Intercostal nerve electrodiagnostic testing in rib fractures.

INTRODUCTION/AIMS: Intercostal nerve injury can occur after rib fractures, resulting in denervation of the abdominal musculature. Loss of innervation to the rectus abdominis and intercostal muscles can cause pain, atrophy, and eventual eventration, which may be an underrecognized and thus undertreated complication of rib fractures. We investigated the clinical utility of intercostal nerve electrodiagnostic testing following rib fractures to diagnose and localize nerve injury at levels T7 and below. METHODS: Five patients with displaced bicortical rib fractures involving the 7th-11th ribs and clinical eventration of the ipsilateral abdominal wall underwent intercostal nerve conduction studies (NCS) and needle electromyography (EMG) on the affected side. EMG of the rectus abdominis and intercostal muscles was performed with ultrasound guidance, and ultrasound measurements of rectus abdominis thickness were obtained to assess for atrophy. RESULTS: Average patient age was 59.4 years and average body mass index (BMI) was 31.5 kg/m2. Intercostal NCS and EMG were able to reliably diagnose and localize intercostal nerve damage after rib fractures. Ultrasound demonstrated an average rectus abdominis transverse cross-sectional thickness of 0.534 cm on the affected side, compared with 1.024 cm on the non-affected side. DISCUSSION: Intercostal electrodiagnostic studies can diagnose and localize intercostal nerve damage after displaced rib fractures. Musculoskeletal ultrasound can be used to diagnose and quantify rectus abdominis atrophy and to accurately and safely guide needle EMG to the intercostal and rectus abdominis muscles.

Serratus Anterior Plane Block and Intercostal Nerve Block after Thoracoscopic Surgery.

BACKGROUND: This study aimed to compare the postoperative analgesic effect between ultrasound-guided serratus anterior plane block (Group S, SAPB) and intercostal nerve block (Group I, ICNB) after single port video-assisted thoracoscopic surgery (S-VATS) in primary spontaneous pneumothorax. METHODS: In this prospective randomized controlled study, 54 patients were randomly assigned to two groups. Patients in Group S underwent the SAPB before the surgical drape by an anesthesiologist, and in Group I, ICNBs were performed just before the wound closure after S-VATS by an attending thoracic surgeon. The primary outcome was the numeric pain rating scale (NRS) score given by the patients for pain at the surgical incision site. NRS was assessed during resting and coughing statuses at 3, 6, and 12 hours postoperatively and at the time of the chest tube removal. The secondary outcomes included the number of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid administration until time to chest tube removal. RESULTS: There were no statistical differences between the two groups regarding age, body mass index, duration of operation, duration of anesthesia, and average NRS scores for the assigned time periods. There was no statistical significance in the number of opioid injections; however, NSAIDs were administered 2.8 times per patient in Group I, and 1.9 times per patient in Group S (p = 0.038). CONCLUSION: In the patients who underwent S-VATS with primary spontaneous pneumothorax, the SAPB provided similar postoperative pain relief with reducing the NSAIDs consumption compared with ICNB.

Postoperative Thoracic Pain Treatment: Serratus Anterior or Erector Spinae Plane Block?

BACKGROUND: Thoracic surgery is one of the most painful surgeries. Effective analgesia is important in postoperative pain management. In this study, we aimed to compare the two new fascial block techniques. METHODS: A total of 107 patients who underwent thoracic surgery between October 2018 and November 2019 were retrospectively evaluated. The study included 59 patients in the serratus anterior plane block (SAPB) group and 48 patients in the erector spinae plane block (ESPB) group. Both groups were administered 30 mL of 0.25% bupivacaine and their morphine consumption was evaluated by a patient-controlled analgesia (PCA) method during the 2nd, 6th, 12th, 24th, and 48th postoperative hours. Pain was measured with the visual analog scale (VAS). Intraoperative mean arterial pressure (MAP) and heart rate (HR) were recorded. RESULTS: During the first 24 hours, VAS values were significantly lower in the ESPB group (p < 0.05). Moreover, morphine consumption was significantly lower in the ESPB group in the 24th and 48th hours (p < 0.05). Intraoperative remifentanil consumption was also significantly lower in the ESPB group (p < 0.05). Intraoperative MAP in the ESPB group was found to be significantly lower after the 4th hour. HR was similar in both groups. CONCLUSION: ESPB was more effective compared with SAPB in postoperative thoracic pain management.

Task-dependent output of human parasternal intercostal motor units across spinal levels.

KEY POINTS: During breathing, there is differential activity in the human parasternal intercostal muscles and the activity is tightly coupled to the known mechanical advantages for inspiration of the same regions of muscles. It is not known whether differential activity is preserved for the non-respiratory task of ipsilateral trunk rotation. In the present study, we compared single motor units during resting breathing and axial rotation of the trunk during apnoea. We not only confirmed non-uniform recruitment of motor units across parasternal intercostal muscles in breathing, but also demonstrated that the same motor units show an altered pattern of recruitment in the non-respiratory task of trunk rotation. The output of parasternal intercostal motoneurones is modulated differently across spinal levels depending on the task and these results help us understand the mechanisms that may govern task-dependent differences in motoneurone output. ABSTRACT: During inspiration, there is differential activity in the human parasternal intercostal muscles across interspaces. We investigated whether the earlier recruitment of motor units in the rostral interspaces compared to more caudal spaces during inspiration is preserved for the non-respiratory task of ipsilateral trunk rotation. Single motor unit activity (SMU) was recorded from the first, second and fourth parasternal interspaces on the right side in five participants in two tasks: resting breathing and 'isometric' axial rotation of the trunk during apnoea. Recruitment of the same SMUs was compared between tasks (n = 123). During resting breathing, differential activity was indicated by earlier recruitment of SMUs in the first and second interspaces compared to the fourth space in inspiration (P < 0.01). By contrast, during trunk rotation, the same motor units showed an altered pattern of recruitment because SMUs in the first interspace were recruited later and at a higher rotation torque than those in the second and fourth interspaces (P < 0.05). Tested for a subset of SMUs, the reliability of the breathing and rotation tasks, as well as the SMU recruitment measures, was good-excellent [intraclass correlation (2,1): 0.69-0.91]. Thus, the output of parasternal intercostal motoneurones is modulated differently across spinal levels depending on the task. Given that the differential inspiratory output of parasternal intercostal muscles is linked to their relative mechanical effectiveness for inspiration and also that this output is altered in trunk rotation, we speculate that a mechanism matching neural drive to muscle mechanics underlies the task-dependent differences in output of axial motoneurone pools.

Diaphragmatic and intercostal electromyographic activity during neostigmine, sugammadex and neostigmine-sugammadex-enhanced recovery after neuromuscular blockade: A randomised controlled volunteer study.

BACKGROUND: Electromyographic activity of the diaphragm (EMGdi) during weaning from mechanical ventilation is increased after sugammadex compared with neostigmine. OBJECTIVE: To determine the effect of neostigmine on EMGdi and surface EMG (sEMG) of the intercostal muscles during antagonism of rocuronium block with neostigmine, sugammadex and neostigmine followed by sugammadex. DESIGN: Randomised, controlled, double-blind study. SETTING: Intensive care research unit. PARTICIPANTS: Eighteen male volunteers. INTERVENTIONS: A transoesophageal EMGdi recorder was inserted into three groups of six anaesthetised study participants, and sEMG was recorded on their intercostal muscles. To reverse rocuronium, volunteers received 50 µg kg neostigmine, 2 mg kg sugammadex or 50 µg kg neostigmine, followed 3 min later by 2 mg kg sugammadex. MAIN OUTCOME MEASURES: We examined the EMGdi and sEMG at the intercostal muscles during recovery enhanced by neostigmine or sugammadex or neostigmine-sugammadex as primary outcomes. Secondary objectives were the tidal volume, PaO2 recorded between the onset of spontaneous breathing and extubation of the trachea and SpO2 during and after anaesthesia. RESULTS: During weaning, median peak EMGdi was 0.76 (95% confidence interval: 1.20 to 1.80) µV in the neostigmine group, 1.00 (1.23 to 1.82) µV in the sugammadex group and 0.70 (0.91 to 1.21) µV in the neostigmine-sugammadex group (P < 0.0001 with EMGdi increased after sugammadex vs. neostigmine and neostigmine-sugammadex). The median peak intercostal sEMG for the neostigmine group was 0.39 (0.65 to 0.93) µV vs. 0.77 (1.15 to 1.51) µV in the sugammadex group and 0.82 (1.28 to 2.38) µV in the neostigmine-sugammadex group (P < 0.0001 with sEMG higher after sugammadex and after neostigmine-sugammadex vs. neostigmine). CONCLUSION: EMGdi and sEMG on the intercostal muscles were increased after sugammadex alone compared with neostigmine. Adding sugammadex after neostigmine reduced the EMGdi compared with sugammadex alone. Unlike the diaphragm, intercostal EMG was preserved with neostigmine followed by sugammadex. TRIAL REGISTRATION: EudraCT: 2015-001278-16; ClinicalTrials.gov: NCT02403063.

Absence of synergy for monosynaptic Group I inputs between abdominal and internal intercostal motoneurons.

Internal intercostal and abdominal motoneurons are strongly coactivated during expiration. We investigated whether that synergy was paralleled by synergistic Group I reflex excitation. Intracellular recordings were made from motoneurons of the internal intercostal nerve of T8 in anesthetized cats, and the specificity of the monosynaptic connections from afferents in each of the two main branches of this nerve was investigated. Motoneurons were shown by antidromic excitation to innervate three muscle groups: external abdominal oblique [EO; innervated by the lateral branch (Lat)], the region of the internal intercostal muscle proximal to the branch point (IIm), and muscles innervated from the distal remainder (Dist). Strong specificity was observed, only 2 of 54 motoneurons showing excitatory postsynaptic potentials (EPSPs) from both Lat and Dist. No EO motoneurons showed an EPSP from Dist, and no IIm motoneurons showed one from Lat. Expiratory Dist motoneurons fell into two groups. Those with Dist EPSPs and none from Lat (group A) were assumed to innervate distal internal intercostal muscle. Those with Lat EPSPs (group B) were assumed to innervate abdominal muscle (transversus abdominis or rectus abdominis). Inspiratory Dist motoneurons (assumed to innervate interchondral muscle) showed Dist EPSPs. Stimulation of dorsal ramus nerves gave EPSPs in 12 instances, 9 being in group B Dist motoneurons. The complete absence of heteronymous monosynaptic Group I reflex excitation between muscles that are synergistically activated in expiration leads us to conclude that such connections from muscle spindle afferents of the thoracic nerves have little role in controlling expiratory movements but, where present, support other motor acts.

A new suture technique avoids rib fractures and intercostal nerve trauma in thoracotomy.

This article describes an alternative suture technique for thoracotomy incisions. A modified mattress suture technique is used to fix the intercostal muscles. The described technique can prevent rib fractures and reduce the incidence of intercostal nerve injury. Also, this technique is easy to perform and is effective.

Neurophysiological evaluation of segmental motor neuron function of the thoracic cord in chronic SCI.

STUDY DESIGN: Pilot study. OBJECTIVES: The aim of the study was to develop a neurophysiological method to diagnose the cranial as well as the caudal level of a complete thoracic spinal cord injury (SCI) with higher precision than today's protocols. SETTING: SCI unit Karolinska University Hospital, Stockholm, Sweden. METHODS: Bipolar needle electromyography was recorded in intercostal spaces of five patients with chronic, complete thoracic SCI. Tests were performed during rest, during voluntary activation and during activation of lower body spasticity. Magnetic resonance imaging (MRI) was performed in each patient according to a protocol optimized for imaging near metal implants. RESULTS: Three distinct patterns were found in each patient. Above the lesion we found voluntary activated, normal motor unit potentials (MUPs). At the neurological level and a varying number of segments below, denervated intercostal segments with fibrillation potentials and positive sharp waves appeared. Below the neurological level, normal MUP activated in concert with lower body spasticity was found. The number of denervated segments showed a significant correlation to the length of spinal cord discontinuity on MRI (r=0.97, P<0.05). CONCLUSION: Intercostal neurophysiology in combination with MRI optimized for imaging near metal implants can be used to determine the extent of a chronic complete thoracic SCI, both anatomically and functionally. The described method increases the sensitivity to detect delicate neurological changes related to the dynamic of the pathology that follows SCI and may be useful in analyzing outcome in clinical trials.

Synchronization of presynaptic input to motor units of tongue, inspiratory intercostal, and diaphragm muscles.

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1-8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10-20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.

Recording triggered EMG thresholds from axillary chest wall electrodes: a new refined technique for accurate upper thoracic (T2-T6) pedicle screw placement.

This study was aimed at evaluating the sensitivity and safety of a new technique to record triggered EMG thresholds from axillary chest wall electrodes when inserting pedicle screws in the upper thoracic spine (T2-T6). A total of 248 (36.6%) of a total of 677 thoracic screws were placed at the T2-T6 levels in 92 patients with adolescent idiopathic scoliosis. A single electrode placed at the axillary midline was able to record potentials during surgery from all T2-T6 myotomes at each side. Eleven screws were removed during surgery because of malposition according to intraoperative fluoroscopic views. Screw position was evaluated after surgery in the remaining 237 screws using a CT scan. Malposition was detected in 35 pedicle screws (14.7%). Pedicle medial cortex was breached in 24 (10.1%). Six screws (2.5%) were located inside the spinal canal. Mean EMG threshold was 24.44 ± 11.30 mA in well-positioned screws, 17.98 ± 8.24 mA (p < 0.01) in screws violating the pedicle medial cortex, and 10.38 ± 3.33 mA (p < 0.005) in screws located inside the spinal canal. Below a threshold of 12 mA, 33.4% of the screws (10/30) were malpositioned. Furthermore, 36% of the pedicle screws with t-EMG stimulation thresholds within the range 6-12 mA were malpositioned. In conclusion, assessment of upper thoracic pedicle screw placement by recording tEMG at a single axillary electrode was highly reliable. Thresholds below 12 mA should alert surgeons to suspect screw malposition. This technique simplifies tEMG potential recording to facilitate safe placement of pedicle screws at upper thoracic levels.

The Effect of Continuous Field Block through Intercostal Muscles after Atrial Septal Defect Closure via a Mini-Right Thoracotomy in Pediatric Patients.

BACKGROUND: Postoperative pain management in thoracotomy patients often is difficult. Furthermore, pediatric patients present more challenges because of their inability to effectively communicate their pain intensity. The purpose of this study was to evaluate the use of continuous field block through intercostal muscles as postoperative pain management in pediatric thoracotomy. METHODS: Between 2014 and 2018, 11 patients underwent an ASD closure using a cardiopulmonary bypass via a mini-right thoracotomy through the fourth intercostal space. At the time of chest closure, a single-shot field block via the fourth intercostal muscles was performed with levobupivacaine (0.6 mg/kg). The first five patients were only given the single-shot field block (Single group). The remaining six patients were given levobupivacaine continuously (0.1 mg/kg/hr) through an indwelling catheter until the chest tube removal (Continuous group). The groups' vital signs, total amounts of acetaminophen used, postoperative courses were compared. RESULTS: Although the heart rate did not differ between the groups, the respiratory rate was significantly higher in the Single group versus the Continuous group at 16 and 32 hr post-surgery (35.6 ± 9.7/min vs. 18.5 ± 4.7/min; p=0.007, 43.0 ± 10.4 vs. 25.3 ± 3.1; p=0.042, respectively). The accumulated dosage of acetaminophen given by postoperative day 2 was significantly higher in the Single group versus the Continuous group (55.3 ± 22.1 mg/kg vs. 7.8 ± 17.4 mg/kg; p=0.012). CONCLUSIONS: Continuous field block via intercostal muscles after ASD closure via a mini-right thoracotomy in children was effective to stabilize the vital signs and reduce the analgesic medication use.

Interplay between the inspiratory and postural functions of the human parasternal intercostal muscles.

The parasternal intercostal muscles are obligatory inspiratory muscles. To test the hypothesis that they are also involved in trunk rotation and to assess the effect of any postural role on inspiratory drive to the muscles, intramuscular electromyographic (EMG) recordings were made from the parasternal intercostals on the right side in six healthy subjects during resting breathing in a neutral posture ("neutral breaths"), during an isometric axial rotation effort of the trunk to the right ("ipsilateral rotation") or left ("contralateral rotation"), and during resting breathing with the trunk rotated. The parasternal intercostals were commonly active during ipsilateral rotation but were consistently silent during contralateral rotation. In addition, with ipsilateral rotation, peak parasternal inspiratory activity was 201 +/- 19% (mean +/- SE) of the peak inspiratory activity in neutral breaths (P < 0.001), and activity commenced earlier relative to the onset of inspiratory flow. These changes resulted from an increase in the discharge frequency of motor units (14.3 +/- 0.3 vs. 11.0 +/- 0.3 Hz; P < 0.001) and the recruitment of new motor units. The majority of units that discharged during ipsilateral rotation were also active in inspiration. However, with contralateral rotation, parasternal inspiratory activity was delayed relative to the onset of inspiratory flow, and peak activity was reduced to 72 +/- 4% of that in neutral breaths (P < 0.001). This decrease resulted from a decrease in the inspiratory discharge frequency of units (10.5 +/- 0.2 vs. 12.0 +/- 0.2 Hz; P < 0.001) and the derecruitment of units. These observations confirm that in addition to an inspiratory function, the parasternal intercostal muscles have a postural function. Furthermore the postural and inspiratory drives depolarize the same motoneurons, and the postural contraction of the muscles alters their output during inspiration in a direction-dependent manner.

Relevant surgical anatomy of the chest wall.

The chest wall, like other regional anatomy, is a remarkable fusion of form and function. Principal functions are the protection of internal viscera and an expandable cylinder facilitating variable gas flow into the lungs. Knowledge of the anatomy of the whole cylinder (ribs, sternum, vertebra, diaphragm, intercostal spaces, and extrathoracic muscles) is therefore not only important in the local environment of a specific chest wall resection but also in its relation to overall function. An understanding of chest wall kinematics might help define the loss of function after resection and the effects of various chest wall substitutes. Therefore, this article is not an exhaustive anatomic description but a focused summary and discussion.

BRILMA block for costal cartilage excision: Case report. / Bloqueo BRILMA para extirpación de cartílago costal: caso clínico.

The block of the lateral branches of the intercostal nerves in the middle axillary line (BRILMA) is an interfascial ultrasound-guided block for analgesia in thoracic wall and upper abdominal surgery, presenting as an adequate alternative to neuraxial techniques. We present the case of a 49-year-old female scheduled for idiopathic subglottic stenosis repair with a costal cartilage graft from the 10th rib and tracheotomy. At the end of the surgery, unilateral ultrasound-guided BRILMA block with 20ml of ropivacaine 0.2% was performed at the level of the 6th rib, uneventfully. Postoperatively, the patient referred a maximum level of pain of 3/10. There was no opioid consumption after the 2nd postoperative day, although a subcostal incision may produce considerable pain. BRILMA is a superficial block, easily reproducible in most patients. It diminishes the number of punctures needed in the thoracic wall, as well as the risk for pneumothorax and local anesthetic toxicity.

Evaluation of postoperative pain in patients undergoing modified radical mastectomy with pectoralis or serratus-intercostal fascial plane blocks.

BACKGROUND: Regional nerve blocks are an integral part of multimodal analgesia and should be chosen based on their efficacy, convenience, and minimal side effects. Here, we compare the use of pectoral (PEC II) and serratus-intercostal fascial plane (SIFP) blocks in breast carcinoma cases undergoing modified radical mastectomy (MRM) in terms of the postoperative analgesic efficacy and shoulder mobility. METHODS: The primary outcome of this prospective controlled study was to compare the postoperative static and dynamic pain scores, and the secondary outcome was to assess the shoulder pain, range of shoulder joint motion, and hemodynamic parameters. Sixty patients were randomly allocated to three groups and given general anesthesia. All patients received paracetamol, diclofenac, and rescue doses of tramadol based on the Institute's Acute Pain Service (APS) policy. No block was performed in group C (control), whereas groups P and S received PEC II and SIFP blocks, respectively, before surgical incision. RESULTS: The groups were comparable in terms of age, weight, height, and body mass index distribution (P > 0.05). Dynamic pain relief was significantly better 12 and 24 h postoperatively in groups P (P = 0.034 and P = 0.04, respectively) and S (P = 0.01 and P = 0.02, respectively) compared to group C. Shoulder pain relief and shoulder mobility were better in group S, while the hemodynamic parameters were more stable in group P. CONCLUSIONS: Both SIFP and PEC blocks have comparable dynamic and static pain relief with better shoulder pain scores in patients receiving SIFP.

DNA topoisomerase IIbeta and neural development.

DNA topoisomerase IIbeta is shown to have an unsuspected and critical role in neural development. Neurogenesis was normal in IIbeta mutant mice, but motor axons failed to contact skeletal muscles, and sensory axons failed to enter the spinal cord. Despite an absence of innervation, clusters of acetylcholine receptors were concentrated in the central region of skeletal muscles, thereby revealing patterning mechanisms that are autonomous to skeletal muscle. The defects in motor axon growth in IIbeta mutant mice resulted in a breathing impairment and death of the pups shortly after birth.

Further observations on cardiac modulation of thoracic motoneuron discharges.

Previous analyses of recordings of alpha motoneuron discharges from branches of the intercostal and abdominal nerves in anesthetized cats under neuromuscular blockade demonstrated modulation with the cardiac cycle. This modulation was interpreted as evidence that thoracic somatosensory afferents, most likely muscle spindles, provide a signal to the CNS that could contribute to cardiac interoception. Here, two aspects of these observations have been extended. First, new measurements of thoracic and abdominal EMG activity in spontaneously breathing dogs show that a very similar modulation exists in these rather different circumstances. Second, further analysis of the cat recordings shows that cardiac modulation of the discharges of bulbospinal neurons that transmit the expiratory drive to thoracic motoneurons is weak and of an inappropriate time-course to be a contributor to the effect seen in the motoneurons.

The influence of affective state on respiratory muscle activity.

Measures of neural respiratory drive through the use of electromyography of the parasternal intercostal muscles (EMGpara) are accurate markers of respiratory load and are reflective of pulmonary function. A previous observation of a significant reduction in EMGpara from a first to second measurement occasion was attributed to participants' acclimatization to the laboratory environment and a reduction in anxiety. This study therefore aimed to investigate whether manipulation of participants' affective state would influence EMGpara and related variables. Healthy adult participants underwent measurement of EMGpara and respiratory flow and volume during exposure to four conditions: no stimulus, music, and tense and calm videos. Respiratory rate (RR), raw neural respiratory drive index (rawNRDI, the product of EMGpara in microvolts and RR) and minute ventilation (VE) differed significantly across conditions: RR and VE were significantly higher in the tense condition than all other conditions (all P<0·05); rawNRDI was higher in the tense compared to the calm video condition (P = 0·03). There was also a significant relationship between EMGpara and subjective tension ratings (measured via visual analogue scale) in the tense condition (Spearman's rho = 0·508, P = 0·016), with multivariate modelling indicating significant interactions between rawNRDI and subjective ratings of both tension and calmness. This suggests that anxiety could contribute to elevated respiratory muscle activity and ventilation. Greater consideration should be given to the influence of anxiety when undertaking measurement of respiratory muscle activity to ensure data accurately represent underlying respiratory load.