Post-surgical immune suppression: another target to improve postoperative outcomes

Environment-responsive dendrobium polysaccharide hydrogel embedding manganese microsphere as a post-operative adjuvant to boost cascaded immune cycle against melanoma

Rationale: Surgical resection is a primary treatment for solid tumors, but high rates of tumor recurrence and metastasis post-surgery present significant challenges. Manganese (Mn2+), known to enhance dendritic cell-mediated cancer immunotherapy by activating the cGAS-STING pathway, has potential in post-operative cancer management. However, achieving prolonged and localized delivery of Mn2+ to stimulate immune responses without systemic toxicity remains a challenge. Methods: We developed a post-operative microenvironment-responsive dendrobium polysaccharide hydrogel embedded with Mn2+-pectin microspheres (MnP@DOP-Gel). This hydrogel system releases Mn2+-pectin microspheres (MnP) in response to ROS, and MnP shows a dual effect in vitro: promoting immunogenic cell death and activating immune cells (dendritic cells and macrophages). The efficacy of MnP@DOP-Gel as a post-surgical treatment and its potential for immune activation were assessed in both subcutaneous and metastatic melanoma models in mice, exploring its synergistic effect with anti-PD1 antibody. Result: MnP@DOP-Gel exhibited ROS-responsive release of MnP, which could exert dual effects by inducing immunogenic cell death of tumor cells and activating dendritic cells and macrophages to initiate a cascade of anti-tumor immune responses. In vivo experiments showed that the implanted MnP@DOP-Gel significantly inhibited residual tumor growth and metastasis. Moreover, the combination of MnP@DOP-Gel and anti-PD1 antibody displayed superior therapeutic potency in preventing either metastasis or abscopal brain tumor growth. Conclusions: MnP@DOP-Gel represents a promising drug-free strategy for cancer post-operative management. Utilizing this Mn2+-embedding and ROS-responsive delivery system, it regulates surgery-induced immune responses and promotes sustained anti-tumor responses, potentially increasing the effectiveness of surgical cancer treatments.

Surgical site infection in thoracic and lumbar fractures: incidence and risk factors in 11,401 patients from a nationwide administrative database

BACKGROUND CONTEXT

The rate of surgical site infection (SSI) following elective spine surgery ranges from 0.5%‒10%. Published reports suggest a higher SSI rate in non-elective spine surgery such as spine trauma; however, there is a paucity of large database studies examining this issue.

PURPOSE

The objective of this study was to investigate the incidence and risk factors of SSI in patients undergoing spine surgery for thoracic and lumbar fractures in a large population database.

STUDY DESIGN/SETTING

This is a retrospective study utilizing the PearlDiver Patient Claims Database.

PATIENT SAMPLE

Patients undergoing spine surgery for thoracic and lumbar fractures between 2015-2020 were identified in the PearlDiver Patient Claims Database using ICD-10 codes. Patients were excluded who had another surgery either 14 days before or 21 days after the index spine surgery, or pathologic fracture.

OUTCOME MEASURES

Rate of surgical site infection.

METHODS

Clinical data collected from the PearlDiver database based on ICD-10 codes included gender, age, diabetes, smoking status, obesity, Elixhauser Comorbidity Index (ECI), Charlson Comorbidity Index (CCI), and SSI. Univariate analysis was used to assess the association of potential risk factors and SSI. Multivariable analysis was used to identify independent risk factors of SSI. The authors have no conflicts of interest or funding sources to declare.

RESULTS

A total of 11,401 patients undergoing spine surgery for thoracic and lumbar fractures met inclusion criteria, and 1,065 patients were excluded. 860 patients developed SSI (7.5%). Risk factors significantly associated with SSI in univariate analysis included diabetes (OR 1.50; 95% CI, 1.30‒1.73; p<.001), obesity (OR 1.66; 95% CI, 1.44‒1.92; p<.001), increased age (p<.001), ECI (p<.001), and CCI (p<.001). On multivariable analysis, obesity and ECI were independently associated with SSI (p<.001 and p<.001, respectively).

CONCLUSIONS

Non-elective surgery for thoracic and lumbar fractures is associated with a 7.5% risk of SSI. Obesity and ECI are independent predictors of SSI in this population. Limitations include the reliance on accurate insurance coding which may not fully capture all SSI, and in particular superficial SSI. These findings provide a broad overview of the risk of SSI in this population at a national level and may also help counsel patients regarding risk.

Variable Response to Antifibrinolytics Correlates with Blood-loss and Transfusion in Posterior Spinal Fusion

PURPOSE

Posterior spinal fusion (PSF) activates the fibrinolytic protease plasmin, which is implicated in blood loss and transfusion. While antifibrinolytic drugs have improved blood loss and reduced transfusion, variable blood loss has been observed in similar PSF procedures treated with the same dose of antifibrinolytics. However, both the cause of this and the appropriate measures to determine antifibrinolytic efficacy during high-blood-loss spine surgery are unknown, making clinical trials to optimize antifibrinolytic dosing in PSF difficult. We hypothesized that patients undergoing PSF respond differently to antifibrinolytic dosing, resulting in variable blood loss, and that specific diagnostic markers of plasmin activity will accurately measure the efficacy of antifibrinolytics in PSF.

METHODS

A prospective study of 17 patients undergoing elective PSF with the same dosing regimen of TXA was conducted. Surgery-induced plasmin activity was exhaustively analyzed in perioperative blood samples and correlated to measures of inflammation, bleeding, and transfusion.

RESULTS

While markers of in vivo plasmin activation (PAP and D-dimer) suggested significant breakthrough plasmin activation and fibrinolysis (P < 0.01), in vitro plasmin assays, including TEG, did not detect plasmin activation. In vivo measures of breakthrough plasmin activation correlated with blood loss (R2 = 0.400, 0.264; P < 0.01), transfusions (R2 = 0.388; P < 0.01), and complement activation (R2 = 0.346, P < 0.05).

CONCLUSIONS

Despite all patients receiving a high dose of TXA, its efficacy among patients was variable, indicated by notable intra-operative plasmin activity. Markers of in vivo plasmin activation best correlated with clinical outcomes. These findings suggest that the efficacy of antifibrinolytic therapy to inhibit plasmin in PSF surgery should be determined by markers of in vivo plasmin activation in future studies.

LEVEL OF EVIDENCE

Level II-diagnostic.