Spinal anesthetic agents

Lidocaine, tetracaine, and bupivacaine are the local anesthetic agents most commonly employed for spinal anesthesia in the U.S. Lidocaine provides a short duration of anesthesia and is primarily useful for surgical and obstetrical procedures lasting less than one hour. Tetracaine and bupivacaine are used for procedures lasting 2 to 5 hours. Tetracaine appears to provide a somewhat longer duration of anesthesia and a more profound degree of motor block than does bupivacaine. On the other hand, compared with tetracaine, bupivacaine has been demonstrated to be associated with a decreased incidence of hypotension. In addition, bupivacaine may be better than tetracaine for use in orthopedic surgical procedures since it appears to be associated with a lower incidence of tourniquet pain. Vasoconstrictors can prolong the duration of spinal anesthesia of all three agents. However, the greatest duration is seen when vasoconstrictors are added to tetracaine solutions. Lidocaine and bupivacaine do not appear to benefit as much from the addition of vasoconstrictors. In general, the local anesthetic agents that are currently available for spinal anesthesia provide significant versatility. By carefully considering the planned surgical procedure, the surgeon's requirements, and the patient's characteristics (e.g., age, height, gravidity), and by understanding the factors that influence spinal anesthesia, the anesthesiologist can select a local anesthetic agent that will assure adequate and satisfying spinal anesthesia.     

Decreased incidence of tourniquet pain during spinal anesthesia with bupivacaine. A possible explanation

In a previous report, the incidence of tourniquet pain was found to be 25% with bupivacaine and 60% with tetracaine (P less than 0.05) spinal anesthesia. On the other hand, tetracaine is more potent than bupivacaine in abolishing the single-compound action potential in vitro in isolated nerves. These conflicting observations may be reconciled if bupivacaine produced greater frequency-dependent conduction blockade of nerve action potentials. This hypothesis was tested in C fibers of isolated, desheathed rabbit vagus nerves. The nerves were supramaximally stimulated at frequencies of 9 or 15 Hz. After a control period, the nerves were exposed to bupivacaine (0.2 mM) or tetracaine (0.02 mM) for 30 minutes. The local anesthetics were then washed out by continuous constant-rate perfusion. The decline and recovery of the first and last action potential amplitudes of the train were measured. Bupivacaine and tetracaine produced similar depression of the first action potential of the 9-Hz and 15-Hz trains. However, bupivacaine caused a delayed recovery of the last action potential of the 15-Hz train but not of the 9-Hz train. These results show that bupivacaine produces greater frequency-dependent conduction blockade of C fibers than does tetracaine. These findings offer a possible explanation as to why spinal anesthesia with bupivacaine results in a lower incidence of tourniquet pain than tetracaine.     

Bupivacaine-sparing effect of fentanyl in spinal anesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES: Visceral pain decreases in cesarean patients under spinal anesthesia when the dose of local anesthetic is increased. However, larger doses of local anesthetic are associated with higher sensory blocks. We hypothesized that the addition of fentanyl could reduce the dose of bupivacaine necessary to achieve adequate surgical anesthesia. METHODS: Two double-blinded, sequential, prospective studies were performed on 120 patients. In the preliminary study, the patients received 8, 10, or 12 mg of 0.5% hyperbaric bupivacaine intrathecally. In the second, main study, they received each bupivacaine dose with 10 microg of fentanyl. Each group consisted of 20 patients, and the groups were identified as B8, B10, B12, BF8, BF10, and BF12. Sensory and motor block, intraoperative pain defined by visual analogue scale (VAS), muscle relaxation, and side effects were assessed. We also measured the sensory and motor recovery and the onset of pain in the postanesthesia care unit (PACU). RESULTS: Maximal block level and incidence of high block (> or = T1) were higher in the 12-mg groups. There was intraoperative pain in 35% of the B8 patients and 20% of the B10 patients, but none in the B12 patients and all fentanyl groups. Incidences of other side effects were not different. The addition of fentanyl to bupivacaine significantly delayed the onset of postoperative pain and sensory recovery, but motor recovery time did not change with additional fentanyl. Conclusions: The optimal dose of hyperbaric bupivacaine to produce surgical anesthesia was 12 mg, which was accompanied by high sensory block. With the addition of 10 microg of fentanyl, the dose of bupivacaine could be reduced to 8 mg in spinal anesthesia for cesarean delivery.     

7-year survey of anesthesia for cesarean section--comparison of tetracaine and bupivacaine as intrathecal anesthetic agents

BACKGROUND: In our institution, spinal anesthesia is the first choice for cesarean section. After the introduction of bupivacaine in 2000 in Japan, the intrathecal anesthetic agent shifted from tetracaine to bupivacaine. We analyzed the anesthesia for cesarean section in recent 7 years and compared the anesthetic quality of tetracaine with that of bupivacaine. METHODS: The anesthetic records were reviewed in the patients who had received cesarean section between January 1998 and December 2004 at our institution. RESULTS:There were 10456 deliveries during the study period with a cesarean section rate of 28.2% (2947 cases). Ninety-one percent of cesarean section was performed under spinal anesthesia. Spinal anesthetic agent shifted from tetracaine to bupivacaine in 2000-2001, both of which was prepared as a hyperbaric solution and supplemented with 0.1 mg of morphine hydrocloride. Of the 2711 patients in whom a cesarean section was started under spinal anesthesia, 20 (0.7%) required conversion to general anesthesia. Three hundred eighteen patients (11.7%) required some analgesic supplementation. The incidence of intra-operative analgesic supplementation was greater in the patients anesthetized with hyperbaric tetracaine and morphine than in those anesthetized with hyperbaric bupivacaine and morphine (22.96% vs 4.20% ; P<0.01). The conversion rate from spinal to general anesthesia for cesarean section was 0.7%. CONCLUSIONS: Comparing these two intrathecal anesthetic agents, the rate of analgesic supplementation in those anesthetized with bupivacaine was lower than in those anesthetized with tetracaine. This suggests that bupivacaine provides the more profound blockade of the visceral pain than tetracaine, and is superior as a local anesthetic.     

Comparison of 0.5% ropivacaine and 0.5% bupivacaine for epidural anesthesia in patients undergoing lower-extremity surgery

Ropivacaine is an amide local anesthetic structurally related to, but appearing less cardiotoxic, than bupivacaine. The authors' investigation was designed in a randomized, double-blind fashion to compare the clinical effectiveness of ropivacaine and bupivacaine in patients undergoing lower-extremity surgery. Forty-five patients were randomized to receive 20 ml of 0.5% ropivacaine or bupivacaine. Intermittent sensory (pinprick) and motor (Bromage score) measurements were made while the block was in effect, and changes in heart rate, blood pressure and amounts of additional analgesics, sedatives and other medications were also recorded. Presence of tourniquet pain and the quality of anesthesia were also assessed. One patient was excluded from analysis; thus, 22 patients each received ropivacaine or bupivacaine. No differences were found in patient or perioperative characteristics between the groups. The quality and extent of sensory and motor blockade between groups were comparable, although bupivacaine was slightly longer acting. Cardiovascular changes, incidence of tourniquet pain, and the amounts of supplemental medications necessary were also similar between groups. The authors found 0.5% ropivacaine and bupivacaine to be clinically similar in both sensory- and motor-blocking characteristics, with the exception that bupivacaine produced a blockade of slightly longer duration. Because ropivacaine is reported to be less cardiotoxic than bupivacaine in animal studies, the similarity of clinical epidural anesthesia may make ropivacaine the preferred agent.     

Incidence of visceral pain during cesarean section: the effect of varying doses of spinal bupivacaine

The safety of 0.5% hyperbaric bupivacaine, as well as the incidence and severity of visceral pain, were evaluated in 36 women undergoing elective cesarean section under spinal anesthesia who, randomly divided into two groups, received different dose ranges according to height, 7.5-10 mg in group A and 10-12.5 mg in group B. When sensory block to at least the fourth thoracic dermatome was established, surgery was begun and the occurrence and severity of visceral pain recorded (visual analog scale) by an observer unaware of patient data. The level of analgesia to pinprick was determined when and if there was onset of pain intraoperatively, and supplementary medication was administered as needed. Hypotension, the incidence of which was similar in both groups, was treated as necessary with ephedrine. No patients experienced pain until after delivery of the infant. Thereafter, moderate to severe pain, in association with peritoneal traction, occurred in 12 patients in group A (70.5%) but only in 6 patients in group B (31.6%). In patients experiencing moderate to severe pain, the mean time between induction of anesthesia and onset of pain was similar in both groups, as was the amount of systemic narcotic given. Total time for regression of sensory analgesia to L5 was longer in patients in group B (243.9 versus 195.4 min), and the incidence of complete motor blockade was greater in group B. Increasing the amount of 0.5% hyperbaric bupivacaine per spinal segment reduces the occurrence of moderate to severe visceral pain during elective cesarean section without jeopardizing mother or fetus.     

Addition of glucose to bupivacaine in spinal anesthesia increases incidence of tourniquet pain

The effect of baricity of 0.5% bupivacaine on the incidence of tourniquet pain when used for spinal anesthesia was evaluated in 60 patients undergoing orthopedic surgery. Three ml of either hyperbaric (8% glucose) or isobaric (glucose-free) solution was used. A standard 7-cm orthopedic tourniquet was applied at the thigh and was inflated to 300 mm Hg for 2 hr or until the patient experienced pain from the tourniquet. During application time, the levels of sensory block to pin prick were similar in the groups. The incidence of tourniquet pain in the glucose-free group (4/30) was significantly lower than in the hyperbaric group (11/30).     

Time-courses of zones of differential sensory blockade during spinal anesthesia with hyperbaric tetracaine or bupivacaine

The purposes of this study were twofold: to compare bupivacaine and tetracaine spinal anesthesia with regard to the zones of differential sensory blockade and to evaluate the time-courses of the widths of the zones of differential sensory blockade during spinal anesthesia. In 51 patients, the most rostral levels of sensory denervation to light touch, pinprick, and temperature discrimination were measured. There was no statistically significant difference in the height of sensory blockade in the 29 patients given bupivacaine and in the 22 patients given equipotent doses of tetracaine. The widths of the zones of differential blockade were also not statistically different between the two groups during onset, maintenance, and regression of anesthesia, except that the light touch-to-pinprick and light touch-to-temperature zones of differential blockade were greater with bupivacaine than with tetracaine 30 min after subarachnoid injection. The width of the zones of differential blockade also remained unchanged within each group during onset, maintenance, and regression of anesthesia. Changes in, and absolute levels of, blood pressure and heart rate were similar with both bupivacaine and tetracaine throughout. We conclude that zones of differential sensory blockade are essentially the same with tetracaine and bupivacaine, that the widths of the zones of differential sensory blockade remain constant during onset, maintenance, and offset of spinal anesthesia, and that bupivacaine and tetracaine are associated with similar changes in heart rate and blood pressure during spinal anesthesia.     

Failure of spinal anesthesia. Evaluation of the practice at a university hospital

There is little data concerning failures in spinal anaesthesia. A retrospective analysis of 337 spinal anaesthesias performed in a teaching hospital gave a 9.8% failure rate. A failure was defined as the need to carry out part or all of a surgical act under general anaesthesia when spinal anaesthesia had been carried out. The main causes of failure were insufficiently or excessively extended neural blockade, insufficient duration or a poor quality sensory blockade with the patient feeling surgical or tourniquet pain. The local anaesthetics used were hyperbaric 0.5% tetracaine with and without 0.1 mg metaraminol, hyperbaric 0.5% prilocaine and isobaric 0.5% bupivacaine. The failure rate was 19.4% with plain hyperbaric tetracaine, 7.6% with tetracaine with metaraminol, 5% with prilocaine and 2.9% with isobaric bupivacaine. This rate was related neither to the experience of the anaesthetist, nor to the clinical features of the patients, nor to the position nor to the needle size. Although there were more failures during orthopaedic procedures, probably because of tourniquet pain, this was not significant. These results confirmed that spinal anaesthesia was a reliable technique. Hyperbaric plain tetracaine did not always guarantee a successful anaesthesia and isobaric bupivacaine should be more commonly used.     

Hypotension in spinal anesthesia: a comparison of isobaric tetracaine with epinephrine and isobaric bupivacaine without epinephrine

Two isobaric spinal anesthetic solutions (bupivacaine 0.5%/20 mg without epinephrine and tetracaine 0.5%/15 mg with 0.2 mg epinephrine) were compared in a double-blind study of 60 patients. Patients were injected while in the lateral recumbent position and were immediately turned supine and horizontal. Up to 30 min after injection, no differences were found between the groups regarding segmental level of analgesia, changes in heart rate, and onset to or maximum decrease in mean arterial pressure (MAP). No correlation was found between maximum decrease in MAP and level of analgesia. At time of maximum decrease in MAP (tetracaine group - 16.7 +/- 12.8% (mean + SEM), bupivacaine group -19.4 + 14.8%) the level of analgesia was significantly higher in the tetracaine group (T5-6) than in the bupivacaine group (T7-8). Hypotension occurred in five patients in the bupivacaine group and in six in the tetracaine group. Two patients in the tetracaine group (but none in the bupivacaine group) had bradycardia. Hypotension together with bradycardia was observed in one patient in the tetracaine group but in no patient in the bupivacaine group. Two patients in each group developed postlumbar puncture headache. The authors conclude that the choice of local anesthetic agent, by itself, is not the sole cause of hypotension seen with spinal anesthesia.     

舒芬太尼复合小剂量布比卡因蛛网膜下腔麻醉在老年患者手术中的应用

目的观察舒芬太尼复合小剂量布比卡因蛛网膜下腔注射在老年患者麻醉中的临床效果。方法 60例择期行下腹部或下肢手术患者,随机分为三组,每组20例。Ⅰ组:0.5%布比卡因7.5mg+舒芬太尼5μg,Ⅱ组:0.5%布比卡因7.5mg+舒芬太尼2.5μg,Ⅲ组:0.5%布比卡因10mg行蛛网膜下腔麻醉。观察感觉阻滞起效时间、感觉阻滞平面上界、镇痛维持时间、运动阻滞起效时间、运动阻滞程度、血流动力学影响及不良反应发生情况。结果Ⅰ、Ⅱ组给药后血流动力学影响小,运动阻滞恢复时间短于Ⅲ组,恶心、头晕发生率明显低于Ⅲ组(P<0.05);Ⅰ组感觉阻滞起效时间,达T10时间明显短于Ⅱ组和Ⅲ组,T10镇痛维持时间明显长于Ⅱ组和Ⅲ组(P<0.05)。结论舒芬太尼2.5、5μg复合小剂量布比卡因蛛网膜下腔注射用于老年患者均可产生良好的感觉和运动阻滞,且对血流动力学影响小。     

Surgical repair of hip fractures using continuous spinal anesthesia: comparison of hypobaric solutions of tetracaine and bupivacaine

The aim of this study was to compare hypobaric solutions of tetracaine and bupivacaine in 30 geriatric patients undergoing surgical repair of hip fractures while under continuous spinal anesthesia. Tetracaine 1% and bupivacaine 0.5% were mixed with distilled water to prepare hypobaric 0.25% solutions. In a double-blind fashion, all patients received 3 ml (7.5 mg) of either solution in the lateral decubitus position with the operated side up, the table being kept horizontal for 30 minutes after injection. The mean highest sensory levels in both groups, and in both operated and non-operated sides in the same group, were comparable, ranging between T7 and T8.5. Duration of analgesia was 134 minutes with tetracaine and 130 minutes with bupivacaine (NS). In both groups, motor blockade was satisfactory in 29/30 patients on the operated side. The frequency of a decrease in systolic blood pressure of more than 30% was similar in the two groups. The authors conclude that hypobaric solutions of both tetracaine and bupivacaine are suitable for surgical repair of hip fractures in geriatric patients and produce comparable anesthetic and hemodynamic effects.     

Isobaric spinal anaesthesia with bupivacaine and tetracaine (author's transl)]

4 ml 0.5% solutions of bupivacaine and tetracaine without the addition of a vasoconstrictor, approximately isobaric, were used for spinal anaesthesia on patients in the sitting position. The sensory and motor block due to the two local anesthetics was tested and compared. The mean time on onset of complete analgesia was the same for both local anaesthetics (9 and 11 min), as was also the highest level of analgesia (T10). The duration of maximal extension of analgesia was on an average 45 min longer due to tetracaine (bupivacaine 105 min, tetracaine 150 min). The duration of maximal spread of the blocked sensation of pain, temperature, pressure and touch was similar for each of both local anesthetics. The regression of these sensory qualities, blocked in a dissoaciated manner, took a parallel course. With tetracaine the motor block of the lower extremities developed faster and lasted longer (Bromage 3 for bupivacaine 192 min, for tetracaine 220 min). Motor function and proprioception normalized in a synchronized manner. Isobaric spinal anaesthesia with these two solutions of local anaesthetics was found to be reliable and controllable, especially when administered to the sitting patient. Tetracaine is a good alternative to bupivacaine, currently controversial for intrathecal use.     

Differential spread of blockade of touch, cold, and pinprick during spinal anesthesia

The differential levels of sensory blockade of pinprick, cold, and touch were monitored throughout the course of spinal anesthesia administered to 50 patients to determine variations in the degree of spread during onset, plateau, and regression, and to establish the effects of epinephrine and the effect of posture during injection. A significant difference was observed between the dermatomal level of sensory loss of touch and the dermatomal level of loss of either pinprick or cold during onset, at 5 min in patients given tetracaine with epinephrine, at time of maximum spread in patients given tetracaine with epinephrine or in the sitting position, and in all groups during regression. Loss of touch began later, never extended as far cephalad, and regressed sooner. The extent of this difference was greatest during regression, when the anesthetic was given to patients in the sitting position, after epinephrine. The level at which the sense of touch was lost seemed to mark the limits of the zone of solid spinal anesthesia; these limits could not be assessed effectively using pinprick. We propose that loss of touch sensation be used to assess whether anesthesia is adequate to avoid tourniquet pain. If there is loss of touch sensation above the L1 dermatome, it is unlikely that tourniquet pain will occur.     

Hyperbaric spinal ropivacaine: a comparison to bupivacaine in volunteers

BACKGROUND: Ropivacaine is a newly introduced local anesthetic that may be a useful alternative to low-dose bupivacaine for outpatient spinal anesthesia. However, its relative potency to bupivacaine and its dose-response characteristics are unknown. This double-blind, randomized, crossover study was designed to determine relative potencies of low-dose hyperbaric spinal ropivacaine and bupivacaine and to assess the suitability of spinal ropivacaine for outpatient anesthesia. METHODS: Eighteen healthy volunteers were randomized into three equal groups to receive one spinal administration with bupivacaine and a second with ropivacaine, of equal-milligram doses (4, 8, or 12 mg) of 0.25% drug with 5% dextrose. The duration of blockade was assessed with (1) pinprick, (2) transcutaneous electrical stimulation, (3) tolerance to high tourniquet, (4) electromyography and isometric force dynamometry, and (5) achievement of discharge criteria. Differences between ropivacaine and bupivacaine were assessed with linear and multiple regression. P < 0.05 was considered significant. RESULTS: Ropivacaine and bupivacaine provided dose-dependent prolongation of sensory and motor block and time until achievement of discharge criteria (R2 ranges from 0.33-0.99; P values from < 0.001 through 0.01). Spinal anesthesia with ropivacaine was significantly different from bupivacaine and was approximately half as potent for all criteria studied. A high incidence of back pain (28%; P = 0.098) was noted after intrathecal ropivacaine was given. CONCLUSION: Ropivacaine is half as potent and in equipotent doses has a similar profile to bupivacaine with a higher incidence of side effects. Low-dose hyperbaric spinal ropivacaine does not appear to offer an advantage over bupivacaine for use in outpatient anesthesia.     

The Addition of Phenylephrine Contributes to the Development of Transient Neurologic Symptoms after Spinal Anesthesia with 0.5% Tetracaine

Background: Recent reports indicate that transient neurologic symptoms commonly occur after single-injection spinal anesthesia with lidocaine. Information regarding tetracaine has been limited to a single case report. In addition, little is known about the cause of these symptoms or the cofactors that affect their occurrence. The present study sought to determine whether the presence of phenylephrine or the concentration of glucose in the anesthetic solution affects the incidence of transient neurologic symptoms after spinal anesthesia with 0.5% tetracaine.

Methods: One-hundred sixty patients classified as American Society of Anesthesiologists physical status I or II who were scheduled for elective surgery on a lower limb or perineum were sequentially assigned to one of four equal groups to receive intrathecal 0.5% tetracaine in 7.5% or 0.75% glucose, with or without 0.125% phenylephrine. Patients were evaluated on postoperative day one for the presence of pain, dysesthesia, or both in the legs or buttocks by an investigator unaware of the drug given.

Results: Symptoms were present in 10 patients (12.5%) receiving a spinal anesthetic containing phenylephrine, but in only one patient (1.3%) receiving spinal anesthesia without phenylephrine. There was no significant difference in the incidence of symptoms between groups receiving 7.5% glucose and those receiving 0.75% glucose (8.8% and 5% of patients, respectively).     

A comparison of intrathecal plain solutions containing ropivacaine 20 or 15 mg versus bupivacaine 10 mg

Ropivacaine, which blocks sensory nerve fibers more readily than motor fibers, is considered to be less potent than bupivacaine. Our hypothesis was that, when used in spinal anesthesia for day surgery, ropivacaine 15 and 20 mg would provide faster motor recovery than bupivacaine 10 mg. This prospective, randomized, double-blinded study included 90 ambulatory lower-extremity surgery patients who received 2 mL of ropivacaine 1%, ropivacaine 0.75%, or bupivacaine 0.5%. Motor block was tested with the Bromage scale, and sensory block was tested with pinprick. Ropivacaine 15 mg provided faster recovery of motor block (150 min) than did bupivacaine 10 mg (210 min; P = 0.005), but the median duration of sensory block at T10 (140 min) did not differ significantly from that with bupivacaine 10 mg (140 min). The median duration of sensory block at T10 was significantly longer with ropivacaine 20 mg (170 min) than with bupivacaine 10 mg (140 min; P = 0.005), but the median recovery from motor block (210 min) did not differ significantly. We conclude that the duration of sensory block of ropivacaine was two thirds and the duration of motor block was half when compared with bupivacaine, with calculations based on the duration-per-milligram of the local anesthetic.     

罗哌卡因蛛网膜下腔阻滞在剖宫产术中的应用

目的观察不同浓度罗哌卡因用于蛛网膜下腔阻滞剖宫产术的麻醉效能、母婴安全和相关不良反应。方法采用随机双盲法,将60例剖宫产手术的足月单胎产妇均分为三组：0．5％罗哌卡因组（L1组）,0．75％罗哌卡因组（L2组）和0．5％布比卡因组（C组）。记录蛛网膜下腔阻滞后产妇的感觉阻滞和运动阻滞的起效和持续时间、麻醉质量评价、恶心呕吐等不良反应及术中HR、BP、SpO2和新生儿1min和5min Apgar评分。结果L1和L2组比C组起效慢,阻滞平面低,平面固定时间长。L2组感觉阻滞时间比L1组和C组长。L2组和C组肌松评分优于L1组。运动神经阻滞改良Bromage评分,L1组〈k组〈C组（P〈0．05）。三组术中低血压及其他不良反应发生率差异无统计学意义。结论0．75％罗哌卡因用于蛛网膜下腔阻滞剖宫产时,其麻醉效能弱于0．5％布比卡因,而强于0．5％罗哌卡因,三者均具有较好的安全性。     

Regional anaesthetic technique and the incidence of tourniquet pain

The influence of regional anaesthetic technique on the incidence of lower extremity tourniquet pain was evaluated. We studied 60 patients undergoing orthopaedic procedures of the lower extremity with the use of a pneumatic tourniquet and anticipated inflation of 60 min or longer. Three different anaesthetic techniques were selected by random card draw: spinal anaesthesia (SAB) with plain 0.5% bupivacaine (15 mg) and 0.2 mg epinephrine added, lumbar epidural anaesthesia (EA) with 2% mepivacaine and 1:200,000 epinephrine added, and epidural anaesthesia (AEA) with the same solution alkalinized with bicarbonate. Onset and level of sensory blockade were determined by loss of painful sensation to pinprick. The incidence of tourniquet pain was determined at 15-min intervals or by patient complaint, by an observer unaware of group. Time to onset of pain, amount of treatment (iv fentanyl), and sensory level at the time of pain were determined. The SAB was compared with EA and AEA, and EA was compared with AEA. The SAB group was older. The sensory level achieved and duration of tourniquet inflation did not differ among groups. The incidence of tourniquet pain was lower with SAB than with EA and lower with AEA than with EA. There was no difference between SAB and AEA. This study demonstrated a lower incidence of tourniquet pain with spinal anaesthesia than with epidural anaesthesia to the same sensory level. However, this advantage is eliminated if the epidural anaesthetic was performed with an alkalinized local anaesthetic.     

Adding dexmedetomidine to lidocaine for intravenous regional anesthesia

Dexmedetomidine is approximately 8 times more selective toward the alpha-2-adrenoceptors than clonidine. It decreases anesthetic requirements by up to 90% and induces analgesia in patients. We designed this study to evaluate the effect of dexmedetomidine when added to lidocaine in IV regional anesthesia (IVRA). We investigated onset and duration of sensory and motor blocks, the quality of the anesthesia, intraoperative-postoperative hemodynamic variables, and intraoperative-postoperative pain and sedation. Thirty patients undergoing hand surgery were randomly assigned to 2 groups to receive IVRA. They received 40 mL of 0.5% lidocaine and either 1 mL of isotonic saline (group L, n = 15) or 0.5 microg/kg dexmedetomidine (group LD, n = 15). Sensory and motor block onset and recovery times and anesthesia quality were noted. Before and after the tourniquet application at 5, 10, 15, 20, and 40 min, hemodynamic variables, tourniquet pain and sedation, and analgesic use were recorded. After the tourniquet deflation, at 30 min, and 2, 4, 6, 12, and 24 h, hemodynamic variables, pain and sedation values, time to first analgesic requirement, analgesic use, and side effects were noted. Shortened sensory and motor block onset times, prolonged sensory and motor block recovery times, prolonged tolerance for the tourniquet, and improved quality of anesthesia were found in group LD. Visual analog scale scores were significantly less in group LD in the intraoperative period and 30 min, and 2, 4, and 6 h after tourniquet release. Intra-postoperative analgesic requirements were significantly less in group LD. Time to first analgesic requirements was significantly longer in group LD in the postoperative period. We conclude that the addition of 0.5 microg/kg dexmedetomidine to lidocaine for IVRA improves quality of anesthesia and perioperative analgesia without causing side effects. IMPLICATIONS: This study was designed to evaluate the effect of dexmedetomidine when added to lidocaine for IV regional anesthesia. This is the first clinical study demonstrating that the addition of 0.5 microg/kg dexmedetomidine to lidocaine for IV regional anesthesia improves quality of anesthesia and intraoperative-postoperative analgesia without causing side effects.