The aim of this study is to compare AMG and EMG (Philips IntelliVue NMT module and Senzime TetraGraph) in the objective monitoring of neuromuscular blocking in children between the age of 6 months and 2 years.The monitoring will be done bilaterally either on n.ulnaris or n. tibialis. The hypothesis of the study is that AMG will indicate faster recovery time (time to return to TOF 90%) from neuromuscular block than EMG.

Objective neuromuscular monitoring is strongly recommended when administering neuromuscular blocking agents (NMBA). However, objective neuromuscular monitoring may be challenging, especially in smaller children due to the limited size of their extremities which often are not easily accessible due to issues such as sterile draping and surgical equipment. Consequently, paediatric anaesthesia care providers often experience problems with neuromuscular monitoring.

NMBAs improve intubating conditions and prevent airway injury in children and infants (<12 months of age). However, both patient age and type of anaesthesia influence onset and duration of action. Infants have shorter onset time of NMBAs compared to older children, and a higher proportion of infants had excellent intubating conditions compared to older children at two minutes after a dose of 0.15 mg/kg cisatracurium. Inhalation anaesthetics prolong recovery from cisatracurium compared to total intravenous anaesthesia and a longer duration of action is seen in infants compared to older children. However, as compared to adults, less profound neuromuscular blockade may be sufficient in children to establish satisfactory intubating conditions.

In children < 3 years old, a study reported residual neuromuscular blockade (TOF (Train Of Four) ratio < 0.9) among 8% of the included patients after administration of a single bolus of 0.1 mg/kg cisatracurium, but the actual proportion may have been as high as 20%. To prevent residual neuromuscular block, objective neuromuscular monitoring is recommended. In adults residual neuromuscular block may result in respiratory events (hypoxaemia and airway obstruction), unpleasant symptoms of muscle weakness, prolonged post-anaesthesia care unit stay, and an increased risk of postoperative pulmonary complications.

It is possible to monitor onset time and duration of action of NMBAs with electromyography (EMG) or acceleromyography (AMG) by train-of-four (TOF) stimulation of a peripheral nerve. Typically, the ulnar nerve is stimulated. In smaller children the tibial nerve can be used as an alternative. However, a recent study in adults reports that there may be important differences when comparing EMG and AMG TOF monitoring at the ulnar nerve with EMG detecting recovery of neuromuscular function later than AMG. Only one study in infants has reported that monitoring of neuromuscular function with AMG applied on the first toe may be a suitable alternative when the thumb is inaccessible. One recent study has reported the feasibility of monitoring the depth of neuromuscular block in infants using electromyography. No study has to our knowledge compared AMG to EMG in infants and small children.

The investigators hypothesize that AMG will indicate faster recovery (time to return to TOF 90%) from neuromuscular block than EMG A secondary aim of this study is to investigate agreement between the two monitors using a Bland Altman analysis comparing onset time and recovery from deep to moderate rocuronium-induced neuromuscular block with EMG and AMG.

Inclusion Criteria:

• Patients 6 months - 2 years of age
• Scheduled for elective surgery under general anaesthesia with intubation and use of rocuronium
• American Society of Anesthesiologists (ASA) physical status classification I to III

Exclusion Criteria:

• Known allergy to rocuronium
• Neuromuscular disease that may interfere with neuromuscular data
• Indication for rapid sequence induction
• Prone position