Duration of peripheral nerve blocks in opioid-tolerant individuals: A study protocol.

BackgroundThere is a long latent period for the sciatic nerve block before a satisfactory block is attained. Changes in the temperature of local anesthetics may influence the characters of the peripheral nerve block. This study was designed to evaluate the effect of warming ropivacaine on the ultrasound-guided subgluteal sciatic nerve block.MethodsFifty-four patients for distal lower limbs surgery were randomly allocated into warming group (group W, n = 27) or room tempeture group (group R, n = 27) with the ultrasound-guided subgluteal sciatic nerve block. The group W received 30 ml of ropivacaine 0.5% at 30℃ and the group R received 30 ml of ropivacaine 0.5% at 23℃. The sensory and motor blockade were assessed every 2 min for 30 min after injection. The primary outcome was the onset time of limb sensory blockade.ResultsThe onset time of sensory blockade was shorter in group W than in group R (16 (16,18) min vs 22 (20,23) min, p < 0.001), and the onset time of motor blockade was also shorter in group W than in group R (22 (20,24) min vs 26 (24,28) min, p < 0.001). The onset time of sensory blockade for each nerve was shorter in group W than in group R (p < 0.001). No obvious differences for the duration of sensory and motor blockade and the patient satisfaction were discovered between both groups. No complications associated with nerve block were observed 2 days after surgery.ConclusionsWarming ropivacaine 0.5% to 30℃ accelerates the onset time of sensory and motor blockade in the ultrasound-guided subgluteal sciatic nerve block and it has no influence on the duration of sensory and motor blockade.Trial registrationThe trial was registered on October 3, 2022 in the Chinese Clinical Trial Registry (https://www.chictr.org.cn/bin/project/edit?pid=181104), registration number ChiCTR2200064350 (03/10/2022).

Objective: The objective of this study was to determine the duration of onset and regression time of sensory and motor blocks, the quality of anesthesia, and post-operative analgesia by the addition of dexmedetomidine to local anesthetic solution in intravenous regional anesthesia (IVRA) in upper extremity orthopedic surgeries. Methods: This is a prospective, randomized, and double blind clinical trial. Ninety American Society of Anaesthesiologists Grade I and II patients of either gender between 18 and 60 years of age scheduled for elective upper extremity orthopedic surgeries lasting for &lt;90 min were included in the study. Patients were randomly allocated to two Groups A and B of 45 each. Group A received 3 mg/kg preservative free lignocaine alone and Group B received 3 mg/kg preservative free lignocaine with dexmedetomidine, 0.5 μg/kg in IVRA. Result: Onset time of sensory blockade in Group A and B was 5.6±0.93 min and 3.9±0.63 min, respectively. Onset time of motor blockade in Group A and Group B was 15.01±4.53 min and 10.74±3.64 min, respectively. The difference in onset time of sensory and motor blockade between the two groups was statistically significant (p&lt;0.05). Sensory blockade recovery time after release of tourniquet was 6.9±0.53 min in Group A and 29.21±5.23 min in Group B. Motor blockade recovery time was 4.35±0.76 min for Group A and 12.32±7.23 min for Group B. The difference in sensory and motor blockade recovery time between the two groups was statistically significant (p&lt;0.05). Conclusion: Dexmedetomidine on addition to lignocaine for IVRA provided rapid onset of sensory and motor blockade, prolonged duration of sensory and motor blockade, and reduced tourniquet pain.

<h3></h3> Peripheral nerve blocks' effectiveness is limited by pain outlasting the analgesic duration of the nerve block. Different approaches have been used to counter this limitation, for example insertion of...

Introduction: Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in term of such damage. The relief from pain is the essence of anesthesia. Peripheral nerve blocks provide longer and more localized pain relief than neuraxial techniques while also avoiding the side effects of systemic medication. This study was aimed to find the effectiveness of Study solution (addition of Sodium bicarbonate to 0.375% Bupivacaine) on onset time, duration and quality of Brachial Plexus Block. Material and methods: This study was conducted among 60 different patients undergoing surgical procedure of the upper limb. They were categorized into two different groups. The first group (Group 1), 30 patients received Brachial Plexus block with 30 ml of study solution (0.375% Bupivacaine with 2 ml of Sodium bicarbonate7.4%). The second group (Group 2) received 30 ml of 0.375 % plain bupivacaine only and the differences in onset, duration and quality of blockade were studied. Result: The similarity of age between the two groups can be seen. In Group 1 the mean onset time of sensory blockade was 9.43 minutes and motor blockade was 10.43 minutes when compared to Group 2 having sensory onset of minutes 23.93 and motor onset of 26.33 minutes. Similarly, In Group I the mean duration of sensory blockade was 477.67 minutes and motor blockade were 467.67 minutes when compared to Group 2 having sensory duration of 215.67 and motor duration of 205.67 minutes. The quality of sensory blockade was also better in group1 (P-Value:0.006). Conclusion: Addition of Sodium bicarbonate to bupivacaine had significant clinical advantage over plain bupivacaine on onset time, duration and quality of sensory and motor blockade in brachial plexus block.

Peripheral nerve blocks are becoming increasingly popular for perioperative use as anesthetics and analgesics in small animals. This prospective study was performed to investigate the duration of motor and sensory blockade following use of bupivacaine for ultrasound-guided femoral and sciatic nerve blocks in dogs and to measure the plasma concentrations of bupivacaine that result from these procedures. Six dogs were anesthetized twice using a randomized cross-over design. At the first anesthetic, dogs were assigned to receive either an ultrasound-guided femoral nerve block or sciatic nerve block with 0.15 mL kg-1 of bupivacaine 0.5%. Two months later, the other nerve block was performed during a second anesthetic. At 5, 10, 15, 20, 30 and 60 minutes after injection, arterial blood samples were collected for laboratory measurement of bupivacaine. After 60 minutes, dogs were recovered from anesthesia. Starting at two hours post-injection, video-recordings of the dogs were made every two hours for 24 hours. The videos were randomized and the degree of motor and sensory blockade was evaluated using a three-point scoring system (0 = no effect, 1 = mild effect, 2 = complete blockade) by two blinded assessors. The median (range) times to full recovery from motor blockade were 11 (6–14) hours (femoral) and 12 (4–18) hours (sciatic), and 15 (10–18) hours (femoral) and 10 (4–12) hours (sciatic) for sensory blockade. There were no differences in the median times to functional recovery for the two techniques. Plasma concentrations of bupivacaine were no different following the blocks and were less than 0.78 μg mL-1 at all times. These results suggest that these ultrasound-guided nerve blocks do not result in potentially toxic systemic levels of local anesthetic and that their duration of action is useful for providing anesthesia and analgesia for pelvic limb procedures.

Introduction Peripheral nerve blocks are frequently used as the sole anesthetic technique or as an adjuvant to general anesthesia, However, the duration of sensory nerve block after single doses of long-acting local anesthetics is not consistent enough to avoid the use of postoperative opioids. Many adjuvants have been added to prolong the duration of nerve block, It was recently suggested that, based on current evidence, perineural dexmedetomidine is the most promising adjuvant to extend the duration of long-acting local anesthetics Aim The aim of this work is to study the effects of dexmedetomidine as an adjuvant to bupivacaine in various peripheral nerve blocks. The study will include: supraclavicular brachial plexus block, paravertebral block and femoral nerve block. Patients Adult patients of either sex aged 25 – 60 years, ASA physical status I and II, Elective surgeries appropriate for the nerve block. Methods patients received bupivacaine 0.5% alone in (group I) or bupivacaine 0.5% combined with 100 dexmedetomidine (group II) in peripheral nerve blocks. Motor and sensory block onset times; durations of blockades and analgesia were recorded Results Sensory and motor block onset times were shorter in group II than in group I. Sensory and motor blockade durations were longer in group II than in group I. Duration of analgesia was longer in group II than in group I. Systolic, diastolic arterial blood pressure levels, and heart rate were less in group II. Conclusion In the current study, it was obvious that:(Addition of dexmedetomidine to bupivacaine in supraclavicular nerve block, paravertebral nerve block and femoral nerve block has shortened the onset times of both sensory and motor blocks and significantly prolonged their durations, Dexmedetomidine had also the added effect of sedation with minimal side effects, which makes it a beneficial adjuvant to local anesthetics in peripheral nerve blocks, Addition of dexmedetomidine to bupivacaine prolonged the postoperative analgesia with subsequent consumption of less amount of analgesics and The use of ultrasonography in performing nerve blocks significantly reduced the incidence of complications such as pneumothorax or intra-arterial injection and hence, lowered the incidence of systemic toxicity of local anesthetics).

BACKGROUND: The quest for searching newer and safer anaesthetic agents has always been one of the primary needs in anaesthesiology practice. Regional anaesthesia techniques have seen numerous modifications over the last two decades with the advent of many newer and safer local anaesthetics Keeping these factors in mind, S (−)-enantiomer of bupivacaine, levobupivacaine has been developed. The advantages of levobupivacaine over bupivacaine are decreased cardiovascular toxicity and there is also a relatively decreased motor nerve fiber penetration and block, thereby a decreased post operative motor blockade and thus early ambulation of the patients can be achieved. The present study compared the effects of addition of epidural dexmedetomidine 50 micrograms to epidural 0.5% levobupivacaine for infraumbilical and lower limb surgeries. METHODS: Sixty patients of either sex belonging to ASA I & II in the age group of 25-45 years scheduled for infraumbilical and lower limb surgeries were randomly divided into 2 groups (30 each) to receive 0.5% isobaric levobupivacaine 20 ml epidurally with 0.5 ml distilled water (Group A) and 0.5% isobaric levobupivacaine 20 ml plus 0.5 ml dexmedetomidine containing 50 micrograms (Group B). This study evaluated the following parameters like time of onset of sensory blockade at T10 level, maximum sensory blockade achieved and time taken to achieve the same, onset time of motor blockade, degree of motor blockade, time taken to achieve maximal motor blockade, hemodynamic changes in pulse rate, blood pressure and oxygen saturation, side effects and complications, intraoperative sedation scores, duration of analgesia, sensory & motor blockade, and any postoperative adverse reactions. RESULTS: The data obtained from the above parameters were statistically analysed using SSPS version 16 software. Student t test was used for parametric data and Chi-square test for non parametric data. P<0.05 was considered as statistically significant. Maximal sensory level was achieved with addition of dexmedetomidine ranging from T4 to T6.Also the onset time of motor blockade was shortened with group A showing 19.33 minutes and group B showing only 14.5 minutes.The maximal motor blockade achieved was also intense (Bromage 3) with the addition of dexmedetomidine. Duration of analgesia, sensory and motor blockade were prolonged when levobupivacaine is combined with dexmedetomidine epidurally. Changes in hemodynamic parameters (blood pressure & heart rate) were very minimal in the dexmedetomidine group. Adverse effects experienced in general were statistically insignificant in both the groups. Mean sedation score in group B (Dexmedetomidine group) was predominantly found to be 2 as per Ramsay sedation score. None of the patients in group B had deep sedation or profound respiratory depression.

Upper limb trauma occurs frequently in elderly patients for whom peripheral nerve blocks are often preferred for anesthesia. The characteristics of such regional blocks have, however, never been described in an elderly population. Therefore, the authors assessed prospectively the onset and duration of upper extremity peripheral nerve block (the mid-humeral block) in elderly and young patients undergoing emergency upper extremity surgery. Consecutive patients aged > 70 yr or < 70 yr received a mid-humeral block with a small volume of ropivacaine, 0.75%. Five milliliters was injected onto each of the musculocutaneous, radial, ulnar, and median nerves. Time to complete sensory and motor block and durations of complete sensory and motor block were assessed. Results are shown as median and its 95% confidence interval. Median ages were 77 yr (95% CI, 72-81 yr) and 39 yr (95% CI, 27-46 yr) in the two groups. Both groups had similar times to complete sensory blockade. The elderly group had longer durations of complete sensory (390 min [range, 280-435 min] vs.150 min [range, 105-160 min]; P< 0.05) and motor (357 min [range, 270-475 min] vs. 150 min [range, 90-210 min]; P< 0.05) blockade. Duration of complete sensory block was significantly correlated with age (rho = 0.56; P< 0.05). Age is a major determinant of duration of complete motor and sensory blockade with peripheral nerve block, perhaps reflecting increased sensitivity to conduction failure from local anesthetic agents in peripheral nerves in the elderly population.

Effect of Ultrasound-guided Nerve Block With 0.75% Ropivacaine at the Mid-forearm on the Prevalence of Moderate to Severe Pain After Hand Surgery

ESRA19-0697 Knee arthroscopy and ligament repair: RA or infiltration

Effects of dexmedetomidine combined with ropivacaine on sciatic and femoral nerve blockade in dogs

Peripheral nerve block and local anaesthetic dose, how much is enough?

Failed Nerve Blocks: Prevention and Management

CONTINUOUS nerve blockade is the only available medium- to long-term modality that blocks evoked pain (e.g. , by knee flexion after knee surgery). In addition to the humanitarian and economical aspects of effective pain management, it is not surprising that improved and faster rehabilitation after surgery, such as knee arthroplasty, have been demonstrated.1Furthermore, decreased nausea and vomiting and increased patient satisfaction are consequences of continuous peripheral nerve blocks (CPNBs), whereas other interesting concepts, such as improved rehabilitation and decreased incidence of postsurgery chronic pain syndromes, are currently receiving attention. The use of continuous peripheral nerve block for outpatient ambulatory surgery is a growing trend countrywide and worldwide,2and the positive economic implications and impact of these promise to be enormous.Three techniques have been proposed to place perineural catheters: the nonstimulating catheter technique, the stimulating catheter technique, and ultrasound-aided catheter placement. A fourth technique, which is no longer used, is the periarterial placement of axillary catheters under direct vision after cut-down during local anesthesia. This author placed continuous axillary blocks with this technique for patients with war injuries to their arms and hands in 1974–1975 during the Angola Civil War.The stimulating catheter technique is probably more difficult and time-consuming to perform than the nonstimulating catheter technique. Whereas its primary block success rate probably equals that of the nonstimulating catheter technique, its secondary block success rate can be expected to be around 100%, versus approximately 65–85% with nonstimulating catheters.3The use of ultrasound for CPNB placement is not yet well established and is currently undergoing extensive preliminary evaluation.Early recorded uses of electrical nerve stimulation include assisting in accurate placement of a catheter for neuraxial blockade in 1948,4followed shortly thereafter by catheter placement for continuous peripheral nerve blockade in 1950.5Anatomical landmarks were still used at that time to place the needle through which the catheter was advanced. Stanley Sarnoff, M.D. (1917–1990) and his wife Lili-Charlotte Sarnoff, R.N., almost accidentally pioneered the use of nerve stimulation for the accurate placement of catheters for continuous peripheral perineural and subarachnoid blockade while working at the Harvard University School of Public Health (Boston, Massachusetts). In the midst of the polio epidemic of the 1950s, they developed the "Electrophrenic Respirator" for artificial ventilation of patients with bulbar polio by percutaneous phrenic nerve stimulation.6This device later served as a "nerve stimulator" to place a continuous nerve block catheter on the phrenic nerve for a patient with intractable hiccups.5Although later workers were not aware of the previous use of "stimulating catheters" in 1950, years later, in 1999, after the use of nerve stimulators for single-injection blocks of peripheral nerves had been well established, they reinvented the technique of placing catheters for CPNBs by stimulating the nerve via both the needle and the catheter.7In the 30 yr after the first descriptions, the main focus in the development of CPNBs was on the upper extremity, and it was mainly to improve blood flow by sympathetic blockade for reimplantations of traumatic upper limb amputations. Most authors used variations of the axillary perivascular technique in the 1970s and 1980s.8At the time, the analgesia was almost viewed as an additional bonus, because it was not the primary purpose of the block.During the 1990s, the emphasis shifted toward the use of CPNBs to manage acute postoperative pain. This was, among other factors, driven by the quest for cost-effective ambulatory surgery after the exponential explosion of medical inflation in the mid to late 1980s. Salter's discovery of the beneficial use of continuous passive motion for rehabilitation also played an important role in this development.9Because of the efficiency and relative safety of continuous neuraxial nerve blocks, the lower extremity received little attention during the early development of continuous nerve blockade; the main focus was on continuous interscalene blocks.10,11Singelyn et al. ,1who worked in Belgium, addressed the question of whether CPNB made any difference to the outcomes of surgery. They demonstrated that continuous femoral nerve blockade for a total knee replacement operation was superior to patient-controlled intravenous morphine in managing postoperative pain for total knee arthroplasty, with earlier and better rehabilitation. They also demonstrated fewer side effects than epidural analgesia, although the analgesia was similar. These results were confirmed in France12and the United States.13A frustrating problem with perineural catheters was inaccurate catheter placement and secondary block failure, which defeated the object of cost effectiveness. The stimulating catheter originated from this frustration in 1999.7Steele et al. 14described a now commonly used nonstimulating perineural catheter technique. An insulated Tuohy needle (e.g. , Contiplex, B. Braun, Bethlehem, PA; Vygon, Les Ulis, France; Alphaplex, Sterimed, Saarbrucen, Germany) is connected to a nerve stimulator. The needle is inserted at the required site and advanced until an appropriate motor stimulus is elicited with a current output of 0.3–0.5 mA, 2 Hz, and 100–300 μs. The needle is attached via tubing to a syringe to aspirate for blood or cerebrospinal fluid. The needle is held steady in that position, and saline or local anesthetic agent is injected through it. A 19- or 20-gauge single- or multiple-orifice epidural catheter is advanced 5–10 cm past the tip of the needle; the needle is removed; and the catheter is secured with medical adhesive spray, with transparent occlusive dressing, or by tunneling it.A nerve stimulator, set to 1–1.5 mA, 100- to 300-μs pulse width, and a frequency of 1–2 Hz, is attached to an insulated Tuohy needle (e.g. , StimuCath, Arrow International, Reading, PA; Stimulong Plus, Pajunk, Geisingen, Germany), and the nerve or plexus appropriate for the surgery is approached.7When the correct motor response is elicited, the needle is advanced until a brisk motor response is elicited with a current output of 0.3–0.5 mA. The needle is then held steady, and without injecting any fluid through the needle, the nerve stimulator is attached to the proximal end of the catheter, and the catheter is advanced through the needle (fig. 1). The elicited motor response should now be similar to that elicited by stimulating via the needle. The catheter is advanced beyond the needle tip with the motor response remaining unchanged. If the motor response changes, the catheter is carefully withdrawn to inside the shaft of the needle, and the needle's position is changed slightly by rotating clockwise or counterclockwise, moving it a few millimeters deeper or more superficial, or slightly changing the angle of the needle (fig. 2). The catheter is then advanced again. This process is repeated by making small, systematic changes to the needle after careful catheter withdrawal until the desired motor response is elicited when the catheter is advanced. The catheter is then advanced 3–5 cm beyond the needle tip.It is currently unclear what the acceptable stimulating current should be for confirming proper placement of the catheter. This probably varies from one type of block to the other.Sutherland15proposed the use of ultrasound for the accurate placement of continuous sciatic nerve blocks. Although the idea is promising, substantial development still must take place before ultrasound can be accepted as an alternative or additional method to place continuous nerve blocks. A problem with ultrasound is that, although it works well for superficial nerves (when it is not really needed), the depth of penetration of most readily available and affordable ultrasound probes is not sufficient to identify deeper nerves, especially in very obese patients (where it is most needed). This problem will no doubt be addressed as more advanced technology becomes available. Like ultrasound does not replace x-rays in orthopaedics, it is ultimately not likely to replace nerve stimulation for continuous nerve block. It is most likely to be a valuable addition to nerve stimulation.Most authors tunnel the catheter subcutaneously.7,16This has virtually eliminated the problem of catheter dislodgement. Various methods of tunneling a catheter have been described, but most of them are variations of tunneling with or without a "skin bridge."7,16There are three basic regimens to provide continuous peripheral nerve block analgesia: fixed basal rate, fixed basal rate plus bolus doses, or boluses only. The latter two regimens can be defined as patient-controlled regional analgesia (PCRA) systems. Not unlike patient-controlled intravenous analgesia, this is a drug delivery system aimed at controlling acute pain by using negative feedback in a closed-loop system in which the patient plays an active role. It overcomes the inadequacies of traditional analgesic protocols, which are caused by the marked differences in pharmacokinetics of analgesic requirements between patients. Patients can control the analgesic dose to balance pain relief with the side effects they are willing to tolerate and required motor function. Patients usually choose less than the available total dose of analgesic.The choice of infusion strategy depends on the preference of the practitioner, which should be based on the needs of the patients. There are limited guidelines based on research data available, but it seems feasible to use a baseline infusion plus patient-controlled bolus doses for very painful conditions and bolus dosing alone for less painful conditions. Ultimately, the infusion strategy should vary from one patient population or type of surgery to the next. Preliminary evidence indicates that a basal background infusion with PCRA provides equivalent or superior analgesia and improved patient satisfaction when compared with continuous infusion only or bolus dosing alone.17,18The use of bolus doses allows the patient to rapidly reinforce the block before physical therapy. If only PCRA boluses are used, patients experience more difficulty in sleeping19but might use less local anesthetic.20One should be flexible in choosing the infusion strategy for any particular patient or surgical setting. The chosen strategy should be individualized and designed to suit the individual needs of every patient. Every infusion strategy referred to above7,16–20is likely to be successful, and the patient is likely to be satisfied, if the catheter is accurately and painlessly placed and the infusion rate, concentration of the drug, and volume and lockout time of boluses are constantly adjusted to suit the changing requirements of individual patients. This ability to constantly tailor the infusion emphasizes the major advantage of CPNB over long-acting local anesthetic agents, which cannot be adjusted and, after unwanted side effects or complications occur, cannot be reversed. A good strategy is to start the CPNB with a bolus of approximately 0.3 ml/kg (with a maximum of 40 ml) of a high-concentration drug, e.g. , 0.5–0.75% ropivacaine, for intraoperative and directly postoperative analgesia. This is followed by an infusion of a low concentration of ropivacaine (0.1–0.2%) at an infusion rate of 5 ml/h and PCRA boluses of 10 ml at a lockout time of 2–4 h. If more motor function is required (e.g. , after total knee arthroplasty), adding normal saline to the reservoir will reduce the concentration of the drug (table 1).There are numerous commercial infusion pumps available, and the final choice of these should be made on the ability to deliver the required infusions and boluses at the required lockout intervals. With initiating the bolus dose, effort should not be required from the patient to empty the reservoir holding the drug. The ideal infusion pump should also be refillable and reprogrammable.Rawal et al. 21offered plausible arguments for the use of bolus doses only, although their indications for CPNB, e.g. , carpal tunnel decompression and other minor procedures, may be questionable. Because the analgesic needs of individual patients differ greatly and the duration of a single-dose local anesthetic varies considerably, PCRA by bolus doses on demand may be preferable to continuous infusion. Analgesia by bolus injection only satisfies individual needs, and it permits patients to maintain adequate analgesia regardless of changes in pain intensity. A possible disadvantage of the bolus-only PCRA technique may be either too dense a motor block after the bolus or too weak a sensory block for some time before the next bolus. Another important factor that needs to be considered is sleep disturbances that may occur when a basal infusion is not given.After 1 or 2 days of continuous infusion, as the postoperative pain decreases and the need for motor function increases, the concentration of local anesthetics can be decreased by adding saline to the reservoir. If a motor block is also required at this stage, the drug concentration can be kept constant, while reducing the infusion rate.Table 1summarizes the surgical procedures for which CPNBs have been used.Complications of perineural catheters for continuous nerve blockade are rare and probably less than those for single-injection nerve blocks,22although large comparative studies have not yet been reported. The most common problems associated with continuous nerve blockade are technical problems, including failed blocks or incomplete analgesia, which does seem to become less as the use of stimulating catheters increase7,16; catheter dislodgement, which seems to be largely solved with catheter tunneling7,16; and leakage around the catheter entry site. The latter is more frequent if a skin bridge is used during tunneling.Complications due to nerve injury are usually secondary to the insensitive limb. The nerves most commonly injured by this are the ulnar, radial, and common peroneal nerves, because of compression by ill-fitting slings and braces or compression of the ulnar nerve on the bed in supine patients (fig. 3). Nerve injury due to traction, diathermy, and direct injury during surgery are often unfairly attributed to nerve blocks. Severe permanent nerve injury caused by continuous nerve blockade has not yet been reported, although surgical damage to nerves, especially the musculocutaneous nerve during shoulder surgery, has recently been shown to be more common than originally thought.23Transient neurologic damage has also mainly been reported for continuous interscalene blocks22and in 0.5% of continuous axillary blocks.24Because the interscalene approach has been abandoned as first choice from the personal practice of this author and the continuous cervical paravertebral block is used as routine first choice for shoulder surgery, the complication of burning pain down the arm, especially in patients after arthroscopic capsulotomy for "frozen shoulder," has not yet been encountered in well over 2,000 cases.Furthermore, this author does not offer any preoperative nerve blocks to patients scheduled to undergo shoulder surgery if these patients experience pain, paresthesia, or dysesthesia distal to the elbow. Bona fide shoulder pathology does not cause pain or dysesthesia distal to the elbow. This pain is most likely caused by existing brachial plexopathy, and it may be prudent to err on the side of safety in such patients by offering them a postoperative nerve block after the shoulder pathology is clear. This is especially relevant if the patient was scheduled to undergo subacromial decompression, in which case a continuous or single-injection cervical paravertebral16or interscalene block can be performed postoperatively if shoulder pathology was found and treated and if deemed necessary by the patient. Motor responses due to nerve stimulation are usually painful after surgery, and proper use of potent analgesics, such as remifentanil, loss-of-resistance to air technique without nerve stimulation (cervical paravertebral block), or ultrasound (interscalene block) should be considered.Capdevila et al. 25reported their experience with 1,416 CPNBs, and although technical problems (17%), failure of pain relief (3.2%), persistent motor block (2.2%), and transient paresthesia and dysesthesia (1.4%) represented the most common complications, colonization of catheters by bacteria was reported in 28% of cases if prophylactic antibiotics were not used. Infection, defined as redness, swelling, or pus around the catheter entry site, can be expected to be present in 3%25to 5%16of cases, whereas deep abscess formation has not been reported yet. Bacterial species found include Staphylococcus epidermidis (61%, mostly found in interscalene catheters), gram-negative bacilli (22%, mainly associated with femoral nerve blocks), and Staphylococcus aureus (17%).25The incidence is not known if prophylactic antibiotics are used, as is often the case with orthopaedic surgery, but it can be expected to be lower. Risk factors for local inflammation are patients in intensive care units, males, catheter duration longer than 48 h, absence of prophylactic antibiotics, diabetes, and femoral nerve blockade.25Catheters should be removed and appropriate antibiotics should be prescribed when signs of infection are present.A comparison was made between the Winnie paresthesia interscalene blocks (group I), stimulating needle single-injection interscalene blocks (group II), and continuous interscalene blocks using a stimulating catheter (group III).7The authors reported 85% complete phrenic nerve blocks in the first group compared with 35% in the second group and 20% in the continuous interscalene block group. Other common nerves that are incidentally blocked are the recurrent laryngeal nerve and the superficial cervical plexus, but these do not usually pose any problems.Total spinal anesthesia has been associated with continuous lumbar paravertebral blockade,26but not with any other continuous perineural catheter. Recurrent brachial plexus neuropathy in a diabetic patient after shoulder surgery and a continuous interscalene block has been reported.27Epidural spread with contralateral block, although not causing any problems, has been reported during continuous cervical paravertebral block.16Toxic drug effects during continuous infusion have not yet been reported, but reports of toxic effects can be expected as continuous peripheral nerve blocks become more widely used. Acute myotoxic effects of local anesthetic agents have been described after continuous peripheral nerve blockade with bupivacaine and ropivacaine in a porcine model.28Compared with bupivacaine, which caused both muscle fiber necrosis and apoptosis, the tissue damage caused by ropivacaine was significantly less severe than that caused by bupivacaine in experimental animals.All catheters (and all nerve blocks for that matter) are placed during some form of anesthesia: some during general anesthesia, some during regional anesthesia, and others during local anesthesia. (In dentistry and ophthalmology, for example, nerve blocks are even placed during topical anesthesia). In this respect, the practitioner should not be rigid but instead should choose the technique appropriate for each individual patient. Placing catheters for CPNBs should never be painful or uncomfortable. The most common cause for pain with CPNB placement is anxiety, which can be adequately dealt with by administering adequate dosages of anxiolytic agents, such as 0.015– 0.15 mg/kg midazolam. Propofol is commonly used, but practitioners should be cautioned because this drug may cause the patient to become unruly at low doses and unconscious, causing airway obstruction, at higher doses.29Furthermore, when appropriate (e.g. , in the case of children, in cases of very painful conditions or very anxious patients), the catheter can be placed during general anesthesia. There is no guidance from the literature as to whether this may increase the incidence of complications or side effects of CPNBs, but the current author contends that placing blocks during general anesthesia in certain circumstances may even be less hazardous, because the patient will not move during needle and catheter placement, and nothing about potential nerve injury can be learned from a crying child or a distressed adult.The area where the CPNB is placed should be anesthetized thoroughly before the catheter is placed. For example, a regional block of the superficial cervical plexus, slowly injected with a fine needle, can be performed before a continuous interscalene block is attempted.7Similarly, a field block down to the pars intervertebralis (or articular column) of the sixth cervical vertebra should be done before a continuous cervical paravertebral block is performed.16It should go without saying that the area of intended catheter tunneling should be appropriately anesthetized before tunneling.Other rare and minor complications of perineural catheters have been reported, although none seem to be due to long-term continuous exposure of the nerves to local anesthetic agents or the presence of the catheter on or near the nerves.Perineural catheters for CPNBs have developed from pure motor blockade for intractable hiccups, through upper limb sympathetic blocks to enhance blood flow after reimplantation surgery, to sensory blocks for the ambulatory management of acute pain. Over the years, the techniques and equipment have improved, and it is now possible to place catheters for CPNBs accurately and thus virtually eliminate secondary block failure. Although complications of CPNBs are not yet sufficiently investigated, it seems that they are rare and, if present, they are mild and occur after the initial, relatively large dose of local anesthetic agent, while the patient is usually still under the care of the anesthesiologist. It is never necessary to hurt patients during catheter placement, and infusion strategies can and should be tailored to the individual requirements of each patient.It is important that patients' well-being and pain relief continuously improve each day after surgery. It is therefore inappropriate to remove catheters prematurely before pain is manageable with oral or parenteral analgesics.The author thanks Peter van de Putte, M.D., and Martial van der Vorst, M.D. (both from the Department of Anesthesia, Ziekenhuis O.L.V. Middelares, Deune, Belgium), Chris Theron, M.D. (Oranjezicht, Cape Town, South Africa), and Paul Casella (Program Associate, University of Iowa, Iowa City, Iowa) for their valuable assistance with the preparation of this manuscript.

Background: Many drugs have been used as adjuvants to local anesthetic agents to prolong the duration of peripheral nerve blocks and decrease the time of onset. In this study we assessed the effect of dexmedetomidine as an adjuvant to bupivacaine in supraclavicular brachial plexus block in terms of onset and duration of sensory and motor blockade, intraoperative sedation, postoperative analgesia, sedation and Complications /side effects if any. Methods: 60 patients of age 18-70 yrs were divided into two equal groups for upper limb surgeries under supraclavicular brachial plexus block. Group BD was given 39 millilitres (ml) of 0.5% Bupivacaine+1 microgram/kg dexmedetomidine; Group BS was given 39 ml of bupivacine+1 ml of saline. The following brachial plexus nerve block parameters were assessed hemodynamic parameters, onset and duration of sensory and motor blockade, Ramsay sedation score, verbal rating score, duration of analgesia, duration for rescue analgesia and number of analgesia given. Results: The onset of sensory blockade was 2.54 minutes less in Group (BD) when compared to Group (BS). The onset of Motor Blockade is 3.26 minutes less in Group (BD) when compared to Group (BS). The duration of sensory blockade is 195.65 minutes more in Group (BD) then Group (BS). The duration of Motor Blockade is 190.33 minutes more in Group (BD) when compared to Group (BS). The duration of Analgesia is 207.83 minutes more in Group (BD) when compared to Group (BS). Ramsay sedation score in Gp (BD)continued to show slightly higher sedation scores at all times including postoperative period in comparison to Gp (BS) (P<0.01). Conclusion: Dexmedetomidine is good adjuvant to local anesthestic agents, as its addition to bupivacaine was associated with prolonged sensory and motor blockade, mild sedation and prolonged analgesia. Satisfactory hemodynamic stability without observed immediate post-operative side effects are other significant qualities related to it.