Pharmacokinetic concepts for dexmedetomidine target-controlled infusion pumps in children

Absorption pharmacokinetics and feasibility of intranasal dexmedetomidine in patients under general anaesthesia

BACKGROUND

The use of intranasal dexmedetomidine is hampered by a limited understanding of its absorption pharmacokinetics.

METHODS

We examined the pharmacokinetics and feasibility of intranasal dexmedetomidine administered in the supine position to adult patients undergoing general anaesthesia. Twenty-eight patients between 35 and 80 years of age, ASA 1-3 and weight between 50 and 100 kg, who underwent elective unilateral total hip or knee arthroplasty under general anaesthesia were recruited. All patients received 100 μg of intranasal dexmedetomidine after anaesthesia induction. Six venous blood samples (at 0, 5, 15, 45, 60, 240 min timepoints from dexmedetomidine administration) were collected from each patient and dexmedetomidine plasma concentrations were measured. Concentration-time profiles after nasal administration were pooled with earlier data from a population analysis of intravenous dexmedetomidine (n = 202) in order to estimate absorption parameters using nonlinear mixed effects. Peak concentration (CMAX) and time (TMAX) were estimated using simulation (n = 1000) with parameter estimates and their associated variability.

RESULTS

There were 28 adult patients with a mean (SD) age of 66 (8) years and weight of 83 (10) kg. The mean weight-adjusted dose of dexmedetomidine was 1.22 (0.15) μg kg-1. CMAX 0.273 μg L-1 was achieved at 98 min after intranasal administration (TMAX). The relative bioavailability of dexmedetomidine was 80% (95% CI 75-91%). The absorption half-time (TABS = 120 min; 95% CI 90-147 min) was slower than that in previous pharmacokinetic studies on adult patients. Perioperative haemodynamics of all patients remained stable.

CONCLUSIONS

Administration of intranasal dexmedetomidine in the supine position during general anaesthesia is feasible with good bioavailability. This administration method has slower absorption when compared to awake patients in upright position, with consequent concentrations attained after TMAX for several hours.

Low-dose sevoflurane co-administered with propofol-based general anaesthesia obliterates intra-operative neurophysiological monitoring in an infant

The influence of general anaesthetic agents on intra-operative neurophysiological monitoring in neonates and infants has rarely been reported. Propofol-based anaesthesia is recommended to avoid suppression of neurophysiological monitoring. However, the administration of propofol in children undergoing prolonged procedures, especially those younger than six months, should be carefully controlled due to the potential risk of propofol infusion syndrome. Adding a small dose of inhalational anaesthetic can be an option to reduce propofol requirements. Recent guidelines in Japan suggest limiting inhalational anaesthetics to less than 0.5 minimum alveolar concentrations when co-administered with low-dose propofol during intra-operative neuromonitoring. However, there is still insufficient evidence regarding the impact of sevoflurane on neurophysiological monitoring when co-administered with propofol in infants. This report describes a case of a three-month-old infant undergoing spinal lipoma resection in which there was a dramatic suppression of neurophysiological monitoring with the addition of 0.35-0.45% sevoflurane to propofol-based anaesthesia.

Intranasal dexmedetomidine sedation for paediatric MRI by radiology personnel: A retrospective observational study

BACKGROUND

MRI often requires sedation or anaesthesia to ensure good image quality in paediatric patients. Access to paediatric anaesthesia services is, however, a limiting factor for effective paediatric MRI service, and alternative sedation methods are, therefore, warranted.

OBJECTIVE

To investigate the efficacy and safety of an intranasal dexmedetomidine sedation program for paediatric MRI, without immediate presence of anaesthesia personnel.

DESIGN

Single institution retrospective observational study.

SETTING

Tertiary care paediatric hospital.

PATIENTS

Children 0 to 12 years, ASA risk class 1 or 2 with heart rate within age-appropriate limit.

INTERVENTION

Radiology personnel administered an initial dose of intranasal dexmedetomidine of 4 μg kg -1 followed by a second dose of 2 μg kg -1 to the patients if needed. Recordings of image quality, critical events, heart rate, pulse oximetry saturation and noninvasive blood pressure before and after dexmedetomidine administration were made.

MAIN OUTCOME MEASURES

Changes in haemodynamic and respiratory data before vs. after intranasal dexmedetomidine were analysed for changes, and the incidence of critical events was evaluated as well as rate of successful MRI scans.

RESULTS

One thousand and ninety-one MRIs under intranasal dexmedetomidine sedation were included (mean age 34 months, 95% confidence interval (CI), 33 to 36, 599 male individuals). A success rate of 93% (95% CI, 91 to 94%) was found. No major critical events were recorded, total incidence of minor issues was 0.2% (95% CI, 0 to 0.7%). Five children had a heart rate under a preset minimal limit after dexmedetomidine (0.4%; 95% CI, 0.1 to 0.9%). Significant decreases in heart rate and mean arterial pressure, within acceptable limits not requiring intervention, was seen after dexmedetomidine administration.

CONCLUSION

Intranasal dexmedetomidine sedation without immediate presence of anaesthesia personnel appears to be well tolerated and associated with minimal interference on MRI image quality.

TRIAL REGISTRATION

clinicaltrials.org NCT05163704, retrospectively registered.

A comprehensive overview of clinical research on dexmedetomidine in the past 2 decades: A bibliometric analysis

Introduction: Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist with sedative, analgesic, anxiolytic, and opioid-sparing properties. A large number of dexmedetomidine-related publications have sprung out in the last 2 decades. However, no bibliometric analysis for clinical research on dexmedetomidine has been published to analyze hot spots, trends, and frontiers in this field. Methods: The clinical articles and reviews related to dexmedetomidine, published from 2002 to 2021 in the Web of Science Core Collection, were retrieved on 19 May 2022, using relevant search terms. VOSviewer and CiteSpace were used to conduct this bibliometric study. Results: The results showed that a total of 2,299 publications were retrieved from 656 academic journals with 48,549 co-cited references by 2,335 institutions from 65 countries/regions. The United States had the most publications among all the countries (n = 870, 37.8%) and the Harvard University contributed the most among all institutions (n = 57, 2.48%). The most productive academic journal on dexmedetomidine was Pediatric Anesthesia and the first co-cited journal was Anesthesiology. Mika Scheinin is the most productive author and Pratik P Pandharipande is the most co-cited author. Co-cited reference analysis and keyword analysis illustrated hot spots in the dexmedetomidine field including pharmacokinetics and pharmacodynamics, intensive care unit sedation and outcome, pain management and nerve block, and premedication and use in children. The effect of dexmedetomidine sedation on the outcomes of critically ill patients, the analgesic effect of dexmedetomidine, and its organ protective property are the frontiers in future research. Conclusion: This bibliometric analysis provided us with concise information about the development trend and provided an important reference for researchers to guide future research.

Propofol context-sensitive decrement times in children

Plasma drug concentration is the variable linking dose to effect. The decrement time required for plasma concentration of anesthetic agents to decrease by 50% (context-sensitive half-time) correlates with the time taken to regain consciousness. However, the decrement time to consciousness may not be 50%. An effect compartment concentration is associated more closely with return of consciousness than plasma concentration. An alternative decrement time, the time required for propofol to decrease to a predetermined effect compartment concentration associated with movement (eg, 2 µg.ml^-1 ), was used to simulate time for the concentration to decrease from steady state at a typical targeted effect compartment concentration 3.5 µg.ml^-1 in children. These times were short and reflected a decrement time to consciousness (CST_AWAKE ) increase that was small with longer infusion time. CST_AWAKE ranged from 7.5 min in 1-year-old infant given propofol for 15 min to 13.5 min in a 15-year-old adolescent given a 2-hour infusion. Changes in decrement time with age reflect maturation of drug clearance. Neonates had prolonged increment times, 10 min after 15 min infusion and 18 min after 120 min infusion using a target concentration of 3.5 µg.ml^-1 . Decrement times to a targeted arousal concentration are context-sensitive. Use of a higher target concentration of 6 µg.ml^-1 doubled decrement times. Decrement times are associated with variability: delayed recovery beyond these simulated times is likely more attributable to the use of adjuvant drugs or the child's clinical status. An understanding of propofol decrement times can be used to guide recovery after anesthesia.