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

Esketamine: Less Drowsiness, More Analgesia

Racemic ketamine is a 1:1 mixture of 2 enantiomers that turn light in opposite direction: Dextrorotatory esketamine is approximately 4 times more affine for the N-methyl-D-aspartate (NMDA) receptor than levorotatory arketamine, which may explain why esketamine is about twice as potent as an analgesic and anesthetic as the racemate. Esketamine has attracted renewed interest in view of the opioid crisis, racemic ketamine's abuse, and esketamine's approval for expanded use. We evaluated the anesthesia literature concerning mental, cardiovascular, cerebral, and antinociceptive effects of esketamine published in English between 1980 and 2022. The review shows that esketamine and racemic ketamine are not "the same" at clinically equivalent analgesic and anesthetic dose: Psychomimetic effects seem to be essentially related to NMDA receptor blockade and esketamine is not devoid of unwanted mental impact. However, it probably involves less cholinergic inhibition. Cognitive disturbances during arousal, awakening, and recovery from the drug are less, and less pronounced with esketamine. The drug allows for an approximately 50% dose reduction in anesthesia and analgesia which goes along with a higher clearance and shorter recovery time as compared to racemic ketamine. In comparison of esketamine with placebo, esketamine shows cardiocirculatory stabilizing and neuroprotective effects which can be seen in anesthesia induction, cardiac surgery, and analgesia and sedation in brain injury. Evidence of esketamine's antinociceptive efficacy is inconsistent, although a recent meta-analysis reports improved pain relief after surgery in a study with short observation time. To better define esketamine's place, direct head-to-head comparison with the racemate at equi-analgesic/anesthetic dose is warranted.

Apoptotic mechanism of development inhibition in zebrafish induced by esketamine

Esketamine, a widely used intravenous general anesthetic, is also employed for obstetric and pediatric anesthesia, and depression treatment. However, concerns regarding esketamine abuse have emerged. Moreover, the potential in vivo toxicity of esketamine on growth and development remains unclear. To address these concerns, we investigated the effects of esketamine exposure on developmental parameters, cell apoptosis, and gene expression in zebrafish. Esketamine exposure concentration-dependently decreased the heart rate and body length of zebrafish embryos/larvae while increasing the hatching rate and spontaneous movement frequency. Developmental retardation of zebrafish larvae, including shallow pigmentation, small eyes, and delayed yolk sac absorption, was also observed following esketamine treatment. Esketamine exposure altered the expression of apoptosis-related genes in zebrafish heads, primarily downregulating bax, caspase9, caspase3, caspase6, and caspase7. Intriguingly, BTSA1, a Bax agonist, reversed the anti-apoptotic and decelerated body growth effects of esketamine in zebrafish. Collectively, our findings suggest that esketamine may hinder embryonic development by inhibiting embryonic apoptosis via the Bax/Caspase9/Caspase3 pathway. To the best of our knowledge, this is the first study to report the lethal toxicity of esketamine in zebrafish. We have elucidated the developmental toxic effects of esketamine on zebrafish larvae and its potential apoptotic mechanisms. Further studies are warranted to evaluate the safety of esketamine in animals and humans.

Ketamine Clinical Use on the Pediatric Critically Ill Infant: A Global Bibliometric and Critical Review of Literature

The developing central nervous system is vulnerable to several stimuli, especially psychotropic drugs. Sedation procedures during the developmental period are frequent in pediatric intensive care units (PICUs), in which the use of the sedative agent is still a challenge for the PICU team. Ketamine has been indicated for sedation in critically ill children with hemodynamic and ventilatory instabilities, but the possible neurobehavioral consequences related to this use are still uncertain. Here, we performed a bibliometric analysis with conventional metrics and a critical review of clinical findings to reveal a gap in the literature that deserves further investigation. We revealed that only 56 articles corresponded to the inclusion criteria of the study. The United States of America emerges as the main country within the scope of this review. In addition, professional clinical societies play a key role in the publications of scientific clinical findings through the specialist journals, which encourages the sharing of research work. The co-occurrence of keywords evidenced that the terms "sedation", "ketamine", and "pediatric" were the most frequent. Case series and review articles were the most prevalent study design. In the critical evaluation, the scarce studies highlight the need of use and post-use monitoring, which reinforces the importance of additional robust clinical studies to characterize the possible adverse effects resulting from ketamine anesthetic protocol in critically ill children.

Median effective dose of esketamine for intranasal premedication in children with congenital heart disease

BACKGROUND

Esketamine is commonly used as a premedication for its sedation effect. However, the proper dosage for intranasal use in children with congenital heart disease (CHD) has not been determined. This study aimed to estimate the median effective dose (ED₅₀) of esketamine for intranasal premedication in children with CHD.

METHODS

Thirty-four children with CHD who needed premedication in March 2021 were enrolled. Intranasal esketamine was initiated at a dose of 1 mg/kg. Based on the outcome of sedation in the previous patient, the dose for the subsequent patient was either increased or reduced by 0.1 mg/kg, which was adjusted between each child. Successful sedation was defined as a Ramsay Sedation Scale score ≥ 3 and Parental Separation Anxiety Scale score ≤ 2. The required ED₅₀ of esketamine was calculated using the modified sequential method. Non-invasive blood pressure, heart rate, saturation of peripheral oxygen, sedation onset time, and adverse reactions were recorded at 5 min intervals after drug administration.

RESULTS

The 34 children enrolled had a mean age of 22.5 ± 16.4 (4-54) months and a mean weight of 11.2 ± 3.6 (5.5-20.5) kg; American Society of Anesthesiologists classification I-III. The ED₅₀ of intranasal S(+)-ketamine (esketamine) required for preoperative sedation in pediatric patients with CHD was 0.7 (95% confidence interval: 0.54-0.86) mg/kg, and the mean sedation onset time was 16.39 ± 7.24 min. No serious adverse events, such as respiratory distress, nausea, and vomiting were observed.

CONCLUSIONS

The ED₅₀ of intranasal esketamine was 0.7 mg/kg, which was safe and effective for preoperative sedation in pediatric patients with CHD.

TRIAL REGISTRATION

The trial was registered in the Chinese Clinical Trial Registry Network (ChiCTR2100044551) on 24/03/2021.

Prospective observational study on the use of continuous intravenous ketamine and propofol infusion for prolonged sedation in critical care

INTRODUCTION

Analgesia and sedation are a priority in paediatric intensive care. The combination of ketamine and propofol is a possible option in patients requiring prolonged or difficult sedation and to reduce the use of benzodiazepines and opiates. The aim of this study was to assess the efficacy and safety of combination ketamine and propofol in continuous infusion for prolonged analgesia/sedation in the paediatric intensive care setting.

PATIENTS AND METHODS

Prospective, observational single-group cohort study in patients aged 1 month to 16 years admitted to the paediatric intensive care unit in 2016-2018 that received ketamine and propofol in continuous infusion for analgesia and sedation. We collected data on demographic and clinical characteristics, analgesia and sedation scores (MAPS, COMFORT-B and SOPHIA), haemodynamic parameters and adverse events.

RESULTS

The study included 32 patients. The maximum dose of ketamine was 1.5 mg/kg/h (interquartile range [IQR], 1-2 mg/kg/h) and the infusion duration was 5 days (IQR, 3-5 days). The maximum dose of propofol was 3.2 mg/kg/h (IQR, 2.5-3.6 mg/kg/h) and the infusion duration, 5 days (IQR, 3-5 days). Thirty (93.7%) patients had previously received midazolam and 29 (90.6%) fentanyl. Analgesia scores did not change after initiation of the ketamine and propofol infusion. There was a statistically significant increase in the COMFORT-B score, but the score remained in the adequate sedation range (12-17). There were small but statistically significant decreases in the mean arterial pressure (from 64 mmHg to 60 mmHg; P = .006) and the diastolic blood pressure (from 50.5 to 48 mmHg; P = .023) 1 h after the initiation of the ketamine and propofol infusion, but this difference was not observed 12 h later and did not require administration of vasoactive drugs. No other major adverse events were detected during the infusion.

CONCLUSIONS

The combination of ketamine and propofol in continuous infusion is a safe treatment in critically ill children that makes it possible to achieve an appropriate level of analgesia and sedation without relevant haemodynamic repercussions.

Ketamine Prolonged Infusions in the Pediatric Intensive Care Unit: a Tertiary-Care Single-Center Analysis

OBJECTIVE

Ketamine is commonly used as an anesthetic and analgesic agent for procedural sedation, but there is little evidence on its current use as a prolonged continuous infusion in the PICU. We sought to analyze the use of ketamine as a prolonged infusion in critically ill children, its indications, dosages, efficacy, and safety.

METHODS

We retrospectively reviewed the clinical charts of patients receiving ketamine for ≥24 hours in the period 2017-2018 in our tertiary care center. Data on concomitant treatments pre and 24 hours post ketamine introduction and adverse events were also collected.

RESULTS

Of the 60 patients included, 78% received ketamine as an adjuvant of analgosedation, 18% as an adjuvant of bronchospasm therapy, and 4% as an antiepileptic treatment. The median infusion duration was 103 hours (interquartile range [IQR], 58-159; range, 24-287), with median dosages between 15 (IQR, 10-20; range, 5-47) and 30 (IQR, 20-50; range, 10-100) mcg/kg/min. At 24 hours of ketamine infusion, dosages/kg/hr of opioids significantly decreased (p < 0.001), and 81% of patients had no increases in dosages of concomitant analgosedation. For 27% of patients with bronchospasm, the salbutamol infusions were lowered at 24 hours after ketamine introduction. Electroencephalograms of epileptic patients (n = 2) showed resolution of status epilepticus after ketamine administration. Adverse events most likely related to ketamine were hypertension (n = 1), hypersalivation (n = 1), and delirium (n = 1).

CONCLUSIONS

Ketamine can be considered a worthy strategy for the analgosedation of difficult-to-sedate patients. Its use for prolonged sedation allows the sparing of opioids. Its efficacy in patients with bronchospasm or status epilepticus still needs to be investigated.

Ketamine Pharmacokinetics

BACKGROUND

Several models describing the pharmacokinetics of ketamine are published with differences in model structure and complexity. A systematic review of the literature was performed, as well as a meta-analysis of pharmacokinetic data and construction of a pharmacokinetic model from raw data sets to qualitatively and quantitatively evaluate existing ketamine pharmacokinetic models and construct a general ketamine pharmacokinetic model.

METHODS

Extracted pharmacokinetic parameters from the literature (volume of distribution and clearance) were standardized to allow comparison among studies. A meta-analysis was performed on studies that performed a mixed-effect analysis to calculate weighted mean parameter values and a meta-regression analysis to determine the influence of covariates on parameter values. A pharmacokinetic population model derived from a subset of raw data sets was constructed and compared with the meta-analytical analysis.

RESULTS

The meta-analysis was performed on 18 studies (11 conducted in healthy adults, 3 in adult patients, and 5 in pediatric patients). Weighted mean volume of distribution was 252 l/70 kg (95% CI, 200 to 304 l/70 kg). Weighted mean clearance was 79 l/h (at 70 kg; 95% CI, 69 to 90 l/h at 70 kg). No effect of covariates was observed; simulations showed that models based on venous sampling showed substantially higher context-sensitive half-times than those based on arterial sampling. The pharmacokinetic model created from 14 raw data sets consisted of one central arterial compartment with two peripheral compartments linked to two venous delay compartments. Simulations showed that the output of the raw data pharmacokinetic analysis and the meta-analysis were comparable.

CONCLUSIONS

A meta-analytical analysis of ketamine pharmacokinetics was successfully completed despite large heterogeneity in study characteristics. Differences in output of the meta-analytical approach and a combined analysis of 14 raw data sets were small, indicative that the meta-analytical approach gives a clinically applicable approximation of ketamine population parameter estimates and may be used when no raw data sets are available.

EDITOR’S PERSPECTIVE

Extended Duration Ketamine Infusions in Critically Ill Children: A Case Report and Review of the Literature

Ketamine is an N -methyl-D-aspartate receptor antagonist that has been used as an adjunct analgesic and sedative in critically ill children. Previous reports noted that ketamine has been used for a variable duration of 12 to 408 hours for this indication. We report on the use of ketamine infusions for >720 hours as a second-line sedative in addition to an opioid and dexmedetomidine infusion in a 2-month old and 17-month old. The purpose of this case report and review of the literature is to highlight the prolonged ketamine exposure of these two patients and to provide awareness to clinicians on the potential of withdrawal with extended ketamine administration. These children were started on initials doses of 5 and 15 µg/kg/min and titrated to peak doses of 20 and 25 µg/kg/min, respectively. They were continued for a total of 987 and 792 hours, respectively. No adverse events were noted during the ketamine infusions. One patient developed possible withdrawal symptoms 17 hours after ketamine discontinuation despite tapering of the infusion. These symptoms resolved with administration of as needed intravenous opioids and benzodiazepines, and the agitation normalized within 24 hours after ketamine discontinuation. Clinicians should consider tapering ketamine infusions in children receiving >72 hours of a continuous infusion by 5 µg/kg/min every 8 to 12 hours. Patients should be monitored for potential withdrawal symptoms including anxiety, allodynia, hyperalgesia, sweating, and drowsiness.