Intraoperative Hypotension and Acute Kidney Injury, Stroke, and Mortality during and outside Cardiopulmonary Bypass

A Retrospective Observational Cohort Study

Miguel Armengol de la Hoz, M.S.; Valluvan Rangasamy, M.D., D.N.B., D.E.S.A.; Andres Brenes Bastos, M.D., Xinling Xu, Ph.D.; Victor Novack, M.D., Bernd Saugel, M.D.; Balachundhar Subramaniam, M.D., M.P.H., F.A.S.A.

Disclosures

Anesthesiology. 2022;136(6):927-939. 

In This Article

Abstract and Introduction

Abstract

Background: In cardiac surgery, the association between hypotension during specific intraoperative phases or vasopressor-inotropes with adverse outcomes remains unclear. This study's hypothesis was that intraoperative hypotension duration throughout the surgery or when separated into hypotension during and outside cardiopulmonary bypass may be associated with postoperative major adverse events.

Methods: This retrospective observational cohort study included data for adults who had cardiac surgery between 2008 and 2016 in a tertiary hospital. Intraoperative hypotension was defined as mean arterial pressure of less than 65 mmHg. The total duration of hypotension was divided into three categories based on the fraction of overall hypotension duration that occurred during cardiopulmonary bypass (more than 80%, 80 to 60%, and less than 60%). The primary outcome was a composite of stroke, acute kidney injury, or mortality during the index hospitalization. The association with the composite outcome was evaluated for duration of hypotension during the entire surgery, outside cardiopulmonary bypass, and during cardiopulmonary bypass and the fraction of hypotension during cardiopulmonary bypass adjusting for vasopressor-inotrope dose, milrinone dose, patient, and surgical factors.

Results: The composite outcome occurred in 256 (5.1%) of 4,984 included patient records; 66 (1.3%) patients suffered stroke, 125 (2.5%) had acute kidney injury, and 109 (2.2%) died. The primary outcome was associated with total duration of hypotension (adjusted odds ratio, 1.05; 95% CI, 1.02 to 1.08; P = 0.032), hypotension outside cardiopulmonary bypass (adjusted odds ratio, 1.06; 95% CI, 1.03 to 1.10; P = 0.001) per 10-min exposure to mean arterial pressure of less than 65 mmHg, and fraction of hypotension duration during cardiopulmonary bypass of less than 60% (reference greater than 80%; adjusted odds ratio, 1.67; 95% CI, 1.10 to 2.60; P = 0.019) but not with each 10-min period hypotension during cardiopulmonary bypass (adjusted odds ratio, 1.04; 95% CI, 0.99 to 1.09; P = 0.118), fraction of hypotension during cardiopulmonary bypass of 60 to 80% (adjusted odds ratio, 1.45; 95% CI, 0.97 to 2.23; P = 0.082), or total vasopressor-inotrope dose (adjusted odds ratio, 1.00; 95% CI, 1.00 to 1.00; P = 0.247).

Conclusions: This study confirms previous single-center findings that intraoperative hypotension throughout cardiac surgery is associated with an increased risk of acute kidney injury, mortality, or stroke.

Introduction

Postoperative major adverse events frequently occur after cardiac surgery, especially with an increasing number of older and complex patients presenting for cardiac surgical care.[1,2] In patients having noncardiac surgery, intraoperative hypotension is associated with postoperative acute kidney injury (AKI),[3–5] myocardial injury,[4–6] stroke,[7] delirium,[8] and mortality.[9–11] Intraoperative hypotension may also be a modifiable risk factor for major adverse events in patients having cardiac surgery.[3,12–14]

While a mean arterial pressure (MAP) of 65 mmHg has been suggested as a population harm threshold in noncardiac surgery patients,[15] there is no clear consensus regarding an optimal blood pressure intervention threshold during cardiac surgery with cardiopulmonary bypass (CPB).[16] Existing fixed absolute blood pressure values used as lower intervention thresholds during cardiac surgery were chosen based on the principle that cerebral blood flow autoregulation remains functional during CPB.[17,18] However, current evidence suggests that lower limits of autoregulation can vary from 40 to 160 mmHg.[19] Therefore, intraoperative hypotension may be an important modifiable risk factor for major adverse events in patients having cardiac surgery. Recently, intraoperative hypotension (MAP less than 65 mmHg) even for only 11 min during CPB has been shown to increase the risk of stroke.[20]

Clinical observations and hemodynamic monitoring drive various treatments such as crystalloids, colloids, blood products, increasing pump flow, vasopressors, and inotropes during cardiac surgery. The association between organ perfusion and postoperative adverse events is complex but may be better understood when considering intraoperative pharmacologic management in addition to blood pressure. We hypothesized that intraoperative hypotension duration throughout the surgery or when separated into hypotension during and outside CPB may be associated with a composite outcome of postoperative AKI, mortality, and stroke after cardiac surgery.

In this study, we thus aimed to explore the association between (1) intraoperative hypotension (defined as MAP less than 65 mmHg) or (2) the fraction of total intraoperative hypotension occurring during CPB with a composite of three major adverse events (stroke, AKI, and mortality) accounting for intraoperative vasopressor and inotrope dose in patients having cardiac surgery with CPB.

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