Trade-offs between vocal accommodation and individual recognisability in common marmoset vocalizations

Recent studies find increasing evidence for vocal accommodation in nonhuman primates, indicating that this form of vocal learning is more prevalent than previously thought. Convergent vocal accommodation (i.e. becoming more similar to partners) indicates social closeness. At the same time, however, becoming too similar may compromise individual recognisability. This is especially problematic if individual recognisability is an important part of the call function, like in long-distance contact calls. In contrast, in calls with a different function, the trade-off between signalling social closeness and individual recognisability might be less severe. We therefore hypothesized that the extent and consequences of accommodation depend on the function of a given call, and expected (1) more accommodation in calls for which individual identity is less crucial and (2) that individual identity is less compromised in calls that serve mainly to transmit identity compared to calls where individual recognisability is less important. We quantified vocal accommodation in three call types over the process of pair formation in common marmoset monkeys (Callithrix jacchus, n = 20). These three call types have different functions and vary with the degree to which they refer to individual identity of the caller. In accordance with our predictions, we found that animals converged most in close contact calls (trill calls), but less in calls where individual identity is more essential (phee- and food calls). In two out of three call types, the amount of accommodation was predicted by the initial vocal distance. Moreover, accommodation led to a drop in statistical individual recognisability in trill calls, but not in phee calls and food calls. Overall, our study shows that patterns of vocal accommodation vary between call types with different functions, suggestive of trade-offs between signalling social closeness and individual recognisability in marmoset vocalizations.

Do marmosets understand others' conversations? A thermography approach

What information animals derive from eavesdropping on interactions between conspecifics, and whether they assign value to it, is difficult to assess because overt behavioral reactions are often lacking. An inside perspective of how observers perceive and process such interactions is thus paramount. Here, we investigate what happens in the mind of marmoset monkeys when they hear playbacks of positive or negative third-party vocal interactions, by combining thermography to assess physiological reactions and behavioral preference measures. The physiological reactions show that playbacks were perceived and processed holistically as interactions rather than as the sum of the separate elements. Subsequently, the animals preferred those individuals who had been simulated to engage in positive, cooperative vocal interactions during the playbacks. By using thermography to disentangle the mechanics of marmoset sociality, we thus find that marmosets eavesdrop on and socially evaluate vocal exchanges and use this information to distinguish between cooperative and noncooperative conspecifics.

Comparison of Exit -Site Infections in Disconnect versus Nondisconnect Systems for Peritoneal Dialysis

Objective

To determine if disconnect systems reduce the incidence of exit-site infections when compared to nondisconnect systems.

Design

We prospectively monitored exit-site infections and peritonitis rates in 96 disconnect patients (Yset, automated peritoneal dialysis (APD)) and 60 nondisconnect patients (spike, ultraviolet connection device (UVXD)).

Setting

A freestanding chronic peritoneal dialysis unit staffed by physicians from both a medical school and a private setting.

Patients

All patients who began peritoneal dialysis at our unit were monitored, regardless of cause of endstage renal disease (ESRD) or age.

Intervention

Patients were dialyzed using the system (Y-set, spike, etc.) most appropriate for their life-style and their ability to administer self-care.

Main Outcome

We attempted to follow disconnect and nondisconnect patients for a similar median time on dialysis and compared differences in exit-site infections.

Results

Peritonitis rates (episodes/pt year) were reduced for disconnect (0.60) versus nondisconnect (0.99) systems (p=0.0006). Despite the marked reduction in peritonitis rates, there was no difference in exit-site infection rates (0.35 vs 0.38), the time to the first exit -site infection, or the time to the first catheter removal for disconnect versus nondisconnect groups. When individual systems were compared, differences in exit-site infection rates (episodes/pt years) were noted (0.62, spike; 0.26,UVXD; 0.32,Y-set; 0.41,APD).

Conclusion

We found no overall difference in exit site infection rates for disconnect versus nondisconnect systems, despite a reduction in peritonitis rates for disconnect systems.

Ysis Prescription and Peritoneal Membrane Transport Characteristics on Nutritional Status

These data suggest that dialysis dose is one of the major determinants of protein and energy intake in PD patients and that higher doses of dialysis tend to improve outcome. The data also suggest that with a long time on PD the peritoneal membrane probably has some underlying histological changes that preclude it from optimally responding to injury and may predispose it to irreversible damage. A possible early finding in this case is an increase in peritoneal transport in patients whose transport was initially stable. Peritoneal membrane transport properties are an important determinant of not only dialysis dose, but also nutritional status via both direct and indirect means. It is therefore important to identify the individual patient's peritoneal membrane transport characteristics. These transport characteristics may change over time. High transporters on CAPD represent a unique challenge. They have ultrafiltration problems and a tendency toward protein malnutrition presumably due to increased dialysate protein losses while on CAPD. One must consider that malnutrition in a rapid transporter may be due to the fact that the patient is on the wrong PD therapy. A change to NIPD may rectify some of the biochemical parameters, but these patients may not always improve. Reasons for this occasional lack of improvement are multifactorial, but emphasize our need to look at each patient as an individual and not focus only on laboratory parameters.

Changes in Peritoneal Transport during the First Month of Peritoneal Dialysis

Objective

To determine if peritoneal transport characteristics change during the initial month of peritoneal dialysis.

Design

Retrospective review of peritoneal equilibration test (PET) results in patients who received their first PET during the first two weeks of peritoneal dialysis (early PET group) versus patients who received their first PET between four and 28 weeks after the initiation of dialysis (late PET group). The initial PET values were compared to subsequent PET results obtained approximately seven months after the initial PET.

Setting

Peritoneal dialysis unit of a tertiary medical center.

Outcome Measures

PET results and calculated mass transfer area coefficient (MT AC) values.

Patients

Thirty-four peritoneal dialysis patients in the early PET group and 17 peritoneal dialysis patients in the late PET group.

Results

In the early PET group, there was a statistically significant increase from the initial to follow-up values for both dialysate-to-plasma (DIP) creatinine and MTAC creatinine (p < 0.01) as well as a significant decrease for four-hour dialysate to initial dialysate ratios (DID) glucose (p = 0.08) and MTAC glucose (p < 0.05). In the late PET group, there was no significant change in any of these parameters with time. However, in the late PET group, there was a significant decrease in DIP urea values with time (p < 0.01), but not with MTAC urea. In addition, there were no differences over time in either group for serum albumin or hematocrit values.

Conclusion

During the first two weeks of peritoneal dialysis, there tends to be a change in peritoneal transport characteristics in some patients. PET data obtained during this time period should be interpreted as preliminary.

An Elevated Ratio of Measured to Predicted Creatinine Production in Capd Patients is Not a Sensitive Predictor of Noncompliance with the Dialysis Prescription

Objective

To determine the effect a period of “intentional noncompliance” in stable continuous ambulatory peritoneal dialysis (CAPD) patients has on the ratio of measured to predicted creatinine generation.

Design

Prospective study that compares baseline to noncompliant periods in individual CAPD patients.

Patients

Nine chronic, stable CAPD patients.

Study Design

At baseline, measured creatinine production and adequacy parameters (KT/V, creatinine clearance, lean body mass, and protein equivalent of nitrogen appearance) were calculated from 24-hour collections of dialysate and urine while patients were performing their routine dialysis prescriptions. After three days of intentional noncompliance (one less exchange/day) the patients repeated their 24-hour collections, again performing their routine number of exchanges. Measured creatinine production and adequacy parameters were again calculated. Predicted creatinine production for each patient was calculated from standard equations. All parameters at baseline were compared to corresponding parameters after intentional noncompliance.

Results

In all patients, except one where there was no change, there was a statistically significant increase in not only the ratio of measured to predicted creatinine production but also all other parameters.

Conclusion

As suspected by previous investigators, this study suggests that one cause of an elevated ratio of measured to predicted creatinine production may be a recent period of noncompliance with the patient's dialysis prescription. However, these data suggest that an isolated ratio of measured to predicted creatinine generation is not a sensitive predictor of noncompliance with the peritoneal dialysis prescription.

Recommended Clinical Practices for Maximizing Peritoneal Dialysis Clearances

Data from the Canada-U.S.A. (CANUSA) Study have recently confirmed a long-suspected linkage between total clearance and patient survival in peritoneal dialysis (PD). Recognizing that what we have historically accepted as adequate PD simply is not, the Ad Hoc Committee on Peritoneal Dialysis Adequacy met in January, 1996. This committee of invited experts was convened by Baxter Healthcare Corporation to prepare a consensus statement that provides clinical recommendations for achieving clearance guidelines for peritoneal dialysis. Through an analysis of 806 PD patients, the group concluded that adequate clearance delivered with PD can be achieved in almost all patients if the prescription is individualized according to the patient's body surface area, amount of residual renal function, and peritoneal membrane transport characteristics. Use of 2.5 L to 3.0 L fill volumes, the addition of an extra exchange, and giving automated peritoneal dialysis patients a “wet” day are all options to consider when increasing weekly creatinine clearance and KTN. Rather than specify a single clearance or KTN target, the recommended clinical practice is to provide the most dialysis that can be delivered to the individual patient, within the constraints of social and clinical circumstances, quality of life, life-style, and cost. The challenge to PD practitioners is to make prescription management an integral part of everyday patient management. This includes assessment of peritoneal membrane permeability, measurement of dialysis and residual renal clearance, and adjustment of the dialysis prescription when indicated.

Solute Clearance Approach to Adequacy of Peritoneal Dialysis

To investigate the effect of dialysis prescription on patient outcome for peritoneal dialysis patients, the relationship between total solute clearance and the relative risk of death has been investigated. Preliminary studies have suggested that more clearance is better and that patient outcome is predicted by total solute clearance. The recently published Canada-U.S.A. (CANUSA) multicenter study, evaluating adequacy of dialysis and nutrition in peritoneal dialysis patients, has further defined this relationship. Although these publications allow us to establish guidelines for the treatment of peritoneal dialysis patients, they also define the limitations of our knowledge and raise new questions.

In this article we review our current knowledge regarding the predicted value of total solute clearance with patient outcome and nutritional status. Furthermore, we attempt to outline a practical approach for optimizing total solute clearance in peritoneal dialysis patients.

Based on a review of the published literature and clinical recommendations, we feel that the minimal target total solute clearance for continuous forms of peritoneal dialysis is a weekly total KTN > 2.0 and/or a weekly total creatinine clearance >60 L/week/1.73 m2. For intermittent therapies, a weekly total KTN > 2.2 and/or a weekly total creatinine clearance >70 L/week/1.73 m2 is recommended.

Frequency and Causes of Discrepancy between Kt/V and Creatinine Clearance

Objective

This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy.

Design

Nonrandomized, retrospective data analysis.

Setting

Single PD unit of a university teaching hospital.

Patients

All adult patients receiving PD at our center from January 1995 to December 1996.

Methods

Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height.

Results

Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V ≥ 2.0/wk and Ccr ≥ 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used.

Conclusions

Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.

Comparison of Peritonitis Rates during Long Term Use of Standard Spike versus Ultraset in Continuous Ambulatory Peritoneal Dialysis (CAPD)

Continuous ambulatory peritoneal dialysis (CAPD) is an increasingly popular means of end-stage renal disease replacement therapy. Unfortunately, peritonitis continues to be a major source of both morbidity and mortality. The Ultraset incorporates a “flush-before-fill” concept which should theoretically decrease peritonitis rates when compared to the standard spike procedure, while allowing patients the convenience of disconnect. To investigate the impact of long-term use of the Ultraset on peritonitis rates, we conducted the following study.

We prospectively compared 21 new CAPD patients using the standard spike to 20 new CAPD patients using the Ultraset. Peritonitis episodes, episodes of exit -site infection, and the association of peritonitis with exit-site infection were monitored. Peritonitis rates were 7.57 months/episode for the group using the standard spike vs. 27.79 months/episode in the group using the Ultraset. Exit-site infection rates were 22.21 months/infection with the standard spike vs. 37.05 months/infection with the Ultraset. Using Kaplan-Meier plots, there was a statistically significant difference in the estimated time to the first episode of peritonitis, but there was no statistically significant difference regarding the risk of exit-site infections.

Combined Peritoneal Dialysis and Hemodialysis: Our Experience Compared to Others

Objective

To determine the clinical experience of using combined-modality [simultaneous hemodialysis (HD) and peritoneal dialysis (PD)] treatment in patients with end-stage renal disease.

Design

We reviewed data on 4 patients from our center that were treated with “combined-mode therapy.” We then conducted a retrospective survey by sending questionnaires to nephrologists in the US and Canada by mail and by posting the survey on the Internet. Data queried included number of patients on combined modality, solute clearances, albumin levels pre and post combined therapy, reasons for using combined therapy, duration and success of combined therapy, and reimbursement issues.

Setting and Participants

Ours is a tertiary-care center. Patients that were not doing well on PD alone were put on combined modality of treatment between 1992 and 1998.

Main Outcome Measures

Clinical improvement in the indication for which the participant was started on combined modality.

Results

In response to the survey, data on 27 patients were collected. These data were combined with data on 4 patients from our unit that had previously been treated with combined HD and PD. Most patients were reported to have more than one clinical reason for changing from PD to combined therapy. The main clinical reason for offering combined treatments was inadequate solute clearance (34%), followed by ultrafiltration problems (16%) and neuropathy (11%). Mean duration of time followed on combined treatment was 8.5 ± 0.12 months. Most patients tolerated combined treatment well and were reported to show improvement in the clinical reasons for which they needed the combined modality. Dual access and reimbursement issues were not a problem. There was no single method used for calculating total (HD, PD, and residual renal) solute clearance. No universal total solute clearance goal was reported.

Conclusion

Hemodialysis and PD are not mutually exclusive. They can be used in combination to achieve targeted solute clearances, to improve certain clinical conditions, and to control volume and blood pressure in a subset of patients. Further evaluation is needed to better establish the long-term outcomes of using combined modality. Total solute clearance goals and methods for determining total solute clearance need to be standardized.

Replacement of Amino Acid and Protein Losses with 1.1% Amino Acid Peritoneal Dialysis Solution

Objective

Losses of nutrients into dialysate may contribute to malnutrition. Peritoneal dialysis (PD) patients are reported to lose 3 -4 g/day of amino acids (AAs) and 4 -15 g/day of proteins. The extent to which one exchange with a 1.1% AA dialysis solution (Nutrineal, Baxter, Deerfield, IL, U.s.A.) offsets these losses was investigated in a 3-day inpatient study in 20 PD patients.

Design

Simple, open-label, cross-over study on consecutive days in a clinical research unit. On day 1 all patients were given a peritoneal equilibration test (PET). On day 2 they received 1.5% dextrose Dianeal (Baxter) as the first exchange of the day and their usual regimen thereafter. On day 3, the first exchange of the day was the 1.1% AA solution in place of 1.5% Dianeal and the usual PD regimen thereafter. On days 2 and 3 all dialysate effluent was collected and analyzed for AAs and proteins. Patients were maintained on a constant diet.

Results

Losses of AAs and total proteins on day 2 were 3.4 ± 0.9 g and 5.8 ± 2.4 g, respectively, totaling 9.2 ± 2.7 g. The net uptake of AAs on day 3 was 17.6 ± 2.6 g (80 ± 12% of the 22 g infused). Mean gains of AAs on day 3 exceeded losses of proteins and AAs on day 2, p < 0.001. Losses of total proteins, but not losses of AAs, and the net absorption of AAs from the dialysis solution were correlated directly with peritoneal membrane transport characteristics, obtained from the PET.

Conclusion

Daily losses of AAs and proteins into dialysate are more than offset by gains of AAs absorbed from one exchange with 1.1% AA-based dialysis solution. Net gains of AAs exceeded losses of proteins and AAs in all patients studied. The difference was relatively constant across a wide range of membrane transport types. Net AA gains were approximately two times the total AA and protein losses.

Assessment of Dialysis Dose by Measured Clearance versus Extrapolated Data

Objective

To determine whether estimates of daily dialysis clearance of creatinine and urea, based on data from the 4-hour peritoneal equilibration test, correlate well with daily dialysis clearance measured by 24-hour dialysate collection in chronic ambulatory peritoneal dialysis patients.

Design

Prospective study in which each subject collected all dialysate from a 24-hour period and then immediately thereafter underwent a standard peritoneal equilibration test (PET). Daily clearances of creatinine and urea were calculated from 24-hour dialysate collections by standard methods and then were compared with several estimates of 24-hour clearance based on PET data.

Setting

Single peritoneal dialysis unit of a university teaching hospital.

Patients

Thirty-six stable patients on continuous ambulatory peritoneal dialysis (CAPD).

Main Outcome

The estimated values for daily dialysis clearance both overestimated and underestimated the measured 24-hour clearance. The correlation coefficient between the extrapolations and the actual 24-hour clearances ranged from 0.63–0.68. The range of discordance for daily creatinine clearance was from -2530 mL/dayto +2199 mL/day. For daily urea clearance, the range of discordance was from -21 03 mL/ day to +1940 mL/day. The peritoneal membrane transport characteristics of the individual patient did not predict whether the extrapolation overestimated orunder estimated the measured daily clearance.

Conclusion

Extrapolation of PET data is not a reliable method to estimate the dose of dialysis delivered to the patient. A 24-hour collection of dialysis is necessary for this determination.

Measurement of Continuous Ambulatory Peritoneal Dialysis Prescription Adherence Using a Novel Approach

Objective

The purpose of the study was to test a novel approach to monitoring the adherence of continuous ambulatory peritoneal dialysis (CAPD) patients to their dialysis prescription.

Design

A descriptive observational study was done in which exchange behaviors were monitored over a 2-week period of time.

Setting

Patients were recruited from an outpatient dialysis center.

Participants

A convenience sample of patients undergoing CAPD at Piedmont Dialysis Center in Winston–Salem, North Carolina was recruited for the study. Of 31 CAPD patients, 20 (64.5%) agreed to participate.

Measures

Adherence of CAPD patients to their dialysis prescription was monitored using daily logs and an electronic monitoring device (the Medication Event Monitoring System, or MEMS; APREX, Menlo Park, California, U.S.A.). Patients recorded in their logs their exchange activities during the 2-week observation period. Concurrently, patients were instructed to deposit the pull tab from their dialysate bag into a MEMS bottle immediately after performing each exchange. The MEMS bottle was closed with a cap containing a computer chip that recorded the date and time each time the bottle was opened.

Results

One individual's MEMS device malfunctioned and thus the data presented in this report are based upon the remaining 19 patients. A significant discrepancy was found between log data and MEMS data, with MEMS data indicating a greater number and percentage of missed exchanges. MEMS data indicated that some patients concentrated their exchange activities during the day, with shortened dwell times between exchanges. Three indices were developed for this study: a measure of the average time spent in noncompliance, and indices of consistency in the timing of exchanges within and between days. Patients who were defined as consistent had lower scores on the noncompliance index compared to patients defined as inconsistent ( p = 0.015).

Conclusions

This study describes a methodology that may be useful in assessing adherence to the peritoneal dialysis regimen. Of particular significance is the ability to assess the timing of exchanges over the course of a day. Clinical implications are limited due to issues of data reliability and validity, the short-term nature of the study, the small sample, and the fact that clinical outcomes were not considered in this methodology study. Additional research is needed to further develop this data-collection approach.

Peritoneal Dialysis

These presentations highlighted some of the current research needs in peritoneal dialysis. They are not meant to eclipse other important issues, such as adequacy and nutrition. These needs have become apparent as the therapy has evolved and progressed. They in fact are a testament to the increasing acceptance, use, and development of the therapy and suggest that there is potential for even further advancement for the therapy of peritoneal dialysis in the future.

Incremental Initiation of Dialysis: One Center's Experience over a Two-Year Period

Objective

This pilot study describes our center's experience with peritoneal dialysis (PD) over the past 2 years using a “healthy start” dialysis protocol with an incremental approach to prescription management.

Design

Nonrandomized, prospective pilot study.

Setting

Single PD unit of a university teaching hospital.

Patients

Thirteen PD patients who initiated dialysis at our center from April 1997 to June 1999.

Methods

Patients initiating PD with residual renal Kt/V of 1.0 – 2.0/week were invited to participate. They were given an initial dialysis prescription so that total (residual renal + dialysis) weekly Kt/V exceeded 2.0. The dialysis prescription was “incrementally” increased as residual renal function (RRF) declined. Data collected for all patients included monthly serum chemistries, residual renal weekly Kt/V and creatinine clearance (CCr) at 1- to 2-month intervals, and peritoneal weekly Kt/V and CCr at 3-month intervals and 1 month after each prescription change.

Results

To date, we have followed 13 patients on our incremental PD protocol for a total of 159.3 patient-months. Mean serum albumin concentration and mean normalized protein equivalent of nitrogen appearance (nPNA) were stable throughout the study. Mean total Kt/V and CCr remained above the recommended targets of 2.0/wk and 60 L/wk, respectively. Residual renal function declined rather slowly in our PD patients. One patient died from complications of aortic valve surgery and a second died from pneumonia. A third patient died from peritonitis. One patient required a new Tenckhoff catheter after catheter migration. Three patients were temporarily switched to hemodialysis after a hernia repair, a pleural leak, and elective native/transplant nephrectomies, respectively. Two patients were permanently switched to hemodialysis: one after an episode of peritonitis, the second after accidentally damaging his PD catheter.

Conclusions

Providing incremental dialysis to maintain adequate total small solute clearance has been technically feasible in our patient population. However, a larger than expected number of complications was seen in our study. Fortunately, complications were easier to manage due to the presence of RRF. Because this study was not designed to compare outcome with that observed after traditional initiation of dialysis, further large-scale studies are needed.

Peritoneal Dialysis Case Forum

The Trials and Tribulations of an Adolescent Patient with End-Stage Renal Disease

Significance, Epidemiology, and Prevention of Peritoneal Dialysis Catheter Infections

Catheter infections are a major cause of morbidity, catheter loss, and transfer to hemodialysis. These infections are mainly due to S. aureus. To date, treatment is less than optimal. Therefore, the primary goal should be prevention of catheter infections. Prevention is based on improving catheter design and implantation technique while using careful exit-site care. Prophylaxis with antimicrobials such as intranasal mupirocin or the use of silverimpregnated catheters appears promising as a way to reduce the risk of developing S. aureus infections. To optimize patient outcome, one must focus on these preventive measures.

24-Hour Dialysate Collection for Determination of Peritoneal Membrane Transport Characteristics: Longitudinal Follow-Up Data for the Dialysis Adequacy and Transport Test (Datt)

Objective

To determine the ability of the dialysis adequacy and transport test (DATT) to monitor changes in peritoneal transport characteristics over time.

Setting

University-based peritoneal dialysis program.

Patients

One hundred patients on continuous ambulatory peritoneal dialysis who underwent 226 simultaneous DATTs and peritoneal equilibration tests (PET).

Methods

Retrospective analysis of DA TT and PET data.

Results

The mean 24-hour dialysate-to-plasma creatinine (cr) concentration ratio (DIP cr) from the DATT was 0.70±0.10, and the mean four-hour DIP crfrorn the PET was 0.68 ± 0.10. The correlation coefficient between the fourhour and 24-hour DIP cr was 0.81, and the standard error of estimate was 0.065. The mean (±SD) difference between the four-hour and 24-hour DIP cr was 0.023 ± 0.061. Fifty eight patients had two or more sequential DA TTs and PETs. For these 94sets of sequential DATTs and PETs, the mean (±SD) difference between the change in the four-hour DIP cr and the change in the 24-hour DIP cr was 0.020 ± 0.024, and the standard error of estimate was 0.064. In 17 patients a change in dwell volume from 2.0 L to 2.5 L occurred between the first and second measures of peritoneal membrane transport characteristics. The mean (±SD) difference between the change in the four-hour DIP cr and the change in the 24-hour DIP cr was 0.036 ± 0.055, and the standard error of estimate was 0.087.

Conclusion

The DATT can be used to monitor for changes in peritoneal transport over time. It should not be used in patients receiving cycler therapy or in patients whose dwell times and dextrose concentrations vary markedly from day to day.

Comparison of a 2.5% and a 4.25% Dextrose Peritoneal Equilibration Test

Background

Ultrafiltration (UF) failure develops over time in some patients on peritoneal dialysis. The workup of UF failure can be difficult and the 4.25% peritoneal equilibration test (PET) has been suggested to be more useful than the 2.5% PET for the workup of UF failure. It is unknown how a 4.25% PET compares to a 2.5% PET in individual patients.

Objectives

To assess the differences in drain volumes and sodium sieving using a 4.25% PET compared to a 2.5% PET, and to determine whether peritoneal transport rates, in terms of dialysate-to-plasma (D/P) ratios, are comparable between the two.

Design

Pilot study with each patient serving as his or her own control.

Setting

Outpatient dialysis facility of Wake Forest University Baptist Medical Center.

Patients

47 patients, all of whom had a 2.5% PET and a 4.25% PET performed within 1 week of each other.

Outcome Measures

Dialysate-to-plasma ratios of urea and creatinine, dialysate total protein, and dialysate glucose compared to time zero (D/D0) at 0, 2, and 4 hours. Four-hour drain volumes and sodium sieving at 2 hours were also measured.

Results

There was reproducibility between the 2.5% and 4.25% PET for D/P ratios of urea and creatinine and for dialysate total protein. There were expected differences in drain volume, sodium sieving, and D/D0 glucose between the two methods.

Conclusions

The use of a 4.25% PET may be more useful for the workup of UF failure because of the accentuation of drain volume and sodium sieving, while remaining useful for prescription management.

The use of infrared thermography to investigate emotions in common marmosets

Measuring body surface temperature changes with infrared thermography has recently been put forward as a non-invasive alternative measure of physiological correlates of emotional reactions. In particular, the nasal region seems to be highly sensitive to emotional reactions. Several studies suggest that nasal temperature is negatively correlated with the level of arousal in humans and other primates, but some studies provide inconsistent results. Our goal was to establish the use of infrared thermography to quantify emotional reactions in common marmosets (Callithrix jacchus), with a focus on the nasal region. To do so we exposed 17 common marmosets to a set of positive, negative and control stimuli (positive: preferred food, playback of food calls; negative: playback of aggressive vocalizations, teasing; control: no stimulus). We compared nasal temperature before and after the stimuli and expected that highly aroused emotional states would lead to a drop in nasal temperature. To validate the thermography measure, we coded piloerection of the tail as an independent measure of arousal and expected a negative correlation between the two measures. Finally, we coded physical activity to exclude its potential confounding impact on nasal temperature. Our results show that all predictions were met: the animals showed a strong decrease in nasal temperature after the presentation of negative arousing stimuli (teasing, playback of aggressive vocalizations). Furthermore, these changes in nasal temperature were correlated with piloerection of the tail and could not be explained by changes in physical activity. In the positive and the control conditions, we found systematic sex differences: in males, the preferred food, the playbacks of food calls, as well as the control stimulus led to an increase in nasal temperature, whereas in females the temperature remained stable (preferred food, control) or decreased (playback of food calls). Based on naturalistic observations that document higher food motivation and competition among female marmosets, as well as stronger reactions to separation from group members in male marmosets, these sex differences corroborate a negative correlation between arousal and nasal temperature. Overall, our results support that measuring nasal temperature by infrared thermography is a promising method to quantify emotional arousal in common marmosets in a fully non-invasive and highly objective way.

Burden and Correlates of Hospital Readmissions among U.S. Peritoneal Dialysis Patients

Background:Hospital readmissions are common among in-center hemodialysis patients, but little is known about readmissions among peritoneal dialysis (PD) patients. Using national administrative data, we aimed to examine the burden and correlates of hospital readmissions among U.S. PD patients.Methods:Among 10,505 adult U.S. PD patients with an index admission (first admission after 120 days on dialysis) between 31 January 2011 and 30 November 2014, readmissions were defined as new hospital admissions within 30 days of index discharge. Multivariable logistic regression was used to obtain adjusted odds ratios (ORs) for readmission.Results:Overall, 26.8% of index admissions were followed by a readmission. Readmitted patients were more likely to have congestive heart failure (31.0% vs 25.4%; p < 0.001) and peripheral arterial disease (11.6% vs 8.6%; p < 0.001) and had longer index admission length of stay (median = 4 vs 3 days; p < 0.001) than those who were not; age, sex, and race did not differ by readmission status. After adjustment for patient and index admission characteristics, longer length of stay (≥ 4 vs < 4 days, OR = 1.48, 95% confidence interval [CI] 1.35 - 1.62), peripheral arterial disease (OR = 1.31, 95% CI 1.16 - 1.57), congestive heart failure (OR = 1.25, 95% CI 1.13 - 1.39), and ischemic heart disease (OR = 1.12, 95% CI 1.01 - 1.24) were associated with higher likelihood of readmission; index admission due to peritonitis vs other causes was associated with lower likelihood of readmission (OR = 0.80, 95% CI 0.70 - 0.92).Conclusions:Our results suggest that, particularly in the absence of a PD-related cause of hospitalization such as peritonitis, PD patients may be at high risk for readmission and may benefit from closer post-discharge monitoring.

Post-hospitalization dialysis facility processes of care and hospital readmissions among hemodialysis patients: a retrospective cohort study

Background

Both dialysis facilities and hospitals are accountable for 30-day hospital readmissions among U.S. hemodialysis patients. We examined the association of post-hospitalization processes of care at hemodialysis facilities with pulmonary edema-related and other readmissions.

Methods

In a retrospective cohort comprised of electronic medical record (EMR) data linked with national registry data, we identified unique patient index admissions (n = 1056; 2/1/10–7/31/15) that were followed by ≥3 in-center hemodialysis sessions within 10 days, among patients treated at 19 Southeastern dialysis facilities. Indicators of processes of care were defined as present vs. absent in the dialysis facility EMR. Readmissions were defined as admissions within 30 days of the index discharge; pulmonary edema-related vs. other readmissions defined by discharge codes for pulmonary edema, fluid overload, and/or congestive heart failure. Multinomial logistic regression to estimate odds ratios (ORs) for pulmonary edema-related and other vs. no readmissions.

Results

Overall, 17.7% of patients were readmitted, and 8.0% had pulmonary edema-related readmissions (44.9% of all readmissions). Documentation of the index admission (OR = 2.03, 95% CI 1.07–3.85), congestive heart failure (OR = 1.87, 95% CI 1.07–3.27), and home medications stopped (OR = 1.81, 95% CI 1.08–3.05) or changed (OR = 1.69, 95% CI 1.06–2.70) in the EMR post-hospitalization were all associated with higher risk of pulmonary edema-related vs. no readmission; lower post-dialysis weight (by ≥0.5 kg) after vs. before hospitalization was associated with 40% lower risk (OR = 0.60, 95% CI 0.37–0.96).

Conclusions

Our results suggest that some interventions performed at the dialysis facility in the post-hospitalization period may be associated with reduced readmission risk, while others may provide a potential existing means of identifying patients at higher risk for readmissions, to whom such interventions could be efficiently targeted.

Electronic supplementary material

The online version of this article (10.1186/s12882-018-0983-5) contains supplementary material, which is available to authorized users.

Reverse audience effects on helping in cooperatively breeding marmoset monkeys

Cooperatively breeding common marmosets show substantial variation in the amount of help they provide. Pay-to-stay and social prestige models of helping attribute this variation to audience effects, i.e. that individuals help more if group members can witness their interactions with immatures, whereas models of kin selection, group augmentation or those stressing the need to gain parenting experience do not predict any audience effects. We quantified the readiness of adult marmosets to share food in the presence or absence of other group members. Contrary to both predictions, we found a reverse audience effect on food-sharing behaviour: marmosets would systematically share more food with immatures when no audience was present. Thus, helping in common marmosets, at least in related family groups, does not support the pay-to-stay or the social prestige model, and helpers do not take advantage of the opportunity to engage in reputation management. Rather, the results appear to reflect a genuine concern for the immatures' well-being, which seems particularly strong when solely responsible for the immatures.

Vascular Access Placement Order and Outcomes in Hemodialysis Patients: A Longitudinal Study

BACKGROUND

Arteriovenous accesses (AVA) in patients performing hemodialysis (HD) are labeled "permanent" for AV fistulas (AVF) or grafts (AVG) and "temporary" for tunneled central venous catheters (TCVC). Durability and outcomes of permanent vascular accesses based on the sequence in which they were placed or used receives little attention. This study analyzed longitudinal transitions between TCVC-based and AVA-based HD outcomes according to the order of placement.

METHODS

All 391 patients initiating chronic HD via a TCVC between 2012 and 2013 at 12 outpatient academic dialysis units were included in this study. Chronological distributions of HD vascular accesses were recorded over a mean (SD) of 2.8 (0.9) years and sequentially grouped into periods for TCVC-delivered and AVA-delivered (AVF or AVG) HD. Primary AVA failure and cumulative access survival were evaluated based on access placement sequence and type, adjusting for age.

RESULTS

In total, 92.3% (361/391) of patients underwent 497 AVA placement surgeries. Analyzing the initial 3 surgeries, primary AVF failure rates increased with each successive fistula placement (p = 0.008). Among the 82.9% (324/391) of TCVC patients successfully converted to an AVA, 30.9% returned to a TCVC, followed by a 58.0% conversion rate to another AVA. Annual per-patient vascular access transition rates were 2.02 (0.09) HD periods using a TCVC and 0.54 (0.03) HD periods using an AVA. Comparing the first AVA used with the second, cumulative access survivals were 701.0 (370.0) vs. 426.5 (275.0) days, respectively. Excluding those never converting to an AVF or AVG, 169 (52.2%) subsequently converted from a TCVC to a permanent access and received HD via AVA for ≥80% of treatments.

CONCLUSIONS

HD vascular access outcomes differ based on the sequence of placement. In spite of frequent AVA placements, only half of patients effectively achieved a "permanent" vascular access and used an AVA for the majority of HD treatments.

Effects of weight-based ultrafiltration rate limits on intradialytic hypotension in hemodialysis

INTRODUCTION

High ultrafiltration (UF) rates can result in intradialytic hypotension and are associated with increased mortality. The effects of a weight-based UF rate limit on intradialytic hypotension and the potential for unwanted fluid weight gain and hospitalizations for volume overload are unknown.

METHODS

This retrospective cohort study examined 123 in-center hemodialysis patients at one facility who transitioned to 13 mL/kg/h maximum UF rates. Patients were studied for an 8 week UF rate limit exposure period and compared to the 8-week period immediately prior, during which the cohort served as its own historical control. The primary outcomes were frequency of intradialytic hypotension events and percentage of treatments with a hypotension event.

FINDINGS

The delivered UF rate was lower during the exposure compared to the baseline period (mean UF rate 7.90 ± 4.45 mL/kg/h vs. 8.92 ± 5.64 mL/kg/h; P = 0.0005). The risk of intradialytic hypotension was decreased during the exposure compared to baseline period (event rate per treatment 0.0569 vs. 0.0719, OR 0.78 [95% CI 0.62-1.00]; P = 0.0474), as was the risk of having a treatment with a hypotension event (percentage of treatments with event 5.2% vs. 6.8%, OR 0.75 [95% CI 0.58-0.96]; P = 0.0217). Subgroup analyses demonstrated that these findings were attributable to patients with high baseline UF rates. Statistically significant differences in all-cause or volume overload-related hospitalization were not observed during the exposure period.

DISCUSSION

A weight-based UF rate limit of 13 mL/kg/h was associated with a decrease in the rate of intradialytic hypotension events among in-center hemodialysis patients.

Intensive Hemodialysis and Potential Risks With Increasing Treatment

Although intensive hemodialysis (HD) can address important clinical problems, increasing treatment also introduces risks. In this review, we assess risks pertaining to 6 domains: vascular access complications, infection, mortality, loss of residual kidney function, solute balance, and patient and care partner burden. In the Frequent Hemodialysis Network (FHN) trials, short daily and nocturnal schedules increased the incidence of access complications, although the incidence of access loss was not statistically higher. Observational studies indicate that infection-related hospitalization is an ongoing challenge with short daily HD. Excess risk may be catalyzed by poor infection control practices in the home setting in which intensive HD is typically delivered, but with fixed probability of bacterial contamination per cannulation, greater treatment frequency necessarily increases the risk for infectious complications. Buttonhole cannulation may increase the risk for metastatic infections. However, intensive HD in the home setting is associated with lower risk for infection than peritoneal dialysis. Data regarding mortality are equivocal. With extended follow-up of individuals in the FHN trials, short daily HD was associated with lower risk relative to the usual schedule, whereas nocturnal HD was associated with higher risk. In many, but not all, observational studies, short daily HD has been associated with lower risk than both in-center HD and peritoneal dialysis; however, observational studies are subject to unmeasured confounding. Intensive HD can accelerate the loss of residual kidney function in new dialysis patients with substantial urine output and can deplete solutes (eg, phosphorus) to the extent that supplementation is necessary. Finally, intensive HD may increase burden on patients and caregivers, possibly leading to technique failure. Some of these problems might be addressed with careful monitoring, so that relevant interventions (eg, antibiotics, retraining, and respite care) can be delivered. Ultimately, intensive HD is not a panacea for end-stage renal disease. Potential benefits and risks of treatment should be jointly considered.

Early hospital readmission among hemodialysis patients in the United States is associated with subsequent mortality

Dialysis providers in the United States may soon be held accountable for their patients' 30-day hospital readmissions. However, few studies have evaluated the timing of readmissions, which determines the window in which dialysis providers could act to prevent readmission. We therefore examined the timing of readmissions of hemodialysis patients in the United States and its association with mortality among 285,795 prevalent adult Medicare-primary hemodialysis patients from a national registry. Patients had at least one hospitalization in 2010-2013 (first index) and survived for 30 days or more. Readmission timing was defined as 0-7, 8-14, or 15-30 days after the index discharge. Multivariable Cox proportional hazards models were used to estimate the association between readmission timing (referent no readmission) and mortality, censored at one year. Overall, 23.1% of patients had readmissions within 30 days of the index discharge, of which over one-third (35.9%) were within the first week. Regardless of timing, patients with readmissions had a higher risk of death within one year, compared to those with no readmissions, with hazard ratios of 2.04 (95% confidence interval 2.00-2.09) for being readmitted within 15-30 days; 1.98 (1.93-2.04) for being readmitted within 8-14 days; and 1.76 (1.71-1.80) for being readmitted within 0-7 days. Thus, opportunities for dialysis providers to intervene and prevent early readmission may be limited. Regardless of the timing, readmission appears independently associated with a substantially increased risk of mortality in this population.

APOL1 renal-risk genotypes associate with longer hemodialysis survival in prevalent nondiabetic African American patients with end-stage renal disease

Relative to European Americans, evidence supports that African Americans with end-stage renal disease (ESRD) survive longer on dialysis. Renal-risk variants in the apolipoprotein L1 gene (APOL1), associated with nondiabetic nephropathy and less subclinical atherosclerosis, may contribute to dialysis outcomes. Here, APOL1 renal-risk variants were assessed for association with dialytic survival in 450 diabetic and 275 nondiabetic African American hemodialysis patients from Wake Forest and Emory School of Medicine outpatient facilities. Outcomes were provided by the ESRD Network 6-Southeastern Kidney Council Standardized Information Management System. Dates of death, receipt of a kidney transplant, and loss to follow-up were recorded. Outcomes were censored at the date of transplantation or through 1 July 2015. Multivariable Cox proportional hazards models were computed separately in patients with nondiabetic and diabetic ESRD, adjusting for the covariates age, gender, comorbidities, ancestry, and presence of an arteriovenous fistula or graft at dialysis initiation. In nondiabetic ESRD, patients with 2 (vs. 0/1) APOL1 renal-risk variants had significantly longer dialysis survival (hazard ratio 0.57), a pattern not observed in patients with diabetes-associated ESRD (hazard ratio 1.29). Thus, 2 APOL1 renal-risk variants are associated with longer dialysis survival in African Americans without diabetes, potentially relating to presence of renal-limited disease or less atherosclerosis.

Survey of home hemodialysis patients and nursing staff regarding vascular access use and care

Vascular access infections are of concern to hemodialysis patients and nurses. Best demonstrated practices (BDPs) have not been developed for home hemodialysis (HHD) access use, but there have been generally accepted practices (GAPs) endorsed by dialysis professionals. We developed a survey to gather information about training provided and actual practices of HHD patients using the NxStage System One HHD machine. We used GAP to assess training used by nurses to teach HHD access care and then assess actual practice (adherence) by HHD patients. We also assessed training and adherence where GAPs do not exist. We received a 43% response rate from patients and 76% response from nurses representing 19 randomly selected HHD training centers. We found that nurses were not uniformly instructing HHD patients according to GAP, patients were not performing access cannulation according to GAP, nor were they adherent to their training procedures. Identification of signs and symptoms of infection was commonly trained appropriately, but we observed a reluctance to report some signs and symptoms of infection by patients. Of particular concern, when aggregating all steps surveyed, not a single nurse or patient reported training or performing all steps in accordance with GAP. We also identified practices for which there are no GAPs that require further study and may or may not impact outcomes such as infection. Further research is needed to develop strategies to implement and expand GAP, measure outcomes, and ultimately develop BDP for HHD to improve infectious complications.

Risk of catheter-related bloodstream infection in elderly patients on hemodialysis

BACKGROUND AND OBJECTIVES

Elderly patients require tunneled central vein dialysis catheters more often than younger patients. Little is known about the risk of catheter-related bloodstream infection in this population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study identified 464 patients on hemodialysis with tunneled central vein dialysis catheters between 2005 and 2007 and excluded patients who accrued <21 catheter-days during this period. Outpatient and inpatient catheter-related bloodstream infection data were collected. A Cox proportional hazards regression analysis adjusting for sex, ancestry, comorbidites, dialysis vintage, dialysis unit, immunosuppression, initial catheter site, and first antimicrobial catheter lock solution was performed for risk of catheter-related bloodstream infection between nonelderly (18-74 years) and elderly (≥ 75 years) patients.

RESULTS

In total, 374 nonelderly and 90 elderly patients with mean (SD) ages of 54.8 (12.3) and 81.3 (4.9) years and dialysis vintages of 1.8 (3.3) and 1.5 (2.9) years (P=0.47), respectively, were identified. Mean at-risk catheter-days were 272 (243) in nonelderly and 318 (240) in elderly patients. Between age groups, there were no significant differences in initial catheter site, type of catheter lock solution, or microbiology results. A total of 208 catheter-related bloodstream infection events occurred (190 events in nonelderly and 18 events in elderly patients), with a catheter-related bloodstream infection incidence per 1000 catheter-days of 1.97 (4.6) in nonelderly and 0.55 (1.6) in elderly patients (P<0.001). Relative to nonelderly patients, the hazard ratio for catheter-related bloodstream infection in the elderly was 0.33 (95% confidence interval, 0.20 to 0.55; P<0.001) after multivariate analysis.

CONCLUSION

Elderly patients on hemodialysis using tunneled central vein dialysis catheters are at lower risk of catheter-related bloodstream infection than their younger counterparts. For some elderly patients, tunneled central vein dialysis catheters may represent a suitable dialysis access option in the setting of nonmaturing arteriovenous fistulae or poorly functioning synthetic grafts.

Treatment options for renal cell carcinoma in renal allografts: a case series from a single institution

Renal cell carcinoma (RCC) is more common in renal transplant and dialysis patients than the general population. However, RCC in transplanted kidneys is rare, and treatment has previously consisted of nephrectomy with a return to dialysis. There has been recent interest in nephron-sparing procedures as a treatment option for RCC in allograft kidneys in an effort to retain allograft function. Four patients with RCC in allograft kidneys were treated with nephrectomy, partial nephrectomy, or radiofrequency ablation. All of the patients are without evidence of recurrence of RCC after treatment. We found nephron-sparing procedures to be reasonable initial options in managing incidental RCCs diagnosed in functioning allografts to maintain an improved quality of life and avoid immediate dialysis compared with radical nephrectomy of a functioning allograft. However, in non-functioning renal allografts, radical nephrectomy may allow for a higher chance of cure without the loss of transplant function. Consequently, radical nephrectomy should be utilized whenever the allograft is non-functioning and the patient's surgical risk is not prohibitive.

Early trends from the Study to Evaluate the Prospective Payment System Impact on Small Dialysis Organizations (STEPPS)

BACKGROUND

Launched in January 2011, the prospective payment system (PPS) for the US Medicare End-Stage Renal Disease Program bundled payment for services previously reimbursed independently. Small dialysis organizations may be particularly susceptible to the financial implications of the PPS. The ongoing Study to Evaluate the Prospective Payment System Impact on Small Dialysis Organizations (STEPPS) was designed to describe trends in care and outcomes over the period of PPS implementation. This report details early results between October 2010 and June 2011.

STUDY DESIGN

Prospective observational cohort study of patients from a sample of 51 small dialysis organizations.

SETTING & PARTICIPANTS

1,873 adult hemodialysis and peritoneal dialysis patients.

OUTCOMES

Secular trends in processes of care, anemia, metabolic bone disease management, and red blood cell transfusions.

MEASUREMENTS

Facility-level data are collected quarterly. Patient characteristics were collected at enrollment and scheduled intervals thereafter. Clinical outcomes are collected on an ongoing basis.

RESULTS

Over time, no significant changes were observed in patient to staff ratios. There was a temporal trend toward greater use of peritoneal dialysis (from 2.4% to 3.6%; P = 0.09). Use of cinacalcet, phosphate binders, and oral vitamin D increased; intravenous (IV) vitamin D use decreased (P for trend for all <0.001). Parathyroid hormone levels increased (from 273 to 324 pg/dL; P < 0.001). Erythropoiesis-stimulating agent doses decreased (P < 0.001 for IV epoetin alfa and IV darbepoetin alfa), particularly high doses. Mean hemoglobin levels decreased (P < 0.001), the percentage of patients with hemoglobin levels <10 g/dL increased (from 12.7% to 16.8%), and transfusion rates increased (from 14.3 to 19.6/100 person-years; P = 0.1). Changes in anemia management were more pronounced for African American patients.

LIMITATIONS

Limited data were available for the prebundle period. Secular trends may be subject to the ecologic fallacy and are not causal in nature.

CONCLUSIONS

In the period after PPS implementation, IV vitamin D use decreased, use of oral therapies for metabolic bone disease increased, erythropoiesis-stimulating agent use and hemoglobin levels decreased, and transfusion rates increased numerically.