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Central Surgical Association

49th Annual Meeting

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Making a Painless Drain: Proof of Concept
Anna K. Gergen, Helen Madsen, Adam J. Rocker, Allana White, Kendra Jones, Dae Won Park, *Jessica A. Rove
Cardiothoracic Surgery, University of Colorado, Denver, Colorado, United States

Objective: Chest tubes account for a large proportion of postoperative pain following cardiothoracic operations. Pain associated with chest tubes can lead to shallow breathing, hypoventilation, and increased opioid needs, precipitating the current opioid crisis in the United States. While numerous studies have examined techniques to minimize pain and opioid use after chest incisions, none of these techniques have been universally adopted. The objective of this study was to develop a novel, cost-effective, lidocaine-eluting coating to reduce pain associated with postoperative chest tubes.
Methods: A prototype drain coating consisting of a lidocaine-eluting hydrogel was developed as follows. An aqueous solution containing gelatin (5%) was prepared in PBS and allowed to dissolve overnight. Micelle nanoparticles loaded with lidocaine-HCl were added to the gelatin solution. Glutaraldehyde (1%) was added to crosslink the gelatin into a hydrogel. The lidocaine-eluting hydrogel was dehydrated, resulting in a thin, stable polymer. Polymer-coated tubes were evaluated with scanning electron microscopy (Figure 1A). A lidocaine release assay demonstrated steady elution of lidocaine over several days (Figure 1B). During ex vivo testing, the hydrogel coating remained stable on the drain when passed between pig ribs. For in vivo testing, hydrogel material was polymerized into a disc shape and nanoparticles were loaded with 20 mg or 80 mg lidocaine. Control discs contained no nanoparticles or lidocaine. Discs were surgically implanted in the subcutaneous space of the abdominal wall of C57BL/6 mice. Using von Frey filaments, mice underwent preoperative baseline pain testing, followed by pain testing on post-procedure day 1 and 3. For each mouse, pain values measured in grams of force were normalized to their baseline pain tolerance.
Results: On post-procedure day 1, mice implanted with control discs demonstrated no change in pain tolerance compared to baseline, while mice implanted with 20 mg and 80 mg lidocaine-coated discs demonstrated a 2.4-fold (p=0.36) and 4.7-fold (p=0.01) increase in pain tolerance, respectively (Figure 1C). On post-procedure day 3, mice implanted with control discs demonstrated a 0.7-fold decrease in pain tolerance compared to baseline, while mice implanted with 20 mg and 80 mg lidocaine-coated discs demonstrated a 1.8-fold (p=0.88) and 8.4-fold (p=0.02) increase in pain tolerance, respectively.
Conclusions: We demonstrate successful development of a lidocaine-eluting chest tube with hydrogel coating, leading to improved pain tolerance in vivo. The concept of a drug-eluting drain coating has significant importance due to its potential universal application in a variety of drain types and insertion locations. Further studies are needed in large animals and eventually human subjects to confirm the safety and efficacy of lidocaine-eluting hydrogel-coated chest tubes.

Figure 1. A) Scanning electron microscopy of lidocaine-nanoparticle loaded hydrogel. B) In vitro release profile of gelatin hydrogel consisting of nanoparticles loaded with varying doses of lidocaine. C) Fold change in mice pain tolerance following subcutaneous implantation of hydrogel discs loaded with no lidocaine, 20 mg lidocaine, or 80 mg lidocaine.

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