The effect of melatonin on sedation of children undergoing magnetic resonance imaging

Background. Melatonin may induce a natural sleepiness and improvepredictability of sedation drugs. We have investigated its clinicalvalue in children sedated for magnetic resonance imaging. Methods. In a stratified randomized double-blind study, 98 childrenreceived either melatonin or placebo 10 min before they weresedated with a standard oral regimen. Children >5 and <15kg received chloral hydrate and those     

Rescue sedation with dexmedetomidine for diagnostic imaging: a preliminary report

BACKGROUND: Sedation is frequently required during noninvasive radiological imaging in children. Although commonly used agents such as chloral hydrate and midazolam are generally effective, failures may occur. The authors report their experience with dexmedetomidine for rescue sedation during magnetic resonance imaging. METHODS: A retrospective chart review was undertaken. RESULTS: The cohort included five patients ranging in age from 11 months to 16 years. Following the failure of other agents (chloral hydrate and/or midazolam), dexmedetomidine was administered as a loading dose of 0.3-1.0 microg x kg(-1) x min(-1) over 5-10 min followed by an infusion of 0.5-1.0 microg x kg(-1) x h(-1). The dexmedetomidine loading dose required to induce sedation was 0.78 +/- 0.42 microg x kg(-1) (range 0.3-1.2). The maintenance infusion rate was 0.57 +/- 0.06 microg x kg(-1) x h(-1) (range 0.48-0.69). The imaging procedures were completed without difficulty. No patient required additional bolus administrations or changes in the infusion rate. The duration of the dexmedetomidine infusion ranged from 30 to 50 min. The mean decrease in heart rate was 13.6 +/- 5.1 b x min(-1) (14.3 +/- 5.0% from baseline; P = 0.02), the mean decrease in systolic blood pressure was 26.4 +/- 15.2 mmHg (24.6 +/- 12.4% decrease from baseline; P = 0.004), and the mean decrease in respiratory rate was 1.4 +/- 1.5 min(-1) (7.5 +/- 7.9% decrease from baseline; P = NS). P(E)CO2 exceeded 6.5 kPa (50 mmHg) in one patient [maximum 6.6 kPa (51 mmHg)] with a maximum value of 6.0 +/- 0.4 kPa (46 +/- 3 mmHg). Oxygen saturation decreased from 98 +/- 1 to 95 +/- 1%; P = 0.001. No patient developed hypoxemia (oxygen saturation less than 90%). Mean time to recovery to baseline status was 112.5 +/- 50.6 min and time to discharge was 173.8 +/- 83.8 min. CONCLUSIONS: Our preliminary experience suggests that dexmedetomidine may be an effective agent for procedural sedation during radiological imaging. Its potential application in this setting is discussed and other reports regarding its use in pediatric patients are reviewed.     

Propofol vs pentobarbital for sedation of children undergoing magnetic resonance imaging: results from the Pediatric Sedation Research Consortium

Background: Pentobarbital and propofol are commonly used to sedate children undergoing magnetic resonance imaging (MRI). The Pediatric Sedation Research Consortium (PSRC) was created in 2003 to improve pediatric sedation process and outcomes. Objective: To use PSRC records to compare the effectiveness, efficiency and adverse events of propofol vs pentobarbital for sedation of children undergoing MRI. Methods: Pediatric Sedation Research Consortium records of children aged 6 months to 6 years who were primarily sedated with either i.v. pentobarbital or propofol were included. Participating PSRC investigators obtained institutional review board approval before data collection. Results: Of 11 846 sedations for MRI, 7079 met inclusion criteria (propofol: n = 5072; pentobarbital: n = 2007). Demographic details were similar between the two groups. Ideal sedation was produced in 96.45% of the pentobarbital group and in 96.8% of the propofol group (P = 0.478), but pentobarbital was more likely to result in poor sedation canceling the procedure (OR 5.88; CI 2.24, 15.40). Propofol resulted in physiologic changes more frequently than did pentobarbital (OR 5.69; CI 1.35, 23.97). Pentobarbital was associated with prolonged recovery (OR 16.82; CI 4.98, 56.8), unplanned admission (OR 5.60; CI 1.02, 30.82), vomiting (OR 36.76; CI 4.84, 279.2) and allergic complication (OR 9.15; CI 1.02, 82.34). The incidence of airway complications was not significantly different between the two. The median recovery time for patients receiving propofol was 30 min, whereas for pentobarbital it was 75 min (P < 0.001). Conclusion: Among institutions contributing data to the PSRC, it is found that propofol provides more efficient and effective sedation than pentobarbital for children undergoing MRI. Although apnea occurred with a greater frequency in patients who received propofol, the rate of apnea and airway complications for propofol was not statistically different from that seen in patients who received pentobarbital.     

Nurse-led dexmedetomidine sedation for magnetic resonance imaging in children: a 6-year quality improvement project

We aimed to safely introduce dexmedetomidine into a nurse-led sedation service for magnetic resonance imaging in children. Secondary aims were to increase the number of children eligible for sedation and to increase the actual number of children having sedation performed by our nurse sedation team. We analysed 1768 consecutive intravenous and 219 intranasal dexmedetomidine sedation episodes in infants, children and adolescents having magnetic resonance imaging scans between March 2016 and March 2022. The overall sedation success rate was 98.4%, with a 98.9% success rate for intravenous dexmedetomidine and a 95.0% success rate for intranasal dexmedetomidine. The incidence of scan interruption during intravenous and intranasal dexmedetomidine sedation was 8.8% and 21.9%, respectively. We conclude that paediatric sedation with dexmedetomidine for magnetic resonance scanning is safe and successful.     

Oral sedation with midazolam and diphenhydramine compared with midazolam alone in children undergoing magnetic resonance imaging

BACKGROUND: The purpose of this study was to compare the safety and efficacy of oral midazolam and midazolam-diphenhydramine combination to sedate children undergoing magnetic resonance imaging (MRI). METHODS: We performed a prospective randomized double-blind study in 96 children who were randomly allocated into two groups. Group D received oral diphenhydramine (1.25 mg x kg(-1)) with midazolam (0.5 mg x kg(-1)), and Group P received oral placebo with midazolam (0.5 mg x kg(-1)) alone. Sedation scores, onset and duration of sleep were evaluated. Adverse effects, including hypoxemia, failed sedation, and the return of baseline activity, were documented. RESULTS: Diphenhydramine facilitated an earlier onset of midazolam sedation (P < 0.01), and higher sedation scores (P < 0.01). In children who received midazolam alone, 20 (41%) were inadequately sedated, compared with 9 (18%) children who received midazolam and diphenhydramine combination (P < 0.01). Time to complete recovery was not significantly different between the two groups. CONCLUSIONS: Our study indicates that the combination of oral diphenhydramine with oral midazolam resulted in safe and effective sedation for children undergoing MRI. The use of this combination might be more advantageous compared with midazolam alone, resulting in less sedation failure during MRI.     

Fasting times and gastric contents volume in children undergoing deep propofol sedation--an assessment using magnetic resonance imaging

Aim: To investigate the effect of fasting times for clear fluids and solids/non‐clear fluids on gastric content volume using magnetic resonance imaging (MRI). Methods: Pediatric patients undergoing diagnostic MRI under deep propofol sedation, with the stomach located within the area of diagnostic study, were included in this clinical observational study. According to standard institutional guidelines, children were allowed to eat/drink until 4 h and to drink clear fluids until 2 h before scheduled induction time of anesthesia. Gastric content volume per kg body weight (GCV_w) was determined using MRI and compared with actual fasting times prior to induction. Results: Overall 68 patients aged from 0.3 to 19.6 (2.8) years were investigated. Fasting time for clear fluids ranged from 1.1 to 15.5 (5.5) h, for non‐clear fluids/solids from 4.0 to 20.2 (6.7) h. GCV_w ranged from 0.2 to 6.3 (0.75) ml·kg^?1 and showed no significant negative correlation to fasting times for clear fluids (r = ?0.07, P = 0.60) and non‐clear fluids/solids (r = ?0.08, P = 0.51). Conclusions: Based on this preliminary data, GCV_w showed considerable variation but did not correlate with fasting times in children and adolescent patients. Recommended fasting times were often exceeded.     

Structured sedation programme for magnetic resonance imaging examination in children

One thousand, eight hundred and fifty-seven patients underwent magnetic resonance imaging following the establishment of a structured sedation programme. Forty-eight of these patients came from the intensive care unit with a secure airway and were therefore excluded from any further analysis. Oral sedation was to be given to children aged 5 years and below. For children >/= 6 years old, oral sedation could be given only if their level of co-operation was judged to be inadequate by the referring physician. Oral sedation consisted of chloral hydrate 90 mg x kg-1 (maximum 2.0 g) orally with or without rectal paraldehyde 0.3 ml x kg-1. All magnetic resonance imaging requests for children who failed oral sedation as well as those referred for general anaesthesia from the outset were reviewed by a consultant anaesthetist who then allocated patients to undergo the procedure with either general anaesthesia or intravenous sedation. Scans requiring intravenous sedation or general anaesthesia were performed in the presence of a consultant anaesthetist. Intravenous sedation consisted of either a propofol 0.5 mg x kg-1 bolus followed by an infusion (maximum 3 mg x kg-1 x h-1) or midazolam 0.2-0.5 mg x kg-1 boluses. General anaesthesia was given using spontaneous ventilation with a mixture of 66% nitrous oxide in oxygen and isoflurane following either inhalation (sevoflurane) or intravenous (propofol) induction. One thousand and thirty-nine (57.4%) of the scans were done without sedation whereas 93 scans were performed during the consultant anaesthetist supervised sessions. Oral sedation failed in 50 out of 727 patients (6.9%). Eighty-seven per cent of children aged 5 years and below needed sedation compared with 4.5% of those aged over 10 years. Two patients who had only received chloral hydrate developed significant respiratory depression. This structured sedation programme has provided a safe, effective and efficient use of limited resources.     

Incidence and predictors of hypertension during high‐dose dexmedetomidine sedation for pediatric MRI

This study reviewed the hypertensive response of a large population of children to high‐dose dexmedetomidine sedation with the aim of determining the incidence and predictors of hypertension. Background: When dexmedetomidine is used to provide sedation for children, fluctuations in blood pressure have been described in case reports. We report the incidence and predictors of hypertension in a large series of children who received dexmedetomidine. Methods/Materials: At our institution, a computerized database holds patient demographics, sedation outcomes, adverse events, and hemodynamic data for all children who receive dexmedetomidine sedation for radiological imaging studies. After Institutional Review Board approval, this database was reviewed. Results: Three thousand five hundred twenty‐two (3522) children received dexmedetomidine sedation between May 1, 2007 and December 31, 2008 for magnetic resonance imaging studies. Median age was 3.6 years (interquartile range: 1.8–5.9). A total of 172 patients (4.9%) developed hypertension, with a higher incidence in the younger age group (0–3 years) when compared to the older age groups (3–18 years) (P < 0.05). Multivariable logistic regression modeling confirmed that younger age (Wald test = 43.5 of 5 degrees of freedom, P < 0.001) and more than one bolus (Wald test = 22.7, P < 0.001) were highly significant predictors of the occurrence of hypertension. Conclusion: When high‐dose dexmedetomidine is used for pediatric sedation for MR imaging, the incidence of hypertension is low. Hypertension is most likely to occur in children <1 year of age during the continuous infusion, after they have received more than one bolus of dexmedetomidine.     

Monitored anesthesia care with a combination of ketamine and dexmedetomidine during magnetic resonance imaging in three children with trisomy 21 and obstructive sleep apnea

We present a series of three children with trisomy 21 and obstructive sleep apnea who required sedation during magnetic resonance imaging of the upper airway. In an effort to provide effective sedation with limited effects on cardiovascular and ventilatory function, sedation was provided by a combination of ketamine and dexmedetomidine. Sedation was initiated with a bolus dose of ketamine (1 mg x kg(-1)) and dexmedetomidine (1 microg x kg(-1)) and maintained by a continuous infusion of dexmedetomidine (1 microg x kg(-1) x h(-1)). One patient required a repeat of the bolus doses of ketamine and dexmedetomidine and an increase of the dexmedetomidine infusion to 2 microg x kg(-1) x h(-1). Effective sedation was provided for all three patients. We noted no clinically significant hemodynamic or respiratory effects. No central apnea was noted although there was a brief episode of upper airway obstruction in one patient which responded to repositioning of the airway. All three patients developed some degree of hypercarbia with maximum P(E)(CO2) values of 6.4, 6.9, and 6.8 kPa (49, 53, and 52 mmHg), respectively. To date, this is the first report regarding the use of this combination in pediatric patients. Given the preliminary success noted in our three patients, prospective trials evaluating the efficacy of a dexmedetomidine-ketamine combination appears warranted.     

Atelectasis in children undergoing either propofol infusion or positive pressure ventilation anesthesia for magnetic resonance imaging

BACKGROUND: Atelectasis because of anesthesia is a recognized problem but may be affected by the anesthetic technique. We compared magnetic resonance images of atelectasis in children undergoing two types of anesthesia. METHODS: Children requiring anesthesia for magnetic resonance imaging (MRI) had additional lung imaging sequences at the beginning and the end of anesthesia. Children had either i.v. propofol infusion (PI) without an artificial airway (n = 26) or positive pressure ventilation (PPV) via a tracheal tube (n = 20); the technique was chosen for clinical reasons. The extent of atelectasis was scored by two independent radiologists. RESULTS: The median ages (range) for PI and PPV groups were 45 months (1-77 months) and 18 months (2-74 months), respectively. The proportion of children with atelectasis was different in the first lung scan (42% vs 80%), but in the second scan atelectasis was seen frequently in both groups (82% vs 94%) with a greater extent in the PPV group. The atelectasis score was higher in young children, but all children had normal oxygen requirements and saturations. CONCLUSIONS: Many factors may influence the development of atelectasis but this study found less extensive atelectasis with PI than PPV. PI allows for sufficient motionlessness, required for high diagnostic image quality in pediatric MRI.     

右美托咪定复合丙泊酚在小儿磁共振检查镇静中的应用观察

目的:观察经鼻给予右美托咪定（dexmedetomidine, Dex）复合小剂量丙泊酚静脉推注应用于小儿两部位MRI检查的安全性和有效性。方法:60例ASA分级Ⅰ、Ⅱ级择期行两个部位（中途需搬动患儿1次,时间>45 min）MRI检查的儿童,按照随机数字表法分为两组（每组30例）：右美托咪定2 μg/kg组（D2组）...     

Anaesthesia with midazolam and S-(+)-ketamine in spontaneously breathing paediatric patients during magnetic resonance imaging

We evaluated safety and efficacy of a sedation technique based on rectal and intravenous S-(+)-ketamine and midazolam to achieve immobilization during Magnetic Resonance Imaging (MRI). Thirty-four paediatric patients were randomly assigned to undergo either the sedation protocol (study group) or general anaesthesia (control group). Imaging was successfully completed in all children. Children in the study group received a rectal bolus (0.5 mg x kg(-1) midazolam and 5 mg x kg(-1) S-(+)-ketamine) and required additional i.v. supplementation (20+/-10 microg x kg(-1) x min(-1) S-(+)-ketamine and 4+/-2 microg x kg(-1) x min(-1) midazolam), spontaneous ventilation was maintained. Transient desaturation occurred once during sedation and four times in the control group (P=0.34). PECO2 was 5.3+/-0.5 kPa (40+/-4 mm Hg) in the study group and 4.1+/-0.6 kPa (31+/-5 mm Hg) in the control group (P<0.001). Induction and discharge times were shorter in the study group (P<0.001), recovery times did not differ significantly between the groups. Our study confirms that a combination of rectal and supplemental intravenous S-(+)-ketamine plus midazolam is a safe and useful alternative to general anaesthesia for MRI in selected paediatric patients.     

Propofol anesthesia in spontaneously breathing children undergoing magnetic resonance imaging: comparison of two propofol emulsions

BACKGROUND: This study evaluated a propofol-based anesthesia regimen with spontaneous breathing in pediatric patients scheduled for magnetic resonance imaging (MRI). METHODS: In this prospective, randomized, double-blind study propofol formulated with long-chain triglycerides (LCT) and mixed medium-chain/long-chain triglycerides (MCT/LCT) were used. Ninety patients aged 2.4 months to 7.3 years were premedicated with intravenous midazolam. Lidocaine was injected prior to propofol to reduce injection pain. Anesthesia was induced and maintained by propofol. Glycopyrronium bromide was administered for saliva reduction. Hemodynamics, blood oxygen saturation and endtidal capnography were continuously monitored. All patients received additional oxygen. The aggregated propofol dose for induction and maintenance of anesthesia was analyzed for therapeutic equivalence. Incidence of injection pain, laboratory safety values, vital signs, and the adverse event profile were analyzed to compare tolerability and safety. RESULTS: Propofol anesthesia was safe and successful in all children. Both propofol formulations were equivalent regarding dose requirements (mean induction and maintenance doses for anesthesia 2.0-4.0 mg.kg(-1) and 6.0-8.8 mg.kg(-1).h(-1) respectively; aggregated doses 8-13.26 mg.kg(-1)). There were no differences in drug safety such as hemodynamics, spontaneous breathing, injection pain, and laboratory values. Duration of induction and of recovery from anesthesia were short and all examinations were completed with minimal interruption. CONCLUSIONS: Propofol-based short-term anesthesia was well suited for anesthesia during MRI procedures in the studied pediatric patients. There were no clinically relevant differences between the two propofol formulations.     

A comparison of the sedative, hemodynamic, and respiratory effects of dexmedetomidine and propofol in children undergoing magnetic resonance imaging

We compared the sedative, hemodynamic, and respiratory effects of dexmedetomidine and propofol in children undergoing magnetic resonance imaging procedures. Sixty children were randomly distributed into two groups: The dexmedetomidine (D) group received 1 microg/kg initial dose followed by continuous infusion of 0.5 microg.kg(-1).h(-1) and a propofol group (P) received 3 mg/kg initial dose followed by a continuous infusion of 100 microg.kg(-1).min(-1). Inadequate sedation was defined as difficulty in completing the procedure because of the child's movement during magnetic resonance imaging. Mean arterial pressure (MAP), heart rate, peripheral oxygen saturation, and respiratory rate (RR) were recorded during the study. The onset of sedation, recovery, and discharge time were significantly shorter in group P than in group D. MAP, heart rate, and RR decreased during sedation from the baseline values in both groups. MAP and RR were significantly lower in group P than in group D during sedation. Desaturation was observed in four children of group P. Dexmedetomidine and propofol provided adequate sedation in most of the children. We conclude that although propofol provided faster anesthetic induction and recovery times, it caused hypotension and desaturation. Thus, dexmedetomidine could be an alternative reliable sedative drug to propofol in selected patients.     

Pharmacokinetics of intravenous dexmedetomidine in children under 11 yr of age

Background: Information has been very limited on the pharmacokinetics ofthe selective ₂-adrenoceptor agonist dexmedetomidine in children,particularly in children <2 yr of age. Methods: Eight children aged between 28 days and 23 months and eightchildren aged between 2 and 11 yr undergoing either electivebronchoscopy or nuclear magnetic resonance imaging were includedin the study. Dexmedetomidine 1 µg kg^–1 was infusedi.v. over 5 min. Blood samples for the measurement of plasmaconcentrations of dexmedetomidine were collected for 5 h afterstarting the infusion. Pharmacokinetic calculations were basedon non-compartmental methods. Results: In the two groups of paediatric patients, the median (range)values for total plasma clearance of dexmedetomidine were 17.4(14.1–27.6) and 17.3 (9.3–22.5) ml kg^–1 min^–1,for volume of distribution at steady state 3.8 (1.9–4.6)and 2.2 (1.3–2.8) litre kg^–1 (P<0.05), and forelimination half-life 139 (90–198) and 96 (69–140)min (P<0.05), respectively. The volume of distribution atsteady state was negatively associated with subject age (r=–0.69,P<0.05). Conclusions: To reach a certain plasma concentration, children younger than2 yr of age evidently need larger initial doses of dexmedetomidinethan the older children, as young children have a larger volumeof distribution of the drug than older children and adults.Since the total plasma clearance of dexmedetomidine is independentof age, similar rates of infusion can be used in younger andolder children to maintain a steady-state concentration of dexmedetomidinein plasma.     

Combined propofol and remifentanil intravenous anesthesia for pediatric patients undergoing magnetic resonance imaging

BACKGROUND: A prospective observational case series of children receiving light general anesthesia for magnetic resonance imaging (MRI) was performed. Our purpose was to examine the merit of anesthesia and recovery/discharge times of combined remifentanil and propofol total intravenous anesthesia (TIVA) in spontaneously breathing children. METHODS: After IRB approval and informed consent, 56 patients receiving Remi/Propofol TIVA (Remifentanil 10 microg.ml(-1) Propofol 10 mg.ml(-1)) were observed. Blood pressure, respiratory rate, endtidal CO(2) (P(E)CO(2)), oxygen saturation and temperature were recorded at the start and finish of anesthesia. In addition, induction and recovery times were noted. Recovery time was from scan completion until discharge from the initial recovery area. Discharge time was from scan completion to discharge home. RESULTS: Fifty-six patients received Remi/Propofol TIVA. The mean Remi/Propofol recovery and discharge times were 8.9 and 28.2 min, respectively. There was a statistically significant decrease in respiratory rate and increase in CO(2) from the start to the end of the procedure. During the scan, seven patients moved. One patient experienced postprocedure nausea and or vomiting. CONCLUSIONS: The combination of remifentanil and propofol for TIVA may be an effective method of light general anesthesia in pediatric patients undergoing MRI.     

Testing of adult and paediatric ventilators for use in a magnetic resonance imaging unit

We have assessed the performance of a series of ventilators (modified versions of the ventiPAC, paraPAC and babyPAC ventilators; SIMS pneuPAC Ltd, Luton, UK) in a magnetic resonance imaging (MRI) scanning environment, with MR safety and compatibility issues being addressed. Following initial modifications to remove ferromagnetic components and replace them with MR-safe materials, all three ventilators performed well in a series of tests in static magnetic fields up to 2 T. Ventilator performance was unaffected by static fields, switching gradients or radio frequency fields within the MR suite. Furthermore, the devices produced no degradation of image quality when used during MR scanning. We discuss management strategies for the care of critically ill ventilated patients during MR procedures.     

Sequential effects of propofol on functional brain activation induced by auditory language processing: an event-related functional magnetic resonance imaging study

Background. We have investigated the effect of propofol on languageprocessing using event-related functional magnetic resonanceimaging (MRI). Methods. Twelve healthy male volunteers underwent MRI scanningat a magnetic field strength of 3 Tesla while performing anauditory language processing task. Functional images were acquiredfrom the perisylvian cortical regions that are associated withauditory and language processing. The experiment consisted ofthree blocks: awake state (block 1), induction of anaesthesiawith 3 mg kg^–1 propofol (block 2), and maintenance ofanaesthesia with 3 mg kg^–1 h^–1 propofol (block 3).During each block normal sentences and pseudo-word sentenceswere presented in random order. The subjects were instructedto press a button to indicate whether a sentence was made upof pseudo-words or not. All subjects stopped responding duringblock two. The data collected before and after the subjectsstopped responding during this block were analyzed separately.In addition, propofol plasma concentrations were measured andthe effect-site concentrations of propofol were calculated. Results. During wakefulness, language processing induced brainactivation in a widely distributed temporofrontal network. Immediatelyafter unresponsiveness, activation disappeared in frontal areasbut persisted in both temporal lobes (block 2 second half, propofoleffect-site concentration: 1.51 µg ml^–1). No activationdifferences related to the task were observed during block 3(propofol effect-site concentration: 4.35 µg ml^–1). Conclusion. Our findings suggest sequential effects of propofolon auditory language processing networks. Brain activation firstlydeclines in the frontal lobe before it disappears in the temporallobe. Br J Anaesth 2004; 92: 641–50