AKI associated with cardiac surgery

Relationship between a perioperative intravenous fluid administration strategy and acute kidney injury following off-pump coronary artery bypass surgery: an observational study

INTRODUCTION

Saline-based and hydroxyethyl starch solutions are associated with increased risk of renal dysfunction. In the present study, we tested the hypothesis that balanced solutions and a limited volume of hydroxyethyl starch solution (renal protective fluid management [RPF] strategy) would decrease the incidence of postoperative acute kidney injury (AKI) and improve clinical outcomes in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB).

METHODS

We investigated 783 patients who underwent elective OPCAB. All patients who underwent OPCAB between 1 January 2010 and 4 July 2012 formed the control group and were given intravenous fluids with saline-based solutions and unlimited volumes of colloid solutions. All patients who underwent OPCAB between 5 July 2012 and 31 December 2013 formed the RPF group and were given intravenous fluids with RPF. The primary outcome was the incidence of postoperative AKI. Secondary outcomes included the incidence of severe AKI, requirement for renal replacement therapy, renal outcome at the time of discharge, and other clinical outcomes.

RESULTS

Postoperative AKI occurred in 33 patients (14.4 %) in the RPF group compared with 210 patients (37.9 %) in the control group (P < 0.001). The incidences of severe AKI and persistent AKI after OPCAB were significantly lower, and the postoperative extubation time and duration of hospital stay were significantly shorter, in patients in the RPF group than in those in the control group. After adjustment by multivariate regression analyses and inverse probability of treatment weighting adjustment, the RPF group was independently associated with a lower incidence of postoperative AKI, severe AKI, and persistent AKI and a shorter postoperative extubation time and duration of hospital stay.

CONCLUSIONS

The RPF strategy is associated with a significantly decreased incidence of postoperative, severe, and persistent AKI in patients undergoing OPCAB, although residual confounding may be present.

Intraoperative hypotension - a neglected causative factor in hospital-acquired acute kidney injury; a Mayo Clinic Health System experience revisited

Acute kidney injury (AKI) is a relatively common complication of cardiothoracic surgery and has both short- and long-term survival implications, even when AKI does not progress to severe renal failure. Given that currently, there are no active effective treatments for AKI, other than renal replacement therapy when indicated, the focus of clinicians ought to be on prevention and risk factor management. In the AKI-surgery literature, there exists this general consensus that intraoperative hypotension (IH) following hypotensive anesthesia (HA) or controlled hypotension (CH) in the operating room has no significant short-term and long-term impacts on renal function. In this review, we examine the basis for this consensus, exposing some of the flaws of the clinical study data upon which this prevailing consensus is based. We then describe our experiences in the last decade at the Mayo Clinic Health System, Eau Claire, in Northwestern Wisconsin, USA, with two selected case presentations to highlight the contribution of IH as a potent yet preventable cause of post-operative AKI. We further highlight the causative although neglected role of IH in precipitating postoperative AKI in chronic kidney disease (CKD) patients. We show additional risk factors associated with this syndrome and further make a strong case for the elimination of IH as an achievable mechanism to reduce overall, the incidence of hospital acquired AKI. We finally posit that as the old saying goes, prevention is indeed better than cure.

Severe acute kidney injury following cardiac surgery: short-term outcomes in patients undergoing continuous renal replacement therapy (CRRT)

BACKGROUND

Acute kidney injury (AKI) represents a major complication of cardiac surgery. Our aim was to evaluate, in patients undergoing continuous renal replacement therapy (CRRT) for cardiac surgery-associated AKI (CS-AKI), prognostic factors related to in-hospital survival and renal function recovery to independence from RRT.

METHODS

We conducted a retrospective analysis in patients with severe CS-AKI who underwent CRRT for at least 48 h. The sequential organ failure assessment (SOFA) score was calculated on a daily basis to evaluate illness severity throughout the intensive care unit (ICU) stay.

RESULTS

In 264 patients (age 66.4 ± 11.7 years, 192 males), 30-day survival was 57.6 % while survival to discharge from the hospital was 40.5 %. Renal function recovery occurred in 96.3 % of survivors and in 13.4 % of non-survivors (p < 0.001). Multivariate analysis selected advancing age, oliguria, sepsis and the highest level of SOFA score within the first week of CRRT (SOFA-max) as independent prognostic factors for failure to recover renal function. Female gender was associated with a higher probability of survival, while higher serum creatinine at the start of CRRT, oliguria, sepsis and SOFA-max were independently associated with mortality. The subgroup of patients with a day-1 SOFA score above the median (≥10) showed a lower probability of survival and a lower cumulative incidence of renal function recovery.

CONCLUSIONS

In a selected population of patients with severe CS-AKI requiring RRT, short-term outcomes appear strongly associated with the worst grade of illness severity during the first week of CRRT, thus reflecting the sequential occurrence of additional major complications during ICU stay. Renal function recovery and in-hospital survival appear mutually linked, sharing oliguria, sepsis and SOFA score as the main determinants of both outcomes.