Dexmedetomidine injection into the locus ceruleus produces antinociception

The value of local dexmedetomidine as an adjuvant to ultrasound-guided wide awake local anesthesia no tourniquet (WALANT) in flexor tendon repair surgeries: a randomized controlled trial

BACKGROUND

The Wide-Awake Local Anesthesia No Tourniquet (WALANT) technique allows intraoperative motor assessment of tendon repair integrity of the hand compared with general anesthesia or brachial plexus block. No studies have tested the effect of adding dexmedetomidine to lidocaine on the analgesic properties of the WALANT technique, which is the aim of our study.

METHODS

A total of 128 patients aged more than 18 years were scheduled for surgical flexor tendon injury repair using WALANT technique. Patients were divided into two equal groups. Ultrasound-guided subcutaneous injection of lidocaine 1% with dexmedetomidine (1 µg/kg), Group D, or without dexmedetomidine, Group C, was performed at four points: proximal to the wrist joint, the distal forearm, palm region, and proximal phalanges. The primary outcome was total morphine consumption throughout the first postoperative day. Secondary outcomes included number of patients requiring rescue analgesia, time to first analgesic request, and pain score.

RESULTS

Total morphine consumption was significantly (P < 0.001) lower in group D (2.66 ± 0.998) than in group C (3.66 ± 1.144) mg. Number of patients requiring rescue analgesia was significantly (P < 0.001) lower in group D (54.7% (35)) than group C (100.0% (64)). The time for first request for analgesia was significantly (P < 0.001) longer in group D (11.31 ± 6.944) than in group C (5.91 ± 4.839) h. Pain score was significantly higher in group C than D at three (P < 0.001), and six (P = 0.001) hours (P = 0.001) postoperatively.

CONCLUSION

Dexmedetomidine significantly improves the analgesic quality of WALANT when added to lidocaine with less opioid consumption.

TRIAL REGISTRATION

(ID: PACTR202203906027106; Date: 31/07/2023).

Enhancing fentanyl antinociception and preventing tolerance with α-2 adrenoceptor agonists in rats

Fentanyl (FEN) is a potent opioid analgesic used for pain management. Opioid analgesic tolerance poses a significant challenge to the clinical utility of opioid agonists. Preventing the development of tolerance to opioid analgesia is crucial for improving its efficacy and safety. The noradrenergic system is involved in pain regulation. This study examined the effects of α-2 adrenoceptor (AR) agonists, dexmedetomidine (DEX), and xylazine (XYL) on FEN tolerance and antinociception, and their impact on μ-opioid receptor (MOR) expression in the posterior horn of the spinal cord (SC). Male rats were divided into six groups and treated with different drug combinations for three consecutive days. Analgesia tests and motor performance assessments were conducted, followed by SC analysis using immunohistochemistry (IHC). Analgesia tests revealed the development of FEN tolerance on the second day, but the groups receiving combined drugs did not develop tolerance. Instead, FEN antinociception was enhanced, with a prolonged duration of its effects. None of the drugs caused sedation or motor impairment, and SC morphology appeared normal. MOR expression levels did not differ significantly between the groups based on IHC analysis. These findings suggest that changes in the secondary messenger system may play a role in the early development of FEN tolerance. Combining drugs can prevent tolerance, while enhancing FEN's antinociceptive effects. These results have promising implications for chronic pain management; however, further research is needed to explore the molecular effects of α-2 AR agonists on FEN tolerance. Overall, this study sheds light on the mechanism of FEN tolerance and identifies potential avenues for future research.

Dexmedetomidine modulates neuronal activity of horizontal limbs of diagonal band via α2 adrenergic receptor in mice

BACKGROUND AND OBJECTIVES

Dexmedetomidine (DEX) is widely used in clinical sedation which has little effect on cardiopulmonary inhibition, however the mechanism remains to be elucidated. The basal forebrain (BF) is a key nucleus that controls sleep-wake cycle. The horizontal limbs of diagonal bundle (HDB) is one subregions of the BF. The purpose of this study was to examine whether the possible mechanism of DEX is through the α2 adrenergic receptor of BF (HDB).

METHODS

In this study, we investigated the effects of DEX on the BF (HDB) by using whole cell patch clamp recordings. The threshold stimulus intensity, the inter-spike-intervals (ISIs) and the frequency of action potential firing in the BF (HDB) neurons were recorded by application of DEX (2 µM) and co-application of a α2 adrenergic receptor antagonist phentolamine (PHEN) (10 µM).

RESULTS

DEX (2 µM) increased the threshold stimulus intensity, inhibited the frequency of action potential firing and enlarged the inter-spike-interval (ISI) in the BF (HDB) neurons. These effects were reversed by co-application of PHEN (10 µM).

CONCLUSION

Taken together, our findings revealed DEX decreased the discharge activity of BF (HDB) neuron via α2 adrenergic receptors.

Effect of opioid-free anesthesia on the incidence of postoperative nausea and vomiting: A meta-analysis of randomized controlled studies

BACKGROUND

Research on opioid-free anesthesia has increased in recent years; however, it has never been determined whether it is more beneficial than opioid anesthesia. This meta-analysis was primarily used to assess the effect of opioid-free anesthesia compared with opioid anesthesia on the incidence of postoperative nausea and vomiting.

METHODS

We searched the electronic databases of PubMed, the Cochrane Library, Web of Science and Embase from 2014 to 2022 to identify relevant articles and extract relevant data. The incidence of postoperative nausea and vomiting, time to extubation, pain score at 24 hours postoperatively, and time to first postoperative rescue analgesia were compared between patients receiving opioid-free anesthesia and those receiving standard opioid anesthesia. Differences in the incidence of postoperative nausea and vomiting were evaluated using risk ratios (95% confidence interval [CI]). The significance of the differences was assessed using mean differences and 95% CI. The heterogeneity of the subject trials was evaluated using the I2 test. Statistical analysis was performed using the RevMan 5.4 software.

RESULTS

Fourteen randomized controlled trials, including 1354 participants, were evaluated in the meta-analysis. As seen in the forest plot, the OFA group had a lower risk of postoperative nausea and vomiting than the control group (risk ratios = 0.41, 95% CI: 0.33-0.51, P < .00001; n = 1354), and the meta-analysis also found that the OFA group had lower postoperative analgesia scores at 24 hours (P < .000001), but time to extubation (P = .14) and first postoperative resuscitation analgesia time (P < .54) were not significantly different.

CONCLUSIONS

Opioid-free anesthesia reduces the incidence of postoperative nausea and vomiting while providing adequate analgesia without interfering with postoperative awakening.

Dexmedetomidine as an Adjuvant in Peripheral Nerve Block

Peripheral nerve block technology is important to balanced anesthesia technology. It can effectively reduce opioid usage. It is the key to enhance clinical rehabilitation as an important part of the multimodal analgesia scheme. The emergence of ultrasound technology has accelerated peripheral nerve block technology development. It can directly observe the nerve shape, surrounding tissue, and diffusion path of drugs. It can also reduce the dosage of local anesthetics by improving positioning accuracy while enhancing the block's efficacy. Dexmedetomidine is a highly selective drug α₂-adrenergic receptor agonist. Dexmedetomidine has the characteristics of sedation, analgesia, anti-anxiety, inhibition of sympathetic activity, mild respiratory inhibition, and stable hemodynamics. Numerous studies have revealed that dexmedetomidine in peripheral nerve blocks can shorten the onset time of anesthesia and prolong the time of sensory and motor nerve blocks. Although dexmedetomidine was approved by the European Drug Administration for sedation and analgesia in 2017, it has not yet been approved by the US Food and Drug Administration (FDA). It is used as a non-label drug as an adjuvant. Therefore, the risk-benefit ratio must be evaluated when using these drugs as adjuvants. This review explains the pharmacology and mechanism of dexmedetomidine, the effect of dexmedetomidine on various peripheral nerve block as an adjuvant, and compare it with other types of adjuvants. We summarized and reviewed the application progress of dexmedetomidine as an adjuvant in nerve block and look forward to its future research direction.

A prospective, randomized, triple-blind comparative study of ropivacaine-dexmedetomidine versus ropivacaine alone in peribulbar blocks

Background and Aims

Bupivacaine and lidocaine mixtures are the commonly used local anesthetic drugs for the peribulbar blocks. Because of its safe anesthetic profile, ropivacaine is being investigated as an alternative agent. Several centers have evaluated the effect of the addition of an adjuvant like dexmedetomidine (DMT) to ropivacaine in enhancing the block characteristics. We proposed to evaluate the effect of the addition of DMT to ropivacaine versus a control group not having DMT as adjuvant.

Material and Methods

A prospective, randomized comparative study was conducted on a total of 80 patients attending our hospital for cataract surgeries. Patients were allocated into four groups of 20 each (n = 20) and peribulbar blocks were given 6 mL of 0.75% ropivacaine in group R and 6 mL of 0.75% ropivacaine plus 10 μg, 15 μg, and 20 μg DMT, respectively, in groups RD1, RD2, and RD3.

Results

When DMT was used as an adjunct to ropivacaine, there was a prolongation of the duration of the sensory block.

Conclusion

In peribulbar blocks, 6 mL of ropivacaine 0.75% produces satisfactory block characteristics, and the addition of 10 μg, 15 μg, or 20 μg of DMT as an adjuvant to ropivacaine 0.75% had the effect of significantly prolonging the duration of the sensory block, which is directly proportional to the dose of DMT employed. However, 20 μg of DMT added as an adjuvant to ropivacaine 0.75% appears to be the optimal dose, as this anesthetic drug mixture provides maximum prolongation of the sensory block besides providing satisfactory operating conditions, acceptable sedation levels, and stable hemodynamic parameters.

Evidence basis for using dexmedetomidine to enhance the quality of paravertebral block: A systematic review and meta-analysis of randomized controlled trials

Background: Dexmedetomidine is considered an adjunct to local anaesthesia (LA) to prolong peripheral nerve block time. However, the results from a previous meta-analysis were not sufficient to support its use in paravertebral block (PVB). Therefore, we performed an updated meta-analysis to evaluate the efficacy of dexmedetomidine combined with LA in PVB.

Methods: We performed an electronic database search from the date of establishment to April 2022. Randomized controlled trials (RCTs) investigating the combination of dexmedetomidine and LA compared with LA alone for PVB in adult patients were included. Postoperative pain scores, analgesic consumption, and adverse reactions were analyzed.

Results: We identified 12 trials (701 patients) and found that the application of dexmedetomidine as a PVB adjunct reduced the postoperative pain severity of patients 12 and 24 h after surgery compared to a control group. Expressed as mean difference (MD) (95% CI), the results were −1.03 (−1.18, −0.88) (p < 0.00001, I² = 79%) for 12 h and −1.08 (−1.24, −0.92) (p < 0.00001, I² = 72%) for 24 h. Dexmedetomidine prolonged the duration of analgesia by at least 173.27 min (115.61, 230.93) (p < 0.00001, I² = 81%) and reduced postoperative oral morphine consumption by 18.01 mg (−22.10, 13.92) (p < 0.00001, I² = 19%). We also found no statistically significant differences in hemodynamic complications between the two groups. According to the GRADE system, we found that the level of evidence for postoperative pain scores at 12 and 24 h was rated as moderate.

Conclusion: Our study shows that dexmedetomidine as an adjunct to LA improves the postoperative pain severity of patients after surgery and prolongs the duration of analgesia in PVB without increasing the incidence of adverse effects.

Effect of oxytocin pretreatment on the development of morphine tolerance and dependence in rats

Increased opioid synthesis and release, and enhanced alpha-2 adrenoceptor signaling have been suggested to mediate repeated oxytocin-induced long-lasting effects including elevated pain threshold in rats. This study evaluated whether oxytocin pretreatment would influence development of dependence and tolerance to the nociceptive and body temperature responses to morphine and enhance effects of alpha-2 adrenergic agonist clonidine on nociceptive threshold, body temperature and morphine withdrawal signs. Rats injected subcutaneously with saline or 1 mg/kg oxytocin for 5 days were implanted with placebo or morphine pellets 24 h after the treatment period. Body temperature and nociception were assessed, with nociception determined via by hot plate and tail immersion tests, before and 4, 24 and 48 h after pellet implantation, and following a challenge dose of morphine. Withdrawal signs were determined after naloxone administration. Oxytocin produced analgesia, as evidenced by increased paw withdrawal latency in the hot plate test. Morphine increased body temperature and nociceptive threshold which declined over time. Morphine challenge could not demonstrate tolerance to the body temperature response. Analgesic tolerance was observed in the hot plate test in saline and in both tests in oxytocin pretreated rats. Naloxone-precipitated withdrawal appeared to be less severe in oxytocin pretreatment. Clonidine was ineffective on the withdrawal signs but decreased body temperature and increased tail flick latency in the tail immersion test in oxytocin pretreated animals. These results, while producing evidence for a hyperresponsiveness in alpha-2 adrenoceptors, provide contrasting effects on morphine tolerance and dependence, and their partial mediation by opioidergic and adrenergic activation in repeated oxytocin treatment.

The Role of Dexmedetomidine in Tumor-Progressive Factors in the Perioperative Period and Cancer Recurrence: A Narrative Review

Dexmedetomidine, a specific α2 adrenergic receptor agonist, is highly frequently used in the perioperatively for its favorable pharmacology, such as mitigating postoperative cognitive dysfunction. Increasing attention has been recently focused on the effect of whether dexmedetomidine influences cancer recurrence, which urges the discussion of the role of dexmedetomidine in tumor-progressive factors. The pharmacologic characteristics of dexmedetomidine, the tumor-progressive factors in the perioperative period, and the relationships between dexmedetomidine and tumor-progressive factors were described in this review. Available evidence suggests that dexmedetomidine could reduce the degree of immune function suppression, such as keeping the number of CD3+ cells, NK cells, CD4+/CD8+ ratio, and Th1/Th2 ratio stable and decreasing the level of proinflammatory cytokine (interleukin 6 and tumor necrosis factor-alpha) during cancer operations. However, dexmedetomidine exhibits different roles in cell biological behavior depending on cancer cell types. The conclusions on whether dexmedetomidine would influence cancer recurrence could not be currently drawn for the lack of strong clinical evidence. Therefore, this is still a new area that needs further exploration.

Dexmedetomidine prolongs the duration of local anesthetics when used as an adjuvant through both perineural and systemic mechanisms: a prospective randomized double-blinded trial

Background

To study the respective peripheral and systemic mechanisms of action of dexmedetomidine, as adjuvant to regional anesthesia, we compared dexmedetomidine added to ropivacaine for mid-forearm nerve blocks, to either systemic-only dexmedetomidine, and to a control with no dexmedetomidine.

Methods

Sixty patients undergoing hand surgery were randomly divided into three groups (n = 20 per group). Each group underwent a triple-nerve (median, radial and ulnar) mid-forearm blocks with 0.75% ropivacaine. In the DexP group, 60 µg of dexmedetomidine were added to the anesthetic mixture, while in the DexIV group, they were intravenously infused. Normal saline as a placebo was used, either as adjuvant, or intravenously. All patients underwent also a supraclavicular block with 1.5% lidocaine for tourniquet pain. The main outcomes were the duration of analgesia and the duration of sensory blockade separately for each nerve termination of the upper limb, and the duration of motor blockade of the upper limb. Tolerance was assessed by blood pressure and heart rate, and the report of adverse events.

Results

Duration of analgesia was longer in the DexP group, in comparison to the two other groups (P < 0.001), while it was similar in the DexIV and the control group. For cutaneous territories targeted by the three mid-forearm blocks, the between-group differences behaved similarly. For the other cutaneous territories (musculocutaneous and posterior brachial cutaneous nerves), duration of sensory blockade was shorter in the control group than in the two dexmedetomidine groups. For duration of motor blockade, the between-group differences behaved similarly. Both blood pressure and heart rate were reduced in the DexP and the DexIV groups, compared to the control.

Conclusions

Dexmedetomidine used as an adjuvant to regional anesthesia may act mostly though a perineural mechanism, especially for the sensory aspects of anesthesia. A systemic action might however explain other clinical effects.

Trial registration

ChiCTR-IOR-17011149, date of registration: 16/04/2017

Comparison of the effects of dexmedetomidine and remifentanil on perioperative hemodynamics and recovery profile of patients undergoing laryngeal microsurgery: A prospective randomized double-blinded study

BACKGROUND

Laryngeal microsurgery (LMS) causes hemodynamic instability and postoperative agitation, cough, pain, nausea, and vomiting. Moreover, because of a short operation time, it is associated with challenging anesthetic management. The aim of this study was to compare the usefulness of continuous administration of dexmedetomidine and remifentanil in inducing general anesthesia in patients undergoing LMS.

METHODS

This is a prospective randomized control design. Continuous intravenous infusion of dexmedetomidine (group D) or remifentanil (group R) was administered from 10 minutes before the induction of anesthesia to the end of surgery. In both groups, 1.5 mg/kg propofol and 0.5 mg/kg rocuronium were administered for the induction of anesthesia, and desflurane were titrated during the measurement of the bispectral index. We recorded hemodynamic data, recovery time, grade of cough, pain score, and analgesic requirements during the perioperative period.

RESULTS

61 patients were finally analyzed (30 for group D, 31 for group R). The incidence of moderate to severe postoperative sore throat was higher in group R than in group D (42% vs 10%, P = .008), and the quantity of rescue fentanyl used in post-anesthesia care unit was significantly higher in group R than in group D (23.2 ± 24.7 mg vs 3.3 ± 8.6 mg; P < .001); however, the time required for eye opening was significantly longer in group D than in group R (599.4 ± 177.9 seconds vs 493.5 ± 103.6 seconds; P = .006). The proportion of patients with no cough or single cough during extubation was comparable between the 2 groups (group D vs group R: 73% vs 70%) as was the incidence of hemodynamic instability.

CONCLUSION

Although there was a transient delay in emergence time, dexmedetomidine reduced postoperative opioid use and the incidence of sore throat. Dexmedetomidine may be used as an alternative agent to opioids in patients undergoing LMS.

Comparing the effects of dexmedetomidine and dexamethasone as perineural adjuvants on peripheral nerve block: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

Dexmedetomidine (Dexm), a selective alpha-2 adrenoceptor agonist, and dexamethasone (Dexa), a very potent and highly selective glucocorticoid, have both been proven effectively to prolong the duration of local anesthetics (LA) in regional anesthesia. However, data comparing the efficacy of Dexm and Dexa as perineural adjuvants are inconsistent. Therefore, this systematic review and meta-analysis of randomized and quasi-randomized controlled trials (RCTs) was conducted to compare the effects of Dexm and Dexa when used as LA adjuvants on peripheral nerve block (PNB).

METHODS

We systematically searched PubMed, Cochrane Library, EMBASE, Web of Science, and ScienceDirect databases up to October, 2020. The primary outcome was the duration of analgesia. Secondary outcomes included incidence of rescue analgesia, cumulative opioid consumption, time required for onset of sensory and motor blockades, duration of sensory and motor blockades, incidence of postoperative nausea and vomiting (PONV), and side effect-associated outcomes (e.g., bradycardia, sedation, hypotension, rates of infection, and neurological complications). The study was registered on PROSPERO, number CRD42020188796.

RESULTS

After screening of full-text relevant articles, 13 RCTs that met the inclusion criteria were retrieved for this systematic review. It was revealed that perineural Dexm provided equivalent analgesic duration to perineural Dexa. Besides, the intake of Dexm increased the incidence of rescue analgesia in limbs surgery, as well as the cumulative opioid consumption, and decreased the time required for onset of sensory and motor blockades for long-acting LA (all P < .05). Other analysis revealed insignificant difference between the 2 groups in terms of the incidence of PONV (P > .05). Additionally, 2 studies demonstrated that Dexm possesses more sedative properties than Dexa (P < .05).

CONCLUSIONS

This meta-analysis indicated that the analgesic duration of Dexm and Dexa as LA adjuvants in PNB is the same. Meanwhile, the effects of perineural Dexm and Dexa on some secondary outcomes, including the incidence of rescue analgesia, cumulative opioid consumption, and time required for onset of sensory and motor blockades, are associated with the surgical site and type of LA.

Effect of Intravenous Dexmedetomidine on Spinal Anesthesia

Background

Subarachnoid block (SAB) with hyperbaric bupivacaine is routinely administered for abdominal and lower limb surgeries. Various agents have been used intrathecally as adjuvants to local anesthetic to increase efficacy and prolong the duration of SAB, among which opioids and α2 agonists are most commonly used. Intravenously administered dexmedetomidine has also been shown to prolong the duration of sensory and motor blockade obtained with subarachnoid block.

Methods

A total of 212 adult patients scheduled to undergo abdominal or lower limb surgeries were enrolled in this prospective, double-blind, randomized study. They were divided into two equal groups to receive either intravenous dexmedetomidine (group D) 1μg/kg loading followed by maintenance at 0.5μg/kg or intravenous normal saline (group C) after 15 mins of subarachnoid block; no other intraoperative sedatives were used. The onset of sensory block and motor block, and the highest level of sensory block attained were assessed. The time taken for sensory regression to L1, Modified Bromage scale 0, and rescue analgesia requirement were assessed.

Results

Patients receiving intravenous dexmedetomidine showed no significant change in terms of onset and level of sensory block (P-0.774) and the onset of motor block (P-0.738). The time taken for sensory regression to L1 was significantly prolonged (P-0.000). Also, the time taken to achieve Modified Bromage scale of 0 and time taken for rescue analgesia was significantly prolonged (P-0.000).

Conclusion

Intravenous dexmedetomidine prolonged the duration of sensory and motor block, and also appears to provide sedation with easy arousability and analgesia postoperatively while maintaining hemodynamic stability with no significant side effects.

Efficacy of dexmedetomidine on peritoneal dialysis catheter insertion

PURPOSE

Dexmedetomidine (DEX) is a sedative agent with minimal respiratory and hemodynamic effects. The present study aimed to evaluate its effectiveness in peritoneal dialysis (PD) catheter insertion.

METHODS

This single-center retrospective study included patients who underwent PD catheter insertion under spinal anesthesia in our hospital between January 2016 and December 2020. Patients were divided into the DEX and non-DEX groups according the use of DEX. After 1:1 propensity score matching to adjust for age, sex, body mass index, mean blood pressure (BP), and Charlson comorbidity index, we compared operation-related outcomes, including peak numerical rating scale (NRS), occurrence of nausea, vital signs, or operative time between the two groups.

RESULTS

Of a total of 44 patients, 9 patients received DEX, and 35 did not. After propensity score matching, each group consisted of 8 patients. Peak NRS was significantly lower (P = 0.003) in the DEX group compared with the non-DEX group. Maximum mean BP during the operation was also significantly lower in the DEX group compared with the non-DEX group (P = 0.020), with no significant differences in minimum mean BP between the two groups (P = 0.831). The DEX group showed a trend of shortened operative time (P = 0.068). There were no significant differences in the occurrence of nausea (P = 1.000). Moreover, there was no clinically important adverse event associated with use of DEX.

CONCLUSION

The use of DEX in PD catheter insertion under spinal anesthesia could safely improve operative analgesia.

Evaluation of analgesic interaction between morphine, maropitant and dexmedetomidine in dogs undergoing ovariohysterectomy

ABSTRACTAims: To compare the analgesic effect of morphine combined with maropitant and/or dexmedetomidine to morphine alone but at a higher dose, and to evaluate the pharmacokinetics of the drug combinations, in dogs undergoing ovariohysterectomy (OHE).Methods: Forty client-owned dogs were randomised into four treatment groups (n = 10 per group) each to receive a different analgesic protocol. After premedication with I/M acepromazine, anaesthesia was induced with propofol to effect and maintained with isoflurane in 100% oxygen delivered via a circle system. The heart rate, respiratory rate, blood pressure, haemoglobin oxygen saturation, end-tidal partial pressure of carbon dioxide, electrocardiogram and rectal temperature were monitored during anaesthesia. The test drugs (Mor: 0.6 mg/kg morphine; Maro + Mor: 0.3 mg/kg morphine and 1 mg/kg maropitant; Dex + Mor: 0.3 mg/kg morphine and 10 μg/kg dexmedetomidine; Dex + Maro + Mor: 0.2 mg/kg morphine, 7 μg/kg dexmedetomidine and 0.7 mg/kg maropitant) were administered I/M after induction of anaesthesia and 30 minutes before the expected start time of ovariohysterectomy, which was carried out by veterinary students under veterinary supervision. The short form of the Glasgow composite measure pain scale (CMPS-SF) and visual analogue scale (VAS) were used for pain assessment at 15 and 30 minutes and 1, 2, 3, 6, 9 and 24 hours after extubation. Dogs with CMPS-SF pain score ≥ 6 received rescue analgesia with S/C buprenorphine (0.02 mg/kg). Blood samples were collected before, 15, 30, 60 and 120 minutes after injection of the test drugs and concentration of the test drugs in plasma was determined by liquid chromatography-mass spectrometry.Results: Dogs that received Dex + Mor had significantly lower CMPS-SF (estimate of difference = -1.53 (SE 0.58); p = 0.010) and VAS (estimate of difference = -0.67 (SE 0.25); p = 0.007) scores compared to the dogs that received morphine alone. There was no evidence of a difference in the number of dogs requiring rescue between groups. All dogs that received dexmedetomidine showed cardiac arrhythmia and second-degree heart block. Mean (SD) maximum concentrations (C_max,) of morphine in plasma were 6.8 (4.56), 9.56 (8.29), 9.30 (3.35) and 18.99 (9.41) ng/mL for the groups Dex + Mor, Dex + Maro + Mor, Maro + Mor and Mor respectively. The C_max of morphine was significantly lower in the Dex + Mor (p = 0.004), Dex + Maro + Mor (p = 0.034) and Maro + Mor (p = 0.018) groups compared to the Mor group.Conclusions For dogs undergoing ovariohysterectomy, lower doses of morphine (0.2 and 0.3 mg/kg) combined with dexmedetomidine or maropitant may provide analgesia equivalent to or better than morphine when given alone at a higher dose (0.6 mg/kg).Abbreviations: AUC: Area under curve; C_max: Maximum concentration in plasma; CMPS-SF: Glasgow composite measure pain scale - short form; NK1: Neurokinin-1; OHE: Ovariohysterectomy; T_max: Time to C_max; T_1/2: Half-life of terminal elimination phase; VAS: Visual analogue scale.

Ultrasound-Guided Suprainguinal Fascia Iliaca Compartment Block for Postoperative Analgesia in Patients Undergoing Hip and Femur Surgeries: A Retrospective Analysis

Context:

Fractures of femur and hip surgeries pose a challenge because of excruciating pain. Fascia iliaca compartment block is an effective and easily learned procedure to decrease postoperative pain score and dosage of opioid. Many adjuvants are combined with local anesthetics to prolong the postoperative analgesia.

Aims:

The aim was to study duration of postoperative analgesia in terms of Numeric Rating Scale (NRS), number of times rescue analgesic used, any adverse effect, and patient satisfaction score.

Settings and Design:

Operation theatre of Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow.

Materials and Methods:

The present study was retrospective study with 203 patients evaluated. Based on the combination of the anesthesia and drugs, study patients were divided into six groups. Pain scores were assessed at 6 hourly intervals for 24 h.

Statistical Analysis Used:

Kruskal–Wallis H-test used to compare NRS as well as age and duration of anesthesia. Chi-square test/Fisher's exact test used to compare the proportions.

Results:

Postoperative analgesia was comparable and insignificant (P > 0.05) at 0, 6, 12 h in all six groups. Better postoperative analgesia was observed with dexmedetomidine and dexamethasone as adjuvant at 18 h, dexmedetomidine as adjuvant in comparison to dexamethasone as adjuvant at 24 h. Rescue analgesia in postoperative period was required maximum in plain bupivacaine. Satisfaction levels were good and excellent in dexmedetomidine and dexamethasone as adjuvant.

Conclusions:

Addition of dexmedetomidine to bupivacaine provides longer duration, good quality postoperative analgesia, reduced requirement for rescue analgesic, lesser postoperative nausea and vomiting, and better satisfaction levels.

Perineural Dexmedetomidine Reduces the Median Effective Concentration of Ropivacaine for Adductor Canal Block

BACKGROUND Multimodal analgesic regimens are well known as the best option for total knee arthroplasty. They include the adductor canal block, combined with local infiltration analgesia and a block of the interspace between the popliteal artery and the capsule of the posterior knee. However, these analgesic techniques all require a large amount of local anesthetics. In this study, we explored whether the quantity of local anesthetics could be decreased by using dexmedetomidine for the adductor canal block. MATERIAL AND METHODS Fifty-four patients scheduled for unilateral, primary total knee arthroplasty were allocated into 2 groups: the ropivacaine group (group R) and the dexmedetomidine group (group RD). Ropivacaine 0.5% was chosen as the initial concentration, and the concentration was decreased or increased according to the response of the previous participant. Based on Dixon's up-and-down method, the median effective concentration was calculated. RESULTS The quadriceps strength was similar between the 2 groups, both at 30 min after adductor canal block and during recovery from general anesthesia in the Postanesthesia Care Unit. None of the patients in this study exhibited bradycardia or hypotension. The median effective concentration of ropivacaine for adductor canal block was 0.29% (95% confidence interval [CI], 0.28-0.31%) in group RD, which was lower than that in group R (0.38% [95% CI, 0.36-0.41%]). CONCLUSIONS This study found perineural dexmedetomidine 1 μg/kg could reduce the median effective concentration of ropivacaine for the adductor canal block.

Paravertebral block using levobupivacaine or dexmedetomidine-levobupivacaine for analgesia after cholecystectomy: a randomized double-blind trial

Background

Thoracic paravertebral block (TPVB) has emerged as an effective and feasible mode of providing analgesia in laparoscopic cholecystectomy. Though a variety of local anaesthetic combinations are used for providing TPVB, literature is sparse on use of dexmedetomidine in TPVB. We aimed to compare levobupivacaine and levobupivacaine-dexmedetomidine combination in ultrasound guided TPVB in patients undergoing laparoscopic cholecystectomy.

Methodology

70 ASA I/II patients, aged 18–60 years, scheduled to undergo laparoscopic cholecystectomy under general anaesthesia were enrolled and divided into two groups. Before anaesthesia induction, group A patients received unilateral right sided ultrasound guided TPVB with 15 ml 0.25% levobupivacaine plus 2 ml normal saline while group B patients received unilateral right sided ultrasound guided TPVB with 15 ml 0.25% levobupivacaine plus 2 ml solution containing dexmedetomidine 1 μg.kg^-1. Patients were monitored for pain using Numeric Rating Scale (NRS) at rest, on movement, coughing and comfort scores post surgery. Total analgesic consumption in first 48 hour postoperative period, time to first request analgesic and pain scores were recorded.

Results

Total amount of rescue analgesia (injection tramadol plus injection tramadol intravenous equivalent dose) consumed during 48 hours postoperatively in group A was 146.55 mg while in group B was 111.30 mg (p = 0.026). Mean time for demanding rescue analgesia was 273 minutes in group A while in group B was 340 minutes (p = 0.00).

Conclusion

TPVB using dexmedetomidine 1 μg.kg^-1 added to levobupivacaine 0.25% in patients undergoing laparoscopic cholecystectomy significantly reduced total analgesic consumption in first 48 hours and provided longer duration of analgesia postoperatively compared to levobupivacaine 0.25% alone.

Dexmedetomidine as an Adjunct for Regional Anesthetic Nerve Blocks

PURPOSE OF REVIEW

This article will review current evidence related to the use of dexmedetomidine as an adjuvant for regional anesthesia.

RECENT FINDINGS

Adjuvants, frequently used during regional anesthesia, act synergistically with local anesthetics thus enhancing the quality of regional anesthesia while minimizing adverse effects. These adjuvants may be administered via different routes including topical, perineural, neuraxial, and systemic. Recent studies indicate that dexmedetomidine prolongs the duration of intravenous regional anesthesia, peripheral nerve blocks, and spinal analgesia. Controversy regarding potential neurotoxicity of perineural dexmedetomidine in patients with diabetic neuropathy requires further evaluation.

Ketamine anesthesia enhances fear memory consolidation via noradrenergic activation in the basolateral amygdala

Trauma patients treated with ketamine during emergency care present aggravated early post- traumatic stress reaction which is highly predictive of post-traumatic stress disorder (PTSD) development and severity. The use of ketamine in the acute trauma phase may directly or indirectly interfere with neural processes of memory consolidation of the traumatic event, thus leading to the formation of maladaptive memories, a hallmark symptom of PTSD. We have recently shown that ketamine anesthesia, immediately after a traumatic event, enhances memory consolidation and leads to long-lasting alterations of social behavior in rats. Based on the evidence that ketamine induces a robust central and peripheral adrenergic/noradrenergic potentiation and that activation of this system is essential for the formation of memory for stressful events, we explored the possibility that the strong sympathomimetic action of ketamine might underlie its memory enhancing effects. We found that rats given immediate, but not delayed, post-training ketamine anesthesia (125 mg/kg) presented enhanced 48-h memory retention in an inhibitory avoidance task and that these effects were blocked by adrenal medullectomy, lesions of the locus coeruleus, systemic or intra-basolateral amygdala ß-adrenergic receptor antagonism. Thus, the memory enhancing effects of ketamine anesthesia are time-dependent and mediated by a combined peripheral-central sympathomimetic action. We elucidated a mechanism by which ketamine exacerbates acute post-traumatic reaction, possibly leading to development of PTSD symptomatology later in life. These findings will help guide for a better management of sedation/anesthesia in emergency care to promote the prophylaxis and reduce the risk of developing trauma-related disorders in trauma victims.

Dexmedetomidine-remifentanil vs propofol-remifentanil for monitored anesthesia care during hysteroscopy: Randomized, single-blind, controlled trial

BACKGROUND

Although dexmedetomidine has been used as either the anesthetic agent for light sedation or as an adjunct to other sedatives, no study has investigated the usefulness of dexmedetomidine as the main sedative agent for invasive and painful procedures. The purpose of this study was to compare the safety of dexmedetomidine-remifentanil and propofol-remifentanil during monitored anesthesia care (MAC) for hysteroscopy.

METHODS

Female patients undergoing hysteroscopy were randomly assigned to either the dexmedetomidine (group D) or the propofol group (group P). The study drug (0.6 ml/kg; dexmedetomidine 2 μg/ml or propofol 4 mg/ml) was loaded for 10 minutes followed by 0.1 to 0.5 ml/kg/hour to maintain a bispectral index of 60 to 80 during the procedure. In both groups, remifentanil was infused using a target-controlled-infusion system with a target concentration of 2 ng/ml and titrated during the procedure. The incidence rates of intraoperative respiratory depression in both groups were compared. Postoperative pain and patients satisfaction were also compared.

RESULTS

A total of 69 female patients were included in this study. Dexmedetomidine significantly decrease the incidence of respiratory depression compared with propofol (15/34 [44.1%] vs 5/35 [14.3%], P = .006, group P and D, respectively). Postoperative pain and patients satisfaction score did not differ between the groups.

CONCLUSION

The combination of dexmedetomidine-remifentanil can reduce the incidence of respiratory depression without increasing hemodynamic complications compared with propofol-remifentanil for MAC during hysteroscopy.

A comparative evaluation of different doses of dexmedetomidine as an adjuvant to bupivacaine in transversus abdominis plane block for postoperative analgesia in unilateral inguinal hernioplasty

Background and Aims

The present study is designed to evaluate addition of two different doses of dexmedetomidine (0.25 mcg/kg and 0.5 mcg/kg) as an adjuvant to bupivacaine in transversus abdominis plane block for post-operative analgesia in patients undergoing unilateral inguinal hernioplasty.

Material and Methods

A total of 90 patients scheduled to undergo elective unilateral open inguinal hernioplasty were divided into three groups in a randomized triple blind way. In group B (n = 30), patients received TAP block using 22 ml of solution, consisting of 20 ml of 0.25% bupivacaine and 2 ml of normal saline; in group BD1 (n = 30), patients received TAP block using 22 ml of solution, consisting of 20 ml of 0.25% bupivacaine and dexmedetomidine 0.25 mcg/kg dissolved in 2 ml of normal saline; while in group BD2 (n = 30), patients received TAP block using 22 ml of solution, consisting of 20 ml of 0.25% bupivacaine and dexmedetomidine 0.5 mcg/kg dissolved in 2 ml of normal saline.

Results

Time to first analgesia was significantly prolonged in group BD2 (874.48 ± 118.28 minutes) as compared to BD1 (536.5 ± 60.35 minutes) and B (341.5 ± 46.22 minutes) (P < 0.0001). Total consumption of diclofenac was also reduced in BD2 (80.17 ± 19.34 mg) as compared with B (150 ± 0 mg) and BD1 (147.5 ± 13.69 mg) (P < 0.001). Patients in dexmedetomidine group were more sedated at 1-hour (P < 0.05). None of our patients required any intervention for hemodynamic changes which were significantly more in dexmedetomidine group.

Conclusion

Dexmedetomidine in a dose of 0.5 mcg/kg is better than dose of 0.25 mcg/kg as an adjuvant to 0.25% bupivacaine in transversus abdominis plane block for post-operative pain relief in unilateral inguinal hernioplasty. However, it causes mores sedation and hemodynamic changes.

Effect of Dexmedetomidine on Delirium in Elderly Surgical Patients: A Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The purpose of this meta-analysis is to assess the effect of dexmedetomidine on delirium in elderly surgical patients.

DATA SOURCES

The Cochrane Library, Web of Science, PubMed, EMBASE, and Google Scholar were searched (January 1, 2000, to February 4, 2020) for randomized controlled trials (RCTs).

STUDY SELECTION AND DATA EXTRACTION

RCTs without language restrictions were included if delirium incidence was assessed in elderly surgical patients receiving dexmedetomidine. Intervention and basic information were extracted.

DATA SYNTHESIS

21 studies were included. Dexmedetomidine reduced delirium occurrence (risk ratio [RR] = 0.55; 95% CI = 0.45 to 0.67) in elderly surgical patients with sufficient evidence from trial sequential analysis. Dexmedetomidine did not prevent delirium incidence for cardiac surgery (RR = 0.71; 95% CI = 0.44 to 1.15) with insufficient evidence. Dexmedetomidine decreased mortality incidence (RR = 0.47; 95% CI = 0.25 to 0.89), shortened the length of intensive care unit (ICU; standard mean difference [SMD] = -0.46) and hospital stays (SMD = -0.41), and increased bradycardia incidence (RR = 1.60).

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This review revealed that dexmedetomidine could reduce delirium incidence for elderly noncardiac surgical patients, and the effect of dexmedetomidine on delirium for elderly cardiac surgical patients needs further studies to guide clinicians.

CONCLUSION

Dexmedetomidine reduced delirium incidence in elderly surgical patients. The efficacy of dexmedetomidine on delirium for elderly cardiac surgical patients warrants further studies. Furthermore, dexmedetomidine was associated with an increased bradycardia incidence, shorter length of ICU/hospital stays, and a lower incidence of mortality.

Influence of Epidural Ropivacaine with or without Dexmedetomidine on Postoperative Analgesia and Patient Satisfaction after Thoraco-Lumbar Spine Instrumentation: A Randomized, Comparative, and Double-Blind Study

Study Design

This was a prospective, randomized, and double-blind study.

Purpose

Thoraco-lumbar spine surgery is associated with severe postoperative pain and can cause chronic pain. We aimed to compare the impact of epidural ropivacaine with and without dexmedetomidine on postoperative analgesia after thoracolumbar spine instrumentation wherein an epidural catheter was placed by the surgeon intraoperatively.

Overview of Literature

Very few studies have reported the use of epidural dexmedetomidine in spine surgeries. When used via the epidural route, dexmedetomidine is safe and efficacious and is associated with reduced rescue analgesia consumption, increased duration of analgesia, reduced pain scores, but not with major hemodynamic adverse effects.

Methods

Total 60 American Society of Anesthesiologists I–III adult patients aged 18–65 years who were scheduled to undergo thoraco-lumbar spine instrumentation were randomly allocated into group RD (epidural ropivacaine+dexmedetomidine) or group R (epidural ropivacaine plus saline). We aimed to compare the total rescue analgesic consumption on postoperative day 0, 1, and 2. Moreover, we studied the time to first rescue analgesia with visual analogue scale score <4 and the overall patient satisfaction scores.

Results

There was no difference between the demographic characteristics of the two groups. The mean value of total rescue analgesia consumption was 162.5±68.4 mg in the RD group and 247.5±48.8 mg in the R group. The mean time to first rescue analgesia was 594.6±83.0 minutes in the RD group and 103.6±53.2 minutes in the R group. The mean patient satisfaction score was 4.2±0.7 in the RD group and 3.2±0.6 in the R group. No patient had any respiratory depression or prolonged motor blockade during the postoperative period.

Conclusions

This study demonstrated the superior efficacy, in terms of postoperative analgesia and patient satisfaction scores, of epidural ropivacaine plus dexmedetomidine over that of ropivacaine alone in patients undergoing surgery for thoraco-lumbar spine.

Investigation of the effects of vatinoxan on somatic and visceral antinociceptive efficacy of medetomidine in dogs

OBJECTIVE

To determine whether concurrent vatinoxan administration affects the antinociceptive efficacy of medetomidine in dogs at doses that provide circulating dexmedetomidine concentrations similar to those produced by medetomidine alone.

ANIMALS

8 healthy Beagles.

PROCEDURES

Dogs received 3 IV treatments in a randomized crossover-design trial with a 2-week washout period between experiments (medetomidine [20 μg/kg], medetomidine [20 μg/kg] and vatinoxan [400 μg/kg], and medetomidine [40 μg/kg] and vatinoxan [800 μg/kg]; M20, M20V400, and M40V800, respectively). Sedation, visceral and somatic nociception, and plasma drug concentrations were assessed. Somatic and visceral nociception measurements and sedation scores were compared among treatments and over time. Sedation, visceral antinociception, and somatic antinociception effects of M20V400 and M40V800 were analyzed for noninferiority to effects of M20, and plasma drug concentration data were assessed for equivalence between treatments.

RESULTS

Plasma dexmedetomidine concentrations after administration of M20 and M40V800 were equivalent. Sedation scores, visceral nociception measurements, and somatic nociception measurements did not differ significantly among treatments within time points. Overall sedative effects of M20V400 and M40V800 and visceral antinociceptive effects of M40V800 were noninferior to those produced by M20. Somatic antinociception effects of M20V400 at 10 minutes and M40V800 at 10 and 55 minutes after injection were noninferior to those produced by M20.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested coadministration with vatinoxan did not substantially diminish visceral antinociceptive effects of medetomidine when plasma dexmedetomidine concentrations were equivalent to those produced by medetomidine alone. For somatic antinociception, noninferiority of treatments was detected at some time points.

Comparison of Adrenaline and Dexmedetomidine in Improving the Cutaneous Analgesia of Mexiletine in Response to Skin Pinpricks in Rats

BACKGROUND

Adrenaline (Adr) and dexmedetomidine (Dex) are commonly used adjuvants of local anesthetics; however, the difference in the improvement of analgesia of local anesthetics between the 2 adjuvants remains unclear.

OBJECTIVE

The objective of this experimental research was to evaluate the cutaneous analgesic effect of mexiletine (Mex) by coadministration with Dex or Adr.

METHODS

The effect of a nociceptive block was assessed based on the inhibition of the cutaneous trunci muscle reflex in response to skin pinpricks in rats. The analgesic activity of Mex alone and Mex coadministered with Dex or Adr was evaluated after subcutaneous injections. Subcutaneous injections of drugs or combinations include Mex 0.6, 1.8, and 6.0 μmol; Adr 13.66 nmol; Dex 1.05600 nmol; saline; and Mex 1.8 and 6.0 μmol, respectively, combined with Dex 0.01056, 0.10560, and 1.05600 nmol or Adr 0.55, 2.73, and 13.66 nmol, with each injection dose of 0.6 mL.

RESULTS

Subcutaneous injections of Mex elicited dose-related cutaneous analgesia. Compared with Mex (1.8 μmol), adding Dex or Adr to Mex (1.8 μmol) solutions for skin nociceptive block potentiated and prolonged the action. Mex (6.0 μmol) combined with Dex or Adr extended the duration of cutaneous analgesia when compared with Mex (6.0 μmol) alone. A high dose of Adr is more effective with Mex 1.8 μmol than that of Dex, whereas medium and low doses were less effective. Mex 6.0 μmol combined with any dose of Adr is superior to that of Dex.

CONCLUSIONS

Both Dex and Adr improve the sensory block and enhance the nociceptive block duration of Mex. But in most cases, Adr is superior to Dex. It may be that different mechanisms of action of the 2 adjuvants lead to the differences.

Effect of Intraoperative Sedation with Dexmedetomidine Versus Propofol on Acute Postoperative Pain Following Major Foot Surgery under Popliteal Sciatic Nerve Block: A Randomized Controlled Trial

Intravenous (IV) dexmedetomidine is reported to prolong analgesia following peripheral nerve blocks. Popliteal sciatic nerve block provides effective postoperative analgesia, but some patients still experience severe pain during the early postoperative period. We aimed to evaluate the postoperative analgesic effects of IV dexmedetomidine versus propofol in patients undergoing foot surgeries under popliteal sciatic nerve block. Forty patients were enrolled and randomly assigned to receive either IV propofol (n = 20) or IV dexmedetomidine (n = 20) for intraoperative sedation. All the patients received continuous popliteal sciatic nerve block. The corresponding drug infusion rate was adjusted to achieve a modified observer’s assessment of alertness/sedation score of 3 or 4. The primary outcome was postoperative cumulative opioid consumption during the first 24 h after surgery. Thirty-nine patients were analyzed. The median (interquartile ranges) postoperative cumulative opioid consumption during the first 24 h after surgery was significantly lower in the dexmedetomidine group (15 (7.5–16.9) mg) than in the propofol group (17.5 (15–25) mg) (p = 0.019). The time to first rescue analgesic request was significantly greater in the dexmedetomidine group than in the propofol group (11.8 ± 2.2 h vs. 10.0 ± 2.7 h, p = 0.030) without the prolonged motor blockade (p = 0.321). Intraoperative sedation with dexmedetomidine reduced postoperative opioid consumption and prolonged analgesic duration after a popliteal sciatic nerve block.

Ultrasound-Guided Subclavian Perivascular Brachial Plexus Block Using 0.5% Bupivacaine with Dexmedetomidine as an Adjuvant: A Prospective Randomized Controlled Trial

Background:

Ultrasound guidance has dramatically improved the accuracy of nerve localization, and various adjuvants prolong the block and extend analgesia.

Aims:

This study aimed to evaluate the effects of dexmedetomidine added to 0.5% bupivacaine on the onset and duration of motor and sensory blockade and the duration of analgesia.

Settings and Design:

This is a prospective, randomized double-blind, study.

Materials and Methods:

Sixty adult patients aged 20–60 years of either sex undergoing orthopedic procedures on the forearm were randomly allocated into two groups of thirty each: Group BS (bupivacaine + saline) and Group BD (bupivacaine + dexmedetomidine). All patients were administered subclavian perivascular brachial plexus block under ultrasound guidance. Group BS: Patients in this group were administered 20-mL 0.5% bupivacaine + 0.75-mL saline. Group BD: Patients in this group were administered 20-mL 0.5% bupivacaine + 0.75-mL dexmedetomidine (75 μg).

Statistical Analysis:

Statistical analysis was performed with IBM SPSS software Version 21.0. Quantitative data were expressed as mean ± standard deviation. Independent sample t-test was used for comparisons between the two groups. P < 0.05 was considered statistically significant.

Results:

Demographic data and surgical characteristics were similar in both groups. The onset times for sensory and motor blocks were statistically significantly shorter in Group BD compared to Group BS (P < 0.01), whereas the duration of blocks and analgesia were statistically significantly longer (P < 0.01) in Group BD.

Conclusion:

The addition of dexmedetomidine to 0.5% bupivacaine for supraclavicular brachial plexus block shortens the onset time and prolongs both the duration of the block and analgesia.

The Effect of Dexmedetomidine Added to Preemptive Ropivacaine Infiltration on Postoperative Pain After Lumbar Fusion Surgery: A Randomized Controlled Trial

STUDY DESIGN

A prospective and controlled study of dexmedetomidine added to preemptive ropivacaine infiltration in lumbar fusion surgery.

OBJECTIVE

Assessment of dexmedetomidine added to preemptive ropivacaine infiltration for the relief of postoperative pain after lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

Single local anesthetic preemptive wound infiltration for the relief of postoperative pain does not translate into major or consistent clinical benefits after lumbar fusion surgery. Dexmedetomidine added to local anesthetics prolonged the duration of blockade and enhanced the analgesic in peripheral nerve block. The effect of dexmedetomidine added to preemptive ropivacaine infiltration in lumbar fusion surgery for the relief of postoperative pain has yet not been studied.

METHODS

Fifty-seven patients with elective posterior lumbar fusion were randomly divided into two groups. Five minutes before incision, the skin and subcutaneous tissues were injected with 20 mL 0.5% ropivacaine in group R (n = 28) and 20 mL 0.5% ropivacaine and 1 ug/kg of dexmedetomidine in group RD (n = 29) in two divided doses (i.e., 10 mL per side of the incision line). After the operation, all patients received intravenous morphine for analgesia. The total morphine consumption, the time of first analgesic demand, numbers of PCA analgesia, Visual Analog Scale, and postoperative adverse effects were collected.

RESULTS

In group RD, cumulative morphine dose and numbers of PCA analgesia in group RD were significantly reduced, the time of first analgesic demand was significantly delayed compared to the group R. Visual Analog Scale in group RD showed a marked reduction at 8 hours, 12 hours, 16 hours after operation and less patients in group RD experienced postoperative nausea or vomiting compared to the group R.

CONCLUSION

The addition of dexmedetomidine to preemptive ropivacaine wound infiltration provided a superior analgesic effect, reduced postoperative morphine consumption, and prolonged the time of the first analgesic demand with no serious side effects.

LEVEL OF EVIDENCE

2.

Monitored Anesthesia Care for Cardiovascular Interventions

The interventional cardiology is growing and evolving. Many complex procedures are now performed outside the operating room to manage cardiovascular pathologies which had been traditionally treated with cardiac surgery. Appropriate sedation strategy is crucial for improved patient comfort and successful procedure while ensuring safety. Sedation for cardiovascular intervention is frequently challenging, especially in critically-ill, high-risk patients. This review addresses pre-procedure evaluation and preparation of patients, proper monitoring, commonly used sedatives and analgesics, and considerations for specific procedures. Appropriate depth of sedation and analgesia should be balanced with patient, procedural and institutional factors. Understanding of the pharmacology of sedatives/analgesics, vigilant monitoring, ability and proper preparation for management of potential complications may improve outcomes in patients undergoing sedation for cardiovascular procedures.

Concentrations of medetomidine enantiomers and vatinoxan, an α2-adrenoceptor antagonist, in plasma and central nervous tissue after intravenous coadministration in dogs

OBJECTIVE

To quantify the peripheral selectivity of vatinoxan (L-659,066, MK-467) in dogs by comparing the concentrations of vatinoxan, dexmedetomidine and levomedetomidine in plasma and central nervous system (CNS) tissue after intravenous (IV) coadministration of vatinoxan and medetomidine.

STUDY DESIGN

Experimental, observational study.

ANIMALS

A group of six healthy, purpose-bred Beagle dogs (four females and two males) aged 6.5 ± 0.1 years (mean ± standard deviation).

METHODS

All dogs were administered a combination of medetomidine (40 μg kg^-1) and vatinoxan (800 μg kg^-1) as IV bolus. After 20 minutes, the dogs were euthanized with an IV overdose of pentobarbital (140 mg kg^-1) and both venous plasma and CNS tissues (brain, cervical and lumbar spinal cord) were harvested. Concentrations of dexmedetomidine, levomedetomidine and vatinoxan in all samples were quantified by liquid chromatography-tandem mass spectrometry and data were analyzed with nonparametric tests with post hoc corrections where appropriate.

RESULTS

All dogs became deeply sedated after the treatment. The CNS-to-plasma ratio of vatinoxan concentration was approximately 1:50, whereas the concentrations of dexmedetomidine and levomedetomidine in the CNS were three- to seven-fold of those in plasma.

CONCLUSIONS AND CLINICAL RELEVANCE

With the doses studied, these results confirm the peripheral selectivity of vatinoxan in dogs, when coadministered IV with medetomidine. Thus, it is likely that vatinoxan preferentially antagonizes α₂-adrenoceptors outside the CNS.

Comparative Evaluation of IV Paracetamol Versus IV Dexmedetomidine in Inpatient Oral and Maxillofacial Surgery: A Double-Blinded Randomized Controlled Study

Purpose

Reconstructive surgeries following fractures in the maxillofacial region often involve considerable bone manipulation, and paracetamol is a commonly used analgesic medication in both intraoperative and postoperative periods. Dexmedetomidine, an alpha-2 adrenoceptor agonist, has both sedative and analgesic properties with minimal cardiorespiratory effects and has been used primarily for its sedative properties in oral and maxillofacial surgery.

Aims and Objectives

To compare the intraoperative analgesic requirements among patients undergoing oral and maxillofacial surgery who receive IV paracetamol versus IV dexmedetomidine. The time to requirement for the first postoperative analgesic dose and safety and adverse events of both medications were also assessed.

Patients and Methods

In total, 64 patients needing primary reconstructive surgery for facial fractures were recruited and divided into two groups for this double-blinded study. Patients were randomized to receive a preinduction dose of either IV paracetamol 1 g (Group P) or IV dexmedetomidine 1 µg/kg (Group D). Sedation scores (Ramsay sedation scale), maximal interincisal distance and pain scores at maximal mouth opening (visual analogue scale) were assessed in both groups just prior to and after the administration of the study drugs. After induction, Group P and Group D received a maintenance dose of normal saline and dexmedetomidine (0.5 µg/kg/h) during the intraoperative period, respectively. Standard noninvasive cardiorespiratory monitoring was done for the entire duration of surgery. Following extubation, postoperative pain scores and the time to request for first analgesic dose in either group were recorded.

Results

The time taken to perform the surgery was comparable in both groups. There was a significant difference between the groups in visual analogue scores and interincisal distance after the bolus dose (p < 0.05). Systolic and diastolic blood pressure was significantly lower in Group D at around 150 and 175 min of surgery. While the intraoperative fentanyl consumption was comparable in both groups, the time to request for the first analgesic dose in the postoperative period was significantly delayed in Group P (p < 0.05). No adverse cardiopulmonary events were observed in either group.

Conclusion

The intraoperative anesthetic and analgesic requirements and hemodynamic stability were comparable in IV paracetamol and dexmedetomidine groups. Dexmedetomidine did not confer any enhanced analgesia effect in the postoperative period. More research examining the role of dexmedetomidine for longer duration inpatient oral and maxillofacial surgery is needed.

Clinical Trial Number

http://ClinicalTrials.gov (No. CTRI/2017/08/009468).

Analgesia and sedation post-coronary artery bypass graft surgery: a review of the literature

This review aimed to study the role of analgesia and sedation after coronary artery bypass graft (CABG) surgery, regarding pain management, assisted respiration, overall postoperative health care, and hospitalization. Data were collected from Pubmed, Scopus, and Cochrane databases. The following terms were used for the search: “analgesia”, “sedation”, “coronary artery bypass grafting”, CABG”, and “opioids”. Articles between the years 1988 and 2018 were evaluated. Several opioid and non-opioid analgesics used to relieve surgical pain are regarded as critical risk factors for developing pulmonary and cardiovascular complications in all kinds of thoracic surgery, especially CABG procedures. Effective pain management in post-CABG patients is largely dependent on effective pain assessment, type of sedatives and analgesics administered, and evaluation of their effects on pain relief. A significant challenge is to determine adequate amounts of administered analgesics and sedatives for postoperative CABG patients, because patients often order more sedatives and analgesics than needed. The pain management process is deemed successful when patients feel comfortable after surgery, with no negative side effects. However, postoperative pain management patterns have not included many modern methods such as patient-controlled analgesia, and postoperative pain management drugs are still limited to a restricted range of opioid and non-opioid analgesics.

Postoperative pain control after the use of dexmedetomidine and propofol to sedate patients undergoing ankle surgery under spinal anesthesia: a randomized controlled trial

Background: Dexmedetomidine is widely used for conscious sedation in patients undergoing lower-extremity surgery under regional anesthesia. We evaluated the postoperative analgesic effects of intravenous dexmedetomidine given during ankle surgery under spinal anesthesia.

Methods: Forty-three participants underwent repair of lateral angle ligaments under spinal anesthesia. For sedation during surgery, participants were allocated to a dexmedetomidine group (n=22) that received a loading dose of 1 mcg.kg⁻¹ over 10 min, followed by a maintenance dose of 0.2–0.7 μg.kg⁻¹.h⁻¹; and a propofol group (n=21) that received an effective site concentration of 0.5–2.0 μg.mL⁻¹ via target-controlled infusion. The primary outcome was the postoperative, cumulative, intravenous (IV) morphine equivalent dose delivered via IV patient-controlled anesthesia (PCA) and rescue analgesic consumption in the first 24 h after surgery. We recorded sensory and motor block durations.

Results: The postoperative IV morphine equivalent dose was 14.5 mg (0.75–31.75 mg) in the dexmedetomidine group compared to 48.0 mg (31.5–92.5 mg) in the propofol group (median difference, 33.2 mg; 95% confidence interval, 21.0–54.8 mg; P<0.001). The time to the first complaint of surgical site pain was significantly prolonged in the dexmedetomidine group (P<0.001), but the duration of motor block was comparable between the two groups (P=0.55).

Conclusion: IV dexmedetomidine given as a sedative during ankle surgery under spinal anesthesia reduced postoperative opioid consumption in the first 24 h. Thus, intraoperative dexmedetomidine is a versatile sedative adjunct.

Level of evidence: Level I, prospective randomized trial.

Evaluation of analgesic interaction between morphine, dexmedetomidine and maropitant using hot-plate and tail-flick tests in rats

OBJECTIVE

To determine if the combinations of morphine, dexmedetomidine and maropitant enhance the analgesic effect and decrease the dose of individual drugs in rats subjected to noxious thermal stimulation with hot-plate and tail-flick tests.

STUDY DESIGN

Randomized, blinded, prospective experimental study.

ANIMALS

A total of 96 male Sprague-Dawley rats.

METHODS

The rats were randomly assigned to the following groups: 1) morphine (3 mg kg^-1; Mor); 2) dexmedetomidine (10 μg kg^-1; Dex); 3) maropitant (20 mg kg^-1; Maro); 4) morphine (1.5 mg kg^-1) + dexmedetomidine (5 μg kg^-1; Mor + Dex); 5) dexmedetomidine (5 μg kg^-1) + maropitant (10 mg kg^-1; Dex + Maro); 6) morphine (1.5 mg kg^-1) + maropitant (10 mg kg^-1; Mor + Maro); 7) morphine (1 mg kg^-1) + dexmedetomidine (3.5 μg kg^-1) + maropitant (6.5 mg kg^-1; Mor + Dex + Maro); and 8) normal saline (0.5 mL; saline), all injected intravenously. The tail-flick and hot-plate tests were performed before and 5, 15, 30, 45, 60, 90 and 120 minutes after the injection of the drugs. These variables were analysed with the effect-time area under the curve (AUC) analysis and a mixed linear model.

RESULTS

Data were analysed in 94 rats. The rank order of the total analgesic effects of the treatment groups shown by AUC analysis was found to be Mor > Maro + Mor > Dex + Mor > Dex > Maro > Dex + Maro + Mor > Dex + Maro > saline for the hot-plate test, and Maro + Mor > Mor > Dex + Mor > Dex + Maro + Mor > Maro > Dex > Dex + Maro > saline for the tail-flick test. The mixed model analysis showed a significant difference between latencies of the group morphine + maropitant versus all other treatment groups in the tail-flick test (p < 0.0001) and morphine versus saline in the hot-plate test (p < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Morphine and maropitant appeared to show a supra-additive effect for analgesia in the tail-flick test. Clinical trials should be conducted to establish its use in treating pain.

Thermal antinociceptive, sedative and cardiovascular effects of Governing Vessel 1 dexmedetomidine pharmacopuncture in healthy cats

OBJECTIVE

To compare the antinociceptive, sedative and cardiovascular effects of dexmedetomidine pharmacopuncture at Governing Vessel 1 (GV 1) with dexmedetomidine intramuscular (IM) administration.

STUDY DESIGN

Randomized, masked crossover design.

ANIMALS

A group of eight healthy female cats.

METHODS

Cats were randomly administered either dexmedetomidine (0.005 mg kg^-1; Dex-IM) IM or at acupuncture point GV 1 (Dex-P) separated by 1 week. Prior to and up to 120 minutes posttreatment, skin temperature (ST), thermal threshold (TT), heart rate (HR), respiratory rate (f_R), sedation, muscle relaxation and auditory response scores were recorded. Parametric data were analyzed using a two-way repeated measures anova followed by Tukey's test for multiple comparisons. Nonparametric data were analyzed using a Friedman test followed by Dunn's multiple comparisons test, and Wilcoxon signed-rank test with Bonferroni correction for multiple comparisons. Significance was set at p ≤ 0.05.

RESULTS

There were no differences within or between treatments for ST, f_R and auditory response. TT was significantly higher at 30-90 minutes in Dex-P (p ≤ 0.0285) than baseline. TT was significantly higher at 60-90 minutes for Dex-P than for Dex-IM (p ≤ 0.0252). HR was significantly lower at 10-75 minutes in Dex-P (p ≤ 0.0378) and at 5-75 minutes in Dex-IM (p ≤ 0.0132) than baseline. Compared with baseline, sedation scores were higher at 25 minutes (p = 0.0327) and 30 minutes (p = 0.0327), and muscle relaxation scores were higher at 25 minutes (p = 0.0151) and 35 minutes (p = 0.0151) in Dex-P. There were no differences in HR, sedation and muscle relaxation scores between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Dex-P increased thermal antinociception compared with Dex-IM at the same dose of dexmedetomidine in cats. This antinociceptive effect must be evaluated under clinical situations.

Intraoperative dexmedetomidine infusion is associated with reduced emergence agitation and improved recovery profiles after lung surgery: a retrospective cohort study

Purpose

This retrospective cohort study aimed to investigate the association between intraoperative dexmedetomidine infusion and emergence agitation (EA), and recovery profiles after lung surgery in adult patients. It was hypothesized that dexmedetomidine was associated with reduced EA and improved recovery profiles.

Patients and methods

A single-center chart review was conducted on elective lung surgeries in adults between January and December 2016. The primary outcome was the incidence of EA in postanesthesia care units (PACUs). The secondary outcomes included rescue analgesia, shivering, time to extubation, residual sedation, postoperative pulmonary events, duration of PACU stay, length of hospital stay, and intraoperative hemodynamic changes. Univariate and multivariate regression analyses were used to analyze data.

Results

Among 2,468 patients, 814 received an intraoperative dexmedetomidine infusion. Intraoperative dexmedetomidine infusion was associated with a lower incidence of EA (10.9% vs 15.0%; adjusted OR, 0.67; 95% CI, 0.51–0.87; P=0.003), rescue analgesia (7.6% vs 12.2%; adjusted OR, 0.63; 95% CI, 0.47–0.86; P=0.003), shivering (4.2% vs 6.6%; adjusted OR, 0.58; 95% CI, 0.38–0.88; P=0.010), and intraoperative bradycardia (18.6% vs 12.6%; adjusted OR, 1.51; 95% CI, 1.19–1.92; P=0.001). No differences were observed in residual sedation, duration of PACU stay, postoperative pulmonary events, and length of hospital stay between the groups.

Conclusion

This retrospective study suggested that intraoperative dexmedetomidine infusion was associated with a lower incidence of EA, rescue analgesia, and shivering in adults after lung surgery. Intraoperative bradycardia was the main side effect.

Thoracic Paravertebral Block with Adjuvant Dexmedetomidine in Video-Assisted Thoracoscopic Surgery: A Randomized, Double-Blind Study

Background: The addition of the adjuvant dexmedetomidine to a nerve block improves the quality of the block and reduces perioperative opioid consumption. The aim of this study was to assess the effect of dexmedetomidine as an adjuvant for the thoracic paravertebral block (TPVB) in postoperative pain control after video-assisted thoracoscopic surgery (VATS). Methods: Sixty-six males, aged 15–40 years, with spontaneous pneumothorax scheduled for VATS wedge resection were enrolled. Following surgery, ultrasound-guided TPVB was performed on the T3 and T5 levels with 30 mL of 0.5% ropivacaine, plus adjuvant dexmedetomidine 50 μg or normal saline. The primary outcome was cumulative fentanyl consumption at 24 h. Pain severity, the requirement for additional rescue analgesics, hemodynamic variations, and side effects were also evaluated. Results: Median postoperative cumulative fentanyl consumption at 24 h was significantly lower in the dexmedetomidine group (122.6 (interquartile range (IQR) 94.5–268.0) μg vs. 348.1 (IQR, 192.8–459.2) μg, p-value = 0.001) with a Hodges–Lehman median difference between groups of 86.2 (95% confidence interval (CI), 4.2–156.4) mg. Coughing numeric rating scale (NRS) was lower in the dexmedetomidine group at postoperative 2, 4, 8, and 24 h. However, resting NRS differed significantly only after 4 h postoperative. Conclusions: Dexmedetomidine as an adjunct in TPVB provided effective pain relief and significantly reduced opioid requirement in VATS.

Selective deficiencies in descending inhibitory modulation in neuropathic rats: implications for enhancing noradrenergic tone

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Descending noradrenergic pathways modulate spontaneous but not evoked thalamic neuronal hyperexcitability in neuropathic pain states. Spinal clonidine inhibits evoked and spontaneous firing, whereas reboxetine selectively inhibits evoked firing.

Pontine noradrenergic neurones form part of a descending inhibitory system that influences spinal nociceptive processing. Weak or absent descending inhibition is a common feature of chronic pain patients. We examined the extent to which the descending noradrenergic system is tonically active, how control of spinal neuronal excitability is integrated into thalamic relays within sensory-discriminative projection pathways, and how this inhibitory control is altered after nerve injury. In vivo electrophysiology was performed in anaesthetised spinal nerve–ligated (SNL) and sham-operated rats to record from wide dynamic range neurones in the ventral posterolateral thalamus (VPL). In sham rats, spinal block of α₂-adrenoceptors with atipamezole resulted in enhanced stimulus-evoked and spontaneous firing in the VPL, and produced conditioned place avoidance. However, in SNL rats, these conditioned avoidance behaviours were absent. Furthermore, inhibitory control of evoked neuronal responses was lost, but spinal atipamezole markedly increased spontaneous firing. Augmenting spinal noradrenergic tone in neuropathic rats with reboxetine, a selective noradrenergic reuptake inhibitor, modestly reinstated inhibitory control of evoked responses in the VPL but had no effect on spontaneous firing. By contrast, clonidine, an α₂ agonist, inhibited both evoked and spontaneous firing, and exhibited increased potency in SNL rats compared with sham controls. These data suggest descending noradrenergic inhibitory pathways are tonically active in sham rats. Moreover, in neuropathic states, descending inhibitory control is diminished, but not completely absent, and distinguishes between spontaneous and evoked neuronal activity. These observations may have implications for how analgesics targeting the noradrenergic system provide relief.

Randomized Open-Labelled Comparative Evaluation of the Efficacy of Nitroglycerine, Esmolol and Dexmedetomidine in Producing Controlled Hypotension in Spine Surgeries

Aim:

This study was designed to evaluate the efficacy of nitroglycerine (NTG), esmolol, and dexmedetomidine (DEX) as hypotensive agents in decreasing intraoperative blood loss by producing controlled hypotension in posterior spine surgeries.

Materials and Methods:

Sixty patients aged 18–60 years, the American Society of Anesthesiologists physical status Classes I and II of either gender, were randomly assigned into three groups to receive either: NTG (0.01%) at the rate of 3–10 μg.kg^-1.min^-1 after positioning without a prior loading dose in Group N, esmolol 500 μg.kg^-1 loading dose over 1 min before induction of anesthesia followed by 50–300 μg.kg^-1.min^-1 infusion in Group E, and DEX 1 μg.kg^-1 over 10 min before induction followed by 0.2–0.7 μg.kg^-1.h^-1. infusion in Group D to maintain mean arterial blood pressure (MAP) between 60 and 65 mmHg. The three groups were compared for the achievement of target MAP, intraoperative blood loss, reversibility of hypotensive state, quality of surgical field, emergence time, and postextubation sedation score.

Statistical Analysis:

Analysis of variance was used for intergroup analysis, and for multiple comparisons, Bonferroni post hoc test was applied. P < 0.05 was considered statistically significant.

Results:

Patients in Group D and Group E achieved the target MAP with better heart rate control as compared to Group N. The intraoperative blood loss was significantly lesser in Group D (P < 0.001). The time to hypotension reversal and emergence time was prolonged in Group D (P < 0.001). The mean quality of surgical field score was statistically insignificant among the three groups. The mean Ramsay Sedation Scores were significantly higher in Group D compared to Groups N and E at 20^th and 40^th min postextubation (P < 0.001) with no significant intergroup difference at 60^th min postextubation (P = 0.130).

Conclusion:

Continuous infusion of DEX is an effective and safe method of producing controlled hypotension by achieving the target MAP, minimizing blood loss, and maintaining superior hemodynamics in comparison with NTG and esmolol in posterior spine surgeries.

Effect of two different doses of dexmedetomidine on the incidence of emergence agitation after strabismus surgery: a randomized clinical trial

Background and objective

Emergence agitation is a postoperative negative behavior that affects mainly children. We studied the effect of two different doses of dexmedetomidine on the incidence and degree of EA in children undergoing strabismus surgery.

Methods

90 patients were allocated into three equal groups; patients received 0.5 μg.kg⁻¹ of dexmedetomidine in high Dex group, 0.25 μg.kg⁻¹ of dexmedetomidine in low Dex group, or normal saline in the placebo group. All drugs were received with the closure of the conjunctiva before the end of the surgery. Pediatric Anesthesia Emergence Delirium (PAED) scale was used to evaluate the agitation, and Face, Legs, Activity, Cry, Consolability (FLACC) scale was used for pain assessment. Adverse effects of dexmedetomidine and recovery times were recorded.

Results

The incidence of agitation was significantly lower in high Dex group compared to other groups and it was significantly lower in low Dex group compared to placebo group. The median (range) of FLACC score was significantly lower in both Dex groups compared to placebo group. Recovery times; time from removal of laryngeal mask to eye opening and time stay in post anesthesia care unit was significantly longer in high Dex group compared to other groups. No significant bradycardia or hypotension was recorded. Recovery time was significantly longer in high Dex group compared to the other two groups.

Conclusion

Dexmedetomidine (0.5 μg.kg⁻¹) before emergence from general anesthesia resulted in a reduction in the incidence of emergence agitation compared to a dexmedetomidine (0.25 μg.kg⁻¹) but on the expense of recovery times without adverse effects.