ArticlePDF Available

Electric velocimetry and transthoracic echocardiography for noninvasive cardiac output monitoring in children after cardiac surgery

Authors:

Abstract

Objective: Assessment of cardiac output (CO) is essential in the management of children after cardiac surgery. Electric velocimetry (EV) is a newly developed monitoring method for CO and stroke volume (SV). However, applicability in a pediatric population, particularly after cardiac surgery, remains unclear. We sought to assess agreement of CO measured by EV and transthoracic Doppler echocardiography (TTE). Design: Prospective observational study. Setting: A cardiac intensive care unit (CICU) at a tertiary children’s hospital in Shizuoka, Japan. Patients and participants: Children <18-year-old admitted to the CICU after cardiac surgery. Intervention: All patients underwent measurement of SV and CO using EV and TTE between 1 to 3 days after surgery. Measurements and results: Thirty patients were analyzed. We collected data on patient demographics, body surface area, vital signs, SV, CO, laboratory examination, drugs used, and type or surgery. There were significant correlations between EV and TTE in SV and CO values (r=0.909, p<0.001 and r=0.831, p<0.001, respectively). Bland-Altman analysis showed a good agreement between EV and TTE in SV and CO values (bias 1.33 mL, 0.08 L/min, and 0.02 L/min/m2, respectively, and limits of agreement -8.59 to 9.93 mL and -0.97 to 1.05 L/min, respectively). Mean percentage error for SV and CO values between EV and TTE were 13.76% and 13.19%, respectively. Conclusions: There is good correlation and clinical agreement between EV and TTE in measuring SV and CO. Electric velocimetry can be used in the hemodynamic monitoring of children after cardiac surgery. © 2015, Indonesian Society of Critical Care Medicine. All rights reserved.
Original
Crit Care & Shock (2015) 18:36-42
Electric velocimetry and transthoracic echocardiography for non-
invasive cardiac output monitoring in children after cardiac surgery
Neurinda P. Kusumastuti, Masaki Osaki
Abstract
Objective: Assessment of cardiac output (CO) is
essential in the management of children after
cardiac surgery. Electric velocimetry (EV) is a
newly developed monitoring method for CO
and stroke volume (SV). However, applicability
in a pediatric population, particularly after
cardiac surgery, remains unclear. We sought to
assess agreement of CO measured by EV and
transthoracic Doppler echocardiography (TTE).
Design: Prospective observational study.
Setting: A cardiac intensive care unit (CICU) at
a tertiary children’s hospital in Shizuoka, Ja-
pan.
Patients and participants: Children <18-year-old
admitted to the CICU after cardiac surgery.
Intervention: All patients underwent measure-
ment of SV and CO using EV and TTE between
1 to 3 days after surgery.
Measurements and results: Thirty patients were
.
analyzed. We collected data on patient de-
mographics, body surface area, vital signs, SV,
CO, laboratory examination, drugs used, and
type or surgery. There were significant correla-
tions between EV and TTE in SV and CO val-
ues (r=0.909, p<0.001 and r=0.831, p<0.001, re-
spectively). Bland-Altman analysis showed a
good agreement between EV and TTE in SV
and CO values (bias 1.33 mL, 0.08 L/min, and
0.02 L/min/m2, respectively, and limits of
agreement -8.59 to 9.93 mL and -0.97 to 1.05
L/min, respectively). Mean percentage error for
SV and CO values between EV and TTE were
13.76% and 13.19%, respectively.
Conclusions: There is good correlation and clin-
ical agreement between EV and TTE in measur-
ing SV and CO. Electric velocimetry can be
used in the hemodynamic monitoring of chil-
dren after cardiac surgery.
Key words: Electric velocimetry, transthoracic echocardiography, non-invasive, hemodynamic monitoring,
cardiac output, post cardiac surgery children.
36
Crit Care & Shock 2015 Vol. 18 No. 2
Address for correspondence:
Neurinda P. Kusumastuti, MD
Division of Pediatric Critical Care, Department of Child
Health
Medical Faculty, Airlangga University - Dr. Soetomo Hospi-
tal, Surabaya, Indonesia
Email: neurindapermata@yahoo.com
From Department of Child Health, Medical Faculty, Airlangga
University - Dr. Soetomo Hospital, Surabaya, Indonesia (Neu-
rinda P. Kusumastuti), and Shizuoka Children’s Hospital,
Shizuoka, Japan (Masaki Osaki).
In the cardiac care unit and pediatric intensive care
unit the continuous monitoring of the cardiac out-
put (CO) is important in high-risk patients after
cardiac surgery, in patients with heart failure and
in the critically ill patients who require titration of
cardiovascular drugs and fluid interventions. (1,2)
Recently, minimally invasive and non-invasive
.
Introduction
methods of estimation of CO were developed to
overcome the limitations of the invasive nature of
pulmonary artery catheterization (PAC) and the
direct Fick method used for the measurement of
stroke volume (SV). (2,3) Impedance cardiography
is probably the only non-invasive technique in true
sense. It provides information about haemodynam-
ic status without the risk, cost and skills associated
with the other invasive or minimally invasive tech-
niques. (4)
Electric velocimetry (EV) is a form of thoracic
electrical bioimpedance (TEB) that is based on
changes of the orientation of erythrocytes in the
aorta during the cardiac cycle. Prior to opening of
the aortic valve, there is no blood flow in the aorta
and the erythrocytes assume a random orientation.
Immediately after aortic valve opening, the pulsa-
tile blood flow forces the red blood cells to align
parallel with the direction of flow. (5) This parallel
alignment in early systole, followed by their return
.
Crit Care & Shock 2015 Vol. 18 No. 2
37
to random alignment, causes a change in conduc-
tivity that can be used to measure the SV. (6)
Only few studies of CO measurement have been
done in infants and children after cardiac surgery
for congenital heart disease. These patients require
continuous, accurate, portable, easy-to-use, and op-
erator-independent monitoring to enable rapid and
appropriate treatment. For this reason, it is very
useful to study a tool that can be used in these pa-
tients, which is not invasive and can be used con-
tinuously to measure CO in order to perform effi-
cient measures in providing therapeutic interven-
tions.
The purpose of this study was to assess the agree-
ment of CO measurement by EV with non-invasive
determination of CO by transthoracic Doppler
echocardiography (TTE) in post-cardiac surgery
children.
Materials and Methods
This was a prospective observational study con-
ducted at Shizuoka Children’s Hospital, a tertiary
pediatric cardiac center in Japan, from September 1
to October 31, 2013. This study was approved by
the local institutional review board, and informed
consent was given by the parents of each patient.
Patients
All patients who underwent cardiac surgery and
were admitted to the Cardiac Intensive Care Unit
(CICU) during the study period were considered
for enrollment. Patients were included in the study
when they were less than 18-year-old, biventricu-
lar, and hemodynamically stable. Single-ventricle
patients or patients undergoing valve replacement
with a mechanical prosthesis were excluded. All
patients underwent both TTE and EV examinations
between the first and third day after surgery.
Measurements were made only once for each pa-
tient. Two pediatric cardiologists performed echo-
cardiography while EV was done.
Electric velocimetry
EV was performed using an Aesculon Mini®
(Osypka Medical, Berlin, Germany and La Jolla,
California, USA) velocimeter. Body surface area
was calculated as (height [cm] x weight [kg] /
3600)1/2. Two surface electrocardiography elec-
trodes were attached one to the left side of the neck
and one on the lower thorax. Heart rate, SV, CO,
and cardiac index were measured continuously.
Transthoracic Doppler echocardiography
TTE was performed using a Philips iE-33 echocar-
.
diography machine (Philips, Netherland) equipped
with a 12-4 MHz extended-frequency range. We
performed simultaneous measurement of left ven-
tricle outflow (LVO). The left ventricle SV was
calculated by measuring the left ventricle outflow
tract (LVOT) area and the amount of blood going
through this area (velocity time integral [VTI]).
The diameter of the LVOT (DLVOT) and VTI
values were taken from the average of two to three
measurements. Left ventricle SV was calculated
using the formula SV=(DLVOF/2)2 x π x VTI.
Cardiac output were then calculated using the for-
mula CO (L/min)=SV x heart rate.
Data analysis
We calculated means and standard deviations for
quantitative data and also frequencies for qualita-
tive data. The correlation between EV and TTE
was determined using Pearson correlation. The
Bland-Altman method was used to analyze the lim-
its of agreement (bias±precision) between TTE and
EV. We also calculated the mean percentage error.
The mean percentage error (MAPE) was calculated
using the equation {2xSD mean difference/[(mean
from EV + mean from TTE) /2] x 100}. A MAPE
of less than 30% was considered clinically ac-
ceptable. (7) Data analysis was performed using
Microsoft Excel (Microsoft Inc., Redmond, Wash-
ington) and SPSS 20.0 (SPSS Inc., Chicago, Illi-
nois).
Results
Fifty-seven pediatric patients underwent cardiac
surgery during the study period. Among these, 30
patients met the inclusion criteria and were all en-
rolled in the study. The clinical characteristics of
these 30 patients are shown in Table 1. Both TTE
and EV were performed in all patients.
More than 50% of the patients were still on hemo-
dynamic support and sedation drugs while exam-
ined, although in minimal doses. Each patient used
a combination of several hemodynamic support or
sedation drugs. Vital signs, laboratory results,
haemodynamic support, and sedative medications
used are summarized in Table 2.
The scatter plot in Figure 1 shows the simulta-
neously obtained measurements of CO and SV by
EV and TTE. There was a strong and significant
correlation between these two techniques (r=0.909,
p<0.001 for SV and r=0.831, p<0.001 for CO).
Figure 2A and 2B shows the 95% limits of agree-
ment between TTE and EV in SV measurement
using Bland-Altman analysis. The mean difference
(bias) between the two methods in SV measure-
ment was 1.33 mL, with 95% limits of agreement
.
38
Crit Care & Shock 2015 Vol. 18 No. 2
of -8.59 to 9.93 mL and a MAPE of 13.76%. For
CO measurement, the mean difference was 0.08
l/min, 95% limits of agreement was -0.97 to 1. 05
L/min, and the MAPE was 13.19%. The mean
difference for cardiac index was 0.02 L/min, 95%
limits of agreement were -2.19 to -2.21 L/min, and
the MAPE was 12.79%.
Discussion
The present study demonstrated a good correlation
between SV and CO values measured by EV or
TTE in pediatric patients after cardiac surgery.
Both EV and TTE are non-invasive and reliable,
but EV is easier to use and operator-independent.
We used echocardiography as a reference, which
has a precision of about 30% and a 10% bias com-
pared to PAC. (8) Values obtained by EV tend to
be under- or overestimations compared to TTE. SV
measured by EV can be up to 8.59 mL below or up
to 9.93 mL above the values obtained by TTE.
This suggests that there is a wide variation in the
agreement between each data pair. While an EV
value of CO is not too much different, its value can
be up to 0.97 L/min below or up to 1.05 L/min
above the TTE value. Our data shows that this
study has an excellent accuracy bias in CO with
values of only 0.08 L/min, using echocardiography
as the reference device. Calculation of SV and CO
values from these two methods has a good MAPE
of <30% (13.76% and 13.19%, respectively).
Almost all subjects were still using continuous se-
dation at the time of study, with any combination
of midazolam, dexmedethomidhine, and fentanyl
infusion. As a result, there was no increase in CO
due to manipulation, which was seen in the stable
heart rate and blood pressure during the examina-
tion process.
Several studies have compared EV with various
tools as a reference. Some of these studies support
the results of our study. However, we found no
previous study assessing the agreement between
EV and TTE with similar value limits. A study in
newborns with transposition of the great arteries
after cardiac surgery showed that the bias (0.71
L/min) and limits of agreement (-0.59 to 2.02 mL)
for SV measurement by EV versus Doppler-TTE
were acceptable, with an overall average error of
29%. (8)
A comparative study of the use of Doppler-trans-
.
esophageal echocardiography (TEE) and EV to
TTE as the reference for measuring SV and CO in
pediatric post-cardiac surgery patients who were
hemodynamically stable and still on ventilator
showed a good correlation between EV and TTE.
The study also found that EV underestimated CO
in terms of absolute values in comparison with
TTE. The percentage of error was more than 30%.
The authors argue that Doppler-TEE and EV are
better tools for monitoring cardiac function trends
than for determining the absolute values. (9)
A study in 2012, using electrocardiometry (as the
test method) and TTE (as the reference) in obese
children and adolescents, showed that electrocardi-
ometry is reliable and accurate in measuring CO.
(6)
Measurement of CO in 32 infants, children, and
adolescents with congenital heart disease using EV
and direct Fick-oxygen showed an excellent corre-
lation (r=0.97, p=0.001). This study suggests that
the variation of the anatomical position of the great
thoracic vessels in congenital heart disease do not
affect the accuracy of EV measurements. (10)
However, several other studies do not support our
results. Tomaske et al. in 2009 found unacceptable
limits of agreement between EV and thermodilu-
tion, with a 48.9% error. Although the bias for CO
values between the Aesculon monitor and subxy-
phoidal Doppler flow measurements in the study
was 0.31 L/min, CO values obtained by Aesculon
monitor and subxyphoidal Doppler flow differed
significantly (p=0.04). (11)
The use of EV as a hemodynamic monitoring de-
vice remains the subject of controversy. More stud-
ies in pediatric patients are needed, since electrode
placement may influence the signal quality and re-
liability of this method, especially in newborns and
small children. Because it is easy to use, this tool is
worth for additional critical and detailed evalua-
tion, especially in smaller children, before we can
use it routinely in the clinical pediatric ICU setting.
Acknowledgements
The authors have disclosed no potential conflict of
interest.
We acknowledge the following person for their
contributions to our study: Miyakoshi Chisato, MD
and Prof. PJ Van den Broek for reviewing this
manuscript and making helpful suggestions.
Table 1. Characteristics of study subjects
39.50
19 (63.3)
11 (37.7)
76.19 (26.18)
10.62 (11.28)
0.46 (0.29)
11.86 (6.01)
1.04
4
9
2
3
1
4
3
2
2
Table 2. Vital signs, laboratory results, and treatment received
Characteristic
Hemoglobin (g/dl) (mean, SD)
O2 saturation (%) (mean, SD)
Systole (mmHg) (mean, SD)
Diastole (mmHg) (mean, SD)
Use of hemodynamic support (n, %)
o Dopamine/dobutamine
o Adrenaline
o Sodium nitroprusside
o Human atrial natriuretic peptide
Sedation
o Fentanyl
o Midazolam
o Dexmedetomidine
14.39 (2.46)
97.67 (3.37)
88.80 (18.86)
55.37 (12.89)
17 (56.67)
17
2
8
3
9
11
17
Crit Care & Shock 2015 Vol. 18 No. 2
39
Figure 1. Scatterplot showing pearson’s correlation between TTE and EV in the measurement of SV and
CO
40
Crit Care & Shock 2015 Vol. 18 No. 2
Figure 2A. Bland-Altman plot for SV shows a mean difference between the results of TTE and EV with
bias of 1.33 L/min and limit of agreement from -8.59 to 9.93 L/min
Figure 2B. Bland-Altman plot for CO shows a mean difference between the results of TTE and EV with
bias of 0.08 L/min and limit of agreement from -0.97 to 1.05 L/min
Crit Care & Shock 2015 Vol. 18 No. 2
41
42
Crit Care & Shock 2015 Vol. 18 No. 2
1. Berton C, Cholley B. Equipment review: New
techniques for cardiac output measurement
oesophageal Doppler, Fick principle using car-
bon dioxide, and pulse contour analysis. Crit
Care 2002;6:216-21.
2. Critchley LA, Critchley JA. A meta-analysis of
studies using bias and precision statistics to
compare cardiac output measurement tech-
niques. J Clin Monit Comput 1999;15:85-91.
3. Lavdaniti M. Invasive and non-invasive meth-
ods for cardiac output measurement. Int J Car-
ing Sci 2008;1:112-7.
4. Mathews L, Singh RK. Cardiac output moni-
toring. Ann Card Anaesth 2008;11:56-68.
5. Osypka M. An introduction to electrical cardi-
ometry. Electrical Cardiometry 2009;1-10.
6. Rauch R, Welisch E, Lansdell N, Burrill E,
Jones J, Robinson T, et al. Non-invasive meas-
urement of cardiac output in obese children
and adolescents: comparison of electrical car-
diometry and transthoracic doppler echocardi-
ography. J Clin Monit Comput 2013;27:187-
93.
7. Chew MS, Poelaert J. Accuracy and repeata-
bility of pediatric cardiac output measurement
.
using Doppler: 20-year review of the literature.
Intensive Care Med 2003;29:1889-94.
8. Grollmuss O, Demontoux S, Capderou A, Ser-
raf A, Belli E. Electrical velocimetry as a tool
for measuring cardiac output in small infants
after heart surgery. Intensive Care Med 2012;
38:1032-9.
9. Schubert S, Schmitz T, Weiss M, Nagdyman
N, Huebler M, Alexi-Meskishvili V, et al.
Continuous, non-invasive techniques to deter-
mine cardiac output in children after cardiac
surgery: evaluation of transesophageal doppler
and electric velocimetry. J Clin Monit Comput
2008;22:299-307.
10. Norozi K, Beck K, Osthaus WA, Wille I, Wes-
sel A, Bertram H. Electrical velocimetry for
measuring cardiac output in children with con-
genital heart disease. Br J Anaesth 2008;100:
88-94.
11. Tomaske M, Knirsch W, Kretschmar O, Bal-
mer C, Woitzek K, Schimtz A, et al. Evalua-
tion of the Aesculon cardiac output monitor by
subxiphoidal Doppler flow measurement in
children with congenital heart defects. Eur J
Anaesthesiol 2009;26:412-5.
References
... Those full-text articles were assessed for eligibility, which led to 24 included studies and 17 excluded studies [18,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67]. The included studies were divided into 13 studies in adults [28][29][30][31][32][33][34][35][36][37][38][39][40] and 11 studies in pediatrics [41][42][43][44][45][46][47][48][49][50][51]. Contacting the manufacturer and screening of the reference lists of all included studies led to no additional studies. ...
... Concerning adult studies; two were conducted in the OR during liver transplantation surgery [31,39], three during cardiac surgery [28,29,36], two both during cardiac surgery and post cardiac surgery in the ICU [30,33], two in the ICU [35,40], three in the cardiology unit [34,37,38] and one in the outpatient unit [32]. Concerning pediatric studies; four were conducted in the OR [45,47,49,50], two in the ICU [43,44], two in the neonatal intensive care unit (NICU) [46,51], and three in the outpatient unit [41,42,48]. The ICON ® device was used in nine studies [28, 29, 31, 32, 41-43, 45, 48] and the Aesculon ® in fifteen studies [30, 33-40, 44, 46, 47, 49-51]. ...
... The risk of bias in individual studies was high in the statistical analysis domain (Tables 3, 4), which is a limitation of this review too. First, in some studies, the direction of the bias was unclear [28,29,40,44,47]. Second, the SD described in the manuscript did not correspond with the LoA in the figure [28,29,43]. ...
Article
Full-text available
Cardiac output monitoring is used in critically ill and high-risk surgical patients. Intermittent pulmonary artery thermodilu-tion and transpulmonary thermodilution, considered the gold standard, are invasive and linked to complications. Therefore, many non-invasive cardiac output devices have been developed and studied. One of those is electrical cardiometry. The results of validation studies are conflicting, which emphasize the need for definitive validation of accuracy and precision. We performed a database search of PubMed, Embase, Web of Science and the Cochrane Library of Clinical Trials to identify studies comparing cardiac output measurement by electrical cardiometry and a reference method. Pooled bias, limits of agreement (LoA) and mean percentage error (MPE) were calculated using a random-effects model. A pooled MPE of less than 30% was considered clinically acceptable. A total of 13 studies in adults (620 patients) and 11 studies in pediatrics (603 patients) were included. For adults, pooled bias was 0.03 L min −1 [95% CI − 0.23; 0.29], LoA − 2.78 to 2.84 L min −1 and MPE 48.0%. For pediatrics, pooled bias was − 0.02 L min −1 [95% CI − 0.09; 0.05], LoA − 1.22 to 1.18 L min −1 and MPE 42.0%. Inter-study heterogeneity was high for both adults (I 2 = 93%, p < 0.0001) and pediatrics (I 2 = 86%, p < 0.0001). Despite the low bias for both adults and pediatrics, the MPE was not clinically acceptable. Electrical cardiometry cannot replace thermodilution and transthoracic echocardiography for the measurement of absolute cardiac output values. Future research should explore it's clinical use and indications.
Article
Objective: To systematically review and meta-analyze the validity of electrical bioimpedance-based noninvasive cardiac output monitoring in pediatrics compared with standard methods such as thermodilution and echocardiography. Data sources: Systematic searches were conducted in MEDLINE and EMBASE (2000-2019). Study selection: Method-comparison studies of transthoracic electrical velocimetry or whole body electrical bioimpedance versus standard cardiac output monitoring methods in children (0-18 yr old) were included. Data extraction: Two reviewers independently performed study selection, data extraction, and risk of bias assessment. Mean differences of cardiac output, stroke volume, or cardiac index measurements were pooled using a random-effects model (R Core Team, R Foundation for Statistical Computing, Vienna, Austria, 2019). Bland-Altman statistics assessing agreement between devices and author conclusions about inferiority/noninferiority were extracted. Data synthesis: Twenty-nine of 649 identified studies were included in the qualitative analysis, and 25 studies in the meta-analyses. No significant difference was found between means of cardiac output, stroke volume, and cardiac index measurements, except in exclusively neonatal/infant studies reporting stroke volume (mean difference, 1.00 mL; 95% CI, 0.23-1.77). Median percentage error in child/adolescent studies approached acceptability (percentage error less than or equal to 30%) for cardiac output in L/min (31%; range, 13-158%) and stroke volume in mL (26%; range, 14-27%), but not in neonatal/infant studies (45%; range, 29-53% and 45%; range, 28-70%, respectively). Twenty of 29 studies concluded that transthoracic electrical velocimetry/whole body electrical bioimpedance was noninferior. Transthoracic electrical velocimetry was considered inferior in six of nine studies with heterogeneous congenital heart disease populations. Conclusions: The meta-analyses demonstrated no significant difference between means of compared devices (except in neonatal stroke volume studies). The wide range of percentage error reported may be due to heterogeneity of study designs, devices, and populations included. Transthoracic electrical velocimetry/whole body electrical bioimpedance may be acceptable for use in child/adolescent populations, but validity in neonates and congenital heart disease patients remains uncertain. Larger studies in specific clinical contexts with standardized methodologies are required.
Article
Full-text available
The objective of this study was to evaluate the reliability and accuracy of electrical cardiometry (EC) for the noninvasive determination of cardiac output (CO) in obese children and adolescents. We compared these results with those obtained by transthoracic echocardiography. Sixty-four participants underwent simultaneous measurement of CO. Cardiac output was measured by EC using the ICON(®) device. Simultaneously CO was determined by using transthoracic Doppler echocardiography from parasternal long-axis and apical view. The median age was 12.52 years (range 7.9-17.6 years) and 36 (56 %) were female. A strongly significant correlation was found between the CO(EC) and CO(Echo) measurements (p < 0.0001, r = 0.91). Significant correlations were also found between CO and age (r = 0.37, p = 0.002), weight (r = 0.57, p < 0.0001), height (0.60, p < 0.0001) and BMI (r = 0.42, p = 0.001). The mean difference between the two methods (CO(EC) - CO(Echo)) was 0.015 l min(-1). According to the Bland and Altman method, the upper and lower limits of agreement, defined as mean difference ±2 SD, were +1.21 and -0.91 l min(-1), respectively. Compared to the transthoracic Doppler echocardiography, Electrical Cardiometry provides accurate and reliable CO measurements in obese children and adolescents.
Article
Full-text available
Cardiac output (CO), the product of stroke volume (SV) and heart rate, is essential to guarantee organ perfusion, especially in the intensive care setting. As invasive measurement of CO bears the risk of complications there is a need for non-invasive alternatives. We investigated if electrical velocimetry (EV) and transthoracic Doppler (Doppler-TTE) are interchangeable for the non-invasive measurement of SV and able to reflect the post-surgical SV/CO trend. Comparison of SV measurements by EV and Doppler-TTE was performed in 24 newborns after switch operation (n = 240 measurements). Three subgroups of measurements (=periods) were created according to the patients' status in the course of post-surgical CO recovery. Bland-Altman analysis found acceptable bias and limits of agreement for the interchangeability of the two methods. Mean overall SV was 3.7 ml with a mean overall bias of 0.28 ml (=7.6 %). The mean percentage error of 29 % was acceptable according to the method of Critchley and Critchley. Overall precision expressed by the coefficient of variation (CV) was 6.6 % for SV(TTE) and 4.4 % for SV(EV). SV(TTE) and SV(EV) medians in the three periods were significantly different and documented the post-surgical CO trend. EV and Doppler-TTE are interchangeable for estimating SV. EV has the advantages of easy handling and allows continuous measurement.
Article
Full-text available
The hemodynamic status monitoring of high-risk surgical patients and critically ill patients inIntensive Care Units is one of the main objectives of their therapeutic management. Cardiac output is one of the mostimportant parameters for cardiac function monitoring, providing an estimate of whole body perfusion oxygen deliveryand allowing for an understanding of the causes of high blood pressure. The purpose of the present review is thedescription of cardiac output measurement methods as presented in the international literature. The articles documentthat there are many methods of monitoring the hemodynamic status of patients, both invasive and non-invasive, themost popular of which is thermodilution. The invasive methods are the Fick method and thermodilution, whereasthe non-invasive methods are oeshophaegeal Doppler, transoesophageal echocardiography, lithium dilution, pulsecontour, partial CO2 rebreathing and thoracic electrical bioimpedance. All of them have their advantages and disadvantages,but thermodilution is the golden standard for critical patients, although it does entail many risks. The idealsystem for cardiac output monitoring would be non-invasive, easy to use, reliable and compatible in patients. A numberof research studies have been carried out in clinical care settings, by nurses as well as other health professionals, for thepurpose of finding a method of measurement that would have the least disadvantages. Nevertheless, the thermodilutiontechnique remains the most common approach in use today.
Article
Full-text available
Continuous and non-invasive measurement of cardiac output (CO) may contribute helpful information to the care and treatment of the critically ill pediatric patient. Different methods are available but their clinical verification is still a major problem. Comparison of reliability and safety of two continuous non-invasive methods with transthoracic echocardiography (TTE) for CO measurement: electric velocimetry technique (EV, Aesculon) and transesophageal Doppler (TED, CardioQP). METHODS/MATERIAL: In 26 infants and children who had undergone corrective cardiac surgery at a median age of 3.5 (1-17) years CO and stroke volume (SV) were obtained by EV, TED and TTE. Each patient had five measurements on the first day after surgery, during mechanical ventilation and sedation. Values for CO and SV from TED and EV correlated well with those of TTE (r = 0.85 and r = 0.88), but mean values were significantly lower than the values of TTE for TED (P = 0.02) and EV (P = 0.001). According to Bland-Altman analysis, bias was 0.36 l/min with a precision of 1.67 l/min for TED vs. TTE and 0.87 l/min (bias) with a precision of 3.26 l/min for EV vs. TTE. No severe adverse events were observed and the handling of both systems was easy in the sedated child. In pediatric patients non-invasive measurement of CO and SV with TED and EV is useful for continuous monitoring after heart surgery. Both new methods seem to underestimate cardiac output in terms of absolute values. However, TED shows tolerable bias and precision and may be helpful for continuous CO monitoring in a deeply sedated and ventilated pediatric patient, e.g. in the operating room or intensive care unit.
Article
Full-text available
The purpose of this study was to evaluate the agreement of cardiac output measurements obtained by electrical velocimetry (CO(EV)) and those that derived from the direct Fick-oxygen principle (CO(F)) in infants and children with congenital heart defects. Simultaneous measurements of CO(EV) and CO(F) were compared in 32 paediatric patients, aged 11 days to 17.8 yr, undergoing diagnostic right and left heart catheterization. For non-invasive measurements of cardiac output by electrical velocimetry, which is a variation of impedance cardiography, standard surface electrodes were applied to the left side of the neck and the left side of the thorax at the level of the xiphoid process. Cardiac output determined using direct Fick-oxygen principle was calculated by direct measurement of oxygen consumption (VO2) and invasive determination of the arterio-venous oxygen content difference. An excellent correlation (r=0.97) was found between CO(EV) and CO(F) (P<0.001). The slope of the regression equation [0.96 (SD 0.04)] was not significantly different from the line of identity. The bias between the two methods (CO(EV)-CO(F)) was 0.01 litre min(-1) and the limits of agreement, defined as the bias (2 SD), were -0.47 and +0.45 litre min(-1). CO(EV) demonstrates acceptable agreement with data derived from CO(F) in infants and children with congenital heart disease. The new technique is simple, completely non-invasive, and provides beat-to-beat estimation of CO.
Article
Measuring cardiac output is of paramount importance in the management of critically ill patients in the intensive care unit and of 'high risk' surgical patients in the operating room. Alternatives to thermodilution are now available and are gaining acceptance among practitioners who have been trained almost exclusively in the use of the pulmonary artery catheter. The present review focuses on the principles, advantages and limitations of oesophageal Doppler, Fick principle applied to carbon dioxide, and pulse contour analysis. No single method stands out or renders the others obsolete. By making cardiac output easily measurable, however, these techniques should all contribute to improvement in haemodynamic management.
Article
Bias and precision statistics have succeeded regression analysis when measurement techniques are compared. However, when applied to cardiac output measurements, inconsistencies occur in reporting the results of this form of analysis. A MEDLINE search was performed, dating from 1986. Studies comparing techniques of cardiac output measurement using bias and precision statistics were surveyed. An error-gram was constructed from the percentage errors in the test and reference methods and was used to determine acceptable limits of agreement between methods. Twenty-five articles were found. Presentation of statistical data varied greatly. Four different statistical parameters were used to describe the agreement between measurements. The overall limits of agreement in studies evaluating bioimpedance (n = 23) was +/-37% (15-82%) and in those evaluating Doppler ultrasound (n = 11) +/-65% (25-225%). Objective criteria used to assess outcome were given in only 44% of the articles. These were (i) limits of agreement approaching +/-15-20%, (ii) limits of agreement of less than 1 L/min, and (iii) more than 75% of bias measurements within +/-20% of the mean. Graphically, we showed that limits of agreement of up to +/-30% were acceptable. When using bias and precision statistics, cardiac output, bias, limits of agreement, and percentage error should be presented. Using current reference methods, acceptance of a new technique should rely on limits of agreement of up to +/-30%.
Article
Review of the accuracy and repeatability of Doppler cardiac output (CO) measurements in children. Publications in the scientific literature retrieved using a computerized Medline search from 1982-2002 and a manual review of article bibliographies. Studies comparing Doppler flow measurements with thermodilution, Fick, or dye dilution methods in the pediatric critical care setting were identified to assess the bias, precision, and intra- and interobserver repeatability of Doppler CO measurement. Where results were not suitable for comparison and the original measurements available, data were re-analyzed using appropriate statistical methods and presented in comparative tables. The precision of pediatric Doppler CO measurements compared to thermodilution, dye dilution, or Fick methods is around 30% and repeatability varies from less than 1% to 22%. Bias is generally less than 10% but varies considerably. The bias, precision, and repeatability from study to study indicate that Doppler CO measurements are acceptably reproducible in children, with best results when used to track changes rather than absolute values, and using the transesophageal approach.
Article
Minimally invasive and non-invasive methods of estimation of cardiac output (CO) were developed to overcome the limitations of invasive nature of pulmonary artery catheterization (PAC) and direct Fick method used for the measurement of stroke volume (SV). The important minimally invasive techniques available are: oesophageal Doppler monitoring (ODM), the derivative Fick method (using partial carbon dioxide (CO2 ) breathing), transpulmonary thermodilution, lithium indicator dilution, pulse contour and pulse power analysis. Impedance cardiography is probably the only non-invasive technique in true sense. It provides information about haemodynamic status without the risk, cost and skill associated with the other invasive or minimally invasive techniques. It is important to understand what is really being measured and what assumptions and calculations have been incorporated with respect to a monitoring device. Understanding the basic principles of the above techniques as well as their advantages and limitations may be useful. In addition, the clinical validation of new techniques is necessary to convince that these new tools provide reliable measurements. In this review the physics behind the working of ODM, partial CO2 breathing, transpulmonary thermodilution and lithium dilution techniques are dealt with. The physical and the physiological aspects underlying the pulse contour and pulse power analyses, various pulse contour techniques, their development, advantages and limitations are also covered. The principle of thoracic bioimpedance along with computation of CO from changes in thoracic impedance is explained. The purpose of the review is to help us minimize the dogmatic nature of practice favouring one technique or the other.
An introduction to electrical cardiometry
  • M Osypka
Osypka M. An introduction to electrical cardiometry. Electrical Cardiometry 2009;1-10.