Abstract
Major vascular surgery is associated with a high risk of morbidity and mortality. Targeted optimization of organ systems most likely to suffer morbidity should be made prior to elective surgery. Risk modification can reduce both perioperative and long-term complications. This article summarizes currently accepted best practice for risk modification and preoperative optimization prior to vascular surgery.
After reading this article, you should:
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understand the value of targeted optimization of organ systems in vascular surgical patients
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be aware of the interventions that can reduce perioperative risk
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appreciate the importance of lifestyle and organizational risk modification strategies in this patient group
Background
Vascular surgery carries significant risks due to the nature of the surgery and the high incidence of comorbid disease in this patient population. It is essential that risks are minimized, and patients optimized, prior to surgery in a bid to enhance patient care while delivering good surgical outcomes.
The preoperative assessment clinic can be used to establish optimal medical care to reduce postoperative complications and improve long-term outcomes through secondary risk factor modification. Ideally patients should be assessed well in advance of surgery to allow sufficient time for optimization, counselling and specialty referral if required.
This article will focus on risk modification and preoperative optimization in the elective setting only.
Risk modification strategies
Lifestyle modification
It is essential to recommend appropriate lifestyle changes in advance of potential surgery to reduce perioperative risk. A 4–6 week time window is often sufficient to enable appropriate changes, which may lead to clinically significant benefits. Such changes are generally also beneficial in the longer term in a bid to modify patient behaviour while facilitating secondary risk factor modification. Appropriate recommendations include:
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Nutritional advice – body mass index has a J-shaped relationship with morbidity following vascular surgery, with both under-weight and morbidly obese patients at risk. Dietary advice or referral to a dietician may be of benefit in these individuals.
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Smoking cessation – minimum effective period is often quoted as being 4–6 weeks. The evidence base for this recommendation is not particularly extensive, and in reality cessation of smoking at any time prior to surgery is probably beneficial.
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Regular exercise – patients with reduced physical fitness have a higher incidence of perioperative morbidity and mortality following major surgery. Preoperative exercise training can improve objectively measured levels of fitness in vascular patients, but it is unclear whether this trans-lates into improved outcome. Current evidence suggests that higher intensity aerobic interval training strategies will deliver greater fitness improvements in a shorter time-frame, with 4–6 weeks of exercise prior to surgery prob-ably the minimum effective duration. It is imperative to consider potential cardiovascular risk prior to any form of preoperative exercise prescription. Cardiopulmonary exercise testing provides a useful screening adjunct in this respect.
Reduction in surgical waiting times
Timeframes from referral to surgery should be minimized where possible to reduce risk from the vascular pathology. This is only appropriate where risks of surgery are considered to be lower than conservative management and pertains particularly to:
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Carotid surgery – current guidance recommends surgery within 2 weeks of first symptoms. Surgery at more than 12 weeks beyond symptoms is generally no longer recommended.
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Aortic surgery – both the NHS national aortic screening programme and Abdominal Aortic Aneurysm Quality Improvement Pathway recommend a target of 8 weeks from referral to surgery. This is to reduce risk of aortic rupture in the lead-up to surgery.
Non-operative management
Under certain circumstances, the risks of surgery may be deemed to exceed those of conservative management. This is often the situation in high-risk individuals. Ideally a multidisciplinary vascular team should discuss these patients before a decision is made for conservative management or best medical therapy alone.
Preoperative optimization strategies
Optimization is clearly appropriate where a decision to proceed with surgery is made following a full preoperative risk assess-ment. The preoperative assessment clinic is pivotal in this process. This will be considered under the following headings:
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specific comorbid conditions
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medical optimization
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interventional optimization.
Specific comorbid conditions
Cardiovascular disease: patients with active cardiac conditions should be referred to cardiology services for medical and/or interventional optimization prior to elective surgery (see below). Generally, heart failure is known to carry the highest risk of adverse perioperative outcome in this setting. Optimization of patients with new or unstable heart failure should be done in conjunction with a cardiologist. Treatment with angiotensin-converting enzyme inhibitors, β-blockers, aldosterone antagonists, diuretics and cardiac resynchronization may be indicated.
Respiratory disease: preoperative interventions which have been demonstrated to reduce risk are:
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smoking cessation for more than 4–6 weeks prior to surgery (see above)
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bronchodilator optimization in individuals with reversible airways disease
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eradication of active infection
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steroid treatment – reduces perioperative bronchospasm in individuals with reactive airways
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physiotherapy – instruction in postoperative breathing exercises.
It may be necessary to admit some individuals with severe pre-existing respiratory disease to hospital 24–48 hours in advance of surgery to achieve optimization.
Renal disease: in the face of a limited evidence base, the following may need to be carefully considered where renal dysfunction is identified prior to vascular surgery:
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overnight intravenous crystalloid hydration prior to aortic surgery
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renal assessment and consideration of renal artery stenting where significant renal artery stenosis is identified as a cause of renal dysfunction
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preoperative dialysis – an appropriate time interval should be allowed for patients to undergo dialysis prior to vascular surgery
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post-dialysis bloods should be available prior to subsequent surgery.
Diabetes: patients with glycated haemoglobin (HbA 1c ) over 69 mmol/mol (8.5%) and those with hypoglycaemia unawareness should be referred to the diabetes specialist team to optimize control. Specific recommendations for preoperative pharmacological management are beyond the scope of this article and are covered elsewhere. The following are recommended:
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a written perioperative plan should be developed for each patient before admission based on local guidelines
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where possible, diabetic patients should be placed first on an operating list to minimize fasting and allow resumption of normal diet and diabetic medications
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when the anticipated period of starvation is more than one missed meal, most patients will require a variable-rate insulin infusion preoperatively
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patients with poor diabetic control or those undergoing major surgery may benefit from overnight preoperative admission.
Anaemia: even mild preoperative anaemia is associated with increased risk of morbidity and mortality following major surgery. Investigation of the cause and correction prior to surgery is therefore essential. Such treatment may include iron or erythropoietin, for example. A comprehensive overview of this important area can be found elsewhere. In the face of a lack definitive evidence, consensus opinion recommends establishing preoperative haemoglobin levels within the normal range prior to elective surgery: more than 12 g/dl for females and more than 13 g/dl for males.
Medical optimization
It is essential that all comorbid medical diseases be optimized in advance of surgery to reduce perioperative risks. This constitutes ‘medical optimization’ and encompasses disease processes such as cardiac disease, diabetes, chronic respiratory disease and renal dysfunction. Specialist referral or advice may be required pre-operatively to achieve this goal. In conjunction with the assessment of specific medical conditions, there is now evidence that a comprehensive geriatric assessment (CGA) is beneficial to patients undergoing vascular surgery. The CGA is a method that also includes the assessment and evaluation of psychological, social and functional issues including the evaluation of frailty. The CGA provides individualized care plans which incorporate the most appropriate investigation, treatments and rehabilitation programmes. Evidence of reductions in length of hospital stay, complication rates and better outcomes (at discharge) from hospital have been widely reported. Elderly vascular patients undergoing urgent intervention for critical limb ischaemia and/or major lower limb amputation appear to benefit the most from specialist input from geriatricians. It is important that vascular anaesthetists and vascular surgeons create local pathways that can allow individuals to have access to CGA where appropriate.
Specific recommendations for preoperative medication are provided in Table 1 .
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