111,825 research outputs found
Cardiac surgery associated acute kidney injury and the role of cardiopulmonary bypass technique
No full textDiscrimination and calibration properties of the hypotension probability indicator during cardiac and vascular surgery
No full textBACKGROUND: Hypotension during surgery is linked to postoperative complications. Recently, a new hemodynamic algorithm intended to predict hypotensive events (hypotension probability indicator [HPI]) has been developed. The aim of the present study is to test the discrimination and calibration properties of the HPI. METHODS: The intraoperative files of 23 patients undergoing cardiac and major vascular surgery receiving the HPI-based hemodynamic monitoring were retrospectively investigated for prediction of hypotensive events (mean arterial pressure <65 mmHg). The HPI was available at 20 seconds intervals; the values of HPI five to seven minutes before a hypotensive event (HPI5-7) were tested for discrimination and calibration. RESULTS: The HPI5-7 has a fair level of discrimination (area under the curve 0.768) and a poor calibration, due to overestimation of the hypotensive risk. At the observed prevalence, a cut-off value of 85% carries a sensitivity of 62.4% and a specificity of 77.7%, a negative predictive value (NPV) of 97.8% and a positive predictive value (PPV) of 12.6%; a value of 98% has a PPV of 64% and an NPV of 95.3%. CONCLUSIONS: The HPI5-7 may offer some useful insights. Values ≤85% carry a clinically acceptable NPV for hypotensive events at the observed prevalence and may represent a “safe zone” during surgery. Values >85% do not carry enough PPV to trigger hemodynamic interventions, but represent a warning signal. Values >98% are highly suggesting a hypotensive event after 5-7 minutes. Further studies exploring the predictive ability of the HPI at different times are needed
General anesthesia reduces the information exchange between heart and circulation
No full textThe study demonstrates the ability of an information-theoretic measure, such as the transfer entropy (TE), in detecting the depression of the cardiac baroreflex control and circulatory-cardio mechanical feedforward link during propofol-induced general anesthesia. TE was computed from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) in patients undergoing coronary artery bypass graft (CABG). TE from SAP to HP and from HP to SAP were evaluated by accounting for the confounding effect of respiration (R) affecting both HP and SAP (i.e. TESAP→HP-R and TEHP→SAP-R respectively). Both TESAP→HP-R and TEHP→SAP-R decreased during general anesthesia, thus suggesting that the strength of the causal relation diminished over both arms of the closed loop HP-SAP control. The squared coherence function between HP and SAP confirmed the decreased HP-SAP coupling during general anesthesia, even though it could not distinguish directionality
Model-based directional analysis of cardiovascular variability identifies patients developing atrial fibrillation after coronary artery bypass grafting
No full textBackground: Postoperative atrial fibrillation (AF) might be favored by cardiovascular control impairment. We hypothesize that cardiovascular regulation indexes derived from directional model-based analysis of the spontaneous fluctuations of heart period (HP) and systolic arterial pressure (SAP) can identify subjects at risk to develop AF after coronary artery bypass graft (CABG) surgery.
Methods: Beat-to-beat HP and SAP series were derived from electrocardiogram (ECG) and invasive arterial pressure recorded for 5 min just before CABG surgery in conscious condition. The group comprised subjects who did develop AF (AF, n = 37, 71 ± 8 years, 27 males) or did not (noAF, n = 92, 65 ± 10 years, 85 males). From HP and SAP variabilities we computed classical time-domain, spectral, cross-spectral and complexity indexes characterizing autonomic function and cardiac baroreflex control. Moreover, we performed model-based directional analysis assessing the gain and strength of the relations from SAP to HP along cardiac baroreflex feedback and from HP to SAP along the feedforward pathway while disambiguating the effect of respiration as estimated from respiratory-related ECG modulations.
Results: Classical HP and SAP variability indexes and baroreflex sensitivity could not separate AF from noAF individuals. Causality markers, and more specifically, the strength of the dynamical interactions from SAP to HP and vice versa, could distinguish the two groups: indeed, AFs have a lower degree of association from SAP to HP and vice versa.
Conclusions: An impairment of the feedforward and feedback arms of the HP-SAP closed loop relation predisposes subjects undergoing CABG surgery to develop postoperative AF.
Perspectives: Competency in medical knowledge: Atrialfibrillation (AF) is a frequent complication after coronary artery bypass graft (CABG) surgery lengthening hospitalization duration and increasing healthcare system costs.
Translational outlook 1: CABG patients who developed AF had a less preserved cardiovascular interactions due to less active physiological control mechanisms as resulting from the lower degree of dependence of systolic arterial pressure on heart period and vice versa before CABG surgery.
Translational outlook 2: Cardiovascular control markers improve stratification of the AF risk after CABG surgery above and beyond more traditional demographic and clinical indexes
Stratifying the risk of developing atrial fibrillation after coronary artery bypass graft surgery using heart rate asymmetry indexes
No full textHeart period (HP) asymmetry (HPA) is a peculiar pattern detectable over short-term HP variability recordings suggesting that cardiac deceleration runs are shorter than acceleration ones in healthy subjects. We tested the hypothesis that two traditional HPA indexes, namely the Porta's index (PI) and Guzik's index (GI), can distinguish patients scheduled for coronary artery bypass graft (CABG) surgery developing atrial fibrillation (AF) after surgery from the ones who do not (noAF). HP was derived from the electrocardiogram in 130 patients scheduled for CABG before (PRE) and after (POST) the induction of general anesthesia. PI assesses the percentage of positive HP changes, while GI quantifies the percent sum of the squared positive variations. Positive departures from 50 suggest that a series exhibits HPA. Surrogate analysis was exploited to assess the significant presence of HPA patterns. The likelihood of detecting HPA patters was higher in AF subjects and this result held during PRE. GI featured a greater statistical power than PI. Neither HP mean nor variance distinguished the two groups. HPA indexes can be exploited to improve stratification of the risk for post-surgery AF
Empirical mode decomposition approach to the estimation of cardiac baroreflex sensitivity in patients undergoing coronary artery bypass graft surgery
No full textCardiac baroreflex sensitivity (BRS) as assessed from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) is reduced during general anesthesia. Patients undergoing coronary artery bypass graft (CABG) surgery are characterized by a low BRS even before general anesthesia. These observations provide the basis of the difficulty in detecting the BRS reduction after the induction of general anesthesia in CABG patients. Empirical mode decomposition (EMD) is a technique decomposing the series into oscillatory modes at different time scales. We propose an EMD-based approach to the BRS estimate in 34 patients undergoing CABG. Results showed that the EMD-based method was not able to detect the BRS reduction in CABG patients after the induction of general anesthesia. The negative result was interpreted as a consequence of the inability of EMD-based method to account for HP-SAP causality
Towards the identification of subjects prone to develop atrial fibrillation after coronary artery bypass graft surgery via univariate and multivariate complexity analysis of heart period variability
No full textThe assessment of cardiovascular control complexity as derived from spontaneous heart period (HP) fluctuations can be improved by exploiting a multivariate (MV) approach. This work proposes the assessment of a normalized complexity index (NCI) of HP variability according to a k-nearest-neighbor approach based on local predictability performed in a MV nonuniform embedding space. The method allows the selection of the past components of HP, systolic arterial pressure (SAP) and respiration (R) most useful for the prediction of HP fluctuations. The NCI derived from the MV approach (NCIMV) was compared to a NCI computed via the same technique applied in a univariate (UV) embedding space (NCIUV) formed exclusively by HP past samples. Indexes were computed in 130 patients undergoing coronary artery bypass graft (CABG) surgery before and after the induction of general anesthesia. Thirty-eight subjects developed atrial fibrillation (AF) after surgery, while the remaining ones did not (noAF, n=92). Both NCIUV and NCIMV could separate AF from noAF patients and revealed a larger complexity of the AF subjects. However, the statistical power of the NCIMV was superior given that the probability of type I error was smaller than that of NCIUV. The assessment of cardiac control complexity could improve risk stratification of patients at risk of developing AF after CABG surgery
Model-based causal closed loop approach to the estimate of baroreflex sensitivity during propofol anesthesia in patients undergoing coronary artery bypass graft
No full textCardiac baroreflex is a fundamental component of the cardiovascular control. The continuous assessment of baroreflex sensitivity (BRS) from spontaneous heart period (HP) and systolic arterial pressure (SAP) variations during general anesthesia provides relevant information about cardiovascular regulation in physiological conditions. Unfortunately, several difficulties including unknown HP-SAP causal relations, negligible SAP changes, small BRS values, and confounding influences due to mechanical ventilation prevent BRS monitoring from HP and SAP variabilities during general anesthesia. We applied a model-based causal closed-loop approach aiming at BRS assessment during propofol anesthesia in 34 patients undergoing coronary artery bypass graft (CABG) surgery. We found the following: 1) traditional time and frequency domain approaches (i.e., baroreflex sequence, cross-correlation, spectral, and transfer function techniques) exhibited irremediable methodological limitations preventing the assessment of the BRS decrease during propofol anesthesia; 2) Granger causality approach proved that the methodological caveats were linked to the decreased presence of bidirectional closed-loop HP-SAP interactions and to the increased incidence of the HP-SAP uncoupling; 3) our model-based closed-loop approach detected the significant BRS decrease during propofol anesthesia as a likely result of accounting for the influences of mechanical ventilation and causal HP-SAP interactions; and 4) the model-based closed-loop approach found also a diminished gain of the relation from HP to SAP linked to vasodilatation and reduced ventricular contractility during propofol anesthesia. The proposed model-based causal closed-loop approach is more effective than traditional approaches in monitoring cardiovascular control during propofol anesthesia and indicates an overall depression of the HPSAP closed-loop regulation. Copyrigh
Cardiovascular interactions assessed via conditional joint transfer entropy in patients developing atrial fibrillation after coronary artery bypass graft surgery
No full textAssigned the universe of knowledge Ω as composed by one target and two exogenous signals, the conditional joint transfer entropy (CJTE), assessing the amount of information jointly transferred from the two sources to the target that can be uniquely linked to one of the two sources, was found useful to study cardiovascular control. We propose the assessment of CJTE from systolic arterial pressure (SAP) and respiration (R) to heart period (HP) conditioned on R (CJTESAP, R→HPR) along the baroreflex, and from HP and R to SAP conditioned on R (CJTEHP, R→SAPR) along the feedforward mechanical pathway, in 134 patients undergoing coronary artery bypass graft surgery before (PRE) and after (POST) the induction of general anesthesia. In this group 38 patients developed atrial fibrillation (AF) after surgery, while the remaining individuals did not (noAF, n=96). Both CJTESAP, R→HPR and CJTEHP, R→SAPR distinguished AF from noAF individuals in the PRE condition, suggesting an impairment of HP-SAP closed-loop regulation in AF group and the possibility to identify subjects at higher risk to develop post-surgery AF
Baroreflex sensitivity and outcomes following coronary surgery.
Get PDFPostoperative 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
- …
