Relationship between evoked motor response and sensory paresthesia in interscalene brachial plexus block

BACKGROUND AND OBJECTIVES: This study sought to define the relationship between a paresthesia and a motor response (MR) to electrical nerve stimulation using a peripheral nerve stimulator (PNS) during interscalene block. We sought to determine if at a low amperage (< or =1.0 mA) a MR would precede a paresthesia. METHODS: Twenty-two interscalene blocks were performed using insulated needles and a PNS. A MR was obtained at 0.5 mA and then the PNS was turned off. The needle was further advanced until a paresthesia was elicited. The PNS was again turned on, the needle held immobile, and the amperage increased in 0.1 mA increments up to 0.5 mA, or an MR obtained, whichever occurred first. If no MR was obtained, the needle was withdrawn at 0.5 mA in the same direction as it entered until MR was again observed. RESULTS: A MR was obtained at 0.5 mA in all the patients. After the PNS was turned off and the needle further advanced, a paresthesia was elicited in 21 patients. When the PNS was turned on again, a MR was produced at 0 to 0.5 mA in 13 patients. In a subset of 8 patients without a second MR to stimulation up to 0.5 mA, the needle was withdrawn at that amperage. A MR was subsequently obtained during withdrawal in each patient in this subset. CONCLUSIONS: MR preceded paresthesia in every patient. The most likely explanation for this observation is that MR can be achieved at a small distance from the nerve, whereas elicitation of mechanical paresthesia requires either nerve contact or more intimate location of the needle's tip relative to the nerve. Another possible explanation is that motor fibers are located in a more superficial position and are therefore encountered first. Motor and sensory responses are separate and discrete phenomena.     

Partial sensory and motor deficit of ipsilateral lower limb after continuous interscalene brachial plexus block

We describe a partial sensory and motor block of the ipsilateral lower limb after interscalene infusion. After and injection of 20 mL of ropivacaine through the needle, the catheter was advanced 5 cm, and an infusion of ropivacaine 0.2% 5 mL/h commenced. Six hours later, the patient reported a left sensory and motor hemisyndrome, which resolved after the infusion was discontinued. Cervical computed tomography showed the tip of the catheter close to the intervertebral foramen at the C7-T1 level and several intravertebral paramedullar air bubbles. We conclude that the neurological symptoms were caused by an injection of local anesthetic via an interscalene catheter placed in proximity to the epidural space. To avoid this complication, we recommend advancing the catheter no more than 2-3 cm and performing frequent neurological evaluation of patients.     

Successful interscalene block with a nerve stimulator may also result after a pectoralis major motor response

BACKGROUND AND OBJECTIVES: Interscalene block of the brachial plexus is a well-established anesthetic and analgesia technique for shoulder surgery. The endpoint for successful block using the nerve stimulator has been described by previous authors as a bicep motor response (twitch) and recently by a deltoid motor response. This retrospective observational case study of regular clinical practice examined the efficacy of using the pectoralis major motor response as an endpoint for a successful block. METHODS: A total of 120 patients who were scheduled for elective ambulatory shoulder surgery were retrospectively studied. All interscalene blocks were performed with aid of a nerve stimulator. Patients were categorized into 3 groups of 40 patients. Group 1 (biceps twitch), group 2 (deltoid twitch), and group 3 (pectoralis major twitch) were compared on success of the block. This retrospective study was conducted by reviewing interscalene block data sheets from the last 40 patients consecutively receiving interscalene block from either a bicep, deltoid, or pectoralis major motor response. A successful block was defined by the inability of the patient to raise their arm against gravity 20 minutes after injection of the local anesthetic. RESULTS: Pectoralis major motor response as an endpoint for local anesthetic injection was examined. Of 40 patients studied in this group, 38/40 were judged successful. This was comparable to the success rate in biceps (38/40 successful) and deltoid groups (37/40 successful). CONCLUSIONS: This retrospective observational case study of regular clinical practice suggests that a pectoralis major motor response can be a satisfactory endpoint for interscalene block.     

三角肌运动反应用于小儿经肌间沟臂丛神经阻滞的临床观察

目的为三角肌运动反应作为在外周神经刺激器定位下小儿经肌间沟臂丛神经阻滞终点的临床应用提供参考。方法60例拟行上肢手术患儿,在外周神经刺激器定位下行经肌间沟臂丛神经阻滞,随机分为3组:A组(20例),三角肌运动反应终点组;B组(20例),肱二头肌运动反应终点组;C组(20例),三角肌和肱二头肌运动反应终点组。比较各组在刺激域电流、获得终点时间、合作患儿运动阻滞起效时间及神经阻滞效果的差异。结果组间刺激域电流、运动阻滞起效时间、神经阻滞效果差异无统计学意义(P>0.05);A、B组获得终点时间大于C组(P<0.05)。结论三角肌运动反应终点可以作为小儿经肌间沟臂丛神经阻滞穿刺针正确定位的标志。     

成人肌间沟臂丛神经阻滞运动反应终点的研究

目的研究胸大肌、三角肌运动反应作为外周神经刺激器(PNS)定位下成人经肌间沟臂丛神经阻滞终点的可行性。方法择期成人上肢手术240例,PNS定位下行经肌间沟臂丛神经阻滞,随机均分为四组:胸大肌运动反应终点组(A组)、三角肌运动反应终点组(B组)、肱二头肌运动反应终点组(C组)和胸大肌、三角肌或肱二头肌运动反应终点组(D组)。比较组间刺激域电流、获得终点时间、运动阻滞起效时间、各神经分支感觉阻滞起效时间、运动阻滞效果、各神经分支感觉阻滞效果及神经阻滞综合效果。结果D组获得终点时间短于A、B、C组(P<0.05),组间刺激域电流、运动阻滞起效时间、各神经分支感觉阻滞起效时间、运动阻滞效果、各神经分支感觉阻滞效果及神经阻滞综合效果差异无统计学意义。神经阻滞综合优良率90.8%。结论胸大肌、三角肌运动反应终点可作为PNS定位下成人经肌间沟臂丛神经阻滞穿刺针正确定位的满意、安全标志。     

Lateral approach to the sciatic nerve block in the popliteal fossa: correlation between evoked motor response and sensory block

BACKGROUND AND OBJECTIVES: The purpose of this study was to identify which of two motor responses of the foot (plantar flexion versus dorsiflexion) best predicts complete sensory blockade of the sciatic nerve when is used for lateral popliteal sciatic nerve block. METHODS: Thirty American Society of Anesthesiologist physical status I or II patients scheduled for foot and ankle surgery under lateral popliteal sciatic nerve block were enrolled in the study. During each block, the needle was placed to evoke one of the following motor responses of the foot: plantar flexion or dorsiflexion. Thirty milliliters of 0.75% ropivacaine was injected after the motor response was elicited at <0.5 mA. The sequence of elicited motor response was randomized. Sensory blockade of the areas of the foot innervated by the deep peroneal, superficial peroneal, posterior tibial, and sural nerves was checked in a blinded manner. Time required for onset of sensory and motor block of the foot was recorded. RESULTS: The 2 groups were similar with regard to demographic variables and type of surgery. The total of nerves blocked (deep and superficial peroneal, posterior tibial, and sural nerves) after elicited plantar flexion was greater (complete sensory block in 58 of 60 nerve distributions) than after elicited dorsiflexion (34 of 60 nerve distributions) (P <.05). Onset of complete sensory and motor blockade of the foot was faster after elicited plantar flexion (16.6 +/- 5.1 minutes, 20.1 +/- 5.1 minutes, respectively) than after elicited dorsiflexion (24.3 +/- 5.1 minutes, 28.1 +/- 5.0 min, P <.05). CONCLUSIONS: After stimulation of the sciatic nerve, plantar flexion better predicts complete sensory blockade of the foot than dorsiflexion when using the lateral approach to the popliteal fossa. The findings of the present study apply to a single injection of 30 mL of ropivacaine 0.75%.     

No enhancement of sensory and motor blockade by ketamine added to ropivacaine interscalene brachial plexus blockade

BACKGROUND: Ketamine can enhance anesthetic and analgesic actions of a local anesthetic via a peripheral mechanism. The authors' goal was to determine whether or not ketamine added to ropivacaine in interscalene brachial plexus blockade prolongs postoperative analgesia. In addition, we wanted to determine the incidence of adverse-effects in patients undergoing hand surgery. METHODS: Sixty adults scheduled for forearm or hand surgery under the interscalene brachial plexus block were prospectively randomized to receive one of the solutions of the study. Group P received 0.5% ropivacaine 30 ml, group K received 0.5% ropivacaine 30 ml with 30 mg ketamine, and group C received 0.5% ropivacaine with 30 mg ketamine i.v. Loss of shoulder abduction, elbow flexion, wrist flexion and loss of pinprick in the C4-7 sensory dermatomes were assessed at 1-min intervals. Adverse-effects were assessed every 5 min. The duration of the sensory and motor blocks was assessed after operation. Adverse-effects were also recorded. RESULTS: The onset time of sensory or motor blockade and the duration of sensory or motor blockade were similar in all groups. Adverse-effects occurred in 44% of patients in group K and 94% of group C. CONCLUSION: This study suggests that 30 mg ketamine added to ropivacaine in the brachial plexus block does not improve the onset or duration of sensory block, but it does cause a relatively high incidence of adverse-effects. These two findings do not encourage the use of ketamine with local anesthetics for brachial plexus blockade.     

Inability to Consistently Elicit a Motor Response following Sensory Paresthesia during Interscalene Block Administration

Background: Two methods of nerve block based on eliciting neural feedback with the block needle currently exist. The paresthesia technique uses sensory feedback to ascertain that the needle tip is close to the nerve. By contrast, a peripheral nerve stimulator makes use of motor responses to electrical stimulation. The relation of motor responses to an electrical peripheral nerve stimulator and sensory nerve contact (paresthesia) had not been studied.

Methods: Thirty consecutive unpremedicated patients who presented for shoulder surgery with interscalene block anesthesia were prospectively studied. Interscalene block was performed by the single paresthesia method of Winnie, using an insulated or noninsulated needle connected to a peripheral nerve stimulator with the power off. At the precise point of paresthesia, the peripheral nerve stimulator was turned on, and the current was slowly increased to 1.0 mA with a pulse width of 0.2 ms. Presence and location of any motor responses were observed and recorded.

Results: All patients had easily elicited paresthesias. The site of first paresthesia was to the shoulder in 73% of patients. Only 30% of patients exhibited any motor response to electrical stimulation up to 1.0 mA. There was no relation between site of paresthesia and associated motor nerve response.     

Sudden severe postoperative dyspnea following shoulder surgery: Remember inadvertent phrenic nerve block due to interscalene brachial plexus block

Advanced imaging techniques, improved operative techniques, and instrumentation combined with better patient awareness and expectations have resulted in an exponential increase in upper limb surgical procedures during recent times. Surgical teams expect superior analgesia and regional blocks have matched these expectations quite often resulting in improved patient satisfaction and early rehabilitation to achieve best results. Ultrasound-guided interscalene brachial plexus block (ISB) is commonly used to provide analgesia for procedures involving shoulder girdle. We report a case of symptomatic hemi-diaphragmatic paresis (HDP) due to the phrenic nerve block following ISB for arthroscopic sub-acromial decompression of the shoulder presenting as severe postoperative dyspnea. There is strong evidence of HDP following ISB in anesthetic literature, but not reported in related surgical specialties such as orthopedics. We wish to inform upper-limb surgeons and educate junior doctors and other ancillary staff working in upper-limb units to be aware of this serious but reversible complication.     

The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound

BACKGROUND AND OBJECTIVE: Seeking paresthesia and obtaining a motor response to an electrical stimulus are the two most common methods of nerve localization for the performance of peripheral-nerve blocks. However, these two endpoints do not always correlate, and the actual sensitivity and specificity of either method remains unknown. The objective of this study is to determine the sensitivity of paresthesia and motor response to electrical nerve stimulation as tools for nerve localization when a 22-gauge insulated needle is used for the performance of axillary-nerve block. METHODS: After IRB approval and informed consent, 103 patients were enrolled. Real-time ultrasonography was used as the reference test. After needle-to-nerve contact was confirmed by ultrasonography, the patient was requested to report the presence of paresthesia, and a nerve stimulator was used to seek a motor response, with a stimulating current of 0.5 mA or less. RESULTS: One patient was excluded from analysis because of protocol violation. Paresthesia was found to be 38.2% sensitive and motor response was 74.5% sensitive for detection of needle-to-nerve contact. CONCLUSION: The very different and relatively low sensitivity of either technique may explain, in part, the lack of correlation previously reported between the 2 endpoints.     

妇科硬膜外左旋布比卡因最低感觉及运动阻滞浓度

目的 测定妇科手术左旋布比卡因最低感觉及运动阻滞浓度即半数有效浓度(EC50).方法 70例妇科手术患者随机分为感觉组和运动组,每组35例.择L2～3行硬膜外穿刺置管后分次给予预定浓度芹旋布比卡因总量为15 ml:第一例感觉组浓度为0.150%,运动组为0.375%,其后各患者的药物浓度以序贯法进行选择,相邻级别浓度比感觉组为0.980.运动组为0.944.以VAS和改良Bromage评分法分别判断感觉和运动阻滞程度.结果 硬膜外左旋布比卡因感觉阻滞EC50为0.140%(95% CI:0.136%～0.144%),显著低于运动阻滞的EC50 0.385%(95% CI:0.359%～0.414%)(P＜0.01),左旋布比卡因感觉与运动阻滞分离区间是0.140%～0.385%.结论 妇科硬膜外左旋布比卡因感觉和运动阻滞EC50.分别为0.140%和0.385%.     

Comparison of clonidine and tramadol added to prilocaine brachial plexus block - analgesia, sensory and motor block

In a randomized, double-blind study we investigated the effect of clonidine and tramadol added to prilocaine on duration of analgesia, sensory and motor brachial plexus block. 60 patients were randomized in three groups. Group A received 40 ml prilocaine 1,5 % with tramadol 1,5 mg/kg KG, group B 40 ml prilocaine 1,5 % plus clonidine 1,5 microg/kg KG and group C 40 ml prilocaine 1,5 % without any additional medication. We recorded heart rate, blood pressure, oxygen saturation and sedation score at regular intervals. The onset of sensory and motor block was tested every five minutes for thirty minutes. The duration of analgesia, sensory and motor block were evaluated by using a questionnaire. There was no difference between the three groups concerning onset of brachial plexus block and duration of analgesia. But there was a significant prolongation of the duration of sensory and motor block in group B. Haemodynamic parameters remained stable in all patients, there were no significant changes in blood pressure and sedation.