Dexmedetomidine in Children

Dexmedetomidine decreases inhibitory but not excitatory neurotransmission to cardiac vagal neurons in the nucleus ambiguus

Dexmedetomidine, an α2 adrenergic agonist, is a useful sedative but can also cause significant bradycardia. This decrease in heart rate may be due to decreased central sympathetic output as well as increased parasympathetic output from brainstem cardiac vagal neurons. In this study, using whole cell voltage clamp methodology, the actions of dexmedetomidine on excitatory glutamatergic and inhibitory GABAergic and glycinergic neurotransmission to parasympathetic cardiac vagal neurons in the rat nucleus ambiguus was determined. The results indicate that dexmedetomidine decreases both GABAergic and glycinergic inhibitory input to cardiac vagal neurons, with no significant effect on excitatory input. These results provide a mechanism for dexmedetomidine induced bradycardia and has implications for the management of this potentially harmful side effect.

Preemptive dexmedetomidine to prevent propofol injection pain in children

BACKGROUND

The incidence of propofol injection pain is high in children, but no methods have been found to suppress it completely. This study intends to evaluate the efficacy of dexmedetomidine-midazolam in preventing propofol injection pain in children.

METHODS

One-hundred ASA I patients, aged 3-12 years, weighing 15-53 kg, undergoing elective surgery were randomized into two groups of 50 each, using computer-generated random numbers. Normal saline 0.15 ml/kg in Group C or dexmedetomidine 0.6 μg/kg in Group D was infused IV over 10 min. Then midazolam 0.06 mg/kg was administered immediately; 2 min after aforementioned treatments in each group, all patients received propofol 2 mg/kg (propofol was mixed with lidocaine 1 mg/ml in Group C) at an average rate of 0.2 ml per 1 s. Another anesthesiologist, blind to the pretreatment, recorded the occurrence of injection pain using a four-graded pain scale: 1 = no pain (no reaction to injection), 2 = slight pain (minor verbal/facial response or motor reaction to injection), 3 = moderate pain (clear verbal/facial response or motor reaction to injection) and 4 = severe pain (the patient both complained of pain and withdrew the arm).

RESULTS

Forty (80 %) patients in Group C (control) had injection pain; however, none of patients in Group D had any injection pain. The total incidence of profol-induced pain in Group C was significantly higher (P < 0.01). There were no instances of bradycardia or low blood pressure with either treatment in this study.

CONCLUSIONS

Pretreatment with dexmedetomidine 0.6 μg/kg, then midazolam 0.06 mg/kg could suppress propofol injection pain in children.

Dexmedetomidine for rigid bronchoscopy in an infant with tracheal web after ventricular septal defect patch repair

We report herein successful rigid bronchoscopy with preserved spontaneous breathing of a 54-day-old infant with tracheal web associated with previous ventricular septal defect (VSD) repair. We considered the use of dexmedetomidine in conjunction with intermittent ketamine from the following three clinical aspects. First, this infant was suffering from respiratory distress with chest retraction, the cause of which was not revealed by a computerized scan of the neck and chest. Second, the patient was scheduled for rigid bronchoscopy, which is accompanied by brief but strong stimulation. Third, this infant underwent congenital VSD heart repair approximately 1 month earlier.

Anaesthetic management in a child with an atypical triad for reconstructive scoliosis surgery

Scoliosis may be of varied aetiology and may be associated with severe congenital anomalies. It often poses a challenge in its anaesthetic management. We present anaesthetic management of a child who underwent scoliosis reconstruction with a rare triad of cerebral palsy, glucose-6-phosphate dehydrogenase deficiency and severe mitral regurgitation. Anaesthetic management in these patients should focus primarily on associated co-morbidities and congenital anomalies affecting the course of the perioperative management and thereafter comprehensive pre-operative strategies must be executed to enhance the safety profile during the surgery.

Effect of dexmedetomidine on sevoflurane requirements and emergence agitation in children undergoing ambulatory surgery

PURPOSE

Dexmedetomidine, a potent selective α2-adrenergic agonist, produces sedation and analgesia. This study was conducted to assess the effect of dexmedetomidine infusion on sevoflurane requirements, recovery profiles, and emergence agitation in children undergoing ambulatory surgery.

MATERIALS AND METHODS

Forty children undergoing ambulatory hernioplasty or orchiopexy were randomized into two groups. The dexmedetomidine group (Group D, n=20) received dexmedetomidine 1 μg/kg, followed by 0.1 μg/kg/h until the end of surgery, whereas the saline group (Group S, n=20) received volume-matched normal saline. Sevoflurane was used for induction and maintenance of anesthesia and caudal block was performed in all children. End-tidal sevoflurane concentration (ET-sevo), the incidence of emergence agitation, pain scores, and sedation scores were recorded. Hemodynamic changes and other adverse effects were assessed in the perioperative period.

RESULTS

ET-sevo of Group D was significantly reduced in 23.8-67% compared to Group S during surgery. The incidence of emergence agitation was lower in Group D than in Group S (5% vs. 55%, p=0.001). Postoperative pain was comparable, and discharge time was not different between the groups. Mean arterial pressure and heart rate were significantly lower in Group D during surgery.

CONCLUSION

Intraoperative infusion of dexmedetomidine reduced sevoflurane requirements and decreased emergence agitation without delaying discharge in children undergoing ambulatory surgery. However, caution should be taken in regard to bradycardia and hypotension.

Anaesthesiological and intensive care management in craniovertebral junction surgery

The main factors of modern perioperative care of the craniovertebral junction surgery include a comprehensive approach to the patients, including a thorough cardiorespiratory, neurophysiological, and metabolic assessment, intraoperative monitoring of spinal cord function, safe airway management, and judicious use of fluids and blood transfusions. Admission in PICU shortly after the CVJ surgery is mandatory to ensure haemodynamic and respiratory stability and to recognize postoperative complications. Anticipating complications in order to achieve an early treatment and adverse event prophylaxis can contribute to reduced morbidity and mortality and increased patients' safety. Multidisciplinary management of perioperative patient care and careful pain control is mandatory in order to improve the outcomes.

Case series: Dexmedetomidine and ketamine for anesthesia in patients with uncorrected congenital cyanotic heart disease presenting for non-cardiac surgery

The number of patients with uncorrected congenital cyanotic heart disease is less but at times some may present for non-cardiac surgery with a high anesthetic risk. Some of these may even be adults with compromised cardiopulmonary physiology posing greater challenges to the anesthesiologist. The authors have used a combination of dexmedetomidine and ketamine for anesthesia for non cardiac surgery in five patients with cyanotic heart disease and right to left shunt (3-Eisenmenger's syndrome, 2-Tetralogy of Fallot). The sympathoinhibitory effects of dexmedetomidine were balanced with the cardiostimulatory effects of ketamine, thereby maintaining good cardiovascular stability. The analgesia was good and there was no postoperative agitation. This drug combination was effective and safe for patients with cyanotic heart disease for non cardiac surgeries.

Hemodynamic responses to dexmedetomidine in critically injured intubated pediatric burned patients: a preliminary study

Because of ineffectiveness and tolerance to benzodiazepines and opioids developing with time, drugs acting via other receptor systems (eg, α-2 agonists) have been advocated in burn patients to improve sedation and analgesia. This study in severely burned pediatric subjects examined the hemodynamic consequences of dexmedetomidine (Dex) administration. Eight intubated patients with ≥20 to 79% TBSA burns were studied between 7 and 35 days after injury. After baseline measurements of mean arterial blood pressure and heart rhythm were taken, each patient received a 1.0 µg/kg bolus of Dex followed by an ascending dose infusion protocol (0.7-2.5 µg/kg/hr), with each dose administered for 15 minutes. There was significant hypotension (27±7.5%, average drop in mean arterial pressure [MAP] ± SD), and a decrease in heart rate (HR; 19% ± 7, average drop in HR ± SD). The average HR decreased from 146 beats per minute to 120. No bradycardia (HR < 60) or heart blocks were observed. In three patients, the MAP decreased to <50mm Hg with the bolus dose of Dex. Of the remaining five patients, three patients completed the study receiving the highest infusion dose of Dex (2.5 µg/kg/hr), whereas in 2 patients the infusion part of the study was begun, but the study was stopped due to persistent hypotension (MAP < 50mm Hg). These observations indicate that a bolus dose of Dex (1.0 µg/kg for 10 minutes) and high infusion rates may require fluid resuscitation or vasopressor support to maintain normotension in critically injured pediatric burn patients.

Propofol-remifentanil or sevoflurane for children undergoing magnetic resonance imaging? A randomised study

BACKGROUND

Magnetic resonance imaging (MRI) of children is generally performed under sedation or with general anaesthesia (GA), but the ideal regimen has not been found. The aim of this study was to see if propofol-remifentanil would be a suitable alternative for the maintenance of anaesthesia in this category of patients.

PATIENTS AND METHODS

Children aged 1-10 years, American Society of Anesthesiologists physical status 1-2 were included. After induction with thiopental or sevoflurane, the children were randomised to maintenance of anaesthesia with an infusion of propofol and remifentanil (group PR) (56 μg/kg/min of propofol and 0.06 μg/kg/min of remifentanil) or with sevoflurane 1.3 MAC (group S). A binasal catheter was placed in group PR and a laryngeal mask airway in group S. The children breathed spontaneously. The Paediatric Anaesthesia Emergence Delirium (PAED) score (primary end point), the number of movements during MRI, and the length of stay in the recovery room (secondary endpoints) were recorded.

RESULTS

Sixty children were included in each group. A lower level of emergence delirium (measured as a lower PAED score) was found in group PR compared with group S, and the children in group PR were discharged earlier from the recovery room than the children in group S. However, 15 children in group PR vs. 0 in group S moved during the scan (P < 0.001).

CONCLUSION

The PR infusion ensured a satisfactory stay in the recovery room, but additional boluses were necessary during the MRI. Sevoflurane was reliable during the MRI, but emergence delirium was a concern.

Dexmedetomidine for patients undergoing diagnostic cardiac procedures: a noninferiority study

When anesthetizing children with congenital heart disease for diagnostic cardiac catheterization, anesthesiologists and cardiologists seek to use anesthetic regimens that yield minimal hemodynamic changes and allow for spontaneous ventilations. Recently, dexmedetomidine has been used as an anesthesia adjunct because of its sedative and analgesic properties and minimal ventilatory depressive effects. We tested the hypothesis that the combination of sevoflurane and dexmedetomidine is non-inferior to sevoflurane alone as it refers to hemodynamic measurements during diagnostic cardiac catheterization in children with a transplanted heart, one ventricle (Fontan procedure), or normal cardiac physiology. Patients were anesthetized with inhalation of sevoflurane in nitrous oxide/oxygen and, after baseline hemodynamic measurements, successive boluses of dexmedetomidine followed by continuous infusion were administered. In this study, non-inferiority was shown when differences at steady-state (dexmedetomidine + sevoflurane) compared to baseline (sevoflurane alone) and its associated 95% confidence interval fell completely within the range of plus or minus 20%. Forty-one (26 normal physiology, 9 cardiac transplantation, and 6 Fontan) patients were enrolled. Non-inferiority of sevoflurane + dexmedetomidine compared with sevoflurane alone was shown for heart rate, but not for arterial blood pressure in patients with normal and cardiac transplant physiology. In patients with normal cardiac physiology, non-inferiority was demonstrated for bispectral index. Therefore, while the lack of depressive respiratory effects and non-inferiority for heart rate are desirable, the lack of non-inferiority of dexmedetomidine + sevoflurane combination for arterial blood pressure do not justify the routine use of this combination compared with sevoflurane alone for children with congenital heart disease undergoing cardiac catheterization.

Long QT syndrome unmasked by dexmedetomidine: a case report

Dexmedetomidine is a selective alpha-2 adrenergic agonist that is used frequently for short-term sedation in children. It has been noted to cause hypertension, hypotension, bradycardia, and sinus pauses; however, QTc prolongation has not been reported with dexmedetomidine administration. We describe a case of marked QT prolongation with use of dexmedetomidine in a pediatric critical care setting. Clinicians should be vigilant about potential QT prolongation in patients on dexmedetomidine, particularly in those receiving multiple other medications.

Sedation and analgesia in mechanically ventilated preterm neonates: continue standard of care or experiment?

Attention to comfort and pain control are essential components of neonatal intensive care. Preterm neonates are uniquely susceptible to pain and agitation, and these exposures have a negative impact on brain development. In preterm neonates, chronic pain and agitation are common adverse effects of mechanical ventilation, and opiates or benzodiazepines are the pharmacologic agents most often used for treatment. Questions remain regarding the efficacy, safety, and neurodevelopmental impact of these therapies. Both preclinical and clinical data suggest troubling adverse drug reactions and the potential for adverse longterm neurodevelopmental impact. The negative impacts of standard pharmacologic agents suggest that alternative agents should be investigated. Dexmedetomidine is a promising alternative therapy that requires further interprofessional and multidisciplinary research in this population.

Development of a stable isotope dilution UPLC-MS/MS method for quantification of dexmedetomidine in a small amount of human plasma

Dexmedetomidine (Dex) is a selective central α2-agonist with anesthetic properties and has been used in clinical practice for sedation in the intensive care unit (ICU) after operations. In this study, an analytical assay for the determination of Dex in a small amount of plasma was developed for the application to pediatric ICU trials. The quantification of Dex was constructed using the original stable isotope Dex-d3 for electrospray ionization-tandem mass spectrometry (ESI-MS/MS) in the selected reaction monitoring mode. A rapid ultra-performance liquid chromatography technique was adopted using ESI-MS/MS with a runtime of 3 min. Efficacious concentration levels (50 pg/mL to 5 ng/mL) could be evaluated using a very small amount of plasma (10 μL) from patients. The lower limit of the quantification was 5 pg/mL in the plasma (100 µL). For sample preparation, a solid-phase extraction was used along with the OASIS-HLB cartridge type. Recovery values ranged from 98.8 to 100.3% for the intra- [relative standard deviation (RSD), 0.9-1.3%] and inter- (RSD, 0.9-1.5%) day assays. A stable test had recovery values that ranged from 97.8 to 99.7% with an RSD of 1.0-1.9% for the process/wet extract, bench-top, freeze-thaw and long-term tests. This method was used to measure the Dex levels in plasma from pediatric ICU patients. In the clinical ICU trial, the small amount of blood (approximate plasma volume, 200 μL) remaining from blood gas analysis was reused and targeted for the clinical analysis of Dex in plasma.

Efficacy and safety of intraoperative dexmedetomidine for acute postoperative pain in children: a meta-analysis of randomized controlled trials

BACKGROUND

Aim of the current meta-analysis was to assess the effects of intraoperative dexmedetomidine on postoperative pain, analgesic consumption, and adverse events in comparison with placebo or opioids in children undergoing surgery.

METHODS

This meta-analysis was performed according to the recommendations of the PRISMA statement and the Cochrane collaboration. For dichotomous and continuous outcomes of efficacy and adverse events, the Revman(®) (The Nordic Cochrane Centre, Copenhagen, Denmark) statistical software was used to calculate relative risk (RR), mean difference (MD), and 95% confidence intervals (CI).

RESULTS

We included 11 randomized controlled trials - 434 children received dexmedetomidine, 440 received control. In comparison with placebo, children receiving dexmedetomidine showed a reduced RR for postoperative opioids (0.4; 95% CI: 0.26-0.62; P < 0.00001) and postoperative pain (0.51; 95% CI: 0.32-0.81; P = 0.004). Similar results were obtained for the comparison with intraoperative opioids: reduced RR for postoperative pain (0.49; 95% CI: 0.25-0.94; P = 0.03) and the need for postoperative opioids (0.77; 95% CI: 0.60-1.09; P = 0.05).

CONCLUSIONS

This meta-analysis revealed a lower risk for postoperative pain and the need for postoperative opioids following intraoperative dexmedetomidine in comparison with placebo or opioids in children undergoing surgery; however, the influence of dexmedetomidine on postoperative opioid consumption is less clear. Although there were only a limited number of adverse events, further studies focusing on procedure specific dexmedetomidine dosing and adverse events are urgently needed.

Inhibition of insulin secretion from rat pancreatic islets by dexmedetomidine and medetomidine, two sedatives frequently used in clinical settings

The aim of this study was to determine whether dexmedetomidine (DEX) and medetomidine (MED), α2-adrenergic agonists clinically used as sedatives, influence insulin secretion from rat pancreatic islets. Islets were isolated from adult male Wistar rats after collagenase digestion. Static incubation was used to determine effects of DEX or MED on insulin secretion and ionic-channel currents of β-cells. Results indicate that both drugs dose-dependently inhibit insulin secretion, DEX more potently than MED. The inhibitory effects were attenuated by addition of yohimbine or by pretreatment of rats with pertussis toxin (PTX). 10 nM DEX decreased the current amplitude of voltage-dependent Ca2+ channels, but this did not occur when the N-type Ca2+ channel blocker ω-conotoxin was added. In the presence of tetraethylammonium, a classical voltage-gated K+ channel (Kv channel) blocker, the magnitude of inhibition of insulin secretion by MED was reduced. However, when tolbutamide, a specific blocker of the ATP-sensitive K+ channel (KATP channel), was present, the magnitude of MED inhibition of insulin secretion was not influenced, suggesting that Kv-channel activity alteration, but not that of KATP channels, is involved in MED-associated insulin secretory inhibition. The Kv-channel currents were increased during 1 nM MED exposure at membrane potentials ranging from -30 mV to -10 mV, where action potentials were generated in response to glucose stimulation. These results indicate that DEX and MED inhibit insulin secretion through an α2-adrenoceptor and PTX-sensitive GTP-binding protein pathway that eventually involves Kv channel activation and Ca2+ channel inhibition.

Clonidine abolishes the adverse effects on apoptosis and behaviour after neonatal ketamine exposure in mice

BACKGROUND

An increasing amount of both experimental and epidemiological data indicates that neonatal anaesthesia causes disruption of normal brain development in rodents and primates, as manifested by acute increased apoptosis and long-lasting altered behaviour and learning. It is necessary to seek strategies that avoid the possible adverse effects after anaesthesia. Our purpose is to show that increased apoptosis and behavioural alterations after ketamine exposure during this period may be prevented by clonidine, a compound already used by paediatric anaesthetists for sedation.

METHODS

To investigate the protective properties of clonidine pre-treatment, five groups of 10-day-old mice were injected with either ketamine 50 mg/kg, clonidine 40 μg/kg, ketamine 50 mg/kg 30 min after 10 μg/kg clonidine, ketamine 50 mg/kg 30 min after 40 μg/kg clonidine or saline (control). Apoptosis was measured 24 h after treatment using Flouro-Jade staining. Spontaneous activity in a novel environment was tested at an age of 55 days.

RESULTS

Pre-treatment with 40 μg/kg clonidine, but not 10 μg/kg clonidine, 30 min before ketamine exposure abolished ketamine-induced apoptosis and the behavioural changes observed in the young adult mice. The mice exposed to clonidine alone showed no differences from the saline-treated (control) mice.

CONCLUSION

The administration of clonidine eliminated the adverse effects of ketamine in this mouse model, suggesting a possible strategy for protection. Alone, clonidine did not cause any adverse effects in these tests.