Neonatal tracheal intubation: an imbroglio unresolved

Effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease: A prospective observational study

BACKGROUND

Neonates and infants with congenital heart disease undergoing general anesthesia have an increased risk for critical cardiovascular events. Etomidate produces very minimal changes in hemodynamic parameters in older children with congenital heart disease. There is a lack of studies evaluating the effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease.

AIM

The aim of this prospective observational study was to evaluate the effect of etomidate on systemic and regional cerebral perfusion in neonates and infants with congenital heart disease.

METHODS

In fifty infants aged 0-11 months (24% neonates n = 12) with congenital heart disease, mean arterial blood pressure, cardiac index using electrical cardiometry, and regional cerebral oxygen saturation using near-infrared spectroscopy were measured at baseline and 1, 3, 5, and 10 minutes after induction by 0.4 mg kg^-1 etomidate. Hypotension was defined as a mean arterial blood pressure under 35 mm Hg and cerebral desaturation as a regional cerebral oxygen saturation of less than 80% of baseline.

RESULTS

Mean arterial blood pressure, cardiac index, and regional cerebral oxygen saturation remained stable above the predefined limits. Mean arterial blood pressure decreased slightly within a physiological range after 3 minutes (P = .005, 95% CI:-5.9 to -1.0). No significant change in cardiac index could be observed.

CONCLUSION

Etomidate 0.4mg kg^-1 does not impair systemic or regional cerebral perfusion in neonates or infants with congenital heart disease.

A manual propofol infusion regimen for neonates and infants

AIMS

Manual propofol infusion regimens for neonates and infants have been determined from clinical observations in children under the age of 3 years undergoing anesthesia. We assessed the performance of these regimens using reported age-specific pharmacokinetic parameters for propofol. Where performance was poor, we propose alternative dosing regimens.

METHODS

Simulations using a reported general purpose pharmacokinetic propofol model were used to predict propofol blood plasma concentrations during manual infusion regimens recommended for children 0-3 years. Simulated steady state concentrations were 6-8 µg.mL^-1 in the first 30 minutes that were not sustained during 100 minutes infusions. Pooled clinical data (n = 161, 1902 plasma concentrations) were used to determine an alternative pharmacokinetic parameter set for propofol using nonlinear mixed effects models. A new manual infusion regimen for propofol that achieves a steady-state concentration of 3 µg.mL^-1 was determined using a heuristic approach.

RESULTS

A manual dosing regimen predicted to achieve steady-state plasma concentration of 3 µg.mL^-1 comprised a loading dose of 2 mg.kg^-1 followed by an infusion rate of 9 mg.kg^-1 .h^-1 for the first 15 minutes, 7 mg.kg^-1 .h^-1 from 15 to 30 minutes, 6 mg.kg^-1 .h^-1 from 30 to 60 minutes, 5 mg.kg^-1 .h^-1 from 1 to 2 hours in neonates (38-44 weeks postmenstrual age). Dose increased with age in those aged 1-2 years with a loading dose of 2.5 mg.kg^-1 followed by an infusion rate of 13 mg.kg^-1 .h^-1 for the first 15 minutes, 12 mg.kg^-1 .h^-1 from 15 to 30 minutes, 11 mg.kg^-1 .h^-1 from 30 to 60 minutes, and 10 mg.kg^-1 .h^-1 from 1 to 2 hours.

CONCLUSION

Propofol clearance increases throughout infancy to reach 92% that reported in adults (1.93 L.min.70 kg^-1 ) by 6 months postnatal age and infusion regimens should reflect clearance maturation and be cognizant of adverse effects from concentrations greater than the target plasma concentration. Predicted concentrations using a published general purpose pharmacokinetic propofol model were similar to those determined using a new parameter set using richer neonatal and infant data.

Practicalities of Total Intravenous Anesthesia and Target-controlled Infusion in Children

Propofol administered in conjunction with an opioid such as remifentanil is used to provide total intravenous anesthesia for children. Drugs can be given as infusion controlled manually by the physician or as automated target-controlled infusion that targets plasma or effect site. Smart pumps programmed with pharmacokinetic parameter estimates administer drugs to a preset plasma concentration. A linking rate constant parameter (keo) allows estimation of effect site concentration. There are two parameter sets, named after the first author describing them, that are commonly used in pediatric target-controlled infusion for propofol (Absalom and Kataria) and one for remifentanil (Minto). Propofol validation studies suggest that these parameter estimates are satisfactory for the majority of children. Recommended target concentrations for both propofol and remifentanil depend on the type of surgery, the degree of surgical stimulation, the use of local anesthetic blocks, and the ventilatory status of the patient. The use of processed electroencephalographic monitoring is helpful in pediatric total intravenous anesthesia and target-controlled infusion anesthesia, particularly in the presence of neuromuscular blockade.

Propofol Dose-Finding to Reach Optimal Effect for (Semi-)Elective Intubation in Neonates

OBJECTIVE

To define the effective dose for 50% of patients (ED₅₀) of propofol for successful intubation and to determine the rate of successful extubation in those patients with planned intubation, surfactant administration, and immediate extubation (INSURE procedure). In addition, pharmacodynamic effects were assessed.

STUDY DESIGN

Neonates (n = 50) treated with propofol for (semi-)elective endotracheal intubation were stratified in 8 strata by postmenstrual and postnatal age. The first patient in each stratum received an intravenous bolus of 1 mg/kg propofol. Dosing for the next patient was determined using the up-and-down method. A propofol ED₅₀ dose was calculated in each stratum with an effective sample size of at least 6, via the Dixon-Masey method, with simultaneous assessment of clinical scores and continuous vital sign monitoring.

RESULTS

Propofol ED₅₀ values for preterm neonates <10 days of age varied between 0.713 and 1.350 mg/kg. Clinical recovery was not attained at the end of the 21-minute scoring period. Mean arterial blood pressure showed a median decrease between 28.5% and 39.1% from baseline with a brief decrease in peripheral and regional cerebral oxygen saturation. Variability in mean arterial blood pressure area under the curve could not be explained by weight or age.

CONCLUSIONS

Low propofol doses were sufficient to sedate neonates for intubation. Clinical recovery was accompanied by permissive hypotension (no clinical shock and no treatment). The propofol ED₅₀ doses can be administered at induction, with subsequent up-titration if needed, while monitoring blood pressure. They can be used for further dosing optimalization and validation studies.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01621373; EudraCT: 2012-002648-26.

Blood pressure and heart rates in neonates and preschool children: an analysis from 10 years of electronic recording

BACKGROUND

An acceptable systolic or mean arterial blood pressure for children 0-6 years during anesthesia is unknown. Accepted blood pressures reported in standard charts for healthy awake children may not apply to those undergoing anesthesia.

AIM

Our goal was to define observed blood pressures (BP) and heart rate (HR) in children 0-5 years during anesthesia.

METHODS

Data from the electronic health record database were available for a 10-year period from June 29, 2005 to July 22, 2015. A simple band-pass filter was applied to remove artifact in the physiologic time-series data for heart rate and blood pressure, with heart rate values 40 or above 250, mean or diastolic blood pressures below 20 or above 200, and systolic blood pressures below 30 or above 200 all excluded. For each anesthetic, the centiles of physiological variables (BP, HR) were calculated.

RESULTS

Data were available for 54 896 anesthetics in children 6 years and younger. There were 898 anesthesia reports available that included blood pressure measures immediately before induction. A larger number of anesthesia records (n = 30 008) were available for intraoperative blood pressure recording. The BP decrease after anesthesia induction was most pronounced in infants 0-10 weeks of age where there was a mean arterial blood pressure (MAP) decrease of 16.6-34.5% (mean 28.6%). Systolic blood pressure decreased by 16.3-32.6% (mean 25.5%). Values above a systolic blood pressure of 60 mm Hg were only noted in half the neonates during anesthesia. Heart rates, both before and after anesthesia induction, were similar.

CONCLUSION

Heart rate while under anesthesia appears a poor indicator for blood pressure changes. Recorded blood pressures in this current study, measured immediately before induction, were consistent with those in the literature. A mean MAP decrease of 28.6% was typical in those infants 0-10 weeks of age.

Clinical pharmacology of analgosedatives in neonates: ways to improve their safe and effective use

OBJECTIVES

To propose approaches tailored to the specific needs of neonates, such as structured product development programmes, with the ultimate goal to improve the safe and effective use of analgosedatives in these fragile patients.

KEY FINDINGS

The feasibility and relevance of a structured product development programme in neonates (optimal study design based on preliminary data; model development; internal, external and prospective evaluation; an individualized dosing regimen; long-term safety; pharmacogenetics) are illustrated for the use of morphine. Based on changes in clinical practices, similar development plans are in progress for short-acting analgosedatives such as propofol, but are in need of tailored pharmacodynamic tools to assess and quantify effects. Furthermore, for drugs like paracetamol where there is already sufficient clinical pharmacology knowledge, attention needs to be given to long-term safety aspects. Finally, new covariates such as pharmacogenetics might further improve neonatal pain management, but clearly need to be integrated with other well-established covariates like age or weight.

SUMMARY

Product development programmes for analgosedatives in neonates are needed. These programmes should be tailored to their specific needs (short-acting sedation, pain relief), should include long-term safety and should incorporate the exploration of newer covariates like pharmacogenetics.

Pharmacology in the very young: anaesthetic implications

Anaesthesia dosing in infants (0-2 years) should be based on pharmacokinetic-pharmacodynamic considerations and adverse effects profiles. Disease processes and treatments in this group are distinct from those in adults. Absorption, distribution and clearance change dramatically during this period because of maturation of anatomical and physiological processes as well as behavioural changes. Pharmacogenomic expression also matures in this period. Population-based and physiological-based pharmacokinetic modelling has improved the understanding of maturation and subsequent dose approximation. Postmenstrual, rather than postnatal, age is a reasonable measure for maturation. There remains a need for clinically applicable tools to assess pharmacodynamics which can provide response feedback; this has been achieved for neuromuscular monitoring, but not yet fully for depth of anaesthesia, sedation or pain. Morbidity and mortality associated with paediatric anaesthesia have historically been highest in this age group and continue to be so. Some of this morbidity was attributable to a poor understanding of developmental pharmacology; this facet continues to plague the specialty.

My child is unique; the pharmacokinetics are universal

The pharmacokinetic (PK) parameters that are important for dosing (e.g., clearance and volume) are well known. They are used in universal mathematical formulae that describe the time course of drug concentration. Additional formulae can be used to describe major covariate effects in children, such as size and maturation. PK parameters describing the time-concentration profile of a drug after administration are those for a typical individual in a population. These parameters are associated with variability. Further, any one individual may not be typical of the population studied. While size and maturation are two important considerations in children and assist with dosing estimation, there are also a number of additional PK covariates (e.g., organ function, disease, drug interactions, pharmacogenetics), and identifying these sources of variability allows us to individualize drug dose. Pharmacology is not simply an application of PK, and determinants of drug dose also require an understanding of the variability associated with pharmacodynamic response and a balancing of beneficial effects against unwanted effects. Each child is unique in this respect.