Thermal Hyperalgesia After Sciatic Nerve Block in Rat Is Transient and Clinically Insignificant

Abstract

Ropivacaine has been associated with transient heat hyperalgesia in sciatic nerve blocks in rat. The goal of the present study was to evaluate the hypothesized presence of transient heat hyperalgesia after perineural injection of ropivacaine with a secondary subanalysis of 2 published studies. Paw withdrawal latency was used to assess the duration of sensory blockade and presence of heat hyperalgesia at 210, 240, 270, and 300 minutes and 24 hours after injection. The analysis revealed hyperalgesia at a single time point (240 minutes after injection; mean difference, -0.60 seconds; P = 0.012) that resolved within 30 minutes, and there was no other significant hyperalgesia at other time points. Although statistically significant, the single time point measurement represented only an 11% change from baseline and was no longer present 30 minutes later. These data support the need for a reevaluation of the interpretation that pain can be worsened by perineural ropivacaine injection.

Dexamethasone as Adjuvant to Bupivacaine Prolongs the Duration of Thermal Antinociception and Prevents Bupivacaine-Induced Rebound Hyperalgesia via Regional Mechanism in a Mouse Sciatic Nerve Block Model

“…Patients commonly describe an intense burning pain initially as the nerve block resolves, which is an undesirable clinical ramification of peripheral nerve blocks [ 24 ]. Similarly, 0.5% ropivacaine could also induce a transient episode of rebound heat hyperalgesia following the resolution of sensory blockade in a rat sciatic nerve block model even when no painful surgery was performed in the sciatic nerve distribution [ 25 , 26 ]. This interesting neurobehavioral phenomenon was also observed in our study.…”

Possible Mechanisms of Rebound Pain After Peripheral Nerve Block Subsides and Preventive Therapy Measures

“…When Kolarczyk et al [2] examined the behavioral changes that occurred in rats after receiving a single injection of ropivacaine to block the sciatic nerve, they discovered that significant thermal nociceptive hypersensitivity might develop after the effect of the nerve block had worn off. This finding was later corroborated by Janda et al [3]. The sciatic nerve was also blocked by An [4] and colleagues using bupivacaine plus dexamethasone (test group) and without dexamethasone (control group), as well as toluidine blue staining and immunohistochemistry.…”

Peripheral nerve block and rebound pain: literature review

“… 14 Transient thermal hyperalgesia was also found in another study with rats after 4 hours of blockade. 13 Acute opioid-induced hyperalgesia is another hypothesis suggested. 26…”

“…Despite the success of regional anesthesia, several studies have demonstrated the occurrence of the phenomenon known as “rebound pain” as soon as the original blockade disappears. 6 , 10 , 11 , 12 Although rebound pain occurs in a wide variety of surgeries 13 , 14 and the phenomenon is well recognized, all studies have several methodological limitations that make it impossible to determine its clinical significance.…”