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Tags: vascular

Peripheral vascular disease

Symptomatic peripheral limb ischaemia can be divided into:

Assessment

Open lower limb revascularization and amputations are considered ‘high risk’ surgery

high risk of MACE & PRAE: risk assessment tools help with shared decision making

Pre-operative cessation of smoking is advised with a benefit shown if stopped greater than four weeks before surgery with a reduction in post-operative pulmonary complications

Statins should be commenced as these reduce the risk of post-operative cardiovascular complications and mortality

Anaesthesia for peripheral arterial disease can be performed via either general or regional anaesthesia

Retrospective analysis has suggested that post-operative mortality and complication rates are 50% lower in those undergoing neuraxial or regional anaesthesia compared to general

Patient selection and education are important when regional anaesthesia is considered.
Revascularization procedures can be prolonged in duration and the narrow beds used in hybrid theatres are uncomfortable. Use of distractions such as the radio or videos via portable electronic equipment may facilitate compliance. Most patients will require sedation for comfort purposes in procedures exceeding 2 hours in duration

Above knee amputations can be done under PNB although this is rarely routine practice and usually reserved for high-risk patients. Successful techniques for this include femoral, obturator and trans-gluteal sciatic nerve block. In addition, lateral cutaneous nerve of the thigh may need to be blocked. Most patients will also require sedation and supplementary analgesia.

In vitro studies have suggested that volatile anaesthetics may be protective of ischaemia–reperfusion injury of which this cohort is at particular risk, however this has not been conclusively reflected in peri-operative outcomes in terms of mortality or morbidity

If a hybrid procedure is taking place, arterial access should be discussed at the team brief as brachial access is sometimes planned and it is important that anaesthesia uses a different arm for monitoring.
If a patient has known CKD, this should also be highlighted as alternative, less nephrotoxic contrasts are available.

Occasionally an arterial trace may be damped with a lower systolic blood pressure than the non-invasive blood pressure (NIBP) in the contralateral limb due to undiagnosed subclavian stenosis

American Heart Association guidance offers more individualized advice stating blood pressure should be kept between 90% and 110% of baseline or 80–110% if the reference systolic blood pressure is >130mmhg

The target-controlled infusion (TCI) models used in TIVA have no compensatory mechanism for when large vessels are cross-clamped during surgery which can lead to excess dosing of propofol (due to reduction in size of all three spaces of the tri-compartmental model). This effect is less profound when a peripheral artery is clamped compared to the aorta as the volume out of circulation is smaller and the leg is likely to be inadequately perfused in the first place

It is recommended that processed electroencephalogram (EEG) with density spectral array as well as proprietary indices is used to enable titration of TCI to minimize burst suppression (potentially associated with worse outcomes). Processed EEG also facilitates reduced MAC values and burst suppression in inhalational anaesthesia.

Although most blood loss is insidious, bleeding can be brisk and extensive in all vascular procedures and expected blood loss is often high (>500 ml)

If vessels are significantly calcified it can be difficult to apply an effective cross-clamp, similarly in mid-foot amputations the presence of bones may make it difficult to apply direct compression of vessels

Conservative transfusion targets of 7 g/dL are rarely appropriate in this cohort owing to the prevalence of ischaemic heart disease and are not relevant in the event of acute surgical blood loss

Use of Tranexamic acid is contentious in vascular surgery as it is perceived to ↑ risk of graft thrombosis
A recent UK Royal Colleges Tranexamic Acid in Surgery Implementation group consensus statement based on multiple meta-analyses and systematic reviews (that included vascular patients) advises that it should be given routinely in procedures with a risk of blood loss >500 ml with no increased risk of thrombosis identified

Multimodal analgesia including local infiltration, paracetamol, and strong opioids (choice largely dependent on renal function) is routine and adjuncts such as magnesium, clonidine, and IV lignocaine can be used
NSAID: many pt C/I
Tramadol use can cause post-operative delirium and intra-operative ketamine has been associated with post-operative nightmares and hallucinations.

For amputations, even if GA is the preferred technique, regional anaesthesia is advisable for post-operative analgesia and shown to reduce early pain scores

If a patient has had a procedure a using epidural or combined spinal epidural technique, the removal of the epidural catheter should be planned carefully in relation to intra-operative heparin and post-operative DVT prophylaxis and recommencement of antiplatelets

Thoracic outlet syndrome
Thoracic outlet syndrome (TOS) describes compression of the neurovascular bundle of the subclavian artery, vein and brachial plexus as they pass the first rib and clavicle. Aetiology is due soft tissue or bony variations that can be congenital or acquired

Presentation can be varied, depending which structures are affected and can be single or multiple symptoms:

When surgery is indicated two approaches may be taken, supraclavicular or trans-axillary, requiring supine and lateral positioning respectively.
This is usually performed under GA. Measures for unanticipated major blood loss should be taken including large-bore vascular access and a crossmatch.
There is potential for breach of the pleura during this procedure and post-operative chest X-ray is indicated. Multi-modal analgesia is used, and a supplemental superficial cervical plexus block can be used for the supraclavicular approach

AVF surgery
The procedure itself is superficial and often amenable to local anaesthesia. If this is unacceptable for patient or procedural reasons general or regional anaesthesia can be performed. Brachial plexus blockade has been shown to be associated with a lower complication rate compared to general anaesthesia and the sympathetic blockade with associated vasodilation may allow for the preferred fistula formation over arterio-venous grafting.

References

Anaesthesia for Vascular Surgery on the Extremities - A&ICM