Defining an Intraoperative Hypotension Threshold in Association withDe NovoRenal Replacement Therapy after Cardiac Surgery

Abstract

Background Acute kidney injury (AKI) is a frequent and deadly complication after cardiac surgery. In the absence of effective therapies, a focus on risk factor identification and modification has been the mainstay of management. The authors sought to determine the impact of intraoperative hypotension on de novo postoperative renal replacement therapy in patients undergoing cardiac surgery, hypothesizing that prolonged periods of hypotension during and after cardiopulmonary bypass (CPB) were associated with an increased risk of renal replacement therapy. Methods Included in this single-center retrospective cohort study were adult patients who underwent cardiac surgery requiring CPB between November 2009 and April 2015. Excluded were patients who were dialysis dependent, underwent thoracic aorta or off-pump procedures, or died before receiving renal replacement therapy. Degrees of hypotension were defined by mean arterial pressure (MAP) as less than 55, 55 to 64, and 65 to 74 mmHg before, during, and after CPB. The primary outcome was de novo renal replacement therapy. Results Of 6,523 patient records, 336 (5.2%) required new postoperative renal replacement therapy. Each 10-min epoch of MAP less than 55 mmHg post-CPB was associated with an adjusted odds ratio of 1.13 (95% CI, 1.05 to 1.23; P = 0.002), and each 10-min epoch of MAP between 55 and 64 mmHg post-CPB was associated with an adjusted odds ratio of 1.12 (95% CI, 1.06 to 1.18; P = 0.0001) for renal replacement therapy. The authors did not observe an association between hypotension before and during CPB with renal replacement therapy. Conclusions MAP less than 65 mmHg for 10 min or more post-CPB is associated with an increased risk of de novo postoperative renal replacement therapy. The association between intraoperative hypotension and AKI was weaker in comparison to factors such as renal insufficiency, heart failure, obesity, anemia, complex or emergent surgery, and new-onset postoperative atrial fibrillation. Nonetheless, post-CPB hypotension is a potentially easier modifiable risk factor that warrants further investigation. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Society of Cardiovascular Anesthesiologists Clinical Practice Update for Management of Acute Kidney Injury Associated With Cardiac Surgery

“…Intraoperative Target Blood Pressure A recent retrospective study showed that MAP <65 mm Hg for 10 minutes or more after CPB was associated with an increased risk of new postoperative RRT. 26 However, there was no association between hypotension before and during CPB with RRT in this study. 26 In addition, the association between intraoperative hypotension and AKI was not strong, when compared with preexisting and procedure-related factors, such as obesity, anemia, renal insufficiency, heart failure, and complex or emergent surgery.…”

The burden of perioperative hypertension/hypotension: A systematic review

“…There were two works investigating these outcomes in cardiac surgery and it was seen that an area under the curve (AUC) below the optimal BP as well as MAP below 65 mmHg were associated with increased odds of developing AKI and requiring de novo renal replacement therapy, respectively. For de novo renal replacement therapy higher odds were reported with lower values of MAP [ 27 , 49 ]. In non-cardiac surgeries an increase of 1.51 odds was associated with a 10% decrease in MAP [ 46 ], while other authors demonstrated a cumulative effect of HPT over time, for example Salmasi et al .…”

Renal failure in cardiac surgery: in search of the magic bullet

“…Studies have been performed trying to reduce hypoperfusion with higher limits for mean arterial pressure (MAP) during cardiopulmonary bypass, but with little effect [13]. Despite this, Ngu et al recently showed that hypotension post-cardiopulmonary bypass for an extended time-period is associated with an increased risk of de-novo postoperative renal replacement therapy [14]. They found that MAP < 65 mmHg for over 10 min postoperatively was associated with the requirement for renal replacement therapy (adjusted odds ratio of 1.12 (95%CI 1.06-1.18)).…”