Abstract
Background
Emergency haemodialysis (HD) is a therapeutic procedure performed in serious clinical situations. This study investigated venous Doppler ultrasound parameters for predicting emergency HD in patients on routine HD treatment for end-stage renal disease in the emergency department (ED).
Method
Adult patients on a routine HD program in a tertiary care ED between April and December 2022 were enrolled in the study. Inferior vena cava, hepatic, and portal vein flow parameters and the venous excess ultrasound (VExUS) score calculated from these parameters were noted in order to predict emergency HD indications. Hyperkalaemia, hypervolemia, missing more than one session, uremic findings, and metabolic acidosis were regarded as emergency HD indications.
Results
One hundred twenty-nine venous ultrasound examinations were performed on 43 patients with routine HD during the study period. The rate of emergency HD was 30.2%. The most common indication of it was hypervolemia (76.9%), followed by missing more than one session (23.1%). Only the portal vein had an AUC value of 0.714, with a sensitivity of 61.5% and specificity of 83.3% for predicting emergency HD. Other parameters including the IVC, hepatic vein, and VExUS score were of no diagnostic value.
Conclusion
The findings of this study show that only the portal vein Doppler flow parameter has very limited diagnostic value for emergency HD in patients on a routine HD program in the ED. This study can serve as a guide to further research.
Keywords: Haemodialysis, Venous Doppler, Emergency department, VExUS
Introduction
Patients receiving maintenance haemodialysis (HD) are often frail due to advanced age and multiple comorbidities and are frequent users of emergency departments (EDs). These patients visit EDs eight times more frequently than the general population [1]. Additionally, patients with end-stage renal disease (ESRD) are more likely to be admitted to the intensive care unit and hospital and are more likely to undergo radiological and blood tests than patients without kidney disease [2, 3]. Emergency HD can be necessary in these cases due to respiratory and/or cardiovascular instability, and one in three patients requires hospitalization under these circumstances [4]. While the indication for emergency HD may be obvious to emergency physicians in some cases, such as a missed session, it can be vague when complicated by different clinical conditions. This uncertainty can lead to an increased length of stay in the ED and unnecessary requests for nephrological consultations or HD.
Lung ultrasound has been one of the most studied imaging methods for HD patients in recent years. Areas of use include the evaluation of volume status and prognosis [5]. Venous system ultrasound (VUS) of abdominal organs has been rarely investigated when determining the relationship between VUS parameters and the management of HD patients [6]. A Venous Excess Ultrasound (VExUS) scoring system comprising a combination of inferior vena cava (IVC), portal, hepatic, and intrarenal veins has been recently introduced to predict cardiorenal acute kidney injury in critically ill patients [7]. This is a relatively new score that needs to be tested in different patient groups. Similarly, this score has never been investigated in the management of HD patients.
The aim of this study was to determine the value of VUS in predicting the need for emergency HD in HD patients in the ED. This can then show whether VUS represents an alternative diagnostic parameter for patients in need of emergency HD.
Methods
Study design and population
This prospective pilot study was conducted in the tertiary care ED of a university hospital in Turkey between April and December 2022. The hospital ethics committee approved the research (No. 04-2022/298), and the study protocol was previously published on ClinicalTrials.gov (NCT05337384). Written consent forms were obtained from all patients.
Adult patients on regular HD programs who presented themselves to the ED were enrolled in the study, regardless of their complaints. Patients were primarily treated by emergency physicians for simple diagnoses such as gastroenteritis or headaches. A nephrology consultation was requested if advanced therapies were needed, such as hospitalization, parenteral medications, or HD. The exclusion criteria were pregnancy, cirrhosis, hepatic malignancy, inability to provide consent, receipt of peritoneal dialysis, and presentation due to cardiac arrest. Patients were also excluded if VUS was not completed within the first six hours of presentation, as excess therapies may alter the VUS parameters.
Indications for emergency HD included hyperkalaemia, hypervolemia, missing more than one session, uremic findings, and metabolic acidosis [8]. Hypervolemia and uremic findings were determined based on the patient’s clinical condition and physical examination. Weekly meetings were held by a nephrologist and an emergency physician to review indications and diagnoses. Demographics, vital signs, and one-month mortality were also recorded during the study.
Ultrasound examination
VUS was performed and measured by an emergency physician with at least eight years’ experience in bedside ultrasound and two experienced radiologists. The IVC was taken from the subcostal window, and its maximum diameter was measured at 3–4 cm from the right atrium. After obtaining pulsed wave flow patterns from the main portal vein and the hepatic vein closest to the IVC from the right coronal plane, the waveform shape and pulsatility were noted. If the portal vein waveform showed minimal variations during the cardiac cycle (portal pulsatility index [PPI] < 30%), it was considered normal. If PPI ranged from 30 to 50%, it was considered mildly abnormal, and if it was ≥ 50%, severely abnormal. For the hepatic vein waveform, if the systolic (S) component was equal to or greater than the diastolic (D) component, then it was deemed normal. On the other hand, if the S component was smaller in magnitude than the D component, then it was deemed mildly abnormal, while if the S component was reversed towards the heart, it was considered severely abnormal.
The intrarenal vein was not included in the ultrasound examination because most patients had an atrophic kidney or no kidney that could be measured. Flow patterns were classified according to VExUS scores [7] (Fig. 1), while examinations were completed with an ECG connection at the head of the bed at a position of 0 to 45 degrees. The Valsalva manoeuvre was avoided because it alters the flow pattern. Finally, the GE Logiq S7 Ultrasound (GE Medical Systems, Milwaukee, WI) system was employed.
Fig. 1.
Normal and abnormal venous Doppler patterns of VExUS score
Statistical analysis
Statistical analyses were performed using MedCalc® Version 15.8 software (MedCalc Software bvba, Ostend, Belgium). Continuous variables were expressed as median values and interquartile ranges (IQRs) or mean plus standard deviation (SD), and categorical variables as percentages and frequencies. The area under the receiver operating characteristic curve (AUC-ROC) was calculated to determine relationships between VUS parameters and the need for emergency HD. Diagnostic probability tests consisting of sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio values, as well as their 95% confidence intervals (CI), were reported based on the cut-off values. An α critical value of 0.05 was regarded as statistically significant.
Results
One hundred twenty-nine venous ultrasound examinations were conducted on 43 patients receiving routine HD during the study period. The patients’ median age was 65 (IQR 53–74), and 58.1% were men. The most common diagnoses were generalized oedema and chest pain/tachycardia (23.3% for both). Hypertension was present in 74.4% of the patients, diabetes mellitus in 41.9%, and coronary artery disease in 29.5%. Fistula was the most commonly used HD access at 62.8%. One-month mortality was observed in two patients (Table 1).
Table 1.
Demographics of patients on haemodialysis in the emergency department
| Emergency haemodialysis (+) n = 13 |
Emergency haemodialysis (–) n = 30 | |
|---|---|---|
| Male, n(%) | 10 (77) | 15 (50) |
| Age, median (IQR) | 64 (49–70) | 65 (52–74) |
| Vital signs, median (IQR) | ||
| • Systolic, /mmHg | 138 (112–180) | 141 (118–162) |
| • Diastolic, /mmHg | 83 (68–102) | 79 (66–92) |
| • Pulse, /min | 89 (78–98) | 95 (84–102) |
| • Saturation, % | 91 (84–96) | 95 (93–97) |
| Diagnosis, n(%) | ||
| • Generalized edema | 9 (69.2) | 1 (3.3) |
| • Chest pain/tachycardia | 2 (15.4) | 8 (26.7) |
| • Fistula/catheter-related | 1 (7.7) | 7 (23.3) |
| • GI pathologies | – | 5 (16.7) |
| • Pneumonia | 1 (7.7) | 2 (6.7) |
| • CVD/syncope | – | 3 (10) |
| • Other | – | 4 (13.3) |
| Comorbidities, n(%) | ||
| • Hypertension | 10 (76.9) | 22 (73.3) |
| • Diabetes mellitus | 4 (30.8) | 14 (46.7) |
| • CAD | 4 (30.8) | 13 (43.3) |
| • CHF | 3 (23.1) | 5 (16.7) |
| Mortality, n(%) | 1 (7.7) | 1 (3.3) |
GI gastrointestinal, CVD cerebrovascular disease, CAD coronary artery disease, CHF congestive heart failure
The rate of emergency HD was 30.2%. The most common indication for this was hypervolemia (76.9%), followed by missing more than one session (23.1%). No other indications were observed.
A maximum IVC diameter greater than 19 mm exhibited an AUC value of 0.579, with a sensitivity of 50% and specificity of 74% for predicting emergency HD. A hepatic vein ≤ grade 2 exhibited an AUC value of 0.535, with a sensitivity of 100% and specificity of 6.4%, while a portal vein > grade 1 exhibited an AUC value of 0.714, with a sensitivity of 61.5% and specificity of 83.3%. Finally, a VExUS score > grade 0 exhibited an AUC value of 0.573, with a sensitivity of 41% and specificity of 74% (Tables 2 and 3).
Table 2.
A comparison of venous ultrasound parameters in groups with and without emergency haemodialysis
| Emergency haemodialysis (+) n = 13 |
Emergency haemodialysis (–) n = 30 |
|
|---|---|---|
| Inferior vena cava, mm median (IQR) | 19 (14–21) | 17 (14–20) |
| Hepatic vein, n(%) | ||
| • Grade 1 | 11 (84.6) | 23 (76.7) |
| • Grade 2 | 2 (15.4) | 5 (16.7) |
| • Grade 3 | – | 2 (6.7) |
| Portal vein, n(%) | ||
| • Grade 1 | 5 (38.5) | 25 (83.3) |
| • Grade 2 | 8 (61.5) | 4 (13.3) |
| • Grade 3 | – | 1 (3.3) |
| VExUS score, n(%) | ||
| • Grade 0 | 8 (61.5) | 22 (73.3) |
| • Grade 1 | 5 (38.5) | 7 (23.3) |
| • Grade 2 | – | – |
| • Grade 3 | – | 1 (3.3) |
Table 3.
Diagnostic accuracy of venous ultrasound parameters for emergency haemodialysis in patients on routine haemodialysis
| AUC (95% CI) |
Cut-off value | Sensitivity % (95% CI) |
Specificity % (95% CI) |
PLR (95% CI) |
NLR (95% CI) |
|
|---|---|---|---|---|---|---|
| Inferior vena cava, mm | 0.579 (0.419–0.728) | > 19 | 50 (21.1–78.9) | 74 (55.4–88.1) | 1.94 (0.9–4.4) | 0.67 (0.4–1.2) |
| Hepatic vein (3 grades) | 0.535 (0.377–0.688) | ≤ 2 | 100 (73.5–100) | 6.4 (0.8–21.4) | 1.07 (1.0–1.2) | – |
| Portal vein (3 grades) | 0.714 (0.556–0.841) | > 1 | 61.5 (31.6–86) | 83.3 (65.3–94.4) | 3.7 (1.5–9.2) | 0.46 (0.2–0.9) |
|
VExUS score (4 grades) * |
0.573 (0.413–0.722) | > 0 | 41.7 (15.2–72.3) | 74.2 (55.4–88.1) | 1.6 (0.7–4.0) | 0.79 (0.5–1.3) |
*The intrarenal vein grade was not included in the calculation of VExUS scores since it is not possible to examine this in HD patients
Discussion
VUS has become a popular subject in relation to the volume management of critically ill patients in EDs and intensive care units. To the best of our knowledge, no previous study has investigated multiorgan VUS examination in patients with routine HD. The findings of this pilot study showed that portal vein flow parameters were of diagnostic value for predicting emergency HD in patients on routine HD in the ED, while the IVC, hepatic vein, and VExUS score had no such accuracy.
Patients with routine HD visit EDs more frequently than the general population due to HD complications, multiple comorbidities, and older age. They also frequently require advanced therapies or hospitalization [9]. Emergency HD is sometimes needed for these patients during these presentations due to hypervolemia, uraemia, or missing a session. The rate of emergency HD in the current study was 30.2%. The equivalent rate was 5.5% in Taiwanese patients diagnosed for the first time with chronic renal failure [10]. Another study reported a figure of 7.2% in patients in Canada receiving maintenance HD who required ambulance transport to the ED [11]. These differences may be due to different study methodologies and regions.
IVC has been one of the most commonly studied ultrasound parameters in HD patients for predicting dry weight, ultrafiltration, or outcome [12]. Hafiz et al. [13] reported that IVC measurements in 30 ESRD patients changed significantly after HD. Similarly, Annamalai et al. showed that IVC measurements changed significantly after HD, but that these were not correlated with ultrafiltration volume in 50 stable HD patients in India [14]. Kaptein et al. [15] reported that an IVC collapsibility index < 20 exhibited an AUC value of 0.77 for ultrafiltration ≥ 0.5 L in 67 ESRD patients. In the current study, the median IVC maximum diameter was higher in patients requiring emergency HD, although it had no diagnostic accuracy for emergency HD.
Doppler flow patterns in abdominal organs have been rarely studied in HD patients, regardless of whether they are seen in inpatient or outpatient clinics. Ergün et al. [6] reported that the mean flow velocities and volume flow of the portal vein decreased after HD in 20 ESRD patients. In the present study, the Doppler flow patterns of the hepatic and portal veins and the resultant VExUS score combination of these parameters for predicting emergency HD were tested, and only the portal vein flow pattern (> 1 grade) exhibited limited diagnostic accuracy with low sensitivity. There are no other studies in the literature with which to compare this information.
The main limitation of this study was the low number of patients, given that this was a pilot study designed to serve as a guide to further research. The use of bedside ultrasound was still limited in this patient group, as is the case in many healthcare areas. We believe that HD patients with high fragility should undergo more bedside ultrasound examinations during management and follow-up. Another limitation was our inability to capture Doppler flow patterns of the intrarenal vein since the VExUS score was validated with the IVC diameter in addition to three abdominal organ flow patterns: portal, hepatic, and intrarenal. Since it was impossible to obtain in HD patients due to an atrophic kidney, a transplanted kidney, or the absence of any kidney, we calculated this score without intrarenal vein flow patterns, making it harder to interpret whether the score is capable of predicting emergency HD.
Conclusion
This study tested IVC, portal, and hepatic flow patterns, and the VExUS score for predicting emergency HD in patients with routine HD. The results showed that only the portal vein Doppler flow pattern was associated with emergency HD in these patients in the ED.
Author contributions
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by MAA, ÖH, MC, and HŞ. The first draft of the manuscript was written by MAA and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Data availability
The data that support the findings of this study are available from the corresponding author, upon reasonable request.
Declarations
Conflict of interest
The authors have no relevant financial or non-financial interests to disclose.
Ethical approval
This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of University Gazi (No. 04-2022/298).
Consent to participate
Informed consent was obtained from all individual participants included in the study.
Footnotes
Publisher's Note
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author, upon reasonable request.