Background and Aims

Inguinal hernia repair is a common surgical procedure [1], after which up to 40% of patients report significant acute pain and 10% develop chronic pain [2,3]. We aim to develop a collagen-based mesh system to elute levobupivacaine to effectively manage acute pain.

Methods

Collagen and levobupivacaine were chosen based on their desirable safety/biocompatibility/efficacy. Elution experiments tested collagen alone (2-10mg/ml) and crosslinked by various concentrations of EDC/NHS (0.1-1000mM).
Twenty-three rats (n=5-6/group) underwent sham procedure, hernioplasty alone or with the collagen/mesh device loaded with 50mg or 100mg levobupivacaine. Open Field (OF) and Von Frey (VF) testing occurred at baseline(-24hrs), and 4, 24 & 48hrs post-surgery. Locomotor activity was also assessed in the homecage. Animals were euthanised 48hrs post-surgery.

Results

Following optimisation, elution of the maximum loadable drug was achieved over 48hrs. Surgery reduced locomotor activity in the OF 4hrs post-surgery and in the homecage during the first 4hrs post-surgery. Surgery also significantly increased responsiveness to VF filaments at 24 hrs. Reduced locomotor activity and increased responsiveness in the VF are important pain-related phenotypes in this model. Homecage and OF locomotor activity was unaffected by the 50 and 100mg devices.  The 100mg device significantly reduced responsiveness in the VF test compared to controls at 24 hrs. 

Conclusions

These data suggest that the device may be effective in alleviating mechanical allodynia following inguinal hernia repair. Improved effectiveness may be achieved by increasing the dose or testing alternative analgesics. 

Acknowledgements

Financial support from Science Foundation Ireland (SFI) and co-funded under the European Regional Development Fund, Grant Number 13/RC/2073.

References

[1] Jenkins & O’Dwyer, (2008) BMJ, 336(7638); 269-272.
[2] McGrath et al., (2008) Canadian Journal of Anaesthesia, 51(9); 886-91.
[3] Aasvang (2005) British Journal of Anaesthesia, 95(1); 67-96

DEVELOPMENT AND PRECLINICAL TESTING OF A PROTOTYPE LEVOBUPIVACAINE-ELUTING DEVICE FOR THE TREATMENT OF POSTOPERATIVE PAIN FOLLOWING INGUINAL HERNIA REPAIR