Postoperative pain following epidural local anaesthetic bolus administration after lumbar fusion: a retrospective analysis

Background Postoperative pain remains a serious concern after posterior lumbar interbody fusion (PLIF). Intraoperative epidural boluses of local anaesthetics (LA) have been proposed to reduce postoperative pain, but evidence is inconsistent. This study evaluated the association between an epidural bolus and pain in the post-anaesthesia care unit (PACU) following PLIF. Methods A retrospective study was conducted including 147 PLIF patients. Patients were divided into the bolus ( n = 80) or control group ( n = 67) based on whether an epidural LA bolus was administered at the end of surgery. Primary outcomes: static (in rest) and dynamic (in movement) pain intensity (Numeric Rating Scale, NRS) in the PACU. Secondary outcomes: ward NRS, opioid consumption (Morphine Milligram Equivalents, MME), PACU and hospital length of stay (LOS), and analgesia- and surgery-related complications within 1 month. The multivariable regression models were adjusted for age, sex, BMI, ASA classification, preoperative opioid use, previous spinal surgery, and screw trajectory. Results The groups were similar in age and sex, but differed in BMI, ASA classification, prior spinal surgery, and screw trajectory. Primary outcome : No significant differences were observed in static (Mann–Whitney U = 2439.0, p = 0.60) or dynamic (Mann–Whitney U = 1944.5, p = 0.48) NRS in the PACU. After adjustments, both static (MD -0.28, 95% CI -1.42 to 0.87, p = 0.63) and dynamic NRS (MD -0.51, 95% CI -1.69 to 0.67, p = 0.39) remained similar. Secondary outcomes : Ward NRS and opioid consumption in the PACU did not differ, but MME/hour on postoperative day 1 was lower in the bolus group (MD -0.34, 95% CI -0.57 to -0.11, p = 0.004). PACU LOS, hospital LOS, and analgesia-related complications were similar. Surgery-related complications < 1 month were not increased in the bolus group. Conclusions This retrospective study found no association between epidural LA bolus administration and lower postoperative pain or opioid consumption in the PACU after PLIF. However, secondary analyses suggested lower opioid consumption on postoperative day 1.