ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20‐ml volume for epidural analgesia in the first stage of labor. The aim of this study was to assess the relative analgesic potencies of epidural bupivacaine and ropivacaine by determining their respective minimum local analgesic concentrations.MethodsSeventy‐three parturients at <or= to 7 cm cervical dilation who requested epidural analgesia were allocated to one of two groups in this double‐blinded, randomized, prospective study. After a lumbar epidural catheter was placed, 20 ml of the test solution was given, either ropivacaine (n = 34) or bupivacaine (n = 39). The concentration of local anesthetic was determined by the response of the previous patient in that group to a higher or lower concentration using up‐down sequential allocation. Analgesic efficacy was assessed using 100‐mm visual analog pain scores with <or= to 10 mm within 30 min defined as effective. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment.ResultsThe minimum local analgesic concentration of ropivacaine was 0.111% wt/vol (95% confidence interval, 0.100‐0.122), and the minimum local analgesic concentration of bupivacaine was 0.067% wt/vol (95% confidence interval, 0.052‐0.082). Ropivacaine was significantly less potent than bupivacaine, with a potency ratio of 0.6 (95% confidence interval, 0.49‐0.74). No difference in motor effects was observed.ConclusionRopivacaine was significantly less potent than bupivacaine for epidural analgesia in the first stage of labor.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundParalysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle.MethodsElectromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium.ResultsThe maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P <or= to 0.05). Onset time was not different between the larynx (58 +/− 10 s), the diaphragm (57 +/− 8 s), and the adductor pollicis (54 +/− 13 s), after succinylcholine (all mean +/− SD). After rocuronium, onset time was 124 +/− 39 s at the larynx, 130 +/− 44 s at the diaphragm, and 115 +/− 21 s at the adductor pollicis. After succinylcholine administration, time to 90% recovery was 8.3 +/− 3.2, 7.2 +/− 3.5, and 9.1 +/− 3.0 min at the larynx, the diaphragm, and the adductor pollicis, respectively. Time to 90% recovery after rocuronium administration was 34.9 +/− 7.6, 30.4 +/− 49.1 +/− 11.4 min at the larynx, the diaphragm, and the adductor pollicis, respectively.ConclusionNeuromuscular blocking effect of muscle relaxants on the larynx can be measured noninvasively by electromyography. Although the larynx appears to be resistant to muscle relaxants, we could not demonstrate that its onset time differed from that of peripheral muscles.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundBecause adenosine has been alleged to produce both anesthetic and analgesic sparing effects, a randomized, double‐blinded study was designed to compare the perioperative effects of adenosine and remifentanil when administered as intravenous adjuvants during general anesthesia for major gynecologic procedures.MethodsThirty‐two women were assigned randomly to one of two drug treatment groups. After premedication with 0.04 mg/kg intravenous midazolam, anesthesia was induced with 2 [micro sign]g/kg intravenous fentanyl, 1.5 mg/kg intravenous propofol, and 0.6 mg/kg intravenous rocuronium, and maintained with desflurane, 2%, and nitrous oxide, 65%, in oxygen. Before skin incision, an infusion of either remifentanil (0.02 [micro sign]g [middle dot] kg‐1[middle dot] min‐1) or adenosine (25 [micro sign]g [middle dot] kg‐1[middle dot] min‐1) was started and subsequently titrated to maintain systolic blood pressure, heart rate, or both within 10‐15% of the preincision values.ResultsAdenosine and remifentanil infusions were effective anesthetic adjuvants during lower abdominal surgery. Use of adenosine (mean +/− SEM, 166 +/− 17 [micro sign]g [middle dot] kg‐1[middle dot] min‐1) was associated with a significantly greater decrease in systolic blood pressure and higher heart rate values compared with remifentanil (mean +/− SEM, 0.2 +/− 0.03 [micro sign]g [middle dot] kg‐1[middle dot] min‐1). Total postoperative opioid analgesic use was 45% and 27% lower in the adenosine group at 0‐2 h and 2‐24 h after surgery, respectively.ConclusionsAdjunctive use of a variable‐rate infusion of adenosine during desflurane‐nitrous oxide anesthesia was associated with acceptable hemodynamic stability during the intraoperative period. Compared with remifentanil, intraoperative use of adenosine was associated with a decreased requirement for opioid analgesics during the first 24 h after operation.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe distribution of solutions injected into the epidural space has not been determined. The author therefore examined the site of catheter tips and the spread of contrast material in the epidural space using computed tomographic (CT) imaging in patients receiving successful epidural analgesia.MethodsLumbar epidural catheters were placed in 20 female patients by a midline technique. Anesthetic effect was determined by motor and sensory examinations during analgesic infusion. CT images were obtained for identification of the catheter tip and after radiographic contrast injection of 4 ml and then an additional 10 ml.ResultsCatheter tips were most often found lateral to the dura in the intervertebral foramen. In these subjects with normally functioning epidural analgesia, there was remarkable interindividual variability in patterns of spread, including various amounts of anterior passage, layering along the dura, and compression of the dura creating a posterior fold. Accumulation becomes more symmetric with increasing injectate volume. Spread through the intervertebral foramina was seen in all subjects. Air and fat in the region of the catheter interfered with solution spread in three subjects, but only over a limited area. Asymmetry in anesthetic effect was attributable to catheter position. No substantial barriers to solution spread were observed.ConclusionsA variety of catheter tip positions and patterns of solution spread underlie normal epidural anesthesia. Non‐uniform distribution of injectate is common and is compatible with uniform anesthesia. Posterior midline structures play a minimal role in impeding distribution of injectate. A far lateral catheter position is a more common cause of asymmetric block than anatomic barriers to solution spread.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundRopivacaine 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.MethodsEighteen 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.ResultsRopivacaine and bupivacaine provided dose‐dependent prolongation of sensory and motor block and time until achievement of discharge criteria (R2ranges 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.ConclusionRopivacaine 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.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThe purpose of this study was to determine current practice patterns for preoperative fasting at major pediatric hospitals.MethodsFasting guidelines for children at each of the hospitals listed in the second edition of the Directory of Pediatric Anesthesiology Fellowship Programs were solicited and analyzed.ResultsFifty‐one institutions were surveyed, and 44 responded. In 50%, clear fluids were permitted up to 2 h prior to anesthesia for all children. Breast milk was restricted to 4 h for children younger than 6 months in 61% of hospitals. Institutions were equally divided (39% each) between a 4‐h and 6‐h fast for formula in infants younger than 6 months; for infants older than 6 months, 50% of hospitals restricted formula feeding to 6 h. There was no consensus for solid feeding in children younger than 3 yr, but 50% of hospitals agree that solids should be restricted after midnight in children older than 3 yr.ConclusionsThere is no uniform fasting practice for children before elective surgery in the United States and Canada. However, there is agreement among most institutions that ingestion of clear fluids 2‐3 h prior to general anesthesia is acceptable. Most also accept a 4‐h restriction for breast milk and a 6‐h restriction for nonhuman formula. There is great diversity among institutions regarding fasting for solids in children, with many restricting intake after midnight. There is little agreement about whether infant formula should be treated in the same way as solid food or how to categorize breast milk.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundThrombogenesis in total hip replacement (THR) begins during surgery on the femur. This study assesses the effect of two doses of unfractionated intravenous heparin administered before femoral preparation during THR on circulating markers of thrombosis.MethodsSeventy‐five patients undergoing hybrid primary THR were randomly assigned to receive blinded intravenous injection of either saline or 10 or 20 U/kg of unfractionated heparin after insertion of the acetabular component. Central venous blood samples were assayed for prothrombin F1+2 (F1+2), thrombin‐antithrombin complexes (TAT), fibrinopeptide A (FPA), and D‐dimer.ResultsNo changes in the markers of thrombosis were noted after insertion of the acetabular component. During surgery on the femur, significant increases in all markers were noted in the saline group (P < 0.0001). Heparin did not affect D‐dimer or TAT. Twenty units per kilogram of heparin significantly reduced the increase of F1+2 after relocation of the hip joint (P < 0.001). Administration of both 10 and 20 U/kg significantly reduced the increase in FPA during implantation of the femoral component (P < 0.0001). A fourfold increase in FPA was noted in 6 of 25 patients receiving 10 U/kg of heparin but in none receiving 20 U/kg (P = 0.03). Intraoperative heparin did not affect intra‐ or postoperative blood loss, postoperative hematocrit, or surgeon's subjective assessments of bleeding. No bleeding complications were noted.ConclusionsThis study demonstrates that 20 U/kg of heparin administered before surgery on the femur suppresses fibrin formation during primary THR. This finding provides the pathophysiologic basis for the clinical use of intraoperative heparin during THR.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

BackgroundPrilocaine exists in two stereoisomeric configurations, the enantiomers s(+)‐ and R(‐)‐prilocaine. The drug is clinically used as the racemate. This study examined the pharmacokinetics of the enantiomers after intravenous administration of the racemate.MethodsTen healthy male volunteers received 200 mg racemic prilocaine as a 10‐min intravenous infusion. Blood samples were collected for 8 h after the start of the infusion. Plasma concentrations were measured by stereoselective high‐performance liquid chromatography (HPLC). Unbound fractions of the enantiomers in blank blood samples, spiked with racemic prilocaine, were determined using equilibrium dialysis.ResultsThe unbound fraction of R(‐)‐prilocaine (mean +/− SD, 70% +/− 8%) was smaller (P < 0.05) than that of S(+)‐prilocaine (73% +/− 5%). The total plasma clearance of R(‐)‐prilocaine (2.57 +/− 0.46 l/min) was larger (P < 0.0001) than that of S(+)‐prilocaine (1.91 +/− 0.30 l/min). The steady‐state volume of distribution of R(‐)‐prilocaine (279 +/− 94 l) did not differ from that of S(+)‐prilocaine (291 +/− 93 l). The terminal half‐life of R(‐)‐prilocaine (87 +/− 27 min) was shorter (P < 0.05) than that of S(+)‐prilocaine (124 +/− 64 min), as was the mean residence time of R(‐)‐prilocaine (108 +/− 30 min) compared with S(+)‐prilocaine (155 +/− 59 min; P < 0.005).ConclusionsThe pharmacokinetics of prilocaine are enantio‐selective. The difference in clearance is most likely a result of a difference in intrinsic metabolic clearance. The difference in the pharmacokinetics of the enantiomers of prilocaine does not seem to be clinically relevant.

ISSN:0003-3022    

出版商:OVID    

年代:1999

数据来源: OVID