Utility of the Venous Excess Ultrasound (VEXUS) score to track dynamic change in volume status in patients undergoing fluid removal during haemodialysis - the ACUVEX study.

BACKGROUND: The use of ultrasound assessment, including the Venous Excess Ultrasound (VEXUS) score, is increasingly being utilised as part of fluid status assessment in clinical practice. We aimed to evaluate the ability of the VEXUS score to track fluid removal during the course of the dialysis session and explore the relationship between traditional measures of fluid status and venous congestion. METHODS: Single-centre, observational study in patients undergoing intermittent haemodialysis, who presented above their target dry weight. Patients had serial assessment using VEXUS, lung ultrasound and selected echocardiographic measures, before, during and after fluid removal. RESULTS: Amongst 33 patients analysed, 5 (15%) had an elevated VEXUS score (> 0). There was no difference in starting weight, dry weight or amount of fluid removed in patients with a normal VEXUS score and those with an elevated VEXUS score. In all patients with elevated VEXUS scores, the degree of venous congestion improved during the course of fluid removal. All patients with an elevated VEXUS score had evidence of both right and left ventricular systolic impairment. CONCLUSION: In patients with ESRF undergoing haemodialysis, the incidence of venous congestion as measured by the VEXUS is low. In patients with elevated VEXUS scores, removal of fluid through haemodialysis improves the venous congestion score. The pattern of LV and RV systolic dysfunction suggests that VEXUS may be a reflection of cardiac failure rather than venous volume status. TRIAL REGISTRATION: Ethical approval was provided by South Central-Berkshire Research and Ethics Committee and registered on clinicaltrials.org (IRAS305720). TRIAL REGISTRATION: ISRCTN14351189 - Retrospectively registered on 30/11/2023.

Quantification of stroke volume in a simulated healthy volunteer model of traumatic haemorrhage; a comparison of two non-invasive monitoring devices using error grid analysis alongside traditional measures of agreement.

INTRODUCTION: Haemorrhage is a leading cause of death following traumatic injury and the early detection of hypovolaemia is critical to effective management. However, accurate assessment of circulating blood volume is challenging when using traditional vital signs such as blood pressure. We conducted a study to compare the stroke volume (SV) recorded using two devices, trans-thoracic electrical bioimpedance (TEB) and supra-sternal Doppler (SSD), against a reference standard using trans- thoracic echocardiography (TTE). METHODS: A lower body negative pressure (LBNP) model was used to simulate hypovolaemia and in half of the study sessions lower limb tourniquets were applied as these are common in military practice and can potentially affect some haemodynamic monitoring systems. In order to provide a clinically relevant comparison we constructed an error grid alongside more traditional measures of agreement. RESULTS: 21 healthy volunteers aged 18-40 were enrolled and underwent 2 sessions of LBNP, with and without lower limb tourniquets. With respect to absolute SV values Bland Altman analysis showed significant bias in both non-tourniquet and tourniquet strands for TEB (-42.5 / -49.6 ml), rendering further analysis impossible. For SSD bias was minimal but percentage error was unacceptably high (35% / 48%). Degree of agreement for dynamic change in SV, assessed using 4 quadrant plots showed a seemingly acceptable concordance rate for both TEB (86% / 93%) and SSD (90% / 91%). However, when results were plotted on an error grid, constructed based on expert clinical opinion, a significant minority of measurement errors were identified that had potential to lead to moderate or severe patient harm. CONCLUSION: Thoracic bioimpedance and suprasternal Doppler both demonstrated measurement errors that had the potential to lead to clinical harm and caution should be applied in interpreting the results in the detection of early hypovolaemia following traumatic injury.

Prospective longitudinal observational study of the macro and micro haemodynamic responses to septic shock in the renal and systemic circulations: a protocol for the MICROSHOCK - RENAL study.

INTRODUCTION: Septic acute kidney injury (AKI) is the most common complication of septic shock and increases mortality. A large body of experimental data suggests alterations in renal perfusion occur, but this is yet to be fully assessed in humans. The aim of the current study is to observe the macro and microcirculations in both the systemic and renal circulations in a cohort of patients with early septic shock. METHODS AND ANALYSIS: Single-centre, prospective, longitudinal, observational study of 50 patients with septic shock. Renal microcirculatory assessment will be performed with contrast-enhanced ultrasound, the sublingual microcirculation assessed with incident dark field microscopy and transthoracic echocardiography used to assess global flow. Patients will be enrolled as soon as possible after admission to the intensive care unit and then at +24,+48 and +96 hours. Blood samples of circulatory and renal biomarkers will be collected. Sample groups will be defined by the presence or absence of AKI and then subclassified by the severity (Kidney Disease Improving Global Outcomes (KDIGO) criteria), variables will be compared within and between groups over time. ETHICS AND DISSEMINATION: Research Ethics Committee (REC) approval has been granted for this study by Yorkshire and the Humber, Leeds West Research Ethics Committee (18/YH/0371) and due to the nature of the patients enrolled with septic shock, capacity for informed consent is likely to be lacking. Therefore, a personal consultee (friend or relative) will be consulted or a nominated consultee (clinician) in their absence. After capacity is regained, consent will then be sought from the patient in accordance with the Mental Capacity Act, UK (2005). This consent process has been approved following REC review. Results will be published in a relevant peer-reviewed journal and presented at academic meetings.

A comparison of two methods of heart rate variability assessment at high altitude.

Heart rate variability (HRV) is a useful index of autonomic function and has been linked to the development of high altitude (HA) related illness. However, its assessment at HA has been undermined by the relative expense and limited portability of traditional HRV devices which have mandated at least a minute heart rate recording. In this study, the portable ithlete™ HRV system, which uses a 55 s recording, was compared with a reference method of HRV which utilizes a 5 min electrocardiograph recording (CheckMyHeart™ ). The root mean squares of successive R-R intervals (RMSSD) for each device was converted to a validated HRV score (lnRMSSD × 20) for comparison. Twelve healthy volunteers were assessed for HRV using the two devices across seven time points at HA over 10 days. There was no significant change in the HRV values with either the ithlete (P = 0·3) or the CheckMyHeart™ (P = 0·19) device over the seven altitudes. There was also a strong overall correlation between the ithlete™ and CheckMyHeart™ device (r = 0·86; 95% confidence interval: 0·79-0·91). The HRV was consistently, though non-significantly higher with ithlete™ than with the CheckMyHeart™ device [mean difference (bias) 1·8 l; 95% CI -12·3 to 8·5]. In summary, the ithlete™ and CheckMyHeart™ system provide relatively similar results with good overall agreement at HA.