[show abstract][hide abstract] ABSTRACT: The lack of reported complications related to lower extremity peripheral nerve blocks (PNBs) may be related to the relatively infrequent application of these techniques and to the fact that most such events go unpublished. Our current understanding of the factors that lead to neurologic complications after PNBs is limited. This is partly the result of our inability to conduct meaningful retrospective studies because of a lack of standard and objective monitoring and documentation procedures for PNBs. We report a case of permanent injury to the sciatic nerve after sciatic nerve block through the anterior approach and discuss mechanisms that may have led to the injury. Intraneural injection and nerve injury can occur in the absence of pain on injection and it may be heralded by high injection pressure (resistance).
[show abstract][hide abstract] ABSTRACT: It has been suggested that use of peripheral nerve blocks (PNBs) may have some potential benefits in the outpatient setting. There have been no studies specifically comparing PNBs performed with short-acting local anesthetics with general anesthesia (GA) in patients undergoing outpatient knee surgery. We hypothesized that a combination of lumbar plexus and sciatic blocks using a short-acting local anesthetic will result in shorter time-to-discharge-home as compared with GA. Patients scheduled to undergo knee arthroscopy were randomized to receive a GA (midazolam, fentanyl, propofol, N(2)O/O(2)/desflurane via laryngeal mask airway) or lumbar plexus/sciatic block (PNBs; 2-chloroprocaine). Patients given GA also received an intraarticular injection of 20 mL 0.25% bupivacaine for postoperative pain control. Patients in the PNB group were given midazolam (up to 4 mg) and alfentanil (500-750 microg) before block placement and propofol 30-50 microg . kg(-1) . min(-1) for intraoperative sedation. Relevant perioperative times, postanesthesia care unit bypass rate, severity of pain, and incidence of complications were compared between the two groups. Fifty patients were enrolled in the study; 25 patients each received GA or PNBs. Total operating room time did not differ significantly between the 2 groups (97 +/- 37 versus 91 +/- 42 min). Seventy-two percent of patients receiving PNB met criteria enabling them to bypass Phase I postanesthesia care unit compared with only 24% of those receiving GA (P < 0.002). Time to meet criteria for discharge home (home readiness) and time to actual discharge were significantly shorter for patients given PNBs than for patients given GA (131 +/- 62 versus 205 +/- 94 and 162 +/- 71 versus 226 +/- 96, respectively). Under the conditions of our study, the combination of lumbar plexus and sciatic blocks with 2-chloroprocaine 3% was associated with a superior recovery profile compared with GA in patients having outpatient knee arthroscopy.
[show abstract][hide abstract] ABSTRACT: General anesthesia (GA) and brachial plexus block have been used successfully for surgery on the upper extremities. Controversy exists as to which method is more suitable in outpatients undergoing hand and wrist surgery. The authors hypothesized that infraclavicular brachial plexus block (INB) performed with a short-acting local anesthetic would result in shorter time to discharge home as compared with "fast-track" GA.
After obtaining written informed consent, 52 patients (aged 18-65 yr, American Society of Anesthesiologists physical status I-III) were randomly assigned to receive either an INB or GA under standardized protocols (INB = 3% 2-chloroprocaine + HCO3 + epinephrine 1:300000, followed by propofol sedation; GA = 12.5 mg dolasetron, propofol induction, followed by laryngeal mask airway insertion and desflurane for maintenance; 0.25% bupivacaine for wound infiltration). At the conclusion of the procedure, nurses blinded to the study goals and the anesthetic technique used a modified Aldrete score to decide whether patients could bypass the postanesthesia care unit. Additional data were collected regarding time to postoperative pain, ambulation, home readiness, and incidence of adverse events.
More patients in the INB group (79%) met the criteria to bypass the postanesthesia care unit compared with patients in the GA group (25%; P < 0.001). Compared with patients in the GA group, fewer patients in the INB group had pain (visual analog scale score > 3) on arrival to the postanesthesia care unit (3% vs. 43%; P < 0.001). None of the patients in the INB group requested treatment for pain while in the hospital, compared with 48% of patients in the GA group (P < 0.001). Patients in the INB group were able to ambulate earlier (82 +/- 41 min) compared with those in the GA group (145 +/- 70 min; P < 0.001). Time to home readiness and discharge times were shorter for patients in the INB group (100 +/- 44 and 121 +/- 37 min) compared with those in the GA group (203 +/- 91 and 218 +/- 93 min; P < 0.001). Adverse events (e.g., nausea, vomiting, sore throat) occurred less frequently in patients undergoing INB as compared with those undergoing GA.
Infraclavicular brachial plexus block with a short-acting local anesthetic was associated with time-efficient anesthesia, faster recovery, fewer adverse events, better analgesia, and greater patient acceptance than GA followed by wound infiltration with a local anesthetic in outpatients undergoing hand and wrist surgery.
[show abstract][hide abstract] ABSTRACT: Background: General anesthesia (GA) and brachial plexus block have been used successfully for surgery on the upper extremities. Controversy exists as to which method is more suitable in outpatients undergoing hand and wrist surgery. The authors hypothesized that infraclavicular brachial plexus block (INB) performed with a short-acting local anesthetic would result in shorter time to discharge home as compared with “fast-track” GA.
[show abstract][hide abstract] ABSTRACT: Recommendations regarding the technical aspects of nerve stimulator-assisted nerve localization are conflicting. The objectives of this study were to determine whether the placement of the cutaneous electrode affects nerve stimulation and to determine the duration and intensity of an electrical stimulus that allows nerve stimulation with minimal discomfort.
Ten healthy volunteers underwent an interscalene and a femoral nerve block. After obtaining a clearly visible motor response of the biceps (interscalene) and quadriceps (femoral) muscles at the minimal current (0.1 ms, 2 Hz), the position of the cutaneous electrode was varied. Next, the duration of the stimulating current was set at 0.05, 0.1, 0.3, 0.5, or 1.0 ms, in random order. Intensity of the motor response and discomfort on stimulation were recorded.
The minimal current at which a visible motor response was obtained was 0.32 +/- 0.1 mA (0.23-0.38 mA) for the inter-scalene block and 0.29 +/- 0.1 mA (0.15-0.4 mA) for the femoral block. Changing the position of the return electrodes did not result in any change in the grade of the motor response or in the current required to maintain it. Currents of longer duration caused discomfort and more forceful contraction at a lower current intensity as compared with currents of shorter duration (P < 0.01). When the current was adjusted to maintain the same visible motor response, there was no significant discomfort among studied current durations.
Site of placement of the cutaneous electrode is not important when constant current nerve stimulators are used during nerve localization in regional anesthesia. There is an inverse relation between the current required to obtain a visible motor response and current duration. Selecting a current duration between 0.05 and 1.0 ms to specifically stimulate sensory or motor components of a mixed nerve does not seem to be important in clinical practice.
[show abstract][hide abstract] ABSTRACT: Anesthesiologists typically rely on a subjective evaluation ("syringe feel") of possible abnormal resistance to injection while performing a peripheral nerve block (PNB). A greater force required to perform the injection is believed to be associated with intraneural injection. The hypothesis of this study is that anesthesiologists vary in their perception of "normal" injection force, that the syringe feel method is inconsistent in estimating resistance, and that needle design may affect the injection force.
Thirty anesthesiologists were asked to inject a local anesthetic, as they would in their everyday practice, through a commonly used syringe and needle assembly. Injection force was measured using an in-line manometer coupled to a computer via an analog-to-digital conversion board. In addition, injection force at clinically relevant injection speeds was determined using 3 differently sized needles from 4 different manufacturers.
During a steady injection rate, all anesthesiologists perceived an increase in the force required to inject, even with minor pressures changes (0.6 +/- 0.3 psi). However, the 30 anesthesiologists, 21 (70%) initiated injection using a force that resulted in pressures greater than 20 psi; 15 (50%) used a force greater than 25 psi, and 3 (10%) exerted pressures greater than 30 psi. Pressures varied as much as 20-fold among needles of the same gauge/length from different manufacturers (P <.01).
Anesthesiologists vary widely in their perception of appropriate force and rate of injection during PNB. The syringe-feel method of assessing injection force is inconsistent and may be further affected by variability in needle design.
Regional Anesthesia and Pain Medicine 01/2004; 29(3):201-5. · 3.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: Nerve stimulation with a low-intensity electrical current has become a vital part of the performance of peripheral nerve blockade. The purpose of this study was to compare the accuracy and characteristics of peripheral nerve stimulators used in clinical practice in the United States.
Fifteen peripheral nerve stimulators were fitted with fresh batteries and set to deliver currents ranging from 0.1 to 4.0 mA into a series of high-tolerance resistance loads ranging from 1 to 100 komega. The current output, stimulus duration, morphology, frequency, and maximum voltage output were studied using a factory-calibrated oscilloscope.
All peripheral nerve stimulators performed uniformly well when set to deliver currents of 1.0 mA or more into a standard resistance load of 1 or 2 komega. However, at lower currents, the median error (%) increased from 2.4 (-5-144%) at 0.5 mA to 10.4 (-24-180%) at 0.1 mA into a 1 komega load. The morphology of the stimulus was characterized by a regular monophasic square pulse at current outputs of up to 1 mA and at a resistance of 1 komega. The stimulus waveform became particularly distorted as the impedance load was increased. The duration of the default stimulus set by the manufacturer varied from 34.8 to 460 micros among the peripheral nerve stimulators tested. The maximum voltage output ranged from 7.4 to 336 Volts.
Nerve stimulators used for regional anesthesia vary greatly in accuracy of current output and in manufacturer-selected electrical characteristics (e.g., current duration, stimulating frequency, maximum voltage output).
[show abstract][hide abstract] ABSTRACT: Cutaneous nerve blocks of the lower extremity are useful anesthetic techniques that can be used as a sole anesthetic technique for minor surgical procedures. More commonly, these blocks are used as an adjunct to the major conduction blocks of the lower extremity. These blocks are superficial, require minimal equipment, are relatively simple to accomplish and learn, and should be in the armamentarium of every practitioner. Copyright 2003, Elsevier Science (USA). All rights reserved.
Techniques in Regional Anesthesia [amp ] Pain Management 01/2003; 7(1):26-31.
[show abstract][hide abstract] ABSTRACT: To review the current recommendations and literature on training in regional anesthesia and suggest an improved model to prepare graduating residents better in the practice of regional anesthesia.
Patient satisfaction, a growing demand for cost-effective anesthesia, and a favorable postoperative recovery profile have all resulted in the growing demand for regional anesthesia. However, it has been well established that the current teaching of regional anesthesia is suboptimal.
A structured regional anesthesia rotation, a dedicated team of mentors with training in regional anesthesia, and adequate clinical volume are a pre-requisite for adequate training, but they may not be available in many anesthesia residency training programs. As the demand for regional anesthesia continues to increase in the years to come, it is imperative to ensure adequate education of graduating residents to meet this demand. In order to achieve this goal, the present recommendations should be re-evaluated, and perhaps a proficiency in a core group of widely applicable and relatively simple nerve blocks should be mastered by all graduates.
Current Opinion in Anaesthesiology 01/2003; 15(6):669-73. · 2.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: Considerable controversy exists over the relationship of paresthesia to nerve stimulation. The purpose of this study was to determine the frequency with which patients report paresthesia at the point that an acceptable motor response is obtained to low-intensity current electrical stimulation.
Low-intensity current nerve stimulation (0.6 mA, 200 microseconds, 2 Hz) was used to identify the brachial plexus in 64 consecutive patients having shoulder or arm surgery with an interscalene block. During nerve localization and while maintaining a motor response (0.20 mA-0.40 mA), the patients were queried regarding any radiating sensation or pain (paresthesia) in the shoulder or extremity on the side of the blockade. Sensory distribution of the block, motor strength of the arm muscles, and adequacy of anesthesia were used to assess the extent of blockade.
Ninety-five percent of patients had satisfactory surgical anesthesia. None of the patients spontaneously reported having a paresthesia during nerve stimulation. However, on careful questioning, half of the patients (55%) reported electrical paresthesia, defined as dull tingling sensation traveling down to their hands and coinciding with the motor response. In addition, most patients (71%) spontaneously reported having a mild, radiating paresthesia on initial injection of local anesthetic.
Painful paresthesiae should be infrequent when a low-stimulating current is used to identify the neural components of the brachial plexus and when the block needle is advanced slowly. Low-current intensity nerve stimulation can be used to achieve successful interscalene block with minimal discomfort to the patient.
Regional Anesthesia and Pain Medicine 01/2003; 28(5):380-3. · 3.46 Impact Factor
[show abstract][hide abstract] ABSTRACT: The classical approach to sciatic nerve block in the popliteal fossa (popliteal block) often requires multiple attempts to localize the sciatic nerve. Recently, it has been suggested that an intertendinous approach to popliteal block may result in a more consistent localization of the sciatic nerve. In the current study, we compared anatomical landmarks for the intertendinous and classical approaches to popliteal block with respect to the accuracy in localizing the sciatic nerve using magnetic resonance imaging simulation. Two anesthesiologists experienced in popliteal block drew landmarks for the intertendinous and classical approaches on 10 volunteers; a 1.5 Tesla superconducting magnet was used to obtain simultaneous, 10-mm thick, fast-spin echo proton density transverse axial sequences of the lower extremities. Using these acquired images, the two approaches were simulated off-line using previously identified landmarks. The spatial relationships of the simulated needle paths to the nerves and vessels in the popliteal fossa, as well as other relevant structures, were measured and compared. Simulation of the intertendinous approach to popliteal block resulted in needle-to-sciatic nerve contact in 14 legs (70%) versus 5 legs (25%) when the classical approach was used (P < 0.05). We conclude that the intertendinous approach might result in a more consistent localization of the sciatic nerve and may decrease the risk of sciatic vessel puncture. IMPLICATIONS: A simulation of popliteal block using magnetic resonance imaging in volunteers suggests that using tendons of the hamstring muscles as the anatomical landmarks yields a more consistent localization of the sciatic nerve.
[show abstract][hide abstract] ABSTRACT: A large proportion of patients undergoing surgery do not receive adequate postoperative analgesia.1 Postoperative pain is the leading cause of unplanned hospital admissions after ambulatory surgery and a major source of dissatisfaction with perioperative outcome.2 The establishment of acute pain services in major institutions both in the United States and overseas has had a major effect on postoperative comfort and patient satisfaction.3,4 Most acute pain services primarily use intravenous patient-controlled analgesia (PCA) or patient-controlled epidural infusion; however, advances in neuronal blockade offer an unprecedented range of effective and surgery site–specific analgesic options. Using long-acting local anesthetics, peripheral nerve blocks can be used to provide an excellent anesthesia and postoperative analgesia. Additionally, a catheter for continuous infusion of local anesthetics can be inserted perineurally to extend the analgesia beyond the duration of the single-shot blocks. This review will discuss the advantages and limitations of various nerve block techniques when used for postoperative pain management for several common surgical indications. Copyright 2002, Elsevier Science (USA). All rights reserved.
Techniques in Regional Anesthesia [amp ] Pain Management 01/2002; 6(2):60-65.
[show abstract][hide abstract] ABSTRACT: Peripheral nerve stimulators have become an indispensable tool in the practice of regional anesthesia. Knowledge and in- depth understanding of how they function is required to realize their full potential in a clinical setting. This review serves to elucidate the basic engineering principles behind nerve stimulators and provides tips on how to choose a nerve stimulator for your own practice. Copyright 2002, Elsevier Science (USA). All rights reserved.
Techniques in Regional Anesthesia [amp ] Pain Management 01/2002; 6(4):155-157.
[show abstract][hide abstract] ABSTRACT: In the anterior approach to the sciatic nerve block, the femur often obstructs the passage of the needle toward the sciatic nerve. In this study, by using a human cadaver model, we assessed how internal and external rotation of the leg influences the accessibility of the sciatic nerve with the anterior approach. Ten lower extremities from five adult cadavers were studied. Needles were used to simulate the anterior approach to the sciatic nerve block. The effect of leg rotation on the needle plane required to reach the sciatic nerve was studied with legs in the neutral position and then with internal and external rotation (45 degrees) of the legs. During needle placement in the neutral position, the needle could not be fully advanced to the level of the sciatic nerve because of obstruction by the lesser trochanter in 80% of attempts. Medial redirection of the needle (10 degrees--15 degrees) allowed it to pass the lesser trochanter but brought the tip of the needle too medial to the sciatic nerve. Internal rotation of the leg facilitated passage of all needles inserted at the level of the lesser trochanter. We conclude that internal rotation of the leg may significantly facilitate needle insertion in the anterior approach to sciatic block.
[show abstract][hide abstract] ABSTRACT: The sciatic nerve (SN) originates from the L4-S3 roots in the form of two nerve trunks: the tibial nerve (TN) and the common peroneal nerve (CPN). The TN and CPN are encompassed by a single epineural sheath and eventually separate (divide) in the popliteal fossa. This division of the SN occurs at a variable level above the knee and may account for frequent failures reported with the popliteal block. We studied the level of division of the SN in the popliteal fossa and its relationship to the common epineural sheath of the SN. The level of division of the SN sheath into TN and CPN above the knee was measured in 28 cadaver leg specimens. The SN was invariably formed of independent trunks (TN and CPN) encompassed in one common epineural sheath. The SN divided at a mean distance of 60.5 +/- 27.0 mm (range 0 to 115 mm) above the popliteal fossa crease. We conclude that the TN and CPN leave the common SN sheath at variable distances from the popliteal crease. This finding and the relationship of the TN and CPN sheaths may have significant implications for popliteal block. Implications: When performing popliteal block, insertion of the needle at 100 mm above the popliteal crease is more likely to result in placement of the needle proximal to the division of the sciatic nerve than placement at 50 or 70 mm, according to the classical teaching.
[show abstract][hide abstract] ABSTRACT: Recently there has been a considerable increase in interest in regional anesthesia and neural blockade. Many traditional nerve block techniques have been significantly modified to better fit the realm of both inpatient and outpatient surgery. The introduction of long acting local anesthetics with better safety profile as well as better equipment for continuous neuronal blockade has further increased the utility of peripheral nerve blocks. A significant effort has also been invested in studying and improving the safety of various techniques. These developments, coupled with an increased emphasis on teaching of regional blocks by organized anesthesia societies are likely to result in a wider use of these techniques in years to come.
Current Opinion in Anaesthesiology 11/2000; 13(5):549-55. · 2.40 Impact Factor
[show abstract][hide abstract] ABSTRACT: The site for needle insertion in femoral nerve block varies significantly among various descriptions of the technique. To determine the site with the highest likelihood of needle-femoral nerve contact, femoral nerve block was simulated in a human cadaver model (17 femoral triangles from 9 adult cadavers). Four 20-gauge 50-mm-long styletted catheters were inserted at four frequently suggested insertion sites for femoral nerve block. At the levels of inguinal ligament and the inguinal crease, the catheters were inserted adjacent to the lateral border of the femoral artery and 2 cm lateral to the femoral artery. During anatomical dissection, we studied the number of catheter-nerve contacts for each of the four insertion sites, and relationships between the femoral nerve and other anatomical structures of relevance to femoral nerve block. Insertion of the needle at the level of the inguinal crease, next to the lateral border of the femoral artery resulted in the highest frequency of needle-femoral nerve contacts (71%). Of note, the femoral nerve was significantly wider (14.0 vs 9.8 mm) and closer to the fascia lata (6.8 vs 26.4 mm) at the inguinal crease than at the inguinal ligament level. We conclude that needle insertion at the inguinal crease level immediately adjacent to the femoral artery produced the highest rate of needle-femoral nerve contacts. The main factors influencing this result include the greater width of the femoral nerve and the more predictable femoral artery-femoral nerve relationship at the inguinal crease level, compared with the inguinal ligament level. IMPLICATIONS: Insertion of a needle at the inguinal crease level and immediately adjacent to the lateral border of the femoral artery results in a high rate of needle-femoral nerve contact.