Pediatric Anesthesia ISSN 1155-5645
Chloral hydrate sedation for magnetic resonance imaging in newborn infants Anna Finnemore, Hilary Toulmin, Naz Merchant, Tom Arichi, Nora Tusor, David Cox, Ash Ederies, Phumza Nongena, Christopher Ko, Ryan Dias, Anthony D. Edwards & Alan M. Groves Centre for the Developing Brain, Imperial College London and MRC Clinical Sciences Centre, London, UK
Keywords infant, newborn; chloral hydrate; magnetic resonance imaging; adverse effects; patient monitoring; patient safety Correspondence Alan Groves, Centre for the Developing Brain, Imperial College London and MRC Clinical Sciences Centre, Hammersmith Hospital Du Cane Road, London W12 0NN, UK Email: [email protected]
Section Editor: Charles Cote Accepted 18 August 2013 doi:10.1111/pan.12264
Summary Background: The aim of this study was to look for clinically significant adverse effects of chloral hydrate used in a large cohort of infants sedated for magnetic resonance imaging. Method: Case notes of infants who underwent magnetic resonance imaging (MRI) scanning from 2008 to 2010 were reviewed, with patient demographics, sedation dose, comorbidities, time to discharge, and side effects of sedation noted. Results: Four hundred and eleven infants (median [range] postmenstrual age per weight at scan 42 [31+4–60] weeks per 3500 g [1060–9900 g]) were sedated with chloral hydrate (median [range] dose 50 [20–80] mgkg 1). In three cases (0.7%), desaturations occurred which prompted termination of the scan. One infant (0.2%) was admitted for additional observation following sedation but had no prolonged effects. In 17 (3.1%) cases, infants had desaturations which were self-limiting or responded to additional inspired oxygen such that scanning was allowed to continue. Conclusion: When adhering to strict protocols, MRI scanning in newborn infants in this cohort was performed using chloral hydrate sedation with a relatively low risk of significant adverse effects.
Introduction Magnetic resonance imaging (MRI) scanning in term and preterm infants is providing vital new insights into neurological development and pathology. Sedative medications are commonly used for scanning in the newborn population to decrease image artifact due to motion without the need for artificial ventilation (1). The UK National Institute for Clinical Excellence (NICE) recommends the use of oral chloral hydrate in children under 15 kg (2), yet some studies have shown that chloral hydrate can cause an increase in episodes of bradycardia, apnea, and reduced oxygen saturation (3). These complications have been postulated to be more frequent in infants with lower birthweights (4). We have a 3.0 Tesla MRI scanner situated within our neonatal intensive care unit, allowing us to perform scans on extremely preterm and sick term infants. As a 190
tertiary neonatal unit taking clinical referrals for brain imaging from across our region, and with an active research program, we perform approximately 500 MRI scans in infants per year. While many scans, particularly in preterm infants, are performed without any sedation using a feed and wrap technique (5), sedation may be necessary in older infants when feed and wrap techniques may be less effective. Chloral hydrate is routinely used for this purpose in infants above 33 weeks postmenstrual age (PMA) with no clinical contraindications. As approximately one-third of our patients receive chloral hydrate sedation for MRI scanning, the aim of this study was to audit the occurrence of recognized side effects from chloral hydrate sedation to ensure best practice. Our hypothesis is that using a dose of 30–50 mgkg 1 of chloral hydrate allows adequate sedation for MRI scanning without the need for intubation and ventilation, and without significant adverse effects. © 2013 John Wiley & Sons Ltd Pediatric Anesthesia 24 (2014) 190–195
A. Finnemore et al.
Methods Ethical approval has been obtained from the Hammersmith and Queen Charlotte’s and Chelsea Research Ethics Committee for all our MRI research projects, and signed parental consent for both research and sedation was obtained in all cases. MRI scans are performed by specially trained medical and nursing staff, following strict protocols for subject preparation, monitoring, and support (see Supporting Information). In all cases, the infants’ vital signs are continually displayed by remote patient monitoring, and values are recorded every 5 min on printed proformas (see Supporting Information). Our protocols are consistent with UK NICE guidelines for sedation in young children (2). We tested our hypothesis by carrying out a retrospective cohort study of all infants sedated for clinical or research MRI scanning at our institution between January 2008 and December 2010. Case notes and MRI observation sheets were retrospectively reviewed by members of the research team for birth and current weight and age, dose, and timing of sedation given, scan timings, comorbidities, and possible adverse effects of sedation including cough, increased oxygen requirements, bradycardias (heart rate 20 s). Brief, self-correcting desaturations and bradycardias were not considered adverse events in our infant cohort because they are a relatively common occurrence in brain injured, preterm, and even term infants (6). The length of time required for infants to become fully awake, alert and feeding, and time to discharge was also recorded. In a subgroup of infants, parents were contacted by telephone on the next working day after MR scanning. Parents were asked about any history of infant drowsiness, difficulty feeding, or requirement to seek medical care in the 24 h after sedation with chloral hydrate. Confidence levels for parametric data are given as twice the standard deviation from the mean. Comparison of continuous nonparametric data was performed with the Mann–Whitney–Wilcoxon test and nominal data with Fischer’s exact test. Scanning methods Infants undergoing sedation for MRI are cared for throughout the process by a specially trained pediatrician or pediatric nurse. They are scanned either as inpatients on the neonatal unit or attend a specialist pediatric ambulatory care unit. They are examined by a pediatrician and certified fit for scan (e.g., free of © 2013 John Wiley & Sons Ltd Pediatric Anesthesia 24 (2014) 190–195
Chloral hydrate sedation for MRI
intercurrent infection, no history of snoring/stridor/airway compromise, etc. – see Supporting Information), then kept nil by mouth for at least an hour prior to sedation. We feel this is appropriate given the level of sedation targeted and that more prolonged periods of fasting are not appropriate in neonates who are often feeding at 2–3 hourly intervals. Oral chloral hydrate is given as a single agent at an initial dose of 30–50 mgkg 1 as per our unit protocols, a relatively low dose compared with that reported elsewhere (7,8). Precise dosage is at the clinician’s discretion within these limits, with suggested doses of 30 mgkg 1 for preterm infants and 50 mgkg 1 for term infants. Re-dosing is permitted if required to a maximum dose of 80 mgkg 1. Oxygen saturation is monitored continuously from time of sedation to time of full waking. Infants are scanned with double layered hearing protection on a 3.0 Tesla Philips Achieva MR scanner (Best, the Netherlands). Throughout the scan process, oxygen saturation is targeted at our neonatal unit protocols, and recordings of heart rate, oxygen saturation, and temperature are noted every 5 min on a specially designed observation sheet. Infants are returned to the ward or ambulatory unit following scanning where observation, including continuous oxygen saturation monitoring, is continued by nursing staff. Infants can be discharged once the responsible nurse feels they are fully awake and feeding. We do not use minimum or maximum times to discharge. Parents who are discharged home are given information regarding side effects, the importance of observation in car seats, and contact numbers for any concerns. Results The case notes of 411 babies were examined. Median (range) gestational age and weight at birth were 37 (23+2–43+4) weeks and 2580 (610–5490) g. Corrected age and weight at scan were 42 (31+4–60) weeks and 3600 (1060–9900 g) grams. Two hundred and six infants were ex-preterm (born at