Hospital discharge after ambulatory knee arthroscopy: A comparison of epidural 2-chloroprocaine versus lidocaine.

BACKGROUND AND OBJECTIVES: This prospective, randomized, double-blind study compares the efficacy of epidural 2-chloroprocaine and lidocaine for attaining hospital discharge criteria after ambulatory knee arthroscopy. We hypothesized that 2-chloroprocaine would facilitate earlier discharge than lidocaine. METHODS: American Society of Anesthesiologists (ASA) I and II patients were randomized to receive equipotent doses of epidural 3% 2-chloroprocaine or 1.5% lidocaine, both without epinephrine. Time to block resolution and discharge were compared between groups, along with the need for epidural reinjection, surgical times, and postoperative back pain. RESULTS: Twenty-seven patients completed the study, 13 in the 2-chloroprocaine group and 14 in the lidocaine group. The 2-chloroprocaine group was ready for discharge significantly earlier than the lidocaine group (130 +/- 17 min [range, 105 to 160] v 191 +/- 32 min [range 144 to 251]; P <.0001, 90% power). The lidocaine group required more epidural reinjections. Anesthesia-related side effects were similar in both groups. CONCLUSIONS: Epidural 3% 2-chloroprocaine without epinephrine is an advantageous choice for ambulatory knee arthroscopy. It enables readiness for discharge an hour sooner than 1.5% lidocaine, requires fewer reinjection interventions, and may reduce delayed discharge secondary to prolonged time to void. This clinical study shows the superiority of epidural 3% 2-chloroprocaine over 1.5% lidocaine for expediting hospital discharge after ambulatory surgery.

Continuous spinal anaesthesia for abdominal surgery in a patient receiving amiodarone.

The perioperative management of a 57-yr-old patient receiving chronic amiodarone therapy with a continuous spinal anaesthetic for a low anterior resection of the colon is discussed. The most appropriate anaesthetic technique for patients receiving chronic amiodarone therapy remains controversial, but the avoidance of general anaesthesia may be beneficial because of the risk of postoperative pulmonary failure. In this patient continuous spinal anaesthesia was slowly titrated to the desired level, coincident haemodynamic alterations were easily treated as they developed, and high serum local anaesthetic concentrations which occur with other regional anaesthetic techniques were avoided.

Chloroprocaine and lidocaine decrease hospital stay and admission rate after outpatient epidural anesthesia.

Lumbar epidural anesthesia with 20 ml of either 3% 2-chloroprocaine (C), 1.5% lidocaine (L), or 1.5% mepivacaine (M) with epinephrine was studied in 84 outpatients undergoing surgery (extracorporeal shock wave lithotripsy (ESWL]. The average duration of the procedure was 31.9 minutes. The total duration of sensory anesthesia was 133 +/- 28 minutes (C), 182 +/- 38 (L), and 247 +/- 42 (M) (p less than 0.05). Times to discharge were 269 +/- 62 minutes (C), 284 +/- 62 (L), and 357 +/- 71 (M). The time to discharge with M, almost six hours, was significantly longer than with C or L. There was a trend to an increasing rate of unplanned overnight hospital admission with increasing duration of the local anesthetic drug employed. Continuous epidural anesthesia with C, L or M appears safe and effective for outpatient surgical procedures such as ESWL. In contrast to previous understanding, mepivacaine produces significantly longer anesthesia and recovery times and may not be optimal for outpatient epidural use.

Effect of clonidine on lidocaine clearance in vivo: a microdialysis study in humans.

BACKGROUND: The addition of clonidine to local anesthetics has been shown to prolong both peripheral and central neuraxial local anesthetic blocks. Whether clonidine prolongs local anesthetic block by a pharmacokinetic effect or a pharmacodynamic effect is unclear. By directly measuring lidocaine tissue concentrations at the site of injection in the presence and absence of clonidine, this study was designed to address this question. METHODS: Microdialysis probes were placed adjacent to the superficial peroneal nerve in both feet of seven volunteers. Plain lidocaine (1%) was injected along one nerve, and lidocaine with clonidine (10 microg/ml) was injected along the other nerve in a double-blind, randomized manner. The extracellular fluid was then sampled for lidocaine concentration at 5-min intervals using microdialysis, cutaneous blood flow was assessed by laser Doppler at 10-min intervals, and sensory block was assessed every 10 min until resolution. RESULTS: Consistent with previous studies, clonidine prolonged lidocaine sensory block. Blood flow increased in both groups but was significantly lower in the clonidine group, especially during the first 60 min. Consistent with the lower blood flow, the area under the lidocaine concentration-versus-time curve was significantly greater in the clonidine group during the first 60 min. CONCLUSION: When added to lidocaine, clonidine prolonged peripheral nerve block. The pharmacokinetic data suggest that the mechanism of prolongation is at least in part pharmacokinetic.

Training anesthesia personnel to perform bleeding times.

Template bleeding time results generated by residents in anesthesiology correlate well with those obtained by trained laboratory personnel (p less than 0.002). Anesthesia personnel can accurately perform bleeding time tests when laboratory support is not available. The results of these tests can be used to guide clinical decisions.

Comparison of needle deviation during regional anesthetic techniques in a laboratory model.

Although many characteristics of needles used for spinal and epidural anesthesia have been studied extensively, the amount that a needle deviates from a straight path while passing through tissue has been relatively ignored. A laboratory model was used to determine the amount of needle deviation produced when different types of new spinal needles and epidural needles were passed through porcine tissue. Both needle point design and, to a lesser extent, needle gauge were found to influence the amount and direction of needle deviation. Deviation was found to be the least for the pencil-point spinal needles (Whitacre, Sprotte, Safetap, range 0.60-1.00 mm/50 mm tissue, analysis of variance (ANOVA) P < 0.001). Needles commonly used for epidural anesthesia (Tuohy, Hustead, Crawford) exhibited increased deviation (range 1.73-3.54 mm/50 mm tissue), although the largest amount was seen with beveled spinal needles (Quincke, Atraucan) (range 4.42-5.90 mm/50 mm tissue). The possible clinical significance of needle deviation during the performance of a regional anesthetic is discussed.

Are anesthesia residency programs failing regional anesthesia? The past, present, and future.

BACKGROUND: A survey of anesthesia training programs in 1980 reported the use of a regional anesthetic technique in 21.3% of cases. Since that time, numerous changes have occurred in anesthesia residency programs. This survey was conducted to assess the impact these changes have had on the use and teaching of regional anesthetic techniques in residency training programs. METHODS: All anesthesia residency program directors were requested to send blinded copies of their residents' 1989-1990 American Board of Anesthesiology Annual Training Report Forms. Data from responding programs were compared to similar data from 1980, and analyzed for factors expected to influence the use of regional anesthesia during training. RESULTS: The use of regional anesthesia in residency training programs has increased from 21.3% in 1980 to 29.8% in 1990, primarily because of a two-fold rise in the use of epidural anesthesia. The use of regional anesthesia is strongly correlated with a resident's exposure to obstetric anesthesia and pain consultations. Wide variability between residency programs remains. CONCLUSION: Some training programs continue to fail to provide adequate regional anesthesia exposure to train residents fully in these techniques, despite the overall increased use of regional anesthesia.

Effect of epinephrine on lidocaine clearance in vivo: a microdialysis study in humans.

BACKGROUND: Local anesthetic nerve block prolonged by epinephrine is thought to result from local vasoconstriction and consequent decreased local anesthetic clearance from the injection site. However, no study has yet confirmed this directly in humans by measuring tissue concentrations of local anesthetic over time. In addition, recent studies have shown that the alpha2-adrenergic receptor agonist, clonidine, also prolongs nerve block without altering local anesthetic clearance. Because epinephrine is also an alpha2-adrenergic receptor agonist, it is possible that epinephrine prolongs local anesthetic block by a pharmacodynamic mechanism and not a pharmacokinetic one. This study was designed to address this issue. METHODS: Microdialysis probes were placed adjacent to the superficial peroneal nerve in both feet of eight volunteers. Plain lidocaine (1%) was injected along one peroneal nerve and lidocaine with epinephrine (2.5 microg/ml) was injected along the other nerve in a double-blinded, randomized manner. The concentration of lidocaine in tissue was measured at 5-min intervals, and sensory block and cutaneous blood flow were assessed by laser Doppler at 10-min intervals for 5 h. The resulting data for lidocaine concentration versus time were fit to a two-compartment model using modeling software. RESULTS: Epinephrine prolonged sensory block by decreasing local blood flow and slowing clearance. There was no evidence of a pharmacodynamic effect of epinephrine. CONCLUSION: Although epinephrine activates alpha2-adrenergic receptors, its mechanism for prolonging the duration of local anesthetic block rests on its ability to decrease local anesthetic clearance and not on a pharmacodynamically mediated potentiation of local anesthetic effect.

Effect of ropivacaine on cutaneous capillary blood flow in pigs.

The effect of subcutaneous infiltration of ropivacaine and bupivacaine on local cutaneous blood flow was assessed by the laser Doppler method. One milliliter of each of ten test solutions (ropivacaine 0.25% and 0.75%, bupivacaine 0.25% and 0.75%, and saline, each with and without added epinephrine 5 micrograms/ml) was injected subcutaneously at separate sites on the side of each pig (n = 6). Skin blood flow was measured by laser Doppler at all sites before and 5, 10, 15, and 30 min after injection. Subcutaneous injection of ropivacaine 0.25% or 0.75% decreased cutaneous blood flow by a maximum of 52% +/- 11% and 54% +/- 14% (mean +/- SE), respectively. In contrast, bupivacaine 0.25% or 0.75% increased flow by 90% +/- 32% and 82% +/- 48%, and injection of saline increased blood flow by 32% +/- 17%. Cutaneous blood flow after the injection of ropivacaine was significantly lower than after injection of bupivacaine or saline, and was also lower than at the uninjected control site (P = 0.0009). All of the solutions with epinephrine decreased blood flow to a similar extent (48-73%, P = 0.3). The ability of ropivacaine to produce cutaneous vasoconstriction offers several advantages over the other local anesthetics presently available for infiltration anesthesia.

Accuracy of laser Doppler capillary flow measurements for predicting blood loss from skin incisions in pigs.

This study assesses the clinical applicability of laser Doppler capillary flow measurements for predicting blood loss from a surgical incision. To produce a wide range of blood flows, we injected lidocaine 1%, lidocaine 1% plus octapressin (0.03 IU.ml-1), and lidocaine 1% plus epinephrine (5 micrograms.ml-1) subcutaneously into three separate sites on the flank of each animal (N = 6). Laser Doppler flow measurements were made before and 10 minutes after injection Subcutaneous injection of lidocaine tended to increase cutaneous blood flow (96 +/- 13 to 153 +/- 30 mV, mean +/- SE, P = 0.09). Blood flow tended to decrease after injection of lidocaine with epinephrine (101 +/- 13 to 57 +/- 10 mV, P = 0.03) or octapressin (108 +/- 20 to 58 +/- 11 mV, P = 0.08). Laser Doppler measurements were higher after the injection of plain lidocaine than after that of lidocaine with either epinephrine or octapressin (P = 0.004). A standard incision was performed at each site and blood loss measured over the subsequent 10 minutes. Laser Doppler measurements correlated with the amount of bleeding from the surgical incision (R = 0.69, P less than 0.001). We conclude that the laser Doppler is a useful tool for evaluating the ability of subcutaneously injected local anesthetics (vasodilators) or vasoconstrictors to alter bleeding from skin incisions.

Effect of needle puncture on morphine and lidocaine flux through the spinal meninges of the monkey in vitro. Implications for combined spinal-epidural anesthesia.

BACKGROUND: Combined spinal-epidural anesthesia is a technique growing in popularity. However, there have been no attempts to investigate the risk of epidural drug reaching the subarachnoid space in high concentration by passing through the meningeal hole left by the spinal needle. This study begins to address this question by quantitating the flux of morphine and lidocaine through the spinal meninges of the monkey in vitro after puncture with three different-sized needles. METHODS: Spinal meningeal tissue from anesthetized monkeys was mounted in a diffusion cell and drug flux was measured through intact tissue and through tissue punctured with a 27-G Whitacre, a 24-G Sprotte, and an 18-G Tuohy needle. RESULTS: The flux of morphine through the meningeal tissue was significantly increased by puncture with each of the study needles. The flux of lidocaine was significantly increased only by puncture with the 24-G Sprotte and 18-G Tuohy needles. The flux of morphine through intact tissue was less than the flux of lidocaine through intact tissue. In contrast, the flux of morphine and lidocaine were the same through tissue punctured with the study needles. The magnitude of the drug flux through the needle puncture was a function of the diameter of the study needle. CONCLUSIONS: Epidural anesthesia after accidental or intentional puncture of the spinal meninges has occasionally resulted in high spinal blocks and total spinal anesthesia. This study suggests that drug movement through the meningeal hole is responsible for this complication and that the risk may be decreased by using the smallest possible needle to puncture the meninges.

The reliability of epidural anesthesia for repeat ESWL: a study of changes in epidural compliance.

Changes in epidural compliance were investigated before and after extracorporeal shock wave lithotripsy (ESWL) in 11 outpatients. Epidural pressures were unchanged acutely by ESWL (p greater than 0.15). In contrast to previous reports of failures of epidural anesthesia in patients having repeat ESWL treatments, a review of our population of patients having repeat ESWL indicates that epidural anesthesia is reliable and not associated with any greater failure rate than for initial ESWL treatments. The difference between our results and previous reports of high failure rates is likely due to differences in anesthetic and surgical techniques such as: (1) use of air for loss-of-resistance when locating the epidural space, (2) differences in the time interval between ESWL treatments, and (3) frequency of use of epidural catheters.

Comparison of lidocaine and saline for epidural top-up during combined spinal-epidural anesthesia in volunteers.

This study was designed to determine the efficacy of saline as an epidural top-up to prolong spinal anesthesia during combined spinal-epidural anesthesia (CSEA). Eight volunteers received three separate CSEAs with intrathecal lidocaine (50 mg). After two-segment regression, each subject received either a saline (10 mL), lidocaine 1.5% (10 mL), or control sham (0.5 mL saline) epidural injection in a randomized, double-blind, triple cross-over fashion. Sensory block was assessed by pinprick and tolerance to transcutaneous electrical stimulation (TES) equivalent to surgical stimulation at the knee and ankle. Motor strength was assessed with iso-metric force dynamometry. Data were analyzed with a repeated measures analysis of variance and a paired t-test. Sensory block to pinprick was prolonged in the thoracolumbar dermatomes only by lidocaine (P < 0.05). Neither lidocaine nor saline prolonged the duration of tolerance to TES at the tested sites. Instead, saline decreased the duration of tolerance to TES by 20 and 24 min at the knee and ankle (P < 0.05). Recovery from motor block at the quadriceps was prolonged by an epidural injection of lidocaine (P < 0.05). We conclude that when 10 mL of epidural saline is administered after two-segment regression, it is an ineffective top-up and may decrease the duration of spinal anesthesia during CSEA.

A comparison of epidural levobupivacaine 0.75% with racemic bupivacaine for lower abdominal surgery.

UNLABELLED: Levobupivacaine, the S(-) isomer of bupivacaine, is less cardiotoxic than racemic bupivacaine. In this prospective, randomized, double-blinded study of epidural anesthesia, the onset, extent, and duration of sensory and motor block produced by 0.75% levobupivacaine (20 mL, 150 mg) was compared with that of 0.75% racemic bupivacaine in 56 patients undergoing elective lower abdominal surgery. The time to onset of adequate sensory block (T10 dermatome) was similar in both treatment groups (13.6 +/- 5.6 min for levobupivacaine and 14.0 +/- 9.9 min for bupivacaine), with an average peak block height of T5 reached at 24.3 +/- 9.4 and 26.5 +/- 13.2 min, respectively. Time to complete regression of sensory block was significantly longer with levobupivacaine (550.6 +/- 87.6 min) than bupivacaine (505.9 +/- 71.1 min) (P = 0.016). Abdominal muscle relaxation was adequate for the scheduled procedure in all patients, and there were no significant differences between the groups in rectus abdominis muscle scores (P = 0.386) and quality of muscle relaxation as determined by the surgeon and anesthesiologist (P = 0. 505 and 0.074, respectively). In conclusion, both 0.75% levobupivacaine and 0.75% bupivacaine produced effective epidural anesthesia and their effects were clinically indistinguishable. IMPLICATIONS: The results of this study indicate that the sensory and motor block produced by 0.75% levobupivacaine is equivalent to that of 0.75% racemic bupivacaine. Both local anesthetics are well tolerated and effective in producing epidural anesthesia for patients undergoing lower abdominal surgery.

Quantitative assessment of differential sensory nerve block after lidocaine spinal anesthesia.

BACKGROUND: Recent technology allows for quantitative and selective measurement of A beta, A delta, and C fiber nerve transmission. To gain further insight into the physiology of differential block after lidocaine spinal anesthesia, the function of these different fibers was quantitatively measured over time, and these measurements were correlated with regression of anesthesia to pinprick, touch, cold, and tolerance of tetanic electrical current (equivalent to surgical incision). METHODS: Six volunteers received lidocaine spinal anesthesia with 50 mg lidocaine (5% in dextrose). Cutaneous current perception thresholds at 2,000, 250, and 5 Hz, which stimulate A beta, A delta, and C fibers, respectively, were determined at L2-L3 (medial aspect above knee) before and every 10 min after spinal anesthesia. Dermatomal levels to pinprick, touch, and cold were assessed every 5 min after spinal anesthesia. Tolerance to tetanic electrical stimulus was assessed at L2-L3 every 10 min after spinal anesthesia. RESULTS: Differential block was demonstrated by the sequential return of sensation to touch, pinprick, and cold at L2-L3. Recovery of function of A beta, A delta, and C fibers correlated with return of sensation to touch (R2 = 0.7, p = 0.03), pinprick (R2 = 0.75, p = 0.02), and cold (R2 = 0.67, p = 0.04) respectively. Loss of tolerance of surgical anesthesia corresponded to return of A beta current perception thresholds to baseline, whereas current perception thresholds for A delta and C fibers were still increased to greater than baseline (p = 0.025). CONCLUSIONS: Differential sensory block during spinal anesthesia is due to different recovery profiles of A beta, A delta, and C fibers. Return of A beta current perception thresholds to baseline correlated with duration of surgical anesthesia as assessed with an electrical stimulation model.

The regional anesthesia "learning curve". What is the minimum number of epidural and spinal blocks to reach consistency?

BACKGROUND AND OBJECTIVES: Wide variability exists in the amount of regional anesthesia practice to which residents are exposed during training. The number of attempts at various blocks before a trainee becomes proficient at performing these regional anesthetic techniques is not known. This study addresses the question: What is the minimum number of blocks a resident must perform to reach consistency during training in these techniques? METHODS: Every regional anesthetic technique attempted by all beginning CA-1 anesthesiology residents (n = 7) during their first 6 months of training (July 1993 to December 1993) were recorded on a daily basis. Nonregional anesthetic techniques attempted were recorded for comparison. The objective measures used to define the degree of success were obtaining cerebrospinal fluid during attempted spinal anesthesia, subsequent anesthetic block during epidural placement, and detection of end-tidal carbon dioxide for endotracheal intubation. RESULTS: An average of 77 +/- 9 epidural anesthetics, 44 +/- 6 spinal anesthetics, and 86 +/- 13 endotracheal intubations were attempted during the 6 months of training. The learning curves for each technique are of similar shape. Residents show significant (P < .05) improvement over baseline after 20 spinal and 25 epidural anesthetics, but a 90% success rate is not reached and maintained until 45 spinal and 60 epidural anesthetics are performed. CONCLUSIONS: Approximately 20-25 procedures each are necessary before improvement in the techniques of spinal and epidural anesthesia is demonstrated by residents in training. If a 90% success rate is desired, 45 and 60 attempts at spinal and epidural anesthesia, respectively, may be necessary.

A comparison of levobupivacaine 0.125%, fentanyl 4 microg/mL, or their combination for patient-controlled epidural analgesia after major orthopedic surgery.

UNLABELLED: Levobupivacaine, the isolated S(-) isomer of bupivacaine, is less cardiotoxic than racemic bupivacaine in animal studies. We studied the effectiveness of patient-controlled epidural analgesia (PCEA) with either levobupivacaine 0.125% or fentanyl 4 microg/mL alone, or a combination of levobupivacaine and fentanyl in 65 patients after total joint arthroplasty in a prospective, random, double-blinded fashion. Intraoperatively, all patients received 20 mL of 0.75% levobupivacaine. Study medication was infused at an initial rate of 4 mL/h, with additional medication available on patient demand (2 mL/10 min). The combination of levobupivacaine and fentanyl produced better analgesia (longer time to first PCEA request; P = 0.007 combination versus fentanyl and P = 0.006 combination versus levobupivacaine) than either drug alone. Patients in the levobupivacaine groups had appreciable sensory blockade to pinprick with minimal motor impairment. Resting and dynamic visual analog scale pain scores were lower in the combination group than in the plain fentanyl group at 6 (P = 0.022 and 0.036) and 12 h (P = 0.002 and 0.001). The 24-h overall patient- and investigator-rated visual analog scale pain scores were also lower in the combination group (resting P = 0.007, dynamic P = 0.005). There was no significant difference among the groups in the incidence of postoperative nausea (26.2%), pruritus (9.2%), hypotension (23.1%), or sedation (0%). We conclude that the analgesic effects of levobupivacaine 0.125% and fentanyl (4 microg/mL) are additive and beneficial for the management of orthopedic surgical pain by the PCEA method. Patients in this study began demand-dosing later, reported lower pain scores, and had no greater risk of adverse events than those who were given either levobupivacaine or fentanyl alone. IMPLICATIONS: We demonstrated a significant additive effect of the combination of levobupivacaine (0.125%) and fentanyl (4 microg/mL), compared with either drug alone, when using patient-controlled epidural analgesia in patients after total joint arthroplasty.

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.