Prospective Association of Serum Opioid Levels and Clinical Outcomes in Patients With Cancer Pain Treated With Intrathecal Opioid Therapy.

BACKGROUND: Opioids remain the mainstay of cancer pain management but are associated with systemic toxicity. In refractory cancer pain, intrathecal therapy (ITT) is associated with improved pain control, reduced systemic side effects, and improved survival. It has been assumed that ITT decreases systemic serum opioid levels and their associated toxicity, but there are limited data to support this assumption. This study hypothesizes that serum opioid levels decrease with ITT. Secondary objectives include comparative measures of pain, bowel function, and other cancer-related symptoms. METHODS: Fifty-one cancer patients undergoing ITT for cancer pain were recruited in a prospective observational study. Daily oral morphine equivalency (OME) dose, serum opioid levels, Brief Pain Inventory (BPI), MD Anderson Symptom Inventory (MDASI), and a constipation questionnaire were obtained at the time of implant, and 4 and 8 weeks postoperatively. RESULTS: Average baseline daily OME was 375 mg (median, 240; interquartile range, 150-405; range, 0-3160), mean serum morphine concentration was 53.7 ng/mL (n = 17), and mean oxycodone concentration was 73.7 ng/mL (n = 20). At 4 weeks, 87.5% of patients had discontinued non-IT opioids, and 53% had undetectable (<2 ng/mL) serum opioid concentrations. At 8 weeks, 92% remained off all non-IT opioids and 59% had undetectable serum opioid levels. IT morphine doses >4.2 mg/d were invariably associated with detectable serum levels; with doses <4.2 mg, morphine was undetectable in 80% of subjects. IT hydromorphone doses >6.8 mg/d were detectable in the serum. Using linear mixed model analyses, there were statistically significant decreases in the mean "worst pain," "average pain," and MD Anderson symptom severity and interference scores at 4 and 8 weeks. This change was independent of serum opioid levels; when analyzed separately, there was no difference in the pain scores of subjects with detectable serum opioid levels compared to those with undetectable levels at 4 and 8 weeks. Constipation ranked as "quite a bit" or "very much" decreased from 58.7% to 19.2% of subjects at week 4 (P < .001) and to 37.5% at 8 weeks (P = .23). A very low complication rate was observed. CONCLUSIONS: ITT for cancer pain was associated with a marked reduction in serum opioid concentrations, with the majority of patients having undetectable serum levels. Reducing serum opioid concentrations in cancer patients may have implications with respect to restoring bowel function, improving fatigue, and promoting the integrity of antitumor immune function and warrants further study.

High intraoperative inspired oxygen does not increase postoperative supplemental oxygen requirements.

BACKGROUND: Although a high fraction of inspired oxygen (FIO2) could reduce surgical site infection, there is concern it could increase postoperative pulmonary complications, including hypoxemia. Intraoperative positive end-expiratory pressure can improve postoperative pulmonary function. A practical measure of postoperative pulmonary function and the degree of hypoxemia is supplemental oxygen requirement. We performed a double-blind randomized 2 × 2 factorial study on the effects of intraoperative FIO2 0.3 versus more than 0.9 with and without positive end-expiratory pressure on the primary outcome of postoperative supplemental oxygen requirements in patients undergoing lower risk surgery. METHODS: After Institutional Review Board approval and consent, 100 subjects were randomized using computer-generated lists into four treatment groups (intraoperative FIO2 0.3 vs. more than 0.9, with and without 3-5 cm H2O positive end-expiratory pressure). Thirty minutes and 24 h after extubation, supplemental oxygen was discontinued. Arterial oxygen saturation by pulse oximetry was recorded 15 min later. If oxygen saturation decreased to less than 90%, supplemental oxygen was added incrementally to maintain saturation more than 90%. RESULTS: Nearly all subjects required supplemental oxygen in the postanesthesia care unit. Nonparametric Wilcoxon rank sum test demonstrated no statistically significant difference between groups in supplemental oxygen requirements at 45 min and 24 h after tracheal extubation (P = 0.56 and 0.98, respectively). CONCLUSIONS: Use of intraoperative FIO2 more than 0.9 was not associated with increased oxygen requirement, suggesting it does not induce postoperative hypoxemia beyond anesthetic induction and surgery. Therefore, it may be reasonable to use high inspired oxygen in surgical patients with relatively normal pulmonary function.