During recent years there has been an increased awareness of the need for adequate sedation and analgesia of critically ill pediatric patients. The choices of the treatment of pain are numerous, but in the Pediatric ICU parenteral opioids are most commonly used. At equipotent doses, all mu agonist opioids (Morphine, Fentanyl, Meperidine and Codeine) produce similar physiologic effects and side effects. Opioids can cause hypoventilation, hypotension, constipation and cause urinary retention. Patients receiving continuous opioid infusions experience not only these physiologic side effects, but also the side effects of dependence, tolerance and withdrawal. These last side effects complicate medical issues and contribute to longer ICU admissions.