Shoulder position influences the location of the musculocutaneous nerve in the axillary fossa.

In the axillary fossa, the musculocutaneous nerve (MC) is generally distant from the axillary artery and from the other brachial plexus nerves. In that way, MC requires a specific block. We observed that the location of MC is influenced by the position of the patient's arm and shoulder. Abduction of the shoulder significantly reduced the distance between the MC and the axillary artery. This change in the location of the MC is probably due to the moving of the nerve because of muscle rearrangements and the ability to achieve better proximity of the probe in the axillary fossae.

Evaluation of a new disinfection method for ultrasound probes used for regional anesthesia: ultraviolet C light.

OBJECTIVES: Ultrasound-guided regional anesthesia is commonly used for block placement. At present, the risk of cross contamination from probes is not well documented. To avoid transmission of infectious agents, several methods have been used for probe disinfection and protection. The aim of this study was to evaluate the antibacterial efficacy of a new high-level disinfection method based on ultraviolet C (UV-C) light under routine conditions after block placement with an unprotected probe. METHODS: The study was after approval by the local Ethics Committee. In the first part of the study, 15 ultrasound probes were exposed to a large inoculum of 3 bacteria. Ultraviolet C disinfection consisted of cleaning the probe with dry and disinfectant-impregnated paper followed by a 90-second UV-C disinfection cycle in a decontamination chamber. A protocol was established to retrieve the probe with sterile gloves after opening the door of the chamber. In the second part, 50 blocks were placed with ultrasound-guided regional anesthesia. The skin was first prepared with an antiseptic solution, and sterile gel was applied; no covers were used to protect the probes. The blocks were then disinfected with UV-C light. Bacteriologic samples were collected before and after the UV-C method and inoculated on chocolate agar plates. RESULTS: During the first part of the study, all probes were infected after inoculation (>150 colony-forming units) but were considered sterile (<10 colony-forming units) after disinfection. During the second part of the study, all probes were considered sterile before and after disinfection. CONCLUSIONS: Ultraviolet C disinfection seems relevant for ultrasound-guided regional anesthesia just before block placement. It offers simple, fast, and effective high-level disinfection. Moreover, this method should obviate the use of sterile probe covers, which can improve echogenicity.

Comfort of the patient during axillary blocks placement: a randomized comparison of the neurostimulation and the ultrasound guidance techniques.

BACKGROUND: Axillary brachial plexus block under neurostimulation is commonly used for upper limb surgery, but it is sometimes recognized as an uncomfortable technique, with most patients identifying electrical stimulation as an unpleasant moment. Ultrasound-guided regional anaesthesia, which becomes an increasingly popular technique, does not require electrical stimulation and then should theoretically improve axillary block placement comfort. The aim of this study was to compare the comfort of the patients during axillary block placement with neurostimulation and ultrasound guidance using either the out-of-plane or the in-plane approach. METHODS: Consecutive patients were prospectively enrolled in three equal groups: neurostimulation, ultrasound out-of-plane and ultrasound in-plane approaches. A score was used to measure the comfort of the patients during axillary blocks placement. This score included three criteria: maximum pain intensity perceived during block placement measured using a visual analogue scale (0, no pain and 100, maximal or worse imaginable pain), the number of unpleasant events declared by the patients and the satisfaction of the patient (unsatisfied, acceptable, satisfied, very satisfied). The comfort score was calculated as the sum of each criterion, which was attributed a value of 0 or 1: visual analogue scale (30/100, 0), number of unpleasant events (0, 1; >or=1, 0) and satisfaction (satisfied or very satisfied, 1; acceptable or unsatisfied, 0). Procedures of axillary blocks placement resulting in a comfort score of 3 and 2 were arbitrary considered as very comfortable and comfortable, respectively. Success rate of axillary blocks, time to perform block and complications related to procedures were noted. RESULTS: One hundred and twenty patients were included. In the ultrasound out-of-plane group, 55% (22/40) and 25% (10/40) of the procedures were very comfortable and comfortable as compared with 32% (13/40, P < 0.05) and 20% (8/40, P < 0.01) in the ultrasound in-plane group and 25% (10/40, P < 0.01) and 8% (3/40, P < 0.01) in the neurostimulation group, respectively. Duration of axillary placement was significantly smaller in the ultrasound out-of-plane group as compared with that of in-plane approaches (P < 0.05) and neurostimulation (P < 0.01). CONCLUSION: The present study showed that the ultrasound approaches were less painful and more comfortable than neurostimulation to place axillary blocks. We also showed that, although pain intensity resulting from blocks placement was similar with the ultrasound approaches, very comfortable procedures were more frequent with the out-of-plane than with the in-plane approach.

Spread of injectate associated with radial or median nerve-type motor response during infraclavicular brachial-plexus block: an ultrasound evaluation.

BACKGROUND AND OBJECTIVES: We have compared ultrasound characteristics of spread during infraclavicular brachial-plexus blocks by use of electrically evoked radial-nerve- or median-nerve-type distal motor responses to guide the injection of 30 mL of 1.5% mepivacaine. METHODS: Consecutive patients who required surgery distal to the upper arm were prospectively included in this study. With radial- or median-evoked distal motor response at a stimulating current intensity of less than 0.5 mA, patients were distributed into 2 equal groups. An independent investigator blinded to the evoked response described ultrasound characteristics of the spread of local anesthetic and assessed block quality 30 minutes after placement. A quality diffusion score proportional to the extent and intensity of spread around the axillary artery was used, and dynamic movements during injection were noted. RESULTS: Thirty-two patients were included. With radial-nerve-type motor response, the success rate of infraclavicular plexus block was 100%, but 3 supplemental axillary blocks were requested with median-nerve-type motor response. Quality diffusion scores were significantly higher with radial-nerve-type as compared with median-nerve-type motor response (P = .03). Injection after radial-nerve-type motor response resulted in a typical and reproducible ultrasound feature of posterior local-anesthetic spread associated with medial and upper movement of the axillary artery. With median-nerve-type motor response, failed blocks were associated with a specific posterior displacement of the axillary artery that resulted from superficial spread. CONCLUSION: We have demonstrated that as compared with median-nerve-type motor response, injection performed after a radial-nerve-type motor response promoted reproducible and remarkable ultrasound spread characteristics associated with complete sensory block of the 3 cords at 30 minutes.

Single-stimulation, low-volume infraclavicular plexus block: influence of the evoked distal motor response on success rate.

BACKGROUND AND OBJECTIVES: We compared the success rate of single-injection infraclavicular plexus block by using electrically evoked radial, ulnar, or median nerve-type distal motor response to guide the injection of local anesthetic. METHODS: Consecutive patients requiring surgery distal to the upper arm were prospectively included in this study over a 6-month period. No search for predetermined distal motor responses was performed. The first qualifying distal motor response evoked for a stimulating current intensity of <0.5 mA distributed patients into 3 groups of patients. The study was continued until 3 groups of 60 patients were fulfilled. Twenty to 25 minutes after the injection of 30 mL of 1.5% mepivacaine, blinded evaluation of block quality was performed. A successful block was defined by the presence of a complete sensory block of the 5 major nerve distal distributions of the arm. RESULTS: Five hundred patients were included. The first evoked distal motor response was of radial, median, and ulnar nerve type in 46% (n = 230), 42% (n = 210), and 12% (n = 60) cases, respectively. The success rate of the infraclavicular plexus block was significantly higher when the injection was performed on a radial nerve-type response (90%) as compared with the median (74%) or ulnar (68%) nerve distal motor response. Intraoperative sedation and general anesthesia were not needed. None of the patients experienced specific complications. CONCLUSION: We showed that evoked distal motor response influenced the success rate of single-injection infraclavicular plexus block. The highest success rate was obtained when injection was performed after radial nerve-type motor response.