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This is a relatively specialised technique aimed more at enhancing the skills of doctors regularly performing local anaesthetic blocks. It is a useful device for confirming the location of major nerves and plexuses proximally, but not necessary for most peripheral nerve blocks.
Nerve conduction block induced by high-frequency sinusoidal electrical current was simulated using a lumped circuit model of the unmyelinated axon based on Hodgkin-Huxley equations. Axons of different diameters (1-20 microm) can be blocked when the stimulation frequency is above 4 kHz. At higher frequency, a higher stimulation intensity is needed to block nerve conduction. Larger diameter axons have a lower threshold intensity for conduction block. High-frequency sinusoidal electrical currents are less effective in blocking nerve conduction than biphasic square pulses of the same frequency. The activation of potassium channels, rather than inactivation of sodium channels, is the possible mechanism underlying the nerve conduction block of the unmyelinated axon induced by high-frequency biphasic (sinusoidal or square pulse) stimulation. This simulation study, which provides more information about the axonal conduction block induced by high-frequency sinusoidal currents, can guide future animal experiments, as well as optimize stimulation waveforms for electrical nerve block in possible clinical applications.
A new lateral approach to blocking the sciatic nerve in the popliteal fossa is described. In a prospective study, 40 patients scheduled for foot surgery involving osteotomies were allocated randomly into one of two groups following induction of general anaesthesia: group PS (n = 21) received a lateral popliteal sciatic nerve block and group SC (n = 19) received subcutaneous infiltration of the wound. Both groups received 20 ml bupivacaine 0.5% plain. The lateral approach to the popliteal sciatic nerve was found to be an effective, quick, and easy to perform, block. Postoperative analgesia in groups PS lasted a median of 18.0 hr and in group SC lasted 6.3 hr (P < 0.05). The lateral popliteal sciatic nerve block provided effective analgesia following foot surgery and had a high level of patient satisfaction.
BACKGROUND: Ketamine has been shown to prolong analgesia produced by caudal local anaesthetic block and is now in common use. This study compares caudal block using bupivacaine/ketamine with dorsal nerve block of the penis. METHODS: Sixty boys undergoing elective circumcision were given either 0.5 ml x kg-1 of bupivacaine 0.15% with ketamine 0.5 mg x kg-1 (n = 30) or dorsal nerve block of the penis with bupivacaine 0.5% (n = 30) as a supplement to general anaesthesia. Postoperative pain was assessed by parents using a modified objective pain score, and the time taken to first requirement of analgesia was recorded. Motor weakness, time to first micturition, postoperative nausea and vomiting (PONV), eating habits, sleep disturbance and behaviour were also assessed. RESULTS: There was no difference between the groups in time to first requirement for analgesia or number of doses of paracetamol given in the first 24 h. Almost half the boys in the caudal group had motor weakness, and there was a significant increase in time to first micturition in that group. There was no difference between the groups in PONV, eating, sleeping or behavioural disturbance. CONCLUSIONS: Caudal anaesthesia with bupivacaine/ketamine does not confer any advantage over a dorsal nerve block with the doses used in this study. Because of the higher incidence of side-effects and technique failure in the caudal group, dorsal nerve block is perhaps the preferred technique.
Axillary nerve blocks are now frequently used for emergency and elective upper limb surgery. The method gives reliable anaesthesia with few complications. A case is described in which a patient developed Herpes Zoster following an Axillary Nerve Block, a hitherto unreported complication.
Up to now, mandibular nerve blocks have been carried out without knowing the exact blood concentrations resulting from the use of the local anesthetics. Due to the high vascularity a rapid increase in serum local anesthetic levels is to be expected. Due to analytical problems, the literature provides controversial statements about the pharmacokinetics of articaine which is generally used for this block. The given half-life periods following intramuscular application range from 39 min [8] to 31 h [6]. For this reason, mandibular nerve blocks with 2 ml 4% articaine with 1:200,000 epinephrine were carried out in 10 awake patients and 10 patients during intubation anesthesia. RESULTS. Blood samples from peripheral veins showed an average maximum concentration of 2.1 +/- 1.3 mg/l after 12.5 +/- 2.5 min. After 8 h the value had fallen below the minimum detection limit of 0.05 mg/l. In the present study, a half-life of approximately 20 min was determined for articaine after conduction anesthesia. This local anesthetic holds an exceptional position because as an amide-type local anesthetic it contains an additional ester group that is hydrolytically metabolized in the blood. The concentration of the resulting metabolite reaches a maximum value of 2.6 +/- 1.6 mg/l after 40 to 50 min. CONCLUSIONS. Compared to other amide-type local anesthetics, whose terminal plasma half-life varies between 1 and 3.6 h [5], the value of 20 min found for articaine is very low. This is in part due to its structure, as the ester group is rapidly metabolized by plasma esterases. Because of its rapid breakdown articaine is very suitable for use in oral surgery. The HPLC method represents an uncomplicated analytical technique for the determination of local anesthetics levels in blood and other body fluids.
Currently, the inferior alveolar nerve block is sometimes ineffective for a number of reasons. The extra-intraoral landmark technique (EIL technique) was modified and compared in effectiveness with the direct technique in patients undergoing inferior alveolar nerve block. The results showed that the success rates of the EIL technique based on both subjective and objective responses were significantly greater than those of the direct technique. The EIL technique also resulted in significantly less pain from the injection than the direct technique.
BACKGROUND: Obturator nerve block is highly recommended for knee surgery in addition to a femoral nerve block. The main disadvantage of the classic approach at the pubic tubercle is low patient acceptance due to pain and discomfort. The authors hypothesized that the use of a new inguinal obturator nerve block technique would reduce pain and discomfort in patients. METHODS: The inguinal approach was simulated in five fresh cadavers. Injection of latex was performed in two cadavers. The location of the needle and the extent of latex solution were analyzed. Fifty patients scheduled to undergo arthroscopic knee surgery were randomly assigned to receive obturator nerve block using either the inguinal (n = 25) or the pubic tubercle approach (n = 25). RESULTS: In all cadavers, the needle was close to the obturator nerve branches, which were surrounded by the latex solution. In the clinical study, visual analog scale pain scores and discomfort of block placement were significantly lower in the inguinal group compared with the pubic tubercle group (P < 0.01). In the inguinal group, there was a significant decrease in block performance time (P < 0.05) and in bolus of propofol and fentanyl used for the procedure (P < 0.01). Twenty minutes after application of the block, adductor strength decrease, occurrence, and location of cutaneous distribution of the obturator nerve were not significantly different between the groups. The incidence of minor complications was significantly increased in the pubic tubercle group (P < 0.05). No major complications were observed. CONCLUSIONS: The new inguinal approach decreases patient discomfort and pain of block placement as well as the time and sedation and analgesics required for a similar quality of sensory and motor block compared with the pubic tubercle approach.
Occipital nerve block is usually considered to be a very simple and safe regional anaesthetic technique. We describe a case of sudden unconsciousness during a lesser occipital nerve block in a patient with an occipital bone defect. A 63-year-old man complained of headache, which was localized to the right occipital region. A right lesser occipital nerve block with a local anaesthetic was performed for treatment. During the lesser occipital nerve block, the patient suddenly became disturbed and lost consciousness. Two hours after the incident, the patient was fully awake without neurological sequelae. He had previously undergone a microvascular decompression for right trigeminal neuralgia. The patient had a bone defect following craniotomy. We believed that the loss of consciousness during lesser nerve block may be due to a subarachnoid injection. Occipital nerve block is relatively contraindicated in the presence of a bone defect.
In order to examine whether repeated sciatic nerve blocks showed tachyphylaxis and continuity of sciatic nerve with spinal cord affected development of tachyphylaxis when assayed in vivo by duration of depression compound action potentials (CAP), rats were anesthetized with halothane, ventilated, monitored and supported with stable hemodynamics and temperature. Posterior tibial nerve distally and sciatic nerve in thigh were exposed, placed on bipolar silver electrodes for stimulation and recording respectively. Three sequential sciatic nerve blocks were performed between these electrodes using 0.15 ml of 3% chloroprocaine. Nine rats were chosen to observe the effects of repeated sciatic nerve blocks on CAP. In another 18 rats, a second investigator exposed the sciatic nerve near its origin at spinal cord and randomly performed nerve cut and sham (n=9), and closed the incision blinding the electrophysiologic investigator. The results showed that electrical stimulated tibial nerve induced sciatic nerve Aalpha/beta, Adelta, C fiber mediated CAP waves. CAP amplitudes were remained stable during whole experimental procedure. CAP amplitudes were decreased completely with 3% chloroprocaine blocked sciatic nerve and recovered fully. The duration of CAP depression were reduced with repeated blocks. There were no selective blocked effects on Aalpha/beta, Adelta, C fiber mediated CAP. With sciatic nerve cut proximally, there was no statistical significant tachyphylaxis with 3% chloroprocaine repeated blocked sciatic nerve, and the duration of first and third blocked Adelta fiber mediated CAP was 108+/-20 and 92+/-14 min respectively (P>0.05). In normal rats the duration of first and third blocked Adelta fiber mediated CAP was 110+/-20 and 75+/-16 min respectively (P<0.05). It was suggested that tachyphylaxis to local anesthetics can occur in rats repeated blocked sciatic nerve when assayed in vivo by duration of depression CAP. The continuity of sciatic nerve with spinal cord is one of the important factors affecting the development of tachyphylaxis.
UNLABELLED: In 1973, Winnie et al. introduced the inguinal paravascular three-in-one block, which allegedly provides anesthesia of three nerves--the femoral, lateral cutaneous femoral, and obturator nerves--with a single injection. This concept was undisputed until the success of the obturator nerve block was reassessed by using evidence of adductor weakness rather than cutaneous sensory blockade, the latter being variable in its distribution and often absent. We performed this study, therefore, to evaluate the area of sensory loss produced by direct injection of local anesthetic around the obturator nerve. A selective obturator nerve block with 7 mL of 0.75% ropivacaine was performed in 30 patients scheduled for knee surgery. Sensory deficit and adductor strength were evaluated for 30 min by using sensory tests (cold and light-touch perception) and the pressure generated by the patient's squeezing a blood pressure cuff placed between the knees. Subsequently, a three-in-one block was performed, and the sensory deficit was reassessed. The obturator nerve block was successful in 100% of cases. The strength of adductors decreased by 77% +/- 17% (mean +/- SD). In 17 patients (57%), there was no cutaneous contribution of the obturator nerve. The remaining 7 patients (23%) had an area of hypoesthesia (cold sensation was blunt but still present) on the superior part of the popliteal fossa, and the other 6 (20%) had sensory deficit located at the medial aspect of the thigh. The three-in-one block resulted in blockade of the lateral aspect of the thigh in 87% of cases, whereas the anteromedial aspect was always anesthetized. By use of magnetic resonance imaging in eight volunteers, we demonstrated that the obturator nerve has already divided into its two branches at the site of local anesthetic injection. However, the injection of blue dye after having simulated the technique in five cadavers showed that the fluid regularly spread to both branches. We conclude that after three-in-one block, a femoral nerve block may have been assessed as an obturator nerve block in 100% of cases when testing the cutaneous distribution of the obturator nerve on the medial aspect of the thigh. IMPLICATIONS: Previous studies reporting an incidence of obturator nerve block after three-in-one block may have mistaken a femoral nerve block for an obturator nerve block in 100% of cases when the cutaneous distribution of the obturator nerve was assessed on the medial aspect of the thigh. The only way to effectively evaluate obturator nerve function is to assess adductor strength.
Femoral and sciatic nerve blocks have been used occasionally for unilateral total knee arthroplasty (TKA). In order to evaluate the effectiveness of this technique, combined femoral 3-in-1 and sciatic nerve blocks were performed in 20 cases of TKA, by the same surgeon. This surgeon also performed unilateral TKA under spinal anesthesia in another 20 cases. The anesthetic effectiveness of the two types of anesthesia was compared in terms of the time needed to complete the surgery, amount of intraoperative blood loss, and time interval until the first dose of analgesic. The results showed that the two types of anesthesia had comparable anesthetic effects. Ten of the 20 patients who had spinal anesthesia complained of postoperative urinary retention, while none of those who had nerve block had this complaint. Neither group experienced postpunctural headache, neurovascular damage, or drug-over-dose toxicity. We conclude that combined femoral 3-in-1 and sciatic nerve block is an effective anesthetic alternative for unilateral TKA.
Forty boys weighing less than 25 kg undergoing unilateral orchidopexy were randomly allocated to receive one of two analgesic regimens. Group C received a caudal epidural block with 0.25% bupivacaine 1 ml.kg-1 and preservative-free ketamine 0.5 mg.kg-1; Group L received an ilioinguinal nerve block with 0.25% bupivacaine 0.5 ml.kg-1 and infiltration of the wound with 0.25% bupivacaine 0.5 ml.kg-1. All subjects received diclofenac sodium 1-2 mg.kg-1 as a rectal suppository. Postoperative pain was assessed by means of a modified Objective Pain Score and analgesia was administered if this exceeded a value of 4. The median duration of analgesia was 10 h (range 2.6 to > 24 h) in Group C and 2.9 h (range 0.7 to > 24 h) in Group L (p < 0.05). There were no differences between groups in the incidence of motor block, urinary retention, postoperative vomiting or postoperative sedation. Subjects in Group L required significantly more doses of postoperative analgesia than those in Group C (p < 0.05).
Three techniques for blocking the sciatic nerve, differing in approach (posterior in group P; lateral in group L; and anterior in group A), were prospectively evaluated in 180 children who were also given light general anesthesia for surgery below the knee. Four anesthetic solutions with epinephrine (1% lidocaine, 0.5% bupivacaine, and two mixtures of 0.5% bupivacaine with either 1% lidocaine or 1% etidocaine) were administered to 15 patients in each group. The sciatic nerve was located by electrical stimulation or, when muscle twitches were not elicited, using a loss-of-resistance technique. Twitches were "typical" in 154 patients of whom 153 developed sciatic nerve block. In 26 patients twitches were atypical (eight patients) or absent (18 patients) and a sciatic block developed in only 13 patients (50%). The depth to which the needle was inserted was measured in each procedure; it varied according to patient's age and weight and was significantly less with the posterior approach than with either the lateral or anterior routes. The overall success rate exceeded 90% in the three groups but significantly fewer difficulties were encountered in group P than in group A. Although the spread of the anesthetic was different in the three groups, the distribution of anesthesia in the lower extremity was similar, including not only dermatomes supplied by the sciatic nerve, but also those supplied by the posterior femoral cutaneous nerve. No neurological sequelae were observed. It is concluded that the posterior and lateral approaches are the most suitable in children for blocking the sciatic nerve proximally.
Continuous extrapleural intercostal nerve block has been shown in a randomized, controlled study to be effective in reducing postoperative pain after thoracotomy and in restoring pulmonary mechanics. To assess the extent of spread of bupivacaine infused through an extrapleurally placed cannula inserted at thoracotomy, iohexol (Omnipaque) was infused at 5 days postoperatively in 5 patients and computed tomography performed. The contrast medium was confined to the paravertebral space covering on average six intercostal spaces. This study demonstrated that anatomically, the site of action of the bupivacaine infused through an extrapleural cannula was primarily in the paravertebral space.
Peripheral nerve blocks (PNBs) have an increasingly important role in ambulatory anesthesia and have many characteristics of the ideal outpatient anesthetic: surgical anesthesia, prolonged postoperative analgesia, and facilitated discharge. Critically evaluating the potential benefits and supporting evidence is essential to appropriate technique selection. When PNBs are used for upper extremity procedures, there is consistent opioid sparing and fewer treatment-related side effects when compared with general anesthesia. This has been demonstrated in the immediate perioperative period but has not been extensively investigated after discharge. Lower extremity PNBs are particularly useful for procedures resulting in greater tissue trauma when the benefits of dense analgesia appear to be magnified, as evidenced by less hospital readmission. The majority of current studies do not support the concept that a patient will have difficulty coping with pain when their block resolves at home. Initial investigations of outpatient continuous peripheral nerve blocks demonstrate analgesic potential beyond that obtained with single-injection blocks and offer promise for extending the duration of postoperative analgesia. The encouraging results of these studies will have to be balanced with the resources needed to safely manage catheters at home. Despite supportive data for ambulatory PNBs, most studies have been either case series or relatively small prospective trials, with a narrow focus on analgesia, opioids, and immediate side effects. Ultimately, having larger prospective data with a broader focus on outcome benefits would be more persuasive for anesthesiologists to perform procedures that are still viewed by many as technically challenging.
OBJECTIVE: The degree of pulpal anesthesia obtained with an ultrasound-assisted inferior alveolar nerve block was compared to that obtained with a conventional inferior alveolar nerve block for mandibular teeth to determine whether needle placement assisted by ultrasound results in more successful anesthesia. STUDY DESIGN: Through use of a repeated-measures design, each of 40 subjects randomly received an ultrasound-assisted inferior alveolar nerve block and a conventional inferior alveolar nerve block at 2 separate appointments. Mandibular anterior and posterior teeth were blindly tested by means of a pulp tester at 4-minute cycles for 60 minutes postinjection. Anesthesia was considered successful when 2 consecutive readings of 80 were obtained. RESULTS: One hundred percent of the subjects had profound lip numbness with both the ultrasound-assisted inferior alveolar nerve block and the conventional inferior alveolar nerve block. For these 2 techniques, anesthetic success rates for individual teeth ranged from 38% to 92%. There were no significant differences (P > .05) between the 2 techniques. CONCLUSIONS: It was concluded that accurate needle placement with ultrasound for the inferior alveolar nerve block did not result in more successful pulpal anesthesia in the mandible. Therefore, accuracy of needle placement is not the primary reason for pulpal anesthetic failure with this block.
INTRODUCTION: Combining adductor canal block (ACB), infiltration between the popliteal artery and posterior capsule of the knee (IPACK), and genicular nerve blocks provides motor-sparing analgesia in total knee arthroplasty (TKA). Adding nerve blocks targeting the nerve to vastus medialis, vastus intermedius, and anterior femoral cutaneous nerve may improve postoperative pain management without affecting mobility. This study evaluated the effect of an eight-nerve block combination for pain relief after TKA versus local infiltration analgesia (LIA). METHODS: Participants were randomized into intervention or standard treatment groups. The intervention group received an eight-nerve block combination using 40 mL ropivacaine, 5 mg/mL, with 75 µg of clonidine. The control group received LIA comprising 150 mL ropivacaine, 2 mg/mL, supplemented with 0.5 mg adrenaline. The primary outcome was postoperative pain intensity, measured by the numeric rating scale (NRS) at postanesthesia care unit (PACU) arrival, 1 hour, 2 hours after PACU arrival, at ward arrival, evening of surgery, morning of postoperative day 1 (POD1), and at 14:00 POD1. Statistical analysis was performed using the Mann-Whitney U test. Secondary outcomes included 48-hour oral morphine equivalent (OME) consumption and length of hospital stay (LOS). RESULTS: A total of 217 patients scheduled for TKA were randomized. No significant differences were observed in the primary outcome. NRS at rest, presented as median (IQR), did not differ between groups at any time point. At PACU arrival 0 (0-3) vs 0 (0-4), at 1 hour 2 (0-4) vs 2 (0-5), at 2 hours 2 (0-6) vs 2.5 (0-4), at ward arrival 3 (2-5) vs 3 (2-5), on the evening of POD0 4 (3-5) vs 3.5 (2-6), on the morning of POD1 4 (3-6) vs 4 (2-5), and at 14:00 POD1 3 (2-5) vs 3 (2-5) for nerve block and LIA groups, respectively (all P > .05). Exploratory secondary outcomes indicated reduced 48-hour OME consumption presented as median (IQR), 70 mg (52.5-96.3), vs 96 mg (61.3-148.8); P = .008) and shortened hospital stay, median (IQR), 1 day (1-2), vs 2 days, (1-3); P < .001) in the nerve block group compared to the LIA group. CONCLUSIONS: No differences were observed in pain scores between the eight-nerve block combination and LIA. Secondary outcomes revealed a reduction in 48-hour opioid consumption and a modestly shorter hospital stay with nerve block compared to LIA.