Remifentanil: applications in neonates

Challenges of pediatric pharmacotherapy: A narrative review of pharmacokinetics, pharmacodynamics, and pharmacogenetics

PURPOSE

Personalized pharmacotherapy, including for the pediatric population, provides optimal treatment and has emerged as a major trend owing to advanced drug therapeutics and diversified drug selection. However, it is essential to understand the growth and developmental characteristics of this population to provide appropriate drug therapy. In recent years, clinical pharmacogenetics has accumulated knowledge in pediatric pharmacotherapy, and guidelines from professional organizations, such as the Clinical Pharmacogenetics Implementation Consortium, can be consulted to determine the efficacy of specific drugs and the risk of adverse effects. However, the existence of a large knowledge gap hinders the use of these findings in clinical practice.

METHODS

We provide a narrative review of the knowledge gaps in pharmacokinetics (PK) and pharmacodynamics (PD) in the pediatric population, focusing on the differences from the perspective of growth and developmental characteristics. In addition, we explored PK/PD in relation to pediatric clinical pharmacogenetics.

RESULTS

The lack of direct and indirect biomarkers for more accurate assessment of the effects of drug administration limits the current knowledge of PD. In addition, incorporating pharmacogenetic insights as pivotal covariates is indispensable in this comprehensive synthesis for precision therapy; therefore, we have provided recommendations regarding the current status and challenges of personalized pediatric pharmacotherapy. The integration of clinical pharmacogenetics with the health care system and institution of educational programs for health care providers is necessary for its safe and effective implementation. A comprehensive understanding of the physiological and genetic complexities of the pediatric population will facilitate the development of effective and personalized pharmacotherapeutic strategies.

Low-Dose Remifentanil in Preterm Cesarean Section with General Anesthesia: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVE

The conventional technique of general anesthesia induction during a Cesarean section involves the use of opioids only after cord clamping. We hypothesized that the use of remifentanil before cord clamping might reduce the use of maternal supplemental anesthetic agents and improve the maternal hemodynamics status and neonatal adaptation of the preterm neonate.

METHODS

A phase III, double-blind, randomized, placebo-controlled, hospital-based trial enrolled parturients undergoing a Cesarean section under general anesthesia before 37 weeks of gestation. Block randomization allocated pregnant women to remifentanil or placebo. The primary outcome was the rate of newborns with Apgar scores < 7 at 5 min. Secondary outcomes were maternal hemodynamic parameters, complications of anesthetic induction, use of adjuvant anesthetic agents, neonatal respiratory distress, umbilical cord pH, and lactate levels.

RESULTS

A total of 52/55 participants were analyzed, comprising 27 women in the remifentanil group and 25 in the placebo group. Nine of 27 (33.3%) neonates had an Apgar score < 7 at 5 min in the remifentanil group versus 11/25 (44.0%) in the placebo group (p = 0.45, odds ratio = 0.66, 95 confidence interval 0.20-2.18). The blood cord gases, cognitive, behavior, sensory, sleeping, and feeding scores at 1 and 2 years of corrected age were not different. For the mothers, hemodynamic parameters, anesthesia duration, and the cumulative treatment dose until cord clamping did not differ between the groups.

CONCLUSIONS

The use of a low dose of remifentanil before cord clamping for a Cesarean section appears to be safe both for the mother and the preterm newborn, but it does not improve maternal or neonatal outcomes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT02029898.

Congenital Myasthenic Syndrome With Malignant Hyperthermia Susceptibility in a Child Undergoing Adenotonsillectomy for Obstructive Sleep Apnea: A Case Report

Congenital myasthenic syndromes are rare genetic diseases involving pathologic proteins in the neuromuscular junction. Malignant hyperthermia susceptibility is a genetic disorder involving a hypermetabolic response to volatile anesthetics and depolarizing neuromuscular blocking agents. We present the first reported case of a 3-year-old boy with both congenital myasthenic syndrome and malignant hyperthermia susceptibility, resulting from a mutation in the ryanodine receptor type 1 gene, who underwent an adenotonsillectomy for severe obstructive sleep apnea. We discuss the anesthetic challenges in navigating these 3 comorbidities in the setting of airway surgery.

[Safe and Appropriate Pharmacotherapy in Paediatric Anaesthesia]

Safe and appropriate pharmacotherapy in children requires knowledge of age-group-specific features regarding pharmacology and drug dosing. In addition, aspects of medication safety must be considered. This review highlights basic principles and discusses key facts; further research in paediatric databases is recommended (www.kinderformularium.de).

Stimulating and maintaining spontaneous breathing during transition of preterm infants

Most preterm infants breathe at birth, but need additional respiratory support due to immaturity of the lung and respiratory control mechanisms. To avoid lung injury, the focus of respiratory support has shifted from invasive towards non-invasive ventilation. However, applying effective non-invasive ventilation is difficult due to mask leak and airway obstruction. The larynx has been overlooked as one of the causes for obstruction, preventing face mask ventilation from inflating the lung. The larynx remains mostly closed at birth, only opening briefly during a spontaneous breath. Stimulating and supporting spontaneous breathing could enhance the success of non-invasive ventilation by ensuring that the larynx remains open. Maintaining adequate spontaneous breathing and thereby reducing the need for invasive ventilation is not only important directly after birth, but also in the first hours after admission to the NICU. Respiratory distress syndrome is an important cause of respiratory failure. Traditionally, treatment of RDS required intubation and mechanical ventilation to administer exogenous surfactant. However, new ways have been implemented to administer surfactant and preserve spontaneous breathing while maintaining non-invasive support. In this narrative review we aim to describe interventions focused on stimulation and maintenance of spontaneous breathing of preterm infants in the first hours after birth.

Dexmedetomidine Compared to Remifentanil Infusion as Adjuvant to Sevoflurane Anesthesia during Laparoscopic Sleeve Gastrectomy

Objectives

Evaluation of postoperative (PO) analgesic effects of intraoperative (IO) Dexmedetomidine (DEX) compared to remifentanil (REMI) infusions during sevoflurane anesthesia for laparoscopic gastric sleeve surgery.

Patients and Methods

One hundred and thirty-two patients with body mass index >35 kg.m^-2 and ASA Grades II or III were randomly divided into group R received REMI infusion (6-18 μg.kg^-1.h^-1) and Group D received DEX infusion (0.2-0.5 μg.kg^-1.h^-1) after tracheal intubation till before stoppage of inhalational anesthetic. Heart rate and mean arterial pressure were noninvasively monitored during and after surgery. Emergence time, time until postanesthetic care unit transfer, and total operating room (OR) time was recorded. PO shoulder-tip pain and wound pain scores were recorded and rescue analgesia was provided as 50 mg pethidine intramuscular injection. Occurrence of PO nausea and vomiting (PONV) and frequency of the need for antiemetic therapy were recorded. Primary study outcome was the ability of the study infusions to reduce consumption of PO pethidine down to one dose during 24-hr PO.

Results

IO use of REMI or DEX infusion allowed hemodynamic control to surgical stresses with nonsignificant difference between both infusions. REMI infusion insured significantly rapid recovery and short OR times but required larger volume of sevoflurane during surgery and proper PO follow-up for pain and PONV. DEX infusion significantly improved control of PO pain with a larger number of patient requested rescue analgesia only once, reduced the dose of PO analgesia, reduced the frequency of PONV, and the need for antiemetic therapy.

Conclusion

REMI or DEX infusion as IO adjuvant to general anesthesia is appropriate option to achieve hemodynamic control of surgical stresses and to improve perioperative outcomes. REMI infusion may be preferred for its induced rapid recovery and short OR time, whereas DEX infusion may be chosen for its improved control of PO pain and reduction of PO analgesia and frequency of PONV.

Pharmacokinetics of Fentanyl and Its Derivatives in Children: A Comprehensive Review

Fentanyl and its derivatives sufentanil, alfentanil, and remifentanil are potent opioids. A comprehensive review of the use of fentanyl and its derivatives in the pediatric population was performed using the National Library of Medicine PubMed. Studies were included if they contained original pharmacokinetic parameters or models using established routes of administration in patients younger than 18 years of age. Of 372 retrieved articles, 44 eligible pharmacokinetic studies contained data of 821 patients younger than 18 years of age, including more than 46 preterm infants, 64 full-term neonates, 115 infants/toddlers, 188 children, and 28 adolescents. Underlying diagnoses included congenital heart and pulmonary disease and abdominal disorders. Routes of drug administration were intravenous, epidural, oral-transmucosal, intranasal, and transdermal. Despite extensive use in daily clinical practice, few studies have been performed. Preterm and term infants have lower clearance and protein binding. Pharmacokinetics was not altered by chronic renal or hepatic disease. Analyses of the pooled individual patients' data revealed that clearance maturation relating to body weight could be best described by the Hill function for sufentanil (R ² = 0.71, B _max 876 mL/min, K ₅₀ 16.3 kg) and alfentanil (R ² = 0.70, B _{max (fixed)} 420 mL/min, K ₅₀ 28 kg). The allometric exponent for estimation of clearance of sufentanil was 0.99 and 0.75 for alfentanil clearance. Maturation of remifentanil clearance was described by linear regression to bodyweight (R ² = 0.69). The allometric exponent for estimation of remifentanil clearance was 0.76. For fentanyl, linear regression showed only a weak correlation between clearance and bodyweight in preterm and term neonates (R ² = 0.22) owing to a lack of data in older age groups. A large heterogeneity regarding study design, clinical setting, drug administration, laboratory assays, and pharmacokinetic estimation was observed between studies introducing bias into the analyses performed in this review. A limitation of this review is that pharmacokinetic data, based on different modes of administration, dosing schemes, and parameter estimation methods, were combined.

Use of remifentanil in general anesthesia for neonatal non-cardiac surgery: a case series

OBJECTIVE

This case series aimed to summarize our experience in usage of remifentanil in neonates undergoing non-cardiac surgery.

BACKGROUND

Physiology of neonates and infants is different from that of adults. Immaturity of their vital organ systems narrows a safety margin of perioperative management including anesthesia. Remifentanil has favorable characteristics for pediatrics such as short duration of action and rapid elimination. Although remifentanil was introduced into clinical practice since 1996, its application to neonatal anesthesia has not been validated yet.

METHODS

This is a 14-month retrospective case series of neonates receiving remifentanil during non-cardiac surgery at a tertiary care pediatric hospital in Japan. Patients' characteristics, intraoperative data, and complications were retrieved from medical records.

RESULTS

A total of 68 neonates underwent non-cardiac surgery under general anesthesia, of whom 48 received remifentanil. Infusion rate was 0.14 (0.04-0.35) mcg/kg/min (median, range). No intractable adverse events including postoperative apnea were detected.

CONCLUSION

Remifentanil is generally feasible to neonatal surgical population.

General Anesthesia With Dexmedetomidine and Remifentanil in a Neonate During Oracotomy and Resection of a Congenital Cystic Adenomatoid Malformation

Based on animal data, concern has been expressed regarding the potential deleterious neurocognitive effects of general anesthesia during infancy and early life. Although there are no definitive data to prove this effect, the neonatal period has been suggested to be the most vulnerable period. While various inhaled and intravenous anesthetic agents have been implicated, dexmedetomidine and the opioids may be devoid of such effects. However, there are limited data regarding the combination of these agents during neonatal surgery and anesthesia. We present the use of these agents in combination with epidural anesthesia for postoperative analgesia in a 1-day-old neonate during thoracotomy and excision of a congental cystic adenomatoid malformation. Previous reports of the use of this unique combination of agents are reviewed and their role in this scenario discussed.

Correction to: Pharmacokinetics of Fentanyl and Its Derivatives in Children: A Comprehensive Review

Fentanyl and its derivatives sufentanil, alfentanil, and remifentanil are potent opioids. A comprehensive review of the use of fentanyl and its derivatives in the pediatric population was performed using the National Library of Medicine PubMed. Studies were included if they contained original pharmacokinetic parameters or models using established routes of administration in patients younger than 18 years of age. Of 372 retrieved articles, 44 eligible pharmacokinetic studies contained data of 821 patients younger than 18 years of age, including more than 46 preterm infants, 64 full-term neonates, 115 infants/toddlers, 188 children, and 28 adolescents. Underlying diagnoses included congenital heart and pulmonary disease and abdominal disorders. Routes of drug administration were intravenous, epidural, oral-transmucosal, intranasal, and transdermal. Despite extensive use in daily clinical practice, few studies have been performed. Preterm and term infants have lower clearance and protein binding. Pharmacokinetics was not altered by chronic renal or hepatic disease. Analyses of the pooled individual patients' data revealed that clearance maturation relating to body weight could be best described by the Hill function for sufentanil (R ² = 0.71, B _max 876 mL/min, K ₅₀ 16.3 kg) and alfentanil (R ² = 0.70, B _{max (fixed)} 420 mL/min, K ₅₀ 28 kg). The allometric exponent for estimation of clearance of sufentanil was 0.99 and 0.75 for alfentanil clearance. Maturation of remifentanil clearance was described by linear regression to bodyweight (R ² = 0.69). The allometric exponent for estimation of remifentanil clearance was 0.76. For fentanyl, linear regression showed only a weak correlation between clearance and bodyweight in preterm and term neonates (R ² = 0.22) owing to a lack of data in older age groups. A large heterogeneity regarding study design, clinical setting, drug administration, laboratory assays, and pharmacokinetic estimation was observed between studies introducing bias into the analyses performed in this review. A limitation of this review is that pharmacokinetic data, based on different modes of administration, dosing schemes, and parameter estimation methods, were combined.

The efficacy of dexmedetomidine-remifentanil versus dexmedetomidine-propofol in children undergoing flexible bronchoscopy: A retrospective trial

Flexible bronchoscopy has been more and more used for diagnosis and management diseases of respiratory system in pediatrics. Previous studies have reported that remifentanil (RF) and propofol are safe and effective for flexible bronchoscopy in adults, however, there have no trials evaluate the efficacy of DEX-RF versus dexmedetomidine-propofol in children undergoing flexible bronchoscopy.We divided 123 children undergoing flexible bronchoscopy with DEX-RF or dexmedetomidine-propofol into 2 groups: Group DR (n = 63, DEX infusion at 1.0 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; RF infusion at 1.0 μg kg for 5 minutes, then adjusted to 0.05-0.2 μg kg min), Group DP (n = 60, DEX infusion at 1.0 μg kg for 10 minutes, then adjusted to 0.5-0.7 μg kg h; propofol infusion at 10 μg kg for 5 minutes, then adjusted to 0.05-0.1 μg kg min). Ramsay sedation scale of the 2 groups was maintained at 3. Anesthesia onset time; total number of intraoperative patient movements; hemodynamics; total cumulative dose of DEX; amount of and time to first-dose rescue midazolam and lidocaine; postoperative recovery time; adverse events; and bronchoscopist satisfaction score were recorded.Anesthesia onset time was significantly shorter in DP (8.22 ± 2.48 vs 12.25 ± 6.43 minutes, respectively, for DP, DR, P = 0.015). The perioperative hemodynamic profile was more stable in DR than DP group. More children moved during flexible bronchoscopy in DP group (P = 0.009). Total dose of rescue midazolam and lidocaine was significantly higher in DR than in DP (P < 0.001). Similarly, the time to first dose of rescue midazolam and lidocaine was significantly longer in DP than in DR (P < 0.001). Total cumulative dose of DEX was more in DR than DP group (P < 0.001). The time to recovery for discharge from the postanesthesia care unit (PACU) was significantly shorter in DP than in DR group (P < 0.001). The bronchoscopist-satisfaction scores were higher for DR than DP (P = 0.036). There were significant differences between the 2 groups in terms of the overall incidence of hypertension, tachycardia, and hypoxemia (P < 0.05).Although underwent longer recovery time and more incidence of rescue scheme, DEX-RF resulted in more stable hemodynamic profiles and bronchoscopist-satisfaction scores, lesser patient movements, and can hence be more effectively used in children undergoing flexible bronchoscopy than dexmedetomidine-propofol.

Sedation with a remifentanil infusion to facilitate rapid awakening and tracheal extubation in an infant with a potentially compromised airway

Sedation is generally required during endotracheal intubation and mechanical ventilation in infants and children. While there are many options for the provision of sedation, the most commonly used agents such as midazolam and fentanyl demonstrate a context-sensitive half-life, which may result in a prolonged effect when these agents are discontinued following a continuous infusion. We present a 20-month-old infant who required endotracheal intubation due to respiratory failure following seizures. At the referring hospital, multiple laryngoscopies were performed with the potential for airway trauma. To maximize rapid awakening and optimize respiratory function surrounding tracheal extubation, sedation was transitioned from fentanyl and midazolam to remifentanil for 18–24 hours prior to tracheal extubation. The unique pharmacokinetics of remifentanil are presented in this study, its use in this clinical scenario is discussed, and its potential applications in the pediatric intensive care unit setting are reviewed.