During pediatric cardiac surgery, an accurate determination of the patient’s volume status, and the choice of an appropriate fluid management strategy are important factors leading to a stable hemodynamic status and thus a better clinical outcome. These considerations are even more important than in adult cardiac surgery, due to the potential for large fluid shifts compared with the pediatric patient’s small body surface area [
In adult patients, volume status is traditionally evaluated by measuring the central venous pressure (CVP) or pulmonary capillary wedge pressure (PCWP) in the past. It is now widely demonstrated that cardiac filling pressures could not reliably predict fluid responsiveness. CVP also has been widely used to estimate the intravascular volume status of pediatric patients because of any other suitable alternative parameter for fluid status. However, as an indicator of exact volume status its use in this population is inappropriate, due to various factors that affect its accuracy, such as venous capacitance, cardiac chamber compliance, cardiac valve competence, and pulmonary artery pressure [
In pediatric patients undergoing a Fontan procedure, the exact volume status cannot be determined based on the CVP value, because the latter is actually the postoperative pulmonary arterial pressure following bidirectional cavopulmonary shunt (BCPS). The development of a good indicator of the volume status of pediatric patients will allow fluid management in those undergoing a Fontan procedure.
The thoracic fluid content (TFC) and its percent change compared to the baseline (TFCd0%) are derived from the application of a bioreactance technique performed using a noninvasive cardiac output monitoring (NICOM) device. The values obtained with this method correlate well with the amount of fluid removal in patients undergoing hemodialysis [
This study was approved by the Institutional Review Board of Konkuk University Medical Center, Seoul, South Korea [KUH1160103, (Aug, 2016)], and subsequently registered at
Anesthesia induction and maintenance were performed according to the institutional standard regimen for pediatric cardiac surgery: sufentanil-based anesthesia with sevoflurane. Anesthesia induction was followed by invasive arterial pressure monitoring at radial artery and central venous catheterization for CVP monitoring at internal jugular vein. Mean arterial pressure (MAP) and CVP were measured using pressure transducers (PX600F, Edwards Lifesciences, Irvine, CA, USA), which were placed on the patient at the level of the mid-axillary line under the guidance of a laser leveler (Physiotrac, Edwards Lifesciences) and then fixed to the operation table. Two NICOM electrode strips (right and left) were then placed on each side of the chest of the patient and connected to a NICOM controller (NICOM, Cheetah Medical, Vancouver, WA, USA). Each electrode strip consisted of upper and lower contact points. The upper thoracic electrode strips were placed at the mid-subclavian region and the lower electrode strips in the middle region of the lower costal margin. After an initial calibration of the electrodes, hemodynamic variables, including cardiac output (CO), cardiac index (CI), stroke volume (SV), and stroke volume variation (SVV), were monitored continuously and recorded every 10 min until just before the patient was transported to the intensive care unit (ICU). After surgical procedure was over, the patients were transported to the ICU with intubation status.
The system’s signal processing unit determines the relative phase shift (
The water content of the body, whether in the blood (intravascular) or outside the blood (extravascular), contains high concentrations of various electrolytes, such as sodium, chloride, potassium, and calcium. These electrolytes are good conductors of electricity. The more fluid a patient has in his/her chest, the more electrolytes are available for electrical conductance and vice versa. Thoracic fluid content (TFC) is calculated as TFC =
Among the intraoperative variables, those recorded at two time points were used in the analysis: the NICOM data obtained just after anesthesia induction (
Cardiac surgery procedures were performed by a single pediatric cardiac surgery team. CPB was performed by a single perfusionist on that team. All patients included in the study underwent an extracardiac Fontan procedure.
The patient’s body weight was measured twice, according to the standard protocol for pediatric cardiac surgery at our institution. After anesthesia induction with routine invasive (arterial blood pressure) and noninvasive patient (pulse oximetry, electrocardiography) monitoring, a central venous catheter and a urinary catheter were inserted and the electrode strips of the NICOM were attached. The patient’s body weight was then measured using portable scales (SW-30H, CAS, Yang-ju, Republic of Korea). This was the
Statistical analyses were conducted using SigmaStat software (ver. 3.1; SYSTAT Software, San Jose, CA, USA). Continuous variables were analyzed using the paired
From April 2011 to December 2015, data from the medical records of 22 patients were collected. One patient was excluded for incomplete medical records. The preoperative demographic profiles of the 21 patients included in the study are summarized in Table
Patient demographic characteristics.
Subjects | |
---|---|
Age (months) | |
Gender (M/F) | 8/13 |
Height (cm) | |
Weight (kg) | |
Body mass index | |
Values are presented as mean ± SD or numbers of patients.
There were no differences in MAP, CO, and CI at
Comparisons of parameters between
| | | |
---|---|---|---|
MAP (mmHg) | | | 0.078 |
HR (beats per min) | | | <0.001 |
CVP (mmHg) | | | <0.001 |
CO (L/min) | | | 0.235 |
CI (L/min/m2) | | | 0.181 |
TFC (1/Ω) | | | <0.001 |
SVV (%) | | | 0.009 |
Body weight (kg) | | | <0.001 |
Values are presented as means ± SD;
The body weight gain was
Perioperative parameters.
Subject | |
---|---|
Op time (min) | |
Anesthesia time (min) | |
Weight gain (g) | |
Weight gain% (%) | |
Intake/output (ml) | |
Change of CVP value (mmHg) | |
ΔTFC (1/Ω) | |
TFCd0% at discharge (%) | |
SVV at discharge (%) | |
Values are presented as means ± SD. Op, operation; Intake/output, intraoperative fluid balance; ΔTFC, change of thoracic fluid content compared with baseline value; TFCd0%, percentage of change compared with thoracic fluid content at baseline; CVP, central venous pressure; SVV, stroke volume variation.
The patients were divided into low and high TFCd0% groups based on a mean TFCd0% value at
Comparisons of parameters between low TFCd0% group versus high TFCd0% group.
Low TFCd0% group | High TFCd0% group | | |
---|---|---|---|
Body weight gain (g) | | | 0.025 |
Body weight gain% (%) | | | 0.023 |
Intraop. fluid balance (ml) | | | 0.035 |
Absolute CVP value (mmHg) | | | 0.22 |
Change of CVP value (mmHg) | | | 0.758 |
ΔTFC (1/Ω) | | | 0.009 |
Values are presented as means ± SD;
The correlation coefficient between TFCd0% and body weight gain was 0.546 (
The coefficient of determination (
Linear regression analysis between TFCd0% and body weight gain ((a),
Linear regression analysis between ΔTFC and body weight gain ((a),
Linear regression analysis between the change in the CVP value and body weight gain ((a),
Linear regression analysis between body weight gain and intraoperative fluid balance (
In the present study, the values of the correlation coefficients derived from the correlation analyses were acceptable, with the strongest correlations between TFCd0% and body weight gain and between body weight gain% and intraoperative fluid balance. The coefficients of determination derived in the linear regression analysis were also acceptable, with the highest being those between TFCd0% and body weight gain and between body weight gain% and intraoperative fluid balance. Because the intraoperative fluid balance is almost the only factor that affects patients’ body weight and the result derived from linear regression analysis between body weight gain and intraoperative fluid balance showed high correlation coefficient, these findings suggest that TFCd0% is an appropriate indicator for intraoperative fluid management in pediatric patients undergoing a Fontan procedure.
In pediatric patients with congenital heart disease who are undergoing surgery, CVP is an inappropriate parameter for estimating the exact volume status. This can be explained by factors such as intracardiac shunt (left to right or right to left), altered pulmonary vascular resistance, altered left ventricular and right ventricular compliance, and the complex anatomy that often occurs in congenital heart disease [
In comparisons of the variables between
Prior to undergoing a Fontan procedure, most patients have already been treated surgically and have a postoperative status of BCPS. This was the case in the present study, in which all of the patients had previously undergone a BCPS procedure. Therefore, the CVP value was instead a measurement of the pulmonary artery pressure (PAP), both before and after surgery. In the determination of PAP, pulmonary vascular resistance is the important factor; however, it is also affected by other factors and, thus, does not reflect the exact volume status of the patient.
The patients were divided into two groups based on the value of TFCd0% 30% at
In a previous study, TFCd0% correlated well with intraoperative fluid balance and with body weight gain, based on correlation coefficients of ~0.7 [
Among the limitations of the present study was its retrospective design. A prospective study would be able to clarify the relationships between the variables. However, the present study has been performed as retrospective design. Although all the medical records were reviewed carefully, the limitations inherent in a retrospective study were inevitable. In addition, TFCd0% detects the changes in intra- and extravascular volume status based on the electrical conductance in the patient’s chest, but it does not distinguish intravascular from extravascular volume change. However, when a large amount of fluid is administered to maintain a stable hemodynamic state, large fluid shift to the third space and tissue edema occurs more often than otherwise. In this case, since TFCd0% reflects the intraoperative fluid balance well, the measurement of TFCd0% can be useful to detect and prevent the side effects of large fluid administration. Thus, in addition to hemodynamic parameters and TFCd0%, the simultaneous use of the dynamic parameters derived from heart–lung interactions, indicative of fluid responsiveness, would improve intraoperative fluid management [
In the clinical field, fluid balance is difficult to estimate accurately, due to conditions such as continuous surgical bleeding in the operating field, absorption of surgical bleeding by gauzes, and the insensible loss of body fluid. Furthermore, estimates based on the intake and output of intraoperative fluid are time-consuming. In pediatric cardiac surgery, patients require continuous monitoring for intraoperative fluid balance. The TFCd0%, which correlated well with body weight gain, body weight gain%, and intraoperative fluid balance, may be more useful indicator than the conventional methods for fluid management.
In conclusion, TFCd0%, derived using a bioreactance technique, correlated well with body weight gain, body weight gain%, and intraoperative fluid balance. It is therefore a useful indicator in the intraoperative fluid management of pediatric patients undergoing a Fontan procedure.
Cardiopulmonary bypass
Central venous pressure
Pulmonary capillary wedge pressure
Bidirectional cavopulmonary shunt
Thoracic fluid content
Percent change of thoracic fluid content compared to the baseline
Noninvasive cardiac output monitoring
Mean arterial pressure
Cardiac output
Cardiac index
Stroke volume
Stroke volume variation
Intensive care unit
The difference in thoracic fluid content
Pulmonary artery pressure.
The authors declare that they have no conflicts of interest.
Tae-Gyoon Yoon contributed to data collection and analysis and manuscript writing, Kyunghwan Jang, Chung-Sik Oh, and Seong-Hyop Kim contributed to data collection and analysis, and Woon-Seok Kang contributed to study design, data analysis, and manuscript writing. All authors read and approved the final manuscript.
This work was supported by Konkuk University.