Non-invasive assessment of fluid responsiveness to guide fluid therapy in patients with sepsis in the emergency department: a prospective cohort study

Incidence, predictability, and outcomes of systemic venous congestion following a fluid challenge in initially fluid-tolerant preload-responders after cardiac surgery: a pilot trial

BACKGROUND

Fluid administration has traditionally focused on preload responsiveness (PR). However, preventing fluid intolerance, particularly due to systemic venous congestion (VC), is equally important. This study evaluated the incidence and predictability of VC following a 7 ml/kg crystalloid infusion in fluid-tolerant preload-responders and its association with adverse outcomes.

METHODS

This single-center, prospective, observational study (May 2023-July 2024) included 40 consecutive patients who were mechanically ventilated within 6 h of intensive care unit (ICU) admission after elective open-heart surgery and had acute circulatory failure. Patients were eligible if they were both fluid-tolerant and preload-responsive. PR was defined as a ≥ 12% increase in left-ventricular outflow tract velocity time integral (LVOT-VTI) 1 min after a passive leg raising (PLR) test. VC was defined by a portal vein pulsatility index (PVPI) ≥ 50%. Patients received a 7 ml/kg Ringer's Lactate infusion over 10 min. The primary outcome was the incidence of VC 2 min post-infusion (early-VC). Secondary outcomes included VC at 20 min, the incidence of acute kidney injury (AKI) and severe AKI at 7 days, and ICU length of stay (LOS).

RESULTS

45% of patients developed early-VC, with VC persisting in only 5% at 20 min. One-third of patients developed AKI, with 17.5% progressing to severe AKI. The median ICU LOS was 4 days. Patients with early-VC had significantly higher central venous pressure, lower mean perfusion pressure, worse baseline right ventricular function, and a higher incidence of severe AKI. While LVOT-VTI returned to baseline by 20 min in both groups, PVPI remained elevated in early-VC patients (p < 0.001). The LVOT-VTI versus PVPI regression line showed similar slopes (p = 0.755) but different intercepts (p < 0.001), indicating that, despite fluid tolerance and PR at baseline, early-VC patients had reduced right ventricular diastolic reserve (RVDR). Post-PLR PVPI predicted early-VC with an area under the curve of 0.998, using a threshold of 44.3% (p < 0.001).

CONCLUSION

Post-PLR PVPI effectively predicts fluid-induced early-VC in fluid-tolerant preload-responders, identifying those with poor RVDR. Its use can guide fluid management in cardiac surgery patients, helping to prevent unnecessary fluid administration and associated complications.

TRIAL REGISTRATION

NCT06440772. Registered 30 May 2024. Retrospectively registered.

The role of point-of-care ultrasound to monitor response of fluid replacement therapy in pregnancy

Fluid management in obstetrical care is crucial because of the complex physiological conditions of pregnancy, which complicate clinical manifestations and fluid balance management. This expert review examined the use of point-of-care ultrasound to evaluate and monitor the response to fluid therapy in pregnant patients. Pregnancy induces substantial physiological changes, including increased cardiac output and glomerular filtration rate, decreased systemic vascular resistance, and decreased plasma oncotic pressure. Conditions, such as preeclampsia, further complicate fluid management because of decreased intravascular volume and increased capillary permeability. Traditional methods for assessing fluid volume status, such as physical examination and invasive monitoring, are often unreliable or inappropriate. Point-of-care ultrasound provides a noninvasive, rapid, and reliable means to assess fluid responsiveness, which is essential for managing fluid therapy in pregnant patients. This review details the various point-of-care ultrasound modalities used to measure dynamic changes in fluid status, focusing on the evaluation of the inferior vena cava, lung ultrasound, and left ventricular outflow tract. Inferior vena cava ultrasound in spontaneously breathing patients determines diameter variability, predicts fluid responsiveness, and is feasible even late in pregnancy. Lung ultrasound is crucial for detecting early signs of pulmonary edema before clinical symptoms arise and is more accurate than traditional radiography. The left ventricular outflow tract velocity time integral assesses stroke volume response to fluid challenges, providing a quantifiable measure of cardiac function, which is particularly beneficial in critical care settings where rapid and accurate fluid management is essential. This expert review synthesizes current evidence and practice guidelines, suggesting the integration of point-of-care ultrasound as a fundamental aspect of fluid management in obstetrics. It calls for ongoing research to enhance techniques and validate their use in broader clinical settings, aiming to improve outcomes for pregnant patients and their babies by preventing complications associated with both under- and overresuscitation.

Differences in Hemodynamic Response to Passive Leg Raising Tests during the Day in Healthy Individuals: The Question of Normovolemia

BACKGROUND

The passive leg-raising (PLR) test was developed to predict fluid responsiveness and reduce fluid overload. However, the hemodynamic response of healthy individuals to the PLR test and how it changes during the day, between the morning and evening, after individuals have consumed food and fluids, has not been profoundly explored. This study aimed to compare the systemic hemodynamic changes in healthy individuals between morning and evening PLR tests.

METHODS

In this study, the PLR test was performed twice a day. The first PLR test was performed between 08h00 and 09h00 in the morning, while the second PLR test was performed between 20h00 and 21h00 in the evening. Hemodynamic parameters were measured using an impedance cardiography monitor, and a cutoff value of a 10% increase in stroke volume (SV) during the PLR test was used to differentiate between preload responders and non-responders.

RESULTS

We included 50 healthy volunteers in this study. When comparing the morning and evening PLR test results, we found no PLR-induced differences in heart rate (-3 [-8-2] vs. -2 [-8-4] beats/min, p = 0.870), SV (11 [5-22] vs. 12 [4-20] mL, p = 0.853) or cardiac output (0.7 [0.2-1.3] vs. 0.8 [0.1-1.4] L/min, p = 0.639). We also observed no differences in the proportion of preload responders during the PLR test between the morning and evening (64% vs. 66%, p = 0.99). However, there was a moderate agreement between the two PLR tests (morning and evening) (kappa = 0.429, p = 0.012). There was a moderate correlation between the changes in SV between the two PLR tests (r_s = 0.50, p < 0.001).

CONCLUSION

In young, healthy individuals, we observed no change in the systemic hemodynamic responsiveness to the PLR test between the morning and evening, without restriction of fluid and food intake.

Contemporary Review of Hemodynamic Monitoring in the Critical Care Setting

Hemodynamic assessment remains the most valuable adjunct to physical examination and laboratory assessment in the diagnosis and management of shock. Through the years, multiple modalities to measure and trend hemodynamic indices have evolved with varying degrees of invasiveness. Pulmonary artery catheter (PAC) has long been considered the gold standard of hemodynamic assessment in critically ill patients and in recent years has been shown to improve clinical outcomes among patients in cardiogenic shock. The invasive nature of PAC is often cited as its major limitation and has encouraged development of less invasive technologies. In this review, the authors summarize the literature on the mechanism and validation of several minimally invasive and noninvasive modalities available in the contemporary intensive care unit. They also provide an update on the use of focused bedside echocardiography.