Hemodynamic Measurements after Cardiac Surgery - Essay Example

?Article Critique/S Article Sharma, J, Bhise, M, Singh, A et al (2005) Hemodynamic Measurements after Cardiac Surgery: Transesophageal Doppler Versus Pulmonary Artery Catheter The aim and intention of this particular study are absolutely clear as the authors intended to compare the traditional, established mode of hemodynamic measurements’ in post cardiac surgical care patients i.e. through insertion of pulmonary artery catheter, considered an invasive procedure, to that of the modern, non-invasive, transesophageal Doppler technique, being recommended these days. In order to ascertain the idealness of selection of patients for this study, the authors’ shortlisted 35 patients undergoing the same procedure i.e. Coronary Artery Bypass Grafting surgery (CABG), while being careful that none of them had compromised ventricular function, the latter condition speculated by the authors’ as an interfering factor, which might have affected correct interpretation of the data aimed to be gathered during the study. Although the sex ratio was skewered due to predominantly male patient selection, it did not matter as end point measurements included standard cardiac parameters unlikely to be biased by sex of the patient. On all 35 patients, measurements were manually obtained by independent investigators, blinded to each other for avoiding bias due to consultation, and the numerous parameters calculated to measure the cardiac output (CO). Similar data was obtained automatically by associated software with the transesophageal Doppler machine. Four readings from each patient taken at specific time intervals yielded 140 readings for comparison with data obtained using the Doppler technique. Although, according to authors’ this seems enough data for comparison, but it appears that such data needs to be collected from a larger number of participants and by some automated software instead of human observers to reduce chances of bias due to human error and variable observation capability of different investigators. The design seems appropriate as similar/detailed parameters were calculated for comparison and recognized/valid statistical software and calculation techniques were used in the study. The main comparison has been done with the values of diverse hemodynamic factors obtained by TDCO (Thermo Dilution Cardiac Output) and the TECO branded transesophageal Doppler software. The authors’ discovered a poor correlation between the two, prompting them to criticize the automated technique due to the pertinence and importance of these parameters in saving the life of patients undergoing such challenging cardiac surgery procedures. They have substantiated their results with similar poor correlation in other studies of the kind, at the same time claiming that their own study was first of a kind, as it was done on off pump CABG unlike others. The authors’ may have claimed poor correlation between measurement of hemodynamic factors taken by the two different techniques, but they have neglected the issue that all patients were under heavy sedation and subject to the side effects of numerous drugs that were administered to them, most likely by different technicians at diverse, independently suitable dose rates for each patient, which may have affected the parameters under study. The authors’ seem to have a biased attitude towards the automated technique, making them condemn the latter due to over reliance on the older, invasive technique, with which they might be more familiar. Modern diagnostic probes and software are sensitive and free from human error and can report such parameters correctly, in a non invasive manner, which can assist in less discomfort to the patient and saving precious lives. Moreover a poor correlation obtained as a result of Bland Altman statistical analysis does not automatically and always imply that there is agreement between the two methods. Article 2: Hadian, M, Kim H K, Severyn, D A & Pinsky, M R (2010). Cross-comparison of cardiac output trending accuracy of LiDCO, PiCCO, FloTrac and pulmonary artery catheters The aim of this study is clear enough as the authors’ have tried to compare the different non invasive instruments available at the time of this study in multifarious cardiac surgery procedures, to accurately predict the cardiac output, in the post surgical environment. They have tried to establish correlation between three different types of instruments viz. LiDCO, PiCCO and FloTrac and the invasive technique PAC, and in the process have suggested that each instrument might be suitable for individualized use taking into consideration, patient characteristics, the drugs being used post surgically and the type of surgery the patient is being subjected to. The authors’ have been extremely meticulous in the design of their study. Although the sample size is small, wherein only 20 postoperative cardiac surgery patients were chosen for studying the parameters but the selection was made on the basis of strict inclusion and exclusion criteria aimed at obtaining accurate measurements using the three types of instruments. Data was however collected from only 17 patients due to non suitability from the rest 3 for various reasons. The distribution of sexes is also fair enough with 11 of them being male, although the age range was highly distributed between 54 to 82 years. However, control over such parameters is not possible as only the patients requiring such surgeries have to be chosen. The demographic data has however been carefully collected and the type of procedure performed on each patient specified. The study design is replete with detail. Authors’ have been careful enough to calibrate each instrument externally in order to suit the primary objective of this study. They have chosen only the instruments which allow external calibration as per the manufacturer’s recommendations. This was considered essential as internal calibration would have skewed the data, making it unfit for the comparative study. The WinDaq data acquisition system was used to obtain readings from the Flotrac, LiDCO and PiCCO systems, the data being fed offline into the latter to for the measurement of cardiac output (CO). Care was taken that a single person performed all data acquisition procedures and the mean of three readings was taken for each therapeutic intervention under which the sampling was done. Analysis of variance (ANOVA) and the Bland Altman techniques were employed for comparison of data from the three instruments. The degree of thoroughness and the meticulous details at every step as reported by the authors’ suggests that the study design, methodology and analysis were appropriate for the objective being aimed at. The main finding of the authors’ was that all techniques produced similar steady state CO values although the trending results were dissimilar between all four techniques. They have concluded that clinical efficacy of each non invasive technique needs to be evaluated independent of each other and the most appropriate instrument used for its particular suitability for specific cardiac surgery procedures. The risk of sepsis due to invasive techniques like PAC needs to be eliminated by utilizing the most appropriate non invasive instrument, as the authors’ comment that the latter is not a gold standard, as claimed by the authors of the first paper (Sharma et al, 2005). Article 3: Baldwin, I C & Heland M (2000) Incidence of cardiac dysrhythmias in patients during pulmonary artery catheter removal after cardiac surgery The aim of this study is clear enough as per the title itself. Pulmonary catheter removal is a routine procedure in post CABG patients; but subject to the occurrence of dysrhythmia in susceptible individuals, the incidence of which was investigated in this study. The authors’ have cited the paucity of such studies in the past as a basis for their research interest in the area. As the procedure is carried out by trained nurses, a teaching hospital in which such patients were routine was selected as the location for this research. No informed consent or permission from relevant authorities’ was sought as the procedure was a routine practice which has to occur in any case in all patients selected for the study. The study was done on 100 patients’, which is a considerable sample size to yield pertinent information as regards the motive of this study. Care was taken to have appropriate resuscitator equipment handy in all cases in order to avoid complications, thereby considering the safety of patients, which denotes a good ethical practice on part of the researchers. The sample size of 100 patients is adequate and fully justified. The authors have taken care to separate them into two groups, depending upon whether or not they were concurrently being administered any medication or exhibiting abnormalities in homeostatic parameters which were considered after evaluating their blood chemistry laboratory reports conducted 2 hours prior to the actual procedure. The study design is absolutely appropriate to the stated objective, as continuous cardiac monitoring to detect dysrhythmias was used during the procedure of removal of the PAC using the same technique in all patients. The measurement tools employed was a bedside monitor from a single manufacturer to record the ECG using Lead II, making it a uniform tool for all patients. The authors followed the technique in a uniform method for all patients, the procedure being described with meticulous detail in the article. The main finding of the authors’ was that dysrhythmias occurred only in a small fraction (19%) of the patients’ studied, with no differences emerging in the affected patients due to abnormal biochemistry measurements. A 2% incidence of non sustained VT (Ventricular Tachycardia) was however observed. The authors’ observed that as the patients belonged to a uniform category, their results may not be extrapolatable to patients’ with concurrent comorbidities such as respiratory insufficiency or hypomagnesaemia. Article 4: Bossert, T, Gummert, J F, Bittner, H et al (2006) Swan-Ganz Catheter-Induced Severe Complications in Cardiac Surgery:Right Ventricular Perforation, Knotting, and Rupture of a Pulmonary Artery The aim of this study as stated by the authors’ is to assess the level and frequency of complications encountered during the insertion of the Swan-Ganz catheter during cardiac surgical procedures. As this is an observational study, the authors’ have just reported the incidence of complications encountered in 3730 Swan-Ganz catheter insertions carried out during a period of one year in which a total of 7150 major cardiac surgeries were performed. In an observational study, the usual pattern is to report the incidence of adverse incidents and compare it with the total number of operations carried out employing the same technique. This gives a percentage level of adverse reactions’ which can lead to the prediction of a particular technique as safe or unsafe. The sample size in this study is justified as the study incorporated all operations carried out in a major cardiac surgery centre in Europe. At places where such operations are routine and their frequency is maximum with respect to the facility available in a particular region, such observational studies are ideal. The data collected in such studies is incidental and after calculating the percentage of adverse incidents, the benefits or not of a particular procedure or technique can be correlated with similar studies carried out at other major cardiac surgery centres of the world. The authors’ have cited the low incidence rate of complications (0.03- 0.1%) as reported with the above procedure as a precedent to the purpose of their present study and were able to demonstrate a percentage rate of as low 0.1, as the occurrence rate of complications resulting due to Swan-Ganz Catheter insertions. The complications included knotting of the catheter in one patient during insertion, right ventricular perforation in another and pulmonary artery rupture in two patients. The complications were handled appropriately following survival of the patient, except in one case, in which the patient died. Handling errors were blamed as the reason for such rare incidents and complications were identified to occur during insertion and placement procedures. As 3727 insertions in this study were carried out successfully, the authors inferred that the employed technique was justified as a valid and essential procedure for use in essential cardiac surgical procedures. The authors have presented adequate details necessary to be included in such studies and explained their observations with liberal use of strategically placed illustrations and details of all four patients in whom complications were encountered. The article is informative in content and serves the purpose for which this observational study was designed. Article 5: Takala, J., Ruokonen, E., Tenhunen, J. et al (2011) Early non-invasive cardiac output monitoring in hemodynamically unstable intensive care patients: A multi-center randomized controlled trial As the title suggests, the aim of this study was a randomized, multicentre trial in an effort to discern advantages, if any, of the non-invasive modes of cardiac output monitoring as compared to the traditional non-invasive one i.e. monitoring via insertion of a pulmonary artery catheter (PAC). The authors’ selected three prominent European Universities’ hospitals which catered to a maximum number of related cardiac surgeries relevant to their investigation intentions. Continuous availability of relevant cardiac surgeons and other experts at the three selected university hospital ICU’s was considered as an element of prime importance in relation to the purpose of this study. The aim of the study is therefore absolutely clear and well directed as the authors’ intention was to investigate the efficacy of the non-invasive cardiac output monitoring, which according to them has gained popularity recently. With newer and more accurate modes of non-invasive cardiac output monitoring being churned out by various manufacturers by the day, each claiming superiority and technological advances over the rival manufacturer, the timing of this study seems to be most appropriate. The primary focus area during their research was to analyze whether early monitoring with the used non-invasive technology at these teaching hospitals provided any distinct advantages by ensuring hemodynamic stabilization of the affected patients’ to improve their survival rate and subsequent clinical course during the therapeutic intervention, if any. The sample size shortlisted after randomization was that of 388 patients who were split into two approximately equivalent groups, 201 subjected to non-invasive mode of cardiac output monitoring and the rest 187 being subjected to the traditional, usually practiced technique of PAC. Randomization of the sample population under investigation was achieved through sequentially numbered and sealed envelopes and subsequent stratification at each university hospital separately to assign patients either to the study or the control group. Strict criteria of patient selection for the study were followed in order to eliminate variation due to prior cardiac condition factors, the type of disorders the selected patients were suffering from and on the basis of uniformity of multiple cardiac parameters measured on admission to the respective hospitals. The sample selection, randomization and masking were therefore done carefully in conformation of established criteria for such studies. As this was an international study, adequate infrastructure was available in tune with the aspiration of the investigators. The sample size is justified as it is likely to generate and yield adequate data for analysis as per the objectives aimed at by the investigators. The study design seems appropriate as the sample selection, locale of research, and the availability of subjects for this kind of study is ideal. The university hospitals were in eminent and distinct countries in Europe where advanced surgery of this kind has regularly been carried out for a significant period of time. As continuous monitoring of patients at such hospitals under experts available 24 hours a day, and seven days a week is possible, the likelihood of detection of the parameters investigated is high. Standard measurement tools for the measurement of hemodynamic parameters were used for all patients’, from the control as well as the study group. Simplified Acute Physiology Scores (SAPS) and Sequential Organ failure Assessment (SOFA) were the parameters recorded. As the focus time for stabilization of the hemodynamic parameters in both groups was a short period of the initial six hours after the application of either of the two modalities, the data obtainable for analysis is likely to be accurate. This was the primary outcome criterion. Standard and recommended statistical tools for data comparison were used. Validity and reliability of the study is therefore good. The authors’ were unable to demonstrate any advantages of the non-invasive techniques for cardiac monitoring and recovery of hemodynamic parameters in the study group as compared to the traditional, invasive methods used in the control group. In fact, outcomes were better in the control group. The authors’ have however, mentioned that as the cardiology experts at all hospitals were more familiar and well versed with the invasive technique of pulmonary artery catheterization, they may harbour preference for the latter due to over familiarity. Availability of better and later versions of non-invasive techniques and machines might lead to different results in subsequent trials of this nature. Article 6: Jacka, M.J., Cohen, M.M., To, T. et al (2002) The appropriateness of the pulmonary artery catheter in cardiovascular surgery As the title suggests, the primary aim of this article was to evaluate the appropriateness of the pulmonary artery catheter in multifarious cardiovascular surgical procedures as visualized by anaesthesiologists’ practicing within the North American continent viz. USA and Canada. The use of pulmonary artery catheter being controversial as regards its appropriateness and usefulness was a debatable issue at the time of this study, justifying the appropriateness of the timing of this study. The authors’ therefore planned this study in form of a survey in which practicing anaesthesiologists who were likely to routinely participate in such surgeries, at a minimal rate of at least one such surgical procedure per month, if not more, were selected. 345 anaesthesiologists were identified and selected and 265 actually responded appropriately to the survey, giving a percentage success response rate of 77%, which the authors’ claim satisfied the conditions for the generalize-ability of their results. The survey was administered in form of a questionnaire in which the respondents were asked to mark their responses according to a pre designed Lickert Scale, in which the participants marked their responses in a range specifying agreeing or not agreeing with the recommendation of PAC use for specific cardiac surgical procedures. The sample size is justified according to the design of the study but responses could have varied due to personal training, preferences and area of practice of the participating respondents. The design is appropriate only for a preliminary analysis of this kind as personal interviews, blinding and randomization are necessary for a truer evaluation. A study based on surveys can pinpoint only the trends and not the actual occurrences at cardiovascular surgery institutions. The measurement tools in the form of a Lickert Scale are however sufficient for a study in which surveillance of a trend is the primary objective, and agrees with the primary aim of this study. The data has been evaluated with suitable statistical tools for this kind of study which illustrate trends and the visual presentation in graphical representation is easy to comprehend. The authors’ were able to identify that most participants agreed to the suitability of the insertion of PAC as appropriate only in patients with severe ventricular impairment and unstable angina, and not in routine cardiovascular surgical procedures associated with stable angina and vascular interventions. The authors’ were able to detect that the practice is favoured more in community rather than institutional practice. Article 7: Jacka, M.J., Cohen, M.M., To, T. et al (2002) The Use of and Preferences for the Transesophageal Echocardiogram and Pulmonary Artery Catheter among Cardiovascular Anesthesiologists In a mirror image study protocol of the above study, the endeavour of the authors’ was to compare the then novel transesophageal echocardiography (TEE), non-invasive cardiac output monitoring modality as compared to the customary and more regularly used modality of a pulmonary artery catheter (PAC) (Jacka et al, 2002). This was the primary aim at which this surveillance study was targeted as the TEE was then tentatively considered as a gold standard in cardiac output monitoring. The sample population of Canadian and US anaesthesiologists’ involved in the study was 345, the same as in the above study and the response rate was also surprisingly equivalent at 77% of the total population queried. The data was collected in the form of survey questionnaire and the responses were normalized and subjected to valid and recognized statistical analysis necessary for arriving at significant inferences in such types of studies. Although the study design, statistical methods and analytical software used were identical to the previous similar study by the authors’ on the appropriateness of PAC in cardiac surgery procedures, the authors’ came up with some interesting findings as a result of this later effort. The analysis revealed that TEE was preferred only by participants’ who were trained in the technique by participating in continuing education programs. They preferred TEE only for procedures involving cardiac valvular surgery instead of one’s which involved aortocoronary bypass or abdominal vascular surgical procedures. An important discovery was that the equipment for TEE was only available at 56% of the facilities from where the experts were shortlisted. PAC, on the other hand was available at all institutions and the preferred mode for monitoring cardiac output by majority of the participants. Most participants did not indicate preference for either of the monitoring methods though the ones trained in TEE showed an inclination to use this technique over the more invasive PAC one. The results of this study are only indicative of a trend and the value of either technique needs to be studied in a more comprehensive randomized trial involving a larger number of hospitals, preferably worldwide. Article 8: Kaczmarek, R. G., Liu, C.K., & Gross, T.P. (2003) Medical Device Surveillance: Gender Differences in Pulmonary Artery Rupture after Pulmonary Artery Catheterization Pulmonary artery catheterization being a routine but invasive procedure employed in cardiovascular surgery, posing inherent threat to the patients’ life, the authors have been spurred by this fact to investigate the incidence of serious adverse effects with the procedure by retrospectively scouring the database in the United States for the reported adverse incidents. Based on the history that insertion of PAC invariably results in rupture of the pulmonary artery in majority of the cases, leading to death of the patient, the authors’ have conducted a search of the national database. To serve their purpose, they have utilized the FDA (Foods & Drugs Administration) agency data for investigating the submitted adverse reaction reports across a period of 10 years. The Medical Device Reporting (MDR) system in the United States is a reliable registry of such data with inputs being provided by various factions of involved parties, such as the hospitals, patient’s relatives and running cardiovascular surgeries within the country. The sample size for the kind of investigation was therefore adequate to the point of being substantial, which is mandatory for this type of research. The study design is appropriate although it is replete with self confessed limitations by the authors’ which include MDR being a passive surveillance system, lack of awareness of the reporting requirement, lack of independently verifiable data and missing information from the registry. The authors’ were nevertheless able to identify from their analysis that pulmonary artery rupture following PAC insertion is a complication worthy of attention as it invariably leads to death of the patient. The interesting finding of this study was that older patients’, particularly females were more prone to adverse effects as compared to their male counterparts. Of the 71 PA rupture cases studied in this research, the majority, 52 in particular, were those of women substantiating the higher risk in females for adverse reactions due to PA insertion. Besides gender, pre existing pulmonary hypertension and the use of anticoagulant agents during cardiac surgery were identified in this study as additional risks for the incidence of PA rupture. Article 9: Kanchi et al (2011) Do we need a pulmonary artery catheter in cardiac anesthesia? - An Indian perspective This study has been conducted with an aim to evaluate the utilization of pulmonary artery catheters during routine cardiovascular procedures in India, based on the predisposition to risk factors associated with the procedure. The author has mentioned that the adverse reactions may be associated more with routine insertions in intensive care units (ICUs) rather than those taking place during actual and emergent cardiovascular surgery in operation theatres. In their study design, the authors’ shortlisted 100 anaesthesiologists working in corporate as well as academic medical institutions in the country and a basic criterion of at least 500 cardiac operations annual turnover was fixed for sample selection. The study itself was in the form of a well designed questionnaire which the respondents were required to fill. Although the questionnaire shown in the paper is brief, it has well directed questions related to the motive for this study and the author was able to ensure 100% compliance from the expert respondents. The main findings of the study include favour of the practitioners for PAC as an evaluative procedure for cardiac parameters in CABG, left ventricular failure, recent myocardial infarction, septal repairs and other active procedures associated with direct interventions on the cardium. The authors’ inferred that PAC was considered essential by most respondents with a caution not to use it as a routine procedure, as in ICUs. Article 10: Kaplan M., Demirtas, M., Cimen, S. et al (2000) Swan-Ganz Catheter Entrapment in Open Heart Surgery The authors’ of this study have attempted to highlight the importance of critical care during the removal of the Swan-Ganz catheter following cardiac surgery. Highlighting the essentiality of the placement of the catheter as a routine procedure during cardiovascular surgeries, the authors’ have tried to identify the best modality and procedure to be adopted for removal of the catheter post operatively and the importance of post operative care in an ICU. The sample used for their assessment were 10 cases of cardiac valve replacement, 5 male and 5 female patients in a Turkish hospital, who had Swan-Ganz catheter entrapment as a post operative complication requiring surgery. Although the reported incidence of the complication at the hospital was extremely low, the authors’ identified the necessity of careful surgical removal of the indwelling entrapped catheter as absolutely essential in the affected patients. The study prompted the authors’ to recommend that either the Swan-Ganz catheter should not be left after conducting right or left atriotomy, or it should be moved after the operation to prevent entrapment. Article 11: Schwann, N.M., Hillel, Z., Hoeft, A. et al (2011) Lack of Effectiveness of the Pulmonary Artery Catheter in Cardiac Surgery The aim of this study was to identify the fact whether PAC was contributing to adverse reactions, including death in patients undergoing cardiovascular surgery, and whether the technique should be used at all or not. In order to serve the purpose of this aim, the authors’ employed a formal prospective observational design for their study and identified 5065 patients undergoing CABG in 70 prominent cardiac surgery centres over a period of 4 years viz. from 1996-2000. The systematic sampling protocol adopted by the authors’ and the propensity score match-pair analysis are valid statistical method for this type of analysis. The authors’ used predefined end points as adverse events to be recorded as the resultant sequel of PAC insertion as well as vital secondary indices to eliminate variations and error in their inferences drawn from this particular study. In 271 of the PAC patients, as compared to 196 non-PAC ones, the authors’ were successfully able to demonstrate their primary endpoint. Based on their observations, the authors’ were able to predict that PAC insertion during CABG resulted in higher risk of severe end organ complications as well as increased mortality. Claiming their results to be merely indicative, they have suggested a randomized controlled trail with defined hemodynamic goals as a sequel to the confirmation of their observations. Article 12: Stover, J.F., Stocker, R., Lenherr et al (2009) Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients This study was designed to compare a non-invasive mode of cardiac parameter monitoring viz. The branded Nefxin HD continuous noninvasive cardiac output and blood pressure monitoring system in which data is collected from a finger fitted cuff, to the more regularly employed but invasive pulmonary artery and arterial catheterization techniques. 10 patients’ in the authors’ institution were shortlisted for the study. The collected data from the patients was subjected to scrutiny, after due approval from the institutional ethics committee. Although the sample size seems small, the study design involved scrutiny of patients with identical conditions being treated in the same hospital, and is likely to demonstrate a trend which may need substantiation in larger, randomized studies. Both the noninvasive and the invasive techniques were used simultaneously in all patients. The equipment used was standard and uniform for all patients’. The mean age of patients being 54 +/- 12 years, and uniform pharmacological interventions being carried out in all patients, the study is likely to generate useful data for comparison. Analysis of the collected data revealed that there was a 29% variation error recorded using the two techniques, enabling the authors’ to infer that the noninvasive techniques need further refinement and should not be relied upon in critical cases. References Baldwin, I C & Heland M (2000) Incidence of cardiac dysrhythmias in patients during pulmonary artery catheter removal after cardiac surgery, HEART & LUNG VOL. 29, NO. 3, pp. 155-160 Bossert, T, Gummert, J F, Bittner, H et al (2006) Swan-Ganz Catheter-Induced Severe Complications in Cardiac Surgery:Right Ventricular Perforation, Knotting, and Rupture of a Pulmonary Artery, Card Surg Vol.21, pp.292-295 Hadian, M, Kim H K, Severyn, D A & Pinsky, M R (2010). Cross-comparison of cardiac output trending accuracy of LiDCO, PiCCO, FloTrac and pulmonary artery catheters, Critical Care 2010, 14:R212. pp. 1-10 Jacka, M.J., Cohen, M.M., To, T. et al (2002) The appropriateness of the pulmonary artery catheter in cardiovascular surgery, CAN J ANESTH, Vol. 49 (3), pp 276–282 Jacka, M.J., Cohen, M.M., To, T. et al (2002) The Use of and Preferences for the Transesophageal Echocardiogram and Pulmonary Artery Catheter among Cardiovascular Anesthesiologists, Anesth Analg 2002;94:1065–71 Kaczmarek, R. G., Liu, C.K., & Gross, T.P. (2003) Medical Device Surveillance: Gender Differences in Pulmonary Artery Rupture after Pulmonary Artery Catheterization, JOURNAL OF WOMEN’S HEALTH, Volume 12, Number 9, pp. 931-935 Kanchi et al (2011) Do we need a pulmonary artery catheter in cardiac anesthesia? - An Indian perspective, Annals of Cardiac Anaesthesia, Vol. 14 (1), pp.25-29 Kaplan M., Demirtas, M., Cimen, S. et al (2000) Swan-Ganz Catheter Entrapment in Open Heart Surgery, J Card Surg, Vol. 15 (3), pp. 313-315 Sharma, J, Bhise, M, Singh, A et al (2005) Hemodynamic Measurements after Cardiac Surgery: Transesophageal Doppler Versus Pulmonary Artery Catheter, Journal of Cardiothoracic and Vascular Anesthesia, Vol 19, No 6 (December), pp 746-750 Takala, J., Ruokonen, E., Tenhunen, J. et al (2011) Early non-invasive cardiac output monitoring in hemodynamically unstable intensive care patients: A multi-center randomized controlled trial, Critical Care 2011, 15:R148 Schwann, N.M., Hillel, Z., Hoeft, A. et al (2011) Lack of Effectiveness of the Pulmonary Artery Catheter in Cardiac Surgery, Anesthesia & Analgesia, Vol. 113 (5), pp. 994-1002 Stover, J.F., Stocker, R., Lenherr et al (2009) Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients, BMC Anesthesiology 2009, 9:6, pp. 1-5 Read More