Hypovolemia assessment with inferior vena cava collapsibility index in cardiac surgery patients: a cross-sectional study

Abstract

Background

Patients who undergo cardiac surgery are at high risk of developing hemodynamic instability during induction of anesthesia, with hypovolemia being a possible trigger. The diagnosis of this condition usually depends on the anesthesiologist’s clinical judgment and ability to interpret hemodynamic parameters once induction has begun. Assessment of inferior vena cava collapsibility and diameter has been correlated with identification of patient volume status. The aim of this study was to describe hemodynamic behavior during anesthetic induction based on the presence of hypovolemia, assessed with the inferior vena cava collapsibility index (IVCCI), in patients who underwent coronary artery bypass grafting (CABG) surgery or aortic valve replacement (AVR).

Methods

This descriptive cross-sectional study included the sequential sampling of 60 adult patients programmed for CABG or AVR between July 2022 and January 2023. Patients with reduced ejection fraction (< 40%), a history of liver disease, ascites, cardiac arrhythmias, abdominal hypertension and a body mass index > 35 kg/m² were excluded. The IVCCI was measured via ultrasonography and calculated using a specific formula, with hypovolemia defined as an IVCCI greater than 30%. Demographic data, echocardiographic measurements, hemodynamic variables (respiratory rate, blood pressure, heart rate) were extracted, and the IVCCI was calculated. Variables were analyzed via JASP v 0.17.1.

Results

Among the 60 patients who were included, 40 underwent CABG, and 20 underwent AVR. 67% (n = 40) of the sample developed hypovolemia, with no significant difference between the CABG and AVR groups. The mean IVCCI was 32.7 (95% CI: 30.5–34.8) for CABG and 29.33 (95% CI: 25.6–33.0) for AVR. No significant difference in hemodynamic changes was found between the groups classified by volume status. Moreover, an exploratory analysis of the impact of fasting on the risk of developing hypovolemia revealed a Pearson correlation coefficient that was weak but positive (0.20) among these variables.

Conclusions

This study showed no significant changes in hemodynamic behavior in the evaluated patients prior to, during, or after anesthetic induction with an IVCCI cut-off value of 30%. Similarly, a slight positive correlation was observed between fasting and hypovolemia, although it lacked statistical significance.

Background

Hemodynamic instability during the induction of anesthesia is a recognized and multifactorial clinical entity. Fluid replacement therapy plays a fundamental role in treating this condition in both critical and perioperative patients [1]. The concept of fluid responsiveness has recently become a topic of great interest as a practical assessment for the correct administration of intravenous fluids (fluid therapy).

The restoration and proper maintenance of volume status are fundamental goals for the proper management of patients undergoing cardiac surgery and those who are under any state of shock [2, 3]. In the former, both fluid overload and dehydration can have serious consequences. On the one hand, an inadequate supply can lead to poor tissue perfusion and deterioration of organ function. On the other hand, excessive fluid administration can interfere with adequate oxygenation, prolong intensive care unit (ICU) and inpatient stays, complicate patient recovery, and increase mortality by even 50% [4]. In fact, a cohort review revealed a positive association between cumulative daily fluid balance and mortality [5].

A goal-directed therapy protocol can improve cardiac output, oxygen delivery, effective circulating volume, organ function and mean arterial pressure in patients after cardiac surgery [6]. Lopes M et al. reported that optimization of preload and cardiac output (CO) in patients undergoing major surgery reduces postoperative complications and length of hospital stay [7]. In addition, uncorrected hypovolemia has been shown to lead to inadequate infusion of vasopressors, which may increase organ hypoperfusion and result in ischemia [8].

Fluid resuscitation then requires accurate assessment of intravascular volume status (cardiac preload) and the likelihood of the patient responding (increased systolic volume) to a fluid challenge. Recently, minimally invasive techniques for functional hemodynamic monitoring have been developed, replacing invasive monitoring methods such as the Swan–Ganz catheter. These new techniques use ultrasonographic assessment of the vena cava, a method that has been shown to respond to the prototype of fluid therapy management in the ICU. However, there is still a lack of wide local data from clinical studies that evaluate the volume status of patient candidates for cardiac surgery by measuring the distensibility of the inferior vena cava and therefore determine that it can be easy to measure, safe and has a lower proportion of potential risks than more invasive techniques do [9].

In fact, volumetric markers of cardiac preload have been shown to be useful in testing whether cardiac preload increases effectively during fluid infusion. Relevant studies have evaluated the effect of respiratory cycle variation in vena cava diameter as a guide to fluid responsiveness. With an increase of 10–15% in CO (fluid-sensitive cardiac output), the analysis of IVC diameter variation effectively detected fluid responsiveness [10].

Thus, expanding the knowledge of the hemodynamic behavior of patients undergoing cardiac surgery by understanding their state of hypovolemia in relation to the collapsibility index of the vena cava becomes relevant in our clinical practice and allows to expand the use of minimally invasive techniques for the diagnosis and hemodynamic monitoring of cardiac surgery patients.

The following article describes the hemodynamic behavior of patients undergoing Coronary Artery Bypass Grafting and Aortic Valve Replacement in relation to the variation in the inferior vena cava collapsibility index (IVCCI). The IVCCI, as determined by echocardiography, serves as the theoretical presumptive point of volume of status variation in this study. The results will contribute to the existing understanding on the behavior of these dynamic parameters in patients undergoing cardiac surgery. Furthermore, they will serve as a basis for studies that aim to study the associations between hemodynamic behavior and these surrogate parameters of hypovolemia.

Methods

A descriptive, observational, cross-sectional study, approved by the Institutional Ethics Committee of Fundación Cardioinfantil-IC (Ethics Committee Approval Letter DDI4688–2022), was conducted in 60 patients who underwent coronary artery bypass graft surgery (CABG) or aortic valve replacement (AVR) at the Fundación Cardioinfantil-IC, Bogotá, Colombia, between July 2022 and January 2023. The sample is chosen consecutively and non-probabilistically until the end of the defined period. Patients who met the following criteria were included: adults older than 18 years who had undergone CABG surgery or aortic valve replacement, patients on spontaneous ventilation (without ventilatory support), and patients with scheduled surgery. Patients with a body mass index (BMI) > 35 kg/m², history or current liver disease, ascites, cardiac arrhythmias, abdominal hypertension and decreased ejection fraction (LVEF < 40%) were excluded. The latter was due to the fact that patients with low ejection fraction may exhibit different hemodynamic behavior. This different hemodynamic behavior could potentially mask the effect of hypovolemia and act as a potential confounder. Furthermore, the STROBE reporting guideline was used to draft this manuscript, and the STROBE reporting checklist was utilized during the editing process.

Institutional management protocol for patients undergoing cardiac surgery

Our institution adheres strictly to the American Society of Anesthesiologists (ASA) guidelines for preoperative fasting. Accordingly, our patients are instructed to abstain from clear liquids for at least 2 h, from a light meal for at least 6 h, and from a fatty or heavy meal for a minimum of 8 h prior to the induction of anesthesia. Additionally, hemodynamic management, including the use of vasopressors and assessment of intravascular volume status, was left to the discretion of the attending anesthesiologist, in accordance with individual patient characteristics and intraoperative conditions.

Measurement technique

The collapsibility of the inferior vena cava was evaluated via ultrasonography, using the Phillips^® CVX 3D equipment and a 2–5 MHz sectorial transducer by a cardiovascular anesthesiologist trained in echocardiography. The assessment was performed prior to anesthesia induction in the preoperative preparation area, with the patient under spontaneous ventilation. A subcostal window with a longitudinal M-mode slice was used to assess the diameter of the inferior vena cava and its variability with inspiratory and expiratory movements. A static measurement obtained with the millimeter measuring tool and the following formula were used to calculate the IVCCI: ([maximal venous diameter during expiration - minimal venous diameter during inspiration]/maximal vessel diameter) × 100%. After a comprehensive review of the literature, it was determined that the IVCCI cut-off value for this study should be set at 30%. Duwat et al. reported a sensitivity of 80.7% and a specificity of 93.7% for an IVCCI greater than 30% [11].

Data analysis

The study included a range of variables, including anthropometric measurements (weight, BMI, height), demographic data (age, sex), echocardiographic measurements (Inferior vena cava distensibility index, hypovolemia as a low IVCCI), and hemodynamic variables (central venous pressure, mean arterial pressure.). Additionally, clinical variables taken during hospitalization were incorporated into the analysis (arterial blood gas data, water balance and others). To detect a prevalence of 30% of IVCCI in our study population, we estimated a required sample size of 66 patients, with 80% power and a 95% confidence level.

To analyze the qualitative variables, the absolute and relative frequencies were calculated. For quantitative variables, means and standard deviations or interquartile ranges and medians were calculated via the Shapiro‒Wilk test, depending on the assumption of normality of the variables evaluated. For bivariate analysis, a T-test and Chi-square test were used, depending on the nature of the variable, with a 95% confidence interval. For some variables of interest, an exploratory analysis of simple linear correlation and Pearson’s correlation coefficient was performed. Statistical analysis was executed with JASP software version 0.17.1.

Results

A total of 60 patients were included in the study, 40 of whom underwent CABG surgery and 20 of whom underwent aortic valve replacement. The mean age was 66.5 ± 8.7 years, with a lower age range among those taken to aortic valve replacement. Among the total patients, 73.3% were male, with a greater proportion in the myocardial revascularization (CABG) group (70.4%) (Table 1).

Table 1.

Demographic and clinical characteristics of patients who underwent cardiovascular surgery

Characteristics	Frequency (n = 60)	AVR	CABG	p
Age (years)	66.5 ± 8.7	65.4 ± 9.4	67.0 ± 8.4	0.343
Weight (kg)	72.1 ± 14.4	68.6 ± 15.2	73.86 ± 13.8	0.099
Height (cm)	165.1 ± 9.8	163.5 ± 0.9	165.9 ± 0.9	0.131
Males (%)	44 (73.3%)	13 (29,5%)	31 (70,4%)	0.004
Fasting (hours)	14.5 ± 3.3	14.25 ± 3.28	14.62 ± 3.32	0.525
Arterial hypertension	46 (76.6%)	14 (30,5%)	32 (69,5%)	0.003
Diabetes	19 (31.6%)	3 (15,7%)	16 (84,2)	0.001
Dyslipidemia	37 (61.6%)	9 (24,3%)	28 (75,6%)	0.001
Smoking	14 (23.3%)	2 (14,2%)	12 (85,7%	0.001
Chronic kidney disease	4 (6.6%)	2 (50%)	2 (50%)	0.545
Hypothyroidism	13 (21.6%)	2 (15,4%)	11 (84,6%)	0.002

Additionally, hypovolemia, defined as an IVCCI greater than 30%, was present in 67% (n = 40) of the total sample. No important differences were found between the groups when the IVCCI and type of surgery were compared. The mean IVCCI for the CABG group was 32.7 (95% CI; 30.5–34.8) versus 29.33 (95% CI; 25.6–33–0) for AVR. An association was found between sex and the presence of hypovolemia, with men being more likely to have hypovolemia than women (82.5% vs. 17.5%, respectively). OR 2.72; p = 0.023) (Table 1).

When evaluating the relationship between IVCCI and fasting, we found that the mean fasting time of patients without hypovolemia was 13.4 ± 3.2 h, whereas those with hypovolemia had a mean fasting time of 15.1 ± 3.3 h. In addition, a nonsignificant trend toward a higher inferior vena cava collapsibility index was observed in patients with longer preoperative fasting (Fig. 1).

Fig. 1.

Fasting and the presence of hypovolemia in patients candidates for cardiovascular surgery

Hemodynamic behavior following anesthetic induction

The general hemodynamic behavior of patients undergoing cardiac surgery showed a progressive decrease in systolic (preinduction 144.8 mmHg) and diastolic (71.7 mmHg) blood pressure after induction of anesthesia (102.9 mmHg; 54.5 mmHg). However, heart rate (HR) parameters did not show greater variability from the time of preinduction to 10 min later (Fig. 2).

Fig. 2.

General hemodynamic behavior of patients during induction of anesthesia. SBP: Systolic blood pressure; DBP: Diastolic blood pressure; HR: Heart rate

A comparison of the population according to the presence of hypovolemia, defined as an IVCCI greater than 30%, revealed no significant differences in any hemodynamic variables before or after induction (Fig. 3 and see Appendix for supplementary Table 1).

Fig. 3.

Hemodynamic behavior of classified patients with hypovolemia according to inferior vena cava index measurements. <30: collapsibility index < 30% (no hypovolemia), > 30: collapsibility index > 30% (hypovolemia); SBP: systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate

Furthermore, 48.3% of patients required vasopressor administration during anesthetic induction; however, no significant differences were found in the use of vasopressors among patients diagnosed with hypovolemia according to the collapsibility index (p = 0.715).

An exploratory analysis was performed. A Pearson correlation coefficient between the IVCCI and fasting variables was obtained, which revealed a weak positive correlation (0.20) between these two variables (Fig. 4).

Fig. 4.

Simple linear regression between fasting and collapsibility index

Both groups, aortic valve replacement and myocardial revascularization, an almost identical fasting time average, 14.12 ± 3.1 h and 14.6 ± 3.4 h, respectively.

Arterial blood gases after anesthetic induction

Out of the total sample, an average pH of 7.4, a lactate concentration of 1.0 mmol/L, an oxygen saturation of 94.7%, a hemoglobin concentration of 14 g/dL, an excess base concentration of −2.5 and a potassium concentration of 3.6 mEq/L were observed, with no statistically significant differences regardless of the type of procedure and volume status (Table 2).

Table 2.

Arterial blood gases after anesthetic induction

Variable	Frequency (n = 60)	Euvolemia	Hypovolemia	p
pH	7.4 ± 0.05	7.39 ± 0.05	7.40 ± 0.05	0.476
NaHCO3	21 ± 2.1	21.7 ± 2.0	20.9 ± 2.1	0.543
Lactate	1.0 ± 0.4	1.03 ± 0.50	1.00 ± 0.44	0.648
SpO2	94.7 ± 2.9	94.4 ± 2.9	94.8 ± 2.9	0.482
FIO2	76.9 ± 34.4	77.1 ± 33.5	76.9 ± 35.3	0.584
CO2	34.2 ± 5.5	35.0 ± 6.7	33.8 ± 4.7	0.145
Hb	14 ± 1.9	14.2 ± 2.6	14.3 ± 1.6	0.934
Hct	43 ± 6.0	42.4 ± 6.9	43.6 ± 5.6	0.667
Base Excess	−2.5 ± 2.1	−2.55 ± 1.7	−2.58 ± 2.2	0.841
Na+	139.8 ± 2.8	139.4 ± 3.1	140.0 ± 2.7	0.367
K+	3.6 ± 0.3	3.6 ± 0.28	3.6 ± 0.40	0.548
Cl	103.3 ± 2.9	102.8 ± 2.7	103.5 ± 3.0	0.745

Discussion

Evaluation of volume status in patients undergoing cardiac surgery remains a significant perioperative challenge. Although IVCCI has emerged as a noninvasive and dynamic tool for assessing intravascular volume, its utility in this specific patient population has not been well established. This study contributes novel evidence on the subject, with the potential to enhance clinical decision-making and improve hemodynamic optimization.

Post-induction hypotension (PIH) is defined as an episode of hypotension after the induction of general anesthesia. This is a common event that is often associated with a high burden of comorbidities and an increased risk of hemodynamic compromise during anesthetic induction. In patients who are submitted to cardiac surgery PIH is known to be associated with postoperative adverse events [12]. This adverse hemodynamic behavior may be influenced by the preoperative volume status of patients. In this study, we observed a total of 60 cardiac surgery patients who underwent echocardiographic evaluation to assess the preinduction volume status. The mean age was 66 years, with a male predominance (73.3%). More than 50% of the study patients had some comorbidities, the most common being arterial hypertension and diabetes mellitus (77% and 62%, respectively). Patients who underwent CABG had a greater burden of comorbidities, with higher proportions of arterial hypertension (69.5% vs. 30.5%), diabetes mellitus (84.2% vs. 15.7%), dyslipidemia (75.6% vs. 24.3%), and hypothyroidism (84.6% vs. 15.4%) (Table 1).

These population characteristics and patterns of comorbidities are consistent with previous studies, as they share common features of the pathophysiology of degenerative cardiovascular disease. Several studies have shown that arterial hypertension increases the likelihood of developing hypotension during anesthesia induction by twofold [13]. This situation is exacerbated in elderly individuals because of reduced cardiac reserve and altered baroreceptor and sympathetic responses [14].

Hypovolemia description

The main objective of this study was to describe the presence of hypovolemia measured by the inferior vena cava collapsibility index in cardiovascular surgery patients. 67% of the patients taken to cardiac surgery had hypovolemia, without significant differences in the preoperative variables, except for sex, for which men had a significantly greater prevalence of hypovolemia (p = 0.023) (Supplementary Table 1).

A representative study in which the IVC diameter was evaluated via ultrasound to determine the volume response was conducted by Barbier et al., who included patients under mechanical ventilation without respiratory effort and obtained the distensibility index by using the maximum and minimum IVC diameters obtained just distal to the suprahepatic vein and expressed this value as an indexed percentage. Values greater than 18% were found to be associated with volume response, with a reported sensitivity and specificity of 90% [15]. Duwat et al. reported a sensitivity of 80.7% and a specificity of 93.7% for an IVC collapsibility index greater than 30% [11]. Subsequently, a re-evaluation of this cutoff value was conducted. The most recent cutoff value was determined to be greater than 43%, with the objective of enhancing both specificity and sensitivity [16].

In their study, Feissel et al. included patients under mechanical ventilation and obtained a distensibility index reporting a cutoff point of 12% (established as a volume responder, values above 12%), with a positive predictive value of 93% and a negative predictive value of 92% [10]. Muller evaluated the IVC collapsibility index in spontaneously ventilated patients and reported a cutoff of 40%, with a sensitivity of 70% and specificity of 80% [17].

In the most robust investigation of spontaneously breathing critically ill patients, aiming to determine the usefulness of the collapsibility index measured by transthoracic echocardiography as a predictor of response to fluid administration, it was shown that the IVCCI can predict fluid response, with a cutoff value of 25% [18]. Therefore, in our study, and owing to the absence of consensus in the definition of intraoperative hypotension, we defined the presence of hypovolemia as an IVCCI greater than 30%, which is comparable to the cutoff of 38% obtained by Zhang & Critchley in a subgroup of patients with preexisting cardiovascular disease [19].

We evaluated the volume status on the basis of the type of surgery. The mean IVCCI for the CABG group was 32.7 (95% CI 30.5–34.8) versus 29.33 (95% CI 25.6–33.0) for AVR, with no significant difference between these 2 groups despite the distinct burden of comorbidities, demonstrating that underlying pathologies do not significantly influence the volume status of patients before surgery. Regarding the age of the patients included we found that men are more likely to present with hypovolemia than women are (82.5% vs. 17.5%. OR 2.72; p: 0.023), these findings may be explained by the greater number of men included in our sample.

Relationship between fasting and the use of vasopressors according to volume status

Moreover, regarding the analysis of the influence of fasting hours versus volume status, we did not find a strong association between fasting time and collapsibility index, with a weak correlation index (0.20). However, when viewed graphically, fasting shows a bimodal trend, with a peak of patients considered hypovolemic after 15 h of fasting, showing a tendency toward greater hypovolemia in patients with more hours of oral restriction prior to the procedure. This relationship was not statistically significant (Fig. 1). This signal is consistent with studies linking fasting to hypovolemia in certain risk groups, leading to widely accepted recommendations to minimize perioperative fasting times [20]. Notably, the fasting time was similar between patients who underwent aortic valve replacement and those who underwent myocardial revascularization.

The most likely reason for not achieving statistical significance for this relationship in our study may be the limited sample size, given that the study was not planned to look for associations but rather to explore signals and generate hypotheses.

Arterial blood gas analysis

Hyperlactatemia has been documented to occur in 36% of patients undergoing cardiac surgery and works both as a predictor of mortality and an independent risk factor for worse outcomes in adult patients after cardiovascular surgery [21, 22]. However, in the present study, lactate levels were similar between patients with hypovolemia (1.00 ± 0.44) and those without hypovolemia (1.03 ± 0.50).

In general, regarding the obtained arterial blood gases, there was no significant difference in those patients diagnosed with or without hypovolemia (Table 2), contrary to the literature that reports acidosis as a metabolic disorder secondary to this disturbance [23].

Hemodynamic behavior

It is known that IVC pressure decreases during spontaneous inspiration because the pressure in the right atrium is a thin-walled, compliant structure and decreases with increasing pleural pressure in this stage. The degree to which central venous pressure (CVP) decreases during spontaneous inspiration depends on three variables: a decrease in (1) pleural pressure, (2) venous return function, and (3) cardiac function. Therefore, this decrease in CVP is transmitted to the IVC [24].

The assessment of intravascular volume status is a challenge, which is the reason why dynamic parameters to assess volume status, such as the vena cava collapsibility index, have been proposed [25, 26]. In our study, the overall hemodynamic behavior of patients who underwent cardiac surgery showed a progressive decrease in systolic (preinduction 144.8 mmHg) and diastolic (71.7 mmHg) blood pressure after the induction of anesthesia (102.9 mmHg; 54.5 mmHg) (Fig. 2). This is an expected behavior secondary to the dual pharmacologic effects of anesthetic induction agents: (1) influence on inotropism and (2) vasodilation with a consequent decrease in vascular resistance [27].

When the differential behavior of the patients according to the state of hypovolemia was evaluated (Fig. 3), there were no significant differences between the 2 groups. The small variation in arterial blood pressure may be the result of the sympathetic stimulation resulting from the intubation maneuvers and the maintenance of the hemodynamic status with intravenous fluids and vasopressors to counteract the vasodilator effects of the intravenous agents administered at the beginning of the induction.

These findings may be explained by the type of population studied. Zhang et al. [28] reported correlations between hypovolemia assessed by the IVCCI and the development of postinduction hypotension in a general population, but this relationship did not hold when the subgroup of high-risk patients was analyzed.

Similarly, Turconi et al. concluded that ultrasound measurements of the inferior vena cava during spontaneous ventilation are not good predictors of intraoperative hypotension after anesthetic induction in patients undergoing cardiovascular surgery, since the optimal points for predicting hypotension have low specificity and moderate sensitivity [29].

For our knowledge, currently the use of IVCCI ultrasound as a tool to assess volume status and guide fluid therapy is not well defined. In this proposal, the measurement of ultrasound collapsibility index showed that male patients could be at greater risk of hypovolemia, which suggested some signals around the relationship of the IVCCI with fasting hours. The utility of these measurements in the development of strategies to avoid hypotension in high-risk patients cannot yet be established with this study; however, owing to the ease of performance and its dynamic nature, the American Society of Echocardiography supports the use of IVCCI in the right atrial pressure estimation and therefore indirect volume status evaluation [30].

Strengths and limitations of the study

It is noteworthy that in the 60 patients included in the study, the IVC-derived parameters were measured via transthoracic echocardiography. This reinforces the concept that they can be easily obtained at the patient’s bedside by healthcare professionals with basic training in echocardiography.

The main strength of the study is the homogeneity of the types of surgery included; patients undergoing 2 types of major cardiovascular surgery were specifically studied, excluding factors known to affect IVCCI measurement. This element is of utmost importance, considering that this population could particularly benefit from the validation of the parameters studied.

It is not possible to evaluate the influence of information bias on hemodynamic behavior, even though the information was collected in a format designed exclusively for this purpose. The dynamic method of performing anesthetic management during induction and its subsequent recording in the anesthesia record implies a high risk of losing relevant information, such as the dose of intravenous fluids and vasopressors, which could limit the detection of differences in the groups according to the state of hypovolemia.

Despite its methodological limitations, the present study offers important insights into fasting time and the presence of hypovolemia in patients at high surgical risk. We were unable to demonstrate a close relationship between the presence of hypovolemia and hemodynamic behavior after induction, but this highlights the need for prospective studies that can better evaluate these relationships.

These results indicate that the measurement of IVC diameter may be useful in predicting the incidence of hypotension in patients who are candidates for cardiovascular surgery, particularly in relation to fasting time. Future clinical investigations could help assess the effectiveness of intravenous therapy, taking into account ultrasonographic measurements.

Conclusion

A prevalence of hypovolemia was observed in 67% of cases. A gender difference was identified, with males exhibiting a higher risk of hypovolemia. A weak positive correlation was noted between fasting time and IVCCI. No differences were found between types of surgery, arterial gases, or hemodynamics in patients with and without hypovolemia. Prospective studies are required to support the use of IVCCI under transthoracic ultrasound as a predictor of hypotension during anesthetic induction. Additionally, further studies are suggested to define the relevance of the inferior vena cava collapsibility index in patients who are candidates for cardiovascular surgery and are at high risk for morbidity and mortality.

Abbreviations

IVCCI

Inferior Vena Cava Collapsibility Index

AVR

Aortic Valve Replacement

CABG

Coronary Artery Bypass Grafting

BMI

Body Mass Index

LVEF

Left Ventricle Ejection Fraction

HTN

Hypertension

Author contributions

GAFG, HAMG, AFGG, LRH, JNDR, JJLR, SBV contributed to the conception and design of the study. HAMG and AFGG contributed to data collection and analysis. The text of the manuscript was written, reviewed, and approved by GAFG, HAMG, AFGG, LRH, JNDR, JJLR, SBV.

Funding

The present study was developed with internal resources. No external funding was required.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The entire protocol was carried out according to the relevant guidelines and regulations. Ethical approval for this research was obtained from the Fundación Cardioinfantil - Instituto de Cardiología Research and Ethics Committee (Acta 024-2022) on June 6, 2022. All participants provided informed consent to participate in the study. Written informed consent was obtained from the patients; a copy is available for inspection by the journal’s editor-in-chief upon request. The study was conducted within the ethical principles for medical research involving human subjects and human data according to the Declaration of Helsinki − 64th General Assembly, Fortaleza, Brazil, October 2013.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-025-03804-0.