Hermann Heinze

Preoperative Cerebral Oxygen Saturation and Clinical Outcomes in Cardiac Surgery

Background: The current study was designed to determine the relation between preoperative cerebral oxygen saturation (Sco2), variables of cardiopulmonary function, mortality, and morbidity in a heterogeneous cohort of cardiac surgery patients. Methods: In this study, 1,178 consecutive patients scheduled for on-pump surgery were prospectively studied. Preoperative Sco2, demographics, N-terminal pro-B-type natriuretic peptide, high-sensitive troponin T, clinical outcomes, and 30-day and 1-yr mortality were recorded. Results: Median additive EuroSCORE was 5 (range: 0–19). Thirty-day and 1-yr mortality and major morbidity (at least two major complications and/or a high-dependency unit stay of at least 10 days) were 3.5%, 7.7%, and 13.3%, respectively. Median minimal preoperative oxygen supplemented Sco2 (Sco2min-ox) was 64% (range: 15–92%). Sco2min-ox was correlated (all: P value <0.0001) with N-terminal pro-B-type natriuretic peptide (&rgr;: −0.35), high-sensitive troponin T (&rgr;: −0.28), hematocrit (&rgr;: 0.34), glomerular filtration rate (&rgr;: 0.19), EuroSCORE (&tgr;: 0.20), and left ventricular ejection fraction class (&tgr;: 0.12). Thirty-day nonsurvivors had a lower Sco2min-ox than survivors (median 58% [95% CI, 50.7–62%] vs. 64% [95% CI, 64–65%]; P < 0.0001). Receiver-operating curve analysis of Sco2min-ox and 30-day mortality revealed an area-under-the-curve of 0.71 (95% CI, 0.68–0.73%; P < 0.0001) in the total cohort and an area-under-the-curve of 0.77 (95% CI, 0.69–0.86%; P < 0.0001) in patients with a EuroSCORE more than 10. Logistic regression based on different EuroSCORE categories (0–2; 3–5, 6–10, >10), Sco2min-ox, and duration of cardiopulmonary bypass showed that a Sco2min-ox equal or less than 50% is an independent risk factor for 30-day and 1-yr mortality. Conclusions: Preoperative Sco2 levels are reflective of the severity of cardiopulmonary dysfunction, associated with short- and long-term mortality and morbidity, and may add to preoperative risk stratification in patients undergoing cardiac surgery.

Variations in arterial blood pressure are associated with parallel changes in FlowTrac/Vigileo-derived cardiac output measurements: a prospective comparison study.

IntroductionThe reliability of autocalibrated pressure waveform analysis by the FloTrac-Vigileo® (FTV) system for the determination of cardiac output in comparison with intermittent pulmonary arterial thermodilution (IPATD) is controversial. The present prospective comparison study was designed to determine the effects of variations in arterial blood pressure on the reliability of the FTV system in patients undergoing coronary artery bypass grafting (CABG).MethodsComparative measurements of cardiac output by FTV (derived from a femoral arterial line; software version 1.14) and IPATD were performed in 16 patients undergoing elective CABG in the period before institution of cardiopulmonary bypass. Measurements were performed after induction of anesthesia, after sternotomy, and during five time points during graft preparation. During graft preparation, arterial blood pressure was increased stepwise in intervals of 10 to 15 minutes by infusion of noradrenaline and lowered thereafter to baseline levels.ResultsMean arterial blood pressure was varied between 85 mmHg and 115 mmHg. IPATD cardiac output did not show significant changes during periods with increased arterial pressure either during sternotomy or after pharmacological manipulation. In contrast, FTV cardiac output paralleled changes in arterial blood pressure; i.e. increased significantly if blood pressure was raised and decreased upon return to baseline levels. Mean arterial blood pressure (MAP) and FTV cardiac output were closely correlated (r = 0.63 (95% confidence interval [CI]: 0.49 - 0.74), P < 0.0001) while no correlation between MAP and IPATD cardiac output was observed. Bland-Altman analyses for FTV versus IPATD cardiac output measurements revealed a bias of 0.4 l/min (8.5%) and limits of agreement from 2.1 to -1.3 l/min (42.2 to -25.3%).ConclusionsAcute variations in arterial blood pressure alter the reliability of the FlowTrac/Vigileo® device with the second-generation software. This finding may help to explain the variable results of studies comparing the FTV system with other cardiac output monitoring techniques, questions the usefulness of this device for hemodynamic monitoring of patients undergoing rapid changes in arterial blood pressure, and should be kept in mind when using vasopressors during FTV-guided hemodynamic optimization.

The metabolic and renal effects of adrenaline and milrinone in patients with myocardial dysfunction after coronary artery bypass grafting

IntroductionMyocardial dysfunction necessitating inotropic support is a typical complication after on-pump cardiac surgery. This prospective, randomized pilot study analyzes the metabolic and renal effects of the inotropes adrenaline and milrinone in patients needing inotropic support after coronary artery bypass grafting (CABG).MethodsDuring an 18-month period, 251 patients were screened for low cardiac output upon intensive care unit (ICU) admission after elective, isolated CABG surgery. Patients presenting with a cardiac index (CI) of less than 2.2 liters/minute per square meter upon ICU admission – despite adequate mean arterial (titrated with noradrenaline or sodium nitroprusside) and filling pressures – were randomly assigned to 14-hour treatment with adrenaline (n = 7) or milrinone (n = 11) to achieve a CI of greater than 3.0 liters/minute per square meter. Twenty patients not needing inotropes served as controls. Hemodynamics, plasma lactate, pyruvate, glucose, acid-base status, insulin requirements, the urinary excretion of alpha-1-microglobuline, and creatinine clearance were determined during the treatment period, and cystatin-C levels were determined up to 48 hours after surgery (follow-up period).ResultsAfter two to four hours after ICU admission, the target CI was achieved in both intervention groups and maintained during the observation period. Plasma lactate, pyruvate, the lactate/pyruvate ratio, plasma glucose, and insulin doses were higher (p < 0.05) in the adrenaline-treated patients than during milrinone or control conditions. The urinary excretion of alpha-1-microglobuline was higher in the adrenaline than in the control group 6 to 14 hours after admission (p < 0.05). No between-group differences were observed in creatinine clearance, whereas plasma cystatin-C levels were significantly higher in the adrenaline than in the milrinone or the control group after 48 hours (p < 0.05).ConclusionThis suggests that the use of adrenaline for the treatment of postoperative myocardial dysfunction – in contrast to treatment with the PDE-III inhibitor milrinone – is associated with unwarranted metabolic and renal effects.Clinical trials registration: ClinicalTrials.gov NCT00446017.

Lack of agreement between pulmonary arterial thermodilution cardiac output and the pressure recording analytical method in postoperative cardiac surgery patients

BACKGROUND Pulse-contour analysis method (PCM) cardiac output (CO) monitors are increasingly used for CO monitoring during anaesthesia and in the critically ill. Very recently, several systems have been introduced that do not need calibration; among them the pressure recording analytical method (PRAM). Sparse data comparing the accuracy of the PRAM-CO with conventional thermodilution CO (ThD-CO) in cardiac surgery patients are available. METHODS In this prospective comparison study, paired CO measurements with a pulmonary artery catheter and a PRAM monitoring set were obtained 20-30 min apart (t1, t2) in 23 extubated patients on the first postoperative day after cardiac surgery. Data were analysed by the Bland-Altman method. RESULTS A total of 46 paired CO measurements (23 for each interval) were collected. The Bland-Altman analysis showed a mean difference (bias) of 0.0 litre min(-1) and limits of agreement (1.96 sd) of 4.53 to -4.54 litre min(-1) [upper 95% confidence interval (CI), 3.26-5.80; lower 95% CI, -5.8 to -3.27]. The percentage error (1.96 sd/mean of the reference method) was 87%. CONCLUSIONS These results question the reliability of the PRAM technology for the determination of CO in postoperative cardiac surgery patients.

The Accuracy of the Oxygen Washout Technique for Functional Residual Capacity Assessment During Spontaneous Breathing

BACKGROUND:Measurement of functional residual capacity (FRC) is of considerable interest for monitoring patients with lung injury. The lack of instruments has impeded routine bedside FRC measurement. Recently, a simple automated method for FRC assessment by O2 washout has been introduced. We designed this study to evaluate the accuracy of FRC measurement using the O2 washout technique. METHODS:The LUFU system (Draeger, Luebeck, Germany) estimates FRC by O2 washout, a variant of multiple breath nitrogen washout. This technique uses a sidestream O2-analyzer to calculate FRC from end-inspired and end-expired O2 concentrations during fast changes of Fio2. We measured FRC in 23 healthy, spontaneously breathing volunteers in the sitting position using three techniques: 1) helium dilution (FRC-He), 2) body plethysmography (FRC-bp), 3) oxygen washout (FRC-O2). RESULTS:FRC-O2 (mean 4.1 ± 1.1 L, range 2.4–6.9 L) corresponds with FRC-He (mean 4.0 ± 1.0 L, range 2.4–6.2 L; bias of FRC-O2: −0.2 ± 0.4 L) and FRC-bp (mean 4.2 ± 1.0 L, range 2.8–6.1 L; bias of FRC-O2: 0.1 ± 0.6 L). CONCLUSIONS:The bias and precision of the O2 washout technique using the LUFU system were clinically acceptable when compared with FRC-He and FRC-bp for FRC assessment in spontaneously breathing volunteers.

Influence of different electrode belt positions on electrical impedance tomography imaging of regional ventilation: a prospective observational study

BackgroundElectrical impedance tomography (EIT) is a non-invasive bedside tool which allows an individualized ventilator strategy by monitoring tidal ventilation and lung aeration. EIT can be performed at different cranio-caudal thoracic levels, but data are missing about the optimal belt position. The main goal of this prospective observational study was to evaluate the impact of different electrode layers on tidal impedance variation in relation to global volume changes in order to propose a proper belt position for EIT measurements.MethodsEIT measurements were performed in 15 mechanically ventilated intensive care patients with the electrode belt at different thoracic layers (L1-L7). All respiratory and hemodynamic parameters were recorded. Blood gas analyses were obtained once at the beginning of EIT examination. Off-line tidal impedance variation/tidal volume (TV/VT) ratio was calculated, and specific patterns of impedance distribution due to automatic and user-defined adjustment of the colour scale for EIT images were identified.ResultsTV/VT ratio is the highest at L1. It decreases in caudal direction. At L5, the decrease of TV/VT ratio is significant. We could identify patterns of diaphragmatic interference with ventilation-related impedance changes, which owing to the automatically adjusted colour scales are not obvious in the regularly displayed EIT images.ConclusionsThe clinical usability and plausibility of EIT measurements depend on proper belt position, proper impedance visualisation, correct analysis and data interpretation. When EIT is used to estimate global parameters like VT or changes in end-expiratory lung volume, the best electrode plane is between the 4th and 5th intercostal space. The specific colour coding occasionally suppresses user-relevant information, and manual rescaling of images is necessary to visualise this information.

A perioperative infusion of sodium bicarbonate does not improve renal function in cardiac surgery patients: a prospective observational cohort study

IntroductionCardiac-surgery-associated-acute-kidney-injury (CSA-AKI) is associated with increased morbidity and mortality. Recent data from patients undergoing on-pump coronary artery bypass grafting suggest that a perioperative infusion of sodium-bicarbonate may decrease the incidence of CSA-AKI. The present study aims to analyze the renoprotective effects of a 24h infusion of sodium-bicarbonate in a large, heterogeneous group of cardiac surgical patientsMethodsStarting in 4/2009, all patients undergoing cardiac surgery at our institution were enrolled in a prospective trial analyzing the relationship between preoperative cerebral oxygen saturation and postoperative organ dysfunction. We used this prospectively sampled data set to perform a cohort analysis of the renoprotective efficiency of a 24h continuous perioperative infusion of sodium-bicarbonate on the incidence of CSA-AKI that was routinely introduced in 7/2009. After exclusion of patients with endstage chronic kidney disease, off-pump procedures, and emergency cases, perioperative changes in renal function were assessed in 280 patients treated with a perioperative infusion of 4 mmol sodium-bicarbonate / kg body weight in comparison with a control cohort of 304 patients enrolled from April to June in this prospective cohort study.Postoperative changes in urine flow, plasma creatinine, estimated creatinine clearance, and the need for renal replacement therapy were determined according to AKI injury network criteria. Concomitantly, hemodynamics, treatments, complications, and clinical outcomes were recorded. Univariate statistical analyses were performed para- and nonparametrically, as appropriate.ResultsWith the exception of a lower prevalence of a history of myocardial infarction and a lower preoperative use of intravenous heparin in the bicarbonate-group, no significant between group differences in patient demographics, surgical risk, type, and duration of surgery were observed. Patients in the bicarbonate group had a lower mean arterial blood pressure after induction of anesthesia, needed more fluids, more vasopressors, and a longer treatment time in the high dependency unit. Despite a higher postoperative diuresis, no differences in the incidence of AKI grade 1 to 3 and the need for renal replacement were observed.ConclusionsRoutine perioperative administration of sodium bicarbonate failed to improve postoperative renal function in a large population of cardiac surgical patients.

Functional Residual Capacity Changes After Different Endotracheal Suctioning Methods

BACKGROUND:Our primary objective was to investigate the effects of three different endotracheal suctioning procedures on functional residual capacity (FRC). METHODS:Using a crossover design, postoperative cardiac surgery patients (n = 20) received three different suctioning methods in randomized order: closed suctioning during pressure-controlled ventilation, closed suctioning during volume-controlled ventilation, and open suctioning. FRC was measured before and 20 min after the intervention. RESULTS AND CONCLUSIONS:FRC is reduced in postcardiac surgery patients after suctioning, regardless of which method is used. Certain patients may have very pronounced changes of FRC. Routine FRC measurements could complement respiratory monitoring to optimize respiratory therapy.

Functional residual capacity-guided alveolar recruitment strategy after endotracheal suctioning in cardiac surgery patients.

Objective:To determine whether the results of functional residual capacity measurements after endotracheal suctioning could guide the decision to perform an alveolar recruitment maneuver and thus improve lung function. Design:Prospective, randomized, controlled interventional study. Setting:Intensive care unit of a university hospital. Patients:Fifty-nine mechanically ventilated patients within 2 hrs after elective cardiac surgery without preexisting lung diseases. Interventions:Patients received a standard suctioning procedure with disconnection of the ventilator (20 secs, 14 F catheter, 200 cm H2O negative pressure). Prospectively, patients were stratified into two groups by the postsuctioning functional residual capacity value (group A: functional residual capacity >94% of baseline; group B: functional residual capacity <94% of baseline). Both groups were randomized into either a recruitment maneuver (RM) group (positive end-expiratory pressure 15 cm H2O, peak inspiratory pressure 35–40 cm H2O for 30 secs, group RM) or a non-RM group, in which ventilation was resumed without an RM (group NRM), resulting in four groups. Measurements and Main Results:Functional residual capacity and arterial blood gases were recorded for up to 1 hr. In addition, distribution of ventilation was measured by means of electrical impedance tomography. The RM had an impact on distribution of ventilation, functional residual capacity, and oxygenation in patients with a decrease of functional residual capacity after suctioning. In contrast, the RM showed no impact on these parameters in patients with no decrease of functional residual capacity after suctioning. Conclusions:By measurements of functional residual capacity after endotracheal suctioning, patients profiting from a consecutive recruitment maneuver could be identified. Guiding the recruitment strategy on changes of functional residual capacity may improve patient care.

The impact of different step changes of inspiratory fraction of oxygen on functional residual capacity measurements using the oxygen washout technique in ventilated patients.

BACKGROUND:Functional residual capacity (FRC) measurements may help to guide respiratory therapy. Using the oxygen washout technique, FRC can be assessed at bedside during spontaneous breathing. High repeatability, crucial for monitoring, has not been shown in ventilated patients. A large step change of inspiratory fraction of oxygen (Fio2) (&Dgr;Fio2) may impede the clinical use in patients ventilated with high Fio2. We investigated the repeatability of FRC measurements and the impact of different &Dgr;Fio2 on this repeatability. METHODS:The LUFU system (Draeger Medical, Luebeck, Germany) estimates FRC by oxygen washout, a variant of multiple-breath-nitrogen-washout during a fast &Dgr;Fio2. In 20 postoperative cardiac surgery patients, FRC was measured in duplicate using &Dgr;Fio2 of 0.1, 0.2, and 0.6. RESULTS:There were no differences between repeated measurements of FRC, neither using a &Dgr;Fio2 of 0.1, 0.2 nor 0.6(&Dgr;0.1: 2.62 L ± 0.58, 2.62 L ± 0.59, P = 0.995; &Dgr;0.2: 2.70 L ± 0.59, 2.66 L ± 0.56, P = 0.258; &Dgr;0.6: 2.61 L ± 0.58, 2.59 L ± 0.58, P = 0,639). Coefficients of variation were 6.6%, 5.6%, and 6.6%, respectively. CONCLUSIONS:FRC can be measured in ventilated patients using the oxygen washout technique with a clinically acceptable repeatability. Repeatability is not significantly influenced whether using a &Dgr;Fio2 of 0.1, 0.2, or 0.6.