Alpha-2 adrenoceptor agonists as adjuncts to Peripheral Nerve Blocks in Children--is there a mechanism of action and should we use them?

Advantages of ketamine in pediatric anesthesia

Although ketamine is primarily used for induction and maintenance of general anesthesia, it also presents sedative, amnestic, anesthetics, analgesic, antihyperalgesia, neuroprotective, anti-inflammatory, immunomodulant, and antidepressant effects. Its unique pharmacodynamics and pharmacokinetic properties allow the use of ketamine in various clinical settings including sedation, ambulatory anesthesia, and intensive care practices. It has also adopted to manage acute and chronic pain management. Clinically, ketamine produces dissociative sedation, analgesia, and amnesia while maintaining laryngeal reflexes, with respiratory and cardiovascular stability. Notably, it does not cause respiratory depression, maintaining both the hypercapnic reflex and the residual functional capacity with a moderate bronchodilation effect. In the pediatric population, ketamine can be administered through practically all routes, making it an advantageous drug for the sedation required setting such as placement of difficult vascular access and in uncooperative and oppositional children. Consequently, ketamine is indicated in prehospital induction of anesthesia, induction of anesthesia in potentially hemodynamic unstable patients, and in patients at risk of bronchospasm. Even more, ketamine does not increase intracranial pressure, and it can be safely used also in patients with traumatic brain injuries. This article is aimed to provide a brief and practical summary of the role of ketamine in the pediatric field.

The Use of Multimodal Perineural Adjuvants in Pediatric Peripheral Nerve Blocks: Technique and Experiences

Background

Postoperative pain management in pediatric population can be very challenging. How to prolong the duration of single-injection peripheral nerve blocks has been widely discussed. Multiple medications are under investigation to accomplish this, yet data specifically focused on their use in pediatric peripheral nerve blocks are limited.

Methods

Anesthetic electronic medical records were queried for any instances where adjuvant drug(s) were used in peripheral nerve blocks during a two-year period at a pediatric surgical specialty hospital. These included buprenorphine, clonidine, dexamethasone, and dexmedetomidine. 

Results

Out of 1,845 blocks placed during the study period, 1,148 (62.2%) utilized perineural adjuvants. Buprenorphine as a sole agent was the most common choice (49.5%), followed by buprenorphine and dexmedetomidine combined (39.9%), dexmedetomidine alone (10.1%), and the rare combination of all three drugs, buprenorphine, dexmedetomidine, and dexamethasone (0.5%). The mean dose of buprenorphine given was 3.6 mcg/kg total, 2.8 mcg/kg/block. The mean dose of dexmedetomidine given was 0.9 mcg/kg total, 0.6 mcg/kg/block. The mean dose of dexamethasone utilized was 2 mg total, 1 mg/block. 

Conclusions

This report examined one institution’s use of multimodal perineural adjuvants in over 1,000 pediatric peripheral nerve blocks. Buprenorphine was the agent most commonly used to prolong the single-injection peripheral nerve block. This highlights the need for future prospective trials evaluating efficacy and safety.

Dexmedetomidine as an adjuvant to 0.25% bupivacaine in ultrasound guided femoral nerve block for preoperative positioning and postoperative analgesia in patients undergoing elective surgery for fracture shaft of femur

Background:

Femur fracture causes excruciating pain and surgical repair is recommended. To obtain satisfactory patient co-operation in the perioperative period, various analgesics have been used. Femoral nerve block (FNB) provides an excellent alternative for analgesia in the perioperative period. Dexmedetomidine of up to 2 μg.kg⁻¹ has been used in FNB as adjuvants in lower limb surgeries.

Aims:

The aim was to study the effect of addition of Dexmedetomidine to Bupivacaine in FNB on the comfort of positioning for subarachnoid block (SAB) and postoperative analgesia.

Materials and Methods:

Prospective, randomized, double-blind design was followed. Seventy American Society of Anesthesiologist I and II patients aged 18–70 years of either gender were randomly allocated into Group B (20 mL 0.25% Bupivacaine + 2 mL Normal Saline) and Group BD (received 20 mL 0.25% Bupivacaine + Dexmedetomidine 2 μg.kg⁻¹ diluted to 2 mL) for FNB. Numerical rating scale (NRS) was recorded before and after FNB and comfort of positioning graded. After 10 min, subarachnoid block (SAB) was administered. NRS was recorded postoperatively until 24 h.

Results:

The comfort of positioning improved in both the groups after FNB but was statistically not significant when compared among the groups (P = 0.7). Duration of postoperative analgesia was significantly higher in the Group BD (741 min ± 97 min) compared to the Group B (440 min ± 45 min) (P = 0.001) and was statistically significant.

Conclusion:

FNB improved the comfort of positioning for SAB, but the addition of Dexmedetomidine did not have any added advantages with respect to comfort of positioning. However, the addition of Dexmedetomidine significantly increased the duration of postoperative analgesia with minimal hemodynamic changes.

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.

Efficacy of Dexmedetomidine as an Adjuvant to Local Anesthetic Agent in Scalp Block and Scalp Infiltration to Control Postcraniotomy Pain: A Double-Blind Randomized Trial

Context

Scalp infiltration and scalp block are being used to manage postcraniotomy pain. Dexmedetomidine has been successfully used as an adjuvant in regional anesthesia. The study was intended to compare whether addition of dexmedetomidine prolonged the duration of analgesia as well as to compare the two techniques.

Aims

The primary objective was to assess whether addition of dexmedetomidine to bupivacaine prolonged the duration of analgesia. The secondary objective was to compare between scalp nerve block and scalp infiltration as techniques for pain relief.

Settings and Design

The randomized control study was conducted in a tertiary care center from November 2013 to October 2014.

Materials and Methods

A total of 150 American Society of Anesthesiologists Physical Status I-II patients, aged 18-70 years undergoing elective craniotomy were included. Patients were randomized into three groups of 50 patients, i.e., Group BI (bupivacaine infiltration), Group BDI (bupivacaine and dexmedetomidine infiltration), and Group BDNB (bupivacaine and dexmedetomidine scalp nerve block). Patient's pain score, pain-free interval, rescue analgesic requirement, and hemodynamic and respiratory parameters were noted for 48 h. Patients were followed up at 1 and 3 months to assess postcraniotomy pain.

Results

Pain-free period was significantly longer in Group BDNB than Groups BDI and BI (P < 0.0001) and pain control was better in dexmedetomidine containing groups than in bupivacaine group (BI) (P < 0.0001). The rescue analgesic requirement was significantly lower in Group BDNB and Group BDI compared to Group BI.

Conclusion

The addition of dexmedetomidine (1 μg/kg) to bupivacaine prolonged the pain-free period. Scalp nerve block is a superior technique than scalp infiltration.

Dexmedetomidine versus Magnesium as Adjuvants to Bupivacaine-Induced Caudal Block in Children: A Randomized, Double-Blinded, Placebo-Controlled, Trial

BACKGROUND

Caudal block remains fundamental in pediatric anaesthetic practice. It is very useful in a wide range of surgical procedures and has proved to have a remarkable safety record, But one of the major limitations of the single-injection technique is the relatively short duration of postoperative analgesia. Prolongation of caudal analgesia using single-shot technique has been achieved by the addition of various adjuvant.

AIM

This work aims to compare magnesium and dexmedetomidine as adjuvants to bupivacaine-induced caudal block in children undergoing lower limb orthopaedic surgery.

STUDY DESIGN

Randomized, double-blind trial.

SETTINGS

Pediatric or of a tertiary care centre.

METHODS

A double-blinded, randomised controlled trial included 36 children, aged between 1 and 7 years, scheduled for lower limb orthopaedic surgery. Patients received general anaesthesia in addition to the caudal block. Patients were divided into three groups: Dexmedetomidine group (n = 12): received 0.5 mL/Kg bupivacaine + 2 mcg/Kg dexmedetomidine, Magnesium group (n = 12): received 0.5 mL/Kg bupivacaine + 50 mg magnesium, and control group (n = 12): received 0.5 mL/Kg bupivacaine + normal saline. Patients were compared according to the duration of analgesia, pain scores, sedation scores, mean arterial pressure, and heart rate.

RESULTS

Both magnesium group and dexmedetomidine group showed better analgesic profile (duration of analgesia and pain scores) compared to the control group without significant difference between the two former groups. Dexmedetomidine group showed higher sedation score, lower mean arterial pressure and lower heart rate compared to other groups.

CONCLUSIONS

Both magnesium (50 mg) and dexmedetomidine (2 mcg/Kg) improved the analgesic profile of bupivacaine-induced caudal block in children. Dexmedetomidine administration was accompanied with higher sedation score and negative hemodynamic profile.

Iatrogenic hypertension: a bioinformatic analysis

It is well known that a myriad of medications and substances can induce side effects that are related to blood pressure (BP) regulation. This study aims to investigate why certain drugs tend to cause iatrogenic hypertension (HTN) and focus on drug targets that are implicated in these conditions.Databases and resources such as SIDER, DrugBank, and Genomatix were utilized in order to bioinformatically investigate HTN-associated drug target-genes for which HTN is a side effect. A tree-like map was created, representing interactions between 198 human genes that relate to the blood pressure system. 72 HTN indicated drugs and 160 HTN-inducing drugs were investigated. HTN-associated genes affected by these drugs were identified. HTN indicated drugs, which target nearly all branches of the interaction tree, were shown to exert an effect on most functional sub-systems of the BP regulatory system; and specifically, for the adrenergic and dopaminergic receptor pathways. High prevalence (25 genes) of shared targets between the HTN indicated and HTN-inducing drug categories was demonstrated. We focus on six drug families which are not indicated for HTN treatment, yet are reported as a major cause for blood pressure side effects. We show the molecular mechanisms that may lead to this iatrogenic effect. Such an analysis may have clinical implications that could allow for the development of tailored medicine with fewer side effects.

Optimal dose of perineural dexmedetomidine for interscalene brachial plexus block to control postoperative pain in patients undergoing arthroscopic shoulder surgery: A prospective, double-blind, randomized controlled study

BACKGROUND

Adjuvant perineural dexmedetomidine can be used to prolong the analgesic effect of interscalene brachial plexus block (ISB). We investigated the optimal dose of dexmedetomidine in ISB for postoperative analgesia in patients undergoing arthroscopic shoulder surgery.

METHODS

One hundred patients scheduled for elective shoulder arthroscopic surgery were enrolled in this randomized, double-blind study. Ultrasound-guided ISB was performed before general anesthesia using 22 mL of ropivacaine 0.5% combined with 1, 1.5, or 2 μg/kg of dexmedetomidine (group D1, D2, and D3, respectively) or with normal saline as a control (group R, n = 25 per group). The primary outcome was the duration of analgesia (DOA), numeric pain rating scale (NRS), and consumption of additional analgesics during 36 h after ISB. Secondary outcome included durations of motor and sensory block (DOM and DOS), hemodynamic variables and sedation and dyspnea scores.

RESULTS

Ninety-seven patients completed the study. The DOS, DOM, and DOA were significantly longer in the dexmedetomidine groups than in group R. The DOA was significantly longer in group D3 than in groups D1 (P = .026) and D2 (P = .039). The DOA was 808.13 ± 179.97, 1032.60 ± 288.14, 1042.04 ± 188.13, and 1223.96 ± 238.06 min in groups R, D1, D2, and D3, respectively. The NRS score was significantly higher in group R than in the dexmedetomidine groups 12 h after ISB (P < .001) and significantly lower in group D3 than in the other groups 18 h after ISB (P = .02). The incidence of hypotension was higher in groups D2 and D3 than in group R during surgery (P = .008 and P = .011, respectively). There were no significant differences in consumption of rescue analgesics, sedation, and dyspnea scores between the study groups.

CONCLUSION

Perineural dexmedetomidine 2 μg/kg could be the optimal dose in ISB for arthroscopic shoulder surgery in that it provides an adequate DOA. However, this dose was associated with increased risk of hypotension.

Alpha-2 adrenoceptor agonists as adjuncts to peripheral nerve blocks in children: a meta-analysis

BACKGROUND

Adult meta-analyses have verified that adjunct use of alpha-2 adrenoceptor agonists (A2AA) together with local anesthetics (LA) will prolong the duration of peripheral nerve blocks. The standard use of A2AAs for peripheral nerve blockade has recently been recommended also in children, but the evidence base in support of this suggestion has to date been equivocal. The purpose of this meta-analysis was to produce evidence-based data regarding the effect in children.

METHODS

Following a thorough literature search, five randomized controlled trials were included in a meta-analysis. Raw data from all studies were gathered and aggregated into patients randomized to receive plain LA (Group PLA) or LA mixed with either adjunct clonidine or dexmedetomidine (Group ADJ). The main outcome parameter was block duration (time to first administration of supplemental analgesic based on predetermined pain scores) analyzed by survival statistics. The total number of supplemental analgesic doses during the first 24 postoperative hours and serious side effects were included as secondary outcomes.

RESULTS

Pooling of the study data generated 141 patients in Group PLA and 142 patients in Group ADJ (overall n = 283; age: 0.8-13 years; weight 8-47 kg). Block duration was significantly prolonged (9.75 h vs 3.75 h) compared to the use of plain LA. Survival statistics verified a beneficial effect of using adjunct A2AAs [the log rank (Mantel-Cox) test (P = 0.0078), Gehan-Breslow-Wilcoxon test (P = 0.0027), and hazard ratio (1.653; 95% CI: 1.142 to 2.395)]. The number of patients that needed ≥ 2 doses of supplemental analgesics was higher in Group PLA (n = 19) compared to Group ADJ (n = 6) (P = 0.0088). No serious side effects were reported.

CONCLUSION

This meta-analysis provides evidence-based support for the use of adjunct alpha-2 adrenoceptor agonists when performing peripheral nerve blocks in children.

Adjuncts should always be used in pediatric regional anesthesia

A number of different adjuncts to local anesthetics can be used to prolong and optimize postoperative pain relief following regional anesthesia in children. The present text provides a slightly opinionated but evidence-based argument in favor of this practice.

Adjuvants in pediatric regional anesthesia

SUMMARY Local anesthetics have a limited duration of action. Adjuvants are used to prolong the duration of action and to augment analgesia allowing lower concentrations of local anesthetic to be used. Adjuvants have been used more extensively with neuraxial blocks, particularly caudal epidural blocks, but more recently to supplement peripheral nerve blocks. Intrathecal adjuvants are not covered in this review since spinal anesthesia is not widely used in children except in ex-premature infants. Morphine is the historical gold-standard with which other adjuvants are compared. Clonidine is most useful and is becoming increasingly popular, while the side-effect profile of other agents reduces their utility. Concerns with regard to the neurotoxicity of ketamine in animal models has led to its withdrawal in some countries.

Comparison of dexmedetomidine and epinephrine as an adjuvant to 1% mepivacaine in brachial plexus block

BACKGROUND

Dexmedetomidine extends the duration of nerve block when administered perineurally together with local anesthetics by central and/or peripheral action. In this study, we compared the duration of nerve block between dexmedetomidine and epinephrine as an adjuvant to 1% mepivacaine in infraclavicular brachial plexus block.

METHODS

Thirty patients, scheduled for upper limb surgery were assigned randomly to 3 groups of 10 patients each. We performed brachial plexus block using a nerve stimulator. In the control group (group C), patients received 40 ml of 1% mepivacaine. In group E, patients received 40 ml of 1% mepivacaine containing 200 µg of epinephrine as an adjuvant. In group D, patients received 40 ml of 1% mepivacaine containing 1 µg/kg of dexmedetomidine as an adjuvant. Sensory block duration, motor block duration, time to sense pain, and onset time were assessed. We also monitored blood pressure, heart rate, oxygen saturation and bispectral index.

RESULTS

In group D and group E, sensory block duration, motor block duration and time to sense first pain were prolonged significantly compared to group C. However, there was no significant difference between group D and group E.

CONCLUSIONS

Perineural 1 µg/kg of dexmedetomidine similarly prolonged nerve block duration compared to 200 µg of epinephrine, but slowed heart rate. Thus, dexmedetomidine is expected to be a good alternative as an adjuvant to local anesthesia in patients who are cautioned against epinephrine.

Dexmedetomidine as an adjuvant to ropivacaine prolongs peripheral nerve block: a volunteer study

BACKGROUND

Dexmedetomidine is an α-2-receptor agonist which might be used as an additive to local anaesthetics for various regional anaesthetic techniques. We therefore designed this prospective, double-blinded, controlled volunteer study to investigate the effects of dexmedetomidine as an adjuvant to ropivacaine on peripheral nerve block.

METHODS

Ultrasound-guided ulnar nerve block (UNB) was performed in 36 volunteers with either 3 ml ropivacaine 0.75% (R), 3 ml ropivacaine 0.75% plus 20 µg dexmedetomidine (RpD), or 3 ml ropivacaine 0.75% plus systemic 20 µg dexmedetomidine (RsD). UNB-related sensory and motor scores were evaluated.

RESULTS

Sensory onset time of UNB was not different between the study groups, whereas motor onset time was significantly faster in Group RpD when compared with the other study groups [mean (sd)] [21 (15) vs 43 (25) min in Group RsD and 47 (36) min in Group R, P<0.05 Group RpD vs other groups]. The duration of sensory block was 350 (54) min in Group R, 555 (118) min in Group RpD, and 395 (40) min in Group RsD (P<0.01 Group RpD vs other groups, P<0.05 Group RsD vs Group R). Motor block duration was similar to the duration of sensory block.

CONCLUSIONS

A profound prolongation of UNB of ∼60% was detected with perineural dexmedetomidine when added to 0.75% ropivacaine. The systemic administration of 20 µg dexmedetomidine resulted in a prolongation of ∼10% during UNB with 0.75% ropivacaine. Eudra-CT No.: 2012-000030-19.