Postoperative pain

Ketamine in neuropsychiatric disorders: an update

The discovery of ketamine as a rapid-acting antidepressant led to a new era in the development of neuropsychiatric therapeutics, one characterized by an antidepressant response that occurred within hours or days rather than weeks or months. Considerable clinical research supports the use of-or further research with-subanesthetic-dose ketamine and its (S)-enantiomer esketamine in multiple neuropsychiatric disorders including depression, bipolar disorder, anxiety spectrum disorders, substance use disorders, and eating disorders, as well as for the management of chronic pain. In addition, ketamine often effectively targets symptom domains associated with multiple disorders, such as anxiety, anhedonia, and suicidal ideation. This manuscript: 1) reviews the literature on the pharmacology and hypothesized mechanisms of subanesthetic-dose ketamine in clinical research; 2) describes similarities and differences in the mechanism of action and antidepressant efficacy between racemic ketamine, its (S) and (R) enantiomers, and its hydroxynorketamine (HNK) metabolite; 3) discusses the day-to-day use of ketamine in the clinical setting; 4) provides an overview of ketamine use in other psychiatric disorders and depression-related comorbidities (e.g., suicidal ideation); and 5) provides insights into the mechanisms of ketamine and therapeutic response gleaned from the study of other novel therapeutics and neuroimaging modalities.

Nociception associated with pain/distress in young children sedated for dental treatment: a clinical study with objective and subjective measures

PURPOSE

To evaluate the association between children's pain/distress levels and patient characteristics (age, sex, history of dental pain), sedation type (level of sedation, sedative regimen), nociception and pain intensity reported by the parents in sedated children undergoing minimally invasive dental treatment.

METHODS

This clinical study evaluated secondary outcomes of an RCT that evaluated the efficacy of dexmedetomidine sedation with or without ketamine. Only children who had nociception levels recorded using the Analgesia Nociception Index (ANI) were included (0-100; 0 = highest nociception). FLACC scale (Face, Legs, Activity, Cry and Consolability) was used to assess children's pain/distress (0-10; 0 = no pain/distress). Parental proxy report of the child's pain intensity during the treatment was performed using the Visual Analogue Scale (VAS; 0-100; 0 = no pain). The association between ANI, children's age and sex, dental pain history, sedation level, sedative regimen, and VAS with the FLACC was verified using the generalised estimation equation analysis (alpha 0.05).

RESULTS

Participants were 31 children (51.6% boys) and their parents (90.3% mothers). Median FLACC was 3.3 (25th-75th percentiles 1.7-8.2), ANI 80.9 (74.7-85.8), and VAS 10 (1-23). FLACC associated with ANI (OR 0.96; 95% CI 0.93-0.99; p = 0.02), moderate sedation (0.13; 0.03-0.50; p = 0.003), and VAS (1.05; 1.01-1.10; p = 0.01).

CONCLUSION

Pain/distress was generally low and more prominent with minimal (versus moderate) sedation and higher nociception.

Adaptive randomised controlled non-inferiority multicentre trial (the Ketodex Trial) on intranasal dexmedetomidine plus ketamine for procedural sedation in children: study protocol

INTRODUCTION

Up to 40% of orthopaedic injuries in children require a closed reduction, almost always necessitating procedural sedation. Intravenous ketamine is the most commonly used sedative agent. However, intravenous insertion is painful and can be technically difficult in children. We hypothesise that a combination of intranasal dexmedetomidine plus intranasal ketamine (Ketodex) will be non-inferior to intravenous ketamine for effective sedation in children undergoing a closed reduction.

METHODS AND ANALYSIS

This is a six-centre, four-arm, adaptive, randomised, blinded, controlled, non-inferiority trial. We will include children 4-17 years with a simple upper limb fracture or dislocation that requires sedation for a closed reduction. Participants will be randomised to receive either intranasal Ketodex (one of three dexmedetomidine and ketamine combinations) or intravenous ketamine. The primary outcome is adequate sedation as measured using the Paediatric Sedation State Scale. Secondary outcomes include length of stay, time to wakening and adverse effects. The results of both per protocol and intention-to-treat analyses will be reported for the primary outcome. All inferential analyses will be undertaken using a response-adaptive Bayesian design. Logistic regression will be used to model the dose-response relationship for the combinations of intranasal Ketodex. Using the Average Length Criterion for Bayesian sample size estimation, a survey-informed non-inferiority margin of 17.8% and priors from historical data, a sample size of 410 participants will be required. Simulations estimate a type II error rate of 0.08 and a type I error rate of 0.047.

ETHICS AND DISSEMINATION

Ethics approval was obtained from Clinical Trials Ontario for London Health Sciences Centre and McMaster Research Ethics Board. Other sites have yet to receive approval from their institutions. Informed consent will be obtained from guardians of all participants in addition to assent from participants. Study data will be submitted for publication regardless of results.

TRIAL REGISTRATION NUMBER

NCT0419525.

Anaesthetic considerations for strabismus surgery in children and adults

Strabismus correction surgery is the most common eye operation in children. Adults have approximately a 4% lifetime risk of developing strabismus. Current treatment options include pharmacological injection of botulinum toxin or bupivacaine, conventional corrective surgery, adjustable suture surgery and minimally invasive surgery. Repeated surgery is common as each operation has a 60%-80% chance of successful correction. The benefits of early surgical correction in large-angle strabismus in children outweigh the risks of anaesthesia. General anaesthesia is suitable for patients of all age groups, for complicated or repeated surgery, and bilateral eye procedures. Regional ophthalmic block reduces the incidence of oculocardiac reflex and emergence agitation, and provides postoperative analgesia, but requires a cooperative patient as many experience discomfort. Topical anaesthesia has been used in pharmacological injection, minimally invasive surgery, uncomplicated conventional strabismus surgery and some adjustable suture strabismus surgery. Its use, however, is only limited to cooperative adult patients. Prophylactic antiemesis with both ondansetron and dexamethasone is recommended, especially for children. A multimodal analgesia approach, including paracetamol, intravenous non-steroidal anti-inflammatory drugs, topical local anaesthetic and minimal opioid usage, is recommended for postoperative analgesia, while a supplementary regional ophthalmic block is at the discretion of the team.

Nasal midazolam vs ketamine for neonatal intubation in the delivery room: a randomised trial

OBJECTIVE

To compare the effectiveness of sedation by intranasal administration of midazolam (nMDZ) or ketamine (nKTM) for neonatal intubation.

DESIGN

A multicentre, prospective, randomised, double-blind study.

SETTING

Delivery rooms at four tertiary perinatal centres in France.

PATIENTS

Preterm neonates with respiratory distress requiring non-emergent endotracheal intubation for surfactant instillation.

INTERVENTIONS

Treatment was randomly allocated, with each neonate receiving a bolus of 0.1 mL/kg in each nostril, corresponding to 0.2 mg/kg for nMDZ and 2 mg/kg for nKTM. The drug was repeated once 7 min later at the same dose if adequate sedation was not obtained.

MAIN OUTCOME MEASURES

Success was defined by adequate sedation before intubation and adequate comfort during the procedure. Intubation features, respiratory and cardiovascular events were recorded.

RESULTS

Sixty newborns, with mean (SD) gestational age and birth weight of 28 (3) weeks and 1100 (350) g, were included within the first 20 min of life. nMDZ was associated with a higher success rate (89% vs 58%; RR: 1.54, 95% CI 1.12 to 2.12, p<0.01) and shorter delays between the first dose and intubation (10 (6) vs 16 (8) min, p<0.01).Number of attempts, time to intubation, mean arterial blood pressure measures over the first 12 hours after birth and length of invasive ventilation were not different.

CONCLUSIONS

nMDZ was more efficient than nKTM to adequately sedate neonates requiring intubation in the delivery room. The haemodynamic and respiratory effects of both drugs were comparable.

CLINICAL TRIAL

This clinical trial was recorded on the National Library of Medicine registry (NCT01517828).

Ambulatory anesthetic care in children undergoing myringotomy and tube placement: current perspectives

PURPOSE

Myringotomy and tube placement is one of the most frequently performed ear, nose and throat (ENT) surgeries in the pediatric population. Effective anesthetic management is vital to ensuring successful ambulatory care and ensuring child and parental satisfaction.

RECENT FINDINGS

This review summarizes recently published studies about the long-term effects of general anesthesia in young children, novel approaches to preoperative fasting and simplified approaches to the assessment and management of emergence delirium (ED) and emergence agitation (EA). New developments in perioperative ambulatory care, including management of comorbidities and day care unit logistics, are discussed.

SUMMARY

Long-term follow-up of children exposed to general anesthesia before the age of 4 years has limited impact on academic achievement or cognitive performance and should not delay the treatment of common ENT pathology, which can impair speech and language development. A more liberal approach to fasting, employing a 6-4-0 regime allowing children fluids up until theater, may become an accepted practice in future. ED and EA should be discriminated from pain in recovery and, where the child is at risk of harm, should be treated promptly. Postoperative pain at home remains problematic in ambulatory surgery and better parental education is needed. Effective ambulatory care ultimately requires a well-coordinated team approach from effective preassessment to postoperative follow-up.

Accuracy of dispersing tramadol capsules for oral administration in young children

Tramadol is used in children aged <12 years for analgesia, particularly for those at risk of obstructive sleep apnoea undergoing adenotonsillectomy. The Australian Therapeutic Goods Administration have strongly recommended that oral tramadol drops (100 mg/ml) not be used in children <12 years because of the risk of inadvertent overdose. The total mass of drug in a 10 ml bottle is 1000 mg. The only alternative preparation available is a 50 mg capsule that requires dispersion of a capsule's contents should smaller doses be required. The accuracy of this preparation has not been assessed. Twenty surgical ward nurses were asked to prepare a 15 mg dose of tramadol from a 50 mg capsule. The dose was within ±5% of 15 mg in 13 cases (65%) and within ±10% in 19 cases (95%) (range 13.9-17.1 mg). Despite the dose variability of this method of preparing tramadol, we consider it sufficiently accurate for clinical use. We also consider it safe, as even at the highest dose prepared, the variability would be unlikely to contribute to clinically significant side-effects or toxicity. Moreover, the maximal dose that could be administered is limited to the size of the capsule (50 mg).

Postoperative pain assessment in children: a pilot study of the usefulness of the analgesia nociception index

BACKGROUND

The ability to perform objective pain assessment is very important in paediatric patients. The goal of this study was to investigate the relationship between the analgesia nociception index (ANI), which is based on the heart rate variability, and objective measurements of pain intensity in young or cognitively impaired children, after surgical or imaging procedures (control group) under general anaesthesia.

METHODS

On arrival in the recovery room and subsequently at 5-10 min intervals, the level of pain was rated using the FLACC pain scale (0-10). The ANI values (0-100; 0 indicating the worst pain) were recorded simultaneously. The area under the receiver operating characteristic curve (AUC) and grey zone approach were used to evaluate the performance of the ANI to detect patients with FLACC >4. Instantaneous ANI values were compared with ANI values averaged over 256 s periods of time.

RESULTS

All children in the surgical group (n=32) developed moderate-to-severe pain (FLACC >4). Children in the control group (n=30) exhibited minimal pain. Instantaneous ANI values were lower in children of the surgical group than in the control group [52 (sd16) vs 69 (16), P<0.001]. The AUC for the 256 s ANI recording period [0.94 (95% confidence interval 0.85-0.99)] was significantly higher than for instantaneous ANI (P<0.05). When measured for a period of 256 s, an ANI cut-off value of 56 (grey zone [58-60]) was most predictive of a FLACC ≥4.

CONCLUSIONS

The ANI may provide an objective measurement of acute postoperative pain, which is correlated with that measured on a FLACC scale in young or cognitively impaired children.

An audit of the use of intravenous ketamine for paediatric dental conscious sedation

AIM

An audit of the use of intravenous ketamine for the provision of conscious sedation in paediatric dentistry was carried out over a three-year period. AUDIT DESIGN: In the audit, 3,751 children were treated and an evaluation was carried out for safety and effectiveness of the drug and procedure, the quality of sedation and clinical procedures provided. In addition, the occurrence of any adverse effects and parental satisfaction were noted along with recovery. All children were ASA I and II, with an average age of 7.5 years. Children were referred because of management problems and were assessed to be at the high anxious level of four and five on the Venham scale. A weight related 0.25 mg/kg was initially administered with additional increments of 0.25 mg/kg given if required. The average total dose provided was 0.41 mg/kg.

RESULTS

The majority of children (76%) accepted all treatment with no problems, with 19% experiencing a small amount of resistance. Although a range of dental treatment was provided, it was mostly exodontias of carious primary dentition. A 27% response was provided assessing satisfaction which was very favourable. No adverse reactions occurred although the most common postoperative experience was nausea.

CONCLUSION

This audit demonstrated the safety and effectiveness of using intravenous ketamine for paediatric conscious sedation and implications for training and appropriate service delivery were discussed.

Postoperative Pain in Children After Dentistry Under General Anesthesia

The objective of this study was to determine the prevalence, severity, and duration of postoperative pain in children undergoing general anesthesia for dentistry. This prospective cross-sectional study included 33 American Society of Anesthesiology (ASA) Class I and II children 4-6 years old requiring multiple dental procedures, including at least 1 extraction, and/or pulpectomy, and/or pulpotomy of the primary dentition. Exclusion criteria were children who were developmentally delayed, cognitively impaired, born prematurely, taking psychotropic medications, or recorded baseline pain or analgesic use. The primary outcome of pain was measured by parents using the validated Faces Pain Scale-Revised (FPS-R) and Parents' Postoperative Pain Measure (PPPM) during the first 72 hours at home. The results showed that moderate-to-severe postoperative pain, defined as FPS-R ≥ 6, was reported in 48.5% of children. The prevalence of moderate-to-severe pain was 29.0% by FPS-R and 40.0% by PPPM at 2 hours after discharge. Pain subsided over 3 days. Postoperative pain scores increased significantly from baseline (P < .001, Wilcoxon matched pairs signed rank test). Moderately good correlation between the 2 pain measures existed 2 and 12 hours from discharge (Spearman rhos correlation coefficients of 0.604 and 0.603, P < .005). In conclusion, children do experience moderate-to-severe pain postoperatively. Although parents successfully used pain scales, they infrequently administered analgesics.

Ketofol dosing simulations for procedural sedation

BACKGROUND

Propofol mixed with racemic ketamine (or "ketofol") is popular for short procedural sedation and analgesia, yet the optimal combination is unknown. We aimed to determine a ketofol dosing regimen for short procedural sedation and analgesia of 5- to 20-minute duration in healthy patients (2-20 y).

METHODS

Pharmacokinetic-pharmacodynamic parameters were used to simulate drug concentration and effect profiles over time for different ketamine-to-propofol ratios (1:1-1:10). The target effect was a Children's Hospital of Wisconsin Sedation Scale score of less than 2. Combined effects were additive, with a propofol EC50 of 1.54 μg/mL (concentration required to produce hypnosis in 50% of patients), a ketamine EC50 of 0.44 μg/mL, and a slope of 5.3. Emergence threshold concentrations for propofol were 2.0 μg/mL in children and 1.8 μg/mL in adults as well as 0.5 μg/mL for ketamine (children and adults). The EC50 for propofol antiemesis was 0.343 μg/mL.

RESULTS

A ketamine-to-propofol ratio of 1:3 was the best combination for intermittent dosing, achieving a rapid onset of a Children's Hospital of Wisconsin Sedation Scale score of less than 2 within 1 minute and a time to emergence of 9 to 19 minutes in all ages after a 10-minute sedation. The optimal ketofol dosing in children (2-11 y) was 0.1 mL/kg initially followed by 0.05 mL/kg at 2 minutes and then 0.025 mL/kg for the subsequent doses. The adults (12-20 y) received 0.05 mL/kg of ketofol initially followed by 0.025 mL/kg for the subsequent doses. These regimens maintain a propofol antiemesis for 30 to 40 minutes after the last dose.

CONCLUSIONS

We suggest an optimal ratio of racemic ketamine to propofol of 1:3 for boluses during short procedures (5-20 minutes). A short ketofol infusion, ratio 1:4, is a suitable alternative to intermittent boluses. Ratios greater than 1:3 result in delayed recovery after 20 minutes.

Outpatient analgesia via paravertebral peripheral nerve block catheter and On-Q pump--a case series

Outpatient pain management after iliac crest bone harvesting can be challenging. We report the use of home L2 paravertebral nerve block catheter (L2PVBC) in a series of five children. The pain scores were low, and analgesic medication consumption was minimal. No complications were reported related with these catheters, and the patients reported very high pain control satisfaction scores. Outpatient L2PVBC can be beneficial as part of a multimodal analgesia strategy in selected pediatric patients.

Pharmacokinetic-pharmacodynamic modeling in acute and chronic pain: an overview of the recent literature

In acute and chronic pain, the objective of pharmacokinetic-pharmacodynamic (PKPD) modeling is the development and application of mathematical models to describe and/or predict the time course of the pharmacokinetics (PK) and pharmacodynamics (PD) of analgesic agents and link PK to PD. Performing population PKPD modeling using nonlinear mixed effects modeling allows, apart from the estimation of fixed effects (the PK and PD model estimates), the quantification of random effects as within- and between-subject variability. Effect-compartment models and mechanism-based biophase distribution models that incorporate drug-association and -dissociation kinetics are applied in PKPD modeling of pain treatment. Mechanism-based models enable the quantification of the rate-limiting factors in drug effect owing to drug distribution versus receptor kinetics (since receptor kinetics are nonlinear they are discernable from the linear effect-compartment kinetics). It is a helpful technique in understanding the complex behavior of specific analgesics, such as buprenorphine, but also morphine and its active metabolite morphine-6-glucuronide, especially with respect to the reversal of opioid-induced side effects, most importantly life-threatening respiratory depression. One approach in chronic pain studies is the application of mixture models. Mixture models do not necessarily need to take PK data into account and allow the objective differentiation of measured responses to analgesics into specific response subgroups, and as such, may play an important role in analyzing Phase I and II analgesia studies. Appropriate application of PKPD modeling leads to the improvement of current therapeutics with respect to dose design and outcome, understanding the interaction of analgesics within complex chronic pain disease processes and may play an important role in drug development. In the current article, novel observations using the aforementioned techniques on opioids, NSAIDs, epidural analgesia, ketamine and GABA-ergic drugs in acute and chronic pain are discussed.

Intranasal ketamine for procedural sedation in pediatric laceration repair: a preliminary report

OBJECTIVE

The objective of this study was to compare the efficacy of 3 doses of intranasal ketamine (INK) for sedation of children from 1 to 7 years old requiring laceration repair.

METHODS

This was a randomized, prospective, double-blind trial of children requiring sedation for laceration repair. Patients with simple lacerations were randomized by age to receive 3, 6, or 9 mg/kg INK. Adequacy and efficacy of sedation were measured with the Ramsay sedation score and the Observational Scale of Behavioral Distress-Revised. Serum ketamine and norketamine levels were drawn during the procedure. Sedation duration and adverse events were recorded.

RESULTS

Of the 12 patients enrolled, 3 patients achieved adequate sedation, all at the 9-mg/kg dose. The study was suspended at that time as per predetermined criteria.

CONCLUSIONS

Nine milligrams of INK per kilogram produced a significantly higher proportion of successful sedations than the 3- and 6-mg/kg doses.

Minimum alveolar concentration of desflurane with fentanyl for laryngeal mask airway removal in anesthetized children

BACKGROUND

Desflurane provides rapid emergence from anesthesia. So, it can be used for the removal of a laryngeal mask airway in an anesthetized child. We conducted this study to determine the optimal endtidal concentrations of desflurane with fentanyl that would allow removal of a laryngeal mask airway without airway complication in children.

METHODS

Thirty-six children of American Society of Anesthesiologist status I between 1 and 10 year of age undergoing ophthalmic surgery were recruited. General anesthesia was induced with sevoflurane and oxygen given via mask and laryngeal mask airway inserted. Anesthesia was maintained with desflurane in 100% oxygen. At the end of the surgery, predetermined target concentration was maintained for 10 min and laryngeal mask airway removed. Each target concentration at the time of removal was predetermined by the Dixon up-down method (with 0.5% as a step size) starting at 5% endtidal concentration. A removal accomplished without coughing, teeth clenching, gross purposeful movement, breath holding, or laryngospasm, during or within 1 min after removal, was considered to be successful.

RESULTS

Endtidal concentration of desflurane required for successful laryngeal mask airway removal in 50% (ED50) was 3.56% desflurane (95% confidence limits, 3.22-3.87%) along with fentanyl.

CONCLUSION

Removal of laryngeal mask airway can be safely accomplished without coughing, moving, or any other airway complications at 3.57% endtidal concentrations of desflurane with fentanyl in 50% of anesthetized children.

Pharmacotherapy for acute pain in children: current practice and recent advances

INTRODUCTION

Acute pain in children may be undertreated. Improved understanding of developmental neurobiology and paediatric pharmacokinetics should facilitate better management of pharmacotherapy. The objective of this review is to discuss current paediatric practice and recent advances with these analgesic agents by using an evidence-based approach.

AREAS COVERED

Using PubMed an extensive literature review was conducted on the commonly used analgesic agents in children from 2000 to April 2010.

EXPERT OPINION

A multimodal analgesic regimen provides better pain control and functional outcome in children. The choice of pharmacological treatment is determined by the severity and type of pain. However, more research and evidence is required to determine the optimal drug combinations.

Anesthetic management for pediatric strabismus surgery: Continuing professional development

PURPOSE

Strabismus surgery is one of the most common pediatric ophthalmic procedures. The purpose of this continuing professional development module is to update physicians on the anesthetic considerations of pediatric patients undergoing strabismus surgery.

PRINCIPAL FINDINGS

The preoperative assessment is important, as patients undergoing strabismus surgery may have an associated neuromuscular disorder, congenital syndrome, or cardiac disease. Malignant hyperthermia is no longer considered as being an issue associated with strabismus. The laryngeal mask airway is used frequently and has been shown as being associated with a low incidence of complications in strabismus surgery. The anesthesia technique can be adapted to decrease the incidence of the oculocardiac reflex and the oculorespiratory reflex, and the use of anticholinergic prophylaxis remains debatable. Since patients are at high risk for postoperative nausea and vomiting (PONV), combination anti-emetic therapy is recommended using dexamethasone and ondansetron. Metoclopramide was not found to provide additional benefit when combined with other anti-emetics. Droperidol is effective, but there remains a black box warning for dysrhythmias. Effective analgesics in this patient population include acetaminophen, nonsteroidal anti-inflammatory drugs, peribulbar blocks, and subtenon blocks. Topical tetracaine drops have demonstrated mixed results, and topical nonsteroidal anti-inflammatory drops were found not to be effective. The use of opioids should be minimized due to the increased incidence of PONV.

CONCLUSIONS

To provide optimal care for the pediatric patient undergoing strabismus surgery, it is important to understand the unique anesthetic considerations for strabismus surgery and to appreciate how each decision regarding the anesthetic technique can alter these considerations.