Locoregional versus general anesthesia in carotid surgery: is there an impact on perioperative myocardial ischemia? Results of a prospective monocentric randomized trial. (25/1144)

PURPOSE: The incidence of cardiac morbidity and mortality in patients who undergo carotid surgery ranges from 0.7% to 7.1%, but it still represents almost 50% of all perioperative complications. Because no data are available in literature about the impact of the anesthetic technique on such complications, a prospective randomized monocentric study was undertaken to evaluate the role of local anesthesia (LA) and general anesthesia (GA) on cardiac outcome. METHODS: From November 1995 to February 1998, 107 patients were classified by the cardiologist as cardiac patients (IHD; history of myocardial infarction, previous myocardial revascularization procedures, or myocardial ischemia documented by means of positive electrocardiogram [ECG] stress test results) or noncardiac patients (NIHD; no history of chest pain or negative results for an ECG stress test). The patients were operated on after the randomization for the type of anesthesia (general or local). Continuous computerized 12-lead ECG was performed during the operative procedure and 24 hours postoperatively. The end points of the study were ECG modifications (upsloping or downsloping more than 2 mm) of the sinus tachycardia (ST) segment. RESULTS: Fifty-five patients were classified as IHD, and 52 were classified as NIHD. Twenty-seven of the 55 IHD patients (49%) and 24 of 52 NIHD patients (46%) were operated on under GA. Thirty-six episodes of myocardial ischemia occurred in 22 patients (20.5%). Episodes were slightly more frequent (58%) and longer in the postoperative period (intraoperative, 10 +/- 5 min; postoperative, 60 +/- 45 min; P <. 001). As expected, the prevalence of myocardial ischemia was higher in the group of cardiac patients than in noncardiac group (15 of 55 patients [27%] vs 7 of 52 patients [13%]; P <.02). By comparing the two anesthetic techniques in the overall population, we found a similar prevalence of patients who had myocardial ischemia (GA, 12 of 52 [23%]; LA, 10 of 55 [18%]; P = not significant) and a similar number of ischemic episodes per patient (GA, 1.5 +/- 0.4; LA, 1.8 +/- 0.6; P = not significant). Episodes of myocardial ischemia were similarly distributed in intraoperative and postoperative periods in both groups. It is relevant that under GA, IHD patients represent most of the population who suffered myocardial ischemia (83%). On the contrary, in the group of patients operated on under LA, the prevalence was equally distributed in the two subpopulations. CONCLUSION: The results confirm the different hemodynamic impact of the two anesthetic techniques. Patients who received LA had a rate of myocardial ischemia that was half that of patients who had GA. The small number of cardiac complications do not permit us to make any definitive conclusion on the impact of the two anesthetic techniques on early cardiac morbidity, but the relationship between perioperative ischemic burden and major cardiac events suggests that LA can be used safely, even in high-risk patients undergoing carotid endarterectomy.  (+info)

Point mutations at N434 in D1-S6 of mu1 Na(+) channels modulate binding affinity and stereoselectivity of local anesthetic enantiomers. (26/1144)

Voltage-gated Na(+) channels are the primary targets of local anesthetics (LAs). Amino acid residues in domain 4, transmembrane segment 6 (D4-S6) form part of the LA binding site. LAs inhibit binding of the neurotoxin batrachotoxin (BTX). Parts of the BTX binding site are located in D1-S6 and D4-S6. The affinity of BTX-resistant Na(+) channels mutated in D1-S6 (mu1-N434K, mu1-N437K) toward several LAs is significantly decreased. We have studied how residue mu1-N434 influences LA binding. By using site-directed mutagenesis, we created mutations at mu1-N434 that vary the hydrophobicity, aromaticity, polarity, and charge and investigated their influence on state-dependent binding and stereoselectivity of bupivacaine. Wild-type and mutant channels were transiently expressed in human embryonic kidney 293t cells and investigated under whole-cell voltage-clamp. For resting channels, bupivacaine enantiomers showed a higher potency in all mutant channels compared with wild-type channels. These changes were not well correlated with the physical properties of the substituted residues. Stereoselectivity was small and almost unchanged. In inactivated channels, the potency of bupivacaine was increased in mutations containing a quadrupole of an aromatic group (mu1-N434F, mu1-N434W, mu1-N434Y), a polar group (mu1-N434C), or a negative charge (mu1-N434D) and was decreased in a mutation containing a positive charge (mu1-N434K). In mutation mu1-N434R, containing the positively charged arginine, the potency of S(-)-bupivacaine was selectively decreased, resulting in a stereoselectivity (stereopotency ratio) of 3. Similar results were observed with cocaine but not with RAC 109 enantiomers. We propose that in inactivated channels, residue mu1-N434 interacts directly with the positively charged moiety of LAs and that D1-S6 and D4-S6 form a domain-interface site for binding of BTX and LAs in close proximity.  (+info)

Bupivacaine augments intrathecal fentanyl for labor analgesia. (27/1144)

BACKGROUND: fentanyl has been shown to be an effective analgesic for labor; this study investigated the analgesic effect of low-dose bpivacaine added to intrathecal fentanyl for labor analgesia METHODS: Ninety parturients in active labor who requested regional analgesia were randomized to receive an intrathecal injection of either fentanyl, 25 microg; bupivacaine, 1.25 mg, with fentanyl, 25 microg; or bupivacaine, 2.5 mg, with fentanyl, 25 microg, as part of a combined spinal-epidural technique. Visual analog pain scores were recorded before and at intervals after injection until the patient requested further analgesia. Maternal blood pressure and fetal heart rate were recorded before and at intervals after injection. Lower-extremity muscle strength was tested before and 30 min after injection; anesthetic level to cold sensation and the presence and severity of pruritus were recorded. RESULTS: Duration of analgesia was longer in the group receiving bupivacaine, 2.5 mg, and fentanyl, 25 microg, than the group receiving plain fentanyl (108 vs. 92 min; P < 0.05). Onset of analgesia was faster in both groups receiving bupivacaine compared with plain fentanyl (P < 0.05). No differences in muscle strength after injection were found in any group, although anesthetic levels to cold were documented in all patients in the bupivacaine groups, and 21 of 30 in the plain fentanyl group. Baseline fetal heart rates did not change after injection in any group, and maternal blood pressure was unchanged. CONCLUSIONS: The addition of 2.5 mg isobaric bupivacaine to 25 microg fentanyl for intrathecal labor analgesia modestly increases duration and speeds onset of analgesia compared with plain intrathecal fentanyl.  (+info)

Relative potencies of bupivacaine and ropivacaine for analgesia in labour. (28/1144)

We have used the technique of randomized, double-blind sequential allocation to compare the minimum local analgesic concentrations (MLAC) of epidural bupivacaine and ropivacaine for women in the first stage of labour. The test bolus was 20 ml of local anaesthetic solution. The concentration was determined by the response of the previous woman to a higher or lower concentration of local anaesthetic, according to up-down sequential allocation. Efficacy was assessed using a 100-mm visual analogue pain score (VAPS). The test solution had to achieve a VAPS of 10 mm or less to be judged effective. For bupivacaine, MLAC was 0.093 (95% CI 0.076-0.110)% w/v, and for ropivacaine, 0.156 (95% CI 0.136-0.176)%w/v (P < 0.0001, 95% CI difference 0.036-0.090). The analgesic potency of ropivacaine was 0.60 (0.47-0.75) relative to bupivacaine. Claims for reduced toxicity and motor block must be considered with differences in analgesic potency in mind.  (+info)

Patients' vs nurses' assessments of postoperative pain and anxiety during patient- or nurse-controlled analgesia. (29/1144)

We have compared patients' and nurses' assessments of postoperative pain and anxiety after different analgesic treatments. Sixty orthopaedic patients were allocated randomly to receive i.v. piritramide (either nurse-controlled or patient-controlled) or subarachnoid bupivacaine (nurse-controlled or patient-controlled). Patients and nurses assessed pain and anxiety using a visual analogue scale (VAS; 1-100 mm). Pain and anxiety ratings of patients and nurses were significantly correlated (Spearman's r > or = 0.69; P < 0.001). In general, patients' pain scores were higher than nurses' scores (patients' median VAS = 34 (range 1-76) mm; nurses VAS 21 (1-59) mm) and for all groups except the patient-controlled subarachnoid bupivacaine group, where they were significantly higher (P < 0.01). Discrepancy in pain estimates between patients and nurses increased with the level of pain. The relationship between patients' and nurses' anxiety scores was less clearly defined and did not depend on the level of anxiety.  (+info)

Effect of bupivacaine on ATP-dependent potassium channels in rat cardiomyocytes. (30/1144)

Bupivacaine induces fatal arrhythmia when accidentally injected i.v. or overdosed, whereas lidocaine is used as an anti-arrhythmic agent. We have suggested recently that the anti-arrhythmic effect of lidocaine may be explained by suppression of ATP-sensitive potassium (KATP) channels. Therefore, it could be argued that different sensitivities of KATP channels to both drugs could be a reason for their different arrhythmic and anti-arrhythmic properties. In this study, we have investigated the direct action of bupivacaine on KATP channels in cardiomyocytes. The effects of bupivacaine on the cardiac KATP channel were investigated using the patch-clamp technique on enzymatically dissociated cardiomyocytes of adult rats. Bupivacaine was applied to the outer side of excised membrane patches using a multiple-barrel perfusion system. Concentration-response curves indicated that bupivacaine blocked the mean current of the KATP channels at a half-maximum inhibiting concentration (IC50) of 29 mumol litre-1, similar to that reported for lidocaine (43 mumol litre-1). Binding of bupivacaine influenced the gating of this channel, but did not reduce the conductance of the open channel. Bupivacaine and lidocaine were equipotent in blocking KATP channels. However, because of its excessive block of the sodium channel in the inactivated state, block of KATP channels by bupivacaine will only enhance its cardiotoxicity.  (+info)

Regeneration of new fibers in muscles of old rats reduces contraction-induced injury. (31/1144)

Skeletal muscles are injured by their own contractions. Compared with muscles in young animals, those in old animals are injured more easily and more severely and regenerate less well afterward. Injection of a myotoxin (bupivacaine) causes complete degeneration of fibers in extensor digitorum longus (EDL) muscles of rats, followed by full regeneration within 60 days. We tested the specific hypothesis that, 3 days after a protocol of pliometric (lengthening) contractions, the newly regenerated muscle fibers in bupivacaine-treated EDL muscles in both young and old rats would show a lesser deficit in maximum force and fewer damaged fibers than muscles in nontreated EDL muscles. The treated and nontreated EDL muscles of young and old male Wistar rats were administered a protocol of 225 pliometric contractions and were evaluated 3 days afterward, when morphological damage to muscle fibers is most severe. In treated compared with nontreated EDL muscles of both young and old rats, the force deficit and the number of damaged fibers were each reduced by approximately 75%. We conclude that newly regenerated fibers in muscles of young and old animals are resistant to injury and that maintenance of newly regenerated fibers by conditioning may prevent inadvertent damage, particularly in muscles of elderly people.  (+info)

Randomized, controlled trial of bupivacaine injection to decrease pain after laparoscopic cholecystectomy. (32/1144)

OBJECTIVES: To determine if intraoperative instillation of bupivacaine would decrease early postoperative pain after laparoscopic cholecystectomy, if the patients would consequently require less narcotic postoperatively and if such patients would elect to be discharged on the day of operation if given the choice. DESIGN: Double-blind, randomized, controlled trial. SETTING: A tertiary care hospital in Hamilton, Ont. PATIENTS: Fifty patients underwent laparoscopic cholecystectomy. Day-surgery patients had the choice of staying overnight for discharge the following day. They were compared with a control group of 47 patients who had laparoscopic cholecystectomy but did not receive bupivacaine. INTERVENTION: Instillation of 20 mL of 0.5% bupivacaine with epinephrine into laparoscopic cholecystectomy port sites intraoperatively before closure. MAIN OUTCOME MEASURES: Visual analogue scale (VAS) pain scores assessed 4 times postoperatively, the choice of patients to leave hospital the same day or to remain in the hospital overnight; the level of postoperative narcotic usage. MAIN RESULTS: Mean VAS pain scores (range 0 [no pain] to 5 [severe pain]) at less than 2 hours and at 6 hours after surgery were 2.9 and 2.9, respectively, in the bupivacaine group compared with 4.5 and 4.0, respectively, in the control group (p = 0.001 and 0.025). VAS scores at 10 hours postoperatively and the next morning did not differ between the groups. More patients in the bupivacaine group elected to go home on the day of surgery (p = 0.034). Narcotic usage was not significantly different. CONCLUSION: Instillation of bupivacaine into port sites should be standard practice for elective laparoscopic cholecystectomy.  (+info)