Interscalene brachial plexus block: can the risk of entering the spinal canal be reduced? A study of needle angles in volunteers undergoing magnetic resonance imaging.

BACKGROUND: Spinal cord damage during interscalene brachial plexus block has been attributed to needle entry into the spinal canal. The purpose of this study was to identify the angles and depths of needle insertion that increase the likelihood of such an event, using the traditional classic interscalene approach and two more proximal entry points. METHOD: Magnetic resonance images of the neck from 10 healthy volunteers were used to obtain the three-dimensional spatial coordinates of three skin markers and the right-sided cervical nerves at the exiting neural foramina. The distance of the intervertebral foramina from the skin markers and the angles of the needle vector and the foramina were calculated. RESULTS: The distance from the skin to the intervertebral foramen may be as short as 2.5 cm with the classic approach. A caudal angulation greater than 50 degrees seemed to eliminate the risk of needle entry through the foramen. CONCLUSION: With the classic approach to the interscalene block, there is a greater possibility of the needle passing through the intervertebral foramen if the needle is advanced too deeply. More proximal entry points and techniques that use a more steeply angled needle may reduce the risk of entry into the spinal space.

A study of the characteristics of single-injection insulated block needles in a biologic model.

BACKGROUND AND OBJECTIVES: Single-injection block needles are manufactured in many different lengths, diameters, and tip designs, but the literature contains no reports of methods to assess clinical characteristics of regional-block needles. A novel animal model for the assessment of the characteristics of single-injection regional anesthesia needles is described. METHODS: Nine different needles designed for peripheral nerve blocks that were fitted with identical hubs were used. Pork bellies were used as the biologic model. The bellies were mounted such that the needles passed from inside to outside. The last layer to be penetrated was the skin. Ten experienced and blinded anesthesiologists scored the feel, resistance, and usability of the 9 needles during their passage through similarly prepared pork bellies. Two identical (index) needles were included in the study to assess the internal validity of the study. RESULTS: The overall scoring was acceptably consistent and repeatable and showed statistically significant differences between the needles tested. The needles that were judged the most usable were those with a moderate resistance to passage through the tissue and a high degree of feel, which was defined as the ability to appreciate the passage of the needle through the tissue planes. Needles with very high or very low resistances and those with poor feel scored poorly on the usability scale. Differences in individuals' assessment of the index needles suggested some within-subject variability during the study. CONCLUSIONS: This type of biologic model can be used for the quantifiable and repeatable assessment of different needle tip designs. Needles with moderate resistance and high feel were preferred.

Lower lobe collapse during continuous interscalene brachial plexus local anesthesia at home.

OBJECTIVES: We report a case of pulmonary left lower lobe collapse following an interscalene local anesthetic infusion administered at home. This case highlights the need for patient education and postoperative communication. CASE REPORT: report A 52-year-old male patient presented for a rotator cuff repair. He was a chronic tobacco abuser with a history of occasional chest pain of unexplained cause. An interscalene catheter was placed preoperatively and surgery was performed under a combination of an interscalene block and a general anesthetic. An infusion of 0.2% ropivacaine was started via the interscalene catheter postoperatively and continued at home following his discharge from the hospital on the third postoperative day. Within 24 hours of discharge, he was readmitted to the hospital after complaining of chest pain and dyspnea. The patient was seen in the emergency department by nonanesthesiologists who were not familiar with the potential for interscalene blocks to cause diaphragmatic paresis. CONCLUSIONS: Good communication must be maintained with the patient at all times. Doctors from other specialties may be unaware of the potential complications of an interscalene block.