Evaluation of a Multiple Injection Axillary Block Technique by Clinical Assessment and MRI

Trygve Kjelstrup, MD, has developed an axillary brachial plexus block technique that combines the insertion of a catheter with a double transarterial injection technique. In clinical practice this triple-deposit method showed promising block effect on the nerves of the brachial plexus that innervate the upper extremity. In the present thesis the triple-deposit axillary block method was evaluated by clinical tests and with MRI. Particularly, we investigated whether differences in block success could be explained by differences in local anaesthetic distribution as observed by MRI. This thesis demonstrated that the triple-deposit method has a higher block success and shorter onset time compared with the single- or double-deposit method. These findings could be explained by analysis of the MRI distribution patterns. MRI showed a wide variability as to where the musculocutaneous nerve leaves the axillary sheath. With the triple-deposit method the nerve can be successfully blocked. We conclude that an axillary plexus block performed with the triple-deposit technique is preferable as compared to the single- and double-deposit method

The relationship of the musculocutaneous nerve to the brachial plexus evaluated by MRI

Axillary plexus blocks (AXB) are widely used for upper limb operations. It is recommend that AXB should be performed using a multiple injection technique. Information about the course and position of the musculocutaneous nerve (MCN) is of relevance for AXB performance. The objective of this study was to examine the position of the MCN and its relationship to the axillary sheath using MRI. 54 patients underwent an AXB with 40 ml of local anaesthetic before MRI examination. The course of the MCN and the position where it left the axillary sheath and perforated the coracobrachial muscle (MCN exit point), in relation to the axillary artery and the block needle insertion point in the axillary fold, were recorded. The MCN was seen clearly in 23, partly in 26, and not identified in five patients at the MCN exit point. The mean distance from the insertion point of the block needle in the axillary fold to the MCN exit point was 36.8 mm (SD = 18.9, range: 0–90.5). In 37 patients the MCN exit point was positioned inside the Q1 quadrant (lateral anterior to the axillary artery) and in 11 patients inside the Q2 quadrant (medial anterior to the axillary artery). There is a wide variability as to where the musculocutaneous nerve (MCN) leaves the axillary sheath. Therefore multiple injection techniques, or the use of a proximally directed catheter, should be appropriate to block the MCN

The relationship of the musculocutaneous nerve to the brachial plexus evaluated by MRI

Axillary plexus blocks (AXB) are widely used for upper limb operations. It is recommend that AXB should be performed using a multiple injection technique. Information about the course and position of the musculocutaneous nerve (MCN) is of relevance for AXB performance. The objective of this study was to examine the position of the MCN and its relationship to the axillary sheath using MRI. 54 patients underwent an AXB with 40 ml of local anaesthetic before MRI examination. The course of the MCN and the position where it left the axillary sheath and perforated the coracobrachial muscle (MCN exit point), in relation to the axillary artery and the block needle insertion point in the axillary fold, were recorded. The MCN was seen clearly in 23, partly in 26, and not identified in five patients at the MCN exit point. The mean distance from the insertion point of the block needle in the axillary fold to the MCN exit point was 36.8 mm (SD = 18.9, range: 0–90.5). In 37 patients the MCN exit point was positioned inside the Q(1) quadrant (lateral anterior to the axillary artery) and in 11 patients inside the Q(2) quadrant (medial anterior to the axillary artery). There is a wide variability as to where the musculocutaneous nerve (MCN) leaves the axillary sheath. Therefore multiple injection techniques, or the use of a proximally directed catheter, should be appropriate to block the MCN

Exergy-based performance indicators for industrial practice

Key performance indicators (KPIs) are powerful tools that industries can use not only to monitor their activities but also to highlight their unexploited potential. Energy-based KPIs are nowadays mostly used to evaluate industrial process performances. However, these indicators might present some limitations and might give misleading results in some circumstances. An example is represented by industrial processes that make use of different energy forms (e.g. electricityandheat)andofdifferentmaterialinputs,andarethereforedifficulttocompareintermsofenergy. Afurther example can be found in the Carnot engine that, despite being ideal, can have quite low energy efficiency (e.g. the energy efficiency of a Carnot engine working between 700 K and 300 K is 57%), suggesting that its performance can be improved. The use of exergy-based KPIs allows us to overcome many of the limitations of energy-based indicators. The exergy efficiency of Carnot engines is 100%, clearly indicating that the system cannot be further improved. Moreover, the use of specific exergy consumption instead of specific energy consumption to monitor the performance of a process allows one to take into account possible differences in quality of material and energy streams. In thepresent work, exergy-basedKPIs for industrial use are reviewed. The paper outlines advantages andlimitations of the reviewed indicators, with the scope of promoting their use in industry. A systematic use of exergy-based KPIs not only gives a meaningful representation of process performances in terms of resource use, but it can also direct efforts to improve the processes. In order to better understand their meaning under different circumstances, the revised indicators are applied to three industrial processes

Exergy-based performance indicators for industrial practice

Key performance indicators (KPIs) are powerful tools that industries can use not only to monitor their activities but also to highlight their unexploited potential. Energy-based KPIs are nowadays mostly used to evaluate industrial process performances. However, these indicators might present some limitations and might give misleading results in some circumstances. An example is represented by industrial processes that make use of different energy forms (e.g. electricityandheat)andofdifferentmaterialinputs,andarethereforedifficulttocompareintermsofenergy. Afurther example can be found in the Carnot engine that, despite being ideal, can have quite low energy efficiency (e.g. the energy efficiency of a Carnot engine working between 700 K and 300 K is 57%), suggesting that its performance can be improved. The use of exergy-based KPIs allows us to overcome many of the limitations of energy-based indicators. The exergy efficiency of Carnot engines is 100%, clearly indicating that the system cannot be further improved. Moreover, the use of specific exergy consumption instead of specific energy consumption to monitor the performance of a process allows one to take into account possible differences in quality of material and energy streams. In thepresent work, exergy-basedKPIs for industrial use are reviewed. The paper outlines advantages andlimitations of the reviewed indicators, with the scope of promoting their use in industry. A systematic use of exergy-based KPIs not only gives a meaningful representation of process performances in terms of resource use, but it can also direct efforts to improve the processes. In order to better understand their meaning under different circumstances, the revised indicators are applied to three industrial processes.submittedVersionThis is the pre-peer reviewed version of an article, which has been published in final form at 10.1002/er.4123. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving

MRI of axillary brachial plexus blocks: A randomised controlled study

BACKGROUND: Axillary 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. OBJECTIVES: Could differences in block success between single, double and triple deposits methods be explained by differences in local anaesthetic distribution as observed by MRI? DESIGN: A blinded and randomised controlled study. SETTING: Conducted at Oslo University Hospital, Rikshospitalet, Norway from 2009 to 2011. PATIENTS: Forty-five ASA 1 to 2 patients scheduled for surgery were randomised to three equally sized groups. All patients completed the study. INTERVENTIONS: Patients 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 MEASURES: Sensory block effect and MRI distribution pattern. RESULTS: The 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. CONCLUSION: Distal 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 REGISTRATION: ClinicalTrials.gov identifier: NCT01033006

Supporting online material is available on Science Online

To determine how spatial scale is represented in the pyramidal cell population of the hippocampus, we recorded neural activity at multiple longitudinal levels of this brain area while rats ran back and forth on an 18-meter-long linear track. CA3 cells had well-defined place fields at all levels. The scale of representation increased almost linearly from <1 meter at the dorsal pole to~10 meters at the ventral pole. The results suggest that the place-cell map includes the entire hippocampus and that environments are represented in the hippocampus at a topographically graded but finite continuum of scales. A lthough the basic intrinsic circuitry of the hippocampus is similar along the entire dorsoventral axis of the structure (1), dorsal and ventral regions may not have similar functions. Dorsal and intermediate regions are preferentially connected, via the dorsolateral and intermediate bands of the entorhinal cortex, to visual and somatosensory cortices important for accurate spatial navigation (2-5), and selective lesions in these hippocampal regions can lead to impairments in spatial learning Conventional recording environments may be too small to visualize the most extended hippocampal representations (figs. S2 to S4 and supporting online text). Thus, we tested the animals on an 18-m-long linear track. Well-delineated place fields, defined as spatially stable contiguous regions with firing above 20% of the peak rate, could be found at all longitudinal levels of the hippocampu

The relationship of the musculocutaneous nerve to the brachial plexus evaluated by MRI

Axillary plexus blocks (AXB) are widely used for upper limb operations. It is recommend that AXB should be performed using a multiple injection technique. Information about the course and position of the musculocutaneous nerve (MCN) is of relevance for AXB performance. The objective of this study was to examine the position of the MCN and its relationship to the axillary sheath using MRI. 54 patients underwent an AXB with 40 ml of local anaesthetic before MRI examination. The course of the MCN and the position where it left the axillary sheath and perforated the coracobrachial muscle (MCN exit point), in relation to the axillary artery and the block needle insertion point in the axillary fold, were recorded. The MCN was seen clearly in 23, partly in 26, and not identified in five patients at the MCN exit point. The mean distance from the insertion point of the block needle in the axillary fold to the MCN exit point was 36.8 mm (SD = 18.9, range: 0–90.5). In 37 patients the MCN exit point was positioned inside the Q(1) quadrant (lateral anterior to the axillary artery) and in 11 patients inside the Q(2) quadrant (medial anterior to the axillary artery). There is a wide variability as to where the musculocutaneous nerve (MCN) leaves the axillary sheath. Therefore multiple injection techniques, or the use of a proximally directed catheter, should be appropriate to block the MCN