Literature Reviews
An Open Label Pilot Study of a Dexmedetomidine-Remifentanil-Caudal Anesthetic for Infant Lower Abdominal/Lower Extremity Surgery: The T REX pilot study
Szumk P, Dandopoulos D, McGowan F, et al. Pediatric Anesthesia 2019;160(1):59-67
Concern about potential neurotoxicity of anesthetics in infants has increased interests in finding other possibly less toxic management solutions. Dexmedetomidine is perceived as having a more advantageous profile but addition of other anesthetics may be required for surgical depth of anesthesia. This study examined the feasibility of a combination of dexmedetomidine with remifentanil and a caudal epidural block in surgery in infants lasting more than two hours.
Methods
An international open label pilot study involving seven centers enrolled 60 infants (age 1-12 months, ASA I-II, 53 male) undergoing lower extremity/lower abdominal surgery projected to last > two hours. After a brief induction with sevoflurane anesthesia was maintained with dexmedetomidine and remifentail infusions. Caudal block (bupivacaine 0.175-0.25% or ropivacaine 0.2%) was performed via inserted and secured (to allow redosing) 22g Angiocath. Safety review of protocol after each of the first two sets of 20 children (group 1-3) led to increases in anesthetic doses (final range: dexmedetomidine loading dose 1 mcg/kg/10 min and infusion 1-1.5 mcg/kg/h; remifentanil loading dose 1 mcg/kg/1-2 min and infusion 0.2-0.5 mcg/kg/min). Primary outcome measure was need of abandonment of protocol. Secondary ones were need for intervention for signs of light anesthesia (hypertension, movement), rescue treatment for bradycardia or hypotension, time to recovery after anesthesia, and postoperative analgesic requirements.
Results
All patients except four (consent withdrawal, protocol violation, failures of caudal placement) completed the protocol. Rescue treatment for hypertension and/or movement was required in 80% of cases. Hypertension alone was seen in 36% of infants. Signs of light anesthesia were observed in all 3 groups. Hypotension occurred in 14/56 (25%) of patients, primarily in group 3, lasting up to 10% of total anesthesia time. Bradycardia was observed in 8/56 patients. Postoperative analgesia was required in 7/56 patients. The epidural was re-dosed in 72% of the infants. Almost all patients received neuromuscular blocking agents.
Conclusion
Satisfactory anesthesia with dexmedetomidine/remifentanil could be achieved in 88% of children with a functioning caudal epidural catheter in place. Optimal doses of dexmedetomidine and remifentail for these types of surgeries need to be further defined. (Comment: The high incidence of movement is interesting considering the use of caudal epidurals and neuromuscular blockers. The authors did not provide information regarding definition of movement, volume of caudal injectate or time to epidural re-dosing).
