Association between Opioid Dose, Acute Post-operative Pain and Walking Distance Following Lumbar Spine Surgery

The opioid doses on post-operative day 1 (POD1) is a major predictor of recovery in patients following lumbar spine surgery (LSS). However, the opioid doses vary widely in clinical practice. Thus, the objective of this study was to explore the associations between opioid doses on POD1, pain and function during a hospital stay in patients following LSS.

This study used medical records of patients who underwent LSS between January 2007 and March 2018. The patients were divided into three groups (high, medium and low dose) according to the amount of opioid (oral morphine equivalents; OME) taken on POD1. A propensity score matching across the three groups was performed to account for main confounding factors related to the opioid dose, pain intensity and gait distance, which identified 114 matched patients in each group. The difference of pain intensity and gait distance between the groups on POD1 was analysed.

The OME in each group on POD1 was 168.75 ± 69.50 mg (high), 65.92 ± 13.28 mg (medium) and 16.90 ± 9.80 mg (low) (P < .0001). Pain intensity on the postoperative day 2 (POD2) and 3 (POD3) was not different between the groups (P > .05). Gait distance on POD2 and POD3 was different between the groups but did not reach the adjusted statistically significant level of 0.017: high (170.3 ± 152.77 feet) versus medium (247.57 ± 216.65 feet) dose on POD2 (P = .04); high (179.31 ± 135.722 feet) versus low (230.94 ± 145.74 feet) dose on POD3 (P = .03); and medium (196.98 ± 159.42 feet) versus low (261.00 ± 161.03 feet) dose on POD3 (P = .09).

The findings indicated that high dose opioids on POD1 did not translate into better outcomes of pain and gait in patients following LSS. In fact, patients in medium and low dose groups walked a greater distance on POD2 and POD3. Use of a functional outcome such as gait should be considered to optimize opioid dose effects.