Candidate Kidney Protective Strategies for Patients Undergoing Major Abdominal Surgery: A Secondary Analysis of the RELIEF Trial Cohort.

BACKGROUND: Acute kidney injury (AKI) is common after major abdominal surgery. Selection of candidate kidney protective strategies for testing in large trials should be based on robust preliminary evidence. METHODS: A secondary analysis of the Restrictive versus Liberal Fluid Therapy in Major Abdominal Surgery (RELIEF) trial was conducted in adult patients undergoing major abdominal surgery and randomly assigned to a restrictive or liberal perioperative fluid regimen. The primary outcome was maximum AKI stage before hospital discharge. Two multivariable ordinal regression models were developed to test the primary hypothesis that modifiable risk factors associated with increased maximum stage of postoperative AKI could be identified. Each model used a separate approach to variable selection to assess the sensitivity of the findings to modeling approach. For model 1, variable selection was informed by investigator opinion; for model 2, the Least Absolute Shrinkage and Selection Operator (LASSO) technique was used to develop a data-driven model from available variables. RESULTS: Of 2,444 patients analyzed, stage 1, 2, and 3 AKI occurred in 223 (9.1%), 59 (2.4%), and 36 (1.5%) patients, respectively. In multivariable modeling by model 1, administration of a nonsteroidal anti-inflammatory drug or cyclooxygenase-2 inhibitor, intraoperatively only (odds ratio, 1.77 [99% CI, 1.11 to 2.82]), and preoperative day-of-surgery administration of an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker compared to no regular use (odds ratio, 1.84 [99% CI, 1.15 to 2.94]) were associated with increased odds for greater maximum stage AKI. These results were unchanged in model 2, with the additional finding of an inverse association between nadir hemoglobin concentration on postoperative day 1 and greater maximum stage AKI. CONCLUSIONS: Avoiding intraoperative nonsteroidal anti-inflammatory drugs or cyclooxygenase-2 inhibitors is a potential strategy to mitigate the risk for postoperative AKI. The findings strengthen the rationale for a clinical trial comprehensively testing the risk-benefit ratio of these drugs in the perioperative period.

Tranexamic acid alters the immunophenotype of phagocytes after lower limb surgery.

BACKGROUND: Tranexamic acid (TXA) is an antifibrinolytic agent frequently used in elective surgery to reduce blood loss. We recently found it also acts as a potent immune-modulator in patients undergoing cardiac surgery. METHODS: Patients undergoing lower limb surgery were enrolled into the "Tranexamic Acid in Lower Limb Arthroplasty" (TALLAS) pilot study. The cellular immune response was characterised longitudinally pre- and post-operatively using full blood examination (FBE) and comprehensive immune cell phenotyping by flowcytometry. Red blood cells and platelets were determined in the FBE and levels of T cell cytokines and the plasmin-antiplasmin complex determined using ELISA. RESULTS: TXA administration increased the proportion of circulating CD141+ conventional dendritic cells (cDC) on post-operative day (POD) 3. It also reduced the expression of CD83 and TNFR2 on classical monocytes and levels of circulating IL-10 at the end of surgery (EOS) time point, whilst increasing the expression of CCR4 on natural killer (NK) cells at EOS, and reducing TNFR2 on POD-3 on NK cells. Red blood cells and platelets were decreased to a lower extent at POD-1 in the TXA group, representing reduced blood loss. CONCLUSION: In this investigation we have extended our examination on the immunomodulatory effects of TXA in surgery by also characterising the end of surgery time point and including B cells and neutrophils in our immune analysis, elucidating new immunophenotypic changes in phagocytes as well as NK cells. This study enhances our understanding of TXA-mediated effects on the haemostatic and immune response in surgery, validating changes in important functional immune cell subsets in orthopaedic patients.

Rationale and design of the intravenous iron for treatment of anemia before cardiac surgery trial.

Background Approximately 20% to 30% of patients awaiting cardiac surgery are anemic. Anemia increases the likelihood of requiring a red cell transfusion and is associated with increased complications, intensive care, and hospital stay following surgery. Iron deficiency is the commonest cause of anemia and preoperative intravenous (IV) iron therapy thus may improve anemia and therefore patient outcome following cardiac surgery. We have initiated the intravenous iron for treatment of anemia before cardiac surgery (ITACS) Trial to test the hypothesis that in patients with anemia awaiting elective cardiac surgery, IV iron will reduce complications, and facilitate recovery after surgery. Methods ITACS is a 1,000 patient, international randomized trial in patients with anemia undergoing elective cardiac surgery. The patients, health care providers, data collectors, and statistician are blinded to whether patients receive IV iron 1,000 mg, or placebo, at 1-26 weeks before their planned date of surgery. The primary endpoint is the number of days alive and at home up to 90 days after surgery. Results To date, ITACS has enrolled 615 patients in 30 hospitals in 9 countries. Patient mean (SD) age is 66 (12) years, 63% are male, with a mean (SD) hemoglobin at baseline of 118 (12) g/L; 40% have evidence (ferritin <100 ng/mL and/or transferrin saturation <25%) suggestive of iron deficiency. Most (59%) patients have undergone coronary artery surgery with or without valve surgery. Conclusions The ITACS Trial will be the largest study yet conducted to ascertain the benefits and risks of IV iron administration in anemic patients awaiting cardiac surgery.

Tranexamic acid modulates the immune response and reduces postsurgical infection rates.

Tranexamic acid (TXA) is an antifibrinolytic agent that blocks plasmin formation. Because plasmin is known to promote inflammatory and immunosuppressive responses, we explored the possibility that plasmin-mediated immunosuppression in patients undergoing cardiac surgery can be directly reversed by TXA and decrease postoperative infection rates. The modulatory effect of TXA on inflammatory cytokine levels and on innate immune cell activation were evaluated with multiplex enzyme-linked immunosorbent assay and flow cytometry, respectively. Postoperative infection rates were determined in patients undergoing cardiac surgery and randomized to TXA (ACTRN12605000557639; http://www.anzca.edu.au). We demonstrate that TXA-mediated plasmin blockade modulates the immune system and reduces surgery-induced immunosuppression in patients following cardiac surgery. TXA enhanced the expression of immune-activating markers while reducing the expression of immunosuppressive markers on multiple myeloid and lymphoid cell populations in peripheral blood. TXA administration significantly reduced postoperative infection rates, despite the fact that patients were being administered prophylactic antibiotics. This effect was independent of the effect of TXA at reducing blood loss. TXA was also shown to exert an immune-modulatory effect in healthy volunteers, further supporting the fibrin-independent effect of TXA on immune function and indicating that baseline plasmin levels contribute to the regulation of the immune system in the absence of any comorbidity or surgical trauma. Finally, the capacity of TXA to reduce infection rates, modulate the innate immune cell profile, and generate an antifibrinolytic effect overall was markedly reduced in patients with diabetes, demonstrating for the first time that the diabetic condition renders patients partially refractory to TXA.

Nitrous oxide and perioperative cardiac morbidity (ENIGMA-II) Trial: rationale and design.

BACKGROUND: Globally there are >200 million major surgical procedures undertaken annually, and about 20% of these involve patients who have coronary artery disease. Many receive nitrous oxide, which impairs methionine synthase, thus inhibiting folate synthesis and increasing postoperative homocysteine levels. Nitrous oxide anesthesia leads to postoperative endothelial dysfunction, and there is some evidence that it increases myocardial ischemia and, possibly, myocardial infarction. We have initiated the Nitrous oxide and perioperative cardiac morbidity (ENIGMA-II) Trial to test the hypothesis that in inpatients undergoing anesthesia for major noncardiac surgery, avoidance of nitrous oxide will reduce the incidence of death and major cardiovascular events. METHODS: ENIGMA-II is a 7,000-patient, international randomized trial involving patients at risk of coronary artery disease undergoing noncardiac surgery. The patients, health care providers (except for the anesthesiologists), data collectors, and outcome adjudicators are blinded to whether patients receive nitrous oxide-containing or nitrous oxide-free anesthetic. The primary outcome is a composite of death and major nonfatal events (ie, myocardial infarction, cardiac arrest, pulmonary embolism, and stroke) at 30 days after surgery. RESULTS: At present, ENIGMA-II has randomized >1,000 patients in 22 hospitals in 5 countries. To date, patients' mean age is 70 years, 66% are men, 38% have a history of coronary artery disease, 19% have a history of cerebrovascular disease, and 84% have a history of hypertension. Most patients have undergone intra-abdominal 28%, vascular 32%, and orthopedic 16% surgery. CONCLUSIONS: The ENIGMA-II Trial will be the largest study yet conducted to ascertain the benefits and risks of removing nitrous oxide from the gas mixture in anesthesia. The results of this large international trial will guide the clinical care of the hundreds of millions of adults undergoing noncardiac surgery annually.