Pain and Opioid Consumption and Mobilization After Surgery

Discussion

Postoperative mobilization was inversely associated with pain scores, suggesting that inadequate postoperative analgesia impairs mobilization. Unsurprisingly, the association was threefold stronger when analysis was restricted to daytime, which is reasonable since few patients mobilize at night, irrespective of pain management. The association was also 1.5-fold stronger when patients had open surgery. In contrast, there was little association between opioid consumption and overall mobilization. To the extent that the relationship is causal, our results suggest that improving postoperative analgesia by about 3 points on an 11-point Likert scale might increase mobilization time by as much as 25%—even if opioids are used to improve analgesia.

Remarkably, all postoperative complications occurred in patients who were in the lowest two mobilization quartiles, those who spent less than 7% (1.7 h/day) of their time sitting or standing during the initial 48 postoperative hours. Importantly, potential confounders as American Society of Anesthesiologists Physical Status as well as surgery approach and duration did not differ much among postoperative pain levels, suggesting similar surgical severity and baseline comorbidities. A difference of 0.7 h of mobilization per day between patients with low or high level of pain might seem marginal. Nonetheless, this small difference corresponded to a substantial difference in the incidence of complications. Even 1.6 h of mobilization per day are therefore associated with reduced complications.

The average mobilization time in our cohort was about 2 h/day, which is the recommended out-of-bed time for the day of surgery, but considerably shorter than the times recommended thereafter by many enhanced recovery pathways.^[5–7] Low adherence to mobilization recommendations is consistent with many qualitative reports.^[6,18,43,44] We note, though, that enhanced recovery after surgery mobilization recommendations are largely based on expert opinion rather than on strong evidence. Our results suggest that 2 h/day may suffice.^[2,5,6]

Although postoperative mobilization is included in most enhanced recovery pathways,^[16,45–47] supportive evidence remains sparse.^[6] On one hand, Daskivich et al.^[18] report in a 100-patient study that 1,000 steps/day on the first postoperative day after major abdominal surgery was associated with lower probability of a prolonged length of stay. On the other hand, in patients recovering from colorectal surgery, staff-directed out-of-bed activities did not reduce the duration of hospitalization.^{[12–17,19–23]} Moreover, a systematic review of 500 patients concluded that current evidence is insufficient to draw strong conclusions regarding the benefits of early mobilization on postoperative outcomes.^[11] Some discrepancies might be partly explained by large variability in mobilization quantification, with some reports relying on nursing or patients' subjective reports^[6,47] while others used walking distance^[19] or daily steps.^[16–18] An important consideration for all observational analyses—including ours—is that failure to mobilize early may be a reflection of poor recovery, rather than being the cause.

Mobility data were missing for 9% [3% to 20%] of the initial postoperative 48 h, in part because continuous monitoring was purely observational. Clinicians were therefore blinded to results, and to disconnections or technical failures. Missing data are always a concern in clinical research, but more so if data are missing nonrandomly. In our case, it is plausible that disconnections were most common in mobile patients, thus diminishing the apparent difference in mobility time for the highest and lowest quartiles. We adjusted for many potential confounding factors including duration of surgery, but it remains likely that larger and open procedures that cause much tissue injury simultaneously provoke pain and impair mobilization. Although few of our patients experienced complications, after adjusting for as many important confounders as we could, there was still a strong relationship between complications and mobilization, even over a small range of sitting and standing times. However, the association between postoperative complications and low levels of mobilization cannot exclude reverse causality since patients with postoperative complications surely move less. The extent to which the association between pain and mobilization is causal, and thus amenable to intervention, remains unclear. A future trial of analgesic approaches with differing efficacies could better evaluate causality.

Conclusions

In patients recovering from abdominal surgery on an enhanced recovery pathway, lower pain scores are associated with increased mobility, even when opioid consumption is increased. Patients spent only about 2 h/day mobilized, which is considerably less than the recommended time. There appears to be little beyond expert opinion to support the recommended daily mobilization goal, and our results suggest that 2 h/day may suffice.

Research Support

The underlying Effect of Intravenous Acetaminophen on Postoperative Hypoxemia After Abdominal Surgery: the FACTOR Randomized Clinical Trial was supported by an investigator-initiated research grant from Mallinckrodt Pharmaceuticals (Hampton, New Jersey); and the underlying Transversus Abdominis Plane Block with Liposomal Bupivacaine versus Continuous Epidural Analgesia for Major Abdominal Surgery: the EXPLANE clinical trial was funded by PACIRA Pharmaceuticals (Parsippany, New Jersey). Sotera Wireless, Inc. (San Diego, California) and Respiratory Motion, Inc. (Watertown, Massachusetts) provided devices and disposables. However, this analysis was supported by internal funds only, and the sponsors had no role whatsoever in data analysis, manuscript preparation, or the decision to submit for publication. The sponsors have not reviewed this manuscript. Dr. Rivas received a grant from Instituto Salud Carlos III, Madrid, Spain (BA18/00048).

Anesthesiology. 2022;136(1):115-126. © 2022 American Society of Anesthesiologists | Lippincott Williams & Wilkins