Impact of bariatric surgery on cardiac structure, function and clinical manifestations in morbid obesity

Obesity results from the excessive accumulation of fat. Risk of premature death is doubled compared to nonobese individuals, and risk of death from cardiovascular disease is increased fivefold. In patients with morbid obesity, a variety of adaptations and alterations in cardiac structure and function occur in the individual, as an excess amount of adipose tissue accumulates. The high long-term failure rate of diet intervention is well acknowledged by the clinician. Surgery for severe obesity has evolved during the last 40 years. Many surgical techniques have been described and abandoned. Nevertheless, numerous different techniques are still in use today. Weight loss has beneficial impacts on functional and structural cardiac status and will be reviewed in this report.     

Impact of bariatric surgery on cardiac structure,function and clinical manifestations in morbid obesity

Obesity results from the excessive accumulation of fat. Risk of premature death is doubled compared to nonobese individuals, and risk of death from cardiovascular disease is increased fivefold. In patients with morbid obesity, a variety of adaptations and alterations in cardiac structure and function occur in the individual, as an excess amount of adipose tissue accumulates. The high long-term failure rate of diet intervention is well acknowledged by the clinician. Surgery for severe obesity has evolved during the last 40 years. Many surgical techniques have been described and abandoned. Nevertheless, numerous different techniques are still in use today. Weight loss has beneficial impacts on functional and structural cardiac status and will be reviewed in this report.     

How to calculate the quantity of CD34+ cells infused? A single center cohort study based on actual,ideal or adjusted ideal body weight

Transplant physicians are generally using the recipient's actual body weight (ABW) for the calculation of the content of CD34+ cells in the harvest material in hematopoietic stem cell transplantation (HSCT). As a reference center performing both the stem cell collection and HSCTs, we aimed to evaluate whether there were any differences for neutrophil recovery by calculating the CD34+ cell content in the graft according to actual, ideal (IBW) or adjusted IBW (AIBW) of the recipients in both autologous (n=148) and allogeneic stem cell collection setting (n=234). We observed a negative correlation between the neutrophil recovery and the cell doses infused as to each of these BWs in the allo-HSCT group, but not in the auto-HSCT group. This negative correlation was stronger for IBW and AIBW rather than for ABW in allo-HSCT group. In addition, calculations for both IBW and AIBW in autologous and allogeneic transplants revealed a significant difference in comparison to ABW for different cut-off values of infused CD34+ cells. Consequently, we suggested that both IBW and AIBW based calculations of CD34+ cells infused are better predictors of neutrophil recovery in comparison to ABW in allo-HSCT. We were not able to show this impact in autologous transplants.     

Bioimpedance cardiography measurements of cardiac output and other cardiovascular parameters

This paper describes impedance technique and device types, discusses hemodynamic data parameters that are available, discusses the differences between impedance cardiography and data that are derived from invasive pulmonary artery catheters, and explains how nurses can apply bioimpedance cardiography in a variety of patient populations.     

Continuous, on-line, real-time measurement of cardiac output and derived cardiorespiratory variables in the critically ill

A previously reported monitoring system provided continuous direct measurements of oxygen consumption and intravascular pressures. These data were combined with interval measurements of cardiac output and blood oxygen saturations to derive various hemodynamic and oxygen transport variables. This system has now been modified so that cardiac output is measured continuously in real-time.     

Gastroplasty in the treatment of morbid obesity

A series of 90 gastroplasty operations based on Eckhout's vertical banded procedure are described. The average weight loss at follow up 2 years postoperatively was 66%. There were no operative or late deaths nor any serious complications. The constricting Gore-Tex band had to be lengthened in 3 cases of outlet stenosis and shortened in another 3 cases of stomal dilatation. In one case the patient failed to lose weight due to a large initial pouch volume.     

Comparison of continuous thermodilution and bolus cardiac output measurements in septic shock

OBJECTIVE: To compare continuous (CCO) and bolus (BCO) thermodilution cardiac output measurement techniques over a wide range of cardiac outputs and blood temperatures in a septic sheep model. DESIGN AND SETTING: Prospective experimental study in a university intensive care laboratory. SUBJECTS: Thirty-five anesthetized sheep. INTERVENTIONS: Pulmonary artery catheters allowing measurement of CCO and BCO were placed through the external jugular vein. Cecal ligation and perforation was performed to induce septic shock. In 14 sheep two femoral venous catheters were placed and connected to a hemofiltration system to alter blood temperature. MEASUREMENTS: CCO and BCO were measured every hour during the experiment. Three 10-ml bolus injections of iced normal saline were given through a closed injectate system and then averaged. The CCO readings were collected just before the BCO measurements. The relationship between CCO and BCO was assessed using Bland and Altman's method. RESULTS: In 465 paired data the temperature ranged between 34.0 degrees and 40.9 degrees C, CCO between 1.4 and 17.0 l/min, and BCO between 1.1 and 17.4 l/min. There was a highly significant correlation between CCO and BCO ( r=0.97). The bias (difference between CCO and BCO) was -0.19 l/min, the SD of the difference 0.45 l/min, and the limits of agreement -1.08/0.71 l/min. There were also highly significant correlations between CCO and BCO at the different temperatures (extreme values: 34.0-34.9 degrees C, r=0.90; 40.0-40.9 degrees C, r=0.98). CONCLUSIONS: Thermodilution measurements of CCO are reliable, when compared to BCO measurements, over a large range of cardiac outputs and blood temperatures.     

Non-invasive measurements of cardiac output in atrial fibrillation: Inert gas rebreathing and impedance cardiography

Abstract

Background. Atrial fibrillation (AF) is associated with significant morbidity and mortality. To test the effect of interventions, knowledge of cardiac output (CO) is important. However, the irregular heart rate might cause some methods for determination of CO to have inherent weaknesses. Objective. To assess the validity of these methods in AF, a new inert gas rebreathing device and impedance cardiography was tested with echocardiography as reference. Methods. Using a cross-sectional design, 127 patients with AF and 24 in SR were consecutively recruited. Resting CO was measured using inert gas rebreathing (n = 62) or impedance measurement of intrathoracic blood flow (n = 89) in separate studies with echocardiographic measurement as reference. Results. CO determined with impedance cardiography was mean 4.77 L/min ± 2.24(SD) compared to 4.93 L/min ± 1.17 by echocardiography (n = 89, n.s.) in patients with AF. CO by inert gas rebreathing was 4.98 L/min ± 2.49(SD) compared to 5.70 L/min ± 2.49 by echocardiography (n = 62, n.s.) in patients with AF and SR (AF 5.42 ± 2.9 vs. 6.27, n.s. and SR 4.09 ± 1.08 vs. 4.35 ± 0.86, n.s.). Mean bias between impedance cardiography and echocardiography was 0.14 ± 0.95 L/min and ?0.13 ± 0.98 L/min between inert gas rebreathing and echocardiography. Inert gas rebreathing showed larger intra-patient variation than impedance cardiography (0.11 vs. 0.054). Correlation between inert gas rebreathing and echocardiography was r = ?0.060 and between impedance cardiography and echocardiography was r = 0.128. Impedance cardiography and inert gas rebreathing both underestimated CO compared to echocardiography. Conclusion. Variation between the inert gas rebreathing and the reference method for AF patients was less than desired. Impedance cardiography was superior to inert gas rebreathing and showed acceptable agreement with echocardiography and variability similar to echocardiography.     

Reliability of thermodilution derived cardiac output with different operator characteristics

Cardiac output (CO) is commonly measured using the thermodilution technique at the time of right heart catheterisation (RHC). However inter-operator variability, and the operator characteristics which may influence that, has not been quantified. Therefore, this study aimed to assess inter-operator variability with the thermodilution technique using a mock circulation loop (MCL) with calibrated flow sensors. Participants were blinded and asked to determine 4 levels of CO using the thermodilution technique, which was compared with the MCL calibrated flow sensors. The MCL was used to randomly generate CO between 3.0 and 7.0 L/min through changes in heart rate, contractility and vascular resistance with a RHC inserted through the MCL pulmonary artery. Participant characteristics including gender, specialty, age, height, weight, body-mass index, grip strength and RHC experience were recorded and compared to determine their relationship with CO measurement accuracy. In total, there were 15 participants, made up of consultant cardiologists (6), advanced trainees in cardiology (5) and intensive care consultants (4). The majority (9) had performed 26–100 previous RHCs, while 4 had performed more than 100 RHCs. Compared to the MCL-measured CO, participants overestimated CO using the thermodilution technique with a mean difference of +0.75?±?0.71 L/min. The overall r² value for actual vs measured CO was 0.85. The difference between MCL and thermodilution derived CO declined significantly with increasing RHC experience (P?<?0.001), increasing body mass index (P?<?0.001) and decreasing grip strength (P?=?0.033). This study demonstrated that the thermodilution technique is a reasonable method to determine CO, and that operator experience was the only participant characteristic related to CO measurement accuracy. Our results suggest that adequate exposure to, and training in, the thermodilution technique is required for clinicians who perform RHC.     

Lack of agreement between thermodilution and electrical velocimetry cardiac output measurements

Objective

The modified algorithm for the non-invasive determination of cardiac output (CO) by electrical bioimpedance—electrical velocimetry (EV^®)—has been reported to give reliable results in comparison with echocardiography and pulmonary arterial thermodilution (PA-TD) in patients either before or after cardiac surgery. The present study was designed to determine whether EV^®-CO measurements reflect intraindividual changes in CO during cardiac surgery.

Design

Prospective, observational study.

Setting

Operating room (OR) and intensive care unit (ICU) of a university hospital.

Patients

Twenty-nine patients undergoing elective cardiac surgery.

Interventions

None.

Measurements

CO was determined simultaneously by PA-TD and EV^® after induction of anesthesia (t1) and 4.9?±?3.5?h after ICU admission (t2).

Results

TD-CO was 3.9?±?1.4 and 5.4?±?1.1 l/min at t1 and t2 (?p?®-CO was 4.3?±?1.1 and 4.9?±?1.5 l/min at t1 and t2 (?p?=?0.013). Bland–Altman analysis showed a bias of ?0.4 l/min and 0.4 l/min and a precision of 3.2 and 3.6 l/min (34.3% and 67.4%) at t1 and t2, respectively. Analysis of the individual pre- to postoperative changes in CO with both methods revealed bidirectional changes in n?=?12 patients and unidirectional changes with a difference greater than 50% and less than 50% in n?=?9 and n?=?8 patients, respectively.

Conclusions

The disagreement between PA-TD and EV^®-CO measurements after anesthesia induction and after ICU admission, as well as the fact that thoracic bioimpedance did not adequately reflect pre- to postoperative changes in CO, questions the reliability of EV^®-CO measurements in cardiac surgery patients and contrasts sharply with previous studies.

     

Reproducibility of transpulmonary thermodilution cardiac output measurements in clinical practice: a systematic review

Measuring cardiac output (CO) is an integral part of the diagnostic and therapeutic strategy in critically ill patients. During the last decade, the single transpulmonary thermodilution (TPTD) technique was implemented in clinical practice. The purpose of this paper was to systematically review and critically assess the existing data concerning the reproducibility of CO measured using TPTD (COTPTD). A total of 16 studies were identified to potentially be included in our study because these studies had the required information that allowed for calculating the reproducibility of COTPTD measurements. 14 adult studies and 2 pediatric studies were analyzed. In total, 3432 averaged CO values in the adult population and 78 averaged CO values in the pediatric population were analyzed. The overall reproducibility of COTPTD measurements was 6.1 ± 2.0 % in the adult studies and 3.9 ± 2.9 % in the pediatric studies. An average of 3 boluses was necessary for obtaining a mean CO value. Achieving more than 3 boluses did not improve reproducibility; however, achieving less than 3 boluses significantly affects the reproducibility of this technique. The present results emphasize that TPTD is a highly reproducible technique for monitoring CO in critically ill patients, especially in the pediatric population. Our findings suggest that obtaining a mean of 3 measurements for determining CO values is recommended.     

Comparison between ultrasonic and thermodilution cardiac output measurements in intensive care patients

The reliability of ultrasonic cardiac output measurement was assessed using a commercial device that combines A-mode aortic root diameter determination and continuous wave (CW) Doppler flow velocity measurement in the ascending aorta. We compared this method with thermodilution (TD) cardiac output in 41 intensive care patients. Aortic root diameter measurement with A-mode was not possible in four (10%) patients. Using strictly defined criteria based upon our initial experience, we could not obtain acceptable CW Doppler flow signals in nine (22%) patients. Thus, ultrasonic cardiac output measurement was possible in 28 (68%) patients in whom there was an excellent correlation with cardiac output (r = 0.97; p less than .001). This study demonstrates that the transcutaneous CW Doppler method for measuring cardiac output is accurate and reliable in a limited percentage of ICU patients. Combining the CW Doppler with B-mode echocardiogram increases the applicability when an A-mode measurement is not possible.     

Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with thermodilution cardiac output measurements

Introduction  

Cardiac output (CO) monitoring is indicated only in selected patients. In cardiac surgical patients, perioperative haemodynamic management is often guided by CO measurement by pulmonary artery catheterisation (CO_PAC). Alternative strategies of CO determination have become increasingly accepted in clinical practice because the benefit of guiding therapy by data derived from the PAC remains to be proven and less invasive alternatives are available. Recently, a device offering uncalibrated CO measurement by arterial waveform analysis (CO_Wave) was introduced. As far as this approach is concerned, however, the validity of the CO measurements obtained is utterly unclear. Therefore, the aim of this study was to compare the bias and the limits of agreement (LOAs) (two standard deviations) of CO_Wave at four specified time points prior, during, and after coronary artery bypass graft (CABG) surgery with a simultaneous measurement of the gold standard CO_PAC and aortic transpulmonary thermodilution CO (CO_Transpulm).     

Gastric bypass in the management of morbid obesity

A report is presented on 82 gastric bypass operations performed from 1979 to 1988. The average preoperative body weight was 132 kg, the body mass index (BMI) 45.0 +/- 7.0. 1 patient died (mortality 1%). 88 per cent of all patients were followed up 2 months to 9 years (2.5 years on average) postoperatively. The mean weight loss was 40.8 kg (reduction of BMI 15.1). Obesity-related diseases decreased remarkably, 3 stomal ulcers and 5 cases of anemia occurred as late complications. On the basis of these results gastric bypass is shown to be an effective and safe treatment of morbid obesity.     

Imaging of morbid obesity procedures and their complications

Surgery for morbid obesity has become commonplace in the United States. Any radiologist who reads abdominal films, body CT, or does gastrointestinal fluoroscopy should be familiar with the surgical procedures and their imaging. Included in this update will be discussions of the vertical banded gastroplasty, Roux-en-Y gastric bypass, laparoscopic adjustable gastric banding, and biliopancreatic diversion with duodenal switch.     

The effect of lung injury and excessive lung fluid, on impedance cardiac output measurements, in the critically ill

Objectives: To investigate the relationship between the attenuation of impedance cardiac output (IC_co) measurements and lung fluid content in critically ill patients.¶Design: Observational study.¶Setting: Intensive Care Unit of a major teaching hospital in Hong Kong.¶Patients: Twenty-four critically ill patients who required a pulmonary artery catheter.¶Measurements and main results: Triplicate thermodilution cardiac output (TD_co) and BoMed NCCOM3 (IC_co) measurements were made simultaneously on a single occasion in each patient. Lung fluid accumulation was assessed by: (a) thoracic impedance (Zo), (b) radiological assessment of chest X-rays using an alveolar consolidation score (0–4) and (c) scoring the degree of hypoxia and use of positive end-expiratory pressure (PEEP). Offsets (TD_co–IC_co)/TD_co, expressed as percentage, were compared with these indices of excess lung fluid. Patients were divided into those with sepsis (n = 13), fluid balance problems (n = 5) and cardiothoracic problems (n = 6). Mean cardiac output values were: 6.7 l/min TD_co (range 3.6–12.9) and 5.2 l/min IC_co (range 2.7–9.0). Overall the TD_co and IC_co values showed great variance, with a bias and limits of agreement of 1.49 ± 4.16 l/min, or ± 69 %. In septic patients, increasing offset was correlated with decreases in Zo (r = 0.73, P = 0.005) and increases in alveolar consolidation score (r = 0.72, P = 0.005).¶Conclusions: The BoMed under-estimates cardiac output in critically ill patients. In septic patients the degree of attenuation of IC_co can be related to the extent of lung injury and fluid accumulation within the thorax.     

Comparison of measurements of cardiac output by bioimpedance and thermodilution in severely ill surgical patients

In order to evaluate a new thoracic electrical bioimpedance (TEB) system for measurement of stroke volume based on the Sramek-Bernstein equation, 391 paired values of cardiac output were measured simultaneously with the standard thermodilution method. These values were obtained from 16 patients selected for having the most severe illness during a 6-month period; the intent was to evaluate the bioimpedance method in the worst possible situations. The correlation coefficient (r) was 0.83, slope was 0.87, intercept was 1.53, and the mean difference between the two methods was 16.2 +/- 11.8 (SD)% in the total series. In 285 paired samples where satisfactory conditions were met, r was 0.90, slope was 0.98, intercept was 0.34, and the mean difference was 11.8 +/- 8.9%. The data indicate satisfactory correlations between these two methods. When the TEB waveform is satisfactory, the agreement between TEB and thermodilution is as good as the agreement between serial thermodilution methods. Difficulties may arise with dysrhythmias, tachycardia (heart rate greater than 150 beat/min), metal in the chest or chest wall, sepsis, hypertension, and extremely oily skin. Mechanical ventilation did not appear to be a problem.