Addition of epidural Clonidine enhances postoperative analgesia: A double-blind study in total knee- replacement surgeries

Co-Evolution of Opioid and Adrenergic Ligands and Receptors: Shared, Complementary Modules Explain Evolution of Functional Interactions and Suggest Novel Engineering Possibilities

Cross-talk between opioid and adrenergic receptors is well-characterized and involves second messenger systems, the formation of receptor heterodimers, and the presence of extracellular allosteric binding regions for the complementary ligand; however, the evolutionary origins of these interactions have not been investigated. We propose that opioid and adrenergic ligands and receptors co-evolved from a common set of modular precursors so that they share binding functions. We demonstrate the plausibility of this hypothesis through a review of experimental evidence for molecularly complementary modules and report unexpected homologies between the two receptor types. Briefly, opioids form homodimers also bind adrenergic compounds; opioids bind to conserved extracellular regions of adrenergic receptors while adrenergic compounds bind to conserved extracellular regions of opioid receptors; opioid-like modules appear in both sets of receptors within key ligand-binding regions. Transmembrane regions associated with homodimerization of each class of receptors are also highly conserved across receptor types and implicated in heterodimerization. This conservation of multiple functional modules suggests opioid–adrenergic ligand and receptor co-evolution and provides mechanisms for explaining the evolution of their crosstalk. These modules also suggest the structure of a primordial receptor, providing clues for engineering receptor functions.

Postoperative Analgesia in Neonates and Infants Using Epidural Chloroprocaine and Clonidine

INTRODUCTION

In neonates and infants, epidural analgesia has gained popularity as a means of providing postoperative analgesia, limiting opioid-related adverse effects and improving the postoperative course. In addition to a local anesthetic agent, adjunctive agents may be added to further augment analgesia. Clonidine is an α2-adrenergic agonist that is frequently added to single-shot caudal analgesia, but there are limited data regarding its use in a continuous epidural infusion, especially in patients ≤12 months of age.

METHODS

We retrospectively reviewed the hospital records of neonates and infants who received postoperative epidural infusions with 2-chloroprocaine, and clonidine was identified over a 4-year period.

RESULTS

The study cohort included 52 neonates and infants ranging in age from 0 to 12 months and in weight from 2.1 to 10.1 kilograms. The catheters were dosed with either 1.5% 2-chloroprocaine (n=47) or 3% 2-chloroprocaine (n=5) with clonidine (median concentration 0.2 µg/mL) infused at a median rate of 0.72 mL/kg/hour. Pain scores were uniformly ≤3 at all evaluation points during the first 72 postoperative hours with a limited need for supplemental systemic opioids. No serious adverse effects were noted.

CONCLUSION

With the recognized limitations of a retrospective study, these preliminary data demonstrate the safety of adding clonidine to an epidural infusion of 2-chloroprocaine in neonates and infants less than 12 months of age. Future studies are needed to determine its analgesic efficacy compared to 2-chloroprocaine alone and the optimal clonidine concentration for postoperative epidural infusions.

Mutual Enhancement of Opioid and Adrenergic Receptors by Combinations of Opioids and Adrenergic Ligands Is Reflected in Molecular Complementarity of Ligands: Drug Development Possibilities

Crosstalk between opioid and adrenergic receptors is well characterized and due to interactions between second messenger systems, formation of receptor heterodimers, and extracellular allosteric binding regions. Both classes of receptors bind both sets of ligands. We propose here that receptor crosstalk may be mirrored in ligand complementarity. We demonstrate that opioids bind to adrenergic compounds with micromolar affinities. Additionally, adrenergic compounds bind with micromolar affinities to extracellular loops of opioid receptors while opioids bind to extracellular loops of adrenergic receptors. Thus, each compound type can bind to the complementary receptor, enhancing the activity of the other compound type through an allosteric mechanism. Screening for ligand complementarity may permit the identification of other mutually-enhancing sets of compounds as well as the design of novel combination drugs or tethered compounds with improved duration and specificity of action.

Adrenergic Agonists Bind to Adrenergic-Receptor-Like Regions of the Mu Opioid Receptor, Enhancing Morphine and Methionine-Enkephalin Binding: A New Approach to "Biased Opioids"?

Extensive evidence demonstrates functional interactions between the adrenergic and opioid systems in a diversity of tissues and organs. While some effects are due to receptor and second messenger cross-talk, recent research has revealed an extracellular, allosteric opioid binding site on adrenergic receptors that enhances adrenergic activity and its duration. The present research addresses whether opioid receptors may have an equivalent extracellular, allosteric adrenergic binding site that has similar enhancing effects on opioid binding. Comparison of adrenergic and opioid receptor sequences revealed that these receptors share very significant regions of similarity, particularly in some of the extracellular and transmembrane regions associated with adrenergic binding in the adrenergic receptors. Five of these shared regions from the mu opioid receptor (muOPR) were synthesized as peptides and tested for binding to adrenergic, opioid and control compounds using ultraviolet spectroscopy. Adrenergic compounds bound to several of these muOPR peptides with low micromolar affinity while acetylcholine, histamine and various adrenergic antagonists did not. Similar studies were then conducted with purified, intact muOPR with similar results. Combinations of epinephrine with methionine enkephalin or morphine increased the binding of both by about half a log unit. These results suggest that muOPR may be allosterically enhanced by adrenergic agonists.

Comparative Evaluation of Ropivacaine and Fentanyl Versus Ropivacaine and Fentanyl with Clonidine for Postoperative Epidural Analgesia in Total Knee Replacement Surgery

Introduction

Clonidine an alpha 2 adrenoceptor agonist possesses analgesic properties and has been used as an adjuvant in epidural analgesia. The addition of clonidine to other analgesics may result in enhanced analgesia through additive mechanisms or synergistic mechanisms. The enhanced analgesia may lead to a decrease in the dosage of analgesic drugs along with reduction of side effects.

Aim

The purpose of this study was to evaluate the effect of adding clonidine to epidural ropivacaine and fentanyl mixture in terms of quality of analgesia and side effects in patients of total knee replacement surgery.

Materials and Methods

A prospective randomised double blind study was conducted on 60 patients of ASA physical status I, II and III who underwent unilateral total knee replacement surgery under combined spinal epidural anaesthesia. Patients were divided into two Groups A and B randomly. Postoperatively Group A received continuous epidural infusion of ropivacaine 2 mg.ml ^-1 and fentanyl 2 μg.ml ^-1 along with clonidine 2 μg.ml^-1 in the range of 3-7 ml.hr^-1 while Group B received the ropivacaine and fentanyl epidural solution. The postoperative VAS scores, haemodynamic parameters, motor block, sedation, nausea, vomiting and any other significant side effects were noted. The two groups were compared with student's t-test, Pearson's Chi square test and t-test using SPSS statistical software.

Results

Visual analog scale scores were lower in Group A (3.38) than in Group B (3.72). The average infusion rate was lower in Group A (4.7 ± 0.7 ml.hr ^-1) than in Group B (5.5 ± 0.7 ml.hr^-1). Patients in Group A required less dosage of rescue pain medication Paracetamol (1g i.v.), diastolic pressure and heart rate were lower in Group A. The groups were comparable in terms of sedation, motor block and nausea vomiting.

Conclusion

Clonidine added to a ropivacaine and fentanyl mixture augmented the postoperative epidural analgesia without significant side effects.

Effect of Clonidine as Adjuvant in Thoracic Paravertebral Block for Patients Undergoing Breast Cancer Surgery: A Prospective, Randomized, Placebo-controlled, Double-blind Study

Background and Aims

Postoperative pain after breast cancer surgery is unavoidable. Thoracic paravertebral block (TPVB), a locoregional anesthetic technique, has been proven successful for postoperative pain management in different thoracic surgical procedures, such as thoracotomy, breast cancer surgeries. Clonidine, an adjuvant, in TPVB may enhance the quality and prolong the duration of analgesia. This prospective study was to evaluate the effectiveness of clonidine; administered with TPVB; in addition to conventional local anesthetic solution.

Materials and Methods

Fifty-two patients (25-55 years) scheduled for breast cancer surgery under general anesthesia were randomly divided into Group A (n = 26) receiving preoperative TPVB at T₃ with clonidine added to local anesthesia solution and Group B (n = 26) receiving identical TPVB with local anesthesia but without any adjuvant. This was followed by balanced general anesthesia. A visual analog scale was used to assess pain postoperatively up to 48 h. Meantime to administration of the first dose of rescue analgesic was noted. Total dose of fentanyl consumption, hemodynamic parameters, and side effects were all recorded for each patient.

Results

The dosage of fentanyl required in the intraoperative period was significantly lower in Group A. Mean time to administration of rescue analgesic was found to be significantly longer in clonidine group. Hemodynamics and side effects were quite comparable among two groups.

Conclusion

Clonidine as adjuvant in TPVB provided profound analgesia for up to 48 h postoperatively for patients undergoing breast cancer surgery without any appreciable side effects.

Evaluation of Efficacy of Epidural Clonidine with 0.5% Bupivacaine for Postoperative Analgesia for Orthopaedic Lower Limb Surgeries

OBJECTIVE

The objective of this study is to evaluate the efficacy of epidural clonidine in intra and postoperative analgesia, the level of sedation caused by clonidine and monitor its side effects.

MATERIALS AND METHODS

Forty patients of ASA1 & ASA2 scheduled for lower limb orthopaediac surgeries were chosen for the study. Study group received 50μg of clonidine diluted to 1ml along with first dose of epidural injection and Control group received 1ml of normal saline along with first dose of epidural. Intra and postoperative vitals, verbal pain rating scale (VRS), sedation score and number of rescue anlgesics required postoperatively were noted. Patients received rescue analgesic when VRS was 1.

RESULTS

Addition of clonidine to bupivacaine definitely improves the quality of analgesia by reducing the overall pain score, prolonging the duration of the time of first rescue analgesia and causing reduction of total analgesic consumption in the postoperative period without any hemodynamic instability. Sedation may be beneficial during the intraoperative period.

CONCLUSION

Epidural clonidine produces long lasting, good quality analgesia with good level of sedation and with minimal side effects.

Comparative study between epidural morphine and bupivacaine with epidural clonidine and bupivacaine for postoperative pain relief in abdominal surgeries

Background:

Many adjuvants are used to increase the efficacy of epidural local anesthetics for postoperative analgesia.

Aims:

The aim was to compare the efficacy of epidural morphine (0.1 mg/kg) and clonidine (2 μg/kg) with bupivacaine (0.125%) for postoperative analgesia in abdominal surgeries.

Settings and Design:

Double-blind retrospective randomized study.

Methodology:

All the patients (n = 60) varying from age group belonging to American Society of Anesthesiologists I–II were randomly allocated to receive epidural analgesia Group A - Morphine (0.1 mg/kg). + Bupivacaine (0.125%) (n = 30), Group B - Clonidine (2 μ/kg) + Bupivacaine (0.125%) (n = 30). We monitored vitals and requirement of inhalational gases intra-operatively, pain by visual analogue score (VAS) and vitals postoperatively. We used rescue analgesics (injection diclofenac 1 mg/kg intravenous) when VAS score > 5. Postoperatively, various parameters were monitored for first 2 h at intervals of 30 min and at 4, 8, 12, 16, and 24 hourly intervals after giving 1^st dose.

Statistical Analysis Used:

Continuous data are analyzed by Student's t-test (paired ‘t’-test for intragroup variations and unpaired ‘t’-test for intergroup variations). Chi-square test was used for categorical data. A P ≤ 0.05 was considered to be statistically significant.

Results:

Mean duration of analgesia was 8.35 ± 0.42 h in Group A (morphine) and 7.45 ± 0.44 h in Group B (clonidine). This difference was statistically significant (P < 0.001), indicating a prolongation of analgesia in group morphine. There was no need of rescue analgesia in any subjects. Group A patients were hemodynamically stable and required less inhalation agents intra-operatively compared to group B patients.

Conclusions:

Epidural morphine plus bupivacaine has a longer duration of analgesia and greater hemodynamic stability as compared to epidural clonidine plus bupivacaine for postoperative analgesia in abdominal surgeries.

A randomized double-blind study to evaluate efficacy and safety of epidural magnesium sulfate and clonidine as adjuvants to bupivacaine for postthoracotomy pain relief

Background:

The aim of the study was to compare postoperative pain relief in patients undergoing an elective thoracotomy with thoracic epidural analgesia using single shot magnesium and clonidine as adjuvants to bupivacaine.

Methods:

In a randomized prospective study, 60 patients of American Society of Anesthesiologists physical status I–III of either sex, between 20 and 60 years undergoing elective unilateral thoracotomy, were allocated to three equal groups of 20 patients. Each patient received thoracic epidural analgesia using bupivacaine alone (Group A) or with magnesium (Group B) or clonidine (Group C) at the end of surgery during skin closure. Postoperatively, pain was measured using a visual analog scale (VAS). Rescue analgesia (50 mg tramadol intravenous) was given at a VAS score of ≥4. Duration of analgesia and total dose of rescue analgesic during 24 h was calculated. Postoperative sedation and other side effects if any were recorded.

Results:

All the groups were homogeneous with respect to their demographics. The 24 h cumulative mean VAS score in Groups A, B, and C was 3.12 ± 0.97, 2.86 ± 0.43, and 1.83 ± 0.59, respectively. The duration of analgesia was prolonged in Group C (165 ± 49.15 min), followed by Group B (138 ± 24.6 min), and Group A (118.5 ± 52.8 min). The duration of analgesia was significantly prolonged in the clonidine group as compared to the control group (P = 0.001). The number of rescue analgesia doses were more in Group A (3.3 ± 1.65) followed by Group B (2.35 ± 0.98) and Group C (1.75 ± 0.71). The sedation scores were significantly higher in Group C. However, shivering was seen in Group A (40%) and Group C (20%) and absent in Group B (P = 0.003).

Conclusion:

Thoracic epidural analgesia using bupivacaine with clonidine is an efficient therapeutic modality for postthoracotomy pain. Magnesium as an adjuvant provided quality postoperative analgesia decreasing the need for postoperative rescue analgesia and incidence of postoperative shivering without causing sedation.