Plasma Concentrations of Lidocaine and Bupivacaine After Cervical Plexus Block for Carotid Surgery:

[Regional anesthesia for carotid surgery : An overview of anatomy, techniques and their clinical relevance]

BACKGROUND

Perioperative care for patients undergoing carotid endarterectomy (CEA) often presents a challenge to the anesthesia provider, as this patient group commonly suffers from a wide range of comorbidities. Although clinical trials could not demonstrate a significant benefit associated with regional anesthesia for outcomes such as insult, cardiac infarction or mortality, many authors concur that regional anesthetic techniques might be preferential in specific patient populations for this type of surgery.

OBJECTIVES

This article aims to present an overview of the currently used techniques for regional anesthesia in CEA, as well as discussing their influence on the perioperative outcome.

MATERIALS AND METHODS

After performing an extensive search of medical databases (Pubmed/Medline) the authors present a narrative analysis and interpretation of recent literature.

RESULTS

Currently there is a clear trend towards ultrasound guided regional anesthesia and away from classic landmark based techniques. The literature seems to support the notion that superior and intermediate cervical blocks are safer and less invasive than deep blocks.

CONCLUSIONS

With regional anesthetic techniques evolving to be more and more complex, the use of ultrasound is becoming increasingly indispensable in the operating theatre. For anesthesiologists with sufficient training and a profound knowledge of the respective anatomy, regional anesthesia seems to be a veritable alternative to general anesthesia for CEA.

Ropivacaine 0.375% vs. 0.75% with prilocaine for intermediate cervical plexus block for carotid endarterectomy: A randomised trial

BACKGROUND

Carotid endarterectomy is widely performed under regional anaesthesia. Ultrasound guidance is increasingly used in many regional anaesthetic procedures to improve safety and efficacy, and because it can reduce the amount of local anaesthetic required. Despite this, an ideal approach and dosing regimen for cervical plexus block remain elusive.

OBJECTIVE

The aim of this study was to compare two different concentrations of ropivacaine in terms of analgesic adequacy, haemodynamic effects and plasma concentration using an ultrasound-guided triple approach for intermediate cervical plexus blockade.

DESIGN

A randomised, placebo-controlled, blinded study.

SETTING

University Clinic Salzburg, Department of Anaesthesiology, Perioperative Medicine and Intensive Care, Paracelsus Medical University, Salzburg, Austria, from 16 November 2012 to 17 September 2013.

PATIENTS

Forty-six patients prospectively randomised to receive ultrasound-guided intermediate cervical block with either 20 ml ropivacaine 0.75% or 20 ml ropivacaine 0.375% each with 20 ml prilocaine 1%.

INTERVENTION

After subcutaneous infiltration, blocks were performed using ultrasound-guided infiltration below the sternocleidomastoid muscle, and ultrasound-guided infiltration of the carotid sheath. Ropivacaine and prilocaine plasma concentrations were measured at intervals.

MAIN OUTCOME

The primary study endpoint was the volume of supplementary lidocaine 1% required to achieve adequate surgical anaesthesia. Perioperative haemodynamic variables and pain scores were recorded.

RESULTS

There was no statistical difference in the volume of supplementary lidocaine given: 5.0 (±3.63) ml in the ropivacaine 0.375% group and 5.17 (±2.76) ml in the ropivacaine 0.75% group (P = 0.846). Pain scores were similarly low across both groups. Measured concentrations of ropivacaine and prilocaine did not reach toxic levels in either group. Levels of ropivacaine were approximately two-fold higher in the 0.75% group [mean area under the curve (AUC) 10 531.11 (±2912.84) vs. 5264.34 ng (±1594.69), P < 0.0001]. Perioperative cardiovascular stability was excellent in both groups. There were no serious block-related complications.

CONCLUSION

An ultrasound-guided intermediate block provides adequate anaesthesia for carotid thrombendarterectomy with a little need for supplementary local anaesthetic. Use of 0.375% ropivacaine provided similarly effective analgesia as 0.75%, but resulted in significantly lower plasma concentrations.

TRIAL REGISTRATION

The study was registered at the European Clinical Trial Database (Eudra CT No.: 2012-002769) as well as at ClinicalTrials.gov (NCT01759940).

Preventive analgesia by local anesthetics: the reduction of postoperative pain by peripheral nerve blocks and intravenous drugs

The use of local anesthetics to reduce acute postoperative pain has a long history, but recent reports have not been systematically reviewed. In addition, the need to include only those clinical studies that meet minimum standards for randomization and blinding must be adhered to. In this review, we have applied stringent clinical study design standards to identify publications on the use of perioperative local anesthetics. We first examined several types of peripheral nerve blocks, covering a variety of surgical procedures, and second, we examined the effects of intentionally administered IV local anesthetic (lidocaine) for suppression of postoperative pain. Thirdly, we have examined publications in which vascular concentrations of local anesthetics were measured at different times after peripheral nerve block procedures, noting the incidence when those levels reached ones achieved during intentional IV administration. Importantly, the very large number of studies using neuraxial blockade techniques (epidural, spinal) has not been included in this review but will be dealt with separately in a later review. The overall results showed a strongly positive effect of local anesthetics, by either route, for suppressing postoperative pain scores and analgesic (opiate) consumption. In only a few situations were the effects equivocal. Enhanced effectiveness with the addition of adjuvants was not uniformly apparent. The differential benefits between drug delivery before, during, or immediately after a surgical procedure are not obvious, and a general conclusion is that the significant antihyperalgesic effects occur when the local anesthetic is present during the acute postoperative period, and its presence during surgery is not essential for this action.

Pharmacokinetics of levobupivacaine 0.5% after superficial or combined (deep and superficial) cervical plexus block in patients undergoing minimally invasive parathyroidectomy

STUDY OBJECTIVE

To evaluate the pharmacokinetic profile of 0.35 mL/kg of 0.5% levobupivacaine during superficial and combined (deep and superficial) cervical plexus block (CPB) in patients undergoing minimally invasive parathyroidectomy.

DESIGN

Prospective randomized study.

SETTING

Operating theater of a university hospital.

PATIENTS

12 ASA physical status II and III patients (11 women and 1 man), scheduled for minimally invasive parathyroidectomy.

INTERVENTIONS

Seven and 5 patients were randomly assigned to receive either superficial or combined CPB, respectively. The superficial CPB was performed with an injection of 0.35 mL/kg of 0.5% levobupivacaine subcutaneously along the posterior border of the sternocleidomastoid muscle and deeper on its medial surface. The combined CPB was initiated by the deep block at the C3 level vertebra by injecting 0.2 mL/kg of 0.5% levobupivacaine, followed by the superficial block with an injection of the remaining 0.15 mL/kg. After completion of the block, venous blood was sampled at the intervals of 5, 10, 15, 20, 30, 45, and 60 minutes.

MEASUREMENTS AND MAIN RESULTS

Venous plasma concentrations were measured using gas chromatography-mass spectroscopy. Mean +/- SD of maximal concentrations of levobupivacaine was 0.58 +/- 0.41 mg/L in group superficial and 0.52 +/- 0.28 mg/L in group combined (P = 0.71). The median (range) time required to reach the maximal concentrations was 30 minutes (20-30 min) in group superficial and 20 minutes (15-30 min) in group combined (P = 0.45). The areas under the drug concentration/time curve (AUC(10-60)) were also similar in both groups. No signs of central nervous system or cardiovascular toxicity or other untoward events were observed in any patient.

CONCLUSION

With the given dose regimen, levobupivacaine plasma concentrations were within safe ranges.

Superficial or deep cervical plexus block for carotid endarterectomy: a systematic review of complications †

Carotid endarterectomy is commonly conducted under regional (deep, superficial, intermediate, or combined) cervical plexus block, but it is not known if complication rates differ. We conducted a systematic review of published papers to assess the complication rate associated with superficial (or intermediate) and deep (or combined deep plus superficial/intermediate). The null hypothesis was that complication rates were equal. Complications of interest were: (1) serious complications related to the placement of block, (2) incidence of conversion to general anaesthesia, and (3) serious systemic complications of the surgical-anaesthetic process. We retrieved 69 papers describing a total of 7558 deep/combined blocks and 2533 superficial/intermediate blocks. Deep/combined block was associated with a higher serious complication rate related to the injecting needle when compared with the superficial/intermediate block (odds ratio 2.13, P = 0.006). The conversion rate to general anaesthesia was also higher with deep/combined block (odds ratio 5.15, P < 0.0001), but there was an equivalent incidence of other systemic serious complications (odds ratio 1.13, P = 0.273; NS). We conclude that superficial/intermediate block is safer than any method that employs a deep injection. The higher rate of conversion to general anaesthesia with the deep/combined block may have been influenced by the higher incidence of direct complications, but may also suggest that the superficial/combined block provides better analgesia during surgery.

Adjunctive pharmacologic use in carotid endarterectomy: a review

Although carotid endarterectomy (CEA) is now widely accepted as the surgical therapy for carotid stenosis, the role of and indications and evidence for many pharmacologic agents that are used adjunctively in the perioperative setting have not been conclusively established. Aspirin (acetylsalicylic acid) is the pharmaceutical agent that has been studied most extensively in conjunction with CEA; other than aspirin and dextran, the use of many agents before, during, and after CEA has not been standardized. Prospective randomized trials are still needed to demonstrate efficacy, predict outcome, and determine the optimal use of these medications in their adjunctive use during CEA to improve patient care and obtain optimal surgical outcomes.

The number of injections does not influence absorption of bupivacaine after cervical plexus block for carotid endarterectomy

STUDY OBJECTIVE

To investigate the efficacy and kinetics of bupivacaine when used for deep cervical plexus block (CPB), using either a single-injection or multiple-injections technique.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Operating room of a university hospital.

PATIENTS

Twenty-four adult patients (16 men, 8 women) scheduled for carotid endarterectomy.

INTERVENTIONS

Patients were randomly assigned to receive CPB either by a single injection or after 3 injections. Patients in the multiple-injections group received a total dose of 15 mL of 0.5% bupivacaine (5 mL each deposited at C2, C3, and C4 over 2 minutes). Patients in the single-injection group received a single 15-mL injection of 0.5% bupivacaine. After the deep CPB, a superficial CPB was performed with 20 mL of 0.5% bupivacaine in all patients.

MEASUREMENTS

An anesthesiologist and a surgeon graded the success of the block. Arterial plasma concentrations of bupivacaine were measured using liquid chromatography-mass spectroscopy.

MAIN RESULTS

No significant differences were seen between the 2 groups with respect to the mean peak concentration of bupivacaine (single injection 2314 +/- 1385 ng/mL vs multiple injections 2255 +/- 1105 ng/mL) or time to reach the maximal concentration (time to maximum concentration [single injection 12.1 +/- 7.2 minutes vs multiple injections 12.5 +/- 3.9 minutes]). Furthermore, there were no significant differences in mean block scores between the single-injection and the multiple-injections groups, evaluated either by the anesthesiologists or the surgeon.

CONCLUSIONS

The results of this study showed that the absorption of bupivacaine is independent of the number of injections after CPB, and that anesthesia for carotid endarterectomy may be accomplished successfully using either technique.

A comparison of ropivacaine and bupivacaine for cervical plexus block

We compared bupivacaine 0.5% and ropivacaine 0.75% for cervical plexus block (CB). Forty patients scheduled for carotid artery surgery were allocated randomly to undergo superficial and deep CB with 30 mL of one of the two anesthetic solutions. We evaluated the onset of anesthetic block; the requirement for supplementation during the surgery; the patients' satisfaction; postoperative pain on a visual analog scale at 1, 2, and 3 h; and the use of paracetamol as a rescue analgesic medication. Arterial blood was sampled immediately and 1, 3, 5, 10, 15, 30, 45, and 60 min after CB for measurements of bupivacaine or ropivacaine concentrations. Patients in both groups had equivalent onset of CB, local infiltration with lidocaine during surgery, and satisfaction scores. In the Bupivacaine group, visual analog scale scores were lower at 2 and 3 h, and the delay before paracetamol administration was prolonged. Observed peak concentrations were larger in the Ropivacaine group (4.25 [2.07-6.59 mg/L] vs 3.02 [0.98-5.82 mg/L]), but time to reach peak concentrations was comparable (5 [1-15 min] vs 5 [0-45 min] in the Ropivacaine and Bupivacaine groups, respectively). We conclude that ropivacaine has no advantage over bupivacaine for CB.

IMPLICATIONS

Compared with bupivacaine (150 mg), a larger dose of ropivacaine (225 mg) produces comparable features of cervical plexus block but less postoperative analgesia and larger plasma concentrations. There is no reason to favor ropivacaine in such a case.

A comparison of superficial versus combined (superficial and deep) cervical plexus block for carotid endarterectomy: a prospective, randomized study

Carotid endarterectomy may be performed by using cervical plexus blockade with local anesthetic supplementation by the surgeon during surgery. Most practitioners use either a superficial cervical plexus block or a combined (superficial and deep) block, but it is unclear which offers the best operative conditions or greatest patient satisfaction. We compared the two techniques in patients undergoing carotid endarterectomy. Forty patients undergoing carotid endarterectomy were randomized to receive either a superficial or a combined cervical plexus block. Bupivacaine 0.375% to a total dose of 1.4 mg/kg was used. The main outcome measure was the amount of supplemental lidocaine 1% used by the surgeon. Subsidiary outcome measures were postoperative pain score, sedative and analgesic requirements before and during surgery, and postoperative analgesic requirements. Median supplemental lidocaine requirements were 100 mg (range 30-180 mg) in the superficial block group and 115 mg (range 30-250 mg) in the combined block group. These differences were not statistically significant (Mann-Whitney U-test). There was no significant difference in the number of patients needing postoperative analgesia between the groups (11 of 20 in the deep block group versus 8 of 20 in the superficial block group) in the 24 h after surgery. The median time to first analgesia in the superficial block group was 150 min, more than in the combined block group (median time 45 min) but this difference, although large, was not statistically significant (Mann-Whitney U-test). We found no significant differences between the anesthetic techniques studied. All patients reported satisfaction with the techniques.

Cervical plexus anesthesia for carotid endarterectomy: comparison of ropivacaine and mepivacaine

PURPOSE

To evaluate the effectiveness of cervical plexus block performed with ropivacaine 0.75% or 1%, or mepivacaine 2%.

METHODS

In a prospective, randomized, double-blind study, 60 patients received deep cervical plexus block with 0.2 ml x kg(-1) divided among C2-C4 injections using ropivacaine 0.75% and 1% or mepivacaine 2%. A blinded observer recorded loss of pin-prick sensation every minute in the C2-C4 dermatomes until readiness for surgery. Then, a superficial cervical block was performed with 0.15 ml x kg(-1) lidocaine 1%. The need for intraoperative supplemental analgesia and degree of pain and time of first postoperative pain medication were also recorded.

RESULTS

General anesthesia was not required to complete surgery in any case. No differences in the need for intraoperative supplemental analgesia was observed (7, 6, and 9 patients with ropivacaine 0.75% and 1% or mepivacaine 2%, respectively). Readiness to surgery required 15 (10-25) min with ropivacaine 0.75%, 18 (8-20) min with ropivacaine 1%, and 15 (5-20) min with mepivacaine 2% (P = NS); while patients asked for first postoperative pain medication after 10 (4-13) hr and 9 (6.5 - 11) hr with ropivacaine 0.75% and 1% compared with 5 (0-8) hr with mepivacaine 2% (P<0.05).

CONCLUSION

Ropivacaine 0.75% or 1% are appropriate choices when performing cervical plexus anesthesia for carotid endarterectomy, providing nerve block characteristics similar to those of mepivacaine 2%, but with the advantage of longer postoperative pain relief.

A comparison of two techniques for cervical plexus blockade: evaluation of efficacy and systemic toxicity

We compared two techniques of cervical plexus blockade (CPB) for carotid endarterectomy. Cervical plexus nerve block was performed with a combination of bupivacaine and lidocaine, with injections at the C2-C3, C3-C4, and C4-C5 transverse processes in 11 patients (classical CPB) or with a single injection after localization of the cervical plexus with a nerve stimulator in 12 patients (interscalene CPB). Pain scores were obtained during block placement and at predetermined phases of the operation. Arterial blood was sampled before and 3, 5, 8, 10, 15, 25, 40, and 60 min after CPB for measurement of bupivacaine and lidocaine concentrations. Interscalene CPB was less painful than classical CPB. The techniques appeared equally effective. Patients in both groups required equivalent supplementation with IV fentanyl and additional local infiltration with lidocaine during the most painful stages of surgery. The maximal concentration of bupivacaine was lower in interscalene CPB compared with classical CPB (1.0 microg/mL versus 1.5 microg/mL, P < 0.01). The time required to reach the maximal concentration of bupivacaine was 15 (10-40) min in interscalene CPB and 10 (5-17) min in classical CPB (P < 0.05). Lidocaine maximal concentration was similar in both groups, however the time required to reach the maximal concentration was longer (P < 0.05) in interscalene CPB (15 [10-60] min) than in classical CPB (10 [8-20] min). We conclude that the interscalene CPB is as effective as the classical CPB as a regional technique for carotid endarterectomy and may be associated with a lower systemic absorption of bupivacaine.

IMPLICATIONS

Cervical plexus blockade for carotid endarterectomy can be effectively performed with a single injection after localization of the cervical plexus with a nerve stimulator. This technique is simple and was associated with less systemic absorption of local anesthetic than the multiple-injection technique.