Comparison of continuous cardiac output measurements in patients after cardiac surgery

OBJECTIVE: To investigate in a direct comparison accuracy and precision of continuous cardiac output measurements assessed by continuous pulmonary artery thermodilution technique (TDCCO), continuous pulse contour analysis (PCCO), and noninvasive partial CO(2)-rebreathing technique (NICO) in patients after coronary artery bypass grafting (CABG) during the postoperative period. DESIGN: Prospective, controlled clinical study. SETTING: University hospital. PARTICIPANTS: Twenty-two patients undergoing elective CABG surgery. INTERVENTIONS: Hemodynamic measurements were performed after admission to the ICU and in sequence every 2 hours during the subsequent 6-hour period. Simultaneously, cardiac output (CO) was measured using a TDCCO, PCCO, and NICO. After the continuous cardiac output measurements were read, bolus thermodilution-derived cardiac output was obtained from thermodilution curves detected in the pulmonary artery (TDBCO(pa)). Four intermittent consecutive boli consisting of 10 mL of ice-cold saline were randomly injected over the ventilatory cycle. MEASUREMENTS AND MAIN RESULTS: The comparison between the continuous cardiac output measurement methods TDCCO versus PCCO showed a bias of -0.12 L/min, between TDCCO versus NICO -0.17 L/min, and between PCCO versus NICO -0.44 L/min. The comparison to the reference technique between TDBCO(pa) versus TDCCO revealed a bias of -0.28 L/min, between TDBCO(pa) versus PCCO -0.40 L/min, and between TDBCO(pa) versus NICO -0.64 L/min. CONCLUSIONS: The results of this clinical investigation show agreement between TDCCO and PCCO to satisfy clinical requirements in a setting of postoperative patients after cardiac surgery. In contrast, the NICO monitor is of very limited use in these patients.     

Non-invasive cardiac output monitoring

Outcomes in the management of critically ill patients may be improved using goal directed peri-operative haemodynamic monitoring. A conservative approach may no longer be acceptable but in view of the significant morbidity associated with balloon tipped flow directed pulmonary artery catheters a non-invasive approach would be preferable. In this review we consider the different non-invasive techniques available and discuss the advantages and disadvantages of each technique.     

Objective assessment of cardiac output in infants after cardiac surgery

An accurate measurement of cardiac performance in infants after cardiopulmonary bypass has long been considered to be an important part of postoperative management. To be useful in clinical decision making, such measurements should ideally be reproducible, non invasive and accurately reflect tissue perfusion and oxygen delivery. Historically, we have relied on intermittent measurements of cardiac output using indicator dilution methods; and more recently, technologies that use pulse contour analysis, bio-impedance, or Doppler methodology. These all have the same shortcoming, that they provide a number that the information as to whether it provides adequate tissue perfusion. There is increasing emphasis being placed on the measurement of oxygen delivery either by mixed venous oxygen saturation and serum lactate, which are important markers of the adequacy of organ perfusion; and relating this to outcome, the development of organ dysfunction and length of ICU stay.     

Management of low cardiac output syndrome after cardiac surgery using enoximone

This case report describes the use of enoximone, a potent phosphodiesterase F-IV inhibitor with inotropic and vasodilator actions, to treat low output syndrome after cardiac surgery. The reduced cardiac output was unresponsive to a combination of inotropic drugs and intra-aortic balloon counterpulsation was contraindicated. Cardiac output was increased dramatically by enoximone, but systemic vascular resistance and perfusion pressure remained low until the addition of metaraminol.     

心脏瓣膜手术期间CCO与TCO的一致性变化

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Non-invasive ventilation after surgery

After surgery, hypoxemia and/or acute respiratory failure (ARF) mainly develop following abdominal and/or thoracic surgery. Anesthesia, postoperative pain and surgery will induce respiratory modifications: hypoxemia, pulmonary volumes decrease and atelectasis associated to a restrictif syndrome and a diaphragm dysfunction. Maintenance of adequate oxygenation in the postoperative period is of major importance, especially when pulmonary complications such as ARF occur. Although invasive endotracheal mechanical ventilation has remained the cornerstone of ventilatory strategy for many years for severe acute respiratory failure, several studies have shown that mortality associated with pulmonary disease is largely related to complications of postoperative reintubation and mechanical ventilation. Therefore, major objectives for anesthesiologists and surgeons are first to prevent the occurrence of postoperative complications and second if ARF occurs is to ensure oxygen administration and carbon dioxide CO₂ removal while avoiding intubation. Non-invasive ventilation (NIV) does not require endotracheal tube or tracheotomy and its use is well established to prevent ARF occurrence (prophylactic treatment) or to treat ARF to avoid reintubation (curative treatment). Studies shows that patient-related risk factors, such as chronic obstructive pulmonary disease (COPD), age older than 60 years, American Society of Anesthesiologists ASA class of II or higher, obesity, functional dependence, and congestive heart failure, increase the risk for postoperative pulmonary complications. Rationale for postoperative NIV use is the same as the post-extubation NIV use plus the specificities due to the respiratory modifications induced by the surgery and anesthesia. Postoperative NIV improves gas exchange, decreases work of breathing and reduces atelectasis. The aims of this article are (1) to review the main respiratory modifications induced by surgery and anesthesia which justify postoperative NIV use (2) to offer some recommendations to apply safely postoperative NIV and (3) to present the main results obtained with preventive and curative NIV in a surgical context.     

Non-invasive cardiac output determination: state of the art

This review deals with recent developments in non-invasive cardiac output measurement. In the past few years significant progress has been made with semi-invasive transoesophageal echocardiography; the method now provides advanced facilities to measure cardiac output and other important characteristics of cardiac function. The method is, however, operator-dependent and the equipment used is expensive, which means that large-scale use on intensive care patients is not feasible. Whole-body impedance cardiography has recently shown good accuracy and flexibility in use, and seems to be the most promising method for the non-invasive measurement of cardiac output.     

Decreased cardiac output in humans during laparoscopic antireflux surgery: direct measurements

OBJECTIVE: In a porcine model, we demonstrated that laparoscopic Nissen fundoplication causes a significant drop in cardiac output (30%) because it exposes both the peritoneal cavity and the mediastinum to CO(2) under pressure. To determine if this occurs in humans, we examined cardiovascular physiology during laparoscopic Nissen fundoplication. Because of invasiveness required in this pilot trial, only six patients were studied. METHODS: The arterial blood pressure (via radial arterial catheter) and the pulmonary artery diastolic pressure and cardiac index (via pulmonary artery thermodilution catheter) were measured at seven points in time during each laparoscopic Nissen fundoplication. RESULTS: The systolic blood pressure decreased in all patients, and the cardiac index decreased in all but one patient. The exception was a patient with Huntington disease, in whom the cardiac output did not decrease. In four of the five patients, the cardiac output was lowest during hiatal dissection, and in the fifth, it was lowest after reverse Trendelenburg positioning. No significant change in the pulmonary artery diastolic pressure was noted. All patients received adequate intravenous fluid replacement (average, 58 +/- 16 mL/kg) to support blood pressure. In one patient, with a particularly large paraesophageal hernia, profound hypotension (40/25 mm Hg) developed during the mediastinal phase of the procedure, and this patient required alpha-adrenergic support followed by laparotomy to eliminate a surgical cause (none found). CONCLUSIONS: Although it is a tremendous advance for patients, laparoscopic Nissen fundoplication can be associated with a significant reduction in cardiac output and blood pressure. Surgeons and anesthesiologists must be alert to changes reflecting these decreases during procedures, which violate both the peritoneal cavity and the mediastinum. We propose careful hemodynamic monitoring during these procedures, especially in patients with coronary artery disease or significant left ventricular dysfunction.     

Monitoring of cardiac output by thermodilution after open-heart surgery.

One hundred twenty-five separate cardiac output determinations were obtained after open-heart surgery in 10 patients by simultaneous use of thermodilution and dye-dilution techniques. Mean thermodilution cardiac output was 1.6 per cent greater than mean dye-dilution cardiac output (5.24 versus 5.16 L. per minute). Reproducibility of thermodilution cardiac output (coefficient of variation, 8.6 per cent) was superior to that of dye-dilution cardiac output (coefficient of variation, 12.3 per cent) for outputs ranging from 2.5 to 8.7 L. per minute (p less than 0.001). Linear regression analysis revealed a correlation showing that COtd = 0.86 COdye + 0.80 (r = 0.9, p less than 0.001) and indicating a similarity between thermodilution and dye-dilution output figures except in extremely low output states. In such cases, thermodilution cardiac output becomes progressively larger than dye-dilution cardiac output. The results indicate that thermodilution cardiac output is a valid method for determining cardiac output in the rapidly changing clinical setting following cardiopulmonary bypass. Clinical applications of this technique include evaluation of the efficacy of inotropic agents, effectiveness of intra-aortic balloon counterpulsation, and status of the low output syndrome postoperatively. Routine use in patients with Class III or IV cardiac disease appears justified.     

Impedance cardiography in cardiac surgery patients: abnormal body weight gives unreliable cardiac output measurements

Background: To study the accuracy of cardiac output measurement by means of Electrical Impedance Cardiography (EIC) in post-cardiac surgery patients.
Methods: In a prospective study, we compared cardiac output measurements by means of thermodilution (COTD) with impedance cardiographic-derived values (CO^EIC) in 37 mechanically ventilated patients after cardiac surgery. Both methods were used simultaneously.
Results: CO^EIC values were weakly correlated with CO^TD in the total group when the equation of Sramek-Bernstein was employed to calculate CO^EIC (r=0.60, P < 0.001, mean difference and standard deviation: -0.06±1.25 l-min^-1). After exclusion of the 12 patients whose body weight differed >15% from their ideal body weight, no significant difference was found between the mean values (5.40±1.80 l-min^-1 (CO^EIC) vs 5.31±1.69 l-min^-1, n=25) while the correlation coefficient increased substantially (r=0.85, P < 0.001, mean difference and standard deviation: 0.09±0.96 l-min^-1).
Conclusions: The results of this study indicate that weight is a very important factor in unreliable measurement of CO by impedance cardiography in cardiac surgery patients. The calculation equation as proposed by Sramek and Bernstein is not accurate enough in patients with more than 15% of weight deviation. Therefore, the use of impedance cardiography in these patients is of limited value until an accurate correction factor has been developed.     

Measurement of cardiac output after cardiac surgery by a new transesophageal Doppler device

OBJECTIVES: Assessment of hemodynamics by transesophageal Doppler devices (TDD) may be a less invasive alternative to the pulmonary artery catheter. In contrast to the TDD evaluated so far, a new monitor (HemoSonic100) measures both blood flow velocity and the diameter of the descending aorta. The aim of this study was to assess the accuracy of the cardiac output/index (CO/CI) measured by this device compared with the CO/CI measured by thermodilution. DESIGN: Prospective nonrandomized study. SETTING: Community hospital; university-based statistician. PARTICIPANTS: Twenty-two patients. INTERVENTIONS: Elective coronary artery bypass grafting and/or valve replacement/repair. MEASUREMENTS AND MAIN RESULTS: After routine cardiac surgery, CO/CI was determined in the intensive care unit by iced-water bolus (IWB), continuous cardiac index (CCI) assessment, and the TDD. Matched measurements were made with each patient at intervals of 30 minutes. Six percent of sets were incomplete because of failed signal detection by the TDD. Bland-Altman analysis revealed a mean bias of 0.23 L/min/m(2) for TDD and IWB. Mean bias for CCI and IWB was 0.11 L/min/m(2). The correlation between TDD and IWB (r(2) = 0.09) for cardiac index was found to be inferior to the correlation between CCI and IWB (r(2) = 0.65). Trend analysis between sequential measurements (T1-4: dTDD, dCCI, dIWB) showed a lower correlation between dTDD and dIWB (r(2) = 0.1) compared with the correlation between dCCI and dIWB (r(2) = 0.44). CONCLUSION: The transesophageal Doppler device (HemoSonic100) cannot be recommended as a sole method for monitoring cardiac output in patients after cardiac surgery.     

Non-invasive positive pressure ventilation for bilateral diaphragm paralysis after pediatric cardiac surgery

We present the case histories of two children having respiratory failure due to bilateral diaphragm paralysis after cardiac surgery. In both children non-invasive positive pressure ventilation alleviated respiratory distress, improved gas exchange, and prevented the need for endotracheal intubation. Following unilateral recovery of diaphragmatic function both children were successfully weaned from non-invasive positive pressure ventilation.