Wound catheter infusion after abdominal surgery in baby's.

The mean cumulative amount of morphine administered over 48 hours postoperatively, in mcg/kg, will be compared in both groups (R group and control group).

Secondary Objectives:
1. Efficacy of treatment of postoperative pain: To determine if WCI with ropivacaine provides adequate treatment of postoperative pain, COMFORT behaviour scale and NRS Pain are measured, and these pain assessments are used to administer rescue morphine doses IV.
Parameters:
• Number of patients needing extra morphine boluses (rescue), over 48 hours.
• Total amount of morphine administered postoperatively, until removal of the wound catheter.
• AUC 24 hours COMFORT-B score and NRS, and percentage of high pain scores (NRS ≥ 4 and COMFORT ≥ 17).
2. Safety of the use of WCI with ropivacaine: To investigate if WCI with local anesthetics is safe for the treatment of postoperative pain in children, the incidence of adverse events related to the wound catheter and the use of ropivacaine is registered
Parameters:
• Toxicity due to overdose or inadvertent intravascular injection of local anesthetic: 
- hypotension
- arrhythmia
- convulsions
• The incidence of adverse effects related to the wound catheter: 
- accidental luxation of the wound catheter
- infection (wound infection, sepsis)
- hematoma of the wound
- delayed healing of the wound
- wound dehiscence
• Plasma concentrations of ropivacaine (total and unbound) will be measured during the phase of continuous infusion in the wound, to determine if plasma levels do not exceed toxic thresholds.
3. Adverse events related to the use of opioids:
• Signs of respiratory depression: 
- number of apnea episodes
- number of intubated and ventilated patients in each group, when arriving on the PICU
- time on the ventilator postoperatively
- number of reintubated patients during the study period
- number of patients receiving naloxone
- time until discharge from the PICU
• Gastro-intestinal: 
- signs of intestinal obstruction and nausea and vomiting
- time to first feeding
• Hemodynamic: 
- hypotension with the need for vaso- active medication or fluid boluses
- bradycardia (other than due to or directly related to the disease or operation)
4. Other variables:
• Surgical stress: 
To classify the surgical stress of the different procedures, the Surgical Stress Score is computed by the surgeon at the end of surgery: the amount of blood loss (score range 0-3); site of surgery (score range 0-2); amount of superficial trauma (score range 1-3); extent of visceral trauma (score range 1-4); duration of surgery (score range 1-5); associated stress factors: hypothermia (score range 0-3) and infection (score range 0-3). The total scores are used to divide the procedures in minor, moderate or severe surgical stress.
• The Parents’ Postoperative Pain Measure- Short Form: One week after the operation, the parents are contacted to fill out a questionnaire: the PPPM-SF, a validated questionnaire, which shows the postoperative recovery of a child after discharge from the hospital.