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October 22, 2008
9:00 AM - 11:00 AM
Room Hall E2-Area E,
PCA Properties Predictive of Acute Opioid Tolerance in the Pediatric Postsurgical Population
Conor Mc Donnell, M.D., F.F.A.R.S.C.I., Carolyne Pehora, R.N., Rebecca Hull, M.B., Christian Zaarour, M.D., Mark Crawford, M.B.
Anesthesia, Hospital for Sick Children, Toronto, Ontario, Canada
Introduction: Acute tolerance to opioids develops when potent opioid agents such as remifentanil are delivered by infusion. In scoliosis repair, high dose, prolonged remifentanil infusion can lead to the development of acute opioid tolerance in the post-operative period. A clinical observation at 24 hours post scoliosis repair is that some patients demonstrate significant analgesia requirements above and beyond that provided by PCA morphine. We hypothesized that such patients may be identifiable earlier in the postoperative period.

Methodology: We preformed a retrospective review of the datasheets of 37 pediatric patients who had undergone elective scoliosis repair.

Results: Patients were divided into two groups. One group received morphine (0.1 mg/kg) by bolus pre-initiation of remifentanil infusion, the other group received saline bolus instead. No other demographic differences between the two groups were present -[table1]Seven patients required alteration of treatment from PCA morphine to hydromorphone. All 7 patients were from the same group (morphine bolus). All 7 patients complained of severe pain and pruritus, however their pain scores were not significantly different from other patients reviewed. All 7 patients had PCA changed from morphine to hydromorphone at 20-24 hrs postop. We examined the ratio of PCA demands to deliveries for each post-operative time period to investigate PCA use and its efficacy. Figure1 demonstrates that for all 7 'hydromorphone' patients, there is an observable difference in PCA ratios from postop hour 8 to hour 24. This difference is first significant at the 8 hour timepoint (*P<0.001) -.[figure1]Conclusions: This retrospective review is not powered to significantly confirm our findings but there are two important issues that warrant further investigation. (1)Administration of morphine by bolus prior to administering remifentanil infusion for pediatric scoliosis surgery may be associated with increased postoperative pain. (2) If further prospective study demonstrates that the ratio of PCA demands to deliveries is indeed predictive of patients with additional analgesia requirements this would significantly impact quality of patient care. We could better and earlier identify significant postop pain. It will also improve patient safety as it would decrease the amount of rescue medications requested in the postoperative period therefore decreasing the risk of adverse medication events.

Anesthesiology 2008; 109 A1706
Table 1: Patient Characteristics and Intraoperative Outcomes
Morphine (n =18 )Saline (n =19 )
Age (yr)14.8 ± 1.714.5 ± 1.9
Weight (kg)54.2 ± 8.851.3 ± 8.4
Male: Female4:143:16
Thoracic Cobb angle (degrees)63 (45-74)62 (41-81)
Length of Instrumentation (vertebral levels)10 (8-14)10 (7-12)
Anesthesia Duration (min)415 ± 83391 ± 97
Propofol infusion rate (μ ± 18126 ± 16
Remifentanil infusion rate (μ ± 0.100.30 ± 0.06
Values are mean ± SD, ratio, or median (range). Patient demographics and extent of surgery were comparable in the two groups
Figure 1