Collecting And Measuring Wound Exudate Biochemical Mediators In Surgical Wounds

Summary

This article provides a detailed and visual description of a methodology for collecting and measuring biochemical inflammatory and nociceptive mediators at the surgical wound site following cesarean delivery. This human bioassay has been used to determine correlations between wound and serum cytokine concentrations and drug-mediated changes in wound cytokines, chemokines and neuropetides.

Abstract

We describe a methodology by which we are able to collect and measure biochemical inflammatory and nociceptive mediators at the surgical wound site. Collecting site-specific biochemical markers is important to understand the relationship between levels in serum and surgical wound, determine any associations between mediator release, pain, analgesic use and other outcomes of interest, and evaluate the effect of systemic and peripheral drug administration on surgical wound biochemistry. This methodology has been applied to healthy women undergoing elective cesarean delivery with spinal anesthesia. We have measured wound exudate and serum mediators at the same time intervals as patient's pain scores and analgesics consumption for up to 48 hours post-cesarean delivery. Using this methodology we have been able to detect various biochemical mediators including nerve growth factor (NGF), prostaglandin E2 (PG-E2) substance P, IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, TNFα, INFγ, G-CSF, GM-CSF, MCP-1 and MIP-1β. Studies applying this human surgical wound bioassay have found no correlations between wound and serum cytokine concentrations or their time-release profile (J Pain. 2008; 9(7):650-7).¹ We also documented the utility of the technique to identify drug-mediated changes in wound cytokine content (Anesth Analg 2010; 111:1452-9).²

Introduction

After a surgical incision, resident and migrating inflammatory cells release pro- and anti-inflammatory cytokines, prostanoids, neuropeptides and chemokines that are important for initiating and maintaining pain.^3,4 The ability to collect site-specific biochemical markers is critical to determine the relationship between levels in serum and surgical wound, understand the complex relationship between mediator release and surgical pain, and to be able to evaluate the effect of both systemic and peripheral drug administration on surgical wound biochemistry. Studies have focused on systemic measurements of biochemical mediators and have not considered site-spec....

Protocol

1. Study Protocol

• Obtain Institutional Review Board approval and written informed consent.
• Select an appropriate surgical population for study conduct. This methodology has only been applied to cesarean delivery wounds but most surgical wounds would be appropriate.
• Consider inclusion and exclusion criteria for your study participation. Patients and procedures with high rates of surgical wound infection may not be appropriate.
• Standardize anesthesia and postoperative management for all patients to avoid potential confounders.

2. Nociceptive and Inflammatory Biochemical Mediator Collection

Results

Using this methodology we have been able to detect all biochemical mediators outlined above with the exception of IL-5 in wound exudate and plasma.^1,2 Some additional cytokines were not detected in plasma (IL-4, IL-17, TNFα, INFγ, GM-CSF).¹ The time course of measured cytokines and chemokines in reported studies were consistent, reaching a plateau within the first few hours that was sustained for the 24 hour observation period..^1,2 However, NGF increased steadily over the 24-hours collect.......

Discussion

This methodology outlined above has been found to be sensitive enough to detect biochemical inflammatory and nociceptive mediators in wound exudate. Sampling at various time-points has also allowed us to observe changes of these mediators over time.^1,2 We are not aware of any other human surgical wound assay that can serially measure the release profile of inflammatory and nociceptive mediators in surgical wound exudate. Results from our methodology of wound exudate collection from the surgical incision site i.......