Abstract
The use of spinal anesthesia with adjuvant intra-thecal opioids has been commonly used in total knee arthroplasty without documented clinical benefit. It has been associated with a potential increase in side effects, including nausea, vomiting, pruritus, urinary retention and oxygen usage. This double-blinded RCT investigated whether the addition of epimorph to spinal anesthesia in patients undergoing total knee arthroplasty resulted in superior pain control and decreased narcotic consumption without also causing an increase in postoperative complication rates.
We performed a prospective double-blind trial in patients undergoing primary total knee arthroplasty (TKA). Patients were randomised to receive either spinal anesthesia alone or spinal anesthesia with epimorph (150 ug). All patients received infiltration of a local anesthetic cocktail intraoperatively. Both the study patients and staff measuring outcomes were blinded to the experimental treatment received during data collection. Postoperatively, visual analogue scale (VAS) for pain was recorded at 6, 12, 18, 24, 36 and 48hrs and a final value at 1 week. Narcotic use, Foley insertion, oxygen requirements, nausea, vomiting and pruritus were recorded during the course of hospitalisation.
Forty-one patients were randomised into each of the spinal with epimorph and spinal alone treatment arms. The groups showed no significant differences in BMI, age, and gender distribution. In the first 12 hours postoperatively there was no difference in VAS for pain between the two groups, however there were significantly lower pain scores in the spinal alone patients at 18 hours (p=0.002), 24 hours (p=0.04) and 48 hours (p = 0.03) compared to the spinal with epimorph group. Narcotic usage was greater in the spinal group during the first 6 hours postoperatively, but beyond this time point narcotic usage was similar between the two groups. Additionally, there was a statistically significant increase in rate of complications with spinal epimorph including nausea (p=0.037) and pruritus (p=0.024). The incidence of urinary retention was greater in the spinal epimorph group, however this did not reach statistical significance.
This study demonstrates no clinical benefit with the addition of intra-thecal opioids to spinal anesthetic in primary TKA. In addition to a failing to reduce VAS pain scores and overall narcotic consumption, increased complication rates were seen. For these reasons, this study does not support the use of epimorph in addition to spinal anesthesia for pain control in TKA.
