The Accuracy of Velocity-Time Integral Variation and Peak Velocity Variation of the Left Ventricular Outflow Tract in Predicting Fluid Responsiveness in Postoperative Patients Mechanically Ventilated at Low Tidal Volumes

RESPIRATORY VARIATION OF VELOCITY TIME INTEGRAL AND PEAK VELOCITY OF LEFT VENTRICULAR OUTFLOW TRACT FOR PREDICTING HYPOTENSION AFTER INDUCTION OF GENERAL ANESTHESIA IN ELDERLY PATIENTS

ABSTRACT

Background : Hypotension after induction of general anesthesia may lead to severe complications in elderly patients. This study investigated whether the respiratory variation of velocity time integral (ΔVTI) and peak velocity (ΔVpeak) of left ventricular outflow tract (LVOT) could predict hypotension after induction of general anesthesia in elderly patients. Methods : 120 elderly patients undergoing selective operation under general anesthesia were enrolled in this study. ΔVTI and ΔVpeak of LVOT were measured by transthoracic echocardiography before induction of general anesthesia. After induction, mean arterial pressure (MAP) was recorded every 1 min for 15 min. Hypotension was defined as a decrease of more than 30% in MAP at baseline or MAP below 65 mmHg from the start of induction. Receiver operating characteristic curves with gray zone and multivariate logistic regression analysis were used to assess the ability of ΔVTI and ΔVpeak of LVOT to predict hypotension after induction of general anesthesia. Results : Hypotension occurred in 64 (53.3%) patients after induction of general anesthesia. The area under receiver operating characteristic curves (AUC) for δVpeak of LVOT to predict hypotension after induction of general anesthesia was 0.811, and the optimal cutoff value was 13.1% with a gray zone of 9.9% to 13.8%, including 45.0% of patients. The AUC for ΔVTI of LVOT was 0.890, and the optimal cutoff value was 13.8% with a gray zone of 11.1% to 13.9%, including 25.8% of patients. After adjusting for confounders, ΔVTI (Odds ratio = 2.24) and ΔVpeak (Odds ratio = 2.09) of LVOT were two significant independent predictors of hypotension after induction of general anesthesia. Conclusions : ΔVTI of LVOT was a reliable predictor of hypotension after the induction of general anesthesia in elderly patients. ΔVpeak of LVOT should be used cautiously to predict hypotension after induction of general anesthesia due to nearly half of elderly patients in the gray zone. Trial registration : This study was registered in the Chinese Clinical Trial Registry (registration number: ChiCTR2300077117).

The Left Ventricular Outflow Tract Velocity Time Integral as a Predictor of Fluid Responsiveness in Patients With Sepsis-Related Acute Circulatory Failure

BACKGROUND

Sepsis is a major contributor to global morbidity and mortality. Effective fluid resuscitation is essential for managing septic shock, but it must be carefully monitored to avoid fluid overload and related complications. Recent studies have demonstrated that both inadequate and excessive fluid resuscitation are linked to poor outcomes.

METHODS

This observational study was conducted over 18 months, including spontaneously breathing patients aged 18 to 65 with sepsis-related acute circulatory failure. Patients were enrolled through convenience sampling. Baseline vital signs and point-of-care ultrasound (POCUS) parameters were recorded. A volume expansion test (VET) was performed, administering 500 ml of normal saline over 15 minutes, followed by reassessment of vital signs and POCUS parameters. Patients were classified as responders or non-responders. The study evaluated the left ventricular outflow tract velocity time integral (LVOT VTI) as a predictor of fluid responsiveness.

RESULTS

The study enrolled 113 patients with a mean age of 48.69 years (SD: ±16.81). The most common age group was 61-70 years (24 patients; 21.2%), and there was a male predominance (73 patients; 64.6%). Forty-eight patients (42.5%) had no comorbidities, with hypertension being the most prevalent (17 patients; 15.0%). Pneumonia was the most common source of sepsis (50 patients; 44.2%), and 16 patients (14.2%) died. The percentage change in LVOT VTI following the VET demonstrated a sensitivity of 96.0% and specificity of 100%, with an area under the receiver operating characteristic (ROC) curve of 0.992. A percentage change of ≥15.19% indicated high fluid responsiveness, although a single VTI measurement alone was not a reliable predictor.

CONCLUSION

LVOT VTI measurements play a critical role in assessing fluid responsiveness in sepsis-related acute circulatory failure. While a single VTI measurement is unreliable, the percentage change in LVOT VTI after a VET offers excellent diagnostic performance. A cutoff of ≥15.19% post-expansion indicates a high likelihood of fluid responsiveness.

Central venous oxygen saturation changes as a reliable predictor of the change of CI in septic shock: To explore potential influencing factors

PURPOSE

Assessing fluid responsiveness relying on central venous oxygen saturation (ScvO2) yields varied outcomes across several studies. This study aimed to determine the ability of the change in ScvO2 (ΔScvO2) to detect fluid responsiveness in ventilated septic shock patients and potential influencing factors.

METHODS

In this prospective, single-center study, all patients conducted from February 2023 to January 2024 received fluid challenge. Oxygen consumption was measured by indirect calorimetry, and fluid responsiveness was defined as an increase in cardiac index (CI) ≥ 10% measured by transthoracic echocardiography. Multivariate linear regression analysis was conducted to evaluate the impact of oxygen consumption, arterial oxygen saturation, CI, and hemoglobin on ScvO2 and its change before and after fluid challenge. The Shapiro-Wilk test was used for the normality of continuous data. Data comparison between fluid responders and non-responders was conducted using a two-tailed Student t-test, Mann Whitney U test, and Chi-square test. Paired t-tests were used for normally distributed data, while the Wilcoxon signed-rank test was used for skewed data, to compare data before and after fluid challenge.

RESULTS

Among 49 patients (31 men, aged (59 ± 18) years), 27 were responders. The patients had an acute physiology and chronic health evaluation II score of 24 ± 8, a sequential organ failure assessment score of 11 ± 4, and a blood lactate level of (3.2 ± 3.1) mmol/L at enrollment. After the fluid challenge, the ΔScvO2 (mmHg) in the responders was greater than that in the non-responders (4 ± 6 vs. 1 ± 3, p = 0.019). Multivariate linear regression analysis suggested that CI was the only independent influencing factor of ScvO2, with R2 = 0.063, p = 0.008. After the fluid challenge, the change in CI became the only contributing factor to ΔScvO2 (R2 = 0.245, p < 0.001). ΔScvO2 had a good discriminatory ability for the responders and non-responders with a threshold of 4.4% (area under the curve = 0.732, p = 0.006).

CONCLUSION

ΔScvO2 served as a reliable surrogate marker for ΔCI and could be utilized to assess fluid responsiveness, given that the change in CI was the sole contributing factor to the ΔScvO2. In stable hemoglobin conditions, the absolute value of ScvO2 could serve as a monitoring indicator for adequate oxygen delivery independent of oxygen consumption.

Use of POCUS for the assessment of dehydration in pediatric patients-a narrative review

In pediatric practice, POCUS (point-of-care ultrasound) has been mostly implemented to recognize lung conditions and pleural and pericardial effusions, but less to evaluate fluid depletion. The main aim of this review is to analyze the current literature on the assessment of dehydration in pediatric patients by using POCUS. The size of the inferior vena cava (IVC) and its change in diameter in response to respiration have been investigated as a tool to screen for hypovolemia. A dilated IVC with decreased collapsibility (< 50%) is a sign of increased right atrial pressure. On the contrary, a collapsed IVC may be indicative of hypovolemia. The IVC collapsibility index (cIVC) reflects the decrease in the diameter upon inspiration. Altogether the IVC diameter and collapsibility index can be easily determined, but their role in children has not been fully demonstrated, and an estimation of volume status solely by assessing the IVC should thus be interpreted with caution. The inferior vena cava/abdominal aorta (IVC/AO) ratio may be a suitable parameter to assess the volume status in pediatric patients even though there is a need to define age-based thresholds. A combination of vascular, lung, and cardiac POCUS could be a valuable supplementary tool in the assessment of dehydration in several clinical scenarios, enabling rapid identification of life-threatening primary etiologies and helping physicians avoid inappropriate therapeutic interventions.   Conclusion: POCUS can provide important information in the assessment of intravascular fluid status in emergency scenarios, but measurements may be confounded by a number of other clinical variables. The inclusion of lung and cardiac views may assist in better understanding the patient's physiology and etiology regarding volume status. What is Known: • In pediatric practice, POCUS (point-of-care ultrasound) has been mostly implemented to recognize lung conditions (like pneumonia and bronchiolitis) and pleural and pericardial effusions, but less to evaluate fluid depletion. • The size of the IVC (inferior vena cava) and its change in diameter in response to respiration have been studied as a possible screening tool to assess the volume status, predict fluid responsiveness, and assess potential intolerance to fluid loading. What is New: • The IVC diameter and collapsibility index can be easily assessed, but their role in predicting dehydration in pediatric age has not been fully demonstrated, and an estimation of volume status only by assessing the IVC should be interpreted carefully. • The IVC /AO(inferior vena cava/abdominal aorta) ratio may be a suitable parameter to assess the volume status in pediatric patients even though there is a need to define age-based thresholds. A combination of vascular, lung, and cardiac POCUS can be a valuable supplementary tool in the assessment of intravascular volume in several clinical scenarios.

Critical Care Echocardiography-A Driven Approach to Undifferentiated Shock

The clinical approach to undifferentiated shock in critically ill patients should be revised to use modern, point-of-care tools that are readily available. With the increasing availability of 2-dimensional ultrasonography and advanced Doppler capabilities, a quick, simplified, and integrated stepwise approach to shock using critical care echocardiography is proposed. Evidence supports the feasibility and usefulness of critical care echo-cardiography in enhancing diagnostic accuracy for shock, but there is a lack of systematic application of the technology in patients with undifferentiated shock. The proposed approach begins with the use of noninvasive ultrasonography with pulsed-wave Doppler capability to determine the flow state by measuring the velocity time integral of the left ventricular outflow tract. This narrative review explores the use left ventricular outflow tract velocity time integral, velocity time integral variation, limited visceral organ Doppler, and lung ultrasonography as a systematic approach for patients with undifferentiated shock.