Heart rate variability in diabetic and non-diabetic renal transplant patients

Backround: Heart rate variability (HRV) has been used to investigate the autonomic modulation of heart rate. Diminished HRV has been observed in diabetic autonomic neuropathy, a condition associated with increased mortality. Uraemia is associated with impaired autonomic function, but reports on the effects of uraemia on HRV are scarce.
Methods: HRV and its circadian variation were studied in 12 diabetic and 11 non-diabetic renal transplantation and in 12 control patients. HRV in time and frequency domains was determined from 24-hour ECG recordings.
Results: In the diabetic group, all time domain and frequency domain measures of HRV were markedly reduced ( P <0.05), when compared with the control group, and the circadian variation of HRV was absent. The mean (SD) amplitudes (ms) in the frequency bands were: high frequency: 3 (1), 6 (3) and 15 (3); low frequency: 9 ( 7 ), 16 (10) and 25 (8); very low frequency: 14 (8), 23 (12) and 30 (11) in the diabetic and non-diabetic uraemic and in the control patients, respectively. In non-diabetic uraemic patients, a tendency to reduced HRV was observed, but no statistical differences in HRV measures were found when compared with the control group.
Conclusion: The severe impairment of HRV in patients with end-stage diabetic nephropathy is probably due to autonomic neuropathy and partly also to the co-existing heart diseases. It may be a contributing risk factor for ventricular arrhythmias and sudden death in these patients. Uraemia alone causes similar but less severe changes in HRV.     

Association between cardiovascular autonomic neuropathy and left ventricular hypertrophy in diabetic haemodialysis patients.

BACKGROUND: Patients with diabetic nephropathy are likely to have neurological complications including cardiovascular autonomic dysfunction, which is related to increased risk of mortality. We investigated whether cardiovascular autonomic neuropathy is associated with left ventricular hypertrophy (LVH) in diabetic haemodialysis patients. METHODS: Holter electrocardiography was carried out for 24 h with time and frequency domain analyses of heart rate variability in 154 diabetic (age 62+/-11 years) and 63 non-diabetic haemodialysis patients (62+/-10 years). The left ventricular mass index (LVMI) was determined by echocardiography. We used the percentage of differences exceeding 50 ms between adjacent normal RR intervals (pNN50) in time domain analysis and the power in the high-frequency range (HF: 0.15-0.40 Hz) in frequency domain analysis as indicators of parasympathetic activity. RESULTS: The mean LVMI was greater in diabetic than in non-diabetic patients (168+/-63 vs 144+/-54 g/m(2), P<0.01). LVMI inversely correlated with pNN50 (r = -0.270, P = 0.0007, n = 154) and HF (r = -0.277, P = 0.0005, n = 154) in diabetic patients, but not in non-diabetic patients. By multiple logistic analysis, LVH was strongly associated with pNN50 (odds ratio 0.088; 0, <2%; 1, >/=2%) and HF (odds ratio 0.058; 0, <500 ms(2); 1, >/=500 ms(2)) in diabetic patients. CONCLUSIONS: Impaired parasympathetic activity, which indicates cardiovascular autonomic neuropathy, was associated with the presence of LVH in diabetic haemodialysis patients. The co-existence of cardiovascular autonomic neuropathy and LVH may be one of the key factors for the high incidence of cardiovascular events in diabetic haemodialysis patients.     

Are diabetic patients in danger at renal transplantation? An invasive perioperative study

It is assumed that diabetic patients with uraemia have more complications at renal transplantation than those who are not diabetic. We compared the preoperative ECGs, and invasive perioperative haemodynamic and oxygenation parameters in 15 diabetic and 15 non-diabetic uraemic patients undergoing renal transplantation. The number of patients with increased QT dispersion in the ECG was higher in diabetic than in non-diabetic patients (P<0.05). Before anaesthesia, heart rate and mean arterial pressure were higher (P<0.05) in the diabetic than in the non-diabetic group. After preanaesthetic volume loading all patients showed a hyperdynamic circulation, which subsided during anaesthesia. However, stroke volume index remained unchanged. Four patients in the diabetic group and six in the non-diabetic group needed additional oxygen therapy after surgery. No cardiac dysrhythmias were noted. However, the increased QT dispersion in diabetic patients calls for an adequate perioperative ECG monitoring for dysrhythmias. The diabetic and non-diabetic uraemic patients performed equally well at renal transplantation. In conclusion, renal transplantation for diabetics is justified.     

QT dispersion and autonomic function in diabetic and non-diabetic patients with renal failure

We have studied 13 patients with diabetic nephropathy and 13patients with uraemia of other origin undergoing renal transplantation,and 12 control patients undergoing general surgery. QTc dispersionand maximum QTc interval were calculated from the 12-lead ECG,and cardiovascular autonomic function tests were performed.QTc dispersion was significantly greater in diabetic (mean 100(SD 37) ms) and non-diabetic (51 (17) ms) uraemic patients thanin control patients (29 (10) ms), and it differentiated thegroups better than maximum QTc. In diabetic patients, severeautonomic neuropathy was common. In other uraemic patients lesssevere disturbances in autonomic function were found. In diabeticuraemic patients, increased QTc dispersion and severe autonomicneuropathy may indicate high risk for cardiac arrhythmias. Inour opinion, QTc dispersion and autonomic function tests maygive valuable information on perioperative risks.     

Influence of angiotensin converting enzyme inhibitor treatment on cardiac autonomic modulation in patients receiving haemodialysis

BACKGROUND: Cardiovascular disease mortality among patients with end stage renal disease (ESRD) exceeds that which is predicted by traditional risk factors. Sudden death accounts for up to 15-38% of patients with ESRD found dead at home. Heart rate variability (HRV) is a reliable measure of autonomic modulation and has a very strong predictive value for ventricular arrhythmias and sudden death. A lower HRV is associated with increased risk. Modifying autonomic tone pharmacologically reduces death from dysrhythmia in the general population but has not been studied in ESRD. METHODS: We examined the effect of ramipril, an angiotensin converting enzyme inhibitor (ACEI) known in the general population to increase HRV, on cardiac function and heart rate variability in patients with renal failure. Eligible subjects on haemodialysis underwent a 2-week washout period free of ACEI or beta blockers, during which time hypertension was treated with amlodipine, which has been shown not to affect HRV. Haemodynamic and HRV measurements were obtained at baseline and after subjects were treated for 4 weeks with an ACEI. RESULTS: Haemodynamics did not differ at 0 and 4 weeks. Baseline HRV values were markedly below those found in the general population, indicating pronounced predominance of sympathetic tone over vagal tone. Actual worsening of HRV with ACEI treatment was evident in several major time domains. The time domain SDNN (the standard deviation of all normal RR intervals) fell from 42.0 +/- 24.8 ms to 20.1 +/- 16.1 ms (P = 0.004) and the triangulation index fell from 178.0 +/- 94.0 to 115 +/- 59.2 (P = 0.01). A trend toward reduced HRV was seen in several other time domains. CONCLUSION: These findings suggest that, unlike the general population, treatment of ESRD patients with an angiotensin converting enzyme inhibitor may cause a deleterious shift toward increased cardiac sympathetic nervous system tone.     

Cardiac autonomic dysfunction in hemodialysis patients assessed by heart rate variability

Sudden cardiac death (SCD) is a major problem in patients with end stage renal disease (ESRD) on haemodialysis (HD) and several risk factors are recognized. A major problem may be the autonomic dysfunction which is observed in more than 50 % of ESRD patients. Autonomic dysfunction, and in particular cardiac autonomic dysfunction, is associated with a high risk of ventricular arrhythmias which may eventually lead to SCD. A non-invasive method for measuring cardiac autonomic function is by assessing heart rate variability (HRV) and this review will focus on HRV in HD patients. ESRD patients have an impaired HRV which may partly explain their high risk of SCD. Some intervention studies in HD patients using HRV as a surrogate parameter have been published and are also discussed in this review.     

Differences in heart rate variability during haemodialysis and haemofiltration.

BACKGROUND: The aim of our study was to evaluate whether convective (haemofiltration, Hf) and diffusive (haemodialysis, Hd) dialysis techniques induce different patterns of long- and short-term autonomic adjustments in haemodynamically stable dialysis patients. METHODS: Ten haemodynamically stable Hd patients were studied. Each patient underwent a block of six Hd sessions, then was switched to six Hf. During the last session of each dialytic treatment, continuous beat to beat measurements of systolic arterial pressure (SAP) and heart rate (HR) were performed. Spectral analysis of heart rate variability (HRV) was made before and during the treatment to evaluate the modification of autonomic nervous system activity. RESULTS: Baseline values of plasma sodium, body weight, HR and SAP were not different for the two considered methods of dialysis, while the baseline values of normalized LF were significantly higher in Hf as compared to Hd and the opposite was observed for HF powers (P < 0.001). Sodium balance and body weight loss per hour did not differ between Hd and Hf while body temperature was kept constant in all sessions. Throughout the dialytic procedures, with both techniques, SAP was constant, while HR diminished from the first hour till the end of the procedure (P < 0.05). An increase in LF (and decrease in HF) was noticed only in the case of Hd, considering normalized units (P < 0.05). These selective changes were maintained also during the recovery after the procedure. CONCLUSIONS: The spectral analysis of RR interval variability during Hd and Hf suggests a potential autonomic advantage with Hf, to be added to the well-recognized intrinsic greater haemodynamic stability.     

Low-frequency Spectral Power of Heart Rate Variability Is Not a Specific Marker of Cardiac Sympathetic Modulation

Background: Heart rate variability in the frequency domain has been proposed to reflect cardiac autonomic control. Therefore, measurement of heart rate variability may be useful to assess the effect of epidural anesthesia on cardiac autonomic tone. Accordingly, the effects of preganglionic cardiac sympathetic blockade by segmental epidural anesthesia were evaluated in humans on spectral power of heart rate variability. Specifically, the hypothesis that cardiac sympathetic blockade attenuates low-frequency spectral power, assumed to reflect cardiac sympathetic modulation, was tested.

Methods: Ten subjects were studied while supine and during a 15-min 40- degrees head-up tilt both before and after cardiac sympathetic blockade by segmental thoracic epidural anesthesia (sensory block: C6-T6). ECG, arterial pressure, and respiratory excursion (Whitney gauge) were recorded, and a fast-Fourier-transformation was applied to 512-s data segments of heart rate derived from the digitized ECG at the end of each intervention.

Results: With cardiac sympathetic blockade alone and the subjects supine, both low-frequency (LF, 0.06-0.15 Hz) and high-frequency (HF, 0.15-0.80 Hz) spectral power remained unchanged. During tilt, epidural anesthesia attenuated the evoked increase in heart rate (+11 *symbol* min sup -1 + 7 SD vs. +6 + 7, P - 0.024). However, while during tilt cardiac sympathetic blockade significantly decreased the LF/HF ratio (3.68 plus/minus 2.52 vs. 2.83 plus/minus 2.15, P = 0.041 vs. tilt before sympathetic blockade), a presumed marker of sympathovagal interaction, absolute and fractional LF and HF power did not change.     

Cardiovascular complications in renal failure.

Cardiovascular diseases are a leading cause of death in end-stage renal disease (ESRD) largely as a result of the progressively increasing age of ESRD patients and the broad constellation of uremia-associated factors that can adversely affect cardiac function. Hypertension, one of the leading causes of renal failure, is a major culprit in this process, causing left ventricular hypertrophy, cardiac chamber dilation, increased left ventricular wall stress, redistribution of coronary blood flow, reduced coronary artery vasodilator reserve, ischemia, myocardial fibrosis, heart failure, and arrhythmias. In addition to impairing the coronary microcirculation, hypertension may contribute to the development of atherosclerotic coronary artery disease, particularly in the presence of the many lipid abnormalities observed in ESRD. These patients have reduced high-density lipoprotein cholesterol and increased plasma triglyceride concentrations, and there is a defect in cholesterol transport. Other abnormalities that may contribute to atherosclerotic coronary artery disease in ESRD are reduced high-density lipoprotein cholesterol synthesis and reduced activity of the reverse cholesterol pathway. Treatment with fibric acids, nicotinic acids, and lovastatin may be useful in lowering cholesterol and triglyceride concentrations in some of these patients. The incidence of coronary artery disease in ESRD populations is difficult to determine. About 25 to 30% of ESRD patients with angina have no evidence of significant coronary artery disease, and an undetermined number have silent coronary disease. The presence of resting electrocardiographic abnormalities caused by hypertension or conduction defects makes it difficult to accurately diagnosis coronary artery disease in ESRD populations by noninvasive methods, including exercise testing and thallium scintigraphy with or without the use of dipyridamole. Hypotension is a frequent complication of the dialytic process. Many factors have been implicated, including autonomic neuropathy. There is no consensus on the function of the efferent limb of the sympathetic nervous system. The afferent limb (arterial baroreflex function) is felt to be impaired. Further, there may be defects in the ability of the cardiovascular system to respond to sympathetic nerve activity. Most studies of autonomic function have used indirect measurements. Studies are underway that use techniques to assess sympathetic function directly. Such experiments with microneuropathy suggest greater skeletal sympathetic muscle discharge in uremic patients than in normal patients.     

Heart rate variability (HRV) in kidney failure: measurement and consequences of reduced HRV.

A common cause of death in end-stage renal disease (ESRD) patients on dialysis is sudden cardiac death (SCD). Compared to the general population, the percentage of cardiovascular deaths that are attributed to SCD is higher in patients treated by dialysis. While coronary artery disease (CAD) is the predominant cause of SCD in dialysis patients, reduced heart rate variability (HRV) may play a role in the higher risk of SCD among other risk factors. HRV refers to beat-to-beat alterations in heart rate as measured by periodic variation in the R-R interval. HRV provides a non-invasive method for investigating autonomic input into the heart. It quantifies the amount by which the R-R interval or heart rate changes from one cardiac cycle to the next. The autonomic nervous system transmits impulses from the central nervous system to peripheral organs and is responsible for controlling the heart rate, blood pressure and respiratory activity. In normal individuals, without cardiac disease, the heart rate has a high degree of beat-to-beat variability. HRV fluctuates with respiration: it increases with inspiration and decreases with expiration and is primarily mediated by parasympathetic activity. HRV has been used to evaluate and quantify the cardiac risk associated with a variety of conditions including cardiac disorders, stroke, multiple sclerosis and diabetes. In this narrative review, we will examine the association between HRV and SCD. This report explains the measurement of HRV and the consequences of reduced HRV in the general population and dialysis patients. Lastly, this review will outline the possible use of HRV as a clinical predictor for SCD in the dialysis population. The current understanding of SCD based on HRV findings among the ESRD population support the use of more aggressive treatment of CAD; greater use of angiotensin converting enzyme inhibitor (ACE-i)/angiotensin receptor blockers (ARBs) and beta-blockers and more frequent and/or nocturnal haemodialysis to improve the survival of a patient with kidney failure.     

Effects of sustained insulin-induced hypoglycemia on cardiovascular autonomic regulation in type 1 diabetes

Effects of hypoglycemia on cardiac autonomic regulation may contribute to the occurrence of adverse cardiac events. This study assessed the effects of sustained hyperinsulinemic hypoglycemia on cardiovascular autonomic regulation in type 1 diabetic patients and their nondiabetic counterparts. The study consisted of 16 type 1 diabetic patients and 8 age-matched healthy control subjects who underwent euglycemic and hypoglycemic clamp procedures in a random order. Heart rate variability was measured from continuous electrocardiogram recordings by time and frequency domain methods, along with Poincare plot analysis during both a hyperinsulinemic-euglycemic and hypoglycemic clamp at three different glucose levels (4.5-5.5, 3.0-3.5, and 2.0-2.5 mmol/l). Controlled hypoglycemia resulted in an increase of supine heart rate in both the diabetic patients (from 72 +/- 9 to 80 +/- 11 bpm, P < 0.01) and the control subjects (from 59 +/- 5 to 65 +/- 5 bpm, P < 0.05) and progressive reductions of the high-frequency spectral component and beat-to-beat heart rate variability (SD1; P < 0.05 in the diabetic patients and P < 0.01 in control subjects). No significant changes in heart rate variability occurred during the euglycemic clamp. We conclude that hypoglycemia results in a reduction of cardiac vagal outflow in both diabetic and nondiabetic subjects. Altered autonomic regulation may contribute to the occurrence of cardiac events during hypoglycemia.     

Accelerated vascular calcification and relative hypoparathyroidism in incident haemodialysis diabetic patients receiving calcium binders.

BACKGROUND: Vascular calcification and low bone turnover with a relatively low parathyroid hormone (PTH) often coexist in diabetic patients undergoing haemodialysis. Since calcium salts (CaS) are used extensively as primary phosphate binders and have been associated with progressive vascular calcification, we studied the effects of CaS on coronary arteries and parathyroid activity in incident haemodialysis diabetic patients. METHODS: We measured the change in coronary artery calcium scores (CACS) with sequential electron beam computed tomography (EBCT) in 64 diabetic and 45 non-diabetic patients, randomized to CaS or sevelamer within 90 days of starting haemodialysis. CACS measurements were repeated after 6, 12 and 18 months. Serum intact PTH (iPTH), calcium and phosphorus were serially tested. RESULTS: During the study period, serum phosphate was similar in diabetic and non-diabetic patients. Serum calcium levels were similar at baseline (2.3+/-0.25 mmol/l for both) and increased significantly with CaS treatment (P<0.05) both in diabetic and non-diabetic patients but not with sevelamer. Diabetic patients treated with CaS showed a significantly greater CACS progression than sevelamer-treated patients (median increase 177 vs 27; P=0.05). During follow-up, diabetic patients receiving CaS were significantly more likely to develop serum iPTH values<16 pmol/l than diabetic patients treated with sevelamer (33% vs 6%, P=0.005) and had a lower mean iPTH level (24+/-16 vs 31+/-14 pmol/l; P=0.038). CONCLUSIONS: The management of hyperphosphataemia with CaS in haemodialysis diabetic patients is associated with a significantly greater progression of CACS than with sevelamer. These effects are accompanied by iPTH changes suggestive of low bone turnover.     

Haemodynamic and catecholamine responses to induction of anaesthesia and tracheal intubation in diabetic and non-diabetic uraemic patients

We have studied cardiovascular and catecholamine responses toinduction of anaesthesia and tracheal intubation in 13 patientswith diabetic nephropathy, in 12 patients with uraemia of otherorigin and in 12 ASA I control patients. All uraemic patientswere undergoing renal transplantation. Cardiovascular autonomicfunction tests indicated that severe autonomic neuropathy wascommon in the diabetic patients; less severe impairment of autonomicfunction was found in the non-diabetic uraemic patients. Thesystolic pressor response to intubation was greater in diabeticuraemic patients than in the other groups (P < 0.05). Bothuraemic groups had higher plasma catecholamine concentrationsthan the ASA I patients both before and after induction of anaesthesia.The increased plasma concentrations of catecholamines in theuraemic patients may be a result of impaired clearance of catecholaminesand higher sympathoadrenal activity needed to maintain cardiacfunction. The normal systolic pressor response to tracheal intubationin the uraemic patients indicates that the capacity of the cardiovascularsystem to respond to a stressful stimulus was preserved in thesepatients also, in spite of autonomic neuropathy. The greaterresponse in the diabetic group may be caused by increased sensitivityto catecholamines and loss of autonomic control.     

Autonomic nervous system response to epidural analgesia in laboring patients by wavelet transform of heart rate and blood pressure variability

BACKGROUND: Epidurals are effective in relieving labor pain but result in a sympathectomy that may compromise maternal hemodynamic stability and fetal perfusion. Decreases in blood pressure and heart rate can be corrected, but markers of autonomic activity would be useful to predict and prevent such changes. The goal of this study was to find markers describing the changes in autonomic nervous system activity with epidural anesthesia in laboring patients. METHODS: The authors analyzed heart rate variability and blood pressure variability in 13 laboring patients using wavelet transform, a time-frequency analysis that accommodates rapid changes in autonomic activity. Heart rate and blood pressure variability were obtained 5 min before and 10 min after injection of 20 ml bupivacaine, 0.125%, and 50 microg fentanyl in the epidural space. RESULTS: Blood pressure and heart rate were not affected by epidural analgesia. However, high-frequency power of heart rate variability increased after epidural (increase in parasympathetic drive). The ratio of low-frequency:high-frequency power of heart rate variability decreased. High- and low-frequency power of blood pressure variability decreased (decrease in sympathetic outflow). CONCLUSIONS: Indices of parasympathetic and sympathetic activity after neuraxial blockade in laboring patients can be obtained by analysis of both heart rate variability and blood pressure variability. The analysis by wavelet transform can discern changes in autonomic activity when values of blood pressure and heart rate do not vary significantly. Whether this technique could be used to predict and prevent hemodynamic compromise after neuraxial blockade merits further studies.     

Echocardiographic assessment of systolic function in dialysis patients

Echocardiography has been widely used to investigate cardiac function in uraemic patients. There is no doubt about the validity of this technique in certain situations, particularly the demonstration of structural abnormalities and pericardial effusions. However, the assessment of cardiac function by measurement of cardiac dimensions and their rate of change is complicated by the profound influence of altered loading conditions, common in uraemia, on the measurements obtained. This is a particular problem in the assessment of changes in cardiac function during haemodialysis. Even studies utilising isovolaemic dialysis are open to criticism, due to the effects of altered afterload on cardiac emptying. Recently the experimental finding that end-systolic volume is independent of end-diastolic volume and linearly related to afterload has raised the possibility that non-invasive assessment of end-systolic indices may allow load-independent assessment of intrinsic cardiac contractility in patients. However, none of the studies using these indices in uraemic patients has validated the assumption that they are indeed load-independent in this clinical situation. Evidence is presented suggesting that the end-systolic pressure:volume relationship is altered by the administration of a volume load and that manipulation of afterload without autonomic blockade results in markedly increased contractility, presumably due to reflex sympathetic activity. More work is required before these indices are used uncritically in dialysis patients.     

Autonomic insufficiency as a factor contributing to dialysis-induced hypotension.

BACKGROUND: Autonomic insufficiency is considered a factor that contributes to dialysis-induced hypotension (DIH). However, the relationship between the two conditions has not been fully elucidated. METHODS: We investigated 44 haemodialysis patients using [(123)I]-meta-iodobenzylguanidine (MIBG) scintigraphy and power-spectral analysis (PSA) of heart rate variability. The patients were divided into four groups: a diabetic group with DIH, a diabetic group without DIH, a non-diabetic group with DIH, and a non-diabetic group without DIH. In these groups the heart to mediastinum average count rate (H/M), MIBG washout rate, and low- and high-frequency components of PSA were compared. RESULTS: From the [(123)I]-MIBG scintigraphy, for both early and delayed images, H/M of the groups with DIH were lower than in groups without DIH, in both diabetics and non-diabetics (P<0.05). For the early images, H/M of the diabetic groups were lower than in the non-diabetic groups, in the groups both with and without DIH (P<0.01). For the delayed images, H/M of the diabetic group was lower than in the non-diabetic group, in the groups with DIH (P<0.05). The MIBG washout rate was the highest in the diabetic group with DIH (P<0.05 vs diabetic and non-diabetic groups without DIH). The PSA of heart rate variability showed a good discrimination of the low-frequency component between the non-diabetic patients with and without DIH (P<0.05). Mean ultrafiltration volume and its rate were not different among the four groups. CONCLUSION: Autonomic insufficiency is more severe in patients with DIH than in those without, and its degree may be enhanced in diabetic patients. For the management of DIH, special care should be addressed not only to dry weight but also to autonomic insufficiency.     

Intra- and post-dialytic changes of haemoglobin concentrations in non-anaemic haemodialysis patients.

BACKGROUND: Non-anaemic haemodialysis (HD) patients are potentially more prone to the adverse effects of ultrafiltration-induced haemoconcentration. No study, however, has assessed the effects of dialytic session on haemoglobin (Hb) levels in these patients. METHODS: The levels of Hb and total protein before, at the end (T0) and up to 120 min (T120) after the third HD session of the week were compared in non-anaemic (Hb >13 g/dl, n = 14, NOR) and anaemic (Hb = 11-12 g/dl, n = 18, LOW) HD patients. RESULTS: The intradialytic weight loss was similar in the two groups (4.0 +/- 0.9 and 4.1 +/- 0.9% body weight). During the treatment, Hb levels increased to the same extent in both groups (from 14.4 +/- 1.2 to 16.3 +/- 1.9 g/dl in NOR, and from 11.4 +/- 0.8 to 12.7 +/- 0.9 g/dl in LOW) in the presence, presumably, of a smaller plasma volume in NOR, whereas the increment of total protein was greater in NOR (from 7.1 +/- 0.2 to 9.6 +/- 0.5 g/dl) than in LOW (from 7.3 +/- 0.6 to 8.7 +/- 0.8 g/dl) (P < 0.0001). At T120, the Hb decline in NOR was almost double that measured in LOW (-9.2 +/- 3.0 vs -4.7 +/- 2.4%, P < 0.001). Consequently, Hb concentration did not differ from the pre-dialytic value in NOR (P = 0.10), but persisted higher in LOW (P < 0.005). The extent of the post-dialytic decrement of Hb was inversely related to the total protein values at T0 (r = -0.547, P = 0.0012). CONCLUSIONS: This study indicates that in NOR: (i) the extent of intradialytic increment of Hb is limited by a greater intradialytic plasma refilling; (ii) the greater plasma refilling persists after the end of dialysis, with the restoration of pre-dialytic Hb levels within the initial 2 h; and (iii) the force driving this phenomenon resides mainly in the larger changes of total protein concentration.     

The hemodynamic and humoral responses to tilting in diabetic patients on chronic hemodialysis treatment

Hemodynamic and humoral responses to tilting were examined in order to elucidate the autonomic nervous function in diabetic hemodialysis patients. Eleven diabetic (DM) and eleven non-diabetic (non-DM) patients on maintenance hemodialysis treatment were involved in the experimentation, matching the age and the duration of hemodialysis. Cardiac output, blood pressure, plasma renin activity (PRA), norepinephrine (NE) and epinephrine (EP) were measured before and 5 minutes after the 45 degree tilting. By the tilting the blood pressure significantly fell in DM, whereas it rose slightly but significantly in non-DM. In both groups, however, the heart rate remained unchanged, and either cardiac index or stroke volume index decreased equally. The percentile increase in total peripheral resistance index (TPRI) was significantly smaller in DM (14.6%) than in non-DM (27.9%). There was a significant correlation between the changes in TPRI and diastolic blood pressure (r = 0.730, p less than 0.01). NE and EP increased significantly in non-DM but not in DM. Blood pressure reduced by the tilting in DM was associated with a small or equivocal response in either TPRI or plasma NE. The heart rate did not respond to the tilting in both groups. These results indicate that both sympathetic and parasympathetic nervous systems are deranged in diabetic hemodialysis patients but parasympathetic dysfunction is evident even in non-diabetic hemodialysis patients.     

The reflex control of vasopressin in haemodialysis patients.

We studied the reflex arginine vasopressin (AVP) response to hypotensive, isosmotic fluid subtraction (by isolated UF) in 14 uraemic patients on renal dialysis treatment: five with normal autonomic function and nine with autonomic involvement of various degrees. Fluid subtraction caused a comparable mean arterial pressure (MAP) decrease in the two groups. The reduction in right atrial pressure was inversely related with the severity of autonomic neuropathy (rs = -0.72, P = 0.004), being distinctly attenuated in the second group (P = 0.006). Plasma arginine vasopressin increased similarly in patients with normal autonomic function and in those with autonomic involvement. The response of patients with haemodialysis hypotension was similar to that of other patients. Reflex control of arginine vasopressin is preserved even in the presence of afferent/central neuropathy or more advanced, widespread autonomic damage in uraemic man. The data suggest that it is unlikely that altered release of arginine vasopressin is involved in the pathogenesis of haemodialysis hypotension.