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Anesth Analg 1999;89:1366
© 1999 International Anesthesia Research Society

CARDIOVASCULAR ANESTHESIA

A Comparison of Two Techniques for Cervical Plexus Blockade: Evaluation of Efficacy and Systemic Toxicity

J. C. Merle, MD*, J. X. Mazoit, MD{ddagger}, P. Desgranges, MD{dagger}, K. Abhay, MD*, S. Rezaiguia, MD*, G. Dhonneur, MD*, and P. Duvaldestin, MD*

*Service d’Anesthésie-Réanimation et {dagger}Service de Chirurgie Vasculaire, Henri Mondor Hospital, Creteil; and {ddagger}Laboratoire d’Anesthésie, Université de Paris-Sud, Faculté de Médecine, Le Kremlin Bicetre, France

Address correspondence and reprint requests to Dr. J. C. Merle, Service d’Anesthesie-Réanimation, Hôpital Henri Mondor, 51 avenue du Maréchal de Lattre de Tassigny, F 94010 Creteil Cedex, France.


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 References
 
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 µg/mL versus 1.5 µg/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.


   Introduction
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 Abstract
 Introduction
Methods
 Results
 Discussion
 References
 
Regional anesthesia for carotid endarterectomy (CEA) allows clinical monitoring of cerebral function in the conscious patient throughout the procedure (1–4). Two techniques can be used: cervical plexus block (CPB) or cervical epidural anesthesia. The use of CPB may be more appropriate for surgery of the lateral aspect of the neck compared with cervical epidural anesthesia, based on the rare but potentially dramatic complications associated with the latter (2,5). However, CPB requires experience and is not without pitfalls, such as unsatisfactory anesthesia and complications (7,8).1 The most common complication is systemic local anesthetic toxicity, caused by either intravascular injection or vascular absorption in this highly vascularized region (9,10).

In the present study, we compared the classical method, which requires three injections after identification of the second, third, and fourth cervical roots (classical CPB) with single injection of the cervical plexus at the level of C4–C5, as identified by appropriate nerve stimulation using an interscalene approach (interscalene CPB). Comparative evaluation was based on the quality of anesthesia and pharmacokinetics.


   Methods
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 Abstract
 Introduction
 Methods
Results
 Discussion
 References
 
After we received approval by the ethical committee and informed consent, 23 patients, ASA grades II and III, scheduled for elective CEA under regional anesthesia were randomized to receive a classical CPB or an interscalene CPB. Patients undergoing external carotid reconstruction alone were excluded. All patients were operated on by two senior vascular surgeons. Before surgery, the options and risks of both regional and general anesthesia were discussed with each patient. The choice of regional versus general anesthesia was based on the preoperative assessment of neurological risk. Patients at risk, including those with clinical signs of a previous stroke, evidence of prior cerebral infarction on cranial tomography, or complete carotid occlusion, were scheduled for regional anesthesia, except when it was felt that they would not be able to cooperate during surgery.

All patients were premedicated with hydroxyzine (1 mg/kg) and/or flunitrazepam (1 mg). Each patient was supine with the head turned slightly away from the side to be blocked. For the classical CPB group, the technique consisted of a deep black and a superficial block. The deep CPB was performed as follows (11): three needles were inserted onto the transverse process of C2, C3, and C4. Six to eight milliliters of 0.5% bupivacaine was injected via each needle. The cervical superficial plexus block consisted of infiltration at the midpoint of the sternomastoid muscle with 20 mL of 2% lidocaine. The duration of injection of bupivacaine and lidocaine was approximately 60 s.

Interscalene CPB was performed using a short bevel needle (Stimuplex cannulae; Braun, Melsungen, Germany) for plexus anesthesia connected to a nerve stimulator (Stimuplex DIG, Braun). The needle was inserted in the interscalene groove at the level of the upper margin of the thyroid cartilage (Level C4–C5) and was directed caudally and medially until an elevation and internal rotation of the scapula was elicited by the nerve stimulator. This muscle-evoked response corresponded to that of the levator muscle of the scapula (Fig. 1). The tip of the needle was considered correctly positioned when a current intensity of <0.5 mA elicited a muscle response. Forty milliliters of an equal mixture of 0.5% bupivacaine and of 2% lidocaine was injected over 2 min while digital pressure was applied below the needle.



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  		Figure 1. Movement of the scapula elicited by stimulation of the cervical plexus.

 
The surgical technique was also standardized. The arteriotomy of the internal carotid was performed beyond the plaque, and patch angioplasty was limited to small-diameter internal carotid arteries. Neurological changes included evidence of paresis, aphasia, and/or a change in the level of consciousness. Intraluminal shunts were inserted only if the neurological status worsened.

The duration of the surgical procedure was recorded. The anesthetist managing the patient during the intraoperative and postoperative period was not aware of the local anesthetic technique used. Continuous electrocardiogram, pulse oximetry, and invasive arterial (radial artery) blood pressure monitoring were recorded. The adequacy of cerebral perfusion was assessed clinically based on the neurological condition of the patient. The mean arterial blood pressure was maintained at or just slightly above the preoperative value.

Pain was assessed using a 0–100 verbal rating scale, where 0 represented no pain and 100 the worst pain imaginable during the initiation of the CPB and at five points during the surgery: skin incision, placement of retractors, carotid clamping, carotid unclamping, and skin closure. Additional requirements for IV analgesia (bolus of 50 µg of fentanyl) or infiltration of lidocaine 1% by the surgeon were recorded.

Arterial blood samples were collected before and at 3, 5, 8, 10, 15, 25, 40, and 60 min after the first injection of local anesthetic in each group. Plasma bupivacaine and lidocaine were measured with high-performance liquid chromatography, with a modification of the technique of Chen et al. (12). The recovery of extraction averaged (±SD) 94.5% ± 3.5% for both lidocaine and bupivacaine. The limit of detection was 0.025 µM (5–10 ng/mL) for lidocaine and bupivacaine. The intraday coefficient of variation was less than 6% at 200 ng/mL and less than 10% at 20 ng/mL.

Pharmacokinetic variables included: peak serum concentration (Cmax) and the time to reach peak concentration (Tmax). Values, median (range), were compared between the two groups using the Mann-Whitney U-test. A P value < 0.05 was considered statistically significant.


   Results
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 Abstract
 Introduction
 Methods
 Results
Discussion
 References
 
There was no difference in demographic variables between the two groups. Eleven patients (8 men and 3 women) aged 72 (63–85) yr and weighing 74 (56–100) kg had an interscalene CPB, and 12 patients (10 men and 2 women) aged 72 (55–86) yr and weighing 75 (63–90) kg had a classical CPB. The duration of surgery was 95 (62–120) min in the interscalene CPB group and 94 (75–130) min in the classical CPB group. No serious adverse events were observed. None of the patients required conversion to general anesthesia. No signs of local anesthetic toxicity were observed in any of the patients.

The verbal rating scale scores of pain during the anesthetic procedure were significantly lower (P < 0.05) in the interscalene CPB (20 [0–50]) compared with the classical CPB (45 [0–90]) (Table 1), whereas it did not differ between the two groups during the different stages of surgery. Additional requirements for IV analgesia or local anesthetics are listed in Table 2. Both techniques required boluses of fentanyl during the surgical procedure, particularly during carotid artery dissection. The majority of the patients in each group requested additional lidocaine locally during the placement of the retractor or the carotid artery dissection.


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  		Table 1. Verbal Rating Scale of Pain
 

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  		Table 2. Supplementary Analgesia
 
The Cmax of bupivacaine was significantly lower (P < 0.01) in the interscalene CPB than in the classical CPB (1.0 vs 1.5 µg/mL) (Table 3). The Cmax for lidocaine was similar in both groups. The Tmax of lidocaine and bupivacaine were significantly longer in the interscalene CPB than in the classical CPB (P < 0.05).


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  		Table 3. Time to Maximal Plasma Concentration (Tmax) and Peak Plasma Concentration (Cmax) of lidocaine and Bupivacaine
 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
References
 
Our study shows that the interscalene CPB is as effective as the classical CPB as a regional anesthetic technique for CEA and may be associated with lower systemic absorption of bupivacaine. CPB provides analgesia and allows direct monitoring of cerebral function during CEA (1–4). However, this technique is unfamiliar to many anesthetists (5) and, even in experienced hands, is associated with a high failure rate as a result of patient discomfort.1 According to our results, both block techniques required supplemental IV analgesia or local anesthetic infiltration, particularly during retractor placement and carotid artery dissection. During these phases of surgery, CPB provided insufficient anesthesia, probably because the innervation of the carotid artery originates from cranial nerves (13). Interscalene CPB with a single-injection technique was described by Winnie et al. (14) in 1975. To optimize this technique for anesthesia for CEA, Mehta and Juneja (15) used a single-injection technique guided with a nerve stimulator to elicit twitches of neck muscles and paresthesia over the shoulder and the upper arm. In our study, the identification of the cervical plexus was more precise, requiring movement of the scapula that corresponds to stimulation of the levator muscle of the scapula, which is innervated by branches of the third, fourth, and fifth cervical roots and which leaves the interscalene groove at the level of the upper margin of the thyroid cartilage (13). Nerve stimulation at this level provokes the elevation and internal rotation of the shoulder blade. Digital pressure below the injection site may help prevent caudad spread of the anesthetic. We considered the combination of a deep block and a superficial plexus block the technique of reference as it has been used by many anesthesiologists for CEA under regional anesthesia (3,4,7–9,16,17). However, in a recent study, it was shown that a superficial block alone was as successful as a deep CPB performed with a single injection for CEA (18).

We observed that the Cmax of bupivacaine was significantly lower in the interscalene CPB than the classical CPB. Moreover, the Tmax of lidocaine and bupivacaine is significantly slowed in the interscalene CPB group. Because systemic toxicity of local anesthetics depends on the Cmax and on the speed at which Cmax is reached, our results suggest that interscalene CPB is perhaps a safer procedure. In a previous study, the venous plasma concentrations of local anesthetics after interscalene block were measured (19). However, because large arteriovenous differences in the concentration of local anesthetics have been observed as a result of tissue uptake, the measurement of the arterial concentrations appears more reliable (20). We also chose to perform arterial sampling because the drug concentration in arterial blood peaks earlier and is more representative of toxicity in vital organs. Another difference from previous studies is that high-performance liquid chromatography was used instead of gas liquid chromatography, because in experienced hands, it is a simpler and more accurate method. Although there are limitations caused by the differences in methodology among the studies, the Cmax and Tmax we reported are not different from results found in previous studies. Tissot et al. (17) reported values of the Tmax of lidocaine and bupivacaine as early as 11 minutes after initiation of the CPB. The rapid vascular absorption of local anesthetics after CPB we reported may be caused by the multiple-injection site technique (17).

No adverse event related to systemic resorption was observed, despite the high Cmax values of lidocaine and bupivacaine observed in some patients. Seven patients (four in the classical CPB group and three in the interscalene CPB) had a Cmax of lidocaine >6 µg/mL, and two patients in the classical CPB group had a Cmax of bupivacaine >2.5 µg/mL, concentrations which are considered toxic for both local anesthetics alone. Some authors believe that the risk of side effects can be amplified, as a mixture of local anesthetics may accumulate to a toxic level (21). The absence of systemic toxicity is not surprising because of the small patient population studied and the low incidence of this complication (16). In addition, most studies refer to venous blood concentration, which may lead to an overestimation of the toxic threshold (15).

We demonstrated that CPB for CEA can be performed with a single injection into the cervical plexus after its localization with a nerve stimulator. This technique is simple, although it does not appear to be superior to the classical method in terms of quality of anesthesia during surgery. However, systemic absorption of local anesthetic appears to be of less concern with the single-injection than with the multiple-injection technique.


   Footnotes
 
1 Bause GS. Intertubular cervical plexus block: a new anesthetic technique [abstract]. Anesth Analg 1987;66:S8. Back


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 

  1. Lee KS, Davis CH, McWhorter JM. Low morbidity and mortality of carotid endarterectomy performed with regional anesthesia. J Neurosurg 1988;69:483–7.[Web of Science][Medline]
  2. Bonnet F, Derosier JP, Pluskwa E, et al. Cervical epidural anaesthesia for carotid artery surgery. Can J Anaesth 1990;37:353–8.[Web of Science][Medline]
  3. Davies MJ, Murrell GC, Cronin KD, et al. Carotid endarterectomy under cervical plexus block: a prospective clinical audit. Anaesth Intens Care 1990;18:219–23.[Web of Science][Medline]
  4. Fiorani P, Sbarigia E, Speziale F, et al. General anaesthesia versus cervical plexus block and perioperative complications in carotid artery surgery. Eur J Vasc Endovasc Surg 1997;13:37–42.[Web of Science][Medline]
  5. Murie JA, Morris PJ. Carotid endarterectomy in Great Britain and Ireland. Br J Surg 1986;73:867–70.[Web of Science][Medline]
  6. Deleted in proof.
  7. Castresana MR, Masters RD, Castresana EJ, et al. Incidence and clinical significance of hemidiaphragmatic paresis in patients undergoing carotid endarterectomy during cervical plexus block anesthesia. Anesth 1994;6:21–3.
  8. Szocik JF, Kellogg W, Wakefield TW. Temporary facial nerve palsy during carotid endarterectomy under local anesthesia. Anesth Analg 1995;81:1106–7.[Web of Science][Medline]
  9. Dawson AR, Dysart RH, Amerena JV, et al. Arterial lignocaine concentrations following cervical plexus blockade for carotid endarterectomy. Anaesth Intensive Care 1991;19:197–200.[Web of Science][Medline]
  10. Brown DL, Ransom DM, Hall JA, et al. Regional anesthesia and local anesthetic-induced systemic toxicity: seizure frequency and accompanying cardiovascular changes. Anesth Analg 1995;81:321–8.[Abstract]
  11. Murphy TM. Somatic blockade of head and neck. In: Cousins MJ, Bridenbaugh PO, eds. Neural blockade. Philadelphia:JB Lippincott, 1988:533–58.
  12. Chen Y, Potter JM, Ravenscroft PJ. A quick, sensitive high-performance liquid chromatography assay for monoethylglycinexylidide and lignocaine in serum/plasma using solid-phase extraction. Ther Drug Monit 1992;14:317–21.[Web of Science][Medline]
  13. Rouvière H, Delmas A. Nerfs de la tête et du cou. In: Anatomie humaine. Tome I. Paris:Masson, 1997:249–339.
  14. Winnie AP, Ramamurthy S, Durrani Z, Radonjic R. Interscalene cervical plexus block: a single-injection technique. Anesth Analg 1975;54:370–3.[Abstract/Free Full Text]
  15. Mehta Y, Juneja R. Regional analgesia for carotid artery endarterectomy by Winnie’s single-injection technique using a nerve detector. Anesth 1992;6:772–3.
  16. Bouttier S, Andreassian B, Leseche G, et al. Chirurgie carotidienne sous bloc pexique cervical. Chirurgie 1994;119:305–14.
  17. Tissot S, Frering B, Gagnieu MC, et al. Plasma concentrations of lidocaine and bupivacaine after cervical plexus block for carotid surgery. Anesth Analg 1997;84:1377–9.[Web of Science][Medline]
  18. Stoneham MD, Doyle AR, Knighton JD, et al. Prospective, randomized comparison of deep or superficial cervical plexus block for carotid endarterectomy surgery. Anesthesiology 1998;89:907–12.[Web of Science][Medline]
  19. Wildsmith JMW, Tucker GT, Cooper S, et al. Plasma concentrations of local anaesthetics after interscalene brachial plexus block. Br J Anaesth 1977;49:461–6.[Abstract/Free Full Text]
  20. Rosenberg PH. Toxicity of local anaesthetics. In: Löfström JB, Sjöstrand U, eds. Monographs in anaesthesiology: local anaesthesia and regional blockade. Amsterdam:Elsevier Ed, 1988:57–75.
  21. Mets B, Janick PK, James MF. Lidocaine and bupivacaine cardiorespiratory toxicity additive: study in rats. Anesth Analg 1992;75:611–4.[Abstract/Free Full Text]
Accepted for publication July 21, 1999.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins and Stanford University Libraries' HighWire Press®. Copyright 1999 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press