Annual Scientific Meeting - 2001

Target-controlled infusion of propofol for induction and maintenance of anaesthesia in children using the Paedfusor

Daphne A Varveris, FRCA and Neil S Morton  FRCA, FRCPCH. Department of Anaesthesia, Royal Hospital for Sick Children, Glasgow, UK

Introduction The aim of this open pilot study was to evaluate the ease of use, safety and efficacy of the Paedfusor, a computer controlled propofol infusion device with software appropriate for children down to age 6 months / 5kg weight. Children tend to have a rapid clearance of intravenous agents (1) and a proportionately larger central compartment volume than adults.  The Paedfusor uses an algorithm previously validated for bias and precision in a paediatric cardiac setting. (2).

Methods Thirty ASA 1 children aged 6 months to 16 years scheduled for elective surgery were included in the study. Vital signs were recorded at 1 minute intervals during induction and every 3 minutes thereafter.  Patients breathed spontaneously through a laryngeal mask airway (LMA) and  perioperative analgesia was provided by a regional block.  Target plasma and calculated effector site propofol readings were recorded on insertion of LMA, insertion of regional block, surgical incision and removal of LMA.

Results A plasma target level of 8mcg/ml universally induced sleep within 1 minute.  Spontaneous respiration was maintained in the majority although four patients had short periods of self-limiting apnea. There were no cases of laryngospasm. Patient data and calculated mean effector site concentrations at different intervention points are presented in Table 1. 57% moved on insertion of block and 30% responded to surgical stimulation. Mean heart rates increased slightly after each stimulus returning thereafter to baseline values. Blood pressure remained stable throughout.  No relationship between infusion duration, total propofol requirements and time to patient awakening was found.  The average total propofol dose was high, being highest in the youngest groups.

Table 1: - Details of patients and results for each group. Mean (SD), MESC = mean effector site concentration

Conclusions: This open study confirms the safety and ease of use of the Paedfusor for the induction and maintenance of anaesthesia in healthy children over 6 months undergoing elective surgery. Further studies assessing the accuracy of the infusion algorithm in this patient group are required.

References:

1. Marsh BJ, White M, Morton NS et al. Pharmokinetic model driven infusion of propofol in children. Br JAnaesth 1991; 67: 41-48

2. D.Amutike, A Lal, A Absolom and G.N.Kenny. Accuracy of the Paedifusor-a new propofol target-controlled infusion system for children. Br J Anaesth 2001;Vol 87;175P – 176P