Introduction Safe and effective sedation and analgesia in children’s critical care is a complex area of medicines use. Analgesia and sedation are needed to treat any pain during a critical care stay, and also to facilitate the delivery of invasive interventions such as mechanical ventilation and intravenous access devices.

Strong opioids are a group of medicines often used to achieve good sedation and pain relief. In adult critical care, alfentanyl has become the opioid of choice as it reduces the length of stay.^{1 2} This could be attributed to the pharmacokinetic profile of alfentanyl. Alfentanyl does not distribute widely into body tissue like fentanyl, and is not dependent on kidney function to be removed from the body like morphine or oxycodone.³ Most children’s critical care units in the UK use either morphine or fentanyl.⁴ The aim of this case report is to describe the use of alfentanil in a complex patient and assess the outcome.

Situation The patient was a 2-month-old (weight = 2.6kg) who had a truncus arteriosus repair at nine weeks of age. The initial postoperative course was complicated by high pulmonary pressures and heart failure that required a further operation. Following this the patient had cardiovascular instability and needed four days of extracorporeal membrane oxygenation (ECMO) support. The clinical team felt that adequate sedation was essential to keeping the patient’s blood pressure under control, and to avoid exacerbating heart failure that may have required another period of ECMO support. Sedation had already been titrated using a fentanyl infusion at 7 microgram/kg/hour, clonidine infusion at 2 microgram/kg/hour and chloral hydrate rectal 200 mg/kg/day in divided doses. Midazolam is not used after cardiac surgery at this unit due to concerns about cardiovascular side effects. Unfortunately, the patient was not on enteral feeds and so sedation could not be given via this route. The patient had reduced urine output and the creatinine trend showed an acute kidney injury. The patient’s oxygen saturations dropped when they became agitated during routine cares and procedures. As fentanyl was not deemed to be working this was stopped and alfentanil started at 30 microgram/kg/hour. The dose was quickly escalated to the maximum recommended of 120 microgram/kg/hour. Unfortunately, little improvement was seen, and ultimately a ketamine infusion was started which proved to be effective. Eventually, enteral feeding was established, and the addition of promethazine helped sedation and the alfentanil was converted to morphine.

Lesson Learned This case showed that there was little benefit from substituting fentanyl for alfentanil in a complex patient during a prolonged hospital admission. If fentanyl is to demonstrate the benefits seen in adult critical care, then it should be studied during the early critical care period. There are many unanswered questions about sedation in children’s critical care. These include whether any medicines are more effective than others, how to escalate sedation in difficult to manage patients, and whether there is any benefit to cycling sedative agents.

References

1. Richards-Belle A, Canter R, Power G, et al. National survey and point prevalence study of sedation practice in UK critical care. Critical Care 2016;20:355.

2. Manley N, Fitzpatrick R, Long T, Jones P. A cost analysis of alfentanil + propofol vs morphine + midazolam for the sedation of critically ill patients. PharmacoEconomics 1997;12:247–255.

3. Piramal Critical Care Ltd. Rapifen – Summary of Product Characteristics. [Internet]. Surrey, UK; Electronic Medicines Compendium. [updated 5th November 2021]. Available from: https://www.medicines.org.uk/emc/product/9776/smpc [Accessed 17th June 2022]

4. Jenkins I, Playfor S, Bevan C, Davies G, Wolf A. Current United Kingdom sedation practice in pediatric intensive care. Paediatric Anaesthesia 2007;17:675–683.