Motor Nerve Block Research Articles

Effects of different doses and concentrations of ropivacaine in axillary brachial plexus block

To evaluate clinic pharmacodynamics of ropivacaine hydrochloride, a new long-acting amide type local anaesthetic, in Chinese patients undergoing neurolysis and tendolysis of forearm through axillary brachial plexus block. Two hundred ASAI-II persons, aged 18-65,weighing 60-75 kg, undergoing neurolysis and tendolysis of forearm under axillary brachial plexus block were randomly assigned to 4 equal groups to received ropivacaine of the doses of 1.00 mg/kg (Group I), 1.25 mg/kg (Group II), 1.50 mg/kg (Group III), and 2.00 mg/kg (Group IV). Each group was subdivided into 5 equal subgroups according to the concentrations (0.15%, 0.20%, 0.25%, 0.30%, and 0.35%). The effects were analyzed. Results There was no significant difference in starting time, consummating time, and persisting time of sensory and motor nerve block between Group I and Group II (all P > 0.05). The starting time and consummating time of Group III and Group IV were all significantly shorter than those of Group I (all P < 0.05), and the persisting times of Groups III and IV were all significantly longer than those of Group I (P < 0.05). 90 minutes after brachial plexus block the degrees of muscle strength Groups I and II were M1 and M2 respectively, hence, the sensory and motor nerves block was in dissociation. When motor never block was above M3 and M4 the interval of brachial plexus block was 55 min and 27 min in Group III and Group IV respectively. Sensory and motor never can be blocked perfectly when the dose of ropivacaine is between 1.5 mg/kg and 2.0 mg/kg and the concentration is between 0.30%-0.35%. When the doses of ropivacaine is 1.25 mg/kg and the concentration is 0.20%-0.25% the starting and consummating time are longer and persisting time is shorter. When the doses of ropivacaine is 1.00 mg/kg and the concentration is 0.15%-0.20% the starting and consummating time are longer and only satisfies external debridement and suture without tourniquets.

Lidocaine Hyperselective Motor Blocks of the Triceps Surae Nerves

This prospective study was designed to evaluate the clinical and gait parameter changes induced by two types of hyperselective motor blocks of the triceps surae nerves (superior soleus and gastrocnemius nerves) and their ability to predict the results of selective tibial neurotomy. Seven adult patients (four males and three females, mean age of 41 yrs old) with spastic foot were included in this study. Clinical (equinus foot score, ankle range of motion, spasticity, pain, and comfort wearing shoes), and gait analysis (kinematic and electromyographic parameters) assessment were performed before and after each motor block (superior soleus nerve and gastrocnemius nerve) and 1 mo after selective tibial neurotomy. The superior soleus nerve block was effective on clinical parameters (triceps surae stretch reflex scores decreased from 2.57 to 0.9, and mean walking time decreased from 44 to 32.1 secs) and on kinematics parameters (the total duration of the gait cycle was decreased because of a reduction of the R3 and swing phases). The same results are observed after soleus neurotomy. This work confirms the practical value of selective superior soleus nerve motor block and that this block provides a useful prediction of the effect of selective soleus neurotomy. It constitutes an additional argument in favor of the predominant role of the soleus in spastic foot.

Anatomic Motor Point Localization of the Biceps Brachii and Brachialis Muscles

Injection of the neurolytic agents into motor points of the biceps brachii or brachialis muscles is an effective treatment of spasticity of the elbow flexors in many stroke survivors. Accurate localization of the motor points of each muscle is necessary for enhancing the efficacy of motor point blocks. To identify the precise locations of the motor points (terminal nerve endings) of the biceps brachii and brachialis muscles in relation to anatomic surface landmarks for motor point blocks, we dissected 23 limbs from 12 cadavers. A reference line was defined as a line connecting the coracoid process with the lateral epicondyle of the humerus. The location of the motor points of the biceps brachii and brachialis muscles was identified in reference to the reference line. The motor point of the biceps brachii muscle was found to be approximately half of the reference line. In the brachialis muscle, the location of the motor point was 70% of the reference line from the coracoid process and 2 cm medial to the line. The results are expected to facilitate effective localization of the motor point block of these muscles in selective motor nerve block.

Local Anesthetics in Lipid-Depot Formulations—Neurotoxicity in Relation to Duration of Effect in a Rat Model

The aim of this study was to investigate the possible local neurotoxicity of a number of lipid-depot formulations of local anesthetics in relation to their duration of action in sciatic-nerve block. Formulations that contain 2%, 4%, 8%, 16%, 32%, or 64% of a mixture of bupivacaine and lidocaine base 4:1 in medium-chain triglyceride were prepared and evaluated, together with 0.5%, 1.0%, and 2.0% bupivacaine HCl solutions, bupivacaine 4.2% or 7.0% in medium-chain triglyceride, and 20% lidocaine base in a polar lipid vehicle. The duration of sensory and motor sciatic-nerve block was determined in rats. A week later, the sciatic nerves were dissected and removed for histopathologic examination by light microscopy. The duration of sensory and motor-nerve block was prolonged almost 4 times with the 32% and 13 times with the 64% bupivacaine:lidocaine formulation, in comparison to the 0.5% aqueous solution. The 64% formulation was applied by injection and also placed directly on the nerve with similar results. Slight to moderate signs of neurotoxicity were only found after administration of the 64% formulation. The findings suggest that depot formulations of local anesthetics with advantageous pharmaceutical and pharmacologic properties can be prepared by use of bupivacaine as the active component and natural lipids as carriers. A favorable balance between effects and toxicity may conceivably be obtained. After supplemental testing in more sensitive models for toxicity, such formulations could be candidates for clinical trials.

Magnesium as an adjuvant to prilocaine prolongs sensory and motor nerve block after forearm and hand surgery,

Magnesium as an adjuvant to prilocaine prolongs sensory and motor nerve block after forearm and hand surgery,

Magnesium Added to Prilocaine Prolongs the Duration of Axillary Plexus Block

The aim of this study was to evaluate the effect of the addition of magnesium to prilocaine on the duration of sensory and motor-nerve block. After institutional approval, 60 ASA physical status I and II patients, between 18 and 60 years of age and scheduled for forearm and hand surgery under axillary brachial plexus block, were included in the study. Patients were randomly assigned to 1 of 4 groups. All of the patients received 5 mg/kg of 2% prilocaine and isotonic sodium chloride solution in 35 mL total volume for axillary brachial plexus block. Group I received intravenous saline, and group II received 150 mg intravenous magnesium at the same time as local anesthetic administration. In group III, 100 mg of magnesium, and in group IV, 150 mg of magnesium, were added to local anesthetic solution. Sensory block and motor block of musculocutaneous, radial, median, and ulnar nerves were recorded at 5-minute intervals. The duration of motor block was significantly longer in group IV than in other groups (167 +/- 30, 177 +/- 17, 180 +/- 20, and 250 +/- 19 minutes in groups I to IV, respectively) (P < .01). Mean duration of sensory block in both of the perineural magnesium groups was statistically different than in groups I and II (P < .001). Duration of sensory block in group IV (304 +/- 30 minutes) was significantly longer than in group III (253 +/- 23 minutes) (P < .001). The admixture of magnesium to prilocaine for axillary brachial plexus block provided a pronounced prolongation of sensory and motor block without side effects.

Surgery in the Peripheral Nerves for Lower Limb Spasticity

Introduced by Stoffel in 1912 for the treatment of spastic foot drop, selective neurotomy consists of partial section of the motor branches to the muscles causing excessive spasticity. This peripheral surgery for spasticity is based on two main concepts. First, spinal reflexes and muscles are heterogeneous, and their regional organization depends on their role during normal movements. This fact is the physiological basis for focal spasticity and peripheral treatment. Second, there is a differential reinnervation after partial section, leading to motor recovery without spindle reinnervation (therefore without spasticity). A careful clinical assessment must be conducted before a neurotomy is performed. What kind of spasticity does the patient have? What is the goal (functional or comfort)? Surgery can be mimicked by motor nerve blocks (anesthetic drugs) to give patients an idea of the expected surgical outcome. Many types of neurotomies have been described for the lower and upper limbs, depending on the patient’s clinical status. The most common neurotomy is the tibial neurotomy for spastic foot drop.

Comparison of Sensory and Motor Nerve Block in Epidural Anesthesia Using a Different Concentrations of Ropivacaine for Cesarean Section

Background: The aim of this study was to evaluate the sensory and motor nerve block achieved by epidural anesthesia using 0.475% ropivacaine and 0.75% ropivacaine. Methods: Fifty-six patients undergoing cesarean section were randomly allocated to group I (0.75% ropivacaine) or group II (0.475% ropivacaine). We assessed changes in sensory and motor block using the Bromage scale over 180 minutes after epidural anesthesia. The incidence of nausea, vomiting and the total dosage of ephedrine used were also recorded. Sensory changes, motor blockade and the total dosage of ephedrine used were compared using the t-test (P ＜ 0.05). Results: No significant differences were found between the two groups at the sensory block level except at 30 and 60 minutes after epidural anesthesia. However, the motor blockade of group I was significantly more intense than that of group II at 15, 20, 25, 30, 60, 120 and 180 minutes after epidural anesthesia. No significant differences were observed between the two groups in the incidences of nausea, vomiting or the total dosage of ephedrine used. Conclusions: The use of 0.475% ropivacaine instead of 0.75% ropivacaine in epidural anesthesia for cesarean section did not reduce the incidence of nausea, vomiting or the total dosage of ephedrine used. The sensory block achieved using 0.75% ropivacaine was similar, but the motor blockade achieved using 0.475% ropivacaine was less intense with a shorter duration and an earlier recovery to normal than that of 0.75% ropivacaine. These results suggest that 0.475% ropivacaine may be more useful in epidural anesthesia for cesarean section than 0.75% ropivacaine.

Electromyographic assessment of ulnar nerve motor block induced by lidocaine

Study Objective: To determine the differences in the onset time and duration of motor block produced by lidocaine 1% and lidocaine 2% via a quantitative and objective method, the measurement of compound muscle action potentials (CMAPs). Study Design: Prospective study. Setting: Main operating rooms of a university hospital. Patients: 20 consecutive patients undergoing surgery not requiring intraoperative muscle relaxation. Interventions: General anesthesia with unilateral ulnar nerve block was administered. In patients’ nondominant (experimental) arms, an insulated block needle was placed adjacent to the ulnar nerve at the wrist while continuous nerve stimulation was delivered to ensure its proper placement. Through this needle, lidocaine 1% or lidocaine 2% was injected. The dominant (control) arm received no injection. Measurements and Main Results: Monitoring of ulnar nerve-evoked CMAPs was performed simultaneously on both arms. Ulnar nerve function was assessed at baseline and then at 10-second intervals by automatically measuring the amplitude of the evoked CMAPs on a two-channel electromyogram. The mean (± SEM) baseline CMAP amplitude prior to injection of lidocaine 1% was 3.10 ± 0.87 mV and 3.06 ± 0.89 mV for the experimental and control ulnar nerves, respectively ( p = NS); for lidocaine 2%, baseline CMAP amplitude was 3.58 ± 1.39 mV and 3.70 ± 1.46 mV, respectively ( p = NS). Over the course of the study, the control CMAP amplitude varied by <12%. At the experimental ulnar nerve, 90% CMAP decrease after injection of lidocaine 1% and lidocaine 2% occurred 7.5 ± 2 minutes and 5 ± 1.5 minutes, respectively ( p = NS), whereas maximal blockade was achieved after 15 ± 3 minutes and 11 ± 5 minutes, respectively ( p = NS). Recovery of CMAP to 90% of baseline occurred 184 ± 31 minutes after injection of lidocaine 1% and 248 ± 30 minutes following lidocaine 2% ( p = NS). Conclusion: The present study describes a technique that can be used in vivo to objectively measure the speed of onset and duration of local anesthetic-induced motor blockade. Although statistically not different, lidocaine 2% demonstrated a faster onset and longer duration of ulnar nerve motor block than lidocaine 1%.

The parasacral sciatic nerve block

The clinical utility of a new parasacral approach for conduction block of the sciatic nerve was investigated, with critical examination of onset, extent, and success rates when this block was used for surgical procedures below the knee. Thirty ASA I-III patients presenting for surgery on the lower limb were enrolled. All received 30 mL of 1.5% lidocaine with 1:200,000 epinephrine following nerve stimulator identification of the sciatic nerve at < or =0.2 mA or less. Trans-sartorial saphenous nerve blocks were performed to provide anesthesia to the medial leg. Overall success for surgical anesthesia with this block was 97%. All components of the sacral plexus could be blocked with this approach, and 93% of patients displayed evidence of obturator nerve motor block. However, no patient displayed evidence of obturator sensory anesthesia that could be mapped. Saphenous nerve blocks were 100% effective in providing surgical anesthesia for the procedures performed. The parasacral approach to the sciatic nerve exhibits a high success rate, resulting in anesthesia of the entire sacral plexus and generally in motor block of the obturator nerve was an interesting observation.

TREATMENT OF ACQUIRED MUSCLE SPASTICITY USING PHENOL PERIPHERAL NERVE BLOCKS

The use of phenol motor nerve blocks is advantageous in the early period of acquired spasticity (ie, that occurring following traumatic brain injury or incomplete spinal cord injury), when increased muscle tone is often the most severe. Because acquired spasticity is dynamic and usually improves slowly, a temporary treatment method used to ameliorate increased muscle tone is desirable. Phenol nerve infiltration provides a temporary motor nerve block that lasts for weeks or months. It allows passive limb mobilization in a comprehensive rehabilitation program that attempts to prevent fixed soft tissue contractures. Permanent or irreversible methods such as operative tendon lengthening, muscle release or recession, or neurectomy are usually best delayed until the spasticity has become static, when the need for surgical correction becomes more firmly indicated, and outcomes of operative intervention are more predictable. Although phenol nerve blocks were initially administered at the spinal cord level to control spasticity, the potential side effects have caused a loss of popularity of this method of administration. The safer and more common use of phenol infiltration at the peripheral nerve level is now more accepted for brain injury and spinal cord injury patients. This report reviews the indications, current concepts, and development of the different methods used to administer phenol nerve blocks. Comparisons to other methods to control spasticity are discussed.

A Comparison of Etidocaine and Lidocaine for Retrobulbar Anesthesia

In this double-blind study of retrobulbar block for cataract surgery, 62 patients scheduled for cataract surgery were randomly assigned to treatment with either (1) lidocaine 2% with epinephrine 1:200,000 (21 patients); (2) etidocaine 1% plain (20 patients); or (3) etidocaine 1% with epinephrine 1:200,000 (21 patients). The time of onset of sensory and motor block after administration of the three drugs was the same. The duration of motor nerve block produced by etidocaine plain and by etidocaine with epinephrine was considerably longer than that produced by lidocaine with epinephrine, and fewer patients reported postoperative pain after either etidocaine plain or etidocaine with epinephrine than after lidocaine with epinephrine.

The use of local anaesthetics to produce prolonged motor nerve block in the study of denervation hypersensitivity.

1. Silastoseal cuffs containing 25% and 45% lignocain, 25% marcain and 25% NaCl were placed onto the sciatic nerve. The effects of this on the sciatic nerve as well as the soleus and extensor digitorum longus (EDL) muscles was studied. 2. Cuffs containing local anaesthetics caused both early and late phases of paralysis, cuffs containing NaCl caused only the late phase of paralysis, showing that the late phase of paralysis was not due to the anaesthetic properties of the drugs. The paralysis produced by these procedures was irreversible. 3. Responses to indirect and direct stimulation of soleus and EDL muscles were compared to assess the degree of denervation. In case of cuffs containing 25% marcain and 45% lignocain more than half of the muscle fibres were denervated. 4. Acetylcholine sensitivity was assesses in all experiments. Soleus and EDL muscles from all animals that had cuffed nerves containing either local anaesthetics or 25% NaCl were hypersensitive to ACh. The degree of hypersensitivity could be correlated to the degree of "denervation" as assessed by comparing the directly and indirectly elicited twitch tensions. 5. It was found that the sciatic nerve undergoes degenerative changes when exposed to cuffs containing either local anaesthetics or 25% NaCl.

Oral motor nerve block: some implications for research in speech.

The effects of a bilateral hypoglossal nerve block on speech, and possible implications of the technique for research in speech pathology, are discussed. The risks involved are essentially the same as those associated with sensory nerve blocks when performed by someone well-trained in the administration of regional anesthesia.