Isothermic dialysis for hypotension-prone patients

Monitoring peripheral hemodynamic response to changes in blood pressure via photoacoustic imaging

Chronic wounds and amputations are common in chronic kidney disease patients needing hemodialysis (HD). HD is often complicated by drops in blood pressure (BP) called intra-dialytic hypotension. Whether intra-dialytic hypotension is associated with detectable changes in foot perfusion, a risk factor for wound formation and impaired healing remains unknown. Photoacoustic (PA) imaging is ideally suited to study perfusion changes. We scanned the feet of 20 HD and 11 healthy subjects. HD patients were scanned before and after a dialysis session whereas healthy subjects were scanned twice at rest and once after a 10 min exercise period while BP was elevated. Healthy (r = 0.70, p < 0.0001) and HD subjects (r = 0.43, p < 0.01) showed a significant correlation between PA intensity and systolic BP. Furthermore, HD cohort showed a significantly reduced PA response to changes in BP compared to the healthy controls (p < 0.0001), showing that PA can monitor hemodynamic changes due to changes in BP.

Major Outcomes With Personalized Dialysate TEMPerature (MyTEMP): Rationale and Design of a Pragmatic, Registry-Based, Cluster Randomized Controlled Trial

BACKGROUND

Small randomized trials demonstrated that a lower compared with higher dialysate temperature reduced the average drop in intradialytic blood pressure. Some observational studies demonstrated that a lower compared with higher dialysate temperature was associated with a lower risk of all-cause mortality and cardiovascular mortality. There is now the need for a large randomized trial that compares the effect of a low vs high dialysate temperature on major cardiovascular outcomes.

OBJECTIVE

The purpose of this study is to test the effect of outpatient hemodialysis centers randomized to (1) a personalized temperature-reduced dialysate protocol or (2) a standard-temperature dialysate protocol for 4 years on cardiovascular-related death and hospitalizations.

DESIGN

The design of the study is a pragmatic, registry-based, open-label, cluster randomized controlled trial.

SETTING

Hemodialysis centers in Ontario, Canada, were randomized on February 1, 2017, for a trial start date of April 3, 2017, and end date of March 31, 2021.

PARTICIPANTS

In total, 84 hemodialysis centers will care for approximately 15 500 patients and provide over 4 million dialysis sessions over a 4-year follow-up.

INTERVENTION

Hemodialysis centers were randomized (1:1) to provide (1) a personalized temperature-reduced dialysate protocol or (2) a standard-temperature dialysate protocol of 36.5°C. For the personalized protocol, nurses set the dialysate temperature between 0.5°C and 0.9°C below the patient's predialysis body temperature for each dialysis session, to a minimum dialysate temperature of 35.5°C.

PRIMARY OUTCOME

A composite of cardiovascular-related death or major cardiovascular-related hospitalization (a hospital admission with myocardial infarction, congestive heart failure, or ischemic stroke) captured in Ontario health care administrative databases.

PLANNED PRIMARY ANALYSIS

The primary analysis will follow an intent-to-treat approach. The hazard ratio of time-to-first event will be estimated from a Cox model. Within-center correlation will be considered using a robust sandwich estimator. Observation time will be censored on the trial end date or when patients die from a noncardiovascular event.

TRIAL REGISTRATION

www.clinicaltrials.gov; identifier: NCT02628366.

Effect of Lowering the Dialysate Temperature in Chronic Hemodialysis: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Lowering the dialysate temperature may improve outcomes for patients undergoing chronic hemodialysis. We reviewed the reported benefits and harms of lower temperature dialysis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We searched the Cochrane Central Register, OVID MEDLINE, EMBASE, and Pubmed until April 15, 2015. We reviewed the reference lists of relevant reviews, registered trials, and relevant conference proceedings. We included all randomized, controlled trials that evaluated the effect of reduced temperature dialysis versus standard temperature dialysis in adult patients receiving chronic hemodialysis. We followed the Grading of Recommendations Assessment, Development and Evaluation approach to assess confidence in the estimates of effect (i.e., the quality of evidence). We conducted meta-analyses using random effects models.

RESULTS

Twenty-six trials were included, consisting of a total of 484 patients. Compared with standard temperature dialysis, reduced temperature dialysis significantly reduced the rate of intradialytic hypotension by 70% (95% confidence interval, 49% to 89%) and significantly increased intradialytic mean arterial pressure by 12 mmHg (95% confidence interval, 8 to 16 mmHg). Symptoms of discomfort occurred 2.95 (95% confidence interval, 0.88 to 9.82) times more often with reduced temperature compared with standard temperature dialysis. The effect on dialysis adequacy was not significantly different, with a Kt/V mean difference of -0.05 (95% confidence interval, -0.09 to 0.01). Small sample sizes, loss to follow-up, and a lack of appropriate blinding in some trials reduced confidence in the estimates of effect. None of the trials reported long-term outcomes.

CONCLUSIONS

In patients receiving chronic hemodialysis, reduced temperature dialysis may reduce the rate of intradialytic hypotension and increase intradialytic mean arterial pressure. High-quality, large, multicenter, randomized trials are needed to determine whether reduced temperature dialysis affects patient mortality and major adverse cardiovascular events.

Identification of patients prone to hypotension during hemodialysis based on the analysis of cardiovascular signals

Intradialytic hypotension (IDH) is a major complication during hemodialysis treatment, and therefore it is highly desirable to identify, at an early stage during treatment, whether the patient is prone to IDH. Heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were analyzed during the first 30 min of treatment to assess information on the autonomic nervous system. Using the sequential floating forward selection method and linear classification, the set of features with the best discriminative power was selected, resulting in an accuracy of 92.1%. Using a classifier based on the HRV features only, thereby avoiding that continuous blood pressure has to be recorded, accuracy decreased to 90.2%. The results suggest that an HRV-based classifier is useful for determining whether a patient is prone to IDH at the beginning of the treatment.

Use of online blood volume and blood temperature monitoring during haemodialysis in critically ill patients with acute kidney injury: a single-centre randomized controlled trial

BACKGROUND

Little is known about the clinical impact on cardiovascular stability during intermittent haemodialysis (IHD) for acute kidney injury (AKI) of online monitoring devices that control blood volume (BV) and blood temperature in the intensive care unit (ICU) setting. We compared different dialysis treatment modalities with or without these new systems among critically ill patients requiring IHD.

METHODS

In a prospective single-centre three-arm randomized controlled trial, 600 dialysis sessions in 74 consecutive AKI critically ill patients were involved to assess intradialytic hypotension. Standard dialysis therapy with constant ultrafiltration (UF) rate, cool dialysate and high sodium conductivity (Treatment A) was compared to regimens with adjunctive interventions including BV control (Treatment B) and the combination of BV and active blood temperature control (Treatment C). Each dialysis session was randomly assigned to one of the three treatment arms and served as statistical unit.

RESULTS

Five hundred and seventy-two dialysis sessions were analysed (188, 190 and 194 in Treatments A, B and C, respectively). Hypotension occurred in 16.6% treatments, with similar rates among the arms. Haemodynamic parameters and dialysis-related complications did not differ between therapies. Based on generalized estimating equation adjusted to dialysate sodium conductivity, higher Sequential Organ Failure Assessment the day of dialysis session, the need for vasopressors and lower systolic blood pressure at the onset of the session were identified as independent predictors of hypotensive episodes, whereas regimens containing the new online monitors were not.

CONCLUSIONS

These results suggest that both actively controlled body temperature and UF profiled by online monitoring systems have no significant impact on the incidence of intradialytic hypotension in the ICU setting. Further research is needed before the use of these new sophisticated automatic methods can be applied routinely to the ICU setting.

Urea kinetics and intermittent dialysis prescription in small animals

Hemodialysis improves survival for animals with acute kidney injury beyond what would be expected with conventional management of the same animals. Clinical evidence and experience in human patients suggest a role for earlier intervention with renal replacement to avoid the morbidity of uremia and to promote better metabolic stability and recovery. For a large population of animal patients, it is the advanced standard for the management of acute and chronic uremia, life-threatening poisoning, and fluid overload for which there is no alternative therapy.

Predilution hemodiafiltration displays no hemodynamic advantage over low-flux hemodialysis under matched conditions

BACKGROUND

It is the prevailing view that convective dialysis techniques stabilize blood pressure. The aim of this study was to compare the intrasession hemodynamics during high-dose predilution hemodiafiltration (HDF) and low-flux hemodialsis, under strict controlled conditions.

METHODS

Twelve stable hemodialysis patients were investigated in a randomized crossover blinded controlled trial. The patients were allocated to one session of predilution HDF (substitution fluid 1.20 +/- 0.10 L/kg body weight) and one session of hemodialysis at 4(1/2) hours. To eliminate confounding factors, dialysis dose, ultrafiltration volume and arterial temperature were matched. At the start of the dialysis the patients' core temperature was "locked" by an automatic feedback system regulating the dialysate temperature; thereby, patients' temperature was kept stable throughout the whole treatment. The calcium-ion concentration in the substitution/dialysis fluid was 1.25 mmol/L. Cardiac output was measured hourly by the ultrasound velocity dilution method.

RESULTS

Mean blood pressure, cardiac output, stroke volume, cardiac work, and relative blood volume was significantly reduced in both treatments. Total peripheral resistance increased significantly in both groups. Ultrafiltration volume, cardiopulmonary recirculation, Kt/V, and total energy transfer were similar for hemodialysis and HDF. The pulse rate showed no significant change throughout both sessions. No significant differences were revealed between hemodialysis and HDF.

CONCLUSION

The hemodynamics of predilution HDF and low-flux hemodialysis displayed a similar profile during matched conditions. An acute circulatory benefit of convective solute removal over diffusive could not be demonstrated.

Heat loss and continuous renal replacement therapy

Because of the devastating consequences of thermal imbalance, it is imperative that nurses understand these concepts and apply them to the daily care of their patients. Heat loss, heat conservation, and heat generation interplay to maintain the narrow range that is considered optimal for human cellular function. These concepts factor into patients who are critically ill but are especially important for patients undergoing continuous renal replacement therapy. Many of these types of dialysis expose the individual patient's blood to room temperature dialysate via an extracorporeal circuit 24-hours a day, sometimes for several weeks at a time. Critical care and advanced practice nurses must understand the interplay of the processes of heat loss, conservation, and heat generation to ensure patients undergoing this therapy achieve maximum benefit with the fewest complications possible.

Hemodialysis-Induced Hypotension: Impact of Technologic Advances

Hemodialysis-induced hypotension is one of the most serious complications in renal replacement therapy. The main cause of intradialytic hypotension is hypovolemia due to an imbalance between the amount of fluid removed and the refilling capacity of the intravascular compartment. Hypotension occurs when compensatory mechanisms for hypovolemia are overwhelmed by excessive fluid removal. As long as renal replacement therapy is limited to only a few hours per week, intradialytic hypotension will continue to be a relevant problem. Research has mainly focused on enlarging the compensatory capacity for ultrafiltration-induced hypovolemia. This article critically discusses the technical approaches that have been introduced into therapy in recent years with the promise of reducing dialysis-induced hypotensive episodes.

Hypotensive transfusion reactions can occur with blood products that are leukoreduced before storage

BACKGROUND

Leukoreduction before storage, rather than bedside white blood cell filtration, is recommended to prevent hypotensive transfusion reactions.

STUDY DESIGN AND METHODS

Investigation of hypotensive transfusion reactions during radical prostatectomy in two patients on angiotensin-converting enzyme inhibitors. In Patient A, hypotension occurred during the transfusion of each of the following blood products: 2 units of autologous blood deposited and leukoreduced (LR) before storage; 3 units of allogeneic red cells LR before storage; and 2 units of non-LR acute normovolemic hemodilution (ANH) whole blood. When each of the transfusions was stopped, the blood pressure recovered. In Patient B, hypotension occurred during the transfusion of non-LR ANH whole blood. All implicated units were administered rapidly using a blood infuser at 37 degrees C. Bradykinin (BK) and des-Arg9-BK formation and degradation and the activity of kinin-degrading metallopeptidases were measured in plasma samples from both patients.

RESULTS

Degradation of des-Arg9-BK was severely impaired and the activity of aminopeptidase P severely reduced in Patient A, but not in Patient B. BK degradation was mildly impaired in both patients.

CONCLUSION

Hypotensive reactions can occur with blood products that are LR before storage and non-LR ANH. An inherent defect in the metabolism of kinins may be a risk factor for the development of hypotensive transfusion reactions.

Rationale for the use of blood volume and temperature control devices during hemodialysis

Despite substantial progress in blood purification techniques over the last three decades, treatment-related hypotensive episodes remain one of the major problems in hemodialysis therapy. There are two main reasons for hypotension occurring during dialysis treatments. First, hypovolemia is frequently induced by rapid fluid removal from the blood compartment which is in excess of refilling of fluids from the interstitial space. Second, many patients fail to support blood pressure by adequate vasoconstriction or increased heart rate as a response to hypovolemia. The capacity to respond adequately to volume contraction may be reduced due to patient- or treatment-related factors, among which heat accumulation within the body plays a major role. Recently, two newer technical developments became commercially available for use in hemodialysis therapy: devices for blood volume and blood temperature control were designed to reduce the incidence of intradialytic hypotension. Although blood volume and temperature measurements are easy to perform today, there is some uncertainty in the dialysis community how and when their use may be helpful and in which patients it is indicated. This review critically discusses the application of blood volume- and temperature-measuring devices with regard to their usefulness in the clinical setting.

RENAL RESEARCH INSTITUTE SYMPOSIUM: Temperature Control by the Blood Temperature Monitor

The rationale of temperature control during hemodialysis (HD) is to prevent heat accumulation, which increases body temperature and enhances hypotensive susceptibility. Treatments where thermal energy is neither delivered nor removed from the patient through the extracorporeal circulation (so-called extracorporeal thermoneutral treatments) lead to a marked increase in body temperature and to considerable heat accumulation during HD. Since this accumulation of heat cannot be explained by increased heat production, it must be related to reduced heat dissipation through the body surface. Peripheral vasoconstriction, and cutaneous vasoconstriction in particular, compensating for the ultrafiltration-induced decrease in blood volume is considered an important component in this setting. Therefore, to maintain temperature homeostasis, thermal energy has to be cleared from the patient by the extracorporeal system because cutaneous clearance of thermal energy is compromised intradialytically. The focus on dialysate temperature alone does not properly address the problem of controlled extracorporeal heat removal because dialysate temperature is only one of the variables involved in that process. These difficulties can be addressed by changing from the control of dialysate temperature to control of body temperature. Control of body temperature and temperature homeostasis is achievable by the physiologic feedback control system realized in the temperature control mode (T-mode) of the blood temperature monitor (BTM). The delivery of isothermic dialysis, that is, dialysis where body temperature is controlled to remain constant during the treatment, has impressively improved hemodynamic stability in hypotension prone patients.