Timing of Aminophylline and Recovery in Pediatric Ambulatory Surgery

An online randomization program (http://www. Randomizer.org) will be used to generate a random list and each patient's code will be kept in an opaque sealed envelope. Patients will be randomly allocated with 1:1:1 allocation ratio into three equal groups in a parallel manner:

• Group E (n=20): patients will receive aminophylline at an early intraoperative time immediately after fixation of ETT and confirmation of bilateral adequate lung ventilation (EtSevo< 1).
• Group L (n=20): patients will receive aminophylline at late intraoperative time immediately after discontinuation of sevoflurane (EtSevo < 1).
• Group (C) (n=20): patients will receive normal saline immediately after discontinuation of sevoflurane (EtSevo < 1). Patients and outcome assessors will be blinded to the group of the patients. An independant anesthetist who is not involved in the study will prepare the interventional medications.

Preoxygenation with 100% oxygen will be done for 3 min. An intravenous cannula will be inserted after inhalational induction of sevoflurane at 8%. Then, General anesthesia will be induced by propofol (2.0 mg/kg), fentanyl (1.0 mcg/kg) and atracurium (0.5 mg/kg) endotracheal intubation will be performed after full relaxation.

Anesthesia will be maintained with sevoflurane (2.0%-3.0%) to keep EtSevo 2.0 % in an O2/air mixture, and top up doses of atracurium every 30 min. Fresh gas flow will be set at 3 L/min all through the intraoperative period. Minute ventilation will be adjusted to maintain normocapnia (end tidal carbon dioxide; et CO2, between 32- and 34-mm Hg application of 5.0 mmHg of PEEP).

Two syringes will be prepared by an independent anesthesiologist for each patient. One syringe contains 5.0 mg/kg aminophylline while the other syringe contains a similar volume of normal saline. Then according to the allocated group, the independent anesthesiologist injected the syringe in an appropriate time and rate (over 10 min). All patients will receive Lactated Ringer's solution infused at a rate of 2.0-3.0 mL/kg/h and dexamethasone at 0.15 mg/Kg as antiemetic. Normothermia will be maintained by warming the IV fluids and using Bair Hugger warming system.

In case of tachycardia (20% increase in the heart rate from the baseline reading) or hypertension (20% increase in the mean arterial pressure from the baseline reading), the depth of anesthesia will be increased by increasing the concentration of sevoflurane and administration of IV fentanyl at 1μg/Kg. In case of hypotension (20% decrease in the mean arterial pressure from the baseline reading); if fluid boluses failed to restore blood pressure back to normal the concentration of the sevoflurane will be reduced, and ephedrine will be administered in 5.0 mg/kg increments.

In the post-anesthesia care unit (PACU), the patient will be assessed immediately after admission and every 5 min using the Pediatric Post-Anesthetic Discharge Scoring System (Ped-PADSS) until it reaches at least 9 points; then the patient will be ready to discharge home. All patients will be given 0.5 mg/Kg I.V. boluses of pethidine if pain score ( Wong-baker faces pain scale) > 4. Ramsay sedation scale will be recorded to distinguish 3 levels of sedation, where 0 means no sedation, 2-3 means conscious sedation, and 4-6 means deep sedation. Emergence delirium (ED) will be suspected if the child had a non-purposeful movement, seemed disorientated or confused, failed to interact normally with parents or caregiver or pulling IV lines, wound dressings or monitors. The Watcha scale will be used to assess postoperative emergence delirium (ED) in the recovery room. Diagnosis of ED will be considered if the child had a score of >2 on the Watcha score.

Measurement tools:

• Demographic data (age, sex, weight), ASA physical status (I or II), type and duration of surgery (from skin incision utill completion of last stitch) and duration of anaesthesia (from iv induction utill sevoflurane discontinuation).
• Heart rate (HR) and mean arterial blood pressure (MBP) will monitored continuously and recorded at the following intervals: T0= immediately before I.V. induction of GA, T1= immediately after fixation of ETT (corresponding to the start time of drug administration in group E), T3= 15 min after fixation of ETT, T4= immediately before sevoflurane discontinuation, T5= 5 min after discontinuation of sevoflurane (corresponding to the ending time of drug administration in groups L and C, T6= 5 min after extubation, T7= 10 min after transfer to PACU.
• Ramsay sedation scale will be recorded 5 min after extubation, on admission to the PACU, and when the Pediatric Post-Anesthetic Discharge Scoring System (Ped-PADSS) >9.
• Watcha scale to diagnose ED will be assessed 5min after PACU admission. ED will be considered if the child had a score of >2 after being suspected clinically and before giving the rescue analgesics.
• Pediatric Post-Anesthetic Discharge Scoring System (Ped-PADSS) will be assessed and recorded immediately after PACU admission and every 5 min until it reached at least 9 points. Recovery of consciousness (ROC) time: defined as the time interval in minutes from discontinuation of sevoflurane anesthetic to eye opening in response to verbal or tactile command (extubation criteria).
• Home readiness discharge time: which is the time in minutes taken to home discharge decision; started from admission to PACU utill Ped PADSS reached at least 9.
• Total recovery time: which is the time in minutes started from discontinuation of sevoflurane anesthesia utill Ped-PADSS reached at least 9. Outcomes

Primary outcome:

• Recovery of consciousness (ROC) time was defined as the time interval in minutes from discontinuation of anesthetics to eye opening in response to verbal command or tactile stimulation.

Secondary outcome:

• Home readiness discharge time: which is the time in minutes taken to home discharge decision; started from admission to PACU utill Ped PADSS reached at least 9.
• Total recovery time: which is the time in minutes started from discontinuation of sevoflurane anesthesia utill Ped-PADSS reached at least 9.
• Level of sedation as assessed by Ramsay sedation scale 5 min after extubation, on admission to the PACU, and when the Pediatric Post Anesthetic Discharge Scoring System (Ped-PADSS).
• Incidence of ED as assessed by Watcha scale 5 min after PACU admission. Adverse events after aminophylline administration (e.g., arrhythmia, hypotension or hypertension, tremors, seizures, vomiting, shivering, agitation, rhabdomyolysis).

Ethical consideration:

Informed consent will be obtained from all parents involved in the study. There were adequate provisions to maintain the privacy of participants and confidentiality of the data.

Sample size calculation:

The sample size calculation was performed using G.power 3.1.9.2 (Universitat Kiel, Germany). The sample size was calculated based on the following considerations: 0.05 α error and 95% power of the study to demonstrate a 10% decrease in ROC (the primary outcome) with group E than group L (mean 4.53 min and SD 3.33 min, the mean was 8.93 min and SD was 0.92 min in group C according to a previous study). Two cases were added to each group to overcome dropout. Therefore, 20 patients were allocated in each group. Statistical analysis Statistical analysis will be done by SPSS v27 (IBM©, Chicago, IL, USA). The Shapiro-Wilks test and histograms will be used to evaluate the normality of the distribution of data. Quantitative parametric data will be presented as mean and standard deviation (SD) and will be analyzed by ANOVA (F) test with post hoc test (Tukey). Quantitative non-parametric data will be presented as median and interquartile range (IQR) and will be analyzed by Kruskal-Wallis test with Mann Whitney-test to compare each group. Qualitative variables will be presented as frequency and percentage and will be analyzed utilizing the Chi-square test. A two tailed P value < 0.05 will be considered statistically significant.