Transthoracic Electrical Bioimpedance Research Articles

Measurement of non-invasive cardiac output during cycling exercise in ischemic stroke inpatients: A pilot study.

Cardiac dysfunction accompanies acute ischemic stroke and affects the effective implementation of early rehabilitation interventions. There is a lack of reference hemodynamic data on cardiac function in the subacute phase of ischemic stroke. In this study, we aimed to identify appropriate cardiac parameters for exercise training utilizing a pilot study. We used a transthoracic electrical bioimpedance non-invasive cardiac output measurement (NICOM) device to monitor cardiac function in real time for two groups [i.e., subacute ischemic stroke inpatients group (n= 10) and healthy control group (n= 11)] using a cycling exercise experiment. The parameters of both groups were compared to highlight the cardiac dysfunction in the subacute phase in patients with ischemic stroke. We considered stroke volume index (SVI) and systemic vascular resistance index (SVRi) as the primary outcomes, and there was significant intragroup difference (stroke group: P< 0.001; control group: P< 0.001, using one-way ANOVA) and significant intergroup difference at each individual time segment (P< 0.01, using independent t-test). Among the secondary outcomes, i.e., cardiac index (CI), ejection fraction (EF), end-diastolic volume (EDV), and cardiac contraction index (CTI), we found significant intergroup differences in CI, EF, and CTI scores (P< 0.01, using independent t-test). Significant interaction with respect to time and group were seen only in the SVRi and CI scores (P< 0.01, using two-way ANOVA). There was no significant inter- or intra-group differences in EDV scores. SVRI, SVI, and CI values highlight cardiac dysfunction in stroke patients the most. At the same time, these parameters suggest that cardiac dysfunction in stroke patients may be closely related to the increased peripheral vascular resistance caused by infarction and the limitation of myocardial systolic function.

Impact of patent ductus arteriosus on non-invasive assessments of lung fluids in very preterm infants during the transitional period

This prospective observational study aimed to evaluate whether lung fluids, assessed by lung ultrasonography and transthoracic electrical bioimpedance (TEB), may be influenced by the presence of a haemodynamically significant patent ductus arteriosus (hsPDA) in very preterm infants during the transitional period. Infants < 32 weeks of gestational age (GA) admitted to the neonatal intensive care units of IRCCS AOU Bologna and Niguarda Metropolitan Hospital of Milan (Italy) underwent a daily assessment of a lung ultrasound score (LUS) and of a TEB-derived index of thoracic fluid contents (TFC) during the first 72 h after birth. Echocardiographic scans were simultaneously performed to evaluate the concomitant ductal status (hsPDA vs. restrictive or closed duct). The correlation between LUS, TFC, and the ductal status was tested using generalized estimating equations. Forty-six infants (median GA: 29 [interquartile range, IQR: 27–31] weeks; median birth weight: 1099 [IQR: 880–1406] g) were included. At each daily evaluation, the presence of a hsPDA was associated with significantly higher LUS and TFC compared with a restrictive or closed ductus (p < 0.01 for all comparisons). These results were confirmed significant even after adjustment for GA and for the ongoing modality of respiratory support. Conclusion: Even during the first 72 h of life, the presence of a hsPDA determines a significant increase in pulmonary fluids which can be non-invasively detected and monitored over time using lung ultrasonography and TEB.What is Known:• Lung ultrasonography provides a non-invasive assessment of lung fluids and is widely used in neonatal settings.• In preterm infants, the persistence of a haemodynamically significant patent ductus arteriosus (hsPDA) over the first weeks can negatively affect pulmonary outcomes.What is New:• The presence of aan hsPDA is associated with increased lung fluids since early postnatal phases.• Lung ultrasonography and transthoracic electrical bioimpedance can effectively monitor lung fluid clearance in preterm infants with a hsPDA during the transitional period, with potential clinical implications.

Prediction of respiratory distress severity and bronchopulmonary dysplasia by lung ultrasounds and transthoracic electrical bioimpedance.

This study aims to evaluate whether the assessment of a lung ultrasound score (LUS) by lung ultrasonography and of thoracic fluid contents (TFC) by electrical cardiometry may predict RDS severity and the development of bronchopulmonary dysplasia (BPD) in preterm infants with respiratory distress (RDS). Infants ≤ 34weeks' gestation admitted with RDS to two neonatal intensive care units were prospectively enrolled in this observational study. A simultaneous evaluation of LUS and TFC was performed during the first 72h. The predictivity of LUS and TFC towards mechanical ventilation (MV) need after 24h and BPD development was evaluated using receiver operating characteristic analysis. Sixty-four infants were included. The area under the curve (AUC) for the prediction of MV need was 0.851 (95%CI, 0.776-0.925, p < 0.001) for LUS and 0.793 (95%CI, 0.724-0.862, p < 0.001) for TFC, while an AUC of 0.876 (95%CI, 0.807-0.946, p < 0.001) was obtained for combined LUS and TFC evaluation. LUS and TFC AUC for BPD prediction were 0.769 (95%CI, 0.697-0.842, p < 0.001) and 0.836 (95%CI, 0.778-0.894, p < 0.001), respectively, whereas their combined assessment yielded an AUC of 0.867 (95%CI, 0.814-0.919, p < 0.001). LUS ≥ 11 and TFC ≥ 40 were identified as cut-off values for MV need prediction, whereas LUS ≥ 9 and TFC ≥ 41.4 best predicted BPD development. Conclusion: A combined evaluation of LUS and TFC by lung ultrasonography and EC during the first 72h may represent a useful predictive tool towards short- and medium-term pulmonary outcomes in preterm infants with RDS. What is Known: •Lung ultrasonography is largely used in neonatal intensive care and can contribute to RDS diagnosis in preterm infants. •Little is known on the diagnostic and predictive role of TFC, measured by transthoracic electrical bioimpedance, in neonatal RDS. What is New: •Combining lung ultrasonography and TFC evaluation during the first 72 h can improve the prediction of RDS severity and BPD development in preterm infants with RDS and may aid to establish tailored respiratory approaches to improve these outcomes.

Evaluation of Electrode Setups by MRI Based Human Phantom with FEM Based Quasi-Static Solver for Bioimpedance Measurement.

Transthoracic electrical bioimpedance (TEB) measurement for acquiring of hemodynamic parameters e.g. stroke volume (SV) and cardiac output (CO) becomes commonly used. For precise and reliable measurement, a good understanding of the measurement system is needed to provide robust electrode placement, reproducible results, and large signal amplitudes. We propose an evaluation by MRI based human phantom with FEM based quasi-static solver for electrode placement in bioimpedance measurement. Placements according to Osypka, Cheetah and Bernstein et al. were simulated and compared with measurements taken from a (real) human subject. As a parameter for evaluation of signal quality, the percentage of current passing through the descending aorta from the overall injected current is measured. The placement according to Osypka results in 1.46 % of current flow through the descending aorta (Cheetah placement 1.12 %, Bernstein et al. placement 0.877 %) for the male human phantom DUKE. The simulation was compared with a real human subject (with comparable age, height, weight) by calculating the baseline impedance (Z0). The simulation seems to fit at best with Osypka placement, where the deviation between simulated baseline impedance and real human subject is 19.9 % (deviation for Cheetah 34.1 %, deviation for Bernstein 62.5 %). The simulation with MRI based human phantoms seems to be a very good basis for further investigations of current injection and bioimpedance measurement comprehension.

Non-invasive stroke volume estimation by transthoracic electrical bioimpedance versus Doppler echocardiography in healthy volunteers

Thoracic electrical bioimpedance (TEB) and transthoracic echocardiography (TTE) are non-invasive methods to estimate stroke volume (SV) and cardiac output (CO). Thoracic electrical bioimpedance is not in widespread clinical use with reports of inaccurate cardiac output estimation compared to invasive monitors, particularly in non-healthy populations. We explore its use as a trend monitor by comparing it against thoracic echocardiography in fifteen healthy volunteers undergoing two physical challenges designed to vary cardiac output. Of all paired values, 54.6% showed gross trend agreement and only 1.9% showed direct disagreement between the two monitors. Our results show thoracic bioimpedance may have a role as a non-invasive cardiac output trend monitor in healthy volunteer studies.

Comparative Assessment of Stroke Volume by Transthoracic Electrical Bio-Impedance &amp; Echocardiography in Patients of Acute Myocardial Infarction

Comparative Assessment of Stroke Volume by Transthoracic Electrical Bio-Impedance &amp; Echocardiography in Patients of Acute Myocardial Infarction

Textrode-enabled transthoracic electrical bioimpedance measurements – towards wearable applications of impedance cardiography

Abstract During the last decades the use of electrical bioimpedance (EBI) in the medical field has been the subject of extensive research, as an affordable, harmless and non-invasive technology. In some specific applications, such as body composition assessment where EBI has proven a good degree of effectiveness and reliability, the use of textile electrodes and measurement garments have shown good performance and reproducible results. Impedance cardiography (ICG) is a modality of EBI that can benefit from the implementation and use of wearable sensors. ICG is based on continuous impedance measurements of a longitudinal segment across the thorax taken at a single frequency. The need for a specific electrode placement on the thorax and neck can be easily ensured with the use of a garment with embedded textile electrodes, also known as “textrodes.” The first step towards the implementation of garment-based ICG is to determine the quality of ICG measurements with textile sensors to allow estimation of fundamental ICG parameters. In this work, the measurement performance of a 2-belt set with incorporated textrodes for thorax and neck is compared against ICG measurements obtained with Ag/AgCl electrodes. The analysis is based on the quality of the fundamental ICG signals (ΔZ, dZ/dt and ECG), systolic time intervals and other ICG parameters. The results indicate the feasibility of using textrodes for ICG measurements with consistent measurements and relatively low data dispersion. Thus, enabling the development of measuring garments for ICG measurements.

The PhysioFlow Thoracic Impedancemeter Is Not Valid for the Measurements of Cardiac Hemodynamic Parameters in Chronic Anemic Patients

The aim of the present study was to test the validity of the transthoracic electrical bioimpedance method PhysioFlow® to measure stroke volume in patients with chronic anemia. Stroke volume index (SVI), as well as cardiac index (CI) obtained by transthoracic electrical bioimpedance method and doppler echocardiography were compared in healthy subjects (n = 25) and patients with chronic anemia (i.e. mainly with sickle cell anemia; n = 32), at rest. While doppler echocardiography was able to detect difference in SVI between the two populations, the Physioflow® failed to detect any difference. Bland & Altman analyses have demonstrated no interchangeability between the two methods to assess CI and SVI in anemic patients and healthy subjects. While doppler echocardiography displayed a good concordance for SVI results with those obtained in the literature for anemic patients, the Physioflow® did not. Finally, in contrast to doppler echocardiography: 1) the CI obtained with the Physioflow® was not correlated with the hemoglobin level and 2) the stroke volume determined by the Physioflow® was highly influenced by body surface area. In conclusion, our findings indicate that the Physioflow® device is inaccurate for the measurement of SVI and CI in patients with chronic anemia and has a poor accuracy for the measurement of these parameters in African healthy subjects.

Use of Bioimpedance to Assess Changes in Hemodynamics During Acute Administration of CPAP.

BackgroundAttempts to investigate the mechanisms by which continuous positive airway pressure (CPAP) therapy improves heart function in patients with obstructive sleep apnea (OSA) have been limited by the lack of non-invasive methods to assess cardiac performance. We used transthoracic electrical bioimpedance (TEB) to assess acute hemodynamic changes including heart rate (HR), stroke volume (SV), cardiac output (CO) and cardiac index (CI) during PAP titration in (1) post-operative cardiac surgery patients, (2) patients with severe OSA, and (3) normal healthy volunteers.MethodsPost-operative cardiac surgery patients were studied via TEB and pulmonary artery catheter (PAC) during acute titration of positive end-expiratory pressure (PEEP) while mechanically ventilated. Patients with severe OSA were studied non-invasively by TEB during acute CPAP titration in supine stage 2 sleep, and normal subjects while awake and recumbent.ResultsIn post-operative cardiac surgery patients (n = 3), increasing PEEP to 18 cmH2O significantly reduced SV and CI relative to baseline. There was no difference between TEB and PAC in terms of ability to assess variations in hemodynamic parameters. In patients with severe OSA (n = 3), CPAP titration to optimal pressure to alleviate obstructive apneas reduced HR, SV, CO and CI significantly compared to without CPAP. In three healthy subjects, maximal tolerated CPAP reduced SV and CO significantly compared to baseline.ConclusionsAcute administration of CPAP causes a decrease in CO and CI, apparently a consequence of a reduction in SV. TEB appears to be an accurate and reproducible non-invasive method of detecting changes in hemodynamics.

Comparison of transthoracic electrical bioimpedance cardiac output measurement with thermodilution method in post coronary artery bypass graft patients

Transthoracic electrical bioimpedance (TEB) has been proposed as a non-invasive, continuous, and cost-effective method of cardiac output (CO) measurement. In this prospective, non-randomized, clinical study, we measured CO with NICOMON (Larsen and Toubro Ltd., Mysore, India) and compared it with thermodilution (TD) method in patients after off-pump coronary artery bypass (OPCAB) graft surgery. We also evaluated the effect of ventilation (mechanical and spontaneous) on the measurement of CO by the two methods. Forty-six post-OPCAB patients were studied at five predefined time points during controlled ventilation and at five time points when breathing spontaneously. A total of 230 data pairs of CO were obtained. During controlled ventilation, TD CO values ranged from 2.29 to 6.74 L/min (mean 4.45 ± 0.85 L/min), while TEB CO values ranged from 1.70 to 6.90 L/min (mean 4.43 ± 0.94 L/min). The average correlation (r) was 0.548 (P = 0.0002), accompanied by a bias of 0.015 L/min and precision of 0.859 L/min. In spontaneously breathing patients, TD CO values ranged from 2.66 to 6.92 L/min (mean 4.66 ± 0.76 L/min), while TEB CO values ranged from 3.08 to 6.90 L/min (mean 4.72 ± 0.82 L/min). Their average correlation was relatively poor (r = 0.469, P= 0.002), accompanied by a bias of -0.059 L/min and precision of 0.818 L/min. The overall percent errors between TD CO and TEB CO were 19.3% (during controlled ventilation) and 17.4% (during spontaneous breathing), respectively. To conclude, a fair correlation was found between TD CO and TEB CO measurements among post-OPCAB patients during controlled ventilation. However, the correlation was weak in spontaneously breathing patients.

Transthoracic electrical bioimpedence cardiac output: comparison with multigated equillibrium radionuclide cardiography

Thoracic electrical bioimpedance (TEB) for measuring cardiac output (CO) is being explored increasingly as an alternative to pulmonary artery catheter. The major advantage of this technology is that it is non-invasive and easy to perform. Several studies have compared it to thermodilution cardiac output using PA catheter, with variable correlation. Multigated radionuclide equilibrium cardiography (RNEC) method of cardiac output measurement is known to be reliable. To compare cardiac output measured by thoracic electrical bioimpdenace with that measured by multigated radionuclide equilibrium cardiography. CO studies were performed sequentially at a single sitting by TEB and RNEC methods among patients with cardiac symptoms referred for radionuclide study as part of their evaluation. TEB CO was measured by placing two pairs of electrodes on either side of neck and two other pairs on either side of the lower chest. Stroke volume was estimated from the sequential changes in transthoracic electrical bioimpedance induced by rhythmic aortic blood flow, using Kubicek equation. RNEC-CO was measured by intravenous injection of radio-active Technitium-tagged RBCs followed by ECG gated blood pool imaging over the chest (MUGA study). Bland-Altman analysis was used to compare the measurements. A total of 32 subjects with proven or suspected ischemic heart disease, but without overt cardiac failure, edema or arrhythmias were studied (M:F::26:6; mean age: 48 +/- 12 years). The mean TEB-CO was 3.54 +/- 1.052 l/min and mean RNEC-CO was 3.907 +/- 0.952 l/min. Correlation coefficient (r) for these measurements was 0.67 (p < 0.01), with bias: -0.421 l/min; precision: 1.557 l/min; and percentage error of measurement: 42.35%. This study observed a moderate correlation between TEB and RNEC methods of CO measurement. Further studies are indicated to explore the relative utility of TEB in comparison with RNEC as well as other methods of CO measurement before considering its use in patients with ischemic heart disease.

Circulating and hepatic endocannabinoids and endocannabinoid-related molecules in patients with cirrhosis

Endocannabinoids include anandamide (AEA) and 2-arachidonoylglycerol (2-AG). Endocannabinoid-related molecules like oleoyl-ethanolamine (OEA) and palmitoyl-ethanolamine (PEA) have also been identified. AEA contributes to the pathogenesis of cardiovascular alterations in experimental cirrhosis, but data on the endocannabinoid system in human cirrhosis are lacking. Thus, we aimed to assess whether circulating and hepatic endocannabinoids are upregulated in cirrhotic patients and whether their levels correlate with systemic haemodynamics and liver function. The endocannabinoid levels were measured in peripheral and hepatic veins and liver tissue by isotope-dilution liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. Systemic haemodynamics were assessed by the transthoracic electrical bioimpedance technique. Portal pressure was evaluated by hepatic venous pressure gradient. Circulating AEA and, to a greater extent, PEA and OEA were significantly higher in cirrhotic patients than in controls. PEA and OEA were also increased in the cirrhotic liver tissue. AEA, OEA and PEA levels were significantly higher in peripheral than in the hepatic veins of cirrhotic patients, while the opposite occurred for 2-AG. Finally, circulating AEA, OEA and PEA correlated with parameters of liver function, such as serum bilirubin and international normalized ratio. No correlations were found with systemic haemodynamics. The endocannabinoid system is upregulated in human cirrhosis. Peripheral AEA is increased in patients with a high model of end-stage liver disease score and may reflect the extent of liver dysfunction. In contrast, the 2-AG levels, the other major endocannabinoid, are not affected by cirrhosis. The upregulation of the endocannabinoid-related molecules, OEA and PEA, is even greater than that of AEA, prompting pharmacological studies on these compounds.

Systemic hemodynamic effects of sequential pneumatic compression of the lower limbs: a prospective study in healthy volunteers

Study ObjectiveTo evaluate the effects on systemic hemodynamics of sequential pneumatic compression of the lower limbs in healthy volunteers. DesignProspective, self-controlled, volunteer study. SettingUniversity teaching hospital. Patients11 healthy volunteers, aged 25 ± 1.3 years. Interventions and MeasurementsAfter volunteers underwent a 6-hour period of fasting and 15 minutes of rest in the supine position, baseline systemic hemodynamics were assessed using transthoracic electrical bioimpedance. Peripheral venous pressure was measured using a 16-gauge intravenous cannula inserted in the forearm and connected to a pressure monitor. Then sequential pneumatic compression of the lower limbs was activated for a 30-minute period, and systemic hemodynamic measurements were repeated. In each volunteer, measurements were repeated twice in two consecutive days, and average values were calculated for each volunteer. Main ResultsAfter activation of sequential pneumatic compression of the lower limbs, mean arterial blood pressure increased from 90 mmHg (79-107 mmHg) to 95 mmHg (79-129 mmHg) (P = 0.02), whereas heart rate decreased from 79 bpm (51-94 bpm) to 75 bpm (53-90 bpm) (P = 0.02). This was associated with a significant increase in peripheral vascular resistance index (from 545 [440-1066] to 613 [369-1280] dynes s cm−5 m−2 [P = 0.013]) and reduction in cardiac index (from 3.4 [2.7- 4.5] to 3.2 [2.5-4.0] L/min per m2 [P = 0.034]). ConclusionsThe application of sequential pneumatic compression to the lower limbs is associated with minor increases in mean arterial blood pressure, with moderate reduction of cardiac output and heart rate.

Muscle circulation contributes to hyperdynamic circulatory syndrome in advanced cirrhosis

Muscle wasting likely influences blood flow to muscle districts in advanced cirrhosis. Thus, we assessed systemic hemodynamics and femoral artery blood flow corrected by muscle mass of the lower limb in 13 patients (Child-Pugh classes B and C) and 11 healthy controls. Systemic hemodynamics were assessed by transthoracic electrical bioimpedance, femoral artery blood flow by duplex-Doppler and muscle mass by magnetic resonance imaging. As expected, patients exhibited increased cardiac index and reduced peripheral vascular resistance. Femoral artery blood flow did not differ between patients and controls. However, when this parameter was indicized by the muscle mass of the lower limb, which was reduced in patients (median: 3391; range: [2546-4793] vs 5118 [3562-7077]cm3, p=0.0006), it proved almost doubled in patients (91.1 [59.9-119.4] vs 50.5 [38.6-69.8]microl/min cm3; p=0.0001). Patient femoral blood flow indicized by muscle mass correlated inversely with peripheral vascular resistance (r= -0.65; p=0.017) and directly with cardiac index (r=0.57; p=0.042). Vasodilation of muscle districts contributes to the reduced peripheral vascular resistance in advanced cirrhosis. Our findings provide a stronger rationale for the use of non-selective vasoconstrictors to treat hemodynamic-dependent complications of cirrhosis, such as hepatorenal syndrome.

Transthoracic electrical bioimpedance: A non-invasive technique for the evaluation of the haemodynamic alterations in patients with liver cirrhosis

Background/aim. Transthoracic electrical bioimpedance is a non-invasive technique for the evaluation of systemic haemodynamics. Compared to Doppler ultrasound, it has the advantage of being operator-independent, providing continuous monitoring and being less influenced by postural changes. Until now, transthoracic electrical bioimpedance has been applied to a very limited extent in liver cirrhosis. We, therefore, aimed to compare transthoracic electrical bioimpedance and echocardiography in the assessment of haemodynamic status in cirrhotic patients. Patients/methods. Thirteen patients with compensated cirrhosis, 10 patients with cirrhosis and ascites and 12 controls were enrolled. Haemodynamic parameters (stroke volume, cardiac output, heart rate, mean arterial pressure and vascular peripheral resistance) were assessed simultaneously by transthoracic electrical bioimpedance monitoring with BioZ.com™ for at least 10 min and Doppler ultrasound. Results. The absolute mean values of haemodynamic parameters obtained by the two techniques were quite similar in all groups; furthermore, a good agreement between transthoracic electrical bioimpedance and echocardiography measurements was found for all the parameters. Finally, transthoracic electrical bioimpedance proved easy to employ and provided continuous real-time monitoring of cardio-circulatory variations. Conclusions. The present study showed a significant correlation between transthoracic electrical bioimpedance and echocardiography in the assessment of systemic haemodynamics in patients with cirrhosis, supporting the employment of transthoracic electrical bioimpedance in pathophysiological studies requiring real-time continuous monitoring of haemodynamic parameters.

Transthoracic electrical bioimpedance: A means of filling the void?

To examine the published evidence regarding the use of transthoracic electric bioimpedance (TEB) for the non-invasive monitoring of cardiac output in the ED. Databases of the medical literature, relevant textbooks and the Internet were searched for articles regarding TEB. Criteria for inclusion were drawn up prior to examination of the articles and included adherence to guidelines for comparing methods of clinical measurement. Results are discussed under the following headings: technological capability, diagnostic accuracy, limitations, range of possible uses, therapeutic impact, impact on health care providers, patient outcome and future directions. TEB is a technique for the non-invasive monitoring of cardiac output whose ease of use, continuous data acquisition and versatility suggest it may have a role to play in the care of patients in our EDs.

Effect of fluid preload on maternal haemodynamics for low-dose epidural analgesia in labour

We prospectively studied 30 women in labour who requested epidural analgesia. They were randomly allocated into two groups; one received a preload of 7 mL/kg normal saline and the other no preload. All patients had a standard epidural solution consisting of 0.1% bupivacaine 20 mL containing fentanyl 2 μg/mL. Mean arterial blood pressure and cardiac index were measured serially for 20 min after epidural drug administration. Cardiac index was measured using transthoracic electrical bioimpedance (BOMED). Power calculation showed that a sample size of 30 had 80% power to detect a difference of more than 20% in cardiac index using a two-sided test at a significance level of <0.05. No significant changes in cardiac index or mean arterial pressure occurred at any time in either group. These results suggest that routine fluid preloading is not necessary for 0.1% bupivacaine 20 mL with fentanyl 2 μg/mL as epidural bolus in labour.

Cardiovascular effects of intravaginal misoprostol in the mid trimester of pregnancy

Objective: Our aim was to evaluate the cardiovascular effects of high-dose intravaginal misoprostol administration by means of transthoracic electrical bioimpedance monitoring. Study Design: Healthy women undergoing mid trimester pregnancy interruption with intravaginal misoprostol were eligible for this prospective observational study. Baseline blood pressure was obtained for 1 hour and transthoracic electrical bioimpedance monitoring was performed before misoprostol administration, 600 μg vaginally. Posttreatment assessments were made every 15 minutes for a total of 4 hours, with patients in a left lateral recumbent position. Heart rate, mean arterial pressure, cardiac index, stroke index, systemic vascular resistance index, and end-diastolic volume index were determined. Measurements were averaged for 30-minute intervals and reported as mean ± SD. Statistical analyses included the paired t test and repeated-measures analysis of variance. Results: Nine women consented to have transthoracic electrical bioimpedance monitoring, and no statistically significant changes in any of the measured cardiac parameters for the 4-hour monitoring interval were noted. Direct comparisons between the pretreatment and 2-hour posttreatment intervals (reported time peak of blood misoprostol levels) also revealed no significant differences in the cardiovascular index values. Conclusion: High-dose intravaginal misoprostol in the mid trimester does not alter maternal cardiac function as measured by transthoracic electrical bioimpedance. (Am J Obstet Gynecol 2000;183:1100-2.)

Epidural meperidine does not cause hemodynamic changes in the term parturient.

Meperidine has local anesthetic properties and, therefore, when given epidurally it has the potential to cause hemodynamic changes. Our objective was to study the hemodynamic effects of an analgesic dose of epidural meperidine (50 mg) in 34 ASA 1-2 term parturients scheduled for elective Cesarean section under epidural anesthesia. A lumbar epidural catheter was inserted and patients lay in the supine left wedge position. Intravenous fluid preload was withheld, and hemodynamic measurements comprising of mean arterial pressure, cardiac output and heart rate were made using automatic oscillotonometry (Dinamap 1486SX) and transthoracic electrical bioimpedance (Bomed NCCOM3). Following baseline measurements, the hemodynamic effects of sequential epidural injection of first, 10 ml saline, and 20 min thereafter, 50 mg meperidine diluted to 10 ml with saline, were recorded. Sensory blockade was assessed following each injection using loss of temperature discrimination to ice. Paired Student t tests were used to compare changes in hemodynamic variables. Epidural meperidine produced a small increase from the saline values in the mean (SD) cardiac output of 5.81 +/-1.44 to 6.04+/-1.54 L x min(-1) (P<0.05), and mean arterial pressure of 77.1+/-8.8 to 79.3+/-9.9 mm Hg (P<0.05). Sensory changes, the upper level of which ranged from L1 to T1, were detected in 94% of patients given epidural meperidine. Epidural saline injection had no such hemodynamic effects, but produced a detectable sensory level in two patients. Epidural meperidine, 50 mg, caused minimal hemodynamic changes in term parturients.

The effect of thoracentesis on lung function and transthoracic electrical bioimpedance

This study aimed to determine the relationship between improvement in lung function and changes in transthoracic electrical bioimpedance (TEB) after thoracentesis in patients with pleural effusions. Fifteen patients with pleural effusions due to either malignant ( n=8) or cardiac ( n=7) diseases were included. Pulmonary function was assessed before and after thoracentesis. During thoracentesis the patients were monitored with TEB. Using linear correlation analysis, the increases for each litre of aspirated thoracic fluid were: forced expiratory volume in 1 s (FEV 1) 0·26 l; forced vital capacity (FVC) 0·33 l; total lung capacity (TLC) 0·58; and the lung diffusing capacity ( D lCO); 2·4 ml min −1 mmHg −1. Baseline impedance increased by 2·3 Ohm l −1 aspirated thoracic fluid. The relative increase in baseline impedance was twice as high for patients with cancer as for patients with heart failure ( P<0·05). We found only minor changes in systolic blood pressure and mean arterial pressure. The improvements in diffusing capacity, airflow, and lung volumes after thoracentesis are correlated to an increase in baseline impedance, but changes are dependent on the primary disease.