Cost-effectiveness of intravenous acetaminophen and ketorolac in adolescents undergoing idiopathic scoliosis surgery

Abstract

Background: Enhanced recovery after surgery protocols increasingly use multimodal analgesia after major surgeries with intravenous acetaminophen and ketorolac, despite no documented cost-effectiveness of these strategies.

Aims: The goal of this prospective cohort study was to model cost-effectiveness of adding acetaminophen or acetaminophen + ketorolac to opioids for postoperative outcomes in children having scoliosis surgery.

Methods: Of 106 postsurgical children, 36 received only opioids, 26 received intravenous acetaminophen, and 44 received acetaminophen + ketorolac as analgesia adjuncts. Costs were calculated in 2015 US $. Decision analytic model was constructed with Decision Maker^® software. Base-case and sensitivity analyses were performed with effectiveness defined as avoidance of opioid adverse effects.

Results: The groups were comparable demographically. Compared with opioids-only strategy, subjects in the intravenous acetaminophen + ketorolac strategy consumed less opioids (P = .002; difference in mean morphine consumption on postoperative days 1 and 2 was -0.44 mg/kg (95% CI -0.72 to -0.16); tolerated meals earlier (P < .001; RR 0.250 (0.112-0.556)) and had less constipation (P < .001; RR 0.226 (0.094-0.546)). Base-case analysis showed that of the 3 strategies, use of opioids alone is both most costly and least effective, opioids + intravenous acetaminophen is intermediate in both cost and effectiveness; and opioids + intravenous acetaminophen and ketorolac is the least expensive and most effective strategy. The addition of intravenous acetaminophen with or without ketorolac to an opioid-only strategy saves $510-$947 per patient undergoing spine surgery and decreases opioid side effects.

Conclusion: Intravenous acetaminophen with or without ketorolac reduced opioid consumption, opioid-related adverse effects, length of stay, and thereby cost of care following idiopathic scoliosis in adolescents compared with opioids-alone postoperative analgesia strategy.

Keywords: cost-effectiveness; intravenous acetaminophen; ketorolac; multimodal analgesia; pain; spine fusion.

FIGURE 1

Decision analytical model for determining cost-effectiveness of the use of 3 strategies for postoperative analgesia after spine fusion surgery: opioids alone, opioids + intravenous (IV) acetaminophen (APAP), and opioids + IV acetaminophen + ketorolac. The decision node is denoted by the filled square, while the chance events following the 3 strategies were similar and are indicated by filled circles following the brackets. The decision tree evaluated each strategy based on probabilities of occurrence opioid side effects/outcomes in high-dose and low-dose morphine subgroups (cut-off of morphine requirement 1.2 mg/kg/d, which was the average for the cohort). The base values included for probabilities of postoperative nausea vomiting (PONV), delayed per os (PO) intake, constipation, and hospital length of stay are detailed in Table 3. Cost-effectiveness was defined as the cost of the strategy to avoid significant opioid side effects

FIGURE 2

One-way sensitivity analysis examining the incremental cost-effectiveness ratio of the opioids + intravenous (IV) acetaminophen (APAP) strategy compared with the opioids + IV acetaminophen + ketorolac strategy as a function of the probability of requiring high-dose morphine for adequate analgesia (Panel A), and the probability of any significant opioid side effect from high dose-morphine in the opioids + IV acetaminophen strategy (Panel B). In the first panel, as the probability of requiring HDM in the opioids + IV acetaminophen increases from 0 to 0.16, the ICER increases, meaning the opioids + IV acetaminophen strategy becomes increasingly more costly for the benefit of opioid side effects avoided. Beyond a probability of 0.18, the opioids + IV acetaminophen + ketorolac strategy dominates by being less costly and more effective. The base-case value is 0.58. The opioids-only strategy was not included since it was a dominated strategy in the base-case analysis. Panel B shows that as the probability of significant side effects in the opioids + acetaminophen strategy increases from 0 to 0.47, the ICER increases, meaning the opioids + acetaminophen strategy becomes increasingly costly for the achieved benefit. At a probability exceeding 0.47, the opioids + acetaminophen + ketorolac strategy dominates (less costly and more effective at avoiding side effects) and the base-case value is 0.67

FIGURE 3

One-way sensitivity analysis examining the incremental cost-effectiveness of the opioids + intravenous (IV) acetaminophen (APAP) + ketorolac strategy compared with the opioids-only strategy (Panel A) as a function of cost of the 1000 mg (100 mL) IV acetaminophen bottle (shown on the x-axis). Present cost (2015 US $) is $42.50. The opioids + IV acetaminophen + ketorolac strategy continues to be the dominant strategy up to a cost of $121 per bottle. Beyond that cost, the strategy of opioids + IV acetaminophen + ketorolac has an increasing ICER. At per bottle costs exceeding $1200 (not shown in the figure), the opioids-only strategy becomes dominant. Panel B shows the costs for each of the 3 strategies at different costs per 1000 mg bottles of IV acetaminophen. At a cost exceeding $121 per bottle, the opioid-only strategy becomes the least costly