Beneficial effect of aspirin on renal function post-cardiopulmonary bypass

Role of aspirin for prevention and treatment of perioperative cardiovascular events

Among adults undergoing non-cardiac surgery who are at risk of a myocardial infarction, a long-standing question has been whether these patients should receive aspirin throughout the perioperative period. A large (n = 10,010 patients) international trial (POISE-2) demonstrated that perioperative aspirin did not prevent myocardial infarction, and the result was consistent both for patients who had been taking aspirin before the trial (continuation stratum, 4382 patients) and for patients who had not been taking aspirin before the trial (initiation stratum, 5628 patients). Aspirin did, however, increase the risk of major bleeding. Therefore, the best evidence does not support the use of aspirin for the prevention of myocardial infarction in patients undergoing non-cardiac surgery. In patients who have an indication for long-term aspirin usage and have their aspirin held during the perioperative period, it is important to ensure aspirin is restarted after the high-risk period for bleeding has passed (i.e., 8-10 days after surgery).

Aspirin and clonidine in non-cardiac surgery: acute kidney injury substudy protocol of the Perioperative Ischaemic Evaluation (POISE) 2 randomised controlled trial

INTRODUCTION

Perioperative Ischaemic Evaluation-2 (POISE-2) is an international 2×2 factorial randomised controlled trial of low-dose aspirin versus placebo and low-dose clonidine versus placebo in patients who undergo non-cardiac surgery. Perioperative aspirin (and possibly clonidine) may reduce the risk of postoperative acute kidney injury (AKI).

METHODS AND ANALYSIS

After receipt of grant funding, serial postoperative serum creatinine measurements began to be recorded in consecutive patients enrolled at substudy participating centres. With respect to the study schedule, the last of over 6500 substudy patients from 82 centres in 21 countries were randomised in December 2013. The authors will use logistic regression to estimate the adjusted OR of AKI following surgery (compared with the preoperative serum creatinine value, a postoperative increase ≥26.5 μmol/L in the 2 days following surgery or an increase of ≥50% in the 7 days following surgery) comparing each intervention to placebo, and will report the adjusted relative risk reduction. Alternate definitions of AKI will also be considered, as will the outcome of AKI in subgroups defined by the presence of preoperative chronic kidney disease and preoperative chronic aspirin use. At the time of randomisation, a subpopulation agreed to a single measurement of serum creatinine between 3 and 12 months after surgery, and the authors will examine intervention effects on this outcome.

ETHICS AND DISSEMINATION

The authors were competitively awarded a grant from the Canadian Institutes of Health Research for this POISE-2 AKI substudy. Ethics approval was obtained for additional kidney data collection in consecutive patients enrolled at participating centres, which first began for patients enrolled after January 2011. In patients who provided consent, the remaining longer term serum creatinine data will be collected throughout 2014. The results of this study will be reported no later than 2015.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01082874.

Safety and Efficacy Outcomes of Preoperative Aspirin in Patients Undergoing Coronary Artery Bypass Grafting

Background:

The administration of aspirin is traditionally discontinued prior to coronary artery bypass grafting (CABG), given a potential risk of excessive postoperative bleeding. Few studies have previously suggested the benefits of continuing aspirin until the time of surgery. The primary aim of this review is to evaluate the effects of preoperative aspirin therapy on several clinically important outcomes in patients undergoing CABG.

Methods:

A meta-analysis of eligible studies of patients undergoing CABG, reporting preoperative aspirin in comparison with no aspirin/placebo and our outcomes, was carried out. The safety outcomes included postoperative bleeding, packed red blood cell (PRBC) transfusion requirements, and reoperation for bleeding. The efficacy outcomes included perioperative myocardial infarction (MI), cerebrovascular accidents (CVAs), and mortality.

Results:

In 8 randomized controlled trials (RCTs; n = 1538), preoperative aspirin increased postoperative bleeding (difference in means = 132.30 mL; 95 % confidence interval [CI] 47.10-217.51; P = .002), PRBC transfusion requirements (difference in means = 0.67 units; 95% CI 0.10-1.24; P = .02), and reoperation for bleeding (odds ratio [OR] = 1.76; 95% CI 1.05-2.93; P = .03). In 19 observational studies (n = 19551), preoperative aspirin increased postoperative bleeding (difference in means = 132.74 mL; 95% CI 45.77-219.72; P = .003) and PRBC transfusion requirements (difference in means = 0.19 units; 95% CI 0.02-0.35; P = .02) but not reoperation for bleeding (OR = 1.13; 95% CI 0.91-1.42; P = .27). Subgroup analyses for RCTs demonstrated that aspirin given at doses ≤ 100 mg/d might not increase the postoperative bleeding, and the dose of 325 mg/d might not be a cutoff value that has clinical and statistical significance. No statistically significant differences in the rate of perioperative MI, CVAs, or mortality were seen between the 2 groups.

Conclusions:

Preoperative aspirin therapy is associated with increased postoperative bleeding, PRBC transfusion requirements, and reoperation for bleeding in patients undergoing CABG. Doses lower than 100 mg/d may minimize the risk of bleeding. Additional RCTs are needed to assess the effects of preoperative aspirin on the safety and efficacy outcomes in patients undergoing CABG.

Future strategies in the treatment of acute renal failure: growth factors, stem cells, and other novel therapies

PURPOSE OF REVIEW

Acute renal failure remains a significant cause of morbidity and mortality in adults and children. Despite advances in understanding the pathophysiology of acute renal failure, little progress has been made in its treatment. This review assesses the recent data on current and promising new therapies for acute renal failure.

RECENT FINDINGS

The first section of the review describes the recent therapies that have been used in humans, all of whom have been adults. The second section evaluates the use of agents given in experimental animal models during or after the onset of acute renal failure. The third section describes the many animal studies using therapies before the onset of experimental renal failure. The final section discusses how the emerging field of stem cell research might be used to treat acute renal failure.

SUMMARY

Among the recent studies in humans, the most intriguing have been the use of atrial natriuretic peptide in patients with nonoliguric renal failure and isotonic sodium bicarbonate infusions to prevent radiocontrast medium-induced renal failure. Among the agents used in animal studies, those with the greatest potential were hepatocyte growth factor and ethyl pyruvate, because they seem to protect against or accelerate recovery from acute renal failure after the renal insult. Finally, stem cell therapy may someday offer the best option for recovery from acute renal failure.