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Contents:
The ACC/AHA 2011 Guideline for the Management of Patients With Peripheral Arterial Disease provide an overview of the patient population and their likely co-morbidities and therapy. The VascularWeb provides info and diagrams about most vascular procedures. The 2007 ACC/AHA Guidelines for Perioperative Cardiovascular Evaluation for Non-Cardiac Surgery is very detailed (multiple pages). See also this textbook's section on pre-operative assessment in our chapter on cardiac surgery, or our more general chapter on preoperative assessment. This site provides a concise visual overview of carotid endarterectomy. Here are the full US 2011 guidelines. The patient may seek advice about carotid stenting, a therapy that, despite initially mixed results avoids the risk of surgery. The CREST study found both to be similar in outcome. This detailed 2011 meta analysis from JAMA Neurology showed surgery to be associated with better results, but not by much. Carotid endarterectomy may be performed under local or general anaesthesia. Overall perioperative stroke rates average 3% either way. One in three occur in the immediate peri-operative period and the remainder over the next three months. Several multi-centre studies have confirmed that carotid endarterectomy improves outcome for most patients with significant lesions (even if asymptomatic). Local anaesthesia typically involves appropriate montoring, cervical plexus block, additional infiltration of local by the surgeon and a degree of sedation. The patient should be conscious at the time of carotid clamping to monitor neurological function. Approximately one in ten patients will require a shunt. The block must be good if the surgeon is to get to the top of a high lesion, so not all patients can be done under local. Outcome (stroke, myocardial infarction) is similar to general anaesthesia, and recovery is prompt. General anaesthesia can provide a higher degree of control over conditions influencing intra-operative cerebral ischaemia. Cerebral metabolic rate is reduced by general anaesthetic agents and mild hypothermia. The patients CO2 level can be controlled and the airway secured. "Cerebral Protection" with thiopentone or proprofol (in doses sufficient to induce EEG burst suppression) can be given. Systemic blood pressure can be kept high with vasopressors without the risk of cardiac ischaemia that may occur in an anxious patient having a local anaesthetic. Attention to these factors, including avoidance of vasodilator anaesthetic agents and use of cerebral protection, can reduce the need to shunt to almost zero and give the surgeon plenty of time to get the best possible surgical result, but only if the anaesthetist monitors and maintains cerebral bloodflow during the crossclamp period. Continuous stump pressure monitoring, EEG monitoring, and trans-cranial Doppler can be used to monitor adequacy of perfusion but strokes can still occur. TCD can monitor embolic frequency on de-clamping and thereby individualise anti-thrombotic therapy. It seems clear that systemic blood pressure should be maintained at relatively high levels during the cross-clamp period, especially if signs of cerebral ischaemia occur on clamping. It's likely that vasodilator effects of high CO2 levels and some anaesthetic agents may induce steal and therefore are probably undesirable components of a general anaesthetic or a sedation technique. It's important to recognise that most strokes are surgical in origin (intimal flaps, thrombus formation, embolus, etc. Perhaps only one in ten, regardless of technique, are due to a lack of bloodflow to the brain during the cross-clamp period. There is no substitute for extensive experience with a particular technique. Outcome depends more on how well things are done rather than the technique used. Three month stroke rates vary from 1% to 7% from institution to instituion. Patients who experience cerebral ischaemia while clamped are at much higher risk (up to 10x) of perioperative stroke because of the patient's dependence on that vessel for adequate cerebral blood flow. This high-risk group probably require more aggressive perioperative antithrombotic therapy and may benefit from extremely meticulous surgery. High-risk patients cannot be predicted except by test occlusion at angiography. General information from Wikipedia and VascularWeb. Greater detail from a 2006 article by Upchurch in American Family Physician and the SVS 2009 guidelines. Notes on aetiology, and from VascularWeb. Information for patients about surgical or endovascular repair. Acute presentations with leaking or rupture need resuscitation and urgent or emergency general anaesthesia. Management of significant blood loss, maintenance of circulating volume, cardiac output, body temperature, avoidance of cagulopathy etc is be the priority. See Peter McLaughlin's notes from AnaesthesiaWA. Elective presentations are usually dealt with by endoluminal techniques, the anaesthetic requirements for which are modest unless things go bad. Elective open repairs require general anaesthesia but whether or not an epidural should be used as well is an interesting question.. Providing adequate post-operative pain managment for open cases is difficult, especially if surgery involves the thorax. Epidurals can improve post-operative analgesia but carry the risk of epidural haematoma and masking of spinal cord damage. Post-operative renal impairment is a significant issue, especially with lesions above the renal arteries, and acute surgical, spinal cord, cerebral and cardiac complications are not uncommon. Preoperative evaluation of these patients is an important part of the anesthesiologic management. Thoracic / Thoracoabdominal Aortic Aneurysm Spinal cord damage and renal impairment are special concerns, and obviously one-lung anaesthsia must be provided. Here's a well-written case report from BHJ. Aneurysms of the Ascending Aorta and Aortic Arch The anesthetic management of patients undergoing open repair of the ascending aorta is complex, essentially a variant of open heart surgery requiring one-lung anaesthesia, cardiopulmonary bypass etc (see the cardiac chapter of The Virtual Anesthesia Textbook). Cerebral hypoperfusion / embolus and paraplegia due to cord ischaemia are very significant concerns. Here are some notes on aortic dissection. Surgical and other issues may be addressed in The Heart Surgery Forum. Several techniques are used to protect the brain during circulatory arrest and profound hypothermia. Information on neurosurgical vascular surgery may be available from the neurosurgery anaesthesia chapter. Postoperative pain is a very significant issue especially after open thoracic or abdominal procedures. All analgesic techniques are associated with some risk. Epidurals provide more effective post-operative pain relief than intravenous opioids for most patients but carry serious risks of epidural haematoma - especially in association with anti-coagulation. Combination analgesic approaches (eg combining local/regional anaesthetic, opiod, anti-inflammatory, paracetamol (acetaminophen), alpha-2 agonist, and tramadol) may be better than monotherapy. Use of COX-2 inhibitors requires caution as some, notably rofecoxib, can increase the risk of post-operative thrombosis. Acutely high blood pressures may rupture graft suture lines, and low blood pressure (actually poor perfusion, not exactly the same thing) may contribute to thrombosis. Blood pressure should be maintained within apropriate limits. Patients are at risk of cardiac events, renal failure, respiratory failure and so on. Adequate post-operative monitoring, often in high-dependency units or ICU environments should be available if needed. For general information about pain relief - see the Virtual Anesthesia Textbook chapter on pain.. William Maples, PhD, of West Georgia College has put up a Web Site to serve as a Support Page for people whose lives have been affected by aneurysmal diseases. Find this site at the State University of West Georgia.
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