Date Published: April 6, 2017
Publisher: Public Library of Science
Author(s): Marco Ranucci, Alberto Porta, Vlasta Bari, Valeria Pistuddi, Maria Teresa La Rovere, Cesario Bianchi.
Postoperative atrial fibrillation, acute kidney dysfunction and low cardiac output following coronary surgery are associated with morbidity and mortality. The purpose of this study is to determine if the preoperative autonomic control is a determinant of these postoperative complications. This is a prospective cohort study on 150 adult patients undergoing surgical coronary revascularization with cardiopulmonary bypass. The patients received an autonomic control assessment after the induction of anesthesia. Baroreflex sensitivity was computed by spectral analysis and expressed as BRSαHF and BRSαLF for measure respectively in the high and low frequency domains. Atrial fibrillation was adjudicated at any postoperative time during the hospital stay. Acute kidney dysfunction was defined as any increase of serum creatinine levels from preoperative values within the first 48 hours after surgery, and acute kidney injury was adjudicated at a 50% increase. Low cardiac ouput syndrome was defined as the need for inotropic support > 48 hours. Thirty-eight (26.4%) patients experienced postoperative atrial fibrillation; 32 (22.2%) had acute kidney dysfunction and 5 (3.5%) acute kidney injury; 14(10%) had a low cardiac output state. No indices of baroreflex sensitivity were associated with atrial fibrillation or acute kidney injury. A low value of BRSαLF was associated with acute kidney dysfunction and low cardiac output state. A BRSαLF < 3 msec/mmHg was an independent risk factor for acute kidney dysfunction (odds ratio 3.0, 95% confidence interval 1.02–8.8, P = 0.045) and of low cardiac output state (odds ratio 17.0, 95% confidence interval 2.9–99, P = 0.002). Preoperative baroreflex sensitivity is linked to postoperative complications through a number of possible mechanisms, including an autonomic nervous system-mediated vasoconstriction, a poor response to hypotension, and an increased inflammatory reaction.
The arterial baroreflex is an important determinant of the neural regulation of the cardiovascular system. A reduction in the baroreceptor-heart rate reflex (i.e., baroreflex sensitivity, BRS), has been reported in hypertension, coronary artery disease, myocardial infarction and heart failure.  The majority of the studies have shown that lower BRS values are associated with higher cardiovascular disease-related mortality. [2–4] More specifically, it has been recently suggested that a cut-off value around 3 ms/mmHg—a threshold rather constant through different methodologies—can be viewed as a biological threshold for the functioning of the baroreflex. [2, 5]
Prospective cohort study performed according to the declaration of Helsinki. The study design was approved by the Local Ethics Committee (Ethics Committee San Raffaele Hospital, Milan). All the patients gave a written informed consent.
The general characteristics of the patients population are depicted in Tables 1 and 2. Out of the 150 patients enrolled, autonomic control parameters were computed in 144 patients who constituted the study population. In the remaining 6 patients it was not possible to extract the variability indices due to frequent arrhythmias or bad arterial pressure recording. Thirty-eight (26.4%) patients experienced at least one episode of postoperative AF, and 14 (9.7%) a LCOS, whereas 32 (22.2%) fulfilled the criteria for AKD and 7 (4.8%) those for AKI. Patients with AKD had a significantly lower hematocrit and higher EuroSCORE II; they experienced a longer mechanical ventilation time and ICU stay; patients with AKI had the same profile plus a significantly smaller weight.
The main results of our study are: (i) BRS as determined by the αHF is not associated with any of the considered outcomes, (ii) conversely, the BRSαLF is an independent predictor of AKD and LCOS, and (iii) postoperative AF is not associated with preoperative measures of BRS.