Post-cardiac Surgery Intensive Care Research Articles

Machine learning in cardiac surgery: a narrative review.

Machine learning (ML) is increasingly being utilized to provide data driven solutions to challenges in medicine. Within the field of cardiac surgery, ML methods have been employed as risk stratification tools to predict a variety of operative outcomes. However, the clinical utility of ML in this domain is unclear. The aim of this review is to provide an overview of ML in cardiac surgery, particularly with regards to its utility in predictive analytics and implications for use in clinical decision support. We performed a narrative review of relevant articles indexed in PubMed since 2000 using the MeSH terms "Machine Learning", "Supervised Machine Learning", "Deep Learning", or "Artificial Intelligence" and "Cardiovascular Surgery" or "Thoracic Surgery". ML methods have been widely used to generate pre-operative risk profiles, consistently resulting in the accurate prediction of clinical outcomes in cardiac surgery. However, improvement in predictive performance over traditional risk metrics has proven modest and current applications in the clinical setting remain limited. Studies utilizing high volume, multidimensional data such as that derived from electronic health record (EHR) data appear to best demonstrate the advantages of ML methods. Models trained on post cardiac surgery intensive care unit data demonstrate excellent predictive performance and may provide greater clinical utility if incorporated as clinical decision support tools. Further development of ML models and their integration into EHR's may result in dynamic clinical decision support strategies capable of informing clinical care and improving outcomes in cardiac surgery.

Agreement between cardiac output estimation with a wireless, wearable pulse decomposition analysis device and continuous thermodilution in post cardiac surgery intensive care unit patients.

Pulse Decomposition Analysis (PDA) uses integration of the systolic area of a distally transmitted aortic pulse as well as arterial stiffness estimates to compute cardiac output. We sought to assess agreement of cardiac output (CO) estimation between continuous pulmonary artery catheter (PAC) guided thermodilution (CO-CCO) and a wireless, wearable noninvasive device, (Vitalstream, Caretaker Medical, Charlottesville, VA), that utilizes the Pulse Decomposition Analysis (CO-PDA) method in postoperative cardiac surgery patients in the intensive care unit. CO-CCO measurements were compared with post processed CO-PDA measurements in prospectively enrolled adult cardiac surgical intensive care unit patients. Uncalibrated CO-PDA values were compared for accuracy with CO-CCO via a Bland-Altman analysis considering repeated measurements and a concordance analysis with a 10% exclusion zone. 259.7h of monitoring data from 41 patients matching 15,583 data points were analyzed. Mean CO-CCO was 5.55L/min, while mean values for the CO-PDA were 5.73L/min (mean of differences +- SD 0.79 ± 1.11L/min; limits of agreement - 1.43 to 3.01L/min), with a percentage error of 37.5%. CO-CCO correlation with CO-PDA was moderate (0.54) and concordance was 0.83. Compared with the CO-CCO Swan-Ganz, cardiac output measurements obtained using the CO-PDA were not interchangeable when using a 30% threshold. These preliminary results were within the 45% limits for minimally invasive devices, and pending further robust trials, the CO-PDA offers a noninvasive, wireless solution to complement and extend hemodynamic monitoring within and outside the ICU.

Agreement between cardiac output estimation by multi-beat analysis of arterial blood pressure waveforms and continuous thermodilution in post cardiac surgery intensive care unit patients

We sought to assess agreement of cardiac output estimation between continuous pulmonary artery catheter (PAC) guided thermodilution (CO-CTD) and a novel pulse wave analysis (PWA) method that performs an analysis of multiple beats of the arterial blood pressure waveform (CO-MBA) in post-operative cardiac surgery patients. PAC obtained CO-CTD measurements were compared with CO-MBA measurements from the Argos monitor (Retia Medical; Valhalla, NY, USA), in prospectively enrolled adult cardiac surgical intensive care unit patients. Agreement was assessed via Bland-Altman analysis. Subgroup analysis was performed on data segments identified as arrhythmia, or with low CO (less than 5 L/min). 927 hours of monitoring data from 79 patients was analyzed, of which 26 had arrhythmia. Mean CO-CTD was 5.29 ± 1.14 L/min (bias ± precision), whereas mean CO-MBA was 5.36 ± 1.33 L/min, (4.95 ± 0.80 L/min and 5.04 ± 1.07 L/min in the arrhythmia subgroup). Mean of differences was 0.04 ± 1.04 L/min with an error of 38.2%. In the arrhythmia subgroup, mean of differences was 0.14 ± 0.90 L/min with an error of 35.4%. In the low CO subgroup, mean of differences was 0.26 ± 0.89 L/min with an error of 40.4%. In adult patients after cardiac surgery, including those with low cardiac output and arrhythmia CO-MBA is not interchangeable with the continuous thermodilution method via a PAC, when using a 30% error threshold.

Utility of Transfontanelle Ultrasound in Predicting the Fluid Responsiveness in Children After Repair of Congenital Heart Diseases: A Prospective Observational Study

Postoperative fluid management in children undergoing cardiac surgery requires a balanced optimization. The blood flow velocity variation in the internal carotid artery (ΔICA) measured through transfontanelle ultrasound has been shown to predict fluid responsiveness during cardiac surgery. It may provide an excellent window to study fluid responsiveness in infants during the postoperative period when the intensivist is faced with the challenges of poor echocardiographic window. The authors aimed to observe the correlation between ΔICA measured on transfontanelle ultrasound with the respiratory variability of peak aortic blood flow velocity (ΔVpeak) on transthoracic echocardiography as a marker of fluid responsiveness in infants on mechanical ventilation during the postoperative period after cardiac surgery. A prospective observational study. The postcardiac surgery intensive care unit (ICU) of a tertiary care hospital. Thirty infants undergoing congenital cardiac surgery. A fluid bolus of 10 mL/kg administered over 10 minutes at 1 and 6 hours after ICU admission. Patients were categorized into fluid responders and nonresponders based on >15% increase in the indexed stroke volume. A total of 50 fluid boluses were administered in 30 patients. Among these, 22 (73.33%) were responders and 8 (26.67%) were nonresponders. There was moderate correlation between ΔICA and peak aortic blood flow velocity variation (ΔVpeak) (r=0.59, p ≤ 0.001). The ΔVpeak >14.74% had 68% sensitivity and 75% specificity to predict fluid responsiveness (area under the receiver operating characteristic [AUROC], 0.749; p=0.001; positive likelihood ratio, 2.71; negative likelihood ratio, 0.43). The ΔICA >9.85% could predict fluid responsiveness in infants (AUROC, 0.728; p=0.003; 75% sensitivity; 60% specificity; positive likelihood ratio, 1.85; negative likelihood ratio, 0.42). Among children younger than 6 months, ΔICA >9.85% was a better predictor of fluid responsiveness (AUROC, 0.889; p=0.009) than ΔVpeak >15% (AUROC, 0.778; p=0.061). The ICA variability >9.85% measured via transfontanelle ultrasound is a good predictor of fluid responsiveness in infants, especially those younger than 6 months on mechanical ventilation after cardiac surgery.

Cardiac Safety of Clonidine and Quetiapine in Post-Cardiac Surgery Intensive Care Unit Patients

Background: Clonidine and quetiapine are frequently used medications in the cardiac surgery intensive care unit (ICU). Objective: The purpose of this study is to assess the impact of clonidine compared to quetiapine on cardiac safety outcomes in adult cardiac surgery ICU patients. Methods: This was a single-center, retrospective observational analysis at a tertiary care, academic medical center. Results: One hundred and sixty-one cardiac surgery patients who were administered clonidine or quetiapine during their ICU stay were included between June 2015 and May 2017. The major endpoint of this study was a cardiac safety composite of bradycardia, hypotension, and QTc prolongation. Minor endpoints included ICU and hospital length of stay, and in-hospital mortality. There were 115 patients included in the clonidine arm and 46 patients in the quetiapine arm. There was no difference between groups with regard to the major endpoint (30.43% vs 33.15%; P < .8). There was a shorter ICU and hospital length of stay in the clonidine arm compared to quetiapine P < .0001. All other endpoints were not statistically significant. Conclusion: Patients who received clonidine tended to have undergone less complex procedures, be younger, and have a lower APACHE II score than patients who received quetiapine. The incidence of composite cardiac safety outcomes was not different in clonidine compared to quetiapine in cardiac surgery ICU patients.

Effect of High-Flow Nasal Oxygen on Respiratory Parameters and Pulmonary Complications After Early Extubation Following Pediatric Heart Surgery

Objectives: The aim of this study was to evaluate the effect of high-flow nasal cannula (HFNC) after early extubation on children undergoing cardiac surgery. Methods: This randomized controlled clinical trial was performed among 92 children aged 1 to 24 months undergoing cardiac surgery from March 5 to August 30, 2020, in a pediatric post-cardiac surgery intensive care unit (ICU). The patients were randomized to receive either HFNC or conventional oxygen therapy after extubation. Arterial blood samples were collected after anesthesia induction, after the end of the surgery, at the time of entering the ICU while they were intubated, 6 hours after entering the ICU, before removing the endotracheal tube, immediately after extubation, as well as 1, 6, 12, 24, and 36 hours after extubation. The patients were compared regarding PaCO2, PaO2/FiO2 ratios, respiratory failure, need for reintubation, development of atelectasis, pneumothorax, pleural effusion, and length of ICU stay. Results: The patients were similar regarding demographic characteristics, the duration of surgery, and mechanical ventilation (P &gt; 0.05). On the first and second days after the surgery, the mean modified radiologic atelectasis score (m-RAS) was lower in the HFNC group compared to the conventional oxygen therapy group (P &lt; 0.05). The frequency of respiratory failure did not differ in the groups before and after the surgery (P &gt; 0.05). PaCO2 was lower in the HFNC group than in the control group after extubation (P &lt; 0.001). PaO2/FIO2 ratio was significantly higher in the HFNC group one hour after extubation and afterward in comparison to the control group (P &lt; 0.001). The need for re-intubation (P &lt; 0.013) and the length of ICU stay (P &lt; 0.001) were significantly lower in the HFNC group compared to the control group. Conclusions: It was found that HFNC could improve the respiratory parameters and reduce postoperative pulmonary complications in infants following a congenital heart surgery.

Prevalence and antibiotic resistance of Acinetobacter baumannii among patients in postcardiac surgery intensive care units of Rajaei Hospital, Tehran

Prevalence and antibiotic resistance of Acinetobacter baumannii among patients in postcardiac surgery intensive care units of Rajaei Hospital, Tehran

Prevalence and antibiotic resistance of Acinetobacter baumannii among patients in postcardiac surgery intensive care units of Rajaei Hospital, Tehran.

Background: Acinetobacter baumannii is an opportunistic, aerobic, nonfermentative, Gram-negative bacterium that can cause major nosocomial infections, especially in patients hospitalized in intensive care units (ICU). Recently, A. baumannii strains have been resistant to a variety of antibiotics. Thus, it was aimed to evaluate the prevalence of A. baumannii and their resistance to the antibiotics in the patients hospitalized in postcardiac surgery ICU. Methods: This retrospective cross sectional study was performed in Rajaei hospital between March 2014 and February 2016. A. baumannii strains were isolated from blood cultures, catheter cultures, sputum cultures, and wound smear cultures. Then, isolates were characterized using standard morphological, cultural, and biochemical properties according to CLSI 2016. The frequency of A. baumannii species were reported as percent. Results: Among 27 167 patients were admitted to the ICU, 113 individuals, including 55 males and 58 females, were identified as A. baumannii-infected and the prevalence rate was 0.42%. The highest rates of antibiotic sensitivity were related to Meropenem 20 (17.7%) and Colistin 16 (14.1%). The shortest length of stay (LOS) for patients with A. baumanniiin the ICU was 3 days, while the longest LOS was 98 days. Conclusion: The findings indicated that A. baumannii strains isolated from postcardiac surgery ICUs had a high prevalence and were sensitive to Meropenem and Colistin. However, new molecular-based techniques are needed to monitor nosocomial infections. Therefore, the treatment of the patients may be feasible by appropriate antibiotic therapy, and infection control policies will be improved by adopting precise disinfection strategies.

A post cardiac surgery intervention to manage delirium involving families: a randomized pilot study.

As many delirium manifestations (e.g., hallucinations or fears) are linked to patients' experiences and personality traits, it is suggested that interventions should be tailored to optimize its management. The inclusion of family members, as part of an intervention, has recently emerged as a solution to developing individualised patient care, but has never been assessed in post-cardiac surgery intensive care unit where almost half of patients will present with delirium. To assess the feasibility, acceptability and preliminary efficacy of an nursing intervention involving family caregivers (FC) in delirium management following cardiac surgery. A randomized pilot study. A total of 30 patient/FC dyads were recruited and randomized to usual care (n = 14) or intervention (n = 16). The intervention was based on the Human Caring Theory, a mentoring model, and sources informing self-efficacy. It comprised seven planned encounters spread over 3 days between an intervention nurse and the FC, each including a 30-min visit at the patient's bedside. During this bedside visit, the FC used delirium management strategies, e.g. reorient the person with delirium. The primary indicator of acceptability was to obtain consent from 75% of approached FCs. The preliminary effect of the intervention on patient outcomes was assessed on (1) delirium severity using the Delirium Index, (2) occurrence of complications, such as falls, (3) length of postoperative hospital stay and (4) psycho-functional recovery using the Sickness Impact Profile. The preliminary effect on FC outcomes was assessed on FC anxiety and self-efficacy. Data were analysed using descriptive statistics, ANCOVAs and logistic regressions. The primary indicator of obtaining consent from FC was achieved (77%). Of the 14 dyads, thirteen (93%) dyads received all seven encounters planned in the experimental intervention. Intervention group patients presented better psycho-functional recovery scores when compared with control group patients (p = 0·01). Mean delirium severity scores showed similar trajectories on days 1, 2 and 3 in both groups. The mentoring intervention was acceptable and feasible and shows promising results in improving patients and FC outcomes. Nurses should involve, if willing, FC to participate in activities that optimise patient well-being FC to use recognized delirium management strategies like reorientation and reassurance.

Assessment of limited chest x-ray technique in postcardiac surgery management

Objectives:The objective of this study is to investigate the safety of elimination of chest radiography in the postcardiac surgery Intensive Care Unit (ICU).Methods and Design:We compared patients in two different groups of routine CXR (RCXR) and limited CXR (LCXR) and their diagnostic and therapeutic outcome in a University hospital-based single center from 2014 to 2016. 3 CXR in the RCXR group and 1 CXR in the limited group was performed, in addition to on-demand criteria.Measurement and Main Results:A total of 978 samples were acceptable for analysis which 55.21% of RCXR and 59.50% of LCXR were male patients. In total, 523 abnormalities in RCXR group and 154 occasions in LCXR group resulted in 26.73% diagnostic efficacy for RCXRs and 28.57% for LCXR. From 1956 CXR that was taken in RCXR group, 72 occasions required intervention (3.68%) and 84 cases out of 539 (15.58%) LCXR needed an action to therapy. This means a 14.40% in RCXRs’ abnormalities and 56.00% of LCXRs’ abnormalities were accompanied with some interventions.Conclusions:Abolishing routine CXR in the ICUs would not be harmful for the patients, and it can be managed based on their clinical status and other safer imaging techniques.

Improving Incidence of Postoperative Atrial Fibrillation After Cardiac Surgery Using Simplified Clinical Practice Guidelines.

Postoperative atrial fibrillation (POAF) remains a major risk after cardiac surgery. Twelve percent patients admitted to this unit postcardiac surgery experienced POAF, which led to hemodynamic instability, increased risk of stroke, and increased length of postoperative intensive care unit stay. Our aim was to decrease the incidence of POAF in the cardiothoracic intensive care unit by the end of April 2014. Design-Retrospective data analysis. Settings-Postcardiac surgery intensive care in a tertiary hospital. Postcardiac surgery patients. Intervention-A clinical practice guideline (CPG) was developed to promote early prevention and to improve adherence to POAF prophylaxis recommendations. Patient's charts were our key performance indicator. Primary outcome measure-Percentage of patients who developed episodes of POAF within the first 24 hours of cardiac surgery. Process measures-compliance with the newly developed CPG and early postoperative patient assessment. Balance measure-early administration of β-blocker. We were able to decrease POAF to 8% after intervention. Compliance with early assessment improved from 25% to 87%. Compliance with adherence to the CPG was 80%. Adherence to the newly developed paper form was the major challenge that could be overcome by an electronic form. We hope to decrease the incidence of POAF to 6% and develop an electronic form by the end of December 2014. This quality improvement project changed the strategy and succeeded in decreasing the incidence of POAF after cardiac surgery. It also improved early assessment of risk factors.

Hospital-acquired pneumonia in patients undergoing coronary artery bypass graft; comparison of the center for disease control clinical criteria with physicians' judgment.

Background:Following coronary artery bypass graft (CABG), patients are at high risk (3.2%-8.3%) for developing hospital-acquired pneumonia (HAP) with mortality rate of 24% to 50%. Some of routine features in patients undergoing CABG are similar to clinical criteria of Center of Disease Control (CDC) for diagnosis of pneumonia. This may lead to over-diagnosis of pneumonia in these patients.Objectives:This study aimed to assess the frequency of CDC criteria for diagnosis of pneumonia in patients undergoing CABG.Patients and Methods:This study was performed on CABG candidates admitted to post cardiac surgery Intensive Care Unit (ICU) in a six-month period. Patient’s records, Chest-X-Ray, and Laboratory tests were assessed for PNU1-CDC criteria for HAP diagnosis. At the same time, a physician who was unaware of the study protocol assessed the clinical diagnosis. Then the results were compared with CDC criteria-based diagnosis.Results:Of total 300 patients, 9 (3%) met CDC criteria for diagnosis of pneumonia while none of the cases were diagnosed as HAP according to the physicians’ clinical diagnosis. All nine patients were discharged with proper general condition and no need of antibiotic therapy. This study showed that loss of consciousness, tachypnea, dyspnea, PaO2 < 60 mm Hg, PaO2/FiO2 < 240, and local infiltration in 24 hours of operation were misleading features of CDC criteria, which were not considered in physicians’ clinical judgment to establish the diagnosis.Conclusions:Our findings suggest that in Post-CABG patients, physicians could judge the occurrence of HAP more accurately in comparison to making the diagnosis based on CDC criteria alone. Expert physician may intentionally do not take some of these criteria into account according the patients’ course of disease. Therefore, it is suggested that the value of these criteria in special group of patients like those undergoing CABG should be re-evaluated.

Effects of perfusion pressure on the splanchnic circulation after cardiopulmonary bypass: a randomized double cross-over study

No randomized trial has assessed the effects of different mean arterial pressure (MAP) targets in postcardiac surgery intensive care. We investigated the short-term effects of MAP of 65 or 85 mmHg on splanchnic oxygen flux, metabolic function, mucosal perfusion and cytokine regulation.

Fatal adenoviral necrotizing bronchiolitis case in a post-cardiac surgery intensive care unit

Fatal adenoviral necrotizing bronchiolitis case in a post-cardiac surgery intensive care unit

Fingertip photoplethysmographic waveform variability and systemic vascular resistance in intensive care unit patients

Low frequency variability in the fingertip photoplethysmogram (PPG) waveform has been utilized for inferring sympathetic vascular control, but its relationship with a quantitative measure of vascular tone has not been established. In this study, we examined the association between fingertip PPG waveform variability (PPGV) and systemic vascular resistance (SVR) obtained from thermodilution cardiac output (CO) and intra-arterial pressure measurements in 48 post cardiac surgery intensive care unit patients. Among the hemodynamic measurements, both CO (P < 0.05) and SVR (P < 0.0001) had statistically significant relationships with the normalized low frequency power (LF(nu)) of PPGV. The LF(nu) of baseline PPGV had moderate but significant positive correlation with SVR (r = 0.54, P < 0.0001), and a value below 52.5 nu was able to identify SVR < 900 dyn s cm⁻⁵ with sensitivity of 59% and specificity of 95%. The results have provided quantitative evidence to confirm the link between fingertip PPGV and sympathetic vascular control. Suppression of LF vasomotor waves leading to dominance of respiration-related HF fluctuations in the fingertip circulation was a specific (though not sensitive) marker of systemic vasodilatation, which could be potentially utilized for the assessment of critical care patients.

Flow-Regulated Extracorporeal Arteriovenous Tubing Loop for Cardiac Output Measurements by Ultrasound Velocity Dilution: Validation in Post-Cardiac Surgery Intensive Care Unit Patients

Assessment of cardiac output (CO) is crucial in the management of the critically ill, especially in post cardiac surgery intensive care unit (ICU) patients. In this study, we validated CO measured by the novel ultrasound dilution (COUD) with those measured by pulmonary artery (PA) thermodilution (COTD) in 26 adult post cardiac surgery patients. For COUD, blood was circulated through an extracorporeal arteriovenous (AV) loop from the radial artery catheter to the introducer of PA catheter for 5-8 minutes. Three to four injections of 25 ml body temperature isotonic saline were performed into the venous limb of the AV loop. For COTD, five injections of 10 ml ice cold saline were performed. A total of 77 COUD and COTD measurement sets were compared. Cardiac output measured by thermodilution ranged from 3.28 to 9.4 L/min, whereas COUD ranged from 2.85 to 10.1 L/min. The correlation between the methods was found to be r = 0.91, COUD = 0.93(COTD) + 0.42 L/min. Bias and precision (mean difference ± 2SDs) was -0.004 ± 1.34 L/min between the two methods. The percentage error (2SD/mean) was 22.2%, which is below the clinically acceptable limit (<30%). Cardiac output measured by ultrasound dilution and thermodilution methods agreed well in post cardiac surgery ICU patients and hence can be interchangeably used.

Estimation of Hemodynamic Parameters by Arterial Waveform: Available Technologies

To the Editor: Funk et al.1 present an interesting review concerning new minimally invasive technologies and devices available for measurement of cardiac output. In their review, Funk et al. did not consider 2 systems: the first is the Modelflow by Wesseling and co-workers2 installed on the Finometer® (Finapres Medical Systems, Amsterdam, The Netherlands); the second is the Pressure Recording Analytical Method (PRAM; used by MostCare®, Vytech Health, Padova, Italy) by Romano et al.3,4 “Pulse contour methods” (PCMs) can be divided into 3 categories: PCMs requiring an indicator dilution cardiac output measurement to calibrate the pulse contour; PCMs requiring patient demographic and physical characteristics for arterial impedance estimation; PCMs that work without any kind of calibration or preloaded data. The PRAM is the only methodology belonging to category 3 because neither calibration nor adjustments based on experimental data are required.3–5 Therefore, PRAM is different than all the other PCMs including the more recent Flo Trac Vigileo® (Edwards LifeSciences, Irvine, CA) and LiDCOrapid™ (LiDCO Ltd, London, UK), which require preloaded patient's demographic and physical characteristics (age, height, gender, and weight), similar to Modelflow6,7 (category 2). For PRAM, the area under the systolic portion of the arterial wave is computed by considering both pulsatile and continuous contributions (Acp). Stroke volume derives from the ratio between Acp and the arterial impedance Z(t) that is directly determined from the detailed analysis of the arterial wave sampled at high frequency (1000 Hz).3 Stefano Romagnoli, MD Heart and Vessels Department Cardiac and Vascular Anesthesia and Post-Cardiac Surgery Intensive Care Unit Careggi Hospital Florence, Italy [email protected] Salvatore Mario Romano, PhD Heart and Vessels Department Critical Care Medicine and Surgery University of Florence Careggi Hospital Florence, Italy

EComment: Brain natriuretic peptide is removed by continuous veno-venous hemofiltration in pediatric patients

We wanted to evaluate if brain natriuretic peptide (BNP) is cleared during continuous veno-venous hemofiltration (CVVH) sessions in children with congenital heart disease. A prospective observational single-center study was conducted in a post-cardiac surgery intensive care unit of the city children's hospital. Ten children requiring CVVH for acute kidney injury following cardiac surgery were enrolled. Seven of them were undergoing postoperative extracorporeal membrane oxygenation. BNP clearance was evaluated by the difference between pre-filter and post-filter BNP blood amount indexed to pre-filter BNP concentration. All CVVH treatments were performed with 0.6 m2 polyacrylonitrile filter, in predilution setting, at a dose of 80 ml/kg/h. Troponin I and myoglobin levels were also measured and CVVH clearances of these markers calculated for comparison with BNP. A significant decrease in post-filter compared with pre-filter levels of BNP was shown in all 10 cases (P 0.05) and their clearance was significantly lower than BNP (P: 0.0004). A daily analysis of BNP levels showed a significant decrease of its blood concentration. BNP levels were significantly reduced after three and four days from CVVH start (P<0.05). During 80 ml/kg/h CVVH, utilizing polyacrylonitrile membranes, BNP is efficiently cleared from blood in a small cohort of pediatric post-cardiosurgical patients. In this situation, BNP absolute blood levels may be unpredictable.

Brain natriuretic peptide is removed by continuous veno-venous hemofiltration in pediatric patients

We wanted to evaluate if brain natriuretic peptide (BNP) is cleared during continuous veno-venous hemofiltration (CVVH) sessions in children with congenital heart disease. A prospective observational single-center study was conducted in a post-cardiac surgery intensive care unit of the city children's hospital. Ten children requiring CVVH for acute kidney injury following cardiac surgery were enrolled. Seven of them were undergoing postoperative extracorporeal membrane oxygenation. BNP clearance was evaluated by the difference between pre-filter and post-filter BNP blood amount indexed to pre-filter BNP concentration. All CVVH treatments were performed with 0.6 m2 polyacrylonitrile filter, in predilution setting, at a dose of 80 ml/kg/h. Troponin I and myoglobin levels were also measured and CVVH clearances of these markers calculated for comparison with BNP. A significant decrease in post-filter compared with pre-filter levels of BNP was shown in all 10 cases (P<0.01). Median BNP clearance was 35.6 (29-39.3) ml/min. Troponin I and myoglobin levels did not show any significant drop between pre- and post-filter values (P>0.05) and their clearance was significantly lower than BNP (P: 0.0004). A daily analysis of BNP levels showed a significant decrease of its blood concentration. BNP levels were significantly reduced after three and four days from CVVH start (P<0.05). During 80 ml/kg/h CVVH, utilizing polyacrylonitrile membranes, BNP is efficiently cleared from blood in a small cohort of pediatric post-cardiosurgical patients. In this situation, BNP absolute blood levels may be unpredictable.

A hybrid hierarchical decision support system for cardiac surgical intensive care patients. Part II. Clinical implementation and evaluation

Patients emerging from cardiac surgery can display varying degrees of cardiovascular instability arising from potentially complex, multi-factorial and interlinked causes. Stabilization and control of the cardiovascular system are currently managed by healthcare experts using experiential knowledge, and, in some centers, manually inputted decision pathway algorithms. This paper describes a clinical trial undertaken to determine the basic functioning of a clinical decision support system (CDSS) designed and constructed by the authors to facilitate the control of the major cardiovascular components in the early post-operative phase. Part II follows Part I's description of the software and simulation testing of the CDSS, and describes the hardware setup of a patient monitoring and CDSS. The system is evaluated on three post-cardiac surgery intensive care patients whom had all undergone cardio-pulmonary bypass. The study was approved by the Sheffield Teaching Hospitals National Health Service (NHS) Foundation Trust Research Ethics Committee and conducted at the North Trent cardio-thoracic surgical unit and cardiac intensive care unit (CICU), Northern General Hospital, Sheffield (UK). Patients considered as 'very likely' to require active intervention to support the cardiovascular function following routine cardiac surgery were recruited during pre-operative surgical and anesthetic assessment, giving written informed consent when admitted for their operation. These patients underwent routine induction and maintenance of anesthesia by a non-study consultant anesthetist and the operation performed. There were no restrictions placed on the types of invasive monitoring used, on the use of trans-oesophageal echocardiography, drug selection, or the anesthetic agents selected by the clinicians performing the operations. All patients had full, routine invasive and non-invasive monitoring applied, including electrocardiography, central venous and peripheral arterial catheterisation, urine outputs and central temperature. After chest closure the patients were transferred to the CICU, sedated and ventilated, and the study commenced by the study anesthetist (1st author). The patients were in a clinically stable condition when admitted to the unit, and were attended by the treating clinicians until the handover to the study anesthetist occurred. The LiDCOplus (lithium dilution cardiac output) monitor (LiDCO Limited, Flowers Building, Granta Park, Cambridge CB1 6GU, United Kingdom) was calibrated after attachment to the patient's arterial line, and the patient's beat-to-beat hemodynamic data transferred to the host laptop computer. The CDSS graphical interface displays the patient's clinical details and specific cardiovascular data and prompts the anesthetist to input the target ranges for each parameter, and select a suitable advisor frequency. This is the frequency with which the therapeutic advice is displayed on screen with an audible prompt for a control inputs from the anesthetist. In each case this was selected to be 30s. When the study anesthetist agreed with the CDSS advice (administration of fluid, commencing a drug, altering the drug infusion rate) the syringe motif on the "Advisor Infusion Rates" panel of the graphical interface was 'clicked' on and the infusion rate immediately and manually inputted to Graseby 3400 pumps. If any disagreement between the anesthetist and the computer's advice arose, the syringe motif on the "Expert Infusion Rates" panel of the preferred drug was 'clicked' on and the expert's therapeutic decision (e.g. infusion rate) was entered in the corresponding data field and then applied to the pump. During all trials, data was stored for off-line analysis. The CDSS successfully selected suitable drug therapies for each case and advised reasonable and appropriate infusion rates such that the study anesthetist did not have to override the suggested CDSS instructions and infusion rates. Under differing clinical conditions the system was able to maintain clinically appropriate and stable control of the cardiovascular system (CVS), with good profiles under noisy physiological measurements, and was readily able to regain control following transient deterioration of the patient hemodynamic parameters (coughing, or during blood sampling).