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High volume and low concentration of anaesthetic solution in the perivascular interscalene sheath determines qualityof block and incidence of complications

Pippa, P.*; Cuomo, P.; Panchetti, A.*; Scarchini, M.; Poggi, G.*; D'Arienzo, M.

European Journal of Anaesthesiology (EJA): October 2006 - Volume 23 - Issue 10 - p 855–860
doi: 10.1017/S0265021506001074
Original Article

Background and objective: In the perivascular sheath of the brachial plexus, the volume of anaesthetic solution determines the quality of anaesthetic cover. Fibrous septa may divide the perivascular space into compartments, leading to inadequate diffusion of the anaesthetic solution. The aim of our study was to obtain good anaesthesia and less complications using high volume of low concentration anaesthetic solution, overcoming the obstacle of the septa with a double approach to the scalene sheath.

Methods: Sixty patients scheduled for shoulder capsuloplasty received both Winnie interscalene brachial plexus block and Pippa proximal cranial needle approach. The patients were randomly assigned to two groups. A constant dose of local anaesthetic was administered to each group: Group I (30 patients) received high volume (60 mL of anaesthetic solution) and Group II (30 patients) received low volume of solution (30 mL of anaesthetic solution). Sensory and motor block in the upper limb and complications were evaluated.

Results: In all the patients the quality of anaesthesia obtained at the surgical site was excellent. In Group I also the areas supplied by the medial cutaneous nerves of the arm and forearm, ulnar, median and radial nerves were blocked (P < 0.002). Complications were only observed in Group II and consisted of bradycardia and hypotension (66% of the patients) and phrenic nerve paresis (27% of the patients).

Conclusions: The lower concentration of the anaesthetic solution avoids complications while increased volume provides good analgesic cover. The combination of the Winnie interscalene plexus block and the Pippa proximal cranial needle approach should contribute to fill up the scalene sheath overcoming the septa obstacles.

*University of Florence, Department of Anaesthesiology, Florence, Italy

University of Florence, Department of Orthopaedics, Florence, Italy

Correspondence to: Pierluigi Cuomo, Department of Orthopaedics, University of Florence, Florence, Italy. E-mail: cuomo@virgilio.it

Accepted for publication 16 January 2006

First published online 11 July 2006

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Introduction

The brachial plexus block rationale is based on the existence of a well-defined fascia running from the cervical processes to the armpit and on the free diffusion of the injected anaesthetic solution along this fascia. The volume of the injected anaesthetic solution may determine the quality of the anaesthetic cover [1].

The aim of this study was to compare two groups of patients scheduled for shoulder capsuloplasty who underwent a Winnie interscalene brachial plexus block [2] followed by a Pippa proximal cranial needle approach [3]. The combination of two anaesthetic approaches [4–7] was employed to overcome the septa obstacles and to fill as much as possible of the interscalene sheath, independently from the quantity of the anaesthetic solution. The dose of anaesthetic employed was constant, while volume and concentration differed between the two groups in order to assess the effect of anaesthetic volume and concentration on the motor and sensory block and to see the effect of the anaesthetic solution on the sympathetic fibres.

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Methods

After local Ethics Committee approval 60 fully consented American Society of Anesthesiologists (ASA) physical status I–II patients, whose age ranged from 20 to 65 yr and weight from 50 to 80 kg (Table 1), received regional anaesthesia for shoulder capsuloplasty. A Winnie interscalene brachial plexus block was performed (Fig. 1) and followed by Pippa proximal cranial needle block (Fig. 2) and a constant dose of anaesthetic was administered: 300 mg of lidocaine and 75 mg of bupivacaine.

Table 1

Table 1

Figure 1.

Figure 1.

Figure 2.

Figure 2.

Patients were randomly assigned to two different groups of 30 patients according to the employed volume: Group I received 60 mL of anaesthetic solution made of equal parts of bupivacaine 0.25% (with 150 μg epinephrine, i.e. 2.5 μg mL−1) and lidocaine 1% while Group II received 30 mL of anaesthetic solution with equal parts of bupivacaine 0.50% (with 150 μg epinephrine, i.e. 5 μg mL−1) and lidocaine 2%. The volume of local anaesthetic administered was divided in equal parts in the two approaches (i.e. 30 mL in each approach in Group I and 15 mL in each approach in Group II).

The block was performed at least 30 min before surgery; 20 min before the block patients were given 10 mg of oral diazepam and 0.5 mg of intramuscular atropine. In each group the nerve block was performed with the aid of a nerve stimulator using a short bevelled, 5 cm, 22-G Teflon-coated stimulating needle (Stimuplex, B Braun Melsungen AG, Germany).

According to the Winnie technique [2] the needle was introduced in the caudal direction at the intersection point between the external jugular vein and the intercricothyroided line (Fig. 1). The Pippa proximal cranial needle block was then performed: the needle was introduced in a cranial direction from the midpoint between the clavicle bone insertion of the sternocleidomastoid muscle and the external jugular vein towards Chaissignac's tubercle with a 30° angle upon the upper border of the clavicle (Fig. 2).

The nerve stimulator was set at 2 Hz, while the intensity of the stimulating current was initially set to deliver 1 mA and then gradually decreased to <0.5 mA.

Flexion or extension of the wrist, elbow or fingers confirmed that the needle was close to the brachial plexus nerve fibres.

The patients were evaluated by an assessor, blinded to the procedure employed, 10, 20 and 30 min after injection of the anaesthetic solution.

Motor function was tested according to the modified Bromage scale [8].

Sensory block was tested by pinprick response in the following eight areas:

  1. Lateral region of the neck, innervated by the cutaneous nerve of the neck (C2–C4).
  2. Lateral region of the arm, innervated by the superior cutaneous nerve of the arm, branch of the axillary nerve (C5–C6).
  3. Lateral region of the forearm, innervated by the lateral cutaneous nerve of the forearm, branch of the musculocutaneous nerve (C5–C6–C7).
  4. Medial side of the forearm, innervated by medial cutaneous nerve of the forearm (C8–T1).
  5. Medial aspect of the arm, innervated by the medial cutaneous nerve of the arm (T1) and the intercostobrachialis nerve (T1–T2).
  6. Dorsal areas of the hand in the region supplied by the radial nerve (C5, C6, C7).
  7. Palmar areas of the hand in the region supplied by the median nerve (C6, C7, C8, T1).
  8. Ulnar territory of the hand (C7, C8, T1).

The degree of analgesia was graded as follows:

0: pinprick clearly felt as painful, evoking a visible reaction;

1: pinprick attenuated, non-visible reaction to the stimulus;

2: pinprick felt only as a tactile, not painful stimulus;

3: pinprick not felt at all.

The onset of the surgical anaesthesia was defined as the loss of pinprick sensation at the skin dermatomes involved in the surgical field (from C4 to C7) with the inability to elevate the operated limb from the bed [9].

Anaesthesia was clinically classified as:

Excellent: patient appeared completely satisfied and comfortable with the procedure.

Good: analgesia was complete, but the patient complained about the position of the arm and/or the length of the procedure necessitating intraoperative intravenous (i.v.) medication.

Insufficient: analgesia was incomplete and additional nerve block and/or i.v. analgesic (fentanyl) was required.

Failure : analgesia was insufficient and general anaesthesia had to be performed.

Ultrasonography was chosen as the method to demonstrate diaphragmatic movement as it reliably shows paradoxical movement of the diaphragm in the event of paresis [10].

Before and 10 min after the block all the patients underwent ultrasonography to assess diaphragmatic movement on deep inspiration. The ultrasound probe was placed over one of the lower intercostals spaces in the mid-axillary line in order to visualize the dome of the diaphragm on the same side as the block. Diaphragmatic paresis was defined as a 50% reduction of the diaphragmatic excursion [11].

Statistical differences between the two groups were assessed according to the Fisher's exact test. Level of significance was set at P < 0.05.

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Results

The level of analgesia obtained in each group is shown in Table 2. In Group I the postaxial regions of the medial arm and forearm, supplied by the medial cutaneous arm, forearm and ulnar nerve, were blocked. The areas supplied by median and radial nerves were blocked as well.

Table 2

Table 2

Clinical outcome of anaesthesia is shown in Table 3.

Table 3

Table 3

Grade II motor block was achieved on average in 25 (range 20–29) and 15 (range 11–19) min in Groups I and II, respectively (P < 0.05).

Minor complications, due to the distribution of the anaesthetic solution to nearby structures, occurred only in Group II and included: dysphonia due to laryngeal nerve involvement (20 patients) and Horner's syndrome (18 patients). All these complications spontaneously resolved within 40 min.

Major complications were observed only in Group II and included bradycardia (heart rate (HR) <45 min−1) and hypotension (systolic arterial pressure <70 mmHg) in the sitting position [12] and phrenic nerve paresis [13] in 66%, 66% and 27% of the patients, respectively.

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Discussion

The main finding of this investigation was that the quality of the anaesthetic block and the incidence of complications strictly depends on the volume and the concentration of the anaesthetic solution. The quality of anaesthesia obtained at the surgical site was excellent in all the patients. The two groups showed a different distribution of anaesthesia in the areas not interested by the surgical procedure. In Group II insufficient anaesthesia was regularly obtained in the areas supplied by the medial cutaneous arm and forearm, ulnar, median and radial nerves.

Several anatomic and clinical studies [14,15] demonstrated the existence of fibrous septa within the sheath of the brachial plexus dividing it into compartments, which may lead to inadequate diffusion of the anaesthetic solution [16]. Furthermore, the author has clinically demonstrated a preferential distribution of the anaesthetic solution injected into the perivascular axillary sheath [17], which could be explained by the trapping of the anaesthetic solution in separate compartments, and its spread along a preferential route in relation to the direction of the needle. These observations were the rationale for a double approach which allowed a combined craniocaudal (Winnie technique) and caudocranial (Pippa's technique) distribution of the anaesthetic solution (Fig. 3). Routine use of nerve stimulators and the peculiar inclination of short bevelled needles in both approaches preserves the safety of the technique. The dose of the anaesthetic injected (300 mg lidocaine +75 mg bupivacaine) was constant, while volume varied between the two groups. The onset of surgical anaesthesia required 25 ± 5 min in Group I and 20 ± 5 min in Group II. It is known that the latency of the anaesthetic block related to the concentration, the quicker minimum effective concentration will be reached inside the nerve fibre, so reducing latency time [18]. As reported also by other authors [15], increased analgesia was observed in patients who were given higher volumes (60 mL).

Figure 3.

Figure 3.

In Group II, phrenic nerve paresis was observed in 27% of cases. Phrenic nerve paresis has been reported as possible complication of supraclavicular block with varying incidence from 28% to 80%. Urmey and colleagues [13] reported ipsilateral hemidiaphragmatic paresis in 100% of patients during interscalene block and argued that phrenic paresis should be considered as an expected side-effect rather than a complication of the block [19]. In our series and with the same investigational technique only 27% of the patients in Group II were found to have a diaphragmatic paresis. Only two patients experienced respiratory symptoms (dyspnea) for <10 min; none of them showed respiratory distress and in all the cases SPO2 remained unchanged. The fact that no phrenic paresis has been recorded in Group I can be ascribed to the lower concentration of anaesthetic employed.

Several authors [12,20–22] have investigated bradycardia and hypotension in upper limb surgery in the sitting position. The nearest hypothesis includes a combination of (a) peripheral vasodilatation due to the block exaggerated by the sitting position, (b) increased heart contractility secondary to absorbed epinephrine from the block, (c) vigorous contraction of an empty ventricle and (d) vagal dominance [23–25]. In our series 66% of the patients in Group II showed hypotension and bradycardia with pre-syncopal symptoms. In all the patients the symptoms resolved with elevation of the legs, i.v. fluid infusion, i.v. administration of sympathomimetic and anticholinergic drugs such as atropine or with a combination of all three measures.

No major complications occurred in Group I, likely because the reduction of the concentration of anaesthetic solution causes less involvement of the sympathetic fibres and phrenic nerve.

In conclusion, the quality of anaesthesia at the surgical site obtained in both groups was excellent. In non-surgical areas different levels of anaesthesia were achieved in the two groups: patients in Group I had a wider anaesthesia due to the larger diffusion of the solution within the brachial plexus. Major complications were observed only in those patients who received high concentration and small volume of local anaesthetic. High concentration of local anaesthetic on brachial plexus motor and sensory fibres affects block intensity and ensure an excellent anaesthetic cover; on the other hand major clinical complications due to sympathetic fibre block may occur and require sudden intervention. High volumes and small concentration of local anaesthetic in the brachial plexus avoid major complications such as phrenic nerve involvement and vagal reflexes.

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Keywords:

ANAESTHESIA CONDUCTION, axillary block, brachial plexus block; ANAESTHETICS LOCAL, lidocaine, bupivacaine; PREOPERATIVE CARE

© 2006 European Society of Anaesthesiology