Intradialytic Hypotension (IDH) is the commonest complication of maintenance haemodialysis and is associated with increased morbidity and mortality. However, there is no standardised definition of IDH, making comparisons between studies difficult. This observational study with a total of 80 patients and over 600 dialysis sessions showed a poor correlation between symptoms and hypotension. Importantly, patients experienced low blood pressure without symptoms, so continuous intradialytic blood pressure monitoring is required to identify this asymptomatic group. In light of these findings, a revised definition of IDH is suggested. This study also aimed to identify predictors of IDH that could be detected in sufficient time to allow a mitigating intervention. A novel non-invasive alternative for continuous blood pressure monitoring is introduced which uses intra-fistula pressure data from the sensors sited in the extracorporeal circuit of the dialysis machine. Results show that in the majority of patients, changes in intra-fistula pressure correlate with blood pressure measurements obtained by a standard oscillometric device. To investigate whether IDH can be predicted, a photoplethysmogram (PPG) waveform was obtained from a pulse oximeter attached to the finger or ear. Continuous PPG monitoring of patients with IDH during dialysis demonstrated that some IDH episodes were predictable using the variation in the PPG baseline with respiration as a surrogate for low blood volume. Additionally, the area under the curve of the PPG waveform can be used as a surrogate for cardiac output and peripheral vascular tone, resulting in a reasonable predictor for potentially critical changes in blood pressure during dialysis. Individually, the novel metrics described here are limited in their identification of IDH in all patients affected, but in combination they may be used to develop a multi-parameter predictive model. The relative merits of personalised versus population-based models are explored and a conclusion is drawn that personalised multi-parameter data fusion modelling for haemodialysis patients would be an important area for future work.

Background: Intradialytic hypotension is a potential complication experienced by patients with end-stage renal disease who receive hemodialysis. This complication occurs during the dialysis treatment in 15-30% of all treatments. The multiple comorbidities that exist in hemodialysis patients predispose them to recurrent intradialytic hypotension episodes. Recurrent intradialytic hypotensive episodes can result in negative short-term and long-term clinical consequences. Short-term consequences include complications such as ischemic events (e.g., heart attacks, strokes), clotting of patient dialysis access, or heart rhythm abnormalities. Long-term consequences include end-organ damage, increased cardiovascular morbidity, and a higher mortality rate. Problem Statement: Available nursing interventions used to treat intradialytic hypotension such as decreased dialysis fluid temperature, changes in the calcium and sodium concentrations in the dialysis fluid and oral medication have limited success. Another existing technological intervention called blood volume monitoring shows greater potential success but is currently underutilized. Purpose: The purpose of this literature review is to synthesize current literature on blood volume monitoring technology used to prevent intradialytic hypotension in hemodialysis patients. Methods: A literature review was conducted analyzing pertinent research articles published in the last ten years, in addition to seminal articles. Seventeen articles were retrieved and analyzed that met criteria. Results: Fourteen of the seventeen research studies reached a consensus on the successful use of blood volume monitoring to decrease intradialytic hypotension and the related symptoms. Conclusion: Results of the literature review support the use of blood volume monitoring technology as an effective nursing intervention to prevent intradialytic hypotension in hemodialysis patients.

Bakgrund: Felaktiga torrvikter är ett problem inom hemodialysvården. Det kan orsaka vårdskada i form av komplikationer och lidande, med symtom som trötthet, blodtrycksfall och sendrag för dialyspatienter. Det finns ett behov av implementering av evidensbaserade metoder som minskar risken för fel i torrviktsbestämning. Bioimpedansmätning beskrivs i litteraturen som ett lovande hjälpmedel för bestämning av torrvikt Syfte: Undersöka effekten av bioimpedansledd torrviktskorrigering, på symtom som hemodialyspatienter kan erfara under och efter dialysbehandling. Metod: Experimentell intervention, i form av veckovis korrigering av torrvikt med vägledning av bioimpedansspektroskopi, utförd med single-case-design och multiple base- line. Urvalet bestod av sex strategiskt utvalda hemodialyspatienter. Resultat: Interventionen hade ringa effekt på förekomst av intradialytiska symtom. Bland studiens deltagare förelåg sällan samvariation mellan förekomst av blodtrycksfall och/eller sendrag och felaktig torrvikt. Däremot förelåg positivt samband mellan symtombörda och differens mellan predialytisk vikt och torrvikt. Bioimpedansmätningarna avslöjade dessutom kliniskt relevant varians i torrvikt över tid. Slutsats: Även om interventionen inte hade bevisad effekt på de beroende variablerna, är det inte uteslutet att noga monitorering av vätskebalans med bioimpedansmätare och korrigering av torrvikt kan förebygga uppkomst av intradialytiska symtom. I vissa subgrupper kan bioimpedansmätning också bidra till förbättrad blodtryckskontroll. Dialyspatienters torrvikt visade sig kunna variera med flera kilogram per vecka, varför fixerad torrvikt kan vara ett dilemma för vissa individer. Bioimpedansmätning bland hemodialyspatienter kan underlätta identifiering av individuella riskfaktorer för intradialytiska symtom och vara ett verktyg som bidrar till utvecklingen mot personcentrerad vård med större patientdelaktighet och individualiserade mål. / Background: Inaccurate dry weight is a problem in hemodialysis care. It can cause health damage in the form of suffering and complications such as fatigue, intradialytic hypotension (IDH) and cramps for dialysis patients. There is a need for implementation of evidence-based practices that reduce the risk of error in dry weight assessment. Bioelectrical impedance is described in literature as a promising tool for assessment of dry weight.Objective: Examine the effect of bioimpedance guided dry weight correction on symptoms that hemodialysis patients may experience during and after dialysis. Method: Experimental intervention in the form of weekly assessment of dry weight with the guidance of bioimpedance spectroscopy, performed with single-case design and multiple baseline. The sample consisted of six strategically selected hemodialysis patients. Results: The intervention had little effect on the prevalence of intradialytic symptoms. Among the study participants, the occurrence of IDH and / or cramps and inaccurate dry weight rarely correlated. However, there was positive correlation between symptoms and the difference between predialytic weight and dry weight. Bioimpedance measurement also revealed clinically relevant variance in dry weight over time. Conclusion: Although the intervention had no proven effect on the dependent variables, it is possible that careful monitoring of fluid balance with bioimpedance measurement and correction of dry weight can help prevent intradialytic symptoms. In certain subgroups bioelectrical impedance may also contribute to improved blood pressure control. Dialysis patients' dry weight was found to vary several kilograms per week; fixated dry weight may therefore be a dilemma for some individuals. Bioelectrical impedance among hemodialysis patients may facilitate identification of individual risk factors for intradialytic symptoms and be a tool that contributes to the development of person-centered care with greater patient participation and individualized goals.

Volume overload is a common feature in patients on haemodialysis (HD). This contributes significantly to the cardiovascular disease burden seen in these patients. Clinical assessments of the volume state are often inaccurate. Techniques such as interdialytic blood pressure, relative blood volume monitoring, bioimpedance are available to improve clinical effectives. However all these techniques exhibit significant shortcomings in their accuracy, reliability and applicability at the bed side. We evaluated the usefulness of a dual compartment monitoring technique using Continuous Segmental Bioimpedance Spectroscopy (CSBIS) and Relative Blood Volume (RBV) as a tool to assess hydration status and determine dry weight. We also sought to evaluate the role of Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP) as a volume marker in dialysis patients. The Retrospective analysis of a historical cohort (n = 376, 55 Diabetic) showed a significant reduction in post-dialysis weights in the first three months of dialysis (72.5 to 70kg, p<0.027) with a non-significant increase in weight between months 6-12. The use of anti-hypertensive agents reduced insignificantly in the first 3 months, increased marginally between months 3-6 and significantly increased over the subsequent 6 months. The residual urea clearance (KRU) fell and dialysis times increased. The cohort was very different to that dialysing at Tassin and showed a dissociation between weight reduction and BP control. This may relate to occult volume overload. CSBIS-RBV monitoring in 9 patients with pulse ultrafiltration (pulse UF) showed distinct reproducible patterns relating to extra cellular fluid (ECF) and RBV rebound. An empirical Refill Ratio was then used to define the patterns of change and this was related to the state of their hydration. A value closer to unity was consistent with the attainment of best achievable target weight. The refill ratio fell significantly between the first (earlier) and third (last) rebound phase (1.97 ± 0.92 vs 1.32 ± 0.2). CSBIS monitoring was then carried out in 31 subjects, whilst varying dialysate composition, temperature and patient posture to analyse the effects of these changes on the ECF trace and to ascertain whether any of these interventions can trigger a change in the slope of the ECF trace distinct to that caused by UF. Only, isovolemic HD caused a change in both RBV and ECF in some patients that was explained by volume re-distribution due to gravitational shifts, poor vascular reactivity, sodium gradient between plasma and dialysate and the use of vasodilating antihypertensive agents. This has not been described previously. These will need to be explored further. The study did demonstrate a significant lack of comparability of absolute values of RECF between dialysis sessions even in the same patient. This too has not been described previously. This is likely to be due to subtle changes in fluid distribution between compartments. Therefore a relative changes must be studied. This sensitivity to subtle changes may increase the usefulness of the technique for ECF tracking through dialysis. The potential of dual compartment monitoring to track volume changes in real time was further explored in 29 patients of whom 21 achieved weight reductions and were able to be restudied. The Refill Ratio decreased significantly in the 21 patients who had their dry weights reduced by 0.95 ± 1.13 kg (1.41 ± 0.25 vs 1.25 ± 0.31). Blood pressure changes did not reach statistical significance. The technique was then used to examine differences in vascular refill between a 36oC and isothermic dialysis session in 20 stable prevalent patients. Pulse UF was carried out in both these sessions. There were no significant differences in Refill Ratios, energy removed and blood pressure response between the two sessions. The core temperature (CT) of these patients was close to 36oC and administering isothermic HD did not confer any additional benefit. Mean BNP levels in 12 patients during isovolemic HD and HD with UF did not relate to volume changes. ANP concentrations fell during a dialysis session in 11 patients from a mean 249 ± 143 pg/ml (mean ± SD) at the start of dialysis to 77 ± 65 pg/ml at the end of the session (p<0.001). During isolated UF levels did not change but fell in the ensuing sham phase indicating a time lag between volume loss and decreased generation. (136±99 pg/ml to 101±77.2 pg/ml; p<0.02) In a subsequent study ANP concentrations were measured throughout dialysis and in the post-HD period for 2 hours. A rebound in ANP concentration was observed occurring at around 90 min post-HD. The degree of this rebound may reflect the prevailing fluid state and merit further study. We have shown the utility of dual compartment monitoring with CSBIS-RBV technique and its potential in assessing volume changes in real time in haemodialysis patients. We have also shown the potential of ANP as an independent marker of volume status in the same setting. Both these techniques merit further study.