Abstract
There are multiple types of procedure for vascular disease on the extremities, the majority of which are for the treatment of peripheral arterial disease (PAD). PAD is a common condition affecting 20% of people over the age of 60. Interventional treatment can be vascular, endovascular or combined (‘hybrid’) procedures by vascular surgeons and interventional radiologists.
PAD has risk factors in common with other atherosclerotic diseases which are often present, even if the patient is asymptomatic. Significant smoking histories are also common. Consequently, patients with PAD are a high-risk anaesthetic cohort. Comprehensive pre-operative assessment and investigation of the cardio-respiratory systems are essential to guide peri-operative planning. Multiple risk assessment tools are available to facilitate peri-operative decision making and risk-benefit discussions with patients.
The aim of intra-operative management is cardiovascular stability with proactive anticipation of events including haemorrhage and clamp release. Post-operatively regional anaesthesia is strongly advised particularly for patients undergoing amputation. Post-operative cardiac investigations may also be indicated.
Thoracic outlet syndrome and AV fistula formations are two specific clinical scenarios also covered in this topic.
After reading this article, you should be able to:
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recognize that patients with peripheral arterial disease (PAD) are associated with high anaesthetic risk
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understand advanced cardiac risk assessment in relation to peripheral vascular surgery
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appreciates the additional perioperative measures for hybrid vascular/endovascular procedures
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understand the aims of safe intra-operative care in patients at high risk of adverse cardiac and respiratory events
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recognize the importance of optimizing post-operative management in PAD patients
Vascular surgery on the extremities covers a large range of procedures from emergency revascularizations due to trauma to elective varicose vein surgery. The focus of this article will be on patients having interventions for the treatment of peripheral arterial disease (PAD). Prospective research on this group of patients is sparse.
Definitions and epidemiology
PAD is common, with a prevalence of approximately 20% in those over 60 years. Only a small proportion of these will be symptomatic. Men are almost twice as likely to have symptoms as women.
Symptomatic peripheral limb ischaemia can be divided into:
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Intermittent claudication
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Chronic limb-threatening ischaemia (CLTI) – chronic vascular insufficiency that includes rest pain, with or without tissue loss (ulcers) or infection. The spectrum of this includes critical limb ischaemia (CLI) where there is imminent risk of limb loss.
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Acute limb ischaemia (ALI) – a sudden onset (<2 weeks) decrease in perfusion with threat of limb loss.
The prevalence of CLTI is approximately 0.4% and there are 1.5 cases of ALI per 10,000 people per year.
CLTI is associated with frailty and poor survival rates with a 5-year mortality of 50%, amongst the highest 5-year mortality for any chronic disease.
Risk factors
Peripheral artery disease is, by definition, atherosclerotic in nature and the risk factors are in common with other atheromatous disease:
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advancing age
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smoking
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hypertension
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chronic kidney disease (both a cause and effect)
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diabetes mellitus
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hypercholesterolaemia
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hyperhomocysteinaemia.
It is strongly associated with coronary and cerebrovascular disease.
Assessment of PAD is done using a mixture of clinical assessment, radiological imaging (typically CT angiography) and the ankle brachial pressure index (ABPI) ( Table 1 ). The lower extremity calcium score (LECS) is a novel measurement to predict risk of amputation whose use may increase over time.
| Ankle:Brachial Pressure index (ABPI) ratio | Grade |
|---|---|
| <0.5 | Severe arterial disease |
| 0.5–0.8 | Arterial disease or mixed arteriovenous disease |
| 0.8–1.3 | Normal |
| >1.3 | Suggestive of non-compressible vessels likely due to severe arterial calcification |
Types of surgical procedure
There are multiple types of intervention for treating PAD including vascular surgery, interventional radiology (IR) and ‘hybrid’ procedures that include both. Commonly vascular surgeons are experienced in using IR techniques without a radiologist to assess inflow, patency and runoff as part of their own procedures.
Common vascular surgical techniques include:
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endarterectomy
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bypass (vein or artificial graft)
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amputations
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aneurysm repair
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embolectomy.
Interventional radiology techniques include:
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angioplasty/Stenting
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embolectomy
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fistula formations.
Pre-operative assessment
Most procedures for PAD take place electively but there is a significant volume of emergency work for CLI. Most amputations are performed as emergencies. The urgency of the surgery defines the appropriate level of pre-operative investigation and optimization.
History and examination
Given the risk factors outlined above, thorough pre-operative assessment is essential for all patients undergoing surgery for peripheral arterial disease. Meticulous attention should be paid to the cardiovascular and respiratory systems ( Box 1 ).
| Respiratory | Cardiovascular |
|---|---|
|
|
| Interventions, medications and investigations (including timeframes) should be included for all the above | |
All patients should be asked if they take anticoagulants, patients are usually prescribed clopidogrel for secondary prevention in PAD. They may however be taking alternative anticoagulants for other comorbidities. A bleeding history (easy bruising, slow to stop bleeding minor injuries etc.) should also be taken at this point. It is more useful than laboratory assessment of coagulation and may identify clopidogrel hyper-responders.
The anaesthetic history should include a functional assessment, including exercise tolerance and status with both personal (pADL) and domestic (dADL) activities of daily living. Functional assessment can represent a challenge in patients with PAD, as the disease itself is often very restrictive due to exertional leg pain, preventing any regular stress to the cardiorespiratory system.
Investigation of patients presenting with critical limb ischaemia who have no cardiac symptoms has previously found 69% had coronary artery stenosis (43% severe lesion specific) on CT angiography. In the absence of functional testing, it is advisable to take a cautious approach and view the patient’s cardiorespiratory reserve as being the Metabolic Equivalents (METs) described (as limited by their PAD symptoms) rather than assuming a larger, unexplored, reserve.
Investigations
Routine bloods including full blood count, urea and electrolytes, liver function tests and coagulation should be performed.
Baseline SpO 2 in health is essential. Other respiratory function testing is not routine. Guidance indicates to ‘consider’ an arterial blood gas (ABG) or pulmonary function tests in patients American Society of Anesthesiologists (ASA) 3 and above undergoing intermediate to high-risk surgery. Pulmonary function tests have no proven utility in predicting post-operative pulmonary complications and their use should be restricted to those where a new diagnosis of significant respiratory disease is suspected based on history, examination and oxygen saturations.
An ECG is mandatory pre-operatively for all patients and further cardiac investigations are recommended for the most vascular patients based on European Society of Cardiology guidelines ( Box 2 ). Pre-operative N-terminal pro-B-type-natriuretic peptide (NT -proBNP) should be used as a screening tool in those either over 65 or with a cardiac history. An echocardiogram is also indicated with elevated levels (e.g. >400 ng/litre), non-elevated levels would be reassuring that heart failure is unlikely to be present.
| Recommendation | Evidence grade |
|---|---|
| In all patients scheduled for non-cardiac surgery (NCS) an accurate history and examination are recommended | I |
| Pre-operative ECG is recommended for patients who have risk factors and are scheduled for intermediate or high-risk surgery. | I |
| In patients aged 45–65 years without signs, symptoms, or history of CVD, ECG and biomarkers should be considered before high risk NCS | IIa |
| Trans-thoracic echocardiography is recommended in patients with poor functional capacity and/or high NT-ProBNP/BNP, or if murmurs are detected before high-risk NCS, in order to undertake risk reduction strategies. | I |
| Stress imaging should be considered before high-risk NCS in asymptomatic patients with poor functional capacity and previous PCI or CABG. | IIa |
| In patients who have known CVD, CV risk factors (including age ≥65 years), or symptoms or signs suggestive of CVD it is recommended to measure hs-cTnT or hs-cTn I before intermediate and high risk NCS and at 24 hours and 48 hours afterwards. | I |
Cardiopulmonary exercise testing (CPET)
Surgery for PAD is classified as high risk. Long complex procedures (e.g. aorto-bifemoral bypass) may meet criteria for functional capacity assessment using CPET. Practically however, its implementation is limited in PAD patients due to leg pain when using a standard cycle ergometer. CPET using an arm ergometer if available, may yield useful measurements including VO 2 max, anaerobic threshold and VE/VCO 2 .
Myocardial perfusion scans
In the general population, myocardial perfusion scans are recommended in intermediate to high-risk patients with limited exercise tolerance whose symptoms are suggestive of severe coronary artery disease. They have a strong negative predictive value but a weak positive predictive one. ,
In vascular patients however, 6.4% patients undergoing infra-inguinal bypass were found to have had a major cardiac event or death despite negative stress testing. Myocardial perfusion imaging may add no predictive value over the Revised Cardiac Risk Index.
Risk assessment tools
Patients with PAD are at high risk for Major Adverse Cardiac Events (MACE) and post-operative pulmonary complications. This should be discussed explicitly with them in the pre-operative setting, preferably not on the day of surgery. Various validated risk tools can be used to provide approximate figures for risk, but none carry strong recommendations for their use over others ( Box 3 ):
| Lee’s Revised Cardiac Risk Index (RCRI) – a six-component risk assessment for cardiovascular events in non-cardiac surgery |
| Link: https://www.mdcalc.com/calc/1739/revised-cardiac-risk-index-pre-operative-risk |
| VISION peri-operative risk scoring – Adds NT-proBNP levels to the RCRI for more accurate prediction of perioperative cardiac damage, MI and death. Validated on >27,000 patients undergoing non-cardiac surgery. |
| https://qxmd.com/calculate/calculator_783/vision-perioperative-risk-using-nt-probnp |
| The ACS NSQUIP surgical risk calculator – uses data from the American College of Surgery (4.3 million operations) to predict a wide range of complications including mortality, post-operative infections and discharge to dependent care. |
| https://riskcalculator.facs.org/RiskCalculator/ |
| Surgical outcome risk tool (SORT) – derived from a prospective observational study in the UK, Australia and New Zealand to predict death within 30 days. |
| http://www.sortsurgery.com/ |
| ARISCAT score for postoperative pulmonary complications – Gives a low/medium/high risk level for development of post-operative pulmonary complications including respiratory failure, infection, atelectasis and pleural effusion. |
| https://www.mdcalc.com/calc/10022/ariscat-score-postoperative-pulmonary-complications |
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