Axillary Plexus Research Articles

Local anaesthetic systemic toxicity

Access the CPD MCQs for this issue online here ### Key points Well-placed local anaesthetics (LAs) can yield great clinical benefits. But systemic toxicity related to their use can be devastating. The highly publicized case in 2004 of Mayra Cabrera, a theatre nurse who died shortly after delivery of her baby boy when her epidural infusion of bupivacaine was mistakenly connected to her i.v. line, reminds us to be vigilant and to learn from such rare events. While prevention is clearly the most important element in avoiding morbidity and mortality associated with local anaesthetic systemic toxicity (LAST), such cases still occur despite best practice. Knowing how to manage these uncommon events is vital. In this review, we cover LA toxicity, its incidence, clinical features, risk factors, prevention, and management and examine i.v. lipid emulsion (ILE) therapy in more detail. LAST has been recognized for more than a hundred years, but the precise incidence is currently unknown. In 1928, the American Medical Association reported 40 deaths attributable to LAs.1 Cocaine was responsible for half of these deaths, but procaine was also implicated. These findings prompted the search for less toxic agents. Lidocaine, first synthesized in 1944, was the first amide LA to be used clinically. However, in 1979, the potentially fatal toxicity of amide LAs was highlighted by Albright.2 More recently, studies from 1993 …

The effect of magnesium sulfate on motor and sensory axillary plexus blockade.

Background:Magnesium is a physiologic cation that blocks neuromuscular transmission and does not allow the nerve to be stimulated.Objectives:This study investigates the effect of adding magnesium sulfate to lidocaine to extend the duration of sensory and motor blocks of the axillary plexus in orthopedic surgeries of the upper extremities.Patients and Methods:This controlled randomized double-blind study was performed on patients who were candidates for orthopedic surgery of the upper extremities. A total of 60 patients between 18–60 years with ASA Class 1 or 2 participated in the study. One group received lidocaine (5 mg/kg) with magnesium sulfate 20% (3 mL) as the case group, while the second group received lidocaine (5 mg/kg) with normal saline (3 mL) as a placebo to block the axillary plexus using the trans-arterial technique. The duration of the sensory and motor block of the axillary plexus was monitored and evaluated using the pinprick and modified Bromage scale.Results:A total of 60 patients were included in the study with 30 patients having received lidocaine plus magnesium and the other 30 patients having received lidocaine plus normal saline. The mean sensory block duration in the case group was 248.83 ± 18.36 and in control group was 204.67 ± 22.62. The mean motor block duration in the case group was 207.0 ± 16.64 and in control group was 147.33 ± 21.52 (both P < 0.0001). The mean onset of sensory block in case group was 15.5 ± 3.79 and the onset block in control group was 10.33 ± 4.13 (P < 0.0001). The mean onset of motor block in case group was 20.66 ± 4.09 and the onset block in control group was 19.73 ± 26.18 (P < 0.848).Conclusions:The addition of magnesium sulfate to lidocaine increased the duration of motor and sensory axillary block in the upper extremities during surgeries when compared to the use of lidocaine alone.

Buprenorphine for postoperative analgesia: Axillary brachial plexus block versus intramuscular administration in a placebo-controlled trial

Background and Aims:Peripheral administration of opioids has been suggested for prolongation of regional analgesia. This prospective, randomized, double-blind placebo-controlled study was undertaken to compare the effect of regional (axillary brachial plexus block [ABPB]) versus intramuscular (IM) buprenorphine (2 μg/kg) in adults.Material and Methods:Seventy-five adults undergoing upper limb surgery received ABPB with local anaesthetic (15 ml 0.5% bupivacaine, 15 ml 2% lignocaine with adrenaline 1:200,000, 9 ml normal saline [NS]). In addition, regional group RB (n = 25) received buprenorphine 2 μg/kg in ABPB and 1 ml NS IM. Systemic Group SB (n = 25) received 1 ml NS in ABPB and buprenorphine 2 μg/kg IM. Group C (n = 25) received 1 ml NS in ABPB and IM. Onset, duration of sensory and motor block, hemodynamic parameters, sedation score, pain scores using visual analog scale, duration of postoperative analgesia, rescue analgesic (RA) requirement, adverse events, and patient satisfaction were noted.Results:Demographics, onset and duration of sensory, motor block were similar. RB group had longest duration of analgesia (20.61 ± 1.33 h) compared to SB (10.91 ± 0.90 h) and control group (5.86 ± 0.57 h) (P < 0.05 RB vs. SB/C and SB vs. C). RA requirement was highest in the control group and least in RB group (P = 0.000 RB vs. SB/C and SB vs. C). SB group had a maximum number of side effects (P = 0.041, SB vs. RB/C). Patient satisfaction was highest with group RB (P < 0.05 RB vs. SB/C, and P = 0.06 SB vs. C).Conclusion:Buprenorphine 2 μg/kg in axillary plexus block provides significantly prolonged analgesia with less RA requirement and greater patient satisfaction compared to IM administration. This is highly suggestive of action on peripheral opioid receptors.

Hyaluronidase revisited: A comparison of axillary plexus block with and without recombinant human hyaluronidase

Hyaluronidase revisited: A comparison of axillary plexus block with and without recombinant human hyaluronidase

MRI of axillary brachial plexus blocks: a randomised controlled study.

BACKGROUNDAxillary plexus blocks are usually guided by ultrasound, but alternative methods may be used when ultrasound equipment is lacking. For a nonultrasound-guided axillary block, the need for three injections has been questioned.OBJECTIVESCould differences in block success between single, double and triple deposits methods be explained by differences in local anaesthetic distribution as observed by MRI?DESIGNA blinded and randomised controlled study.SETTINGConducted at Oslo University Hospital, Rikshospitalet, Norway from 2009 to 2011.PATIENTSForty-five ASA 1 to 2 patients scheduled for surgery were randomised to three equally sized groups. All patients completed the study.INTERVENTIONSPatients in the single-deposit group had an injection through a catheter parallel to the median nerve. In the double-deposit group the patients received a transarterial block. In the triple-deposit group the injections of the two other groups were combined. Upon completion of local anaesthetic injection the patients were scanned by MRI, before clinical block assessment. The distribution of local anaesthetic was scored by its closeness to terminal nerves and cords of the brachial plexus, as seen by MRI. The clinical effect was scored by the degree of sensory block in terminal nerve innervation areas.MAIN OUTCOME MEASURESSensory block effect and MRI distribution pattern.RESULTSThe triple-deposit method had a higher success rate (100%) than the single-deposit method (67%) and the double-deposit method (67%) in blocking all cutaneous nerves distal to the elbow (P = 0.04). The patients in the triple-deposit group most often had the best MRI scores. For any nerve or cord, at least one of the single-deposit or double-deposit groups had a similarly high MRI score as the triple-deposit group.CONCLUSIONDistal to the elbow, the triple-deposit method had the highest sensory block success rate. This could be explained to some extent by analysis of the magnetic resonance images.TRIAL REGISTRATIONClinicalTrials.gov identifier: NCT01033006.

Guidance of axillary multiple injection technique for plexus anesthesia. Ultrasound versus nerve stimulation

Ultrasound guidance is still a young method in regional anesthesia when compared to nerve stimulation and only a few studies exist comparing these two techniques in an axillary multiple injection approach. This prospective, randomized, observer-blinded study compared an ultrasound-guided (SONO) quadruple injection axillary block (out of plane, perineural) with a nerve stimulation-guided (STIM) triple injection axillary block for upper limb surgery. A total of 60 patients were randomized to either the SONO (n = 30) or STIM (n = 30) group. For the block 40-50ml mepivacaine 1.5 % (plexus) and 5-10ml mepivacaine 0.5 % (subcutaneous in the medial skin of the arm) was used. Anesthesia time was recorded as the primary end point. After evaluation of block-related pain using a visual analog scale (VAS) a blinded observer tested sensory and motor function of the median nerve (MED), ulnar nerve (ULN), radial nerve (RAD), musculocutaneous nerve of the upper limb (MUC) and medial cutaneous nerve of the forearm (CAM) at defined times. The main outcome variable was onset time (defined loss of sensory/motor function). No differences were observed between the groups in terms of onset time (single nerves 10-20min, plexus 20-25min) and success rate (SONO 90 %, STIM 89 %). Patient satisfaction as measured by block-related pain score (VAS 2cm), complications (vascular puncture SONO 7 %, STIM 11 %; paresthesia SONO 21 %, STIM 22 %) and patient acceptance (SONO 92 %, STIM 91 %) showed no differences. Performance time was shorter in the SONO group (6.68 ± 1.72min vs. 8.05 ± 2.58, p = 0.02). Nerve stimulation-guided axillary plexus blocks performed by trained anesthesiologists may result in similar onset times and success rates compared to ultrasound-guided blocks.

Effective low dosage of mepivacaine in ultrasound-guided axillary nerve block: a double-blinded, randomized clinical trial of efficacy in patients undergoing distal upper extremity surgery

Study ObjectiveTo evaluate two low-dose volumes (20 mL or 30 mL) of 1.5% mepivacaine solution used for ultrasound-guided axillary blockade for outpatients undergoing distal upper limb surgery. DesignProspective, double-blinded randomized study. SettingOutpatient surgical setting of a university-affiliated hospital. Patients64 adult, ASA physical status 1, 2, and 3 patients, aged 28-46 years, scheduled for upper limb surgery. InterventionsPatients were randomized to two groups to receive either 20 mL of 1.5% mepivacaine solution (n=31) or 30 mL of 1.5% mepivacaine solution (n=33) for ultrasound-guided axillary plexus blockade. MeasurementsBlock duration, proportion of surgical and functional successful blocks, onset of sensory and motor blockade measured from 0 to 30 minutes following final needle extraction, total amount of preoperative sedative (midazolam), and intraoperative propofol administered were recorded. Main ResultsFollowing axillary plexus blockade, neither patient group showed any statistically significant difference in the percentage of functionally successful blockade (30 mL, 100%: 20 mL, 97%; P = 0.48), surgically successful blockade (30 mL, 100%; 20 mL, 94%; P = 0.23), cumulative sensory or motor blockade surgical time, block performance time, preoperative midazolam use, or intraoperative propofol use. ConclusionLow volumes (30 mL or 20 mL) of 1.5% mepivacaine provides satisfactory anesthesia for ambulatory distal upper limb surgery with no significant difference in clinical outcomes.

Our experiences with a single injection axillary block technique.

OBJECTIVE:Axillary plexus block is one of the widely used technique for upper extremity surgery. In this study, we retrospectively evaluated the single injection axillary plexus block technique we used in our rutine anesthesia practice, between August 2010-March 2011.METHODS:Medical records of ASA I-III, 40 17 female and 23 male patients who underwent elective single injection axillary block performed by neurostimulation technique in elective distal part of the arm, forearm and hand surgeries were evaluated, retrospectively. Axillary block was performed with a nerve stimulator, and a 22 G, 50 mm insolated needle. The needle was inserted immediately superior to axillary artery, advanced through the lateral border of the pectoralis major muscle and to the most proximal part of the axilla. The local anesthetic mixture (1% lidocaine 20 ml + 0.25% bupivacaine 15 ml) was injected to the place (point) where the distal motor responses of the median and ulnar nerves were elicited at the same time, before dropping the stimulation current down to 0.5 mA. In our study, demographic data, motor and sensory block times, the success rate and the complications of the block were evaluated.RESULTS:The mean block performance time was 1.21±0.39 min in our 40 patients. The onset time of the motor block was 14.20±4.96 min and the sensory block was 17.19±2.71 min, respectively. The success rate of the block was 97.5 percent. No complication was found during 24 hours postoperatively. The sensory and motor functions returned properly in all patients.CONCLUSION:In our study we found that the single injection axillary block tecnique was easy to perform with its higher success, and lower complication rates. Therefore we concluded that axillary block should be supported in appropriate cases.

Der „Wide-Awake Approach“ - Effizienz und Patientensicherheit bei der Karpaldachspaltung

In order to improve operating room efficiency in our institution, we introduced the wide-wake approach for carpal tunnel releases in 2012. This study examines the effect of this new anaesthetic technique on the work-flow and the duration of operation compared to the previously used axillary plexus anaesthesia.In this retrospective study, we reviewed the surgical case data of all patients in whom carpal tunnel releases had been performed as single procedures. 120 procedures of the year 2011, performed under axillary plexus anaesthesia, were compared to 153 procedures of the year 2012, performed as wide-awake surgery. We hypothesised that an earlier beginning of the first operation of the day with wide-awake surgery. Furthermore, we expected a shorter surgical time as well as a shorter interval between 2 carpal tunnel releases.By introduction of the wide-awake -approach, the first operation began a mean of 11 min earlier (p<0.001). While the surgical time did not change for the hand surgeon himself (10.7 vs. 10.2 min; p=0.478), the surgical time shortened significantly, when residents performed the operation (19.1 vs. 15.9 min, p<0.001). The interval between 2 carpal tunnel releases shortened from 19.8 to 17.7 min (p=0.009). Secure preparation was accomplished by the hypoperfused situs, when the wide-awake approach was applied, even though a tourniquet was not used. In the post-operative control, no complicated wound healings were noted.The wide-awake approach has proven to be reliable for the operating room -efficiency and, likewise, for patient safety. Therefore, we can recommend this technique without restrictions for carpal tunnel releases.

Axillary arteriovenous fistula after axillary plexus block

This report presents the case of a 51-year-old man who had an axillary arteriovenous fistula (AVF) as a complication of an axillary plexus block that was performed for internal fixation for a right forefinger phalanx fracture 4 years previously. While performing the axillary plexus block, a 22-gauge needle was placed inside the axillary sheath by observing the pulsations of the axillary artery. A pulsatile mass was found in the right axilla 1 day after the block was performed. Apart from this soft mass, the patient had no symptoms of vascular nerve damage. As the mass gradually increased in size, it became painful. During the past 3 months, in particular, the patient experienced repeated attacks of intermittent sharp pain and requested surgery. Digital subtraction angiography, performed 4 years after the axillary block, showed a tumor-like dilation was developing in both the right axillary artery and vein, almost simultaneously. Thus, the diagnosis of AVF was confirmed. The false aneurysm sac was excised and lateral repair of the axillary artery and vein was carried out under general anesthesia. Postoperative recovery was uneventful. The possible occurrence of an AVF after axillary plexus block should be kept in mind, because early diagnosis and treatment are necessary to avoid development of AVF and false aneurysm.

High- Versus Low-Stimulation Current Threshold for Axillary Plexus Blocks

For nerve stimulator-guided regional anesthesia, one has to compromise between a presumed low success rate (using a high-current threshold) and a presumed increased risk of nerve damage (using a low-current threshold). We hypothesized that high-current thresholds in the range of 0.9 to 1.1 mA are not inferior with respect to the procedural and latency times compared with low threshold currents in the range of 0.3 to 0.5 mA for nerve stimulation in brachial plexus blocks. Two hundred five patients scheduled for elective surgery were randomized to a low (0.3-0.5 mA, n = 103) or a high (0.9-1.1 mA, n = 102) stimulation current threshold for the axillary plexus block with 40 mL local anesthetic mixture (20 mL, each of prilocaine 1% and ropivacaine 0.75%). The primary end point was the time to complete sensory block. The secondary outcome measures were the time to readiness for surgery (defined as the time from the start of block procedure to complete sensory block) and the block performance time. The noninferiority margin was set at 5 minutes and was evaluated using the two-sided 95% bootstrap-confidence intervals ([CIs] 100,000 replications) for differences in means. The mean times to complete sensory block revealed a significant decrease with the low-current group (17.9 ± 12.1 (mean ± SD) versus 22.8 ± 12.4 minutes; 95% CI, 1.1 to 8.6; p = 0.012). The time to readiness for surgery was 30.3 ± 13.8 minutes in the low-current group and 31.7 ± 12.9 minutes in the high-current group (95% CI, -2.7 to 5.5; p = 0.49). The performance time was significantly shorter in the high-current threshold group (9.5 ± 4.7 versus 11.9 ± 5.7 minutes; 95% CI, -4 to 1.1; p = 0.001). Noninferiority for the high-current threshold technique could neither be confirmed for the primary end point nor for secondary end points. However, we consider a difference in mean times of approximately 8.5 minutes to achieve readiness for surgery acceptable for clinical practice.

Comparison of Local Anesthetic Mixtures with Tramadol or Fentanyl for Axillary Plexus Block in Orthopaedic Upper Extremity Surgery

The local anesthetic mixtures are performed for peripheral nerve blocks to accelerate the onset time of sensorial and motor blocks. Also adjuvant agents can be added to local anesthetics to improve the quality and duration of plexus blocks. In this study, we compared the effect of tramadol and fentanyl as adjuvant agents to local anesthetic mixtures in axillary plexus block for orthopedic upper extremity surgery. After approval of hospital ethics committee and written patient consent, sixty patients were enrolled to the study in three groups; The Control Group (Group C, 40 mL of 0.25% levobupivacaine + 40 mg lidocaine n:20), the Fentanyl Group(Group F, 40 mL of 0.25% levobupivacaine + 40 mg lidocaine + 50 mcg fentanyl n:20), the Tramadol Group (Group T, 40 mL of 0.25% levobupivacaine + 40 mg lidocaine + 100 mg tramadol n:20) for axillary plexus block. Groups were compared for partial and complete motor and sensorial block, onset time, partial and complete motor and sensorial block recover time, and postoperative first analgesic requirement time (VAS >4). In Group T partial sensorial block onset time was shorter than Group C and complete sensorial block onset time was shorter than Group C and Group F. In Group T complete sensorial block recover time was longer than Group C and Group F. The postoperative first analgesic requirement time was significantly longer in Group T and F when compared with Group C and significantly longer in Group T when compared with Group F. We conclude that the addition of tramadol or fentanyl to local anesthetic mixtures as an adjuvant agent for axillary block provide better postoperative analgesia for orthopedic upper extremity surgery. Furthermore tramadol more improves the block quality than fentanyl.

Bilateral ultrasound‐guided axillary plexus anesthesia in a child with dystrophic epidermolysis bullosa

Bilateral ultrasound‐guided axillary plexus anesthesia in a child with dystrophic epidermolysis bullosa

Tramadol as an adjunct for levobupivacaine in axillary plexus blockade: a prospective, randomized, double-blind study*

To evaluate the effect of tramadol addition to levobupivacaine in axillary plexus blockade in a prospective, randomized double-blind study. Materials and methods: A total of 60 patients scheduled to undergo hand and forearm surgery under axillary plexus blockade were randomly divided into 2 groups. Group L received 36 mL of racemic 0.5% levobupivacaine with 2 mL of saline, whereas Group LT received 2 mL (100 mg) of tramadol instead of saline. After routine monitorization, axillary block was performed with a multistimulation technique using a nerve stimulator. Motor (finger, wrist, and elbow movements) and sensory (pinprick sensation for the cutaneous supply) block characteristics for radial, median, ulnar, and musculocutaneous nerves were determined every 5 min. Postoperative motor and sensory block duration, analgesic consumption, and numeric rating scale (NRS) scores were also recorded. Results: In each group, 2 patients had block failures. The data for the remaining 56 patients were analyzed. There were no significant differences between the study groups according to motor and sensory block characteristics of 4 nerves, block durations, analgesic consumption, and NRS scores. Conclusion: The addition of 100 mg of tramadol to 0.5% levobupivacaine for axillary brachial plexus blockade neither improved the intraoperative block quality nor prolonged the duration of postoperative analgesia.

Incidence of Regional Pain Syndrome after Carpal Tunnel Release. Is there a Correlation with the Anesthetic Technique?

Complex regional pain syndrome (CRPS) previously known as reflex sympathetic dystrophy refers to a set of signs and symptoms that include pain, increased sweating, and vasomotor instability. Pain is usually triggered by a noxious stimulus in a peripheral nerve, which is disproportionate to the triggering stimulus. Its development after surgery is not uncommon varying with the type of intervention. An incidence of 2.1 to 5% has been reported after carpal tunnel release (CTR). Sympathetic blockade may prevent the onset of CRPS. However, there is no study validating this technique to prevent CRPS after CTR. The objective of the present study was to define the incidence of CRPS after CTR and its relationship with four anesthetic techniques. Patients were randomly distributed to undergo one of the following techniques: general anesthesia, regional intravenous anesthesia with lidocaine, regional intravenous anesthesia with lidocaine and clonidine, or axillary plexus block. Postoperatively, they were followed-up by a nurse who was unaware of the anesthetic technique used, and follow-up was done through electronic patient records for up to 6 months after the anesthesia. During this period signs and symptoms typical of CRPS were investigated and, if positive, treatment was instituted. A descriptive evaluation using the chi-square test was performed. Three-hundred and one patients were investigated. Twenty-five of them developed CRPS, an incidence of 8.3%. Predominance was not observed among the anesthetic techniques used. Other factors such as smoking, profession, and other concomitant diseases were also investigated, and none showed a relationship with the development of post-CTR CRPS. Complex regional pain syndrome has an incidence of 8.3% after CTR surgery without association with the anesthetic techniques investigated.

Ultrasound-Guided Axillary Plexus Block in a Child with Dystrophic Epidermolysis Bullosa

We report the use of ultrasound-guided axillary brachial plexus block in a child with dystrophic epidermolysis bullosa needing surgical treatment of the right hand. The regional anaesthesia was used in association with sedation/ anaesthesia. This technique is suitable for these difficult patients because it can minimise the risk of new bullae formation due to palpation of landmarks or unintentional intra- or subcutaneous injections. Initial anaesthesia/sedation was provided with sevoflurane until intravenous access was obtained, following which intravenous propofol infusion with ketamine boluses without any invasive airway management was continued for performance of the block and the procedure. This management plan provided good surgical conditions, early postoperative analgesia, minimised stress for the patient and avoided the need to manipulate the airway with instruments and the associated risk of mucosal bullae. The classification and breadth of clinical manifestation of epidermolysis bullosa is complex and briefly summarised. The anaesthetist should clarify the details of a particular patient's form of epidermolysis bullosa, especially in terms of mucosal involvement, as this may greatly influence planning for a procedure.

Anesthesia care in a medium-developed country: a nationwide survey of Mongolia

Study Objective To evaluate the current status of anesthesia and its allied disciplines in Mongolia. Design Nationwide questionnaire survey. Setting Two university hospitals. Measurements A total of 44 hospitals that include a department of surgery and that were registered at the Mongolian Ministry of Health were queried. The questionnaire included 44 questions in two sections. The first section consisted of 6 general questions about the hospital, and the second section included 40 questions on anesthesia and perioperative patient care. The Mann-Whitney U-test, Chi²-tests, and a bivariate correlation analysis were used for statistical analysis. Main Results 44 (100%) questionnaires were returned. Twenty-two (50%) hospitals were located in the capital city of Ulaanbaatar. Nine hundred (median; interquartile range: 413-1,468) surgical interventions were performed annually in the study hospitals. Physician anesthesiologists delivered anesthesia in all hospitals. Techniques for general anesthesia included endotracheal intubation (95.5%), laryngeal mask ventilation (13.6%), mask ventilation (27.3%), dissociative ketamine anesthesia (84.1%), and combined general/regional anesthesia (63.6%). Regional anesthetic techniques included spinal (97.7%), epidural (43.2%), axillary plexus (40.9%), peripheral nerve (13.6%), and local anesthesia (15.9%). The most frequently used hypnotics were ketamine (86.4%) and thiopental sodium (70.5%). Halothane was available in all hospitals. Oxygen was available during anesthesia in 95.5% of hospitals. The most widely available intraoperative monitoring equipment were a stethoscope (84.1%), oximeter (81.8%), and sphygmomanometer (84.1%). A recovery room was available in 22 (50%) hospitals. Conclusions Anesthesia is an underdeveloped and under-resourced medical specialty in Mongolia.

Effect of temperature of ropivacaine on onset time and anaesthetic quality in an ultrasound guided axillary plexus blockade. Comparison of ropivacaine 0.75% in three different temperatures (7°C, 21°C, 37°C)

Effect of temperature of ropivacaine on onset time and anaesthetic quality in an ultrasound guided axillary plexus blockade. Comparison of ropivacaine 0.75% in three different temperatures (7°C, 21°C, 37°C)

Minimum volume of local anaesthetic required to surround each of the constituent nerves of the axillary brachial plexus, using ultrasound guidance: a pilot study

The minimum effective volume of local anaesthetic needed to provide effective analgesia of the four main branches of the axillary brachial plexus is unknown. This study was performed to determine the minimum volume of local anaesthetic required to surround the nerves of the axillary brachial plexus and document onset and duration of sensory and motor effects. We enrolled 19 ASA I-II patients undergoing hand or forearm surgery. The four nerves of the axillary plexus were identified with ultrasound guidance. Lidocaine 1.5% with epinephrine 1:200 000 was loaded into a syringe driver. A 22 G needle was inserted in the long axis to each nerve and injection commenced using the bolus function (600 ml h(-1)). The needle was repositioned until the nerve was completely surrounded. The bolus dose in millilitres displayed on the syringe driver was recorded. This was repeated for each nerve. The degree of sensory and motor block was recorded as secondary outcomes. The mean (95% CI) volume to surround each nerve was: radial 3.42 (2.84-3.99) ml, median 2.75 (2.31-3.19) ml, ulnar 2.58 (2.14-3.03) ml, and musculocutaneous 2.30 (1.96-2.64) ml. The mean (95% CI) onset time for complete sensory block was: radial 22.5 (13.5-31.5) min, median 26.8 (18.5-35.0) min, ulnar 26.6 (17.8-35.4) min, and musculocutaneous 15.8 (7.45-24.2) min. The mean (95% CI) last recorded time with complete block was: radial 137.1 (105.6-168.7) min, median 144.7 (123.4-166.0) min, ulnar 183.2 (158.1-208.2) min, and musculocutaneous 158.3 (131.8-184.9) min. Seven patients required additional local anaesthetic infiltration and two required i.v. analgesia. No patient required conversion to general anaesthesia for surgery. We found that it is possible to surround each nerve of the axillary brachial plexus with 2-4 ml of local anaesthetic. We speculate that increasing this volume would produce blocks of quicker onset and longer duration while still using smaller volumes than previously thought.

Ultrasonographic guided axillary plexus blocks with low volumes of local anaesthetics: a crossover volunteer study

Our study group recently evaluated an ED(95) local anaesthetic volume of 0.11 ml.mm(-2) cross-sectional nerve area for the ulnar nerve. This prospective, randomised, double-blind crossover study investigated whether this volume is sufficient for brachial plexus blocks at the axillary level. Ten volunteers received an ultrasonographic guided axillary brachial plexus block either with 0.11 ('low' volume) or 0.4 ('high' volume) ml.mm(-2) cross-sectional nerve area with mepivacaine 1%. The mean (SD) volume was in the low volume group 4.0 (1.0) and 14.8 (3.8) ml in the high volume group. The success rate for the individual nerve blocks was 27 out of 30 in the low volume group (90%) and 30 out of 30 in the high volume group (100%), resulting in 8 out of 10 (80%) vs 10 out of 10 (100%) complete blocks in the low vs the high volume groups, respectively (NS). The mean (SD) sensory onset time was 25.0 (14.8) min in the low volume group and 15.8 (6.8) min in the high volume group (p < 0.01). The mean (SD) duration of sensory block was 125 (38) min in the low volume group and 152 (70) min in the high volume group (NS). This study confirms our previous published ED(95) volume for mepivacaine 1% to block peripheral nerves. The volume of local anaesthetic has some influence on the sensory onset time.