Regional anesthesia considerations for cardiac surgery.

Pain is a significant consequence of cardiac surgery and newer techniques in cardiac anesthesia have provided an impetus for the development of multimodal techniques to manage acute pain in this setting. In this regard, regional anesthesia techniques have been increasingly used in many cardiac surgical procedures, for the purposes of reducing perioperative consumption of opioid agents and enhanced recovery after surgery. The present investigation focuses on most currently used regional techniques in cardiac surgical procedures. These regional techniques include chest wall blocks (e.g., PECS I and II, SAP, ESB, PVB), sternal blocks (e.g., TTMPB, PSINB), and neuraxial blocks (e.g., TEA, high spinal anesthesia). The present investigation also summarizes indications, technique, complications, and potential clinical benefits of these evolving regional techniques. Cardiac surgery patients may benefit from application of these regional techniques with well controlled indications and careful patient selections.

The effect of lateral pectoral nerve sparing technique and radiotherapy on the pectoralis major muscle applied with modified radical mastectomy.

BACKGROUND/OBJECTIVE: The aim of this study was to evaluate with electromyography (EMG) the effect of lateral pectoral nerve sparing technique (LPNST) and radiotherapy (RT) on the lateral pectoral nerve (LPN) in patients applied with modified radical mastectomy (MRM). METHODS: The study included 66 patients who underwent MRM surgery. The patients were separated into 2 groups as those applied with LPNST and those who underwent standard surgery (Control group). Within these 2 groups, patients were again separated as those who received or did not receive RT. The EMG evaluations were made by a neurology specialist blinded to the patient groups. RESULTS: The mean age of the patients was 53.3 ± 10.6 years. Standard surgery was applied to 33 (50%) patients and LPNST to 33 (50%) patients, RT was applied to 32 (48.5%) patients and not to 34 (51.5%) patients. In the EMG evaluation, latency was 2.1 ms (1.4-3.2) in the LPNST and 3.7 ms (1.9-12.4) in the control (p <0.001) and amplitude values were 9650 mV (3120-36900) in the LPNST and 4780 mV (510-12.4) in the control (p <0.001). The latency values in the Control receiving and not receiving RT were 4.0 ms (1.9-12.4) and 2.6 ms (1.9-6.2) respectively (p <0.05). The latency values of the patients receiving and not receiving RT in the LPNST were 2.2 ms (1.8-3.2) and 2.0 ms (1.4-2.4) respectively (p <0.05). In the Control and LPNST Group, no significant difference was determined between receiving and not receiving RT groups in respect of amplitude values (p >0.05). CONCLUSION: The results of this study demonstrated that electromyographically the latency and amplitude values were better protected in the LPNST group. It was also seen that RT increased the formation of nerve damage in both groups.

Efficacy of Pectoral Nerve Block Type II for Breast-Conserving Surgery and Sentinel Lymph Node Biopsy: A Prospective Randomized Controlled Study.

Objectives: The pectoral nerve block type II (PECS II block) is widely used for postoperative analgesia after breast surgery. This study evaluated the analgesic efficacy of PECS II block in patients undergoing breast-conserving surgery (BCS) and sentinel lymph node biopsy (SNB). Methods: Patients were randomized to the control group (n=40) and the PECS II group (n=40). An ultrasound-guided PECS II block was performed after induction of anesthesia. The primary outcome measure was opioid consumption, and the secondary outcome was pain at the breast and axillary measured using the Numerical Rating Scale (NRS) 24 hours after surgery. Opioid requirement was assessed according to tumor location. Results: Opioid requirement was lower in the PECS II than in the control group (43.8 ± 28.5 µg versus 77.0 ± 41.9 µg, p < 0.001). However, the frequency of rescue analgesics did not differ between these groups. Opioid consumption in the PECS II group was significantly lower in patients with tumors in the outer area than that in patients with tumors in the inner area (32.5 ± 23.0 µg versus 58.0 ± 29.3 µg, p=0.007). The axillary NRS was consistently lower through 24 hr in the PECS II group. Conclusion: Although the PECS II block seemed to reduce pain intensity and opioid requirements for 24 h after BCS and SNB, these reductions may not be clinically significant. This trial is registered with Clinical Research Information Service KCT0002509.

Should thoracic paravertebral blocks be used to prevent chronic postsurgical pain after breast cancer surgery? A systematic analysis of evidence in light of IMMPACT recommendations.

The role of thoracic paravertebral block (PVB) in preventing chronic postsurgical pain (CPSP) after breast cancer surgery (BCS) has gained interest, but existing evidence is conflicting, and its methodological quality is unclear. This meta-analysis evaluates efficacy of PVB, compared with Control group, in preventing CPSP after BCS, in light of the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) recommendations. Electronic databases were searched for randomized trials comparing PVB with Control group for CPSP prevention after BCS. Eligible trials were assessed for adherence to IMMPACT recommendations. The primary outcomes were CPSP at 3 and 6 months, whereas secondary outcomes were PVB-related complications. Data were pooled and analyzed using random-effects modelling. Trial sequential analysis was used to evaluate evidence conclusiveness. Data from 9 studies (604 patients) were analyzed. The median (range) of IMMPACT recommendations met in these trials was 9 (5, 15) of 21. Paravertebral block was not different from Control group in preventing CPSP at 3 months, but was protective at 6 months, with relative risk reduction (95% confidence interval) of 54% (0.24-0.88) (P = 0.02). Meta-regression suggested that the relative risk of CPSP was lower when single-injection (R = 1.00, P < 0.001) and multilevel (R = 0.71, P = 0.01) PVB were used. Trial sequential analysis revealed that 6-month analysis was underpowered by at least 312 patients. Evidence quality was moderate according to the GRADE system. Evidence suggests that multilevel single-injection PVB may be protective against CPSP at 6 months after BCS, but methodological limitations are present. Larger trials observing IMMPACT recommendations are needed to confirm this treatment effect and its magnitude.

Nerve stimulator-guided repetitive paravertebral block for thoracic myofascial pain syndrome.

Myofascial pain syndrome (MPS) may persist for many years and is often refractory to traditional therapeutic approaches including pharmacotherapy, focal tenderness infiltration by local anesthetic and corticosteroids, physical therapy and behavioral modification. This report describes three cases of MPS following coronary artery bypass graft, inadequate positioning during abdominal hysterectomy, and excessive physical effort refractory to conventional therapeutic approaches. Three patients were successfully treated with repeated nerve stimulator-guided paravertebral block using a mixture of bupivacaine and clonidine. Physical examinations including a complete neurological assessments were unremarkable. Relevant diagnostic imaging (X-ray, magnetic resonance imaging, computed tomography) and laboratory evaluations also failed to demonstrate any significant structural disorders or systemic diseases that might have been responsible for their pain. Nerve stimulator-guided paravertebral block was performed at the dermatomes corresponding to the thoracic myofascial pain region. Each point was injected with 4 mL of the local anesthetic solution. If the pain returned, a second paravertebral block was performed. The three patients were pain-free over a follow-up period up to 2 years. Our report suggests that nerve stimulator-guided paravertebral blockade could be a useful treatment for MPS refractory to traditional therapeutic approaches.

Long thoracic nerve: anatomy and functional assessment.

BACKGROUND: The anatomy and function of the long thoracic nerve are not fully understood. The purposes of this study were to clarify the anatomy of the long thoracic nerve and to propose a clinical test to assess the function of the upper division of the long thoracic nerve. METHODS: The long thoracic nerve and the serratus anterior muscle were studied in fifteen fresh cadavera. Six patients had an operation to treat a brachial plexus injury, and the long thoracic nerve was electrically stimulated. The resulting shoulder motion was then observed. RESULTS: The long thoracic nerve was formed by branches arising from the C5, C6, and C7 nerve roots. The C5 and C6 branches joined beneath the scalenus medius muscle to form the upper division of the long thoracic nerve, which was located 1 cm posteriorly and superiorly to the upper trunk origin. The union of the upper division with the branch from C7 occurred caudally, in the axillary region. Two branches from the upper division of the long thoracic nerve to the upper portion of the serratus anterior muscle were consistently identified. After electrical stimulation of the upper division branches, shoulder protraction was observed. CONCLUSIONS AND CLINICAL RELEVANCE: In the supraclavicular region, the long thoracic nerve has a trajectory parallel to the brachial plexus, which is contrary to the schematic representation in most textbooks. The upper division of the long thoracic nerve can be assessed by the shoulder protraction test.

Sonographic mapping of the normal brachial plexus.

BACKGROUND AND PURPOSE: Mapping of the brachial plexus with MR imaging has been reported and may have potential clinical applications (eg, precise localization of traumatic or tumoral nerve lesions, selective anesthesia of the brachial plexus). We sought to demonstrate that mapping of the brachial plexus may be performed by means of sonography. METHODS: Twelve healthy adult volunteers (seven women and five men; age range, 24-38 years; mean, 31 years) underwent bilateral sonographic examination for the assessment of the nerve structures of the brachial plexus from the extraforaminal part to the axillary part. Four formolated cadavers (two male and two female; age range, 66-84 years; mean, 77.5 years) were frozen and sawed into 3-mm-thick contiguous sections in the same plane as that used for the sonographic exploration. RESULTS: A satisfactory sonographic examination was performed in 10 of 12 volunteers, leading to a good association with anatomic sections. Two volunteers were excluded from the study because a clear depiction of the brachial plexus was difficult owing to a short neck and low echogenicity at examination. The association between sonographic images and anatomic sections allowed us to map the brachial plexus. The subclavian and deep cervical arteries were useful landmarks for this mapping. The eighth cervical nerve root and the first thoracic nerve root were the most difficult part of the brachial plexus to depict because of their deep location. CONCLUSION: The brachial plexus can be mapped with sonography. However, this technique requires a good grounding in anatomy and may be impossible in short-necked individuals.

Repetitive stimulation of the long thoracic nerve in myasthenia gravis: clinical and electrophysiological correlations.

OBJECTIVE: To investigate repetitive stimulation of the long thoracic nerve as a reliable and technically undemanding method for evaluating respiratory muscle function in myasthenia gravis. METHODS: 15 patients with myasthenia gravis and positive single fibre electromyography had repetitive stimulation of the long thoracic nerve together with serratus anterior recordings. There were 20 normal controls. RESULTS: Eight patients with respiratory symptoms all had abnormal results, with an increased response decrement. These patients required intensive monitoring and supplemental oxygen. The remaining seven cases with no respiratory symptoms all had negative studies. CONCLUSIONS: This is a simple well tolerated method that shows good correlation with respiratory symptoms and management requirements in myasthenia gravis. It can alert the physician to serious respiratory complications in this disease.

Right vagal nerve stimulation for coronary anastomosis without cardiopulmonary bypass: investigation in dogs.

BACKGROUND: The purpose of this study is to assess the potential of right vagal nerve stimulation for reducing the heart rate during coronary anastomosis without cardiopulmonary bypass. METHODS: Through the fourth left intercostal space, left internal thoracic artery grafts were sutured to the left anterior descending artery with the heart beating. In Group I (n=7), two dogs underwent right cervical vagal stimulation alone and five dogs underwent right cervical vagal stimulation during intravenous infusion of diltiazem or verapamil. In Group II (n=3), one dog underwent right thoracic vagal stimulation alone and two dogs underwent right thoracic vagal stimulation during intravenous infusion of diltiazem or verapamil. The thoracic vagal nerve was isolated endoscopically. The electrocardiogram and aortic pressure were monitored during interventions. RESULTS: In Group I, cervical vagal stimulation reduced the heart rate from 190 to 45 and 180 to 42 b/min. During intravenous infusion of diltiazem or verapamil, cervical vagal stimulation caused ventricular arrest. In Group II, thoracic vagal stimulation decreased the heart rate from 205 to 70 b/min, and stimulation during intravenous infusion of diltiazem caused ventricular arrest. CONCLUSIONS: Right vagal stimulation during intravenous infusion of diltiazem or verapamil has potential value as a technique for reducing the heart rate during coronary anastomosis without cardiopulmonary bypass.

Right vagal nerve stimulation during minimally invasive direct coronary artery bypass grafting in dogs. A preliminary study.

BACKGROUND: Minimal access coronary artery bypass grafting without cardiopulmonary bypass has been used with increasing frequency. However, some surgeons are still unwilling to perform MIDCAB because the anastomosis is technically demanding. The aim of this study was to assess whether autonomic activation via right vagal nerve stimulation will be an effective support technique on heart rate during MIDCAB in dogs. EXPERIMENTAL DESIGN: Preliminary study. SETTING: Cardiothoracic Surgery Unit, University Clinic. METHODS: The right cervical vagal nerve was stimulated in five dogs. In one dog, right thoracotomy was performed to isolate the vagal nerve. Bipolar hook electrodes were attached to the vagal nerve. The vagal nerve was stimulated (3-5 mA, 40 Hz) for a few seconds while suturing the coronary artery. Experiments were conducted in two groups. In Group I, two dogs received vagal stimulation via the right neck, and one dog received vagal stimulation via the right thoracic cavity approach. In Group H, all vagal stimulations were performed via the neck during intravenous infusion of diltiazem (10 mg/hrs) or verapamil (5 mg/hrs). RESULTS: In Group I, when the cervical nerve stimulation started the heart rate decreased from 190 to 45 beats/min in one dog, and from 180 to 42 beats/min in another dog. During thoracic nerve stimulation, the heart rate decreased from 205 to 70 beats/min. In Group II, vagal stimulation of one dog (10 mg/hr diltiazem) caused ventricular arrest, and in the other dogs (5 mg/hr verapamil) vagal stimulation caused marked bradycardia with atrioventricular block. After the cessation of nerve stimulation, the heart rate returned to normal sinus rhythm immediately in each dog. CONCLUSIONS: Based on our findings, this type of autonomic stimulation (especially with i.v. administration of diltiazem or verapamil) can be an effective technique in reducing heart beats, thus obtaining relatively quiet surgical field for coronary anastomosis in CABG without cardiopulmonary bypass.

Neurotization of the remaining latissimus dorsi muscle following muscle flap transplant.

The neurotization of the remaining latissimus dorsi muscle at the donor site is a useful technique in children. It is performed during the same surgical procedure as the free vascularized flap and consists of a neurolysis of the thoracodorsal nerve into three to five fascicles, and introducing them into three to five different openings in the muscle fibers. This technique is important in young patients for avoiding functional long-term sequelae such as scoliosis and developmental muscular defects of the vertebral column. Three cases are reported, with evaluation by electromyography and biopsy.

Effect of vagotomy and thoracic sympathectomy on responses of the monkey to water immersion.

Cardiopulmonary stretch receptors have been implicated as part of a reflex mechanism linking changes in blood volume to changes in renal excretion. Experiments were performed to determine whether total denervation of these receptors by combined cervical vagotomy and thoracic sympathectomy affects the renal responses of the monkey to head-out water immersion, a maneuver that translocates blood to the thorax and elicits an increase in renal salt and water excretion. Macaca fascicularis monkeys first underwent chronic bilateral thoracic sympathectomy or sham denervation performed in two stages a week apart. One to two weeks later, they were anesthetized with pentobarbital sodium, and the sympathectomized animals underwent bilateral cervical vagotomy. Control renal function did not differ between the two groups. Immersion of 90-min duration increased central venous and mean arterial pressures by similar amounts in both groups, but heart rate increased only in the sham-denervated animals. Denervation did not affect the magnitudes or delay the times of onset of the increases in urine flow, absolute and fractional sodium excretion, and osmolar and free water clearances occurring with immersion. These results demonstrate that in the anesthetized monkey cardiopulmonary receptors are not necessary for eliciting the renal responses to immersion.

Cockroach molting. II. The nature of regeneration-induced delay of molting hormone secretion.

1. The amount of regenerating limb tissue does not control the length of molting delay in cockroaches; rather, a programmed delay associated with each autotomy level and segment allows an appropriate delay for accomplishing the necessary regeneration. 2. Delay of molting is accomplished by inhibiting ecdysiotropin release. 3. Each regenerating limb produces a delay independent of other regenerating limbs. 4. Single and simultaneous double autotomies can be used to obtain substantially increased synchrony of the molting cycle of a wide variety of cockroach species. 5. The signal to delay molting is transmitted to the brain along the ventral nerve cord and requires the stereotyped sensory input associated with autotomy to initiate it. 6. There are two phases of ecdysone titer increase during the molting cycle of cockroaches. An early transitory or gradual increase is associated with the regeneration critical period, while a later major peak is associated with apolysis. The major ecdysone peak was shown to be delayed during leg regeneration.