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毓恬图曹
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1 2015 / 05 / 05 R2 林書瑜 VS 鍾雍泰醫師

2 INTRODUCTION This review will focus on the whole process of regional anaesthesia for CEA, including: Preoperative assessment and preparation Regional anaesthetic techniques The choice of sedative and local anaesthetic (LA) drugs The available evidence comparing regional and general anaesthetic (GA) techniques Perioperative arterial pressure management The treatment options for patients developing neurological deficits after carotid cross-clamping.

3 INTRODUCTION We searched the electronic databases; PubMed and National Library of Medicine from 1999 to 2013 We looked for articles, reviews, and case reports that described new techniques or developments in regional anaesthesia. We also searched the reference list of relevant articles for further references. For this article, we did not consider animal studies.

4 PREOPERATIVE ASSESSMENT Preoperative hypertension is a risk factor for postoperative stroke and death Specific figures for preoperative arterial pressure targets have not been defined from controlled trials, but a sensible target is that systolic and diastolic arterial pressures are 180 and 100 mm Hg, respectively.

5 PREOPERATIVE ASSESSMENT The 2012 National Guidelines for Stroke: Carotid intervention for recently symptomatic severe carotid stenosis should be regarded as an emergency procedure in patients who are neurologically stable, and should ideally be performed within 48 h of a transient ischaemic attack or minor stroke and definitely within 1 week, as the benefits of carotid surgery decrease rapidly after this. => less time for preoperative patient preparation, including arterial pressure control.

6 PREOPERATIVE ASSESSMENT The patient s neurological status should be assessed before operation, and neurological deficit(s) documented. Anti-hypertensive medications should usually be continued except for angiotensinconverting enzyme inhibitors and angiotensin II receptor antagonists Reductions in arterial pressure should be avoided in patients with neurological symptoms.

7 PREOPERATIVE ASSESSMENT The American College of Cardiology recommendations for perioperative β-block include continuation if already taking but not to start unless specifically indicated. Statins should be continued as there is evidence Statins should be continued as there is evidence of up to a 3% reduction in the incidence of stroke after CEA

8 PREOPERATIVE ASSESSMENT Antiplatelet therapy has a theoretical, therapeutic benefit both at the thrombogenic endarterectomy site and in the coronary circulation in high-risk vascular patients. Aspirin is recommended for all vascular patients in the perioperative period, but the situation regarding clopidogrel is less clear. There is certainly evidence in patients undergoing CEA of the benefits of dual antiplatelet therapy (aspirin combinedwith low-dose clopidogrel) to reduce the rate of micro-embolization after operation. A Cochrane review of randomized trials found significant protection against stroke in patients receiving clopidogrel.

9 PREOPERATIVE ASSESSMENT Neither the incidence of clinically important neck haematoma nor the morbidity rate from haemorrhagic complications increases in patients undergoing CEA taking clopidogrel with or without aspirin. Surgery may take longer; however, careful consideration should be given to the risks and benefits of performing regional anaesthesia in these patients.

10 REGIONAL ANAESTHETIC TECHNIQUES Key anatomy The cervical plexus is formed by the ventral rami of the first four cervical nerves (C1 4). The nerves pass laterally along the corresponding transverse process immediately posterior to the vertebral artery and vein. The deep branches are entirely motor and supply the neck muscles. The superficial branches are sensory and supply the skin and subcutaneous tissues of the neck and posterior aspect of the head.

12 REGIONAL ANAESTHETIC TECHNIQUES Cervical epidural anaesthesia An epidural catheter is sited at C6 7 and a dilute anaesthetic solution such as bupivacaine 0.25%injected. Significant side-effects : hypotension, bradycardia, and respiratory impairment Other complications include conversion to GA, dural tap, epidural haematoma, and direct spinal cord damage. Single injection posterior cervical paravertebral block at the C4 level using a nerve stimulator is another technique of blocking C2 4 dermatomes, which may reduce the risk of accidental vascular injury or injection

13 Superficial cervical plexus block

14 Ultrasound-guided superficial cervical plexus block a linear streak of hypoechoic nodules, which have a honeycomb appearance

15 Ultrasound-guided superficial cervical plexus block

16 Ultrasound-guided superficial cervical plexus block High concentrations of LA agent are not required since the superficial cervical plexus comprises purely sensory nerves An oft-cited disadvantage of superficial compared with deep block is said to be that it does not provide neck muscle relaxation, although this has not been shown to be important clinically.

17 Ultrasound-guided intermediate cervical plexus block Investing fascia

18 Ultrasound-guided intermediate cervical plexus block a depth of 15 mm may be a perception of loss of resistance

19 Deep cervical plexus block The cervical transverse processes are palpated behind sternocleidomastoid. a 50 mm, 25 G block needle is introduced aiming slightly caudally and posteriorly until the cervical transverse process is encountered, usually 1 2 cm under the skin.

20 Ultrasound-guided deep cervical plexus block

21 Ultrasound-guided deep cervical plexus block

22 REGIONAL ANAESTHETIC TECHNIQUES The deep block has been implicated with a higher risk of accidental involvement of deep structures, such as the carotid and vertebral arteries, the phrenic nerve, dura mater, and the sympathetic trunk Nerve stimulators may be used to identify the deep cervical plexus By identifying diaphragmatic muscle response, a nerve stimulator may avoid administration of the LA directly onto the phrenic nerve, thereby avoiding phrenic nerve palsy Continuous deep block

23 REGIONAL ANAESTHETIC TECHNIQUES Pharmacology of cervical plexus blocks Most LA agents have been used for cervical plexus block => Ropivacaine, levobupivacaine, bupivacaine, mepivacaine

24 REGIONAL ANAESTHETIC TECHNIQUES Pharmacology of cervical plexus blocks

25 REGIONAL ANAESTHETIC TECHNIQUES Assessment of the block The loss of pinprick sensation in the distribution of the C2 4 dermatomes => Extend over the shoulder and down to the clavicle (C4 dermatome), and up to and including the neck up to the earlobe (C2).

26 INTRAOPERATIVE MANAGEMENT Patient comfort fluids should be kept to a minimum to avoid the need to void intraoperatively Oxygen administration Respiratory monitoring Cardiac monitoring

27 CAROTID CROSS-CLAMPING Carotid cross-clamping May be up to or even longer than 1 hr Cerebral perfusion Augmentation of arterial pressure to 20% above baseline has been recently shown to reduce early postoperative cognitive dysfunction => however, precipitate myocardial ischaemia?!

28 REGIONAL ANAESTHETIC TECHNIQUES Under GA, many surgeons choose to shunt all patients regardless of neurological state.

29 REGIONAL ANAESTHETIC TECHNIQUES In awake patients, shunting is usually only performed if a neurological deficit develops after cross clamping Treatment options: selective augmentation of the arterial pressure to normal, or up to 20% above normal The administration of high concentrations of oxygen has been shown clinically to reverse the developing neurological deficit and to increase the ipsilateral cerebral oxygenation measured by cerebral oximetry during carotid cross-clamping

30 REGIONAL ANAESTHETIC TECHNIQUES An awake patient is the most reliable method for assessing neurology during carotid crossclamping. loss or altered consciousness, confusion, agitation, dysphasia, seizures, an contralateral motor weakness counting tests; questions requiring cognition to answer correctly (e.g. what day of the week is it?). A squeaky toy is used by some for assessment of motor power. Cardiac symptoms

31 REGIONAL ANAESTHETIC TECHNIQUES BIS monitoring during awake CEA has not been shown to be reliable in detecting cerebral ischaemia. Transcranial Doppler monitoring (TCD) Middle cerebral artery blood flow May be used to detect particulate and gaseous embolism intraoperatively

32 SEDATION Supplement the regional block during awake CEA Opioids (remifentanil, fentanyl) α-2 agonists (clonidine, dexmeditomidine) Propofol butyrophenones (droperidol, haloperidol). The ideal sedative agent should reduce anxiety without causing respiratory depression, airway compromise, or haemodynamic instability, while the depth of sedation is altered rapidly Propofol target-controlled infusion

33 SEDATION α-2 2 agonists are ideal drugs as in addition to sedation, they reduce analgesic requirements and are hypotensive agents with cardioprotective properties. Remifentanil produces a rapidly reversible and predictable sedo-analgesia while at the same time reducing LA supplementation Sedation must be minimal during cross-clamping to allow frequent neurological assessment.

34 HAEMODYNAMIC MANAGEMENT Patients who require perioperative pharmacological treatment for hypotension and hypertension have> 1 yr morbidity and mortality. Under GA: patients tend to be relatively hypotensive intraoperatively, commonly requiring vasopressor support After operation, GA patients tend to be hypertensive patients under regional anaesthesia are often relatively hypertensive intraoperatively, particularly during the cross-clamp period, but then relatively hypotensive after operation.

35 HAEMODYNAMIC MANAGEMENT Arterial pressure during carotid cross-clamping should not be allowed to decrease below the patient s baseline and should be kept at or up to 20% above this. However, after carotid artery unclamping, hypertension should be avoided to reduce the likelihood of hyperperfusion syndrome Metaraminol, ephedrine, and phenylephrine Hydralazine, glyceryl trinitrate (GTN), calcium channel antagonists, β-blockers (labetalol, esmolol, atenolol), and α- 2 agonists, such as clonidine, may be used to treat perioperative hypertension

36 COMPLICATIONS OF REGIONAL ANAESTHESIA Seizures LA overdose, direct injection of LA into the artery or cerebral ischaemia hyperperfusion syndrome

37 COMPLICATIONS OF REGIONAL ANAESTHESIA Cervical block complications More complications have been reported in the literature from patients undergoing deep and combined deep and superficial cervical plexus block compared with superficial block alone. The conversion rate to GA was also higher with patients receiving the deep/combined block

38 COMPLICATIONS OF REGIONAL ANAESTHESIA Cardiovascular complications Myocardial infarction is a major cause of perioperative and long-term mortality after CEA no difference between the GA and LA groups!! Accidental surgical manipulation of the vagus nerve, which lies within the carotid sheath, can lead to profound haemodynamic disturbance, including nausea and vomiting, bradycardia, hypotension, and even cardiovascular collapse.

39 COMPLICATIONS OF REGIONAL ANAESTHESIA Airway complications Respiratory distress, secondary to diaphragmatic or vocal cord paralysis, may occur Phrenic nerve block is common after deep cervical block occurring in up to half of the patients, although this is commonly tolerated without major sequelae Preoperative examination of vocal cords in patients at risk of contralateral nerve damage has been recommended Airway oedema Local trauma and interference with venous and lymphatic drainage. Haematoma formation

40 COMPLICATIONS OF REGIONAL ANAESTHESIA Intra-arterial injectionof LA Subarachnoid injection(resulting in brainstem anaesthesia) Anaesthesia of the recurrent laryngeal, vagus, hypoglossal, and phrenic nerve have all been described with deep cervical plexus block. Conversion to GA is rarely required. An incidence of 2.5% is quoted and may result from inadequate anaesthesia, patient agitation, poor patient compliance, severe respiratory compromise, or accidental intravascular injection

41 COMPLICATIONS OF REGIONAL ANAESTHESIA Nerve injuries The marginal mandibular branch of the facial, laryngeal, accessory, hypoglossal, the sympathetic chain (Horner s syndrome), and the radial nerve. Most cranial nerve injuries probably result from stretching, retraction, clamping, or imprudent use of diathermy, and resolve within 4 months. Dexamethasone has been shown to be effective at decreasing the incidence of temporary post-cea cranial nerve dysfunction

42 REGIONAL ANAESTHESIA VS GA GA: Neurological protection afforded by thiopental and volatile anaesthetic agents Absolute perioperative control of ventilation (allowing control of arterial carbon dioxide concentration and its effects on the cerebral vasculature)

43 REGIONAL ANAESTHESIA VS GA Regional anaesthesia: Easy assessment of neurological status during carotid cross-clamping Immediate postoperative neurological assessment Greater cardiovascular stability Better postoperative analgesia Shorter hospital stay

44 REGIONAL ANAESTHESIA VS GA The GALA trial Over 8 yr, 3526 patients were recruited and randomized to receive GA or regional anaesthesia for CEA. A primary outcome (myocardial infarction, stroke, or death within 30 days of surgery) occurred in 4.8% patients assigned to GA and 4.5% of those assigned to LA The GALA collaborators published a study showing that patients receiving GA had higher jugular venous concentrations of a marker of cerebral ischaemia (neuronal-specific enolase) compared with those patients receiving LA

45 REGIONAL ANAESTHESIA VS GA One possible explanation for the equivocal results ofgala is that the choice of anaesthetic technique used is less important than the vascular team looking after the patient. => 默契良好的團隊合作最重要!!

46 CONCLUSIONS Regional anesthesia has NOT been shown to be associated with better outcome than GA, but Haemodynamic stability The ease of neurological monitoring Shorter hospital stay Future challenge: Optimizing arterial pressure control Developing clinical protocols to avoid perioperative complications

醫學新知 (I) 35 11.74 mm Hg 2. 50% 3. SYMPLICITY HTN-III study 26% 4. 5. SYMPLICITY HTN-I SYMPLICITY HTN-II SYMPLICITY HTN-III 6 A controlled trial of

醫學新知 (I) 35 11.74 mm Hg 2. 50% 3. SYMPLICITY HTN-III study 26% 4. 5. SYMPLICITY HTN-I SYMPLICITY HTN-II SYMPLICITY HTN-III 6 A controlled trial of 34 醫學新知 (I) 針對頑固性高血壓之腎動脈交感神經阻斷術控制研究編譯 : 王宇澄中國醫藥大學附設醫院心臟內科 2:1 6 24 70% 535 14.13±23.93 mm Hg 11.74±25.94 mm Hg ( p