Propofol 6% as sedative in children under 2 years of age following major craniofacial surgery

The role of systematic reviews in pharmacovigilance planning and Clinical Trials Authorisation application: example from the SLEEPS trial

BACKGROUND

Adequate sedation is crucial to the management of children requiring assisted ventilation on Paediatric Intensive Care Units (PICU). The evidence-base of randomised controlled trials (RCTs) in this area is small and a trial was planned to compare midazolam and clonidine, two sedatives widely used within PICUs neither of which being licensed for that use. The application to obtain a Clinical Trials Authorisation from the Medicines and Healthcare products Regulatory Agency (MHRA) required a dossier summarising the safety profiles of each drug and the pharmacovigilance plan for the trial needed to be determined by this information. A systematic review was undertaken to identify reports relating to the safety of each drug.

METHODOLOGY/PRINCIPAL FINDINGS

The Summary of Product Characteristics (SmPC) were obtained for each sedative. The MHRA were requested to provide reports relating to the use of each drug as a sedative in children under the age of 16. Medline was searched to identify RCTs, controlled clinical trials, observational studies, case reports and series. 288 abstracts were identified for midazolam and 16 for clonidine with full texts obtained for 80 and 6 articles respectively. Thirty-three studies provided data for midazolam and two for clonidine. The majority of data has come from observational studies and case reports. The MHRA provided details of 10 and 3 reports of suspected adverse drug reactions.

CONCLUSIONS/SIGNIFICANCE

No adverse reactions were identified in addition to those specified within the SmPC for the licensed use of the drugs. Based on this information and the wide spread use of both sedatives in routine practice the pharmacovigilance plan was restricted to adverse reactions. The Clinical Trials Authorisation was granted based on the data presented in the SmPC and the pharmacovigilance plan within the clinical trial protocol restricting collection and reporting to adverse reactions.

Scaling of pharmacokinetics across paediatric populations: the lack of interpolative power of allometric models

AIM

The objective of this investigation was to assess the performance of an allometric model as the basis for interpolating drug exposure in the context of pharmacokinetic bridging across paediatric subpopulations.

METHODS

Midazolam was selected as a paradigm compound. Two nonlinear mixed effects models were developed to describe midazolam pharmacokinetics in infants, toddlers and adults (model 1) and in children and adolescents (model 2). Subsequently, systemic drug exposure, expressed in terms of the area under the concentration vs. time curve (AUC), in children and adolescents was interpolated based on pharmacokinetic parameter distributions obtained from the model describing infants, toddlers and adults (model 1). Results were compared with the values obtained from modelling of the data in the corresponding population (model 2).

RESULTS

The two pharmacokinetic models accurately described midazolam exposure in the population on which they were built. However, the model based on data from infants, toddlers and adults failed to predict the exposure observed in children and adolescents: the mean difference between the predicted and estimated AUC(0-180) was of -17.8%, with a range of -6.8 to -38.4%.The discrepancy between estimated and interpolated exposure increased proportionally with body weight.

CONCLUSIONS

The current results indicate that irrespective of whether extrapolation or interpolation methods are to be applied during paediatric drug development, model predictions beyond the range of the data used for parameter estimation may be biased. For accurate inter- or extrapolation to different populations, the assumption of identical parameter-covariate correlations across age groups may not be taken for granted.

Use of propofol in pediatric intensive care units: a national survey in Germany

OBJECTIVE

Propofol is not licensed for sedation in pediatric intensive care medicine mainly due to the risk of propofol infusion syndrome. Nevertheless, it is applied by many pediatric intensive care units. The aim of this national survey was to asses the current use of propofol in pediatric intensive care units in Germany.

DESIGN

We performed a nationwide survey. The questionnaire assessed the intensive care unit type, patient numbers, dosing, duration, age and time limits, indications, side effects, and institutional protocols for propofol usage.

SETTING

Pediatric intensive care units in Germany.

SUBJECTS

Questionnaire about routine use of propofol sent to 214 pediatric departments.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One hundred ninety-four questionnaires (90.7%) were returned, ten had to be censored. The final analysis comprised 184 questionnaires (134 pediatric/neonatal intensive care units, 28 pediatric intensive care units, 22 neonatal intensive care units). Seventy-nine percent of intensive care units (n = 145 of 184) used propofol in children under the age of 16 yrs. Of these, 98% were for bolus application (n = 142 of 145), 78% for infusion ≥3 hrs (n = 113 of 145), and 33% for infusion >3 hrs (n = 48 of 145). A lower age limit was applied by 52% (n = 75 of 145) and a dose limit by 51% (n = 74 of 145). The median dose limit was 4 mg/kg/hr; 48% (n = 70 of 145) used 3 mg/kg/hr or less. A time limit was applied by 98% (n = 46 of 47), 70% (n = 33 of 47) used it for ≤24 hrs, and 30% (n = 15 of 47) for >24 hrs. MAIN INDICATIONS FOR PROPOFOL APPLICATION WERE: difficult sedation (44%), postoperative ventilation (43%), and difficult extubation (30%). Seven cases of propofol infusion syndrome were reported by seven centers.

CONCLUSIONS

This study shows that propofol is used off-license by many pediatric intensive care units in Ge. The majority of users has adopted tightly controlled regimens for propofol sedation, and limits the dose to ≤3-4 mg/kg/hr and the maximum application time to 24-48 hrs.

Does postoperative 'M' technique massage with or without mandarin oil reduce infants' distress after major craniofacial surgery?

AIM

This article is a report of a randomized controlled trial of the effects of 'M' technique massage with or without mandarin oil compared to standard postoperative care on infants' levels of pain and distress, heart rate and mean arterial pressure after major craniofacial surgery.

BACKGROUND

There is a growing interest in non-pharmacological interventions such as aromatherapy massage in hospitalized children to relieve pain and distress but well performed studies are lacking.

METHODS

This randomized controlled trial allocated 60 children aged 3-36 months after craniofacial surgery from January 2008 to August 2009 to one of three conditions; 'M' technique massage with carrier oil, 'M' technique massage with mandarin oil or standard postoperative care. Primary outcome measures were changes in COMFORT behaviour scores, Numeric Rating Scale pain and Numeric Rating Scale distress scores assessed from videotape by an observer blinded for the condition.

RESULTS

In all three groups, the mean postintervention COMFORT behaviour scores were higher than the baseline scores, but differences were not statistically significant. Heart rate and mean arterial pressure showed a statistically significant change across the three assessment periods in all three groups. These changes were not related with the intervention.

CONCLUSIONS

Results do not support a benefit of 'M' technique massage with or without mandarin oil in these young postoperative patients. Several reasons may account for this: massage given too soon after general anaesthesia, young patients' fear of strangers touching them, patients not used to massage.

Assessing circadian rhythms in propofol PK and PD during prolonged infusion in ICU patients

This study evaluates possible circadian rhythms during prolonged propofol infusion in patients in the intensive care unit. Eleven patients were sedated with a constant propofol infusion. The blood samples for the propofol assay were collected every hour during the second day, the third day, and after the termination of the propofol infusion. Values of electroencephalographic bispectral index (BIS), arterial blood pressure, heart rate, blood oxygen saturation and body temperature were recorded every hour at the blood collection time points. A two-compartment model was used to describe propofol pharmacokinetics. Typical values of the central and peripheral volume of distribution and inter-compartmental clearance were V_C = 27.7 l, V_T = 801 l, and CL_D = 2.73 l/min. The systolic blood pressure (SBP) was found to influence the propofol metabolic clearance according to Cl (l/min) = 2.65·(1 − 0.00714·(SBP − 135)). There was no significant circadian rhythm detected with respect to propofol pharmacokinetics. The BIS score was assessed as a direct effect model with EC₅₀ equal 1.98 mg/l. There was no significant circadian rhythm detected within the BIS scores. We concluded that the light–dark cycle did not influence propofol pharmacokinetics and pharmacodynamics in intensive care units patients. The lack of night–day differences was also noted for systolic blood pressure, diastolic blood pressure and blood oxygenation. Circadian rhythms were detected for heart rate and body temperature, however they were severely disturbed from the pattern of healthy patients.

Efficacy of sedation regimens to facilitate mechanical ventilation in the pediatric intensive care unit: a systematic review

OBJECTIVE

Children admitted to pediatric intensive care units (PICUs) often receive sedatives to facilitate mechanical ventilation. However, despite their widespread use, data supporting appropriate dosing, safety, and optimal regimens for sedation during mechanical ventilation are lacking. Therefore, we conducted a systematic review of published data regarding efficacy of sedation to facilitate mechanical ventilation in PICU patients. Our primary objective was to identify and evaluate the quality of evidence supporting sedatives used in PICUs for this purpose.

DATA SOURCES

We searched MEDLINE, EMBASE, and The Cochrane Registry of Clinical Trials from 1966 to June 2008 to identify published articles evaluating sedation regimens to facilitate mechanical ventilation in PICU patients.

STUDY SELECTION

We included only those studies of intubated PICU or pediatric cardiac intensive care unit patients receiving pharmacologic agents to facilitate mechanical ventilation that reported quality of sedation as an outcome.

DATA EXTRACTION

We analyzed studies separately for study type and by agents being studied. Studies were appraised using criteria of particular importance for reviews evaluating sedatives.

DATA SYNTHESIS

Our search strategy yielded 39 studies, including 3 randomized trials, 15 cohort studies, and 21 cases series or reports. The 39 studies evaluated a total of 39 different sedation regimens, with 21 different scoring systems, in a total of 901 PICU/cardiac intensive care unit patients ranging in age from 3 days to 19 years old. Most of the studies were small (<30 patients), and only four studies compared one or more agents to another. Few studies thoroughly evaluated drug safety, and only one study met all quality criteria.

CONCLUSIONS

Despite the widespread use of sedatives to facilitate mechanical ventilation in the PICU, we found that high-quality evidence to guide clinical practice is still limited. Pediatric randomized, controlled trials with reproducible methods and assessment of drug safety are needed.

Maturational pharmacokinetics of single intravenous bolus of propofol

BACKGROUND

Our aim was to document propofol pharmacokinetics in preterm and term neonates following a single intravenous bolus and compare these estimates with pharmacokinetics findings in toddlers and young children.

METHODS

Newly collected observations following intravenous bolus administration of propofol in preterm and term neonates (n = 9) were compared with earlier reported pharmacokinetic estimates in toddlers and young children. Data are reported by median and range. Mann-Whitney U-test or correlation was used to analyze differences in pharmacokinetic findings between neonates, toddlers and young children.

RESULTS

Concentration-time profiles obtained were interpreted by two-stage analysis as a three compartment open model in nine neonates with a median weight of 2.51 (range 0.91-3.8) kg and a median postmenstrual age (PMA) of 36 (range 27-43) weeks. Median clearance (CL) was 13.6 (range 3.7-78.2) ml.min(-1).kg(-1) and median apparent volume of distribution at steady state (V(ss)) was 3.7 (1.33-7.96) l.kg(-1). Following allometric scaling and standardization to 70 kg, median CL was 442 (range 97-2184) ml.min(-1).70 kg(-1). Compared with earlier reported observations in toddlers and children, median clearance (kg.min(-1)) was significantly lower in neonates (P < 0.01) and these differences remained significant after allometric scaling (70 kg.min(-1)) while V(ss) (l.kg(-1)) was significantly lower in neonates (P < 0.01).

CONCLUSIONS

Propofol disposition is significantly different in neonates compared with toddlers and young children, reflecting both ontogeny and differences in body composition. Based on the reduced clearance of propofol, a longer recovery time is more likely to occur in neonates.

Objective and continuous measurement of peripheral motor indicators of pain in hospitalized infants: a feasibility study

Measurement of pain in pre-verbal infants is complex. Until now, pain behavior has mainly been assessed intermittently using observational tools. Therefore, we determined the feasibility of long-term, objective and continuous measurement of peripheral motor parameters through body-fixed sensors to discriminate between pain and no pain in hospitalized pre-verbal infants. Two pain modes were studied: for procedural pain 10 measurements were performed before, during and after routine heel lances in 9 infants (age range infants: 5-175 days), and for post-operative pain 14 infants (age range 45-400 days) were measured for prolonged periods (mean 7h) using the validated COMFORT-behavior scale as reference method. Several peripheral motor parameters were studied: three body part activity parameters derived from acceleration sensors attached to one arm and both legs, and two muscle activity parameters derived from electromyographic (EMG) sensors attached to wrist flexor and extensor muscles. Results showed that the accelerometry-based parameters legs activity and overall extremity activity (i.e. mean of arm and legs) were significantly higher during heel lance than before or after lance (p0.001), whereas arm activity accelerometry data and wrist muscle activity EMG data showed no significant change. For the post-operative pain measurements, relationships were found between accelerometry-based overall extremity activity and COMFORT-behavior (r=0.76, p<0.001), and between EMG-based wrist flexor activity and COMFORT-behavior (r=0.55, p<0.001, for a subgroup of 7 infants). We conclude that long-term, objective and continuous measurement of peripheral motor parameters is feasible, has high potential, and is promising to assess pain in pre-verbal hospitalized infants.

Organ toxicity and mortality in propofol-sedated rabbits under prolonged mechanical ventilation

BACKGROUND

Prolonged administration of propofol at large doses has been implicated in propofol infusion syndrome in intensive care unit patients. In this study we investigated organ toxicity and mortality of propofol sedation at large doses in prolonged mechanically ventilated rabbits and determined the role of propofol's lipid vehicle.

METHODS

Eighteen healthy male rabbits were endotracheally intubated and sedated with propofol 2% (Group P), sevoflurane (Group S) or sevoflurane while receiving Intralipid 10% (Group SI). Sedation lasted 48 h or until death (Group P) or the maximum surviving period of Group P (Groups S and SI). The initial propofol infusion rate (20 mg x kg(-1) x h(-1)) or sevoflurane concentration (1.5%) was adjusted, if needed, to maintain a standard level of sedation. Blood biochemical analysis was performed in serial blood samples and histologic examination in the heart, lungs, liver, gallbladder, kidneys, urinary bladder, and quadriceps femoris muscle at autopsy.

RESULTS

The mortality rate was 100% (surviving period, 26-38 h) for Group P, whereas 0% for Groups S and SI. The initial propofol infusion rate had to be increased up to 65.7 +/- 4.6 mg x kg(-1) x h(-1) and sevoflurane concentration up to 4%. Serum liver function indices, lipids and creatine kinase were significantly increased (P < 0.05) in Groups P and SI and lactate was increased only in Group P, whereas amylase was increased in all groups. In Group P, histologic examination revealed myocarditis, pulmonary edema with interstitial pneumonia, hepatitis, steatosis, and focal liver necrosis, cholangitis, gallbladder necrosis, acute tubular necrosis of the kidneys, focal loss of the urinary bladder epithelium, and rhabdomyolysis of skeletal muscles; in Group S, low-grade bronchitis and incipient inflammation of the liver and the kidneys; and in Group SI, low-grade bronchitis, liver steatosis and hepatitis, and incipient inflammation of the gallbladder, kidneys, and urinary bladder.

CONCLUSIONS

Continuous infusion of 2% propofol at large doses for the sedation of rabbits undergoing prolonged mechanical ventilation induced fatal multiorgan dysfunction syndrome similar to the propofol infusion syndrome seen in humans. Our novel findings including lung, liver, gallbladder, and urinary bladder injury were also noted. The role of propofol's lipid vehicle in the manifestation of the syndrome was minor. Sevoflurane proved to be a safe alternative medication for prolonged sedation.

Effect of propofol on seizure-like phenomena and electroencephalographic activity in children with epilepsy vs children with learning difficulties

There is an ongoing debate as to whether propofol exhibits pro- or anticonvulsant effects, and whether it should be used in patients with epilepsy. We prospectively assessed the occurrence of seizure-like phenomena and the effects of intravenous propofol on the electroencephalogram (EEG) in 25 children with epilepsy (mean (SD) age: 101 (49) months) and 25 children with learning difficulties (mean (SD) age: 52 (40) months) undergoing elective sedation for MRI studies of the brain. No child demonstrated seizure-like phenomena of epileptic origin during and after propofol sedation. Immediately after stopping propofol, characteristic EEG changes in the epilepsy group consisted of increased beta wave activity (23/25 children), and suppression of pre-existing theta rhythms (11/16 children). In addition, 16 of 18 children with epilepsy and documented EEG seizure activity demonstrated suppression of spike-wave patterns after propofol sedation. In all 25 children with learning difficulties an increase in beta wave activity was seen. Suppression of theta rhythms occurred in 11 of 12 children at the end of the MRI study. In no child of either group was a primary occurrence or an increase in spike-wave patterns seen following propofol administration. The occurrence of beta wave activity (children with learning difficulties and epilepsy group) and suppression of spike-wave patterns (epilepsy group) were transient, and disappeared after 4 h. This study demonstrates characteristic, time-dependent EEG patterns induced by propofol in children with epilepsy and learning difficulties. Our data support the concept of propofol being a sedative-hypnotic agent with anticonvulsant properties as shown by depression of spike-wave patterns in children with epilepsy and by the absence of seizure-like phenomena of epileptic origin.