Re-evaluation of Pre-pump Arterial Pressure to Avoid Inadequate Dialysis and Hemolysis: Importance of Prepump Arterial Pressure Monitoring in Hemodialysis Patients

Hemolysis in Hemodialysis, Secondary to Severe Vena Cava Stenosis

Complications in hemodialysis patients are increasingly rare thanks to advances in technology, including more compatible membranes, more flexible lines, safety in water treatments, alarms in the circuit, and standardization in dialysate fluids plus exhaustive chemical and microbiological tests. In addition, it is highly unusual having hemolysis on hemodialysis; however, it is a life-threatening complication, so the cause must be identified and early managed. The etiology can be chemical or mechanical; however, so far, there are no reports in the literature of an association with severe stenosis of the vena cava, as it is described in the case reported here, where a patient presented hemolysis in two hemodialysis sessions, without initially being possible to find the cause; the only identifiable factor was that he had a dysfunctional tunneled jugular catheter, with a history of difficult vascular access. The patient underwent interventional radiology, finding 99% stenosis of the vena cava, which prevented the passage of the contrast agent to the atrium. Angioplasty and catheter replacement were performed, with a resolution of the complication; the subsequent dialysis therapies were satisfactory.

How to Reduce the Risk of Arteriovenous Fistula Dysfunction by Observing Prepump Arterial Pressure during Hemodialysis: A Multicenter Retrospective Study

OBJECTIVE

Prepump arterial (Pa) pressure indicates the ease or difficulty with which the blood pump can draw blood from the vascular access (VA) during hemodialysis. Some studies have suggested that the absolute value of the Pa pressure to the extracorporeal blood pump flow (Qb) ratio set on the machine (|Pa/Qb|) can reflect the dysfunction of VA. This study was conducted to explore the impact of arteriovenous fistula (AVF) dysfunction and to explore the clinical reference value of |Pa/Qb|.

METHODS

We retrospectively identified adults who underwent hemodialysis at 3 hospitals. Data were acquired from electronic health records. We evaluated the pattern of the association between |Pa/Qb| and AVF dysfunction during 1 year using a Cox proportional hazards regression model with restricted cubic splines. Then, the patients were grouped based on the results, and hazard ratios were compared for different intervals of |Pa/Qb|.

RESULTS

A total of 490 patients were analyzed, with an average age of 55 (44, 66) years. There were a total of 85 cases of AVF dysfunction, of which 50 cases were stenosis and 35 cases were thrombosis. There was a U-shaped association between |Pa/Qb| and the risk of AVF dysfunction (p for nonlinearity <0.001). |Pa/Qb| values <0.30 and >0.52 increased the risk of AVF dysfunction. Compared with the group with a |Pa/Qb| value between 0.30 and 0.52, the groups with |Pa/Qb| <0.30 and |Pa/Qb| >0.52 had a 4.04-fold (p = 0.002) and 3.41-fold (p < 0.001) greater risk of AVF dysfunction, respectively.

CONCLUSIONS

The appropriate range of |Pa/Qb| is between 0.30 and 0.52. When |Pa/Qb| is <0.30 or >0.52, the patient's AVF function or Qb setting should be reevaluated to prevent subsequent failure.

Hemodialysis efficiency management from the viewpoint of blood removal pressure

Degradation of dialysis efficiency during hemodialysis, caused by incompatible indwelling needle size or increase in hematocrit, is a serious problem that can threaten a patient's life. This study aims to derive a quantitative index for determining the indwelling needle diameter that can maintain an appropriate blood flow rate, and presents an effective method to prevent a decrease in the actual blood flow rate. The relationships between the set flow rate and various parameters such as indwelling needle diameter, blood viscosity, and arterial line pressure are analyzed. A simple and reliable method for estimating the actual blood flow rate is derived from these relationships. A correlation between viscosity and actual blood flow rate is estimated adequately by regression analysis using a least-squares method. The relationship between Reynolds number and the flow rate reduction ratio is also evaluated. A new parameter (simple estimation method for actual blood flow) is derived by measuring the blood removal pressure. A pump control approach that uses blood removal pressure is suggested, which can be a future research direction in the field of hemodialysis.

It is time to implement prepump arterial pressure monitoring during hemodialysis: A retrospective multicenter study

INTRODUCTION

Prepump arterial pressure (Pa) indicates the ease or difficulty with which the blood pump can draw blood from vascular access (inflow) during hemodialysis. The absolute prepump arterial pressure to blood pump speed (Qb) ratio (|Pa/Qb|) may reflect the dysfunction of other vascular accesses. There is no consensus on the impact of |Pa/Qb| on arteriovenous fistula dysfunction. This study aimed to demonstrate the impact of |Pa/Qb| on arteriovenous fistula dysfunction.

METHODS

In this retrospective analysis, 490 hemodialysis patients with arteriovenous fistula from three hospitals were enrolled. Data were extracted from the I-Diapro database and hospital case systems. The absolute values for |Pa/Qb| and other data collected in the first month of enrollment were used to predict arteriovenous fistula dysfunction and determine the |Pa/Qb| cutoff value. Based on this value, patients were grouped, and 1-year arteriovenous fistula function was analyzed. Patients were followed until arteriovenous fistula dysfunction, until access type replacement, or for 12 months.

RESULTS

The area under the receiver operating characteristic curve for fistula dysfunction over 1 year was 0.65, with an optimal |Pa/Qb| value, sensitivity, and specificity of 0.499, 60.7%, and 72.6%, respectively. |Pa/Qb| > 0.499 was associated with earlier intervention (317.37 ± 7.68 vs 345.96 ± 3.64 days), lower survival (p < 0.001), and a 3.26-fold greater risk of arteriovenous fistula dysfunction (p < 0.001) than |Pa/Qb| ⩽ 0.499.

CONCLUSIONS

|Pa/Qb| was an independent risk factor for arteriovenous fistula dysfunction. Nurses should emphasize |Pa/Qb| monitoring and properly set blood pump speed according to this ratio to protect arteriovenous fistula function. |Pa/Qb| > 0.499 might be a predictive measure of arteriovenous fistula dysfunction.

Enhancing dialyser clearance-from target to development

Products of metabolism accumulate in kidney failure and potentially have toxic effects. Traditionally these uraemic toxins are classified as small, middle-sized and protein-bound toxins, and clearance during dialysis is affected by diffusion, convection and adsorption. As current dialysis practice effectively clears small solutes, increasing evidence supports a toxic effect for middle-sized and protein-bound toxins. Therefore, newer approaches to standard dialysis practice are required to look beyond urea clearance. Current dialysers have been developed to effectively clear small solutes and secondly to increase middle-sized toxin clearances. However, there is no ideal dialyser which can effectively clear all uraemic toxins. Advances in nanotechnology have led to improvements in manufacturing, with the production of smoother membrane surfaces and uniformity of pore size. The introduction of haemodiafiltration has led to changes in dialyser design to improve convective clearances. Both diffusional and convectional clearances can be increased by changing dialyser designs to alter blood and dialysate flows, and novel dialyser designs using microfluidics offer more efficient solute clearances. Adjusting surface hydrophilicity and charge alter adsorptive properties, and greater clearance of protein-bound toxins can be achieved by adding carbon or other absorptive monoliths into the circuit or by developing composite dialyser membranes. Other strategies to increase protein-bound toxins clearances have centred on disrupting binding and so displacing toxins from proteins. Just as the hollow fibre design replaced the flat plate dialyser, we are now entering a new era of dialyser designs aimed to increase the spectrum of uraemic toxins which can be cleared by dialysis.

Artificial Organs 2015: A Year in Review

In this Editor's Review, articles published in 2015 are organized by category and briefly summarized. We aim to provide a brief reflection of the currently available worldwide knowledge that is intended to advance and better human life while providing insight for continued application of technologies and methods of organ Replacement, Recovery, and Regeneration. As the official journal of The International Federation for Artificial Organs, The International Faculty for Artificial Organs, the International Society for Rotary Blood Pumps, the International Society for Pediatric Mechanical Cardiopulmonary Support, and the Vienna International Workshop on Functional Electrical Stimulation, Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. We take this time also to express our gratitude to our authors for providing their work to this journal. We offer our very special thanks to our reviewers who give so generously of their time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers, the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.