Endothelial HIF signaling regulates pulmonary fibrosis-associated pulmonary hypertension.

Pulmonary hypertension (PH) complicating chronic parenchymal lung disease, such as idiopathic pulmonary fibrosis, results in significant morbidity and mortality. Since the hypoxia-inducible factor (HIF) signaling pathway is important for development of pulmonary hypertension in chronic hypoxia, we investigated whether HIF signaling in vascular endothelium regulates development of PH related to pulmonary fibrosis. We generated a transgenic model in which HIF is deleted within vascular endothelial cells and then exposed these mice to chronic intraperitoneal bleomycin to induce PH associated with lung fibrosis. Although no differences in the degree of fibrotic remodeling were observed, we found that endothelial HIF-deficient mice were protected against development of PH, including right ventricle and pulmonary vessel remodeling. Similarly, endothelial HIF-deficient mice were protected from PH after a 4-wk exposure to normobaric hypoxia. In vitro studies of pulmonary vascular endothelial cells isolated from the HIF-targeted mice and controls revealed that endothelial HIF signaling increases endothelial cell expression of connective tissue growth factor, enhances vascular permeability, and promotes pulmonary artery smooth muscle cell proliferation and wound healing ability, all of which have the potential to impact the development of PH in vivo. Taken together, these studies demonstrate that vascular endothelial cell HIF signaling is necessary for development of hypoxia and pulmonary fibrosis associated PH. As such, HIF and HIF-regulated targets represent a therapeutic target in these conditions.

Determining the Effect of Intraoperative TXA on Postoperative Blood Loss in ACDF.

STUDY DESIGN: Retrospective cohort study using prospectively collected data. OBJECTIVE: To determine the effectiveness of intraoperative tranexamic acid (TXA) in anterior cervical discectomy and fusion (ACDF) on postoperative blood loss. SUMMARY OF BACKGROUND DATA: TXA has been proven to be a safe and effective agent in reducing blood loss after cervical surgery; however, its efficacy when used intraoperatively for ACDF surgeries had yet to be researched. Currently, there are few studies examining the effects of intraoperative TXA in cervical spinal fusion, and none specifically examining TXA use in ACDF. METHODS: A tertiary medical center's prospectively collected spine registry was queried between 1/1/18 and 12/1/21 for all patients who underwent elective ACDF surgery and received a drain postoperatively. Patients were separated into 2 groups; those who had received intraoperative TXA and those who did not. Baseline demographic and operative variables were collected from the registry. The primary outcome was postoperative blood loss over a 24-hour period. Secondary outcomes included total drain output, intraoperative estimated blood loss, operative duration, drain duration, changes in preoperative to postoperative hemoglobin and hematocrit levels, and rate of transfusions, complications, revisions, and reoperations. Univariate and multivariate regression analyses were performed. RESULTS: Two hundred eighty-six patients were included. One hundred ninety patients underwent ACDF and did not receive intraoperative TXA, whereas 96 patients underwent ACDF and did receive TXA. There were no differences in any demographic or baseline variables. Multivariate analysis showed intraoperative TXA was associated with shorter drain duration (ß=-5.74, 95% CI: -10.9 to -0.53, P =0.031) and reduction in 24-hour drain output (ß=-12.2, 95% CI: -19.4 to -4.89, P =0.001) and total drain output (ß=-14.0, 95% CI: -22.9 to -5.05, P =0.002). CONCLUSIONS: TXA use during ACDF procedures leads to a decrease in perioperative blood loss and faster drain removal. TXA is an effective and safe agent for reducing perioperative blood loss in ACDF surgery. LEVEL OF EVIDENCE: III.