Haemodynamic responses and population pharmacokinetics of midazolam following administration to ventilated, preterm neonates

Characterization of Pediatric Rectal Absorption, Drug Disposition, and Sedation Level for Midazolam Gel Using Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling

This study aims to explore and characterize the role of pediatric sedation via rectal route. A pediatric physiologically based pharmacokinetic-pharmacodynamic (PBPK/PD) model of midazolam gel was built and validated to support dose selection for pediatric clinical trials. Before developing the rectal PBPK model, an intravenous PBPK model was developed to determine drug disposition, specifically by describing the ontogeny model of the metabolic enzyme. Pediatric rectal absorption was developed based on the rectal PBPK model of adults. The improved Weibull function with permeability, surface area, and fluid volume parameters was used to extrapolate pediatric rectal absorption. A logistic regression model was used to characterize the relationship between the free concentrations of midazolam and the probability of sedation. All models successfully described the PK profiles with absolute average fold error (AAFE) < 2, especially our intravenous PBPK model that extended the predicted age to preterm. The simulation results of the PD model showed that when the free concentrations of midazolam ranged from 3.9 to 18.4 ng/mL, the probability of "Sedation" was greater than that of "Not-sedation" states. Combined with the rectal PBPK model, the recommended sedation doses were in the ranges of 0.44-2.08 mg/kg for children aged 2-3 years, 0.35-1.65 mg/kg for children aged 4-7 years, 0.24-1.27 mg/kg for children aged 8-12 years, and 0.20-1.10 mg/kg for adolescents aged 13-18 years. Overall, this model mechanistically quantified drug disposition and effect of midazolam gel in the pediatric population, accurately predicted the observed clinical data, and simulated the drug exposure for sedation that will inform dose selection for following pediatric clinical trials.

Predicting Volume of Distribution in Neonates: Performance of Physiologically Based Pharmacokinetic Modelling

The volume of distribution at steady state (Vss) in neonates is still often estimated through isometric scaling from adult values, disregarding developmental changes beyond body weight. This study aimed to compare the accuracy of two physiologically based pharmacokinetic (PBPK) Vss prediction methods in neonates (Poulin & Theil with Berezhkovskiy correction (P&T+) and Rodgers & Rowland (R&R)) with isometrical scaling. PBPK models were developed for 24 drugs using in-vitro and in-silico data. Simulations were done in Simcyp (V22) using predefined populations. Clinical data from 86 studies in neonates (including preterms) were used for comparison, and accuracy was assessed using (absolute) average fold errors ((A)AFEs). Isometric scaling resulted in underestimated Vss values in neonates (AFE: 0.61), and both PBPK methods reduced the magnitude of underprediction (AFE: 0.82-0.83). The P&T+ method demonstrated superior overall accuracy compared to isometric scaling (AAFE of 1.68 and 1.77, respectively), while the R&R method exhibited lower overall accuracy (AAFE: 2.03). Drug characteristics (LogP and ionization type) and inclusion of preterm neonates did not significantly impact the magnitude of error associated with isometric scaling or PBPK modeling. These results highlight both the limitations and the applicability of PBPK methods for the prediction of Vss in the absence of clinical data.

The use of neurally-adjusted ventilatory assist (NAVA) for infants with congenital diaphragmatic hernia (CDH)

OBJECTIVES

Newborns with congenital diaphragmatic hernia (CDH) can have complex respiratory problems which are worsened by ventilatory induced lung injury. Neurally adjusted ventilator assist (NAVA) is a potentially promising ventilation mode for this population, as it can result in improved patient-ventilator interactions and provision of adequate gas exchange at lower airway pressures.

CONTENT

A literature review was undertaken to provide an overview of NAVA and examine its role in the management of infants with CDH.

SUMMARY

NAVA in neonates has been used in CDH infants who were stable on ventilatory support or being weaned from mechanical ventilation and was associated with a reduction in the level of respiratory support.

OUTLOOK

There is, however, limited evidence regarding the efficacy of NAVA in infants with CDH, with only short-term benefits being investigated. A prospective, multicentre study with long term follow-up is required to appropriately assess NAVA in this population.

Neurocardiovascular coupling in congenital diaphragmatic hernia patients undergoing different types of surgical treatment

BACKGROUND

The effect of peri-operative management on the neonatal brain is largely unknown. Triggers for perioperative brain injury might be revealed by studying changes in neonatal physiology peri-operatively.

OBJECTIVE

To study neonatal pathophysiology and cerebral blood flow regulation peri-operatively using the neuro-cardiovascular graph.

DESIGN

Observational, prospective cohort study on perioperative neuromonitoring. Neonates were included between July 2018 and April 2020.

SETTING

Multicentre study in two high-volume tertiary university hospitals.

PATIENTS

Neonates with congenital diaphragmatic hernia were eligible if they received surgical treatment within the first 28 days of life. Exclusion criteria were major cardiac or chromosomal anomalies, or syndromes associated with altered cerebral perfusion or major neurodevelopmental impairment. The neonates were stratified into different groups by type of peri-operative management.

INTERVENTION

Each patient was monitored using near-infrared spectroscopy and EEG in addition to the routine peri-operative monitoring. Neurocardiovascular graphs were computed off-line.

MAIN OUTCOME MEASURES

The primary endpoint was the difference in neurocardiovascular graph connectivity in the groups over time.

RESULTS

Thirty-six patients were included. The intraoperative graph connectivity decreased in all patients operated upon in the operation room (OR) with sevoflurane-based anaesthesia ( P  < 0.001) but remained stable in all patients operated upon in the neonatal intensive care unit (NICU) with midazolam-based anaesthesia. Thoracoscopic surgery in the OR was associated with the largest median connectivity reduction (0.33 to 0.12, P  < 0.001) and a loss of baroreflex and neurovascular coupling. During open surgery in the OR, all regulation mechanisms remained intact. Open surgery in the NICU was associated with the highest neurovascular coupling values.

CONCLUSION

Neurocardiovascular graphs provided more insight into the effect of the peri-operative management on the pathophysiology of neonates undergoing surgery. The neonate's clinical condition as well as the surgical and the anaesthesiological approach affected the neonatal physiology and CBF regulation mechanisms at different levels.

TRIAL REGISTRATION

NL6972, URL: https://www.trialre-gister.nl/trial/6972 .

Cerebral Oxygenation and Activity During Surgical Repair of Neonates With Congenital Diaphragmatic Hernia: A Center Comparison Analysis

Background and aim: Neonatal brain monitoring is increasingly used due to reports of brain injury perioperatively. Little is known about the effect of sedatives (midazolam) and anesthetics (sevoflurane) on cerebral oxygenation (rScO₂) and cerebral activity. This study aims to determine these effects in the perioperative period. Methods: This is an observational, prospective study in two tertiary pediatric surgical centers. All neonates with a congenital diaphragmatic hernia received perioperative cerebral oxygenation and activity measurements. Patients were stratified based on intraoperatively administrated medication: the sevoflurane group (continuous sevoflurane, bolus fentanyl, bolus rocuronium) and the midazolam group (continuous midazolam, continuous fentanyl, and continuous vecuronium). Results: Intraoperatively, rScO₂ was higher in the sevoflurane compared to the midazolam group (84%, IQR 77-95 vs. 65%, IQR 59-76, p = < 0.001), fractional tissue oxygen extraction was lower (14%, IQR 5-21 vs. 31%, IQR 29-40, p = < 0.001), the duration of hypoxia was shorter (2%, IQR 0.4-9.6 vs. 38.6%, IQR 4.9-70, p = 0.023), and cerebral activity decreased more: slow delta: 2.16 vs. 4.35 μV ² (p = 0.0049), fast delta: 0.73 vs. 1.37 μV ² (p = < 0.001). In the first 30 min of the surgical procedure, a 3-fold increase in fast delta (10.48-31.22 μV ²) and a 5-fold increase in gamma (1.42-7.58 μV ²) were observed in the midazolam group. Conclusion: Sevoflurane-based anesthesia resulted in increased cerebral oxygenation and decreased cerebral activity, suggesting adequate anesthesia. Midazolam-based anesthesia in neonates with a more severe CDH led to alarmingly low rScO₂ values, below hypoxia threshold, and increased values of EEG power during the first 30 min of surgery. This might indicate conscious experience of pain. Integrating population-pharmacokinetic models and multimodal neuromonitoring are needed for personalized pharmacotherapy in these vulnerable patients. Trial Registration: https://www.trialregister.nl/trial/6972, identifier: NL6972.

First dose in neonates: pharmacokinetic bridging study from juvenile mice to neonates for drugs metabolized by CYP3A

First dose prediction is challenging in neonates. Our objective in this proof-of-concept study was to perform a pharmacokinetic (PK) bridging study from juvenile mice to neonates for drugs metabolized by CYP3A. We selected midazolam and clindamycin as model drugs. We developed juvenile mice population PK models using NONMEM. The PK parameters of these two drugs in juvenile mice were used to bridge PK parameters in neonates using different correction methods. The bridging results were evaluated by the fold-error of 0.5- to 1.5-fold. Simple allometry with and without a correction factor for maximum lifespan potential could be used for a bridging of clearance (CL) and volume of distribution (V_d), respectively, from juvenile mice to neonates. Simulation results demonstrated that for midazolam, 100% of clinical studies for which both the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. For clindamycin, 75% and 100% of clinical studies for which the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. A PK bridging of drugs metabolized by CYP3A is feasible from juvenile mice to neonates. It could be a complement to the ADE and PBPK models to support the first dose in neonates.

Electronic Health Record-Embedded Decision Support Platform for Morphine Precision Dosing in Neonates

Morphine is the opioid most commonly used for neonatal pain management. In intravenous form, it is administered as continuous infusions and intermittent injections, mostly based on empirically established protocols. Inadequate pain control in neonates can cause long-term adverse consequences; however, providing appropriate individualized morphine dosing is particularly challenging due to the interplay of rapid natural physiological changes and multiple life-sustaining procedures in patients who cannot describe their symptoms. At most institutions, morphine dosing in neonates is largely carried out as an iterative process using a wide range of starting doses and then titrating to effect based on clinical response and side effects using pain scores and levels of sedation. Our background data show that neonates exhibit large variability in morphine clearance resulting in a wide range of exposures, which are poorly predicted by dose alone. Here, we describe the development and implementation of an electronic health record-integrated, model-informed decision support platform for the precision dosing of morphine in the management of neonatal pain. The platform supports pharmacokinetic model-informed dosing guidance and has functionality to incorporate real-time drug concentration information. The feedback is inserted directly into prescribers' workflows so that they can make data-informed decisions. The expected outcomes are better clinical efficacy and safety with fewer side effects in the neonatal population.

Arterial spin-labeling magnetic resonance imaging of brain maturation in early childhood: Mathematical model fitting to assess age-dependent change of cerebral blood flow

PURPOSE

To determine the trajectory of age-dependent cerebral blood flow (CBF) change in infants and young children by fitting mathematical models to the imaging data.

METHODS

In this retrospective study, we reviewed the arterial spin-labeling imaging studies of 49 typically developing infants and young children at postmenstrual age (PMA) ranging from 38 to 194 weeks. All patients had normal structural MR imaging. Coregistration and gray matter segmentation were performed to extract whole-brain CBF values. Regional CBF values were obtained using manual region-of-interest placement. Curve estimation regression procedures with the corrected Akaike information criterion (AICc) were performed to determine the mathematical model best fitting the relationship between the CBF (whole-brain and regional measurements) and PMA of the patients.

RESULTS

Whole-brain CBF trajectory was best fitted by a cubic model (AICc = 215.95; R² = 0.566; P < .001). Whole-brain CBF at 1, 6, 12, and 24 months was estimated to be 36, 52, 58, and 55 mL/100 g/min, respectively. Regional CBF trajectory was also best fitted by a cubic model in the frontal (AICc = 233.63; R² = 0.442; P < .001), parietal (AICc = 229.18; R² = 0.614; P < .001), basal ganglion (AICc = 239.39; R² = 0.178; P = .043), temporal (AICc = 236.01; R² = 0.441; P < .001), and occipital (AICc = 236.46; R² = 0.475; P < .001) regions.

CONCLUSIONS

In early childhood, the trajectory of CBF change was nonlinear and best fitted by the cubic model for the whole brain and all brain regions.

Narcotics and sedatives use in the mechanical ventilation in preterm infants: Predictors and outcome

BACKGROUND

Mechanical ventilation (MV) causes discomfort but whether it causes pain remains controversial. Around the world neonatal intensive care units (NICU) often utilize narcotics and/or sedatives during MV of vulnerable infants yet the association with adverse neonatal outcomes has not been adequately addressed.

OBJECTIVE

Test for associations between the use of narcotics/sedatives during MV and mortality/morbidity in preterm infants in a large infant cohort in Canada.

DESIGN/METHODS

Preterm infants born <35 weeks gestational age (GA) requiring MV for >24 hrs were identified retrospectively from the Canadian Neonatal Network database, 2010-12. Infants were categorized according to whether they received narcotics/sedatives for greater than 24 hours concurrently with MV. Infants were excluded if moribund on admission, had major congenital anomalies, diagnoses where narcotic administration is routine and suspected seizures. Multivariable logistic and linear regression analysis tested for association of narcotics/sedatives use during MV with mortality/morbidity (nosocomial infections, BPD, ROP, IVH) and length of MV.

RESULTS

After exclusions the cohort included 2672 infants; 467(17%) exposed only to narcotics 101(4%) only to sedatives and 299(11%) to both. All models were adjusted for GA, gender, small for GA, SNAP-II score >20, multiple births, delivery mode, outborn, PDA status, MV type, use of high flow, muscle relaxant use, indwelling lines, caffeine and surfactant therapy. The composite mortality/morbidity, and MV days were significantly higher for MV infants exposed to narcotics, sedatives or both compared to infants not exposed.

CONCLUSION

Mounting evidence of the adverse short and long-term impacts of narcotics/sedatives during MV supports the need for further work in alternative therapies.

First-Pass CYP3A-Mediated Metabolism of Midazolam in the Gut Wall and Liver in Preterm Neonates

To predict first‐pass and systemic cytochrome P450 (CYP) 3A‐mediated metabolism of midazolam in preterm neonates, a physiological population pharmacokinetic model was developed describing intestinal and hepatic midazolam clearance in preterm infants. On the basis of midazolam and 1‐OH‐midazolam concentrations from 37 preterm neonates (gestational age 26–34 weeks) receiving midazolam orally and/or via a 30‐minute intravenous infusion, intrinsic clearance in the gut wall and liver were found to be very low, with lower values in the gut wall (0.0196 and 6.7 L/h, respectively). This results in a highly variable and high total oral bioavailability of 92.1% (range, 67–95%) in preterm neonates, whereas this is around 30% in adults. This approach in which intestinal and hepatic clearance were separately estimated shows that the high bioavailability in preterm neonates is explained by, likely age‐related, low CYP3A activity in the liver and even lower CYP3A activity in the gut wall.

Nasal midazolam vs ketamine for neonatal intubation in the delivery room: a randomised trial

OBJECTIVE

To compare the effectiveness of sedation by intranasal administration of midazolam (nMDZ) or ketamine (nKTM) for neonatal intubation.

DESIGN

A multicentre, prospective, randomised, double-blind study.

SETTING

Delivery rooms at four tertiary perinatal centres in France.

PATIENTS

Preterm neonates with respiratory distress requiring non-emergent endotracheal intubation for surfactant instillation.

INTERVENTIONS

Treatment was randomly allocated, with each neonate receiving a bolus of 0.1 mL/kg in each nostril, corresponding to 0.2 mg/kg for nMDZ and 2 mg/kg for nKTM. The drug was repeated once 7 min later at the same dose if adequate sedation was not obtained.

MAIN OUTCOME MEASURES

Success was defined by adequate sedation before intubation and adequate comfort during the procedure. Intubation features, respiratory and cardiovascular events were recorded.

RESULTS

Sixty newborns, with mean (SD) gestational age and birth weight of 28 (3) weeks and 1100 (350) g, were included within the first 20 min of life. nMDZ was associated with a higher success rate (89% vs 58%; RR: 1.54, 95% CI 1.12 to 2.12, p<0.01) and shorter delays between the first dose and intubation (10 (6) vs 16 (8) min, p<0.01).Number of attempts, time to intubation, mean arterial blood pressure measures over the first 12 hours after birth and length of invasive ventilation were not different.

CONCLUSIONS

nMDZ was more efficient than nKTM to adequately sedate neonates requiring intubation in the delivery room. The haemodynamic and respiratory effects of both drugs were comparable.

CLINICAL TRIAL

This clinical trial was recorded on the National Library of Medicine registry (NCT01517828).

Trends in narcotics and sedative use during mechanical ventilation of preterm infants in Canadian neonatal intensive care units

OBJECTIVE

Mechanical ventilation (MV) in preterm infants (PTI) causes discomfort. Whether it causes pain is controversial. Meta analysis reviews of published work on PTI during MV have shown no clinically significant impact of opioids on pain scales, and hence not recommended for routine use in neonatal intensive care units (NICUs). Similarly regular use of sedative midazolam is also not recommended. Therefore we hypothesized a downward trend in narcotics and sedatives used in MV of PTI in NICUs. This study aimed to assess trends of sedatives and narcotics use during MV of PTI in Canadian NICUs during 2004-2009.

METHODS

PTI born at gestational age (GA) of <35 weeks requiring invasive MV for >24 hours were identified retrospectively from the Canadian Neonatal Network database for 2004-2009. PTI were excluded if moribund on admission, had major congenital anomalies, surgery (except laser eye surgery), necrotizing enterocolitis, chest tube or history of maternal narcotic abuse. PTI were classified according to whether they received any narcotics (morphine, fentanyl, methadone, sufentanyl, meperidine, alfentynl and codiene) or sedatives (chloral hydrate, midazolam, lorazepam, phenobarbital, pentobarbital, ketamine and propofol) for >24 consecutive hours during MV. Trends of narcotics and sedatives were assessed using the Cochrane-Armitage Trend test separately for PTI born at <29 and 29-34 weeks of GA.

RESULTS

Among 5 638 study subjects, 2 169 (38.5%) received narcotics and 897 (15.9%) received sedatives. The most common narcotics were morphine (62.2%) and fentanyl (63.8%) and sedatives were phenobarbital (44.9%) and chloral hydrate (44.2%). A significant decreasing trend (P<0.01) in the use of any sedatives during MV was observed in PTI <29 and 29-34 weeks of GA. However, the use of any narcotics during MV increased significantly (P=0.03) among PTI <29 weeks of GA, and no change in trend was detected for PTI born at 29-34 weeks of GA.

CONCLUSIONS

The use of sedatives during MV in PTI born at <35 weeks of GA was positively affected, however the narcotics use during MV remained constant for PTI born at 29-34 weeks, and increased in extremely low GA group (less than 29 weeks) suggesting evidence based practice change was not observed during the study period.

[A survey on premedication prior to intubation in very preterm infants (28-32WG) with respiratory distress syndrome in French neonatal intensive care units]

INTRODUCTION/OBJECTIVES

Tracheal intubation is a painful procedure for which the routine use of analgesia is recommended. However, the use of premedication for intubation is not yet generalized and there is great diversity in the drugs used. The main objective of this study was to describe the frequency of premedication use in preterm neonates aged between 28 and 32weeks of gestation, intubated for respiratory distress syndrome. Secondary objectives were to describe the existence of a written protocol, its influence on the frequency of premedication and the drugs used.

MATERIALS AND METHODS

Declarative survey on Google.docs forms addressed to physicians and residents working in neonatal intensive care units in France.

RESULTS

One hundred thirty respondents from 64 units completed this survey between 1 June and 31 July 2014. Fifty-seven percent of respondents declared always using a premedication, and 64 % of participants had a written protocol in their units. Persons working in a unit with a written protocol more frequently reported using premedication (P=0.04). The drugs used were various (mostly a hypnotic/morphine combination) and their dosages scattered.

DISCUSSION

The results found by this survey confirm data from the literature and the situation seems to have stagnated over the last few years. A written protocol might encourage premedication use.

CONCLUSION

Improvements in practices and increased knowledge are required to generalize the sedation/analgesia practices for tracheal intubation in neonatal intensive care units in France.

Intravenous midazolam infusion for sedation of infants in the neonatal intensive care unit

BACKGROUND

Proper sedation for neonates undergoing uncomfortable procedures may reduce stress and avoid complications. Midazolam is a short-acting benzodiazepine that is used increasingly in neonatal intensive care units (NICUs). However, its effectiveness as a sedative in neonates has not been systematically evaluated.

OBJECTIVES

Primary objeciveTo assess the effectiveness of intravenous midazolam infusion for sedation, as evaluated by behavioural and/or physiological measurements of sedation levels, in critically ill neonates in the NICU. Secondary objectivesTo assess effects of intravenous midazolam infusion for sedation on complications including the following.1. Incidence of intraventricular haemorrhage (IVH)/periventricular leukomalacia (PVL).2. Mortality.3. Occurrence of adverse effects associated with the use of midazolam (hypotension, neurological abnormalities).4. Days of ventilation.5. Days of supplemental oxygen.6. Incidence of pneumothorax.7. Length of NICU stay (days).8. Long-term neurodevelopmental outcomes.

SELECTION CRITERIA

We selected for review randomised and quasi-randomised controlled trials of intravenous midazolam infusion for sedation in infants aged 28 days or younger.

DATA COLLECTION AND ANALYSIS

We abstracted data regarding the primary outcome of level of sedation. We assessed secondary outcomes such as intraventricular haemorrhage, periventricular leukomalacia, death, length of NICU stay and adverse effects associated with midazolam. When appropriate, we performed meta-analyses using risk ratios (RRs) and risk differences (RDs), and if the RD was statistically significant, we calculated the number needed to treat for an additional beneficial outcome (NNTB) or an additional harmful outcome (NNTH), along with their 95% confidence intervals (95% CIs) for categorical variables, and weighted mean differences (WMDs) for continuous variables. We assessed heterogeneity by performing the I-squared (I2) test.

MAIN RESULTS

We included in the review three trials enrolling 148 neonates. We identified no new trials for this update. Using different sedation scales, each study showed a statistically significantly higher sedation level in the midazolam group compared with the placebo group. However, none of the sedation scales used have been validated in preterm infants; therefore, we could not ascertain the effectiveness of midazolam in this population. Duration of NICU stay was significantly longer in the midazolam group than in the placebo group (WMD 5.4 days, 95% CI 0.40 to 10.5; I2 = 0%; two studies, 89 infants). One study (43 infants) reported significantly lower Premature Infant Pain Profile (PIPP) scores during midazolam infusion than during dextrose (placebo) infusion (MD -3.80, 95% CI -5.93 to -1.67). Another study (46 infants) observed a higher incidence of adverse neurological events at 28 days' postnatal age (death, grade III or IV IVH or PVL) in the midazolam group compared with the morphine group (RR 7.64, 95% CI 1.02 to 57.21; RD 0.28, 95% CI 0.07 to 0.49; NNTH 4, 95% CI 2 to 14) (tests for heterogeneity not applicable). We considered these trials to be of moderate quality according to GRADE assessment based on the following outcomes: mortality during hospital stay, length of NICU stay, adequacy of analgesia according to PIPP scores and poor neurological outcomes by 28 days' postnatal age.

AUTHORS' CONCLUSIONS

Data are insufficient to promote the use of intravenous midazolam infusion as a sedative for neonates undergoing intensive care. This review raises concerns about the safety of midazolam in neonates. Further research on the effectiveness and safety of midazolam in neonates is needed.

Scaling clearance in paediatric pharmacokinetics: All models are wrong, which are useful?

Linked Articles

This article is commented on in the editorial by Holford NHG and Anderson BJ. Why standards are useful for predicting doses. Br J Clin Pharmacol 2017; 83: 685–7. doi: 10.1111/bcp.13230

Aim

When different models for weight and age are used in paediatric pharmacokinetic studies it is difficult to compare parameters between studies or perform model‐based meta‐analyses. This study aimed to compare published models with the proposed standard model (allometric weight^0.75 and sigmoidal maturation function).

Methods

A systematic literature search was undertaken to identify published clearance (CL) reports for gentamicin and midazolam and all published models for scaling clearance in children. Each model was fitted to the CL values for gentamicin and midazolam, and the results compared with the standard model (allometric weight exponent of 0.75, along with a sigmoidal maturation function estimating the time in weeks of postmenstrual age to reach half the mature value and a shape parameter). For comparison, we also looked at allometric size models with no age effect, the influence of estimating the allometric exponent in the standard model and, for gentamicin, using a fixed allometric exponent of 0.632 as per a study on glomerular filtration rate maturation. Akaike information criteria (AIC) and visual predictive checks were used for evaluation.

Results

No model gave an improved AIC in all age groups, but one model for gentamicin and three models for midazolam gave slightly improved global AIC fits albeit using more parameters: AIC drop (number of parameters), –4.1 (5), –9.2 (4), –10.8 (5) and –10.1 (5), respectively. The 95% confidence interval of estimated CL for all top performing models overlapped.

Conclusion

No evidence to reject the standard model was found; given the benefits of standardised parameterisation, its use should therefore be recommended.

Anticonvulsant effectiveness and hemodynamic safety of midazolam in full-term infants treated with hypothermia

BACKGROUND

Midazolam is used as an anticonvulsant in neonatology, including newborns with perinatal asphyxia treated with hypothermia. Hypothermia may affect the safety and effectiveness of midazolam in these patients.

OBJECTIVES

The objective was to evaluate the anticonvulsant effectiveness and hemodynamic safety of midazolam in hypothermic newborns and to provide dosing guidance.

METHODS

Hypothermic newborns with perinatal asphyxia and treated with midazolam were included. Effectiveness was studied using continuous amplitude-integrated electroencephalography. Hemodynamic safety was assessed using pharmacokinetic-pharmacodynamic modeling with plasma samples and blood pressure recordings (mean arterial blood pressure) under hypothermia.

RESULTS

No effect of therapeutic hypothermia on pharmacokinetics could be identified. Add-on seizure control with midazolam was limited (23% seizure control). An inverse relationship between the midazolam plasma concentration and mean arterial blood pressure could be identified. At least one hypotensive episode was experienced in 64%. The concomitant use of inotropes decreased midazolam clearance by 33%.

CONCLUSIONS

Under therapeutic hypothermia, midazolam has limited add-on clinical anticonvulsant effectiveness after phenobarbital administration. Due to occurrence of hypotension requiring inotropic support, midazolam is less suitable as a second-line anticonvulsant drug under hypothermia.

Inter-individual variation in midazolam clearance in children

OBJECTIVES

To determine the extent of inter-individual variation in clearance of midazolam in children and establish which factors are responsible for this variation.

METHODS

A systematic literature review was performed to identify papers describing the clearance of midazolam in children. The following databases were searched: Medline, Embase, International Pharmaceutical Abstracts, CINAHL and Cochrane Library. From the papers, the range in plasma clearance and the coefficient of variation (CV) in plasma clearance were determined.

RESULTS

25 articles were identified. Only 13 studies gave the full range of clearance values for individual patients. The CV was greater in critically ill patients (18%-170%) than non-critically ill patients (13%-54%). Inter-individual variation was a major problem in all age groups of critically ill patients. The CV was 72%-106% in preterm neonates, 18%-73% in term neonates, 31%-130% in infants, 21%-170% in children and 47%-150% in adolescents. The mean clearance was higher in children (1.1-16.7 mL/min/kg) than in neonates (0.78-2.5 mL/min/kg).

CONCLUSIONS

Large inter-individual variation was seen in midazolam clearance values in critically ill neonates, infants, children and adolescents.

Neonatal pain control and neurologic effects of anesthetics and sedatives in preterm infants

Preclinical and clinical studies have demonstrated the adverse consequences of untreated pain and stress on brain development in the preterm infant. Sucrose has widely been implemented as standard therapy for minor procedural pain. Anesthetics are commonly utilized in preterm infants during major surgery. Pharmacologic agents (benzodiazepines and opioids) have been examined in clinical trials of preterm infants requiring invasive mechanical ventilation. Controversy exists regarding the safety and long-term impact of these interventions. Ongoing multidisciplinary research will help define the impact of these agents and identify potential alternative therapies.

Clinical pharmacology of midazolam in neonates and children: effect of disease-a review

Midazolam is a benzodiazepine with rapid onset of action and short duration of effect. In healthy neonates the half-life (t_1/2) and the clearance (Cl) are 3.3-fold longer and 3.7-fold smaller, respectively, than in adults. The volume of distribution (Vd) is 1.1 L/kg both in neonates and adults. Midazolam is hydroxylated by CYP3A4 and CYP3A5; the activities of these enzymes surge in the liver in the first weeks of life and thus the metabolic rate of midazolam is lower in neonates than in adults. Midazolam acts as a sedative, as an antiepileptic, for those infants who are refractory to standard antiepileptic therapy, and as an anaesthetic. Information of midazolam as an anaesthetic in infants are very little. Midazolam is usually administered intravenously; when minimal sedation is required, intranasal administration of midazolam is employed. Disease affects the pharmacokinetics of midazolam in neonates; multiple organ failure reduces the Cl of midazolam and mechanical ventilation prolongs the t_1/2 of this drug. ECMO therapy increases t_1/2, Cl, and Vd of midazolam several times. The adverse effects of midazolam in neonates are scarce: pain, tenderness, and thrombophlebitis may occur. Respiratory depression and hypotension appear in a limited percentage of infants following intravenous infusion of midazolam. In conclusion, midazolam is a safe and effective drug which is employed as a sedative, as antiepileptic agent, for infants who are refractory to standard antiepileptic therapy, and as an anaesthetic.

Intubation in the delivery room: experience with nasal midazolam

BACKGROUND

Neonates are often intubated in the delivery room (DR) without anesthesia because vascular access is impossible.

AIMS

To assess neonatal comfort and adverse events after use of nasal midazolam (nMDZ) for intubation in the DR.

STUDY DESIGN

Prospective data collection over 6months on the intubation of neonates with respiratory distress requiring tracheal instillation of surfactant.

SUBJECTS

Twenty-seven neonates with median (Q25-75) gestational age and birthweight of, respectively, 29 (27-33)weeks and 1270 (817-1942)g received a 0.1mg/kg dose of nMDZ, and intubation was performed at the onset of tonus resolution or apnea.

OUTCOME MEASURES

Comfort was assessed with a scale of hetero-pain assessment and electrical skin conductance monitoring. Continuous pulse oximetry was recorded in the first postnatal hour, with oscillometric blood pressure measurement every 10min.

RESULTS

Seventy percent of the patients required a single dose, with intubation performed 4.8 (3-9)min after administration. Combined electro-clinical assessment found adequate comfort during the procedure in 68% of neonates. Mean blood pressure decreased from 39 (34-44)mmHg before to 31 (25-33)mmHg 1h following nMDZ (p=0.011).

CONCLUSION

nMDZ provided rapid and effective sedation to intubate neonates in the DR but potentially exposed them to hypotension, thus requiring close hemodynamic monitoring.

Population pharmacokinetic analysis during the first 2 years of life: an overview

Three decades after its introduction, pharmacokinetic population approaches have become a reference method for drug modelling, particularly in paediatrics. The main practical limitation in this specific population is the collected blood volume. Pharmacokinetic population approaches using sparse sampling may resolve this issue. The pharmacokinetics of many drugs have been studied during the last 25 years using such methods. This review summarizes all of the published studies concerning population pharmacokinetic approaches in paediatric subjects from neonate to 2 years old. A literature search was conducted using the PubMed database, from 1985 to December 2010, using the following terms: pharmacokinetic(s), population, paediatric/pediatric and neonate(s). Articles were excluded if they were not pertinent according to our criteria. References of all relevant articles were also evaluated. Ninety-eight studies were included in this review. The following information was extracted from the articles: drug name, therapeutic class, population size, age of patients, number of samples per patient, covariates used for clearance and volume of distribution estimates, software used for modelling and validation methods. An increasing rate of publications over the years was observed; 44 different drugs were studied using a pharmacokinetic population approach. Antibacterials were the most studied class of drugs, including a large number of studies devoted to vancomycin and gentamicin. It must be underlined that few studies have been performed on anticonvulsant drugs and anaesthetics used in clinical daily practice conditions.

Premedication for neonatal intubation: Current practice in Saudi Arabia

BACKGROUND

Despite strong evidence of the benefits of rapid sequence intubation in neonates, it is still infrequently utilized in neonatal intensive care units (NICU), contributing to avoidable pain and secondary procedure-related physiological disturbances.

OBJECTIVES

The primary objective of this cross-sectional survey was to assess the practice of premedication and regimens commonly used before elective endotracheal intubation in NICUs in Saudi Arabia. The secondary aim was to explore neonatal physicians' attitudes regarding this intervention in institutions across Saudi Arabia.

METHODS

A web-based, structured questionnaire was distributed by the Department of Pediatrics, Umm Al Qura University, Mecca, to neonatal physicians and consultants of 10 NICUs across the country by E-mail. Responses were tabulated and descriptive statistics were conducted on the variables extracted.

RESULTS

85% responded to the survey. Although 70% believed it was essential to routinely use premedication for all elective intubations, only 41% implemented this strategy. 60% cited fear of potential side effects for avoiding premedication and 40% indicated that the procedure could be executed more rapidly without drug therapy. Treatment regimens varied widely among respondents.

CONCLUSION

Rates of premedication use prior to non-emergent neonatal intubation are suboptimal. Flawed information and lack of unified unit policies hampered effective implementation. Evidence-based guidelines may influence country-wide adoption of this practice.

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.

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.

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.

Premedication for endotracheal intubation in the newborn infant

Endotracheal intubation, a common procedure in newborn care, is associated with pain and cardiorespiratory instability. The use of premedication reduces the adverse physiological responses of bradycardia, systemic hypertension, intracranial hypertension and hypoxia. Perhaps more importantly, premedication decreases the pain and discomfort associated with the procedure. All newborn infants, therefore, should receive analgesic premedication for endotracheal intubation except in emergency situations. Based on current evidence, an optimal protocol for premedication is to administer a vagolytic (intravenous [IV] atropine 20 μg/kg), a rapid-acting analgesic (IV fentanyl 3 μg/kg to 5 μg/kg; slow infusion) and a short-duration muscle relaxant (IV succinylcholine 2 mg/kg). Intubations should be performed or supervised by trained staff, with close monitoring of the infant throughout.

Intravenous midazolam infusion for sedation of infants in the neonatal intensive care unit

BACKGROUND

Proper sedation for neonates undergoing uncomfortable procedures may reduce stress and avoid complications. Midazolam is a short-acting benzodiazepine that is increasingly used in neonatal intensive care units (NICU). However, its effectiveness as a sedative in neonates has not been systematically evaluated.

OBJECTIVES

To determine whether intravenous midazolam infusion is an effective sedative, as evaluated by behavioural or physiological measurements, or both, for critically ill neonates undergoing intensive care and to assess clinically significant short- and long-term adverse effects associated with its use.

SEARCH METHODS

We performed a literature search according to the Cochrane Neonatal Review Group search strategy. Randomised and quasi-randomised controlled trials of intravenous midazolam use in neonates were identified by searching the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2012), MEDLINE (1985 to 2012), EMBASE (1980 to 2012), CINAHL (1981 to 2012), reference lists of published studies, personal files, and abstracts published in The Pediatric Academic Societies Meeting Abstract Archives from 1990 to 2011.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of intravenous midazolam infusion in infants aged 28 days or less for sedation were selected for review.

DATA COLLECTION AND ANALYSIS

Data regarding the primary outcome of level of sedation were abstracted. Secondary outcomes such as intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL), death, length of NICU stay, and adverse effects associated with midazolam were assessed. When appropriate, meta-analyses were performed using risk ratio (RR), risk difference (RD), along with their 95% confidence intervals (95% CI) for categorical variables and weighted mean difference (WMD) for continuous variables.

MAIN RESULTS

Three trials were included in the review. Using different sedation scales, each study showed a statistically significantly higher sedation level in the midazolam group compared to the placebo group. However, since none of the sedation scales used have been validated in preterm infants, the effectiveness of midazolam in this population could not be ascertained. One study showed a statistically significant higher incidence of adverse neurological events (death, grade III or IV IVH, PVL), and meta-analysis of data from two studies showed a statistically significant longer duration of NICU stay in the midazolam group compared to the placebo group.

AUTHORS' CONCLUSIONS

There are insufficient data to promote the use of intravenous midazolam infusion as a sedative for neonates undergoing intensive care. This review raises concerns about the safety of midazolam in neonates. Further research on the effectiveness and safety of midazolam in neonates is needed.

A maturation model for midazolam clearance

BACKGROUND

Physiological-based pharmacokinetic models have been used to describe midazolam clearance (CL) maturation. There are no maturation descriptors of CL from neonate to adulthood based on reported estimates at different ages.

METHODS

Published CL estimates after intravenous administration from time-concentration profiles were used to construct a maturation model based on size and age. Curve fitting was performed using nonlinear mixed effects models.

RESULTS

There were 16 publications reporting an estimate of CL after intravenous administration in children, although few estimates were available from 44-80 weeks postmenstrual age (PMA). CL maturation, standardized to a 70 -kg person was described using the Hill equation. Mature CL was 523 (CV 32%, 95%CI 469, 597) ml·min(-1) ·70 kg(-1) . The maturation half-time was 73.6 (95%CI 59.4, 80.0) weeks PMA and the Hill coefficient 3 (95%CI 2.2, 4.1). Predicted CL changes with age based on this model were in close agreement with physiologically based pharmacokinetic (PBPK) models. A comparison with a published PBPK model predictions revealed a root mean squared prediction error (precision) of 4.0% (95%CI 1.1, 5.8) and bias was -0.9% (95%CI -4.3, 2.6).

CONCLUSIONS

Previously published pharmacokinetic parameters can be used to develop maturation models that address gaps in current knowledge regarding the influence of age on a drug's disposition. If a midazolam sedation target concentration of 0.1 mg·l(-1) , similar to that given to adults, is assumed, then we might anticipate steady-state infusion rates of 0.014 mg·kg(-1) ·h(-1) in neonates, 0.05 mg·kg(-1) ·h(-1) in a 1-year-old, 0.06 mg·kg(-1) ·h(-1) in a 5-year-old and 0.05 mg·kg(-1) ·h(-1) in a 12-year-old child. Age-related pharmacodynamic differences that will affect dose and the impact of active metabolites on response are not yet quantified.

Premedication for nonemergency endotracheal intubation in the neonate

Endotracheal intubation is a common procedure in newborn care. The purpose of this clinical report is to review currently available evidence on use of premedication for intubation, identify gaps in knowledge, and provide guidance for making decisions about the use of premedication.

Use of analgesic and sedative drugs in the NICU: integrating clinical trials and laboratory data

Recent advances in neonatal intensive care include and are partly attributable to growing attention for comfort and pain control in the term and preterm infant requiring intensive care.Limitation of painful procedures is certainly possible, but most critically ill infants require unavoidable painful or stressful procedures such as intubation, mechanical ventilation, or catheterization.Many analgesics (opioids and nonsteroidal anti-inflammatory drugs)and sedatives (benzodiazepines and other anesthetic agents) are available but their use varies considerably among units. This review summarizes current experimental knowledge on the effects of sedative and analgesic drugs on brain development and reviews clinical evidence that speaks for or against the use of common analgesic and sedative drugs in the NICU but avoids any discussion of anesthesia during surgery. Risk/benefit ratios of intermittent boluses or continuous infusions for the commonly used sedative and analgesic agents are discussed in the light of clinical and experimental studies. The limitations of extrapolating experimental results from animals to humans must be considered while making practical recommendations based on the currently available evidence.

Impact of anesthetic agents on cerebrovascular physiology in children

The role of the pediatric neuroanesthetist is to provide comprehensive care to children with neurologic pathologies. The cerebral physiology is influenced by the developmental stage of the child. The understanding of the effects of anesthetic agents on the physiology of cerebral vasculature in the pediatric population has significantly increased in the past decade allowing a more rationale decision making in anesthesia management. Although no single anesthetic technique can be recommended, sound knowledge of the principles of cerebral physiology and anesthetic neuropharmacology will facilitate the care of pediatric neurosurgical patients.

Betamethasone impairs cerebral blood flow velocities in very premature infants with severe chronic lung disease

OBJECTIVE

To assess betamethasone (BM) effects on the cerebral hemodynamics of neonates with severe chronic lung disease (CLD).

STUDY DESIGN

Intravenous BM was given once daily for 6 consecutive days to 12 infants (birth weight: 698 g [range, 650-884 g], gestational age: 25.3 weeks [range, 25-26.4 weeks]) at a postnatal age of 34 days (range, 28-36 days). Cerebral blood flow velocities (CBFVs) were recorded prospectively in the anterior cerebral artery (ACA) and the lenticulostriate artery (LSA) before, during, and after treatment, using Doppler flowmetry.

RESULTS

The decrease in systolic and diastolic velocities was maximum on the 5th day, reaching 32% (95% confidence interval [CI], 23%-42%) and 58% (95% CI, 39%-64%) from baseline in the ACA, and 44% (95% CI, 29%-50%) and 57% (95% CI, 33%-66%) in the LSA, respectively. The resistance index (RI) increased significantly in both arteries during treatment. Return to baseline values was observed after BM was stopped. The change in velocities and RI was independent of arterial blood gas and blood pressure variations.

CONCLUSIONS

BM decreased the CBFVs of premature infants, suggesting a vasoconstrictor effect in both superficial and deep arterial vessels. Caution is recommended when BM is used to treat preterm infants with severe CLD.

Effects of Midazolam and Morphine on Cerebral Oxygenation and Hemodynamics in Ventilated Premature Infants

BACKGROUND

Midazolam sedation and morphine analgesia are commonly used in ventilated premature infants.

OBJECTIVES

To evaluate the effects of midazolam versus morphine infusion on cerebral oxygenation and hemodynamics in ventilated premature infants.

METHODS

11 patients (GA 26.6-33.0 weeks, BW 780-2,335 g) were sedated with midazolam (loading dose 0.2 mg/kg, maintenance 0.2 mg/kg/h) and 10 patients (GA 26.4-33.3 weeks, BW 842-1,955 g) were sedated with morphine (loading dose 0.05 mg/kg, maintenance 0.01 mg/kg/h). Changes in oxyhemoglobin (Delta cO2Hb) and deoxyhemoglobin (Delta cHHb) were assessed using near infrared spectrophotometry. Changes in cHbD (= Delta cO(2)Hb - Delta cHHb) reflect changes in cerebral blood oxygenation and changes in concentration of total hemoglobin (Delta ctHb = Delta cO2Hb + Delta cHHb) represent changes in cerebral blood volume (DeltaCBV). Changes in cerebral blood flow velocity (DeltaCBFV) were intermittently measured using Doppler ultrasound. Heart rate (HR), mean arterial blood pressure (MABP), arterial oxygen saturation (saO2) and transcutaneous measured pO2 (tcpO2) and pCO2 (tcpCO2) were continuously registered. Statistical analyses were carried out using linear mixed models to account for the longitudinal character study design.

RESULTS

Within 15 min after the loading dose of midazolam, a decrease in saO2, tcpO2 and cHbD was observed in 5/11 infants. In addition, a fall in MABP and CBFV was observed 15 min after midazolam administration. Immediately after morphine infusion a decrease in saO2, tcpO2 and cHbD was observed in 6/10 infants. Furthermore, morphine infusion resulted in a persistent increase in CBV.

CONCLUSIONS

Administration of midazolam and morphine in ventilated premature infants causes significant changes in cerebral oxygenation and hemodynamics, which might be harmful.

Analgesia and local anesthesia during invasive procedures in the neonate

BACKGROUND

Preterm and full-term neonates admitted to the neonatal intensive care unit or elsewhere in the hospital are routinely subjected to invasive procedures that can cause acute pain. Despite published data on the complex behavioral, physiologic, and biochemical responses of these neonates and the detrimental short- and long-term clinical outcomes of exposure to repetitive pain, clinical use of pain-control measures in neonates undergoing invasive procedures remains sporadic and suboptimal. As part of the Newborn Drug Development Initiative, the US Food and Drug Administration and the National Institute of Child Health and Human Development invited a group of international experts to form the Neonatal Pain Control Group to review the therapeutic options for pain management associated with the most commonly performed invasive procedures in neonates and to identify research priorities in this area.

OBJECTIVE

The goal of this article was to review and synthesize the published clinical evidence for the management of pain caused by invasive procedures in preterm and full-term neonates.

METHODS

Clinical studies examining various therapies for procedural pain in neonates were identified by searches of MEDLINE (1980-2004), the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2004), the reference lists of review articles, and personal files. The search terms included specific drug names, infant-newborn, infant-preterm, and pain, using the explode function for each key word. The English-language literature was reviewed, and case reports and small case series were discarded.

RESULTS

The most commonly performed invasive procedures in neonates included heel lancing, venipuncture, IV or arterial cannulation, chest tube placement, tracheal intubation or suctioning, lumbar puncture, circumcision, and SC or IM injection. Various drug classes were examined critically, including opioid analgesics, sedative/hypnotic drugs, nonsteroidal anti-inflammatory drugs and acetaminophen, injectable and topical local anesthetics, and sucrose. Research considerations related to each drug category were identified, potential obstacles to the systematic study of these drugs were discussed, and current gaps in knowledge were enumerated to define future research needs. Discussions relating to the optimal design for and ethical constraints on the study of neonatal pain will be published separately. Well-designed clinical trials investigating currently available and new therapies for acute pain in neonates will provide the scientific framework for effective pain management in neonates undergoing invasive procedures.

Analgesia and sedation during mechanical ventilation in neonates

BACKGROUND

Endotracheal intubation and mechanical ventilation are major components of routine intensive care for very low birth weight newborns and sick full-term newborns. These procedures are associated with physiologic, biochemical, and clinical responses indicating pain and stress in the newborn. Most neonates receive some form of analgesia and sedation during mechanical ventilation, although there are marked variations in clinical practice. Clinical guidelines for pharmacologic analgesia and sedation in newborns based on robust scientific data are lacking, as are measures of clinical efficacy.

OBJECTIVE

This article represents a preliminary attempt to develop a scientific rationale for analgesia sedation in mechanically ventilated newborns based on a systematic analysis of published clinical trials.

METHODS

The current literature was reviewed with regard to the use of opioids (fentanyl, morphine, diamorphine), sedative-hypnotics (midazolam), nonsteroidal anti-inflammatory drugs (ibuprofen, indomethacin), and acetaminophen in ventilated neonates. Original meta-analyses were conducted that collated the data from randomized clinical comparisons of morphine or fentanyl with placebo, or morphine with fentanyl.

RESULTS

The results of randomized trials comparing fentanyl, morphine, or midazolam with placebo, and fentanyl with morphine were inconclusive because of small sample sizes. Meta-analyses of the randomized controlled trials indicated that morphine and fentanyl can reduce behavioral and physiologic measures of pain and stress in mechanically ventilated preterm neonates but may prolong the duration of ventilation or produce other adverse effects. Randomized trials of midazolam compared with placebo reported significant adverse effects (P < 0.05) and no apparent clinical benefit; the findings of a meta-analysis suggest that there are insufficient data to justify use of IV midazolam for sedation in ventilated neonates.

CONCLUSIONS

Despite ongoing research in this area, huge gaps in our knowledge remain. Well-designed and adequately powered clinical trials are needed to establish the safety, efficacy, and short- and long-term outcomes of analgesia and sedation in the mechanically ventilated newborn.

Minimum effective dose of midazolam for sedation of mechanically ventilated neonates

OBJECTIVE

To determine the minimal effective dose (MED) of intravenous midazolam, required for appropriate sedation in 95% of patients, 1 h after drug administration.

METHODS

A double-blind dose-finding study using the continual reassessment method, a Bayesian sequential design. Twenty-three newborn infants hospitalized in intensive care unit participated. Inclusion criteria were: (i) post-natal age <28 days, (ii) gestational age >33 weeks, (iii) intubation and ventilatory support required for respiratory distress syndrome, (iv) need for sedation (i.e. one of the six following criteria: agitation or grimacing or crying facial expression before tracheal suctioning, agitation or grimacing or crying facial expression during tracheal suctioning). Each neonate was allocated to a loading dose, ranging from 75 to 200 microg/kg, and a maintenance dose ranging from 37.5 to 100 microg/kg/h.

RESULTS

The primary endpoint was the level of sedation 1 h after the onset of infusion. The sedation procedure was classified as a success if all the following clinical criteria were met: no agitation, no grimacing and no crying facial expression before as well as during tracheal suctioning. Based on the 23 patients, the final estimated probability of success was 76.9% (95% credibility interval: 56.6-91.4%) for the 200 microg/kg loading dose. no significant adverse effect was observed.

CONCLUSIONS

Continual reassessment is a new approach, suitable for dose-finding study in neonates. this method overcomes some of the ethical, statistical and practical problems associated with this population. Using this method, the MED was estimated to be the 200 mug/kg loading dose of midazolam.

Anaesthetic considerations for the management of very low and extremely low birth weight infants

The opportunities for very low birth weight infants (birth weight < 1500 g) and extremely low birth weight infants (birth weight < 1000 g) to undergo surgery are increasing. These infants are prone to prematurity-related morbidities including respiratory distress syndrome, intraventricular haemorrhage, periventricular leukomalacia, retinopathy of prematurity, patent ductus arteriosus and necrotising enterocolitis. Evidence is accumulating that preterm infants are also sensitive to pain and stress. The pharmacokinetics of drugs in preterm infants is not fully understood but smaller doses of anaesthetic drugs are usually required in preterm infants compared to term infants and older children and their effects last longer due to low clearance rates and longer elimination half-lives. Key anaesthetic considerations are (i) inspired oxygen concentration that should be adjusted to avoid hyperoxia, (ii) haemodynamic parameters that should be kept stable and (iii) prevention of hypothermia by using adequate measures to keep the infants warm. These precautions must be continuously taken during the operation and the transport to and from the operating theatre.

Intravenous midazolam infusion for sedation of infants in the neonatal intensive care unit

BACKGROUND

The need for sedation for neonates undergoing uncomfortable procedures in the neonatal intensive care unit (NICU) has often been overlooked. Proper sedation may reduce stress and avoid complications during procedures such as mechanical ventilation. Midazolam is a short acting benzodiazepine that has been increasingly used in the NICU. However, the effectiveness of intravenous midazolam as a sedative in neonates has not been systematically evaluated.

OBJECTIVES

To determine whether intravenous midazolam infusion is an effective sedative, as evaluated by behavioural and/or physiologic measurements, for critically ill neonates undergoing intensive care, and to assess clinically significant short and long term adverse effects associated with its use.

SEARCH STRATEGY

Literature search according to the Cochrane Neonatal Review Group search strategy. Randomized and quasi-randomized controlled trials of intravenous midazolam use in neonates were identified by searching the Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2002), MEDLINE (1985-2002), EMBASE (1980-2002), reference lists of published studies, personal files, and abstracts published in Pediatric Research from 1990-2002.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials of intravenous midazolam infusion in infants </= 28 days of age for sedation during mechanical ventilation or radiologic investigations were selected for review. Studies on midazolam use as an anesthetic or an anticonvulsant were excluded. Studies involving neonates and older infants and children were excluded if data for neonates could not be extracted.

DATA COLLECTION AND ANALYSIS

Data regarding the primary outcome of level of sedation (as evaluated by behavioural scales or physiologic parameters) were abstracted. Secondary outcomes including intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), death within 28 days of age, adverse effects associated with midazolam (hemodynamic and neurologic), days of ventilation, days of supplemental oxygen use, pneumothorax, length of NICU stay, and long term neurodevelopmental outcome were assessed. When appropriate, meta-analyses were performed using relative risk (RR), risk difference (RD), along with their 95% confidence intervals (95% CI) for categorical variables and weighted mean difference (WMD) for continuous variables.

MAIN RESULTS

Three trials were eligible for inclusion in the review. Data on level of sedation from the three trials could not be combined for meta-analysis because of differences in tools used to measure sedation levels. Two studies (Jacqz-Aigrain 1994, Arya 2001) showed a statistically significantly higher level of sedation in the midazolam group compared to the placebo group. The third study (Anand 1999) comparing midazolam to morphine and placebo found no statistically significant difference in sedation level among the three groups, but a statistically significantly higher level of sedation was found in the midazolam group compared with the placebo group during the treatment infusion. However, since the sedation scales used in all three studies have not been validated in preterm infants, the effectiveness of midazolam as a sedative in this population could not be ascertained. In the study by Jacqz-Aigrain et al (Jacqz-Aigrain 1994), blood pressure was statistically significantly lower in the midazolam group than in the placebo group on days one and two, although there was no statistically significant difference in the incidence of hypotension requiring albumin or vasoactive drugs between groups. The study by Anand et al (Anand 1999) showed a statistically significant higher incidence of adverse neurologic events (death, grade III-IV IVH, PVL) in the midazolam group compared with the other groups. In addition, meta-analysis of available data from two studies (Jacqz-Aigrain 1994, Anand 1999) showed a statistically significantly longer duration of NICU stay in the midazolam group compared to the placebo group (WMD 5.4 days, 95%CI 0.4, 10.5). Meta-analyses of other secondary outcomes showed no statistically significant differences between the midazolam and placebo groups.

REVIEWER'S CONCLUSIONS

There are insufficient data to promote the use of intravenous midazolam infusion as a sedative for neonates undergoing intensive care. This review raises concerns about the safety of midazolam in neonates. Further research on the effectiveness and safety of midazolam in neonates is needed.

Plasma concentrations of midazolam in neonates receiving extracorporeal membrane oxygenation

Drug disposition is affected during extracorporeal membrane oxygenation (ECMO). This study investigates the dose-concentration relationship of midazolam in neonates requiring ECMO during continuous infusion into the circuit (extracorporeally; n = 10) and intravenously (n = 10). Data on hourly doses and sedation scores were collected for 120 hours. Plasma concentrations were analyzed at times 0, 2, 4, 6, 12, 18, and 24, and every 12 hours thereafter. Both groups were clinically similar. Mean (standard deviation) dose for all patients was 250 (185) microg/kg/h, four times greater than previously reported. Doses administered in the first 24 hours were significantly greater extracorporeally [361 (300)] compared with intravenous [258 (190) microg/kg/h, p < 0.001]. Mean (standard deviation) plasma concentrations in all patients at 24, 48, and 72 hours were 1.4 (0.9), 1.8 (1.2), and 2.6 (1.8) microg/ml, respectively. Satisfactory sedation levels were achieved in all patients. Comparison of the actual observed with predicted (simulated) midazolam concentrations suggested significant attenuation of plasma levels during the first 24 hours of ECMO. However, at 48 hours, observed concentrations exceeded those predicted, suggesting accumulation. We conclude that in the first 24 hours of ECMO, because of an expanded circulating volume and sequestration by the circuit, significantly more midazolam is required to achieve adequate sedation. Subsequently, and because of circuit saturation, maintenance doses should be reduced.

Safety of benzodiazepines in newborns

BACKGROUND

Benzodiazepines are being used in neonatal intensive care units for sedation and control of seizures. However, anecdotal reports suggest that their use in infants may be associated with serious adverse effects (AEs).

OBJECTIVE

To determine the incidence of AEs from benzodiazepine use in preterm and full-term infants.

METHODS

Retrospective chart review of 63 infants who received benzodiazepines as a sedative or anticonvulsant over a 16-month period.

RESULTS

Mean +/- SD gestational age of the infants was 33.1 +/- 6.2 weeks, and birth weight was 2.3 +/- 1.2 kg. Median (range) postnatal age at commencement of drug administration was 19 (5-54) days. Forty-one infants received lorazepam, 8 received midazolam, and 14 received both. Ten (16%) of the infants had 14 documented adverse events: seizures (n = 6), hypotension (n = 5), and respiratory depression (n = 3). Using a validated adverse drug reaction probability scale, a probable association with benzodiazepine use was demonstrated in 12 of the AEs. Due to the retrospective nature of the data, a score for definite association was not attainable. Anticonvulsant administration was required for 4 of 6 infants and, in all cases of respiratory depression, ventilatory support was initiated or increased. Two cases of significant hypotension were treated with inotropes. There was no statistically significant correlation between AEs and benzodiazepine dose or concomitant use of inotropes or analgesics (morphine), although most infants had underlying medical conditions or received multiple drugs that may have predisposed them to experience AEs.

CONCLUSIONS

Administration of benzodiazepines was frequently associated with AEs in full-term and preterm infants. It is possible that underlying illnesses and concomitant drug use predisposed these effects. Until the benefit-to-risk ratio is determined by further studies, judicious use of benzodiazepines is recommended in this vulnerable population.

Assessment and management of pain and distress in the neonate

Pain management is an integral focus of neonatal care. This article reviews the physiology and impact of neonatal pain and distress and pain assessment tools, as well as clinical interventions and current controversies in the management of pain and distress in neonates. Current guidelines to enhance the recognition and treatment of pain are highlighted.

Flumazenil's Reversal of Myoclonic-like Movements Associated with Midazolam in Term Newborns

Sedation is an important aspect of care for critically ill newborns. Proper sedation reduces stress during procedures such as mechanical ventilation. Midazolam, a short-acting benzodiazepine, is widely administered as a sedative in newborn intensive care units but is not without side effects. Three term newborns developed myoclonic-like abnormal movements after receiving midazolam. In one, flumazenil controlled the abnormal movements. Flumazenil is a potent benzodiazepine antagonist that competitively blocks the central effects of benzodiazepines. It can reverse the sedative effects of benzodiazepines occurring after diagnostic or therapeutic procedures or after benzodiazepine overdose. Flumazenil may be considered in cases of abnormal movements associated with midazolam. However, further studies are needed to provide guidelines for the administration of this drug in newborns.

Changes in cerebral venous prostanoids during midazolam-induced cerebrovascular hypotension in newborn piglets

OBJECTIVES

We hypothesized that the effects of midazolam are associated with altered prostanoid synthesis in the newborn piglet during continuous infusion. To test this hypothesis, we examined the effect of midazolam on prostanoid production in the carotid artery and sagittal sinus vein before and during midazolam infusion.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Research laboratory at Long Beach Memorial Medical Center.

SUBJECTS

Fourteen newborn piglets (1-3 days old, 1-1.5 kg) randomly assigned to receive either midazolam or vehicle (5% dextrose) infusion for 6 hrs.

INTERVENTIONS

Two groups of animals received either a) a loading dose of 300 microg/kg of midazolam over 15 mins, followed by a continuous intravenous infusion of 100 microg/kg/hr (n = 6), or b) equivalent volume bolus and intravenous infusions of 5% dextrose (control, n = 8).

MEASUREMENTS AND MAIN RESULTS

Changes in systemic and cerebral venous hemodynamics, blood gases, and prostanoid (prostaglandin E2, 6-ketoprostaglandin F1 alpha, thromboxane B2) production were measured at baseline, postbolus, and at 0.5, 2, 4, and 6 hrs. Systemic and cerebral venous midazolam concentrations were measured at 0.5, 1, 2, 3, 4, 5, and 6 hrs. Midazolam infusion did not affect systemic hemodynamics or blood gases. In contrast, midazolam infusion significantly reduced sagittal sinus vein blood pressure, PO2, oxygen saturation, and oxygen content. Cerebral fractional oxygen extraction increased and was positively correlated with cerebral fractional midazolam extraction. Concurrently, systemic and sagittal sinus vein plasma prostaglandin E2 concentrations decreased, whereas 6-ketoprostaglandin F1 alpha concentrations increased with midazolam infusion. Thromboxane B2 concentrations increased transiently in the systemic plasma.

CONCLUSIONS

Midazolam infusion preceded by a high bolus dose in newborn piglets alters systemic and sagittal sinus vein prostanoid production. It is also associated with changes in sagittal sinus vein blood pressure and cerebral fractional oxygen extraction. These changes may reflect decreased brain perfusion and metabolism during midazolam infusion.

Treatment of pain in the neonatal intensive care unit

Pain is a disruptive influence on infants in the NICU. The most obvious and effective strategy to decrease infant pain in the NICU is to stringently limit the frequency of painful procedures, especially those that are most commonly reported (i.e., heel lances and endotracheal suctioning), and have these performed on infants that are most unstable or critically ill by the most experienced person available. Organizational concerns over the cost of NICU care have forced a re-evaluation of the necessity of certain diagnostic and care procedures and a limiting of procedures to those that can be documented to positively affect clinical outcome. Pharmacologic and nonpharmacologic strategies are essential to the prevention and management of neonatal pain, and these should be considered for complementary use for every infant. Research has shown the safety and effectiveness of some of the strategies in reducing mild pain caused by brief invasive procedures; however, many of the studies had methodologic limitations. Therefore, more research is required to determine the comparative efficacy of the various strategies and to document additive or synergistic effects when combined.