Experience with remifentanil in neonates and infants

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.

Efficacy and Safety Aspects of Remifentanil Sedation for Intubation in Neonates: A Retrospective Study

Objective: To evaluate the efficacy and safety of remifentanil as a premedication in neonates undergoing elective intubation. Study Design: This retrospective study focused on neonates admitted to the Neonatal Intensive Care Unit of Port-Royal, Paris Centre University Hospitals, France, between June 2016 and November 2017, who received remifentanil before an elective intubation. First, atropine (10 μg/kg) was administered intravenously as a bolus, followed by remifentanil, which was administrated continuously. The dose of remifentanil was reduced twice during the study period in order to administer the minimum effective dose and thus reduce possible adverse events. Results: Fifty-four neonates were exposed to remifentanil and atropine. The intubating conditions were excellent or good for 46 procedures (85%) and the median Acute Pain in Newborn Infants score was 2 (IQ 25-75: 0-5) before the sedation, 1 (0-2) during the laryngoscopy, and 0 (0-0) after the intubation. The intubation was successful at the first attempt for 18 patients (33%). Chest wall rigidity occurred in 6 procedures (11%), other respiratory problems in 5 (9%), and laryngospasm in 1 (2%). Some of the procedures were complicated by bradycardia (23%) or desaturation (37%). Conclusions: Remifentanil and atropine prior to intubation provided satisfactory intubating conditions in neonates. Nevertheless, severe adverse effects (such as chest wall rigidity) are a potential risk, possibly related to the total dose received. These data do not support the safety of using remifentanil alone prior to intubation in neonates.

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.

Population Pharmacokinetic Modeling of Remifentanil in Infants with Unrepaired Tetralogy of Fallot

BACKGROUND

Although there is literature suggesting that pathophysiologic changes in children with congenital heart disease alter the pharmacokinetics of anesthetics and may result in dosage adjustment, limited information exists regarding the pharmacokinetics of remifentanil in infants with unrepaired tetralogy of Fallot (TOF). The objectives of the current analysis were to characterize the population pharmacokinetics of remifentanil in infants, and to evaluate the effects of TOF on remifentanil's pharmacokinetics.

METHODS

Twenty-seven infants (16 with TOF and 11 with normal cardiac anatomy; aged 114-360 days) scheduled to undergo elective surgery under general anesthesia were recruited in the study. All children received remifentanil 1 μg/kg/min intravenously for anesthesia induction and early maintenance [until ~ 20 min before cardiopulmonary bypass (CPB) for patients with TOF]. Serial arterial blood samples were drawn and analyzed. Population pharmacokinetics of remifentanil was characterized using NONMEM software. The estimates were standardized to a 70-kg adult using a per-kilogram model.

RESULTS

A two-compartment disposition model adequately described the pharmacokinetics of remifentanil. Besides body weight, the introduction of any other covariates, including TOF status, did not improve the model significantly (P > 0.05). The population parameter estimates for systemic clearance (Cl₁) and inter-compartment clearances (Cl₂) were 6.03 × (WT/70 kg) and 1.23 × (WT/70 kg) L/min, respectively, and central volume of distribution (V₁) and peripheral volumes of distribution (V₂) were 19.6 × (WT/70 kg) and 21.7 × (WT/70 kg) L, respectively.

CONCLUSIONS

Unrepaired TOF does not change the pharmacokinetics of remifentanil, suggesting a similar dosage for infants with TOF compared to normal cardiac anatomy infants.

CLINICAL TRIAL REGISTRATION

The patient enrollment in this study started at 2012, so we do not have clinic trial number, but we still think this is a valuable research and hope it could be considered for publication.

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.

Insufficient Sedation and Severe Side Effects after Fast Administration of Remifentanil during INSURE in Preterm Newborns

BACKGROUND

Neonatal intubation is stressful and should be performed with premedication. In the case of an INSURE (intubation/surfactant/extubation) procedure a short duration of action of the premedication used is needed to facilitate fast extubation. Given its pharmacological profile, remifentanil seems a suitable candidate.

OBJECTIVES

The aim here was to evaluate the effect and side effects of remifentanil as a premedication for preterm neonates undergoing INSURE.

METHODS

A prospective, single-center study in a level III neonatal intensive care unit was conducted. The quality of sedation was assessed in preterm infants receiving remifentanil prior to intubation for the INSURE procedure. Intravenous remifentanil was administered quickly and followed by a saline flush in approximately 30 s. The quality of sedation was defined by a combination of adequate sedation score, good intubation conditions and absence of side effects.

RESULTS

The study was terminated after the inclusion of 14 patients because of the high rate of side effects and the poor intubation conditions. Adequate sedation was achieved in only 2 patients (14%). Six patients (43%) needed additional propofol to obtain adequate sedation. Chest wall rigidity occurred in 6 patients (43%).

CONCLUSIONS

The rapid administration of remifentanil provides insufficient sedation and is associated with a high risk of chest wall rigidity in preterm neonates.

Anesthetic use in newborn infants: the urgent need for rigorous evaluation

Approximately 1.5 million neonates receive general anesthesia each year for a surgical procedure. Despite this being an essential practice, a number of recent studies now indicate that anesthetic exposure could cause toxicity and neuronal apoptosis in the developing brain. This could potentially influence long-term neurodevelopmental outcome, especially premature infants in need of multiple surgical procedures. Most anesthetic drugs routinely administered to neonates have not been adequately tested for safety or efficacy. Given the number of confounders, dosing is often extrapolated from adults. This is concerning since many different drugs can be administered concurrently, with few of these agents actually approved for use by the Food and Drug Administration. Since 1997, legislation has been passed in the United States and abroad encouraging more drug investigation in infants and children. This has resulted in over 500 labeling changes to products regarding safety and efficacy in various pediatric age groups. However, only three drugs routinely used as anesthetic agents in newborn infants have had any updated labeling (none in very premature infants). This "off-label" use without adequate testing must be addressed. Therefore, more clinical trials of common anesthetic agents used alone and in combination in neonates are urgently needed.

Pain management in newborns

As a standard of care for preterm/term newborns effective pain management may improve their clinical and neurodevelopmental outcomes. Neonatal pain is assessed using context-specific, validated, and objective pain methods, despite the limitations of currently available tools. Therapeutic approaches reducing invasive procedures and using pharmacologic, behavioral, or environmental measures are used to manage neonatal pain. Nonpharmacologic approaches like kangaroo care, facilitated tucking, non-nutritive sucking, sucrose, and others can be used for procedural pain or adjunctive therapy. Local/topical anesthetics, opioids, NSAIDs/acetaminophen and other sedative/anesthetic agents can be incorporated into NICU protocols for managing moderate/severe pain or distress in all newborns.

A comparative study of two remifentanil doses for procedural pain in ventilated preterm infants: a randomized, controlled study*

OBJECTIVES

Remifentanil is an ultrashort-acting synthetic opioid, and the metabolism of which is not influenced by hepatic or renal function. This study aims to compare the efficacy of two remifentanil doses during procedures in ventilated preterm infants.

DESIGN

Prospective, randomized, double-blind, noninferiority trial.

SETTING

Neonatal ICU.

PATIENTS

Preterm infants who were supported by a mechanical ventilator with tracheal tube and requiring central venous access.

INTERVENTIONS

Two remifentanil dosages were administered in mechanically ventilated preterm infants during peripherally inserted central catheter insertion. Fourteen preterm infants were randomly assigned to low-dose (0.1 μg/kg/min) or high-dose (0.25 μg/kg/min) remifentanil infusion. The Premature Infant Pain Profile was used to score pain during the procedure, and changes in the Premature Infant Pain Profile score between needle puncture and baseline were analyzed to investigate the noninferiority of low-dose to high-dose remifentanil. Occurrence of cardiorespiratory complications was also recorded.

MEASUREMENTS AND MAIN RESULTS

The median gestational age (minimum, maximum) was 26 weeks (24, 31), and the median birth weight was 825 g (610, 1,280). Changes in Premature Infant Pain Profile in the high-dose and low-dose groups were 1.43 ± 3.10 and -0.60 ± 5.32, respectively. The difference in changes in the Premature Infant Pain Profile score between the high-dose and low-dose groups was -2.03 ± 4.13. The corresponding lower limit of one-tailed 97.5% CI was -7.24, below the noninferiority margin. Apneic events and bradycardia did not occur in the low-dose group; however, there were three episodes of apnea (42.9%) and one of bradycardia (14.3%) in the high-dose group (p = 0.683 and 0.366, respectively).

CONCLUSION

For mechanically ventilated preterm infants, the use of remifentanil at 0.25 μg/kg/min as an analgesic for short procedures represents a therapeutic option. Our pilot study suggests the need for larger randomized trials.

Sedation of newborn infants for the INSURE procedure, are we sure?

Background. Neonatal intubation is a stressful procedure that requires premedication to improve intubation conditions and reduce stress and adverse physiological responses. Premedication used during the INSURE (INtubation, SURfactant therapy, Extubation) procedure should have a very short duration of action with restoration of spontaneous breathing within a few minutes. Aims. To determine the best sedative for intubation during the INSURE procedure by systematic review of the literature. Methods. We reviewed all relevant studies reporting on premedication, distress, and time to restoration of spontaneous breathing during the INSURE procedure. Results. This review included 12 studies: two relatively small studies explicitly evaluated the effect of premedication (propofol and remifentanil) during the INSURE procedure, both showing good intubation conditions and an average extubation time of about 20 minutes. Ten studies reporting on fentanyl or morphine provided insufficient information about these items. Conclusions. Too little is known in the literature to draw a solid conclusion on which premedication could be best used during the INSURE procedure. Both remifentanil and propofol are suitable candidates but dose-finding studies to detect effective nontoxic doses in newborns with different gestational ages are necessary.

Remifentanil/midazolam versus fentanyl/midazolam for analgesia and sedation of mechanically ventilated neonates and young infants: a randomized controlled trial

PURPOSE

Common opioids for analgesia and sedation of mechanically ventilated infants may tend to accumulate and cause prolonged sedation with an unpredictable extubation time. Remifentanil is a promising option due to its unique pharmacokinetic properties, which seem to be valid in adults as well as in infants.

METHODS

In this double-blind, randomized, controlled trial mechanically ventilated neonates and young infants (<60 days) received either a remifentanil or fentanyl-based analgesia and sedation regimen with low dose midazolam. The primary endpoint of the trial was the extubation time following discontinuation of the opioid infusion. Secondary endpoints included efficacy and safety aspects.

RESULTS

Between November 2006 and March 2010, we screened 431 mechanically ventilated infants for eligibility. The intention to treat group included 23 infants who were assigned to receive either remifentanil (n = 11) or fentanyl (n = 12). Although this was designed as a pilot study, median extubation time was significantly shorter in the remifentanil group (80.0 min, IQR = 15.0-165.0) compared to the fentanyl group (782.5 min, IQR = 250.8-1,875.0) (p = 0.005). Remifentanil and fentanyl provided comparable efficacy with more than two-thirds of the measurements indicating optimal analgesia and sedation (66.4 and 70.2 %, respectively; p = 0.743). Overall, both groups had good hemodynamic stability and a comparably low incidence of adverse events.

CONCLUSIONS

As neonates and young infants have a decreased metabolism of common opioids like fentanyl and are more prone to respiratory depression, remifentanil could be the ideal opioid for analgesia and sedation of mechanically ventilated infants.

Remifentanil and propofol for weaning of mechanically ventilated pediatric intensive care patients

Mechanically ventilated pediatric intensive care patients usually receive an analgesic and sedative to keep them comfortable and safe. However, common drugs like fentanyl and midazolam have a long context sensitive half time, resulting in prolonged sedation and an unpredictable extubation time. Children often awake slowly and struggle against the respirator, although their respiratory drive and their airway reflexes are not yet sufficient for extubation. In this pilot study, we replaced fentanyl and midazolam at the final phase of the weaning process with remifentanil and propofol. Twenty-three children aged 3 months-10 years were enrolled. Remifentanil and propofol revealed throughout excellent or good weaning conditions with rapid transition from hypnosis to the development of regular spontaneous breathing, airway protective reflexes, and an appropriate level of alertness. Extubation time following discontinuation of the remifentanil and propofol infusion was only 24 ± 20 min (5-80 min). We conclude that the combination of remifentanil and propofol is a promising option to improve the weaning conditions of pediatric intensive care patients. Randomized controlled trials are needed to compare remifentanil and propofol with conventional weaning protocols.

Remifentanil in neonatal intensive care and anaesthesia practice

Remifentanil is a relatively new ultrashort action synthetic opioid. Studies on the use of remifentanil in neonatology have emerged demonstrating its effectiveness and safety in neonates. The present study describes the use of remifentanil in both full-term and premature newborns, highlighting the theoretical benefits for this population in terms of both neonatal intensive care and anaesthesia. A Medline search was undertaken of all reviews and reports about the use of remifentanil in neonates published between 1996 and 2009 using MeSH search terms 'remifentanil', 'analgesia', 'anaesthesia', 'newborn' and 'neonate'. The review points that remifentanil has been used with advantages in newborns including preterm neonates and even for foetal anaesthesia. It proved to be a good option to attenuate the hemodynamic/endocrine markers of stress related to surgery. Owing to its unique pharmacokinetic profile, shorter extubation times can be achieved what makes the drug also a good option for short duration invasive procedures in NICUs (InSurE). A concern on its use is that the hemodynamic response (hypotension) may become significant when the drug is associated to other drugs like sevoflurane.

CONCLUSION

Remifentanil seems to be an effective and safely used opioid for neonatal intensive care and anaesthesia practice.

Remifentanil for INSURE in preterm infants: a pilot study for evaluation of efficacy and safety aspects

AIM

To evaluate intubating conditions, extubation times and outcome in preterm infants receiving remifentanil as induction agent for the INSURE procedure.

METHODS

In twenty-one preterm infants of 29 to 32 weeks gestation and signs of respiratory distress, we utilized remifentanil as induction agent for the INSURE procedure. Following intubation and surfactant application, the infants were mechanically ventilated until respiratory drive was judged to be satisfactory for continuing CPAP therapy. Intubating conditions were classified by our own scoring system by rating limb movements, coughing and breathing. Heart rate, blood pressure and oxygen saturation were recorded during the entire INSURE procedure.

RESULTS

Remifentanil provided excellent or good intubating conditions in all patients. We observed no serious side effects after remifentanil infusion, in particular, no thorax rigidity, clinically significant bradycardia or arterial hypotension. Average extubation time after surfactant administration was 16.9 min (1-45 min); none of the infants had to be reintubated. Following extubation, the infants required only 3.3 days (1-8 days) of CPAP therapy. None exhibited serious complications of prematurity like periventricular leucomalacia, intraventricular haemorrhage >I degree, necrotizing enterocolitis or retinopathy.

CONCLUSION

In this pilot study, INSURE with remifentanil was associated with good intubating conditions and early extubation resulting in an excellent neonatal outcome.

Experience with remifentanil-sevoflurane balanced anesthesia for abdominal surgery in neonates and children less than 2 years

BACKGROUND

Few data report remifentanil use in the neonatal population. We described here our experience with remifentanil-sevoflurane balanced anesthesia in neonates and children less than 2 years who underwent general anesthesia for abdominal surgery.

METHODS

We retrospectively studied the pattern of remifentanil infusion associated with sevoflurane inhalation in preterm neonates (PTN; n = 18) (born before 37 weeks of gestation and <45 weeks of postmenstrual age), full-term neonates (FTN; n = 21) (born after 37 weeks of gestation and less than 29 days old) and older children up to 2 years (CUT; n = 24). We recorded heart rate (HR), mean arterial pressure (MAP), mean remifentanil dose and sevoflurane concentration before incision and at 5, 10, 20, 30, 45, 60, 90, and 105 min after incision.

RESULTS

We observed that remifentanil doses used during surgery were lower in PTN than in both FTN and CUT and lower in FTN than in CUT. This was because of a progressive decrease in remifentanil dose during anesthesia in PTN and FTN. Conversely, remifentanil doses increased in CUT during anesthesia. Sevoflurane concentrations were higher in CUT group than in PTN and FTN groups. MAP and HR did not vary in the three groups during anesthesia.

CONCLUSIONS

Remifentanil-sevoflurane anesthesia can be used for general anesthesia in neonates. We observed that anesthetists used lower doses of remifantanil and lower concentrations of sevoflurane in neonates compared with the older children.

Early awakening and extubation with remifentanil in ventilated premature neonates

BACKGROUND

Morphine is one of the most commonly used drugs for sedation and analgesia during mechanical ventilation, but its pharmacological profile has limitations, such as prolonged duration of action, especially in premature neonates. Because of its very short context-sensitive half-time, remifentanil has rapid onset and quickly decreases in plasma concentration after interrupting administration. The aim of the present study was to compare a continuous infusion of remifentanil and morphine during mechanical ventilation of premature neonates with respiratory distress syndrome (RDS).

METHODS

Twenty premature neonates (28-34 weeks) with RDS were randomized in a prospective double-blinded study to receive either a continuous infusion of morphine (n = 10) or remifentanil (n = 10) for mechanical ventilation. The length of time to awaken and extubate the neonate after interrupting opioid administration was recorded. We also recorded stress (COMFORT scale), pain response [Neonatal Infant Pain Scale (NIPS)], hemodynamic and ventilatory variables as well as adverse effects secondary to infusion of the specific opioid.

RESULTS

After terminating infusion, the length of time required to awaken and extubate the neonates was 18.9- and 12.1-fold longer, respectively, in the morphine group than in the remifentanil group. Both groups produced good quality sedation and analgesia as evaluated by the NIPS and COMFORT scores. No major side effects were observed.

CONCLUSIONS

Our results show an interesting potential for the use of remifentanil in premature neonates. Remifentanil allowed an adequate level of sedation and analgesia as well as rapid recovery after discontinuation. However, further properly designed clinical trials are needed before it can be generally recommended.