Ultrasound-guided serratus plane block with continuous postoperative drug delivery system for acute nociceptive and neuropathic pain after mastectomy

Objectives
The study compared the effect of pre-emptive serratus plane block, with postoperative continuous drug delivery: into the serratus plane (bupivacaine 0.125% CDB), or around the wound (lidocaine 5% patches LP) on acute nociceptive and neuropathic pain after mastectomy.
Methods
This randomized-controlled blinded study was conducted on 43 women scheduled for mastectomy for breast cancer, under standard general anaesthesia and pre-emptive serratus plane block. Patients were randomly assigned to 2 groups according to postoperative analgesia: Group (S) received a 6 ml hourly doses of bupivacaine (0.125%) for 24 hrs using an epidural catheter inserted into the serratus plane and Group (L) received 2 LP around the wound for 12 hrs/24 hrs. IV morphine (3 mg) was given to patients with visual analogue scale >3 and repeated at 10 min intervals if needed.
Measurements
Primary outcome was visual analogue scale (VAS) for nociceptive pain at rest and arm movement for 24 hrs postoperatively. Secondary outcomes included incidence, characters and severity of acute neuropathic pain, using DN4 questionnaire and Neuropathic Pain Scale (NPS) for 4 weeks. Hypothesia to touch and temperature, mechanical allodynia and hyperalgesia were assessed between T2-T6 compared to the other side for 4 weeks. Patient satisfaction was measured by satisfaction score.
Results
There was no significant difference between the two groups regarding VAS at rest and movement, incidence, duration and sites of neuropathic pain and its effect on sleep, mood and work. The intensity of numbness measured by NPS was significantly less in Group L than Group S in the third postoperative week (P ≤ 0.05). Patients ‘satisfaction with postoperative pain relief was higher in Group L (P ≤ 0.05).
Conclusion
LP are as effective in reducing acute nociceptive pain as continuous bupivacaine delivery into the serratus plane. They are superior in reducing numbness and favoured by patients postmastectomy.