title: ICU Blood Pressure Variability May Predict Nadir of Respiratory Depression After Coronary Artery Bypass Surgery.
abstract: OBJECTIVE
  Surgical stress induces alterations on sympathovagal balance that can be determined through assessment of blood pressure variability. Coronary artery bypass graft surgery (CABG) is associated with postoperative respiratory depression. In this study we aimed at investigating ICU blood pressure variability and other perioperative parameters that could predict the nadir of postoperative respiratory function impairment.
  
  
  METHODS
  This prospective observational study evaluated 44 coronary artery disease patients subjected to coronary artery bypass surgery (CABG) with cardiopulmonary bypass (CPB). At the ICU, mean arterial pressure (MAP) was monitored every 30 min for 3 days. MAP variability was evaluated through: standard deviation (SD), coefficient of variation (CV), variation independent of mean (VIM), and average successive variability (ASV). Respiratory function was assessed through maximal inspiratory (MIP) and expiratory (MEP) pressures and peak expiratory flow (PEF) determined 1 day before surgery and on the postoperative days 3rd to 7th. Intraoperative parameters (volume of cardioplegia, CPB duration, aortic cross-clamp time, number of grafts) were also monitored.
  
  
  RESULTS
  Since, we aimed at studying patients without confounding effects of postoperative complications on respiratory function, we had enrolled a cohort of low risk EuroSCORE (European System for Cardiac Operative Risk Evaluation) with < 2. Respiratory parameters MIP, MEP, and PEF were significantly depressed for 4-5 days postoperatively. Of all MAP variability parameters, the ASV had a significant good positive Spearman correlation (rho coefficients ranging from 0.45 to 0.65, p < 0.01) with the 3-day nadir of PEF after cardiac surgery. Also, CV and VIM of MAP were significantly associated with nadir days of MEP and PEF. None of the intraoperative parameters had any correlation with the postoperative respiratory depression.
  
  
  CONCLUSIONS
  Variability parameters ASV, CV, and VIM of the MAP monitored at ICU may have predictive value for the depression of respiratory function after cardiac surgery as determined by peak expiratory flow and maximal expiratory pressure. ClinicalTrials.gov Identifier: NCT02074371.
authors.affiliation: Center of Innovation, Technology and Education, Camilo Castelo Branco UniversitySao Jose dos Campos, Brazil; Health Sciences Center, State University of PiauiTeresina, Brazil.
authors.forename: Anne S M
authors.initials: AS
authors.lastname: Costa
authors.affiliation: Hospital Sao Marcos Teresina, Brazil.
authors.forename: Paulo H M
authors.initials: PH
authors.lastname: Costa
authors.affiliation: Hospital Sao MarcosTeresina, Brazil; Health Sciences Center, Federal University of PiauiTeresina, Brazil.
authors.forename: Carlos E B
authors.initials: CE
authors.lastname: de Lima
authors.affiliation: Health Sciences Center, Federal University of Piaui Teresina, Brazil.
authors.forename: Luiz E M
authors.initials: LE
authors.lastname: Pádua
authors.affiliation: Center of Innovation, Technology and Education, Camilo Castelo Branco University Sao Jose dos Campos, Brazil.
authors.forename: Luciana A
authors.initials: LA
authors.lastname: Campos
authors.affiliation: Center of Innovation, Technology and Education, Camilo Castelo Branco University Sao Jose dos Campos, Brazil.
authors.forename: Ovidiu C
authors.initials: OC
authors.lastname: Baltatu
keywords: CABG; ICU; autonomic nervous system; blood pressure variability; perioperative parameters; respiratory function