Local anesthetics for skin grafting and local flaps

Use of a topical mix of lidocaine and prilocaine during split-thickness skin graft harvest improves postoperative recovery-A prospective randomized controlled trial

PURPOSE

To provide evidence of efficacy and postoperative benefit of topical anesthesia (TA) for harvesting split-thickness skin graft (STSG) in an Asian population.

MATERIALS AND METHODS

Patients with well-granulating wounds with skin grafting were randomized into TA or general anesthesia (GA) groups. In the TA group, an eutectic mixture of lidocaine and prilocaine (EMLA) was applied. Perioperative heart rate, postoperative donor site pain, adverse effects, patients' satisfaction, duration of surgery, and operation room (OR) stay duration were recorded.

RESULTS

Thirty-nine patients (19 males, 20 females; mean age 54.9 ± 17.8) were included. Twenty underwent TA and 19 underwent GA for STSG. The TA group patients had tolerable pain during skin graft harvesting (VAS, 0.85 ± 1.5). Average EMLA exposure duration was 180.3 ± 65.8 min, and the amount applied was 1.72 ± 0.43 g/10 cm². The TA group had lower donor site pain score at one hour postoperatively (1.34 ± 1.49 vs 3.08 ± 1.90, p = 0.005), lower OR stay duration (36.5 ± 6.5 min vs 65.1 ± 17.2 min, p < 0.001) and less adverse effects than the GA group.

CONCLUSION

Harvesting STSG under TA with EMLA is an effective and efficient approach for most Asian patients with less early postoperative donor site pain and fewer adverse effects.

The effect of local anesthetic on pro-inflammatory macrophage modulation by mesenchymal stromal cells

Administering local anesthetics (LAs) peri- and post-operatively aims to prevent or mitigate pain in surgical procedures and after tissue injury in cases of osteoarthritis (OA) and other degenerative diseases. Innovative tissue protective and reparative therapeutic interventions such as mesenchymal stromal cells (MSCs) are likely to be exposed to co-administered drugs such as LAs. Therefore, it is important to determine how this exposure affects the therapeutic functions of MSCs and other cells in their target microenvironment. In these studies, we measured the effect of LAs, lidocaine and bupivacaine, on macrophage viability and pro-inflammatory secretion. We also examined their effect on modulation of the macrophage pro-inflammatory phenotype in an in vitro co-culture system with MSCs, by quantifying macrophage tumor necrosis factor (TNF)-α secretion and MSC prostaglandin E2 (PGE2) production. Our studies indicate that both LAs directly attenuated macrophage TNF-α secretion, without significantly affecting viability, in a concentration- and potency-dependent manner. LA-mediated attenuation of macrophage TNF-α was sustained in co-culture with MSCs, but MSCs did not further enhance this anti-inflammatory effect. Concentration- and potency-dependent reductions in macrophage TNF-α were concurrent with decreased PGE2 levels in the co-cultures further indicating MSC-independent macrophage attenuation. MSC functional recovery from LA exposure was assessed by pre-treating MSCs with LAs prior to co-culture with macrophages. Both MSC attenuation of TNF-α and PGE2 secretion were impaired by pre-exposure to the more potent bupivacaine and high dose of lidocaine in a concentration-dependent manner. Therefore, LAs can affect anti-inflammatory function by both directly attenuating macrophage inflammation and MSC secretion and possibly by altering the local microenvironment which can secondarily reduce MSC function. Furthermore, the LA effect on MSC function may persist even after LA removal.

Effect of Local Anesthetics on Human Mesenchymal Stromal Cell Secretion

Anti-fibrotic and tissue regenerative mesenchymal stromal cell (MSC) properties are largely mediated by secreted cytokines and growth factors. MSCs are implanted to augment joint cartilage replacement and to treat diabetic ulcers and burn injuries simultaneously with local anesthetics, which reduce pain. However, the effect of anesthetics on therapeutic human MSC secretory function has not been evaluated. In order to assess the effect of local anesthetics on the MSC secretome, a panel of four anesthetics with different potencies - lidocaine, procaine, ropivacaine and bupivacaine - was evaluated. Since injured tissues secrete inflammatory cytokines, the effects of anesthetics on MSCs stimulated with tumor necrosis factor (TNF)-α and interferon (IFN)-γ were also measured. Dose dependent and anesthesia specific effects on cell viability, post exposure proliferation and secretory function were quantified using alamar blue reduction and immunoassays, respectively. Computational pathway analysis was performed to identify upstream regulators and molecular pathways likely associated with the effects of these chemicals on the MSC secretome. Our results indicated while neither lidocaine nor procaine greatly reduced unstimulated cell viability, ropivacaine and bupivacaine induced dose dependent viability decreases. This pattern was exaggerated in the simulated inflammatory environment. The reversibility of these effects after withdrawal of the anesthetics was attenuated for TNF-α/IFN-γ-stimulated MSCs exposed to ropivacaine and bupivacaine. In addition, secretome analysis indicated that constitutive secretion changes were clearly affected by both anesthetic alone and anesthetic plus TNFα/IFNγ cell stimulation, but the secretory pattern was drug specific and did not necessarily coincide with viability changes. Pathway analysis identified different intracellular regulators for stimulated and unstimulated MSCs. Within these groups, ropivacaine and bupivacaine appeared to act on MSCs similarly via the same regulatory mechanisms. Given the variable effect of local anesthetics on MSC viability and function, these studies underscore the need to evaluate MSC in the presence of medications, such as anesthetics, that are likely to accompany cell implantation.