Effect of clonidine and/or fentanyl in combination with intrathecal bupivacaine for lower limb surgery

Biased, Bitopic, Opioid-Adrenergic Tethered Compounds May Improve Specificity, Lower Dosage and Enhance Agonist or Antagonist Function with Reduced Risk of Tolerance and Addiction

This paper proposes the design of combination opioid-adrenergic tethered compounds to enhance efficacy and specificity, lower dosage, increase duration of activity, decrease side effects, and reduce risk of developing tolerance and/or addiction. Combinations of adrenergic and opioid drugs are sometimes used to improve analgesia, decrease opioid doses required to achieve analgesia, and to prolong the duration of analgesia. Recent mechanistic research suggests that these enhanced functions result from an allosteric adrenergic binding site on opioid receptors and, conversely, an allosteric opioid binding site on adrenergic receptors. Dual occupancy of the receptors maintains the receptors in their high affinity, most active states; drops the concentration of ligand required for full activity; and prevents downregulation and internalization of the receptors, thus inhibiting tolerance to the drugs. Activation of both opioid and adrenergic receptors also enhances heterodimerization of the receptors, additionally improving each drug's efficacy. Tethering adrenergic drugs to opioids could produce new drug candidates with highly desirable features. Constraints-such as the locations of the opioid binding sites on adrenergic receptors and adrenergic binding sites on opioid receptors, length of tethers that must govern the design of such novel compounds, and types of tethers-are described and examples of possible structures provided.

Effects of fadolmidine, an α2 -adrenoceptor agonist, as an adjuvant to spinal bupivacaine on antinociception and motor function in rats and dogs

α2 -Adrenoceptor agonists such as clonidine and dexmedetomidine are used as adjuvants to local anesthetics in regional anesthesia. Fadolmidine is an α2 -adrenoceptor agonist developed especially as a spinal analgesic. The current studies investigate the effects of intrathecally administered fadolmidine with a local anesthetic, bupivacaine, on antinociception and motor block in conscious rats and dogs. The antinociceptive effects of intrathecal fadolmidine and bupivacaine alone or in combination were tested in the rat tail-flick and the dog's skin twitch models. The durations of motor block in rats and in dogs were also assessed. In addition, the effects on sedation, mean arterial blood pressure, heart rate, respiratory rate and body temperature were evaluated in telemetrized dogs. Concentrations of fadolmidine in plasma and spinal cord were determined after intrathecal and intravenous administration in rats. Co-administration of intrathecal fadolmidine with bupivacaine increased the magnitude and duration of the antinociceptive effects and prolonged motor block without hypotension. The interaction of the antinociceptive effect was synergistic in its nature in rats. Concentration of fadolmidine in plasma was very low after intrathecal dosing. Taken together, these studies show that fadolmidine as an adjuvant to intrathecal bupivacaine provides enhanced sensory-motor block and enables a reduction of the doses of both drugs. The results indicate that co-administration of fadolmidine with intrathecal bupivacaine was able to achieve an enhanced antinociceptive effect without hypotension and could thus represent a suitable combination for spinal anesthesia.

The efficacy of spinal anaesthesia with fentanyl supplementation for arthroscopic knee surgery: A meta-analysis of randomized controlled studies

INTRODUCTION

The efficacy of spinal anaesthesia with fentanyl supplementation for arthroscopic knee surgery remains controversial. We conducted a systematic review and meta-analysis to explore the influence of fentanyl supplementation for arthroscopic knee surgery.

METHODS

We searched PubMed, Embase, Web of Science, EBSCO and Cochrane Library databases through May 2019 for randomized controlled trials (RCTs) assessing the efficacy and safety of fentanyl supplementation for arthroscopic knee surgery. This meta-analysis is performed using the random-effects model.

RESULTS

Five RCTs are included in the meta-analysis. Overall, compared with the control group for knee arthroscopy, fentanyl supplementation is associated with decreased time for sensory block regression to S1 (mean difference (MD) = -47.38; 95% confidence interval (CI) = -56.74 to -38.02; p < 0.00001), first ambulation (MD = -41.65; 95% CI = -65.11 to -18.19; p = 0.0005), first urination (MD = -23.45; 95% CI = -32.16 to -14.74; p < 0.00001) and hospital discharge (MD = -29.39; 95% CI = -44.73 to -14.06; p = 0.0002) but has no substantial influence on onset time of anaesthesia (MD = 0.50; 95% CI = -1.71 to 2.70; p = 0.66), duration for motor blockade (MD = -42.56; 95% CI = -119.18 to 34.07; p = 0.28), pruritus (risk ratio (RR) = 2.17; 95% CI = 0.28 to 16.90; p = 0.46) or nausea (RR = 0.42; 95% CI = 0.10 to 1.81; p = 0.25).

CONCLUSIONS

Fentanyl supplementation benefits postoperative recovery after knee arthroscopy.

Comparison of bupivacaine plus intrathecal fentanyl and bupivacaine alone for spinal anesthesia with intravenous dexmedetomidine sedation: a randomized, double-blind, noninferiority trial

BACKGROUND AND OBJECTIVES

Fentanyl is widely used as an intrathecal adjuvant to local anesthetics to enhance the duration of spinal anesthesia. Recent evidence suggests that intravenous dexmedetomidine prolongs the duration of spinal anesthesia. This noninferiority study evaluated whether bupivacaine alone could provide a noninferior duration of block compared with bupivacaine and fentanyl when intravenous dexmedetomidine was administered intraoperatively.

METHODS

Fifty-six patients scheduled for total knee arthroplasty under spinal anesthesia were randomly allocated to receive either bupivacaine 13 mg with intrathecal fentanyl 20 µg (Group BF) or bupivacaine 13 mg (Group B). Both groups underwent intravenous dexmedetomidine sedation throughout the surgery (1 µg kg^-1 for 10 min, followed by 0.5 µg kg^-1 h^-1). The primary outcome was the time to two-segment regression of the sensory block. The noninferiority margin for the mean difference was predefined as -10 min. Secondary outcomes included postoperative pain scores, analgesics consumptions, and the incidences of pruritus, nausea, and vomiting.

RESULTS

There was no significant difference in the two-segment regression time of sensory block (Group B 109.1±25.0 min vs Group BF 104.3±25.9 min; p=0.484). The mean difference in the two-segment regression time between the 2 groups was 4.8 min (95 % CI -8.9 to 18.6), demonstrating the noninferiority of bupivacaine alone. Secondary outcomes showed no significant differences between the two groups.

CONCLUSIONS

The duration of spinal anesthesia with bupivacaine alone is noninferior to that of bupivacaine plus fentanyl in patients receiving intravenous dexmedetomidine intraoperatively. Our results suggest that intrathecal fentanyl may not be required when intravenous dexmedetomidine is administered.

TRIAL REGISTRATION NUMBER

NCT03105115.

Use of intrathecal midazolam or fentanyl as an adjunct to spinal anaesthesia with bupivacaine for lower limb surgery: A randomised controlled study

Background

Intrathecal adjuncts have been used to prolong the quality and duration of subarachnoid anaesthesia. Midazolam given intrathecally is reported to have antinociceptive properties. The purpose of this study was to compare intrathecal midazolam with fentanyl for pain relief and patient comfort.

Methods

In this prospective, double-blind, randomised controlled trial, 90 patients for lower limb surgeries were randomly allocated to three groups: "control group" (3 ml 0.5% heavy bupivacaine), "fentanyl group" (3 ml 0.5% bupivacaine + 10 mcg fentanyl) and "midazolam group" (3 ml 0.5% bupivacaine + 1 mg midazolam). Level, duration, and quality of blocks were compared along with the duration and quality of postoperative analgesia. Haemodynamic stability and any associated complications were also noted.

Results

Onset of block was fastest in Group C (28.5 ± 13.48 min) vis-a-vis other groups (35.5 ± 26.05 min for Group "F" and 28.5 ± 23.68 min for Group "M"; P = 0.51). Duration of block was comparable in all groups (130.5 ± 39.3 min Group "C"; 126.5 ± 44.0 min Group "F" and 129.5 ± 45.7 min Group "M"; P > 0.5).Addition of adjuncts did not significantly defer the appearance of pain. Intensity of pain was lower in Group "M". Average VAS scores were lower for Group "M" (3-4) than those for Group "C" (4-5) and Group "F" (4-6).Majority of patients required at least one dose of rescue analgesic; however, those receiving fentanyl reported better quality of postoperative analgesia than those in midazolam group.

Conclusion

Adjuvants improve quality of postoperative analgesia (fentanyl better than midazolam).

A comparative study of dexmedetomidine and fentanyl as adjuvants to levobupivacaine for caudal analgesia in children undergoing lower limb orthopedic surgery

Background:

Levobupivacaine is an effective local anesthetic agent with less systemic toxicity than racemic bupivacaine, but it has short postoperative analgesic duration. Dexmedetomidine and fentanyl are promising adjuncts to provide excellent and prolonged postoperative caudal analgesia. This study compared the effects of caudal levobupivacaine plus dexmedetomidine and levobupivacaine plus fentanyl for postoperative analgesia and sedation in children undergoing lower limb orthopedic surgery.

Patients and Methods:

Ninety children, whose age ranged from 1 to 7 years, American Society of Anesthesiologists I-II, undergoing orthopedic lower limb surgery under general anesthesia received caudal block for postoperative analgesia. The children were randomly allocated into three groups: Group L (control) received 0.75 ml/kg levobupivacaine 0.25% diluted in saline; Group LD received 0.75 ml/kg levobupivacaine 0.25% with dexmedetomidine 1 μg/kg; and Group LF received 0.75 ml/kg levobupivacaine 0.25% with fentanyl 1 μg/kg. Following the administration of the drugs; hemodynamic variables, the total anesthesia time, sedation score, Face, Legs, Activity, Cry, Consolability score, duration of analgesia, and side effects were recorded.

Results:

Demographically, all the groups were comparable, both the baseline and the intraoperative hemodynamic profile were similar in all groups. The mean duration of analgesia and the mean sedation score in the Group LD were significantly greater as compared to both the other groups.

Conclusion:

Dexmedetomidine may be a better additive to levobupivacaine than fentanyl for caudal postoperative analgesia, arousable sedation with comparable hemodynamic and side effect profile in children.