Efficacy and adverse effects of ketamine as an additive for paediatric caudal anaesthesia: a quantitative systematic review of randomized controlled trials

Ketamine versus midazolam as an adjuvant to peribulbar block using a single inferonasal injection in patients undergoing vitreoretinal surgery: A randomized controlled trial

INTRODUCTION AND OBJECTIVES

This study aimed to assess the safety and efficacy of midazolam and ketamine as adjuvants to the peribulbar block in vitreoretinal surgeries.

PATIENTS AND METHODS

This randomized controlled trial included 93 adult patients undergoing vitreoretinal surgeries performed with peribulbar anaesthesia. Patients were randomly allocated to 3 groups (31 participants each): control (standard anaesthetic mixture), midazolam (standard mixture + midazolam), and ketamine (standard mixture + ketamine). The primary outcomes were onset of globe akinesia and duration of analgesia. Secondary outcomes were duration of motor blockade, onset of corneal anaesthesia and lid akinesia, and changes in vital data (blood pressure, oxygen saturation, and pulse rate).

RESULTS

The ketamine group vs. the control and midazolam groups showed the most rapid onset of lid and globe akinesia (p < 0.001) and corneal anaesthesia (0.7 ± 0.2 vs. 1.5 ± 0.5 and 1.2 ± 0.4, respectively; p < 0.001) and the longest duration of both analgesia (3.7 ± 0.6 vs. 2.3 ± 0.4 and 3.1 ± 0.6, respectively; p < 0.001) and akinesia (3.8 ± 0.5 vs. 3.0 ± 0.4, and 3.7 ± 0.5, respectively; p < 0.001). The midazolam group showed better outcomes than controls, but the drug was less effective than ketamine. There were no significant differences in vital data among groups (p > 0.05).

CONCLUSIONS

Ketamine is an effective adjuvant for peribulbar blockade. It enhances both motor and sensory blockade by hastening onset and prolonging duration. These effects are desirable in lengthier ophthalmic procedures such as vitreoretinal surgeries. The effects of ketamine were superior to those of midazolam.

“K-Powder” Exposure during Adolescence Elicits Psychiatric Disturbances Associated with Oxidative Stress in Female Rats

Ketamine, also called ‘K-powder’ by abusers, an analog of phencyclidine, primarily acts as an antagonist of N-methyl-D-aspartic acid (NMDA) receptors, therapeutically used as an anesthetic agent. Ketamine also stimulates the limbic system, inducing hallucinations and dissociative effects. At sub-anesthetic doses, ketamine also displays hallucinatory and dissociative properties, but not loss of consciousness. These behavioral consequences have elicited its recreational use worldwide, mainly at rave parties. Ketamine is generally a drug of choice among teenagers and young adults; however, the harmful consequences of its recreational use on adolescent central nervous systems are poorly explored. Thus, the aim of the present study was to characterize the behavioral and biochemical consequences induced by one binge-like cycle of ketamine during the early withdrawal period in adolescent female rats. Adolescent female Wistar rats (n = 20) received intraperitoneally administered ketamine (10 mg/kg/day) for 3 consecutive days. Twenty-four hours after the last administration of ketamine, animals were submitted to behavioral tests in an open field, elevated plus-maze, and forced swimming test. Then, animals were intranasally anesthetized with 2% isoflurane and euthanized to collect prefrontal cortex and hippocampus to assess lipid peroxidation, antioxidant capacity against peroxyl radicals, reactive oxygen species, reduced glutathione, and brain-derived neurotrophic factor (BDNF) levels. Our results found that 24 h after recreational ketamine use, emotional behavior disabilities, such as anxiety- and depression-like profiles, were detected. In addition, spontaneous ambulation was reduced. These negative behavioral phenotypes were associated with evidence of oxidative stress on the prefrontal cortex and hippocampus.

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.

Comparing Effect of Adding Ketamine versus Dexmedetomidine to Bupivacaine in Pecs-ⅠⅠ Block on Postoperative Pain Control in Patients Undergoing Breast Surgery

BACKGROUND

Pecs-II block has previously and successfully demonstrated a good quality of perioperative analgesia for breast surgery.

OBJECTIVE

This study aimed to compare the quality of postoperative pain control when adding either ketamine or dexmedetomidine to bupivacaine 0.25% for Pecs-II block.

METHODS

This prospective randomized double-blind study was conducted on 159 female patients with American society of anesthesiologist (ASA) physical status class I-III scheduled to have modified radical mastectomy. Patients were randomly assigned into three groups. Each group included 53patients to receive ultrasound guided Pecs-II blocks with either 32 mL of 0.25% bupivacaine added to ketamine hydrochloride 1 mg/kg (BK group), 32 mL of 0.25%bupivacaine added to dexmedetomidine 1 ug/kg (BD group) or 32 mL of 0.25% bupivacaine only (B group).The primary outcome of this study was the total postoperative morphine consumption for the first 24 hours postoperatively. The time of the first request of analgesia, the pain scores at rest of ipsilateral arm, and the intra-operative fentanyl requirements, were the secondary outcome measures. Any side effects occurred were recorded.

RESULTS

The total postoperative morphine consumption was significantly lower in patients received bupivacaine with addition of either ketamine (BK group), (10.3±2.6 mg), or dexmedetomidine (BD group), (3.8±0.2 mg) respectively, versus patients received only bupivacaine (B group), (16.9±5.3 mg). Both ketamine (BK group) and dexmedetomidine (BD group) added to bupivacaine significantly prolonged the time to first analgesic request (16.7±4.5 h), (21.6±1.6 h) in both groups respectively compared to patients received bupivacaine alone (B group), (11.5±1.2 h).The pain score was variable between the three groups over different times during the first 24 hours postoperatively. There was no significant difference in perioperative hemodynamics, O2 saturation, sedation scores or side effects observed between the three groups. Patient satisfaction was reported to be the best in patients received dexmedetomidine added to bupivacaine than the other patients who received ketamine as an additive or those who received bupivacaine alone.

CONCLUSION

Adding dexmedetomidine to bupivacaine provides more effective postoperative pain control than adding ketamine during Pecs-II blocks for breast cancer surgery.

Review of clinical evidence of caudal block for postoperative analgesia in children with ketamine added local anesthetics

Background

Adding ketamine to local anesthetics used for caudal block in children is an emerging clinical practice. This review aims to resolve controversies related to this adjuvant for a caudal block in children who underwent sub-umbilical surgeries.

Methods

Between January 2010 and November 2021, PubMed, Cochrane Review, and Google Scholar were searched for a caudal block with ketamine added local anesthetics for children. After screening for eligibility and removing duplicates, 38,187 articles were found, 13 reviewed.

Discussion

Despite adding ketamine to local anesthetics used for a caudal block, it is a recent technique practiced worldwide. Ketamine showed equi-efficacious as other adjuvants used for the caudal block to control postoperative pain in children.

Conclusion

Ketamine with a 0.5 mg/kg dose is safe and effective to manage postoperative children's pain when used as an adjuvant to local anesthetics used for caudal block.

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Caudal additives prolong the length of analgesia than local anesthetics alone

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Ketamine is an alternative to be added for local anesthetics in a caudal block for children

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Ketamine in caudal block prolongs analgesia and reduces opioid intake.

Ambulatory Pain Management in the Pediatric Patient Population

PURPOSE OF REVIEW

Outpatient surgery in the pediatric population has become increasingly common. However, many patients still experience moderate to severe postoperative pain. A poor understanding of the extent of pain after pediatric ambulatory surgery and the lack of randomized control studies of pain management of the outpatient necessitate this review of scientific evidence and multimodal analgesia.

RECENT FINDINGS

A multimodal approach to pain management should be applied to the ambulatory setting to decrease postoperative pain. These include non-pharmacological techniques, multimodal pharmacologics, and neuraxial and peripheral nerve blocks. Postoperative pain management in pediatric ambulatory surgical patients remains suboptimal at most centers due to limited evidence-based approach to postoperative pain control. Pediatric ambulatory pain management requires a multipronged approach to address this inadequacy.

Bibliometric Analysis of Functional Magnetic Resonance Imaging Studies on Acupuncture Analgesia Over the Past 20 Years

Background

Researches on the central mechanisms of acupuncture analgesia have been widely conducted worldwide. However, there is no bibliometric analysis of functional magnetic resonance imaging (fMRI) studies on acupuncture analgesia. This study visualized the current status, hot spots and frontiers of fMRI studies on acupuncture analgesia in the past 20 years to provide a theoretical basis for its clinical application.

Methods

All publications were obtained from Science Citation Index-Expanded (SCI-E) of Web of Science (WOS). We used CiteSpace to analyze publications, journals, cited journals, authors, cited authors, institutions, countries, references, and keywords. We also analyzed collaborative network maps and co-occurrence network maps.

Results

We retrieved a total of 797 articles. Regarding the volume of publications, the total number of annual publications showed a fluctuating but overall increasing trend. Evidence-based Complementary and Alternative Medicine (21 articles) was the most productive journal, and Pain (225 articles) was the most cited journal. The most productive author was Qin W (16 articles), and the most co-cited author was Hui KKS (111). The most prolific institution and country were Massachusetts General Hospital (34 articles) and USA (212 articles). “Pain” was the top-ranked for keyword frequency and centrality. “Functional connectivity” was the frontier hotspot for 2018–2021.

Conclusion

First, fMRI researches on acupuncture analgesia involved several countries (regions) and institutions, mainly located in the USA, China and Korea, and most of them were universities. In addition, the USA was a major contributor in this field. Second, in terms of disciplinary distribution, the literatures were mainly from clinical neurology, neuroscience, and radiology nuclear medicine medical imaging. Third, the keyword co-occurrence analysis showed that the hot keywords included pain, fMRI, and lower back pain. Fourth, through keyword clustering analysis, the hot disease was found to be lower back pain, and the hot contents were acupuncture specificity and frequency specificity. Fifth, a timeline analysis of the references identified that chronic low back pain and specificity will remain a hot topic for future research.

Comeback of ketamine: resurfacing facts and dispelling myths

Initially known as CI-581, ketamine was first synthesized in 1962 as a replacement from phencyclidine. It has since been used as an anesthetic and analgesic. In addition, it has bronchodilating, sedative, and amnestic properties, preserving airway reflexes and sympathetic nervous system tone. Since the discovery of ketamine, it has been a major topic of discussion due to controversies regarding its usage in particular sets of patients. In the past 50 years, despite its potential benefits, it is not commonly used because of concerns of "emergence phenomenon," its use as a substance of abuse, and its systemic side effects. Since 2012, three World Health Organization reviews on ketamine have addressed its international control. Researchers have been studying this wonder drug for a decade worldwide. Many myths of ketamine regarding emergence phenomenon and its use in traumatic brain injury and open eye injury have been disproved in recent times. It is becoming popular in pre-hospital settings, critical care, emergency medicine, low-dose acute pain services, and adjuvant in regional anesthesia techniques. This review highlights the current consensus on the various applications of ketamine in the literature.

Efficacy and safety of caudal dexmedetomidine in pediatric infra-umbilical surgery: a meta-analysis and trial-sequential analysis of randomized controlled trials

BACKGROUND

Dexmedetomidine is used as a local-anesthetics adjuvant in caudal block to prolong analgesia in pediatric infra-umbilical surgery.

OBJECTIVE

We evaluated the analgesic efficacy and safety of the addition of caudal dexmedetomidine to local anesthetics (vs local anesthetics alone) in pediatric infra-umbilical surgery.

EVIDENCE REVIEW

We searched 10 databases for randomized controlled trials (RCTs) of pediatric patients undergoing infra-umbilical surgery, comparing caudal block with and without dexmedetomidine as local anesthetic adjuvant. We performed a frequentist random-effects meta-analysis (R statistical package). We analyzed continuous outcomes as a ratio of means (ROM) and dichotomous data as relative risk (RR), along with 95% CI. We included 19 RCTs (n=1190 pediatric patients) in the meta-analysis. The primary outcome was duration of analgesia (defined as 'the time from caudal injection to the time at which the study-specific pain score was greater than a cut-off threshold').

FINDINGS

Data from 19 included RCTs (n=1190) suggested that compared with control (mean duration 346 min), the addition of caudal dexmedetomidine significantly prolonged the duration of analgesia (ratio of means 2.14, 95% CI 1.83 to 2.49, p<0.001; 'moderate' evidence). Trial-sequential analysis showed adequate 'information size' for the primary outcome. Caudal dexmedetomidine also reduced the number of analgesic administrations ('low' evidence), total acetaminophen dose ('moderate' evidence) and the risk of emergence delirium ('moderate' evidence). There were no significant differences in adverse effects such as hypotension, bradycardia, post-operative nausea and vomiting, urinary retention and respiratory depression.

CONCLUSIONS

Our results suggest that the addition of dexmedetomidine to local anesthetic in caudal block significantly improves the duration of analgesia and reduces the analgesic requirements, while maintaining a similar risk-profile compared with local anesthetic alone. Further data on neurological safety are needed.

Efficacy of caudal vs intravenous administration of α2 adrenoceptor agonists to prolong analgesia in pediatric caudal block: A systematic review and meta-analysis

BACKGROUND

α₂ adrenoceptor agonists have been proposed as adjuncts to prolong analgesia in pediatric caudal block. The aim of this meta-analysis was to compare the analgesic efficacy of caudal vs intravenous α₂ adrenoceptor agonists during pediatric caudal block.

METHODS

A systematic search, data extraction, bias risk assessment, and pooled data analysis were performed following the PRISMA guidelines. All randomized controlled trials comparing caudal with intravenous α₂ adrenoceptor agonists in pediatric caudal block were included. Relative risk and weighted mean differences (the corresponding 95% confidence intervals) were calculated for dichotomous and continuous data, respectively. Trial sequential analyses were performed to evaluate the credibility of the meta-analysis.

RESULTS

A total of 244 patients in five trials were identified. Compared with the intravenous group (9.56 ± 4.23 hours), the time to the first rescue analgesia was prolonged in the caudal α₂ adrenoceptor agonists group (12.72 ± 5.99 hours) by a weighted mean difference of 2.98 hours [95% confidence interval: 0.59-5.36 hours; P = .01]. The number of children requiring rescue analgesia in the caudal group (64, 66.67%) was lower than that in the intravenous group (80, 81.63%) [relative risk = 0.82; 95% confidence interval: 0.69-0.97; P = .02]. These findings were also verified by trial sequential analysis. There were no significant differences in the side effects.

CONCLUSION

Caudal α₂ adrenoceptor agonists as adjuncts to local anesthetic during pediatric caudal block are more effective than intravenous injection. However, the results were affected by small sample size and significant heterogeneity.

Methodological tools and sensitivity analysis for assessing quality or risk of bias used in systematic reviews published in the high-impact anesthesiology journals

Background

A crucial element in the systematic review (SR) methodology is the appraisal of included primary studies, using tools for assessment of methodological quality or risk of bias (RoB). SR authors can conduct sensitivity analyses to explore whether their results are sensitive to exclusion of low quality studies or a high RoB. However, it is unknown which tools do SR authors use for assessing quality/RoB, and how they set threshold for quality/RoB in sensitivity analyses. The aim of this study was to assess quality/RoB assessment tools, the types of sensitivity analyses and quality/RoB thresholds for sensitivity analyses used within SRs published in high-impact pain/anesthesiology journals.

Methods

This was a methodological study. We analyzed SRs published from January 2005 to June 2018 in the 25% highest-ranking journals within the Journal Citation Reports (JCR) “Anesthesiology” category. We retrieved the SRs from PubMed. Two authors independently screened records, full texts, and extracted data on quality/RoB tools and sensitivity analyses. We extracted data about quality/RoB tools, types of sensitivity analyses and the thresholds for quality/RoB used in them.

Results

Out of 678 analyzed SRs, 513 (76%) reported the use of quality/RoB assessments. The most commonly reported tools for assessing quality/RoB in the studies were the Cochrane tool for risk of bias assessment (N = 251; 37%) and Jadad scale (N = 99; 15%). Meta-analysis was conducted in 451 (66%) of SRs and sensitivity analysis in 219/451 (49%). Most commonly, sensitivity analysis was conducted to explore the influence of study quality/RoB (90/219; 41%) on the results. Quality/RoB thresholds used for sensitivity analysis for those studies were clearly reported in 47 (52%) articles that used them. The quality/RoB thresholds used for sensitivity analyses were highly heterogeneous and inconsistent, even when the same tool was used.

Conclusions

A quarter of SRs reported using quality/RoB assessments, and some of them cited tools that are not meant for assessing quality/RoB. Authors who use quality/RoB to explore the robustness of their results in meta-analyses use highly heterogeneous quality/RoB thresholds in sensitivity analyses. Better methodological consistency for quality/RoB sensitivity analyses is needed.

An Update on the Basic and Clinical Science of Ketamine Analgesia

OBJECTIVE

In the context of the current opioid epidemic, there has been a renewed interest in the use of ketamine as an analgesic agent.

METHODS

We reviewed ketamine analgesia.

RESULTS

Ketamine is well-known as an antagonist for N-methyl-D-aspartate receptors. In addition, it can regulate the function of opioid receptors and sodium channels. Ketamine also increases signaling through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. These myriad of molecular and cellular mechanisms are responsible for a number of pharmacological functions including pain relief and mood regulation. Clinically, a number of studies have investigated the role of ketamine in the setting of acute and chronic pain, and there is evidence that ketamine can provide analgesia in a variety of pain syndromes.

DISCUSSION

In this review, we examined basic mechanisms of ketamine and its current clinical use and potential novel use in pain management.

Ketamine applications beyond anesthesia - A literature review

Ketamine's clinical use began in the 1970s. Physicians benefited from its safety and ability to induce short-term anesthesia and analgesia. The psychodysleptic effects caused by the drug called its further clinical use into question. Despite these unpleasant effects, ketamine is still applied in veterinary medicine, field medicine, and specialist anesthesia. Recent intensive research brought into light new possible applications of this drug. It began to be used in acute, chronic and cancer pain management. Most interesting reports come from research on the antidepressive and antisuicidal properties of ketamine giving hope for the creation of an effective treatment for major depressive disorder. Other reports highlight the possible use of ketamine in treating addiction, asthma and preventing cancer growth. Besides clinical use, the drug is also applied to in animal model of schizophrenia. It seems that nowadays, with numerous possible applications, the use of ketamine has returned; to its former glory. Nevertheless, the drug must be used with caution because still the mechanisms by which it executes its functions and long-term effects of its use are not fully known. This review aims to discuss the well-known and new promising applications of ketamine.

Effect of magnesium added to local anesthetics for caudal anesthesia on postoperative pain in pediatric surgical patients: A systematic review and meta-analysis with Trial Sequential Analysis

BACKGROUND

Magnesium has been investigated as an adjuvant for neuraxial anesthesia, but the effect of caudal magnesium on postoperative pain is inconsistent. The aim of this systematic review and meta-analysis was to evaluate the analgesic effect of caudal magnesium.

METHODS

We searched six databases, including trial registration sites. Randomized clinical trials reporting the effect of caudal magnesium on postoperative pain after general anesthesia were eligible. The risk ratio for use of rescue analgesics after surgery was combined using a random-effects model. We also assessed adverse events. The I2 statistic was used to assess heterogeneity. We assessed risk of bias with Cochrane domains. We controlled type I and II errors due to sparse data and repetitive testing with Trial Sequential Analysis. We assessed the quality of evidence with GRADE.

RESULTS

Four randomized controlled trials (247 patients) evaluated the need for rescue analgesics. In all four trials, 50 mg of magnesium was administered with caudal ropivacaine. The results suggested that the need for rescue analgesia was reduced significantly by caudal magnesium administration (risk ratio 0.45; 95% confidence interval 0.24-0.86). There was considerable heterogeneity as indicated by an I2 value of 62.5%. The Trial Sequential Analysis-adjusted confidence interval was 0.04-5.55, indicating that further trials are required. The quality of evidence was very low. The rate of adverse events was comparable between treatment groups.

CONCLUSION

Caudal magnesium may reduce the need for rescue analgesia after surgery, but further randomized clinical trials with a low risk of bias and a low risk of random errors are necessary to assess the effect of caudal magnesium on postoperative pain and adverse events.

TRIAL REGISTRATION

University Hospital Medical Information Network Clinical Trials Registry UMIN000025344.

Effect of an Intravenous Dexamethasone Added to Caudal Local Anesthetics to Improve Postoperative Pain: A Systematic Review and Meta-analysis With Trial Sequential Analysis

BACKGROUND

Caudal anesthesia has been used for postoperative pain control in pediatric surgical patients, but the duration of the analgesic effect is occasionally unsatisfactory. Intravenous steroids have been shown to be effective for postsurgical pain management after certain surgeries. The aim of this meta-analysis with trial sequential analysis (TSA) was to evaluate the analgesic effect of steroids in patients administered with caudal anesthesia.

METHODS

This study was a systematic review and meta-analysis. A search of published literature was conducted in the MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials databases and in trial registration sites. Randomized controlled trials that compared intravenous steroids with a placebo in pediatric patients who had received caudal anesthesia for surgery were included in the study. The primary outcomes from the present meta-analysis were the analgesic duration and the number of patients who required rescue analgesics. The analgesic duration and incidence of rescue use were summarized using mean difference or risk ratio with a 97.5% confidence interval (CI), respectively. If the 97.5% CI of the mean difference or risk ratio included a value of 0 or 1, respectively, we considered the difference not to be significant. We used the random effects model to combine the results. Heterogeneity was quantified with the I statistic. The quality of the trials was evaluated using the Cochrane methodology. Moreover, a TSA with a risk of type 1 error of 2.5% and power of 90% was performed. We established the minimum clinically meaningful difference of analgesic duration as 3 hours. The target sample size for meta-analysis was also calculated in the TSA. We also assessed adverse events.

RESULTS

Six trials with 424 patients were included; 211 patients received intravenous steroids. All trials compared dexamethasone of at least 0.5 mg/kg dose with a placebo. Dexamethasone prolonged the duration of caudal analgesia (mean difference, 244 minutes; 97.5% CI, 188-300). Heterogeneity was considerable with an I value of 94.8%. Quality of evidence was very low. The TSA suggested that only 17.0% of the target sample size had been reached, but the cumulative Z score crossed the trial sequential monitoring boundary to indicate a benefit. Rescue use was reported in 4 studies with 260 patients. Rescue use was not significantly reduced in the dexamethasone group (risk ratio, 0.53; 97.5% CI, 0.09-3.30; I, 98.7%). No increase in adverse events was reported.

CONCLUSIONS

Intravenous dexamethasone prolongs the analgesic duration of caudal anesthesia. Trials to investigate the effectiveness of a lower dose of the dexamethasone in prolonging analgesic effects would be of interest. Further trials with a low risk of bias are necessary.

Pharmacokinetics of S-ketamine during prolonged sedation at the pediatric intensive care unit

BACKGROUND

S-ketamine is the S(+)-enantiomer of the racemic mixture ketamine, an anesthetic drug providing both sedation and analgesia. In clinical practice, significant interpatient variability in drug effect of S-ketamine is observed during long-term sedation.

AIMS

The aim of this study was to evaluate the pharmacokinetic variability of S-ketamine in children aged 0-18 years during long-term sedation. Twenty-five children (median age: 0.42 years, range: 0.02-12.5) received continuous intravenous administrations of 0.3-3.6 mg/kg/h S-ketamine for sedation during mechanical ventilation. Infusion rates were adjusted to the desired level of sedation and analgesia based on the COMFORT-B score and Visual Analog Scale. Blood samples were drawn once daily at random time-points, and at 1 and 4 hours after discontinuation of S-ketamine infusion. Time profiles of plasma concentrations of S-ketamine and active metabolite S-norketamine were analyzed using nonlinear mixed-effects modeling software. Clearance and volume of distribution were allometrically scaled using the ¾ power model.

RESULTS

A total of 86 blood samples were collected. A 2-compartment and 1-compartment model adequately described the PK of S-ketamine and S-norketamine, respectively. The typical parameter estimates for clearance and central and peripheral volumes of distribution were: CL_S-KETAMINE =112 L/h/70 kg, V1_S-KETAMINE =7.7 L/70 kg, V2_S-KETAMINE =545L/70 kg, Q_S-kETAMINE =196 L/h/70 kg, and CL_{S-NORKETAMINE} =53 L/h/70 kg. Interpatient variability of CL_S-KETAMINE and CL_{S-NORKETAMINE} was considerable with values of 40% and 104%, respectively, leading to marked variability in steady-state plasma concentrations.

CONCLUSION

Substantial interpatient variability in pharmacokinetics in children complicates the development of adequate dosage regimen for continuous sedation.

Epidural analgesia in a paediatric teaching hospital: Trends, developments, and a brief review of literature

Introduction:

Continuous epidural analgesia has proven to be a good tool in the anaesthetist’s quest to provide excellent pain relief for an extended perioperative period. Pharmaceutical advances provide us with a larger array of both local anaesthetic (LA) drugs and additives that can prolong the duration or enhance the quality of analgesia, or both. The avoidance of LA toxicity is of paramount importance for safe prescription, especially in the high-risk neonatal and infant cohort, and all patients stand to benefit from ‘safer’ LA agents and adjuvants that promote the use of a lowered concentration of epidural LA infusions. We present a descriptive review of trends in epidural prescription and technique in our hospital.

Methods:

Our observational study was conducted over a period of 19 years in a tertiary paediatric teaching hospital. Prospectively collected data that included patient demographics, level of epidural catheter insertion, LA drugs and adjuvants used, as well as postoperative infusion rates, were then analysed retrospectively.

Results:

There was a decline in the use of paediatric epidural analgesia. Over the study period, we also observed a shift in preference of LAs and adjuvant drugs toward safer alternatives.

Conclusion:

Paediatric epidural analgesia is gradually being superseded by other analgesic modalities with superior safety profiles (e.g. peripheral neural blockade). However, indications remain for its continued use, and anaesthetists should be familiar with its technical aspects and pitfalls.

Interventions for postoperative pain in children: An overview of systematic reviews

The aim of this study was to conduct an overview of systematic reviews that summarizes the results about efficacy and safety from randomized controlled trials involving the various strategies used for postoperative pain management in children. We searched the Cochrane Database of Systematic Reviews, CINAHL, Database of Reviews of Effect, Embase, MEDLINE, and PsycINFO from the earliest date to January 24, 2016. This overview included 45 systematic reviews that evaluated interventions for postoperative pain in children. Out of 45 systematic reviews that investigated various interventions for postoperative pain in children, 19 systematic reviews (42%) presented conclusive evidence of efficacy. Positive conclusive evidence was reported in 18 systematic reviews (40%) for the efficacy of diclofenac, ketamine, caudal analgesia, dexmedetomidine, music therapy, corticosteroid, epidural analgesia, paracetamol, and/or nonsteroidal anti-inflammatory drugs and transversus abdominis plane block. Only one systematic review reported conclusive evidence of equal efficacy that involved a comparison of dexmedetomidine vs morphine and fentanyl. Safety of interventions was reported as conclusive in 14 systematic reviews (31%), with positive conclusive evidence for dexmedetomidine, corticosteroid, epidural analgesia, transversus abdominis plane block, and clonidine. Seven systematic reviews reported equal conclusive safety for epidural infusion, diclofenac intravenous vs ketamine added to opioid analgesia, bupivacaine, ketamine, paracetamol, and dexmedetomidine vs intravenous infusions of various opioid analgesics, oral suspension and suppository of diclofenac, only opioid, normal saline, no treatment, placebo, and midazolam. Negative conclusive statement for safety was reported in one systematic review for caudal analgesia vs noncaudal regional analgesia. More than half of systematic reviews included in this overview were rated as having medium methodological quality. Of 45 included systematic reviews, 10 were Cochrane reviews and they had higher methodological quality than non-Cochrane reviews. As evidence concerning efficacy and safety is inconclusive for most of the analyzed interventions, our review points out the need for more rigorous trials concerning pain management in children.

Adjuvants to local anesthetics: Current understanding and future trends

Although beneficial in acute and chronic pain management, the use of local anaesthetics is limited by its duration of action and the dose dependent adverse effects on the cardiac and central nervous system. Adjuvants or additives are often used with local anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and limiting the cumulative dose requirement of local anaesthetics. The armamentarium of local anesthetic adjuvants have evolved over time from classical opioids to a wide array of drugs spanning several groups and varying mechanisms of action. A large array of opioids ranging from morphine, fentanyl and sufentanyl to hydromorphone, buprenorphine and tramadol has been used with varying success. However, their use has been limited by their adverse effect like respiratory depression, nausea, vomiting and pruritus, especially with its neuraxial use. Epinephrine potentiates the local anesthetics by its antinociceptive properties mediated by alpha-2 adrenoreceptor activation along with its vasoconstrictive properties limiting the systemic absorption of local anesthetics. Alpha 2 adrenoreceptor antagonists like clonidine and dexmedetomidine are one of the most widely used class of local anesthetic adjuvants. Other drugs like steroids (dexamethasone), anti-inflammatory agents (parecoxib and lornoxicam), midazolam, ketamine, magnesium sulfate and neostigmine have also been used with mixed success. The concern regarding the safety profile of these adjuvants is due to its potential neurotoxicity and neurological complications which necessitate further research in this direction. Current research is directed towards a search for agents and techniques which would prolong local anaesthetic action without its deleterious effects. This includes novel approaches like use of charged molecules to produce local anaesthetic action (tonicaine and n butyl tetracaine), new age delivery mechanisms for prolonged bioavailability (liposomal, microspheres and cyclodextrin systems) and further studies with other drugs (adenosine, neuromuscular blockers, dextrans).

Evaluation of the effects of ketamine on spinal anesthesia with levobupivacaine or ropivacaine

Spinal anesthesia or regional anesthesia is a potent anesthetic procedure. Additional modalities have been sought to increase the duration of block in spinal anesthesia. Ketamine is an N-methyl-D-aspartate (NMDA) receptor blocker that has an anesthetic effect when injected intrathecally and has a synergic effect with bupivacaine. Ketamine also has potent analgesic properties. The present study investigated the effect of intrathecally administered ketamine on spinal anesthesia with levobupivacaine or ropivacaine. Sprague-Dawley rats at post-natal day 21 were exposed to spinal anesthesia with 0.5% levobupivacaine or 0.5% ropivacaine. Separate groups of rats were treated with intrathecal ketamine at a 5 or 10 mg/kg bodyweight dose along with ropivacaine or levobupivacaine. The thermal and mechanical withdrawal latencies of the animals were determined using hot plate and von Frey filaments, respectively. A rotarod apparatus was employed to assess the capacity of the rats to rotate the spindle at 24 h following anesthesia. The gait of the rat pups was also assessed. Intrathecal administration of ketamine resulted in dense blocks and extended the duration of spinal blocks as evidenced by thermal latencies and responses to von Frey filaments. The latency to fall was shorter in rats exposed to ketamine along with ropivacaine or levobupivacaine spinal anesthesia. The gait parameters were also more disturbed upon ketamine administration. In conclusion, ketamine administration with ropivacaine or levobupivacaine increased the intensity and duration of spinal blockade, thereby increasing the anesthetic effects.

Ketamine use in current clinical practice

After nearly half a century on the market, ketamine still occupies a unique corner in the medical armamentarium of anesthesiologists or clinicians treating pain. Over the last two decades, much research has been conducted highlighting the drug's mechanisms of action, specifically those of its enantiomers. Nowadays, ketamine is also being utilized for pediatric pain control in emergency department, with its anti-hyperalgesic and anti-inflammatory effects being revealed in acute and chronic pain management. Recently, new insights have been gained on ketamine's potential anti-depressive and antisuicidal effects. This article provides an overview of the drug's pharmacokinetics and pharmacodynamics while also discussing the potential benefits and risks of ketamine administration in various clinical settings.

Regional anaesthesia in neonates, infants and children: an educational review

Prophylactic analgesia with local anaesthesia is widely used in children and has a good safety record. Performing regional blocks in anaesthetised children is a safe and generally accepted practice. When compared with adults, lower concentrations of local anaesthetics are sufficient in children; the onset of a block occurs more rapidly but the duration is usually shorter. Local anaesthetics have a greater volume of distribution, a lower clearance and a higher free (non-protein-bound) fraction. The recommended maximum dose has to be calculated for every individual. Peripheral blocks provide analgesia restricted to the site of surgery, and some of them have a very long duration of action. Abdominal wall blocks, such as transverse abdominis plane or ilio-inguinal nerve block, should be performed with the aid of ultrasound. Caudal anaesthesia is the single most important technique. Ropivacaine 0.2% or levobupivacaine 0.125 to 0.175% at roughly 1 ml  kg⁻¹ is adequate for most indications. Clonidine and morphine can be used to prolong the duration of analgesia. Ultrasound is not essential for performing caudal blocks, but it may be helpful in case of anomalies suspected at palpation and for teaching purposes. The use of paediatric epidural catheters will probably decline in the future because of the potential complications.

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.

Caudal blockade for children undergoing infra-abdominal surgery

The assessment and management of pain in children can be complicated by their inability to communicate effectively; therefore, it is important that every attempt be made to circumvent the undertreatment of pain. Caudal blockade is associated with excellent pain relief and minimal side effects, and it is an established technique used in conjunction with general anesthesia for children undergoing infra-abdominal surgery. Available local anesthetic agents have a relatively short analgesic duration period, so anesthesia professionals often combine their use with adjuvant medications (eg, epinephrine, clonidine, fentanyl, morphine, preservative-free ketamine, neostigmine). Additional consideration should be given to intraoperative care, postoperative observation (eg, measuring sedation, motor blockade, postoperative nausea and vomiting, pain), and discharge instructions for the patient's caregiver.

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.

Postoperative pain management in children and infants: an update

Many factors contribute to suboptimal pain management in children. Current evidence suggests that severe pain in children has significant long-lasting effects, even more so than in adults. In particular, recent evidence suggests a lack of optimal postoperative pain management in children, especially following ambulatory surgery. This review provides simple guidelines for the management of postoperative pain in children. It discusses the long-term effects of severe pain and how to evaluate pain in both healthy and neurologically impaired children, including neonates. Currently available treatment options are discussed with reference to the efficacy and side effects of opioid and non-opioid and regional analgesic techniques. The impact of preoperative anxiety on postoperative pain, and the efficacy of some nonpharmacological techniques such as hypnosis or distraction, are also discussed. Finally, basic organizational strategies are described, aiming to promote safer and more efficient postoperative pain management in children.

From peripheral to central: the role of ERK signaling pathway in acupuncture analgesia

Despite accumulating evidence of the clinical effectiveness of acupuncture, its mechanism remains largely unclear. We assume that molecular signaling around the acupuncture needled area is essential for initiating the effect of acupuncture. To determine possible bio-candidates involved in the mechanisms of acupuncture and investigate the role of such bio-candidates in the analgesic effects of acupuncture, we conducted 2 stepwise experiments. First, a genome-wide microarray of the isolated skin layer at the GB34-equivalent acupoint of C57BL/6 mice 1 hour after acupuncture found that a total of 236 genes had changed and that extracellular signal-regulated kinase (ERK) activation was the most prominent bio-candidate. Second, in mouse pain models using formalin and complete Freund adjuvant, we found that acupuncture attenuated the nociceptive behavior and the mechanical allodynia; these effects were blocked when ERK cascade was interrupted by the mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) inhibitor U0126 (.8 μg/μL). Based on these results, we suggest that ERK phosphorylation following acupuncture needling is a biochemical hallmark initiating the effect of acupuncture including analgesia.

PERSPECTIVE

This article presents the novel evidence of the local molecular signaling in acupuncture analgesia by demonstrating that ERK activation in the skin layer contributes to the analgesic effect of acupuncture in a mouse pain model. This work improves our understanding of the scientific basis underlying acupuncture analgesia.

The effect of ketamine as an additive in epidural block on the intractable herpetic neuralgia: a case report

Ketamine has been shown to have analgesic effect by blocking N-methyl-D-aspartate receptor, thus preventing and reducing central sensitization caused by peripheral nociceptive stimulation. However, due to lack of knowledge about its safety and toxicity in the central nervous system, either epidural or intrathecal injection of ketamine still remains controversial. Here, we describe a case report of satisfactory pain relief after the addition of ketamine in epidural injection in a patient with severe herpes zoster pain that was refractory to conventional medication, intravenous opioids and continuous epidural block. This case indicates the viability of epidural ketamine injection in patients with intractable herpetic neuralgia.

Ketamine: use in anesthesia

The role of ketamine anesthesia in the prehospital, emergency department and operating theater settings is not well defined. A nonsystematic review of ketamine was performed by authors from Australia, Europe, and North America. Results were discussed among authors and the final manuscript accepted. Ketamine is a useful agent for induction of anesthesia, procedural sedation, and analgesia. Its properties are appealing in many awkward clinical scenarios. Practitioners need to be cognizant of its side effects and limitations.

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.