Total intravenous anesthesia(TIVA) is a commonly used anesthetic technique. Although TIVA can be accomplished with a variety of drug combinations, infusions of Propofol and Remifentanil are often used with dosage adjusted manually by the anesthesia provider.The pharmacokinetics of these drugs are well understood, and that knowledge has led to the development of computer controlled infusion pumps that can administer the drugs based upon pharmacokinetic models. Computer controlled infusion schemes automatically adjust the drug administration based upon pharmacokinetic models which typically dictate a tapering infusion scheme. When one considers the dosage of a computer controlled infusion it is obvious that manually imitating a similar scheme may be difficult.This study will evaluate manually controlled infusion schemes using the models built into the Applied Medical Visualizations (Medvis) display and compare the manual dosage schemes to the predicted effect site concentrations and pharmacodynamic effect.

During Total intravenous anesthesia (TIVA), the anesthetic propofol and the opioid remifentanil are often used together. Previous studies have demonstrated the synergy between these combinations of medications. From these data, drug interaction models have been developed to pair drug effect-site concentrations with event markers of interest to the clinical anesthesiologist. For example, the amount of remifentanil and propofol typically required during the induction of anesthesia to cause loss of responsiveness to verbal or moderate stimuli has been studied. Likewise, the blood concentration levels present during emergence from anesthesia have been explored describing levels typically present for patients to return to consciousness.

The purpose of this study is to retrospectively analyze the infusion doses of both remifentanil and propofol for pediatric patients undergoing spinal fusion surgery at CHOP. These data will be applied to the pharmacokinetic models to determine the predicted effect site concentration, and the relationship of that concentration to the 50% and 95% doses as predicted by the model.

Inclusion Criteria:

1. Male and Female patients age 0 to 18 years old
2. Spinal surgery at CHOP between 4/1/07 and 3/31/08
3. Complete CompuRecord Anesthesia documentation
4. Use of Propofol and Remifentanil infusions as primary anesthetic technique

Exclusion Criteria:

1. Chronic opioid or benzodiazepine medication use prior to surgery
2. Use of other anesthetic infusions (i.e. Ketamine/Fentanyl) during TIVA
3. Use of Neuraxial opioids
4. Use of other Induction medications (i.e. Sodium Thiopental)

Pediatric patients having spinal surgery procedures completed at CHOP from April 2007 through March 2008