Susceptibility of hepato-splanchnic perfusion to intra-abdominal pressure in peritoneal dialysis patients

BACKGROUND

The impact of peritoneal filling on hepato-splanchnic perfusion during peritoneal dialysis has not been fully elucidated yet.

METHODS

Measurements were done in 20 prevalent peritoneal dialysis patients during a peritoneal equilibration test (PET) with 2L of standard dialysate. Data were obtained in the drained state at baseline (T0), after instillation (T1), and after 2 h of dwell time (T2). Intra-abdominal pressure (IAP) was measured by Durand's approach. The hepatic clearance index (KI) of indocyanine-green (ICG) was determined as an indirect measure of hepato-splanchnic blood flow. Cardiac index (CI), heart rate (HR), and total peripheral resistance index (TPRI) were derived from continuous arterial pulse analysis. Fluid volume overload (VO) was evaluated by multifrequency bioimpedance analysis. Ejection fraction (EF) was obtained from echocardiographic examination.

RESULTS

IAP was 5.8 ± 3.5 mmHg at baseline (T0), rose to 9.4 ± 2.8 mmHg after instillation of dialysate (T1), and further to 9.7 ± 2.8 mmHg after 2 h of dwell time (p < 0.001). KI slightly declined from 0.60 ± 0.22 L/min/m2 at T0 to 0.53 ± 0.15 L/min/m2 at T1 (p = 0.075), and returned to 0.59 ± 0.22 L/min/m2 at T2 (p = 0.052). CI, HR, and TPRI did not change significantly. In five patients with an EF < 40% KI was significantly lower at T1 (0.42 ± 0.12 L/min/m2; p = 0.039), and further decreased at T2 (0.40 ± 0.04 L/min/m2; p = 0.016) compared to patients with normal EF (T1: 0.58 ± 0.15 L/min/m2 and T2: 0.67 ± 0.22 L/min/m2).

CONCLUSIONS

Overall, hepatic clearance of ICG as a marker of hepato-splanchnic blood flow is not affected by the filling of the peritoneal cavity.

Continuous Ambulatory Peritoneal Dialysis is Better than Automated Peritoneal Dialysis as First-Line Treatment in Renal Replacement Therapy

This article examines the roles of continuous ambulatory peritoneal dialysis (CAPD) versus automated peritoneal dialysis (APD) as first-line renal replacement therapy. To date, no high-quality large-scale randomized controlled studies have compared CAPD with APD as first-line therapy. However, a discussion on this issue is important so that nephrologists can decide and patients can have a choice of modality on which to start dialysis, especially in the context of health care economics. We review the literature and present Hong Kong as the model of a “CAPD first” policy, an appealing, cost-effective approach for any country.

An ideal renal replacement therapy should provide optimal survival, lowest possible risk for comorbidity, highest level of quality of life, and equally important, acceptable cost to society. When we consider this subject in the context that all patients should be started on one first-line modality, the data suggest that a “CAPD first” policy has all these advantages, with APD probably having the edge only with regard to patient preference. The present review highlights preservation of residual renal function, removal and balancing of sodium, incidence of peritonitis, peritoneal membrane transport status, patient rehabilitation, and financial issues in demonstrating that a “CAPD first” policy is the model that should be adopted.

Acute Central Hemodynamic Effects of a Volume Exchange in Peritoneal Dialysis

Background

Although peritoneal dialysis is considered to offer more hemodynamic stability than hemodialysis, the acute hemodynamic effects of peritoneal dialysis have only been investigated scarcely. The present study assesses the central hemodynamic impact of volume infusion using pH-adjusted icodextrin, thus avoiding interference of glucose, pH, and osmolarity.

Methods

Patients were randomized to 3 different starting volumes (A: 1000 mL, B: 1500 mL, and C: 2500 mL) of icodextrin, followed by addition (A and B) or drainage (C) of 200 mL every 10 minutes for 50 minutes. Local carotid systolic blood pressure (BP; as a surrogate for central BP), augmentation index, and augmentation pressure were measured by applanation tonometry before and after infusion of the starting volumes and after each volume change.

Results

We included 13 patients (median age 57 years). Baseline brachial BP was 126/77 mmHg. After infusion of the starting volume, carotid systolic BP and augmentation pressure increased by 4.7 mmHg ( p = 0.006) and 3.1 mmHg ( p = 0.015). Augmentation index increased by 5.7% ( p = 0.04) and heart rate decreased by 2.6/minute ( p = 0.006). Intraperitoneal pressure increased by 2.3 cm H2O ( p = 0.03). No additional hemodynamic changes except for a rise in diastolic BP with increasing volume ( p = 0.004) were observed after subsequent addition or removal of volumes.

Conclusions

Infusion of peritoneal dialysis fluids causes an acute increase in carotid systolic B P, followed by a progressive rise in diastolic BP. These effects persist until complete drainage of the abdomen and may be due to an enhanced preload, resulting from intraperitoneal venous compression, and/or increased wave reflection.

Supine equilibration of extracellular fluid in peritoneal dialysis varies with intra-abdominal pressure

BACKGROUND

Increased intra-abdominal pressure (PIA) leads to venous congestion in splanchnic and adjoining circulations. The aim is to examine whether PIA in peritoneal dialysis (PD) affects the mobilization of extracellular fluid from the lower body in supine body position.

METHODS

Patients were studied during a regular peritoneal equilibration test (PET) in supine body position using multifrequency bioimpedance analysis to determine extracellular resistance and absolute volume overload (AVO) in wrist-to-ankle (W2A) as well as in ankle-to-ankle (A2A) configurations. Measurements were taken at baseline (T0) after draining the peritoneal cavity, at T1 shortly after filling with 2 L of standard dialysate, and at T2 before taking the 2 h PET samples. PIA was measured from the column height in the PD catheter. Extracellular resistance in the lower extremities (RL) was taken as half of the A2A resistance.

RESULTS

Eighteen patients (56 ± 15 years, 76 ± 21 kg, body mass index (BMI) 26.4 ± 7 kg/m², 13 men) were studied. After having assumed a supine body position for the duration of 17, 77, and 155 min, AVO continuously decreased from 1.6 ± 1.3 (T0) to 1.2 ± 1.5 (T1) and 1.0 ± 1.4 L (T2). RL significantly increased from 238 ± 57 (T0) to 254 ± 62 (T1) and 264 ± 67 Ohm (T2). This increase was negatively correlated to BMI and PIA measured at any time point, but not to net ultrafiltration volume.

CONCLUSIONS

Orthostatic fluid shifts from the lower limbs may take up to 2 h in supine PD patients, especially with high BMI and PIA because of venous congestion in splanchnic and adjoining circulations.

The Occurrence of Increased Intraperitoneal Volume Events in Automated Peritoneal Dialysis in the US: Role of Programming, Patient/User Actions and Ultrafiltration

Background, objectives and methods

Increased intraperitoneal volume (IIPV) can occur during automated peritoneal dialysis (APD). The contribution of factors such as cycler programming and patient/user actions to IIPV has not been previously explored. The relationship between IIPV and cycler programming, patient/user actions, and ultra-filtration over a two-year period was investigated using US data from Baxter cyclers. Drain/fill volume ratios of > 1.6 to ≤ 2.0 and > 2.0 were defined as Level I and Level II IIPV events, respectively.

Results

Level I IIPV events occurred in 2.39% of standard and 4.73% of small fill volume therapies, while Level II IIPV events occurred in 0.26% and 1.33% of therapies, respectively. IIPV events occurred significantly more often in association with tidal peritoneal dialysis (PD) compared to non-tidal PD therapies. In tidal therapies, IIPV events were primarily related to suboptimal programming of total ultrafiltration volume. Factors that increased the odds of IIPV events during standard therapies included programming the initial drain volume target to < 70% of the last fill, and setting minimum drain volumes to < 85% of the fill volume. Bypass of initial drain by patients/users was also associated with a significant increase in the odds of IIPV events in non-tidal, but not tidal PD. An increase in the odds for IIPV was also seen for standard therapies within the highest (> 1,245 mL) versus the lowest (< 427 mL) quartile of ultrafiltration. Similar trends were seen in small fill volume therapies. Clinical presentations associated with IIPV events were not assessed.

Conclusions

IIPV events are more frequent in tidal and small fill volume therapies. The greatest potential for IIPV occurred when the total ultrafiltration was set too low for the patient's UF requirements during tidal therapy. Patient/user bypass of drains without reaching the target drain volume contributes significantly to IIPV events in non-tidal PD therapies. Poorly functioning PD catheters may be central to the cycler programming and patient/user actions that lead to IIPV.

Strategies for preserving residual renal function in peritoneal dialysis patients

Although there have been many advancements in the treatment of patients with chronic kidney disease (CKD) over the last 50 years, in terms of reducing cardiovascular risk, mortality remains unacceptably high, particularly for those patients who progress to stage 5 CKD and initiate dialysis (CKD5d). As mortality risk increases exponentially with progressive CKD stage, the question arises as to whether preservation of residual renal function once dialysis has been initiated can reduce mortality risk. Observational studies to date have reported an association between even small amounts of residual renal function and improved patient survival and quality of life. Dialysis therapies predominantly provide clearance for small water-soluble solutes, volume and acid-base control, but cannot reproduce the metabolic functions of the kidney. As such, protein-bound solutes, advanced glycosylation end-products, middle molecules and other azotaemic toxins accumulate over time in the anuric CKD5d patient. Apart from avoiding potential nephrotoxic insults, observational and interventional trials have suggested that a number of interventions and treatments may potentially reduce the progression of earlier stages of CKD, including targeted blood pressure control, reducing proteinuria and dietary intervention using combinations of protein restriction with keto acid supplementation. However, many interventions which have been proven to be effective in the general population have not been equally effective in the CKD5d patient, and so the question arises as to whether these treatment options are equally applicable to CKD5d patients. As strategies to help preserve residual renal function in CKD5d patients are not well established, we have reviewed the evidence for preserving or losing residual renal function in peritoneal dialysis patients, as urine collections are routinely collected, whereas few centres regularly collect urine from haemodialysis patients, and haemodialysis dialysis patients are at risk of sudden intravascular volume shifts associated with dialysis treatments. On the other hand, peritoneal dialysis patients are exposed to a variety of hypertonic dialysates and episodes of peritonitis. Whereas blood pressure control, using an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB), and low-protein diets along with keto acid supplementation have been shown to reduce the rate of progression in patients with earlier stages of CKD, the strategies to preserve residual renal function (RRF) in dialysis patients are not well established. For peritoneal dialysis patients, there are additional technical factors that might aggravate the rate of loss of residual renal function including peritoneal dialysis prescriptions and modality, bio-incompatible dialysis fluid and over ultrafiltration of fluid causing dehydration. In this review, we aim to evaluate the evidence of interventions and treatments, which may sustain residual renal function in peritoneal dialysis patients.

Relationship between drain volume/fill volume ratio and clinical outcomes associated with overfill complaints in peritoneal dialysis patients

BACKGROUND

To better understand the spectrum of overfill reports and their corresponding clinical severity and etiology, we conducted a review of overfill reports from the Manufacturer and User Facility Device Experience (MAUDE) database, which is within the Food and Drug Administration (FDA) Web site (www.fda.gov).

METHOD

We searched the MAUDE database for events related to overfill reports between 1 January 1995 and 31 December 2008 and recorded drain volume (DV)/fill volume (FV), or DV/FV, and clinical symptoms and signs associated with the overfill report.

RESULTS

Among 462 MAUDE reports with a possible overfill event, 440 reports (95.2%) with a confirmed overfill event contained sufficient information to ascertain the clinical severity of the event. The number of reports with a clinical severity rating of minor, moderate, major, or death was 331, 71, 28, and 10, respectively. The median (range) DV/FV for a subgroup of 292 reports with a clinical severity rating of minor, moderate, major, or death was 1.63 (1.06 - 4.29), 1.71 (1.08 - 5.87), 2.14(1.64 - 2.61), and 2.50 (2.28 - 3.33), respectively. Insufficient drain accounted for a majority of overfill reports.

CONCLUSION

Our analysis of reports from the MAUDE database suggests an association between DV/FV and clinical severity of the reported overfill event, as well as significant patient-to-patient variability with respect to intraperitoneal volume tolerance.

Peritoneal dialysis is not associated with myocardial stunning

BACKGROUND

Hemodynamic changes during hemodialysis can precipitate subclinical myocardial ischemia, which over time contributes to the development of cardiac failure and is associated with a poor prognosis. Peritoneal dialysis (PD) is also associated with acute changes in systemic hemodynamics and a similarly high incidence of cardiovascular disease; we therefore sought to examine whether the hemodynamic effects of a PD exchange would be sufficient to induce subclinical myocardial ischemia.

METHODS

10 patients on PD entered a prospective observational study to determine whether left ventricular (LV) regional wall motion abnormalities (RWMAs) developed following a dialysate exchange. Serial echocardiography with quantitative analysis was used to assess ejection fraction and regional systolic LV function (shortening fraction). Blood pressure (BP) and hemodynamic variables were measured using continuous pulse wave analysis.

RESULTS

We observed a very low frequency of RWMA development (5/100 regions). Only 1 patient had more than 1 RWMA and 6 patients were entirely unaffected. Overall mean shortening fraction increased when comparing pre and post values for both 2-chamber (from 3.06% ± 1.5% to 4.26% ± 1.3%, p = 0.001) and 4-chamber (from 3.00% ± 0.7% to 3.67% ± 0.9%, p = 0.021) analyses. Mean arterial pressure fell by a small degree during drainage of dialysate, with a larger rise in BP observed during instillation. These changes were driven by changes in peripheral resistance that fell during drainage and rose during instillation.

CONCLUSIONS

In contrast to hemodialysis, the acute effects of PD do not result in subclinical myocardial ischemia.

Continuous renal replacement therapies in patients with liver disease

Patients with acute and chronic liver disease are prone to hypotension, and mortality increases when acute kidney injury supervenes. Hypotension during renal replacement therapy compromises cerebral perfusion, which can exacerbate cerebral edema in cases of fulminant hepatic failure and those with encephalopathy due to chronic liver failure. As such, any renal replacement therapy utilized should have minimal adverse effects on cardiovascular and cerebrovascular stability. Continuous modes of renal replacement therapy have been shown to cause less cardiovascular and cerebrovascular instability compared to other modalities, and as such are the treatments of choice for this group of critically ill patients.

Continuous renal replacement therapies in patients with acute neurological injury

Acute neurological injury may occur in patients with end-stage kidney disease on dialysis. Less frequently, acute kidney injury requiring renal dialytic support develops following acute neurological injury. Surrounding any site of neurological injury there is a penumbra of damage which is potentially reversible. To maximize full potential neurological recovery in patients requiring renal dialytic support, it is important that treatments do not themselves cause further cerebral ischemia. Standard intermittent hemodialysis is associated with cerebral swelling even in healthy outpatients and often with episodes of intradialytic hypotension. Continuous modes of renal replacement therapy have been shown to cause fewer surges in intracranial pressure and greater stability of cerebral perfusion pressure than standard intermittent techniques. In patients with acute neurological injury, renal replacement therapy should be carefully adapted to minimize cardiovascular instability and reduce the rate of change of serum osmolality.

Cardiac function in an African dialysis population with a low prevalence of pre-existing cardiovascular disease

Cardiac dysfunction is highly prevalent in dialysis patients in the developed world, and is a major cause of morbidity and mortality. The relative impact of pre-existing cardiac disease and dialysis/uremia on cardiovascular morbidity are not clear. We conducted a retrospective, cross-sectional analysis of cardiac function and mortality in 202 incident and prevalent dialysis patients over an 18-month period in a population with a low prevalence of cardiovascular disease at dialysis initiation. Systolic dysfunction was defined as an ejection fraction (EF) of <50%. Left ventricular hypertrophy (LVH) was determined by echocardiography or electrocardiogram. Clinical data was collected by chart review. Ninety-nine percent of patients were black, with a mean age of 41.7 +/- 10.1 years, and median follow up 28 months (range 1-216 months). Echocardiograms were available in 132 patients. Seventy-seven patients received hemodialysis, and 55 received peritoneal dialysis. Mean EF was 63.2 +/- 11.1. EF was not lower in patients with greater duration of dialysis, although LVH tended to increase (not statistically significant). In 39 patients who died during the study period, cardiac function was not different from survivors, and no patient died of ischemic heart disease or heart failure. In conclusion, in a population of patients with a low prevalence of cardiovascular disease at dialysis initiation, cardiac function appears preserved over time, and cardiac morbidity and mortality are low. This finding suggests that dialysis and uremia per se, in the absence of pre-existing cardiac disease, may not be major contributors to cardiovascular morbidity.

Comparison of volume overload with cycler-assisted versus continuous ambulatory peritoneal dialysis

BACKGROUND AND OBJECTIVES

Cycler-assisted peritoneal dialysis (CCPD) has been associated with decreased sodium removal compared with continuous ambulatory peritoneal dialysis (CAPD) as a result of peritoneal sodium sieving during the short dwells that are associated with CCPD. This may have adverse consequences for management of extracellular fluid volume (ECFV). This study compared ECFV in patients who received CAPD or CCPD; CCPD dwell times were maximized by limiting the number of exchanges, and the use of icodextrin for the long daytime dwells was widespread.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was an observational, cross-sectional study of 158 prevalent patients (90 CAPD, 68 CCPD). Demographic data, blood work, and 24-h dialysate and urine samples were collected from all participants between January 2004 and July 2006. They subsequently underwent assessment of ECFV by multifrequency bioimpedance spectroscopy analysis. Multivariate analysis was used to determine the relationship between peritoneal dialysis modality and ECFV. Potential cofounders including age, comorbidity, time on dialysis, residual renal function, and icodextrin use were identified a priori.

RESULTS

There were no differences in BP, use of antihypertensive medications, or the presence of peripheral edema between CAPD and CCPD patients. Similarly, there was no difference in the ratio of ECFV to total body water between CAPD (51.8%) and CCPD (51.9%) patients (P = 0.929).

CONCLUSIONS

There is no difference in BP, sodium removal, or volume control in patients who use a contemporary approach to CCPD that uses fewer night cycles and liberalizes the use of icodextrin when compared with CAPD.

Albumin infusion fails to restore circulatory function following paracentesis of tense ascites as assessed by beat-to-beat haemodynamic measurements

AIMS

To study whether circulatory changes during large volume paracentesis (LVP) in patients with liver cirrhosis and tense ascites as assessed by novel non-invasive haemodynamic measuring technology are reversed by subsequent albumin infusion.

MATERIALS AND METHODS

Eleven patients with portal hypertensive ascites secondary to liver cirrhosis of Child's class B or C were studied during LVP (10.7 +/- 4.4 l) and subsequent infusion of albumin. Digital arterial pulse waves were continuously measured by vascular unloading technique providing data for beat-to-beat values of systolic (P(s)), diastolic (P(d)) and mean arterial pressures (P(m)), respectively, as well as for heart rate (F(h)), stroke volume (V(s)), cardiac output (Q(co)) and peripheral resistance (R). Data extrapolated to the end of paracentesis, albumin infusion and follow-up phases were compared with the end of the equilibration phase.

RESULTS

At the end of paracentesis, P(s), P(m) and P(d) changed by -14 +/- 15% (p < 0.05), -16 +/- 11% (p < 0.01) and -17 +/- 11% (p < 0.001), respectively, whereas Q(co) and F(h) did not change substantially. There was a highly significant increase in V(s) by +21 +/- 25% (p < 0.01). The largest change was seen in R which significantly decreased by -29 +/- 24% (p < 0.01). This change was not reversed by infusion of albumin and persisted up to the end of follow-up.

CONCLUSION

The haemodynamic changes following LVP appear to be first and foremost controlled by changes in peripheral resistance with insufficient cardiac compensation. Further studies combining albumin with vasopressors for prevention of paracentesis-induced circulatory changes are needed.

Effects of peritoneal dialysis fluid biocompatibility on baroreflex sensitivity

Conventional low biocompatibility peritoneal dialysis (PD) fluid composition has been driven by manufacturing expediency and cost limitations. PD is associated with significant acute changes in cardiovascular functional parameters, at least in part influenced by fluid composition. Short-term control of blood pressure (BP) is under control of the baroreflex arc. The aim of this study was to investigate the effects of PD fluid biocompatibility on baroreflex sensitivity (BRS). We studied 10 non-diabetic established continuous ambulatory PD patients, in a randomized crossover trial comparing conventional and biocompatible PD fluids. Systemic hemodynamics were continuously monitored using digital pulse-wave analysis. Plasma glucose and insulin were assessed during treatment with both 1.36% and 3.86% glucose-containing fluids. BRS was calculated offline from continuous BP and interbeat interval data. BRS was significantly higher with conventional PD fluid during both 1.36% (P<0.001) and 3.86% (P<0.001) dwells. Systolic BP was higher; heart rate, stroke volume, and cardiac output were lower; and total peripheral resistance increased during exposure to either fluid. There were significant differences between fluids with respect to the magnitude of these responses. Plasma glucose and insulin concentrations, and ultrafiltration volumes were significantly higher during the 3.86% dwell than the 1.36% dwell, but there were no differences between standard and biocompatible fluids. We have demonstrated for the first time that PD fluid biocompatibility rapidly affects BRS. These changes occur against a background of cardiovascular variability, hyperinsulinemia, and hyperglycemia. Further research is needed to explore the mechanism and, more importantly, the consequences of these findings.

Dialysis-Induced Regional Left Ventricular Dysfunction Is Ameliorated by Cooling the Dialysate

Dialysis patients who develop cardiac failure have a poor prognosis. Recurrent subclinical myocardial ischemia is important in the genesis of heart failure in nondialysis patients. It has previously been demonstrated that subclinical ischemia occurs during hemodialysis; therefore, this study examined whether the improved stability of cool-temperature dialysis lessens this phenomenon. Ten patients who were prone to intradialytic hypotension entered a randomized, crossover study to compare the development of dialysis-induced left ventricular (LV) regional wall motion abnormalities (RWMA) at dialysate temperatures of 37 and 35 degrees C. Serial echocardiography with quantitative analysis was used to assess ejection fraction and regional systolic LV function. BP and hemodynamic variables were measured using continuous pulse wave analysis. The severity of thermal symptoms was scored using a simple questionnaire. Forty-nine new RWMA developed in nine patients during hemodialysis with dialysate at 37 degrees C (HD(37)), compared with thirteen RWMA that developed in four patients during HD(35) (odds ratio 3.8; 95% confidence interval 2.1 to 6.9). The majority of RWMA displayed improved function by 30 min after dialysis. Overall, regional systolic LV function was significantly more impaired during HD(37) (P < 0.001). BP was higher during HD(35), with fewer episodes of hypotension as a result of a higher peripheral resistance and no difference in stroke volume. The development of thermal symptoms was heterogeneous, with most patients tolerating HD(35) well. This study confirms previous findings of reversible LV RWMA that develop during hemodialysis. It also shows that this phenomenon can be ameliorated by reducing dialysate temperature, a simple intervention with no cost implications.