A Comparison of the Local Anesthetic Effects of Meperidine, Fentanyl, and Sufentanil on Dorsal Root Axons

Comparative Evaluation of the Local Anesthetic Action of Tramadol Hydrochloride With Adrenaline Versus Lidocaine Hydrochloride With Adrenaline for Maxillary Exodontia: A Randomized Control Trial

BACKGROUND

Tramadol hydrochloride (T-HCl) has demonstrated to have a local anesthetic effect similar to lidocaine hydrochloride (L-HCl) when administered locally for minor oral surgical procedures.

PURPOSE

Our study aimed to compare the anesthetic effect of T-HCl versus L-HCl in maxillary premolar extraction.

STUDY DESIGN, SETTING AND SAMPLE

The study is a split-mouth, double-blind randomized clinical trial at the Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bengaluru, India. The study sample was composed of patients referred for maxillary bicuspid extraction. Patients were excluded from the sample if, allergic to the study drugs, pregnant or lactating females, and smokers.

EXPOSURE VARIABLE

The variable is an anesthetic drug administered for local anesthesia and it is grouped into 2 categories, T-HCl and L-HCl. A supraperiosteal infiltration of T-HCl with adrenaline on one side and L-HCl with adrenaline on the contralateral side was injected.

MAIN OUTCOME VARIABLE

The primary outcome variable was profound anesthesia of T-HCl, where the patient sensed the loss of sensation of touch, temperature, and pain. Secondary outcomes were onset and duration of anesthesia, intraoperative pain, postoperative analgesia, and adverse reactions, were recorded.

ANALYSES

Inferential statistics, the χ2 Test, the Mann-Whitney Test, and the Wilcoxon signed-rank test were used to compare the parameters. The level of significance was set at ≤ 0.05.

RESULTS

A total of 40 patients were included, and 80 teeth were extracted. Profound anesthesia was achieved in all the cases. The mean subjective duration of anesthesia in the T-HCl and L-HCl groups was 130.80 ± 20.01 minutes and 111.40 ± 14.87 minutes, respectively, with a P value of .001. The mean Visual Analogue Scale (VAS) score for pain during the procedure in the T-HCl and L-HCl groups was 0.60 ± 0.67 and 1.10 ± 0.71, respectively, with a P value of .002. The mean Visual Analogue Scale score for pain postoperatively in the T-HCl and L-HCl groups was 0.70 ± 0.72 and 1.40 ± 0.67, respectively, with a P value of .001. Six patients in T-HCl required postoperative analgesia when compared to 18 patients in L-HCl (P value < .003).

CONCLUSIONS AND RELEVANCE

T-HCl provides similar anesthetic outcomes in the extraction of maxillary bicuspids as L-HCl.

Buprenorphine has a concentration-dependent cytotoxic effect on equine chondrocytes in vitro

OBJECTIVE

To investigate the cytotoxic effects of 2 different concentrations of buprenorphine and compare them with bupivacaine and morphine on healthy equine chondrocytes in vitro.

SAMPLE

Primary cultured equine articular chondrocytes from 3 healthy adult horses.

PROCEDURES

Chondrocytes were exposed for 0 and 2 hours to the following treatments: media (CON; negative control); bupivacaine at 2.2 mg/mL (BUPI; positive control); morphine at 2.85 mg/mL (MOR); buprenorphine at 0.12 mg/mL (HBUPRE); or buprenorphine at 0.05 mg/mL (LBUPRE). Chondrocyte viability was assessed using live/dead staining, water-soluble tetrazolium salt-8 (WST-8) cytotoxic assay, LDH assay, and flow cytometry. All continuous variables were evaluated with a mixed ANOVA with treatment, time, and their interactions as the fixed effects and each horse as the random effect.

RESULTS

Buprenorphine showed a concentration-dependent chondrotoxic effect. The viability of chondrocytes was significantly decreased with exposure to HBUPRE and BUPI compared to CON, MOR, and LBUPRE.

CLINICAL RELEVANCE

Negligible chondrotoxic effects were observed in healthy cultured equine chondrocytes exposed to 0.05 mg/mL of buprenorphine, whereas higher concentrations (0.12 mg/mL) showed a marked cytotoxic effect. Based on these results, low concentrations of buprenorphine appear to be safe for intra-articular administration. Further evaluation of this dose in vivo is needed before recommending its clinical use.

Comparative study of Local Anesthetic Efficacy of 5% Tramadol Versus 2%Lignocaine with 1:100,000 adrenaline for Extraction of fully erupted Maxillary 3rd molars using Infiltration Anesthesia

Introduction

The majority of dental procedures need local anesthesia for pain control, and lidocaine/ lignocaine is the most commonly used anesthetic agent in dentistry. Although effective and safest, the anesthetic agent still has some complications. To overcome these many alternatives have been used. Tramadol has been shown to have some local anesthetic (LA) effects when used for infiltration anesthesia in dentistry.

Methods

In the present study, the local anesthetic efficacy of tramadol was compared with 2% lignocaine containing 1: 100,000 adrenaline for the extraction of maxillary fully erupted 3rd molar teeth. The parameters recorded included the onset of action, duration of action, intraoperative pain, post-operative analgesic effect, and incidence of an allergic reaction. A total of 200 patients were randomly divided into two groups. In group A -Each patient received 0.6 ml of 5% tramadol (Tramataj- 50 mg prepared by Taj pharma company) 0.4 ml buccally and 0.2 ml palatally for extraction of maxillary 3rd molar as local infiltration following strict aseptic precaution. In Group B- patients received 0.6 ml of 2% lignocaine containing 1: 100,000 adrenaline buccally and 0.2 ml palatally as infiltrations.

Results

It was found that 5% tramadol has a local anesthetic efficacy similar to 2% lignocaine with adrenaline but was found to be a comparatively weaker agent.

Conclusion

tramadol is a valid alternative for performing extractions in normal patients or patients allergic to lidocaine.

Effectiveness of tramadol compared to lignocaine as local anesthesia in the extraction of firm teeth: a randomized controlled trial

Background

The aim of this study was to compare the local anesthetic effect of tramadol with that of lignocaine in the extraction of immobile (grade 0) maxillary first molars.

Methods

This was a randomized, double-blind, equally balanced, controlled trial conducted on a sample population of 116 patients. The patients were randomly divided into two groups: group A (control) and group B (study). Group A and group B participants received 1.8 ml of 2% lignocaine without adrenaline and 1.8 ml of 5% tramadol, respectively through the supra-periosteal infiltration technique before extraction. Intraoperative pain was recorded on the Visual Analog Scale (VAS) and was evaluated using two unpaired t-tests.

Results

Intraoperative pain was evaluated in both the control and study groups. In the control group, the mean VAS score was 0.71 ± 0.81, while in the study group, the mean intraoperative VAS score was 1.21 ± 0.86, with the difference between the two mean values being statistically significant (P = 0.001).

Conclusion

Tramadol has a less potent local anesthetic effect than lignocaine. As a higher dose of tramadol is required to obtain the desired anesthetic effect, it should be used as a supplement to lignocaine in extensive surgical procedures. It can also be used in patients allergic to lignocaine.

Inhibition of Fast Nerve Conduction Produced by Analgesics and Analgesic Adjuvants-Possible Involvement in Pain Alleviation

Nociceptive information is transmitted from the periphery to the cerebral cortex mainly by action potential (AP) conduction in nerve fibers and chemical transmission at synapses. Although this nociceptive transmission is largely inhibited at synapses by analgesics and their adjuvants, it is possible that the antinociceptive drugs inhibit nerve AP conduction, contributing to their antinociceptive effects. Many of the drugs are reported to inhibit the nerve conduction of AP and voltage-gated Na⁺ and K⁺ channels involved in its production. Compound action potential (CAP) is a useful measure to know whether drugs act on nerve AP conduction. Clinically-used analgesics and analgesic adjuvants (opioids, non-steroidal anti-inflammatory drugs, ₂-adrenoceptor agonists, antiepileptics, antidepressants and local anesthetics) were found to inhibit fast-conducting CAPs recorded from the frog sciatic nerve by using the air-gap method. Similar actions were produced by antinociceptive plant-derived chemicals. Their inhibitory actions depended on the concentrations and chemical structures of the drugs. This review article will mention the inhibitory actions of the antinociceptive compounds on CAPs in frog and mammalian peripheral (particularly, sciatic) nerves and on voltage-gated Na⁺ and K⁺ channels involved in AP production. Nerve AP conduction inhibition produced by analgesics and analgesic adjuvants is suggested to contribute to at least a part of their antinociceptive effects.

Tramadol hydrochloride: An alternative to conventional local anaesthetics for intraoral procedures- a preliminary study

Purpose

To evaluate and compare the soft tissue anaesthesia produced by tramadol hydrochloride on gingival tissues in maxilla.

Methods

A total of 50 ASA physical status I subjects between 18 and 35 years of age, both male and female were included in the study. Each individual received 0.5 ml of 50 mg tramadol in the soft tissues over maxillary canine tooth as local infiltration on one and 0.5 ml of 20 mg lignocaine on the contralateral side in a double-blinded fashion. After completing the injection, the author recorded pain on injection, the onset of action, duration of anaesthesia, side effects, and feedback from patient.

Results

The mean onset of anaesthesia for tramadol was 172.00 s (standard deviation 39.898) while for lignocaine it was 162.60 s (standard deviation 35.098) and there was no statistically significant difference between the two groups (p = 0.214). The mean duration of anaesthesia for tramadol group was 45.70 min with a standard deviation of 8.512 min whereas for lignocaine group it was 44.70 min with a standard deviation of 8.107 min. There was no statistical relevant difference between the two groups in duration of anaesthesia (p = 0.549). None of the subjects reported any side effect in both the groups. There was no significant difference in pain on injection between the two groups.

Conclusions

Tramadol has a local anaesthetic effect similar to lignocaine when injected as infiltration in oral soft tissues.

Comparison of Local Anaesthetic Efficacy of Tramadol Versus Lignocaine for Extraction of Tooth Under Supraperiosteal Infiltration

Background

Tramadol has been shown to have a local anaesthetic effect when used as infiltration anaesthesia.

Methods

The local anaesthetic efficacy of tramadol was compared with that of lignocaine for the extraction of teeth in terms of their onset of action, duration of action, intraoperative pain, post-operative analgesic effect and adverse reactions. Apart from this, incidence of allergic reaction was also recorded for both the drugs. A total of 100 patients were divided into two groups randomly. Each patient was assigned to receive either a maximum of 2 ml of 5% tramadol (Supridol 50 mg, Neon laboratories), Group T (n = 50), as a local anaesthetic solution for extraction of maxillary premolar for orthodontic reason under supraperiosteal infiltration following strict aseptic precaution or a maximum of 2 ml of 2% lignocaine (Lox 2%, Neon laboratories), Group L (n = 50), in a double-blinded fashion.

Results

In group T, the mean subjective onset of action was 33.66 s, while in group L it was 33.06 s (p = 0.881). In group T, the mean objective onset of action was 3.04 min, while in group L it was 3.18 min (p > 0.05). The mean duration of action in group T was 55.60 min, while in group L it was 57.50 min (p = 0.432). Only 2 patients in group T and 1 patient in group L had nausea (p = 0.245).

Conclusion

We conclude that 5% tramadol has a local anaesthetic efficacy similar to 2% lignocaine but is comparatively a weaker agent.

In Vitro Chondrotoxicity of Nonsteroidal Anti-inflammatory Drugs and Opioid Medications

BACKGROUND

A variety of medications are administered to the intra-articular space for the relief of joint pain. While amide-type local anesthetics have been extensively studied, there is minimal information regarding the potential chondrotoxicity of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid medications.

PURPOSE

To investigate the in vitro chondrotoxicity of single-dose equivalent concentrations of ketorolac, morphine, meperidine, and fentanyl on human chondrocytes.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human cartilage was arthroscopically harvested from the intercondylar notch and expanded in vitro. Gene expression of cultured chondrocytes before treatment was performed with quantitative polymerase chain reaction for type I collagen, type II collagen, aggrecan, and SOX9. Chondrocytes were then exposed to 0.01%, 0.02%, and 0.04% morphine sulfate; 0.3% and 0.6% ketorolac tromethamine; 0.5%, 1.0%, and 1.5% meperidine hydrochloride; 0.0005% and 0.001% fentanyl citrate; and saline. A custom bioreactor was used to constantly deliver medications, with the dosage of each medication and the duration of exposure based on standard dose equivalents, medication half-lives, and differences in the surface area between the 6-well plates and the native joint surface. After treatment, a live/dead assay was used to assess chondrocyte viability and if minimal cell death was detected. A subset of samples after treatment was maintained to analyze for possible delayed cell death.

RESULTS

All tested concentrations of ketorolac and meperidine caused significantly increased cell death versus the saline control, demonstrating a dose-response relationship. The morphine and fentanyl groups did not show increased chondrotoxicity compared with the saline group, even after 2 weeks of additional culture.

CONCLUSION

In vitro exposure of chondrocytes to single-dose equivalent concentrations of either ketorolac or meperidine demonstrated significant chondrotoxicity, while exposure to morphine or fentanyl did not lead to increased cell death.

An early granulocyte colony-stimulating factor treatment attenuates neuropathic pain through activation of mu opioid receptors on the injured nerve

Several studies have shown that the mu opioid receptor (MOR) located in the peripheral nerves can be activated after nerve injury and that it attenuates peripheral nociceptive signals to the spinal dorsal horn. Various cytokines and phosphorylated-p38 (p-p38) activation in the dorsal horn also play an important role in neuropathic pain development. Granulocyte-colony stimulating factor (GCSF) is a growth factor that can stimulate granulocyte formation and has been shown to exert an analgesic effect on neuropathic pain through recruiting opioid-containing leukocytes to the injured nerve. However, the underlying mechanisms are not well understood. Herein, the results of behavior tests in addition to MOR levels in the injured sciatic nerve and the levels of p-p38 and various cytokines in the spinal dorsal horn were studied in vehicle-treated or GCSF-treated chronic constriction injured (CCI) rats at different time points (i.e., 1, 3, and 7 days, respectively) after nerve injury. The results showed that a single early systemic GCSF treatment after nerve injury can up-regulate MORs in the injured nerve, which can decrease peripheral nociceptive signals. Thereafter, those changes suppress the pro-inflammatory cytokine IL-6 but enhance the anti-inflammatory cytokine IL-4, followed by decreases in p-p38 in the dorsal horn, and thus further attenuate neuropathic pain.

The effect of intra-articular meperidine and bupivacaine 0.5% on postoperative pain of arthroscopic knee surgery; a randomized double blind clinical trial

Background:

Arthroscopic knee surgeries have a painful postoperative course, which often necessitates acute pain management. Among different analgesia techniques, Intra-articular injection is the technique of choice for many pain specialists, based on its confined effect to the surgical site (knee), lack of systemic effects and promotion of safe early ambulation.

Objectives:

The aim of this study was to compare analgesic effects of intra-articular meperidine, bupivacaine 0.5% or their combination after knee arthroscopic surgery.

Patients and Methods:

Sixty ASA class I-II patients’ candidates for arthroscopy knee surgery enrolled in a randomized double blind study to receive either 20 mL of bupivacaine 0.5%; 100 mg meperidine (diluted in normal saline) or bupivacaine 0.5% along with 100 mg meperidine. A written informed consent was obtained from all patients. Postoperative analgesia duration, VAS at 2, 6, 12 and 24 hours, the first analgesic request time, total fentanyl consumption in first 24 hours, patients’ satisfaction and adverse effects were recorded.

Results:

The bupivacaine-meperidine group had better duration of postoperative analgesia (P = 0.001), latter first analgesic request (P ≤ 0.001), lower total fentanyl consumption in first 24 hours after the operation (P = 0.001), less mean VAS at 2 hours (P = 0.001) and more patients’ overall satisfaction (P = 0.01) compared with each medication alone. VAS at 6, 12 and 24 postoperative hours were not different between the groups of study. No adverse effects were observed.

Conclusions:

Although postoperative intra-articular meperidine is a better alternative for bupivacaine, their combination could improve their analgesic effects compared with each other alone.

Effects of opioids on local anesthesia in the rat: a codeine and tramadol study

Opioids are central analgesics that act on the CNS (central nervous system) and PNS (peripheral nervous system). We investigated the effects of codeine (COD) and tramadol (TRAM) on local anesthesia of the sciatic nerve. Eighty Wistar male rats received the following SC injections in the popliteal fossa: local anesthetic with epinephrine (LA); local anesthetic without vasoconstrictor (LA WV); COD; TRAM; LA + COD; LA + TRAM; COD 20 minutes prior to LA (COD 20' + LA) or TRAM 20 minutes prior to LA (TRAM 20' + LA). As a nociceptive function, the blockade was considered the absence of a paw withdraw reflex. As a motor function, it was the absence of claudication. As a proprioceptive function, it was the absence of hopping and tactile responses. All data were compared using repeated-measures analysis of variance (ANOVA). Opioids showed a significant increase in the level of anesthesia, and the blockade duration of LA + COD was greater than that of the remaining groups (p < 0.05). The associated use of opioids improved anesthesia efficacy. This could lead to a new perspective in controlling dental pain.

Comparison of local anesthetic effects of lidocaine versus tramadol and effect of child anxiety on pain level in circumcision procedure

OBJECTIVE

To compare the local anesthetic effects of tramadol hydrochloride with those of lidocaine in circumcision procedures. We also investigated the effect of child anxiety on pain level.

PATIENTS AND METHODS

A total of 70 children were included in this study. The children were randomized into 3 groups. Group 1 (n = 26) received lidocaine hydrochloride + epinephrine and they underwent circumcision using Ali's clamp(®). Group 2 (n = 35) received lidocaine hydrochloride + epinephrine and group 3 (n = 12) 5% tramadol. The last two groups underwent conventional circumcision.

RESULTS

The mean anxiety score was 22.6. We did not find significant differences in terms of anxiety score among the groups (p = 0.761). When the pain scores of the groups during injection were compared, it was found that there were no significant differences. However, the pain score of the third group was significantly high when it was compared with the first and second group 2 and 10 min after injection. In the correlation analysis, we found a positive correlation between children's anxiety scores and the pain degree during injection (r = 0.373, p = 0.001).

CONCLUSION

Tramadol may not provide effective local anesthesia in male circumcision. The child's anxiety before the circumcision seems to have a negative effect on pain level.

Fentanyl decreases discharges of C and A nociceptors to suprathreshold mechanical stimulation in chronic inflammation

An essential component of mechanical hyperalgesia resulting from tissue injury is an enhanced excitability of nociceptive neurons, termed mechanical sensitization. Local application of opioids to inflamed rat paws attenuates mechanical hyperalgesia and reduces electrical excitability of C-fiber nociceptors in acute injury. Here, we examined the effects of the opioid receptor agonist fentanyl on the mechanical coding properties of not only C- but also A-fiber nociceptors innervating the rat hind paw in a model of chronic pain, i.e., 4 days after Freund's complete adjuvant-induced inflammation. The peripheral mechanosensitive terminals of C-fibers (n = 143), A-fibers (n = 79), and low-threshold mechanoreceptors (n = 25) were characterized using the in vitro skin-nerve preparation from the saphenous nerve. Although mechanical activation thresholds were not changed, discharges to suprathreshold mechanical stimuli were elevated significantly in both A- and C-fiber nociceptors from inflamed tissue. In addition, the proportion of nociceptors as well as the frequency of spontaneous discharges in A (14% vs. 0%)- and C (28% vs. 8%)-fibers were increased in inflamed compared with normal tissue. Fentanyl inhibited responses to suprathreshold stimuli in a significantly higher proportion of not only C (36% vs. 7%)- but also A (41% vs. 8%)-fibers in inflamed tissue in a naloxone-reversible and concentration-dependent manner. Our results demonstrate that mechanical sensitization persists in chronic inflammation, in correlation with behavioral hyperalgesia. Opioid sensitivity of both A- and C-fibers is markedly augmented. This is consistent with an upregulation or enhanced functionality of opioid receptors located at the peripheral terminals of sensitized nociceptors.

Local infiltrative anesthetic effect of tramadol compared to lidocaine for excision of cutaneous lesions: pilot randomized, double-blind clinical study

BACKGROUND

In this double-blind, randomized study, the efficacy of tramadol, an atypical opioid, was tested versus lidocaine in excision of cutaneous lesions of the face.

METHODS

Eighty-eight patients were randomly assigned to receive either 2 mg/kg tramadol 2% plus adrenaline 1:200,000 (group T, n  =  46) or 3 mg/kg lidocaine 2% plus adrenaline 1:200,000 (group L, n  =  42) for excision of cutaneous lesions. Pain at the injection site, 2 and 20 minutes postinjection and 3, 6, and 12 hours postoperatively, was monitored on a 0 to 10 numerical rating scale (NRS). Irritation at the injection point and the duration of postoperative analgesia were also recorded.

RESULTS

There were no significant differences in demographic data, topography, size of the lesions removed, and operative time between the two groups. A tendency toward lower injection NRS pain scores was observed in group L compared to group T (p  =  .064). No statistically significant differences between the two groups were found at 2 and 20 minutes postinjection (p  =  .741 and p  =  .142, respectively); however, pain scores were significantly higher in group L at 3, 6, and 12 hours postoperatively (all p < .001). Erythema at the injection site was observed in nine group T and two group L patients (p  =  .076). No postoperative analgesics were required in the tramadol group of patients, whereas acetaminophen with or without codeine was administered in all but five lidocaine group patients during the first 12 hours.

CONCLUSION

Tramadol may be used as a reliable local anesthetic agent, providing longer postoperative analgesia compared to lidocaine; however, it bears a higher incidence of irritation at the injection site.

Comparison of three different analgesic protocols during shockwave lithotripsy

BACKGROUND AND PURPOSE

Shockwave lithotripsy (SWL) is one of the most important treatment modalities for urinary stone disease. The procedure may cause pain, and patient relaxation and cooperation are crucial in maintaining stone localization for optimal fragmentation and patient comfort during the procedure. As yet, there is not a standard analgesic protocol for patients undergoing SWL. We aimed to use three different analgesic agents and compare their efficacy during SWL in this study.

PATIENTS AND METHODS

Written informed consents were obtained from 95 patients with kidney stones, and they were randomized to receive lornoxicam (group L, n=32 patients), paracetamol (group P, n=31 patients), and tramadol with a patient-controlled analgesia device (group T, n=32 patients). All groups received patient-controlled analgesia with tramadol during the SWL procedure. The intensity of pain was evaluated with a visual analog scale (VAS).

RESULTS

The mean age of the patients was 41.87 ± 16.53 years, 44.07 ± 11.48 years, and 41.24 ± 14.82 years in group L, group P, and group T, respectively. No significant differences were found between the three groups concerning patient age, stone location, or session duration (P>0.05). The mean VAS scores and analgesic consumption were lower in group L compared with other groups (P<0.05).

CONCLUSION

The results of this study showed that additional administration of analgesics was decreased with intravenous lornoxicam in comparison with paracetamol and only tramadol.

Perineural meperidine blocks nerve conduction in a dose-related manner: a randomized double-blind study

BACKGROUND

Meperidine has been shown to exhibit a sensory block in peripheral nerves. However, its motor blockade ability is controversial. The aim of this study was to investigate, electroneurographically, the ability of meperidine to inhibit conduction in both sensory and motor fibres in the ulnar nerve.

MATERIALS AND METHODS

The study was conducted in a double-blind, placebo-controlled fashion. Eighteen healthy volunteers were randomized into three groups (Saline, meperidine 1% and meperidine 2%). Three millilitre of the study solution was administered to the ulnar nerve perineurally at the level of the wrist by the guidance of a nerve stimulator. Sensory nerve action potential (SNAP) and compound motor action potential (CMAP) amplitudes were recorded. At least a 20% decrease in the initial response amplitude was accepted as a block.

RESULTS

The number of individuals with sensory and motor block with saline, meperidine 1% and meperidine 2% were 0/6, 6/6, 6/6 and 0/6, 5/6, 6/6, respectively (P<0.05). The maximum decrease in the median SNAP and CMAP amplitude values were 4.7% and 8.3% with saline; 38.5% and 46.4% with meperidine 1%; and 100% and 97.8% with meperidine 2%, respectively (P<0.05). Median values for the duration of sensory and motor block with meperidine 1% and meperidine 2% were 45, 52.5 and 30, 32.5 min, respectively.

CONCLUSION

Meperidine blocks sensory and motor nerve conduction in a dose-related manner.

Does pethidine affect the cardiovascular and sedative effects of dexmedetomidine in dogs?

OBJECTIVES

To investigate pethidine's effects on sedation and cardiovascular variables in dogs premedicated with dexmedetomidine.

METHODS

Sixty American Society of Anesthesiologists (ASA) I dogs were presented for routine neutering. Heart rate was measured at admission. Dogs were randomly assigned to one of the five groups to decide premedication; group D5+P (dexmedetomidine 5 microg/kg plus pethidine 5 mg/kg), D10+P (dexmedetomidine 10 microg/kg plus pethidine 5 mg/kg) with three control groups, D5 (dexmedetomidine 5 microg/kg), D10 (dexmedetomidine 10 microg/kg) or P (pethidine 5 mg/kg). Heart rate was measured at 3, 5, 10 and 20 minutes after preanaesthetic medication. Simple descriptive scores for sedation were assigned after 20 minutes. Anaesthesia was induced using propofol and maintained using isoflurane in oxygen. Heart rate was recorded throughout anaesthesia.

RESULTS

Sedation scores after preanaesthetic medication were significantly higher (P<0.001) in groups D5+P and D10+P compared with the other three groups. D5+P and D10+P groups tended to have lower heart rates in dogs at all time points after premedication compared with groups containing only pethidine or dexmedetomidine at the relevant dose.

CLINICAL SIGNIFICANCE

Greater sedation is achieved using combinations of dexmedetomidine and pethidine compared with each drug alone. Pethidine does not attenuate the alpha-2 adrenergic-induced bradycardia.

Tramadol as a local anaesthetic in tendon repair surgery of the hand

This double-blind pilot study compared the local anaesthetic effects of tramadol plus adrenaline with lidocaine plus adrenaline during surgery to repair hand tendons. Twenty patients were randomly allocated to receive either 5% tramadol plus adrenaline (n = 10) or 2% lidocaine plus adrenaline (n = 10). Injection site pain and local skin reactions were recorded. At 1-min intervals after injection of the anaesthetic agent, the degree of sensory blockade was assessed by the patient reporting the extent to which they felt a pinprick, light touch and a cold sensation. Pain felt during surgical incision was also recorded. There was no difference in the quality of sensory blockade or the incidence of side effects between the two groups. Only patients treated with tramadol did not require additional post-operative analgesia. A combination of tramadol plus adrenaline provided a local anaesthetic effect similar to that of lidocaine plus adrenaline.

Inhibitory effects of opioids on compound action potentials in frog sciatic nerves and their chemical structures

An opioid tramadol more effectively inhibits compound action potentials (CAPs) than its metabolite mono-O-demethyl-tramadol (M1). To address further this issue, we examined the effects of opioids (morphine, codeine, ethylmorphine and dihydrocodeine) and cocaine on CAPs by applying the air-gap method to the frog sciatic nerve. All of the opioids at concentrations less than 10 mM reduced the peak amplitude of the CAP in a reversible and dose-dependent manner. The sequence of the CAP peak amplitude reductions was ethylmorphine>codeine>dihydrocodeine> or = morphine; the effective concentration for half-maximal inhibition (IC(50)) of ethylmorphine was 4.6 mM. All of the CAP inhibitions by opioids were resistant to a non-specific opioid-receptor antagonist naloxone. The CAP peak amplitude reductions produced by morphine, codeine and ethylmorphine were related to their chemical structures in such that this extent enhanced with an increase in the number of -CH(2) in a benzene ring, as seen in the inhibitory actions of tramadol and M1. Cocaine reduced CAP peak amplitudes with an IC(50) value of 0.80 mM. It is concluded that opioids reduce CAP peak amplitudes in a manner being independent of opioid-receptor activation and with an efficacy being much less than that of cocaine. It is suggested that the substituted groups of -OH bound to the benzene ring of morphine, codeine and ethylmorphine as well as of tramadol and M1, the structures of which are quite different from those of the opioids, may play an important role in producing nerve conduction block.

The addition of adrenaline to thoracic epidural meperidine does not improve analgesia following thoracotomy

PURPOSE

Patient-controlled epidural analgesia (PCEA) with meperidine provides effective analgesia following thoracotomy. Accumulation of normeperidine, a meperidine metabolite with neuroexcitatory effects, has led to recommendations to limit the use of meperidine postoperatively. The purpose of this study was to determine if the addition of adrenaline to PCEA meperidine decreased meperidine consumption, reduced serum normeperidine levels, and improved analgesia following thoracotomy.

METHODS

Following Research Ethics approval consenting patients were randomly assigned to PCEA with either meperidine (2 mgxmL(-1)) + adrenaline (2 microgxmL(-1)) or meperidine alone (2 mgxmL(-1)). All patients received a standardized anesthetic and similar perioperative care. Visual analogue pain scores (at rest and with activity), quality of recovery (QoR) scores, and side effects were documented six, 24, and 48 hr postoperatively. Serum levels of meperidine and normeperidine were measured at the same time points.

RESULTS

Forty-six patients completed the study protocol. Meperidine consumption (mean+/-SD) was similar in the meperidine + adrenaline and the meperidine groups (601+/-211 mg vs 580+/-211 mg over 48 hr, respectively; P=0.744). Serum meperidine levels were similar at all study time points. Serum normeperidine was not detected in any sample. Pain scores, QoR scores, and adverse events were comparable in both study groups.

CONCLUSION

The addition of adrenaline did not influence PCEA meperidine consumption, analgesia outcomes, or QoR. Normeperidine did not accumulate in patients of either study group during the 48-hr study period. Meperidine for patient controlled epidural analgesia, with or without adrenaline, provides effective post-thoracotomy analgesia in selected patients.

Anesthetic Efficacy of Lidocaine/Meperidine for Inferior Alveolar Nerve Blocks in Patients with Irreversible Pulpitis

The purpose of this prospective, randomized, single-blind study was to compare the anesthetic efficacy of lidocaine with epinephrine to lidocaine plus meperidine with epinephrine for inferior alveolar nerve blocks (IAN) in patients with mandibular posterior teeth experiencing irreversible pulpitis. Forty-eight emergency patients diagnosed with irreversible pulpitis of a mandibular posterior tooth randomly received, in a single-blind manner, 36 mg of lidocaine with 18 mug epinephrine or 36 mg of lidocaine with 18 mug of epinephrine plus 36 mg meperidine with 18 mug epinephrine, using a conventional inferior alveolar nerve block. Endodontic access was begun 15 minutes after solution deposition, and all patients were required to have profound lip numbness. Success was defined as no or mild pain (visual analog scale recordings) upon endodontic access or initial instrumentation. The success rate for the inferior alveolar nerve block using the lidocaine solution was 26%, and for the lidocaine/meperidine solution, the success rate was 12%. There was no significant difference (p = 0.28) between the two solutions. In conclusion, for mandibular posterior teeth with irreversible pulpitis, the addition of 36 mg of meperidine to a lidocaine solution administered in a conventional IAN block did not improve the success rate over a standard lidocaine solution.

Tramadol, fentanyl and sufentanil but not morphine block voltage-operated sodium channels

Lidocaine-like sodium channel blocking drugs provide pain relief either by interrupting impulse conduction in neurons when applied locally in high concentrations or, when given systemically, by suppressing high-frequency ectopic discharges due to preferential drug binding to inactivated channel states. Lidocaine-like actions of opioids have frequently been demonstrated clinically. However, drug binding to resting and inactivated channel conformations has been studied systematically only in the case of meperidine. The aim of this in vitro study was to investigate the effects of four currently used opioids on heterologously expressed neuronal (NaV(1.2)) voltage-gated sodium channels. Block of sodium currents was studied at hyperpolarized holding potentials and at depolarized potentials inducing either fast- or slow-inactivation. Sufentanil, fentanyl and tramadol but not morphine reversibly suppressed sodium inward currents at high concentrations (half-maximum blocking concentrations (IC50) 49+/-4, 141+/-6 and 103+/-8 microM) when depolarizations were started from hyperpolarized holding potentials. Short depolarizations inducing fast-inactivation and long prepulses inducing slow-inactivation significantly (*p < or = 0.001) increased the blocking potency for these opioids. 15% slow inactivated channels reduced the respective IC50 values to 5+/-3, 12+/-2 and 21+/-2 microM. These results show that: (1) Sufentanil, fentanyl and tramadol block voltage-gated sodium channels with half-maximum inhibitory concentrations similar to the IC50 reported for meperidine. (2) Slow inactivation--a physiological mechanism to suppress ectopic activity in response to slow shifts in membrane potential--increases binding affinity for sufentanil, fentanyl and tramadol. (3) Morphine has no such effects.

Tramadol, but not its major metabolite (mono-O-demethyl tramadol) depresses compound action potentials in frog sciatic nerves

BACKGROUND AND PURPOSE

Although tramadol is known to exhibit a local anaesthetic effect, how tramadol exerts this effect is not understood fully.

EXPERIMENTAL APPROACH

The effects of tramadol and its metabolite mono-O-demethyl-tramadol (M1) on compound action potentials (CAPs) were examined by applying the air-gap method to frog sciatic nerves, and the results were compared with those of other local anaesthetics, lidocaine and ropivacaine.

KEY RESULTS

Tramadol reduced the peak amplitude of the CAP in a dose-dependent manner (IC50=2.3 mM). On the other hand, M1 (1-2 mM), which exhibits a higher affinity for mu-opioid receptors than tramadol, did not affect CAPs. These effects of tramadol were resistant to the non-selective opioid receptor antagonist naloxone and the mu-opioid receptor agonist, DAMGO, did not affect CAPs. This tramadol action was not affected by a combination of the noradrenaline uptake inhibitor, desipramine, and the 5-hydroxytryptamine uptake inhibitor, fluoxetine. Lidocaine and ropivacaine also concentration-dependently reduced CAP peak amplitudes with IC50 values of 0.74 and 0.34 mM, respectively.

CONCLUSIONS AND IMPLICATIONS

These results indicate that tramadol reduces the peak amplitude of CAP in peripheral nerve fibres with a potency which is less than those of lidocaine and ropivacaine, whereas M1 has much less effect on CAPs. This action of tramadol was not produced by activation of mu-opioid receptors nor by inhibition of noradrenaline and 5-hydroxytryptamine uptake. It is suggested that the methyl group present in tramadol but not in M1 may play an important role in producing nerve conduction block.

Comparative effects of lidocaine and tramadol on injured peripheral nerves

The aim of the present study was to investigate the action of lidocaine and tramadol on the abnormal impulse characteristics of injured peripheral nerves. The ultrastructure of nerves was studied with electron microscopy and the action of lidocaine and tramadol on intact and injured rat sciatic nerves was examined by using the sucrose gap recording technique. Tramadol and lidocaine caused concentration- and frequency-dependent decreases in the amplitude of the compound action potential. Injured nerves were more sensitive to lidocaine than to tramadol. Lidocaine suppressed the delayed depolarization and decreased the hyperpolarizing afterpotentials to a greater extent than did tramadol. A low concentration of lidocaine may restore the abnormal impulse characteristics of injured nerves without changing the normal impulse pattern. The efficacy of lidocaine and inefficacy of tramadol on abnormal impulse characteristics may contribute, at least in part, to our understanding of the mechanisms of action of these drugs in neuropathic pain therapy.

Effects of thoracic epidural meperidine on arterial oxygenation during one-lung ventilation in thoracic surgery

OBJECTIVE

To compare the effects that the use of general intravenous anesthesia (propofol-fentanyl) (GA) or general anesthesia combined with thoracic epidural anesthesia with meperidine (TEA-M) may have on arterial oxygenation during one-lung ventilation (OLV).

DESIGN

Prospective.

SETTING

Tertiary care hospital.

PARTICIPANTS

Seventy-two patients undergoing OLV for thoracic surgery.

INTERVENTIONS

Patients were prospectively randomized into two groups: GA (n = 37) fentanyl, propofol, rocuronium anesthesia was used; and group TEA-M (n = 35) were anesthetized with propofol, rocuronium and thoracic epidural meperidine (2 mg/kg in 10-12 mL) administered before anesthetic induction. A double-lumen endotracheal tube was inserted, and mechanical ventilation with 100% oxygen was used during study. Mean arterial pressure, heart rate and arterial and venous blood gases were recorded with the patients in the lateral decubitus position in three phases: during two-lung ventilation (TLV), 15 and 30 minutes after beginning OLV (OLV + 15 and OLV + 30 respectively). The authors measured arterial and venous central oxygen tension, arterial and venous central oxygen saturation, arterial and venous central oxygen content and venous admixture percentage (Qs/Qt%).

MEASUREMENTS AND MAIN RESULTS

There were no statistical differences between the two groups for PaO(2) during OLV + 15 (GA = 165 mmHg, TEA-M = 153 mmHg) and OLV + 30 (GA = 176 mmHg, TEA-M = 158 mmHg); and with values for Qs/Qt%.

CONCLUSIONS

It is concluded that GA combined with TEA-M (2 mg/kg) do not affect arterial oxygenation during OLV in thoracic surgery.

Comparison of local anaesthetic effects of tramadol with prilocaine for minor surgical procedures

BACKGROUND

Recent studies have shown that a local anaesthetic action of tramadol 5% was able to induce a sensory block to pinprick, touch, and cold similar to that of lidocaine 1%. The aim of this study was to compare the local anaesthetic effects of tramadol hydrochloride with prilocaine.

METHODS

Sixty ASA I or II patients, undergoing excision of the cutaneous lesions under local anaesthesia, were included in the study. Patients were randomly assigned to receive either 1 ml of tramadol 5% (Group T, n=30) or 1 ml of prilocaine 2% (Group P, n=30) intradermally, in a double-blinded fashion. The degree of the burning sensation and pain at the injection site was documented. Sensory block was assessed 1 min after injection. The patient was asked to report the degree of sensation and to grade touch and pinprick sensation. Two minutes after drug administration, incision was performed and intensity of pain, felt by the patient was evaluated on a four-point scale (0-3). Any local adverse effects were recorded.

RESULTS

There was no difference in the quality of block between the two groups. Side effects were noted in both groups with a significant increase in the incidence of local reaction (rash) in Group T (seven patients) when compared with Group P (one patient) (P<0.05). Seven patients in Group T vs four patients in Group P complained of burning at the injection site (P>0.05).

CONCLUSIONS

Intradermal tramadol 5% can provide a local anaesthesia similar to the prilocaine but the incidence of local adverse effects is higher.

The effects of intrathecal tramadol on spinal somatosensory-evoked potentials and motor-evoked responses in rats

Tramadol has been proven to exert a local anesthetic-type effect on peripheral nerves in both clinical and laboratory studies. In this study, we evaluated the effects of tramadol on sensory and motor neural conduction when administered intrathecally in the rat. Tramadol (0, 1, or 2 mg) was administered through an intrathecal catheter. Spinal somatosensory-evoked potentials (SSEPs) were recorded at the thoracolumbar junction after stimulation of the sciatic nerve. An evoked compound muscle action potential (CMAP) was recorded in the intrinsic muscles of the foot in response to electric stimulation of the lower thoracic (T1213) interspinous space. Both SSEP and CMAP were obtained before drug application as the pretreatment baseline and at 5, 15, and 30 min after treatment, and at 30- or 60-min intervals thereafter for another 4.5 h. SSEP was averaged from 20 responses, whereas CMAP was obtained from a single stimulation. Reproducible SSEPs and CMAP were consistently recorded in all rats. Intrathecal tramadol dose-dependently reduced the amplitude and delayed the latency in both SSEPs and CMAP. Generally, the suppressive effects occurred immediately after injection and recovered over 2 h. Combined administration with 20 micro g of intrathecal naloxone did not attenuate the inhibition of spinal SSEPs. We conclude that intrathecal tramadol causes a dose-related suppressive effect on both sensory and motor neural conduction in the spinal cord.

IMPLICATIONS

Spinal somatosensory-evoked potentials and evoked compound muscle action potential were used to evaluate the effects of intrathecal tramadol on sensory and motor neural conduction. Intrathecal tramadol dose-dependently reduced the amplitude and delayed the latency of both spinal somatosensory-evoked potentials and compound muscle action potential. These results indicate that tramadol exerts a dose-related central neural blockade.

Transient neurological symptoms after subarachnoid meperidine

IMPLICATIONS

The syndrome of transient neurological symptoms (TNS) after subarachnoid use of local anesthetics, particularly lidocaine, has been well described. This syndrome has not been reported with the subarachnoid use of opioids. This case report describes TNS that occurred after administration of subarachnoid meperidine, an opioid with local anesthetic properties.

Direct Tramadol Application on Sciatic Nerve Inhibits Spinal Somatosensory Evoked Potentials in Rats

We sought to determine the possible neural conduction blockade of tramadol and whether there is evidence of localized neural toxicity with spinal somatosensory evoked potential (SSEP) measurements. Male Wistar rats were used. SSEP, elicited by supramaximally stimulating the hind paw and recorded from the thoracolumbar and the first and second lumbar interspinous ligaments, was monitored. SSEPs were obtained before drug application as the pretreatment baseline and measured every 15 min after treatment for 2 h and at 60-min intervals thereafter until SSEP returned to baseline or for another 4 h. Two small strips of Gelfoam (0.6 x 1.0 cm(2)) soaked with the drug were placed under and over the left sciatic nerve for a 30-min period. Gelfoam was prepared with tramadol hydrochloride (Tramal; the US trade name is Ultram) 5, 2.5, and 1.25 mg, diluted if needed with saline to a total volume of 100 microL (5%, 2.5%, and 1.25%, respectively). The control data were obtained from the right side limb with normal saline by following the same method. Spinal SSEPs were measured after 48 h to detect the late neural damage. The results showed that direct tramadol application on sciatic nerves dose-dependently reduced both the amplitude and conduction velocity of SSEPs when compared with the pretreatment baseline. All SSEPs returned to pretreatment baseline, and no significant changes of SSEP between bilateral limbs were noted at the 48-h measurements. No evidence of irreversible conduction blockade indicative of local neural toxicity was seen. Pretreatment with naloxone 1 mg/kg failed to block the changes of SSEP produced by 2.5% tramadol 100 microL. We conclude that tramadol exerts a local anesthetic-type effect on peripheral nerves.

Selective spinal anesthesia for outpatient laparoscopy. III: sufentanil vs lidocaine-sufentanil

PURPOSE

The efficacy of low dose intrathecal lidocaine-sufentanil was compared with intrathecal sufentanil for short duration outpatient gynecological laparoscopy.

METHODS

Thirteen ASA I and II patients undergoing gynecological laparoscopy were studied in a randomized double-blind trial. Patients received either intrathecal 10 mg lidocaine plus 10 microg sufentanil (Group LS) or intrathecal 20 microg sufentanil (Group S), each diluted to 3 mL with sterile water through a 27g Whitacre needle in the sitting position. Sensory and motor recovery were assessed with pinprick and a modified Bromage scale.

RESULTS

One of seven Group LS patients and two of five Group S patients required conversion to general anesthesia for failed skin test with forceps. Two of the remaining three Group S patients felt sharpness with skin incision. The study was terminated early because of inadequate anesthesia in Group S. The small sample size (n = 9) made statistical analysis uninformative.

CONCLUSION

Intrathecal 20 microg sufentanil is unsuitable as a sole agent for gynecological laparoscopy.

Peripheral and preemptive opioid antinociception in a mouse visceral pain model

Recent studies suggest that opioids can produce analgesia through peripheral mechanisms following inflammation of peripheral tissue. This study examined whether opioids administered prior to inflammation can produce antinociception by peripheral mechanisms in a model of visceral pain. Mice were injected intraperitoneally (i.p.) with 1% acetic acid to evoke abdominal writhing, a standard model of visceral pain. The number of writhes that occurred during 30 min after acetic acid were determined. Intraperitoneal injection of morphine sulfate (60, 90, 100 or 120 microg/0.3 ml) or the peripherally acting opioid loperamide (0.12, 0.36, 1.2 or 3.6 mg/0.3 ml) given 5 min after acetic acid decreased writhing in a dose-dependent fashion. Morphine (100 microg) produced an 70% attenuation in the number of writhes while loperamide (1.2 mg) decreased writhing by 56%. These antinociceptive effects were blocked by pretreatment with the opioid receptor antagonists naloxone (10 mg/kg) and its quarternary version naloxone methiodide (10 mg/kg). To determine whether opioids produced preemptive antinociception via peripheral mechanisms, mice received i.p. injections of morphine (1, 5, and 10 microg/0.3 ml) or vehicle 5 min before acetic acid. Doses of 5 and 10 microg morphine inhibited the number of writhes by 51 and 93%, respectively. The highest dose (10 microg) was ineffective when given intravenously 5 min before acetic acid, suggesting that antinociception following i.p. administration was acting via peripheral mechanisms. These data demonstrate that low doses of opioids, given before or after acetic acid, produce visceral antinociception through peripheral mechanisms. This may be clinically relevant for the management of postoperative abdominal pain.

Adding low dose meperidine to spinal lidocaine prolongs postoperative analgesia

PURPOSE

To investigate the effects of the addition of low dose meperidine to spinal lidocaine on the sensory and motor blockade profile, and the quality and duration of postoperative analgesia.

METHODS

In a randomized double blind prospective dose finding study 40 patients undergoing transurethral prostatectomy with spinal anesthetic were allocated to receive 75 mg lidocaine 5% intrathecally as the sole agent (group A), or co-administered with 0.15 mg x kg(-1) meperidine (group B) or 0.30 mg x kg(-1) meperidine (group C). Sensory and motor blockade profiles were documented. Postoperatively, the amount of analgesics required, time to first analgesic, visual analogue scores and adverse events were recorded.

RESULTS

Sensory blocks at or above T10 was maintained for 128, 156 and 145 minutes in groups A, B and C respectively. There was no difference in the latency or duration of the motor block among the three groups. Patients in group C had lower visual analogue pain scores (VAPS) over time than did those in groups A and B (P < 0.05). Time to first analgesia was longer (429 +/- 197 minutes) in group C than in group A (254 +/- 157 minutes) (P < 0.05). Fewer patients in group C required parenteral opioid postoperatively than in group A (P < 0.05). The incidence of bradycardia was higher in the groups receiving meperidine. No symptoms of transient radicular irritation (TRI) were reported in the groups receiving meperidine.

CONCLUSION

The addition of 0.3 mg x kg(-1) of meperidine to spinal lidocaine prolongs postoperative analgesia without delaying discharge from post anesthetic care unit (Table II) and reduces the requirement for parenteral analgesics (Table III).

The analgesic effect of fentanyl, morphine, meperidine, and lidocaine in the peripheral veins: a comparative study

Using venous retention with a tourniquet (70 mm Hg), we performed a randomized, double-blind study to assess the efficacy of I.V. pretreatment with fentanyl, morphine, meperidine, or lidocaine in reducing propofol injection pain. Immediately after venous occlusion with a tourniquet, I.V. fentanyl 150 microg (Group A, n = 35), morphine 4 mg (Group B, n = 35), meperidine 40 mg (Group C, n = 35), 2% lidocaine 3 mL (Group D, n = 35), or normal saline 3 mL (Group E, n = 35; as placebo control) was given to adult patients. The venous retention of the drug was maintained for 1 min, followed by tourniquet release and I.V. administration of propofol 100 mg. Pain assessment was made immediately after the propofol injection. Lidocaine and meperidine significantly reduced propofol injection pain more than placebo (P < 0.05), but there were more side effects in the meperidine group. Fentanyl and morphine reduced the intensity of propofol injection pain (P < 0.05) and had some effect in reducing the incidence of propofol injection pain, but the difference did not reach statistical significance. The order of efficacy was lidocaine approximately meperidine > morphine approximately fentanyl. We postulate that the peripheral analgesic effect of these opioid is due to their local anesthetic activity.

IMPLICATIONS

Propofol, a commonly used anesthetic, often causes pain on injection. Given as venous retention pretreatments 1 min before propofol, meperidine and lidocaine were found to significantly reduce the propofol injection pain, whereas fentanyl and morphine only slightly reduced the propofol injection pain.