Postoperative pain increased with sequential surgery
medwireNews: Pain sensitivity in patients who undergo staged bilateral total knee arthroscopy (TKA) is greater after the second than the first operation, a study by South Korean researchers has found.
The observations suggest that surgical injury induces hyperalgesia via central sensitization, highlighting the need for therapeutic approaches to reduce pain in these patients, say the authors.
Sang-Hwan Do (Seoul National University Bundang Hospital) and team studied 30 patients with bilateral knee osteoarthritis who underwent staged sequential TKA at a 1-week interval.
Results showed that self-reported pain, assessed on a visual analog scale 24 hours after surgery, was greater after the second operation than after the first, with median scores of 49.3 versus 21.8 at rest, and 83.7 versus 74.3 at maximum knee flexion. Both differences were statistically significant.
Analgesia requirements supported this finding, with patients receiving a higher cumulative dose of opiate analgesic (229.4 vs 77.5 µg) during the first 24 hours and a greater amount of rescue analgesics (50.0 vs 13.3 mg) during the first 48 hours after the second than the first operation.
Use of antiemetics postoperatively did not differ between the first and second surgeries.
Writing in Pain, the study authors surmise that pain is greater in the second operated knee than in the first, despite the identical TKA protocol, same pathology (degenerative arthritis), and similar preoperative knee pain.
These similarities mean that the nociceptive stimuli arising from the operated knees would be equivalent for the first and second TKAs; thus, the increase in perceived pain in the second knee represents hyperalgesia.
They suggest that the mechanism underlying this hyperalgesia is pain-induced neuroplasticity, or central sensitization, triggered by persistent nociceptive inputs from the first operated knee that alter sensory processing and sensitize subcortical structures.
“Under the condition of central sensitization, the transmission of further nerve impulses from the periphery to the brain can be amplified, which may account for the hyperalgesia of the second knee,” Do et al propose.
The team concludes: “Therapeutic approaches to reduce such hyperalgesia induced by sequential surgical procedures deserve further study, given the detrimental impact of unrelieved postoperative pain and considering the potential contribution to the study of hyperalgesia mechanisms.”
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By Joanna Lyford, Senior medwireNews Reporter