduated compression stockings would be preferred as these can be easily continued into the convalescent period. Twelve percent of surgeons chose not to use VTE prophylaxis in this patient.

The 60-year-old man in scenario 2 undergoing anterior resection must be considered as high risk in view of the nature and duration of surgery along with the presence of malignant disease. He should, therefore, be offered multi-modality prophylaxis and the majority of respondents agreed with this. Nineteen percent of surgeons offered single agent prophylaxis which is insufficient and two surgeons failed to provide any recommendation.

The 57-year-old woman undergoing hernia repair in scenario 3 is at low risk and does not require specific VTE prophylaxis other than general factors such as encouraging early mobilisation. At the time of the questionnaire there was no firm evidence that HRT increased VTE risk, although recent publications suggest there may indeed be some increased risk, although less than the combined oral contraceptive pill.^6,7 In the absence of other risk factors, age alone does not have a significant effect. Only 13% of respondents suggested that no VTE prophylaxis was appropriate. Forty-five percent of respondents suggested prophylaxis with two or more measures which is excessive. Although such zeal is well intentioned it incurs unnecessary expense and all methods of prophylaxis have potential complications.^8-10

The 29-year-old trauma victim with an unstable pelvic fracture represents a more complex problem. The risk of VTE is indisputable and he must be considered at high risk. However, the use of heparin is tempered by concerns of ongoing pelvic bleeding. Guidelines suggest the use of all mechanical means of VTE prophylaxis with the introduction of chemical means at the earliest opportunity following stabilisation of the pelvic injury and cessation of bleeding. Fifty-four percent of the respondents suggested regimens which would be considered an under treatment, 12% suggested no prophylaxis was necessary and 11% did not provide a suggestion stating that they did not deal with pelvic trauma. The use of VTE prophylaxis has been debated in other studies examining trauma patients and there are a variety of opinions.11,12 It is striking that only 33% of respondents offered multi-modality prophylaxis in this case, compared with over 45% in the 56-year-old lady undergoing hernia repair in scenario 3 and 58% in scenario 5, neither of whom was at more than moderate risk.

The VTE risk of the 69-year-old man undergoing thyroidectomy in scenario 5 is moderate, and he should be offered single agent prophylaxis. Many surgeons undertaking surgery of this nature wish to avoid heparin but this or graduated compression stockings would be appropriate.

Table 3: Risk factors for venous thromboembolism. (SIGN)⁴ 

Table 4: Recommended prophylaxis for low, moderate and high risk groups of patients
(taken from SIGN guidelines).

Fifty-eight percent of surgeons agreed with this, offering prophylaxis with either chemical or mechanical means, 25% suggested prophylaxis with two or more agents and 18% would not use prophylaxis.

The patient in scenario 6 must be considered at high risk of VTE, with the presence of emergency abdominal surgery in an elderly man with coexisting morbidity. The efficacy of aspirin is under debate in VTE prophylaxis and in combination with heparin increased complications can be anticipated.^{1,4, 13, 14} Three respondents offered no prophylaxis and 38% offered single agent prophylaxis with either mechanical or chemical means. The majority of surgeons offered appropriate multi-modality prophylaxis.

LMWH has been shown to have an advantage over UFH in orthopaedic cases where it is associated with a reduction in VTE risk with no increase in bleeding risk. It may also be more favourable because of its once daily administration. No advantage, however has been demonstrated in general surgical cases.¹⁵ Furthermore, it has a longer duration of action and is less readily reversed by protamine, which can lead to problems if its action needs to be stopped. Despite this, 43% of respondents recommended the use of LMWH over UFH in the general surgical patients of scenarios 1,2,3,5 and 6.

The spectrum of practice in VTE prophylaxis is particularly apparent from scenarios 1 and 4 in which the same proportion of surgeons recommended no prophylaxis as multimodal means. This highlights the failure of adherence to a standardised approach to VTE prophylaxis. Prophylactic measures are often instituted by the most junior doctors often in consultation with nursing staff, therefore, clarity and the avoidance of ambiguity is a prerequisite if appropriate prophylaxis is to be employed. The situation where different regimens are employed by surgeons in the same firm is obviously to be avoided.

These data do not allow in-depth analysis but the picture emerging suggests that a subgroup of surgeons view VTE risk as either absent or present and accordingly offer no prophylaxis or maximum prophylaxis. Although this ‘all or none’ approach is generally well intentioned it is at odds with current national guidelines. In contrast, it is apparent from the under use of VTE prophylaxis in high-risk scenarios 2 and 4, that the surgical community is still displaying a certain complacency towards VTE and the value of prophylaxis. Consultants are generally seen as being responsible for the education of staff and the implementation of guidelines, and it is, therefore, appropriate that strategies to implement guidelines should be aimed at them.¹⁶

CONCLUSION

Guidelines, such as those produced by SIGN, are becoming an everyday part of clinical practice. Their intention is to make care more consistent and efficient and to help clinicians practise that which is supported by evidence.¹⁷ They are particularly useful in complex areas such as VTE prophylaxis, allowing optimisation of treatment. Guidelines have been criticised as sometimes ignoring resource implications, and restricting doctors discretion and autonomy.¹⁸ However, the suggestions for VTE prophylaxis are not particularly costly and there is considerable scope for the clinician to determine the exact method in individual cases. Despite this, this study shows that there is still widespread disregard for these nationally produced guidelines.

Whilst they are not intended to be a legal benchmark, with the increasing prominence of clinical governance and the audit of clinical practice, those doctors who continue to ignore guidelines will be under increasing pressure to justify and possibly alter their practice.

REFERENCES

1. Claggett GP, Reisch JS. Prevention of venous thromboembolism in general surgical patients. Result of meta-analysis. Annals of Surgery 1988; 208: 227-40
2. Lowe GDO, Greer IA, Cooke TG, Dewar EP, Evans MJ, Forbes CD, Mollan RAB, Scurr JH. Risk of and prophylaxis for venous thromboembolism in hospital patients. BMJ 1992;305:567-74
3. Gillies TE, Ruckley CV, Nixon SJ. Still missing the boat with fatal pulmonary embolism. Br J Surg 1996; 83: 1394 - 5
4. Anonymous. Prophylaxis of Venous Thromboembolism. Edinburgh. Scottish Intercollegiate Guidelines Network (SIGN). 1995
5. Vessey M, Mant D, Smith A, Yeates D. Oral contraceptives and venous thromboembolism: findings in large prospective study. BMJ 1986; 292: 526
6. Hoibraaten E, Abdelnoor M, Sandset PM. Hormone replacement therapy with estradiol and risk of venous thromboembolism - a population-based case-control study. Thromb Haemost 1999; 82: 1218-21
7. Douketis JD, Gordon M, Johnston M, Julian JA, Adachi JR, Ginsberg JS. The effects of hormone replacement therapy on thrombin generation, fibrinolysis inhibition and resistance to activated protein C: prospective cohort study and review of literature. Thromb Res 2000; 99: 25-34
8. Heath D, Kent S, Johns D, Young T. Arterial thrombosis associated with graduated pressure antiembolic stockings. BMJ 1987; 295:580
9. Nelson-Piercy C. Hazards of heparin: allergy, heparin induced thrombocytopaenia and osteoporosis. Ballieres Clin Obstet Gynaecol 1997; 11(3):459-66
10. Oakley M, Wheelwright E, James P. Pneumatic compression boots for prophyalxis against deep vein thrombosis: beware occult arterial disease. BMJ 1998; 316:454
11. Spain D, Richardson D, Polk H, Bergamini T, Wilson M, Miller F. Venous thromboembolism in the high-risk trauma patient: do risks justify aggressive screening and prophylaxis? J Trauma 1997;42: 463-7
12. Piotrowski J, Alexander J, Brandt C, McHendry C, Yuhas J, Jacobs D. Is deep vein thrombosis surveillance warranted in high-risk trauma patients? Am J Surg. 1996; 172: 210-3
13. Sors H, Meyer G. Place of aspirin in prophylaxis of venous thromboembolism. Lancet 2000; 355: 1288-9
14. Antiplatelet Trialists’ Collaboration. Collaborative
17. West E, Newton J. Clinical guidelines. BMJ 1997; 315: overview of randomised trials of antiplatelet therapy -III: Reduction in venous thrombosis and pulmonary embolism by antiplatelet prophylaxis among surgical and medical patients. BMJ 1994; 308: 235-46
15. Nurmohamed MT, Rosendaal FR, Buller HR, Dekker E, Hommes DW, Vandenbroucke JP, Briet E. Low molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis. Lancet 1992; 340: 152-6 
16. Walker A, Campbell S, Grimshaw J. Implementation of a national guideline on prohylaxis of venous thromboembolism: a survey of acute services in Scotland. Health Bull (Edinb) 1999; 57: 141-7
18. Haycox A, Bagust A, Walley T. Clinical guidelines - the hidden costs. BMJ 1999; 318: 391-393

Copyright date: 7th July 2001

Correspondence: P. Burns, University Department of Vascular Surgery, Lincoln House, Birmingham Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS, UK

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