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Biomedical subjects

B Charra

Publications and source records attributed to B Charra.

At least 55 records · Page 3Linked to original sources
PubMed1998

Blood pressure control in dialysis patients: importance of the lag phenomenon.

Failure by the world dialysis community to understand and use the dry-weight method of blood pressure (BP) control has resulted in an increasing incidence of treatment-resistant hypertension, which remains the principal cause of cardiovascular morbidity and mortality. This failure may in part be because the relationship between the extracellular volume (ECV) and BP is not simple and linear, but complex, because of a lag of several weeks between the normalization of the time-averaged ECV and the decrease in BP. Another cause for this failure may be the unwillingness to taper and stop all antihypertensive medications during the transition from hypertension to normotension. In this report, we describe in detail the lag phenomenon, document its presence during treatment in other populations, and describe how this knowledge is used in the application of the dry-weight method of drug-free BP control in the dialysis population.

Antihypertensive Agents↗
PubMed1998

Hemodialysis trends in time, 1989 to 1998, independent of dose and outcome.

The 1989 Morbidity, Mortality, and Prescription of Dialysis Symposium (Dallas, TX) deeply modified the way of prescribing and delivering hemodialysis (HD) in the United States, as elsewhere. Among strategies emerging for end-stage renal disease treatment improvement, increasing the delivered dose has been the central issue, whereas the session time effect has remained an unsettled question. The purpose of this article is to analyze the trends in HD session time over the last decade in Tassin, France, and elsewhere and their relationship to outcome, independent of dialysis dose. The published data indicate that in the United States, there has been an increase in session time. Outside the United States, where session time had been somewhat longer, there has been either no change or a decrease in time without apparent ill effects. The dialysis dose, as measured by the urea Kt/V, has increased everywhere because improved technology allows for efficient toxin removal within a very short dialysis session. In Tassin, a recent limited experience of high-dose shortened dialysis did not show a significant short-term survival difference, but an impaired control of blood pressure (BP) and nutrition. Thus far, the highest HD long-term survival rates have been reported by the groups that used the largest doses and the longer times of HD. Effects of dose and time are, at this point, impossible to disentangle. A longer dialysis time improves extracellular volume (ECV) and BP control and decreases cardiovascular mortality. Shortening the HD session leads to impaired control of BP and increasing cardiovascular morbidity (by far the first cause of mortality on HD). In the future, the length of dialysis session should be governed by the demand of BP control.

France↗
PubMed1998

Is post-dialysis urea rebound significant with long slow hemodialysis?

BACKGROUND: According to previous studies, postdialysis urea rebound (PDUR) is achieved within 30-90 min, leading to an overestimation of Kt/V of between 15 and 40% in 3- to 5-hour dialysis. The purpose of the study was to assess the impact of PDUR on the urea reduction ratio (URR), Kt/V and normal protein catabolic rate (nPCR) with long 8-hour slow hemodialysis. METHODS: This study was performed in 18 patients (13 males/5 females), 62.5 +/- 11.7 years of age, hemodialyzed for 3-265 months. Initial nephropathies were: 3 diabetes; 2 polycystic kidney disease; 3 interstitial nephritis; 2 nephrosclerosis; 3 chronic glomerulonephritis, and 5 undetermined. Residual renal function was negligible. The dialysis sessions were performed using 1- to 1.8-m2 cellulosic dialyzers during 8 h, 3 times a week. Blood flow was 220 ml/min, dialysate flow 500 ml/min, acetate or bicarbonate buffer was used. Serial measurements of the urea concentration were obtained before dialysis, immediately after dialysis (low flow at t = 0), and at 5, 10, 20, 30, 40, 60, 90 and 120 min, and before the next session. The low-flow method was used to evaluate the access recirculation, second-generation Daugirdas formulas for Kt/V, and Watson formulas for total body water volume estimation. The difference between the expected urea generation (UG) and urea measured after dialysis (global PDUR) defines net PDUR (n-PDUR). RESULTS: The n-PDUR usually became stable after 58 +/- 25 (30-90) min. Its mean value was 17 +/- 10% of the 30-second low-flow postdialysis urea (3.9 +/- 2 mmol/l). This small postdialysis urea value and the importance of UG in comparison with shorter dialysis justify the use of n-PDUR. Ignoring n-PDUR would lead to a significant 4% overestimation (p < 0.001) of the URR (79 +/- 7 vs. 76 +/- 8%), 12% of Kt/V (1.9 +/- 0.4 to 1.7 +/- 0.38) and 4% of the nPCR (1.1 +/- 0.3 to 1.05 +/- 0.3). n-PDUR correlated negatively with postdialysis urea (r = 0.45 p = 0.05), positively with URR (r = 0.31 p = 0.01) and Kt/V (r = 0.3 p = 0.03) but not with K, and negatively with the urea distribution volume (r = 0.33 p = 0.05). Mean total recirculation, ultrafiltration rate, predialysis urea levels and urea clearance did not correlate with n-PDUR. CONCLUSION: We found a significant PDUR in long-slow hemodialysis after a mean of 1 h after dialysis. This PDUR has a less important impact upon dialysis delivery estimation than short 3- to 5-hour hemodialysis, especially for the lower Kt/V or URR ranges. This is explained by the low-flux, high-efficiency, and long-term dialysis. Its inter-individual variability incites us to calculate PDUR on an individual basis.

Aged↗
PubMed1998

Blood pressure control and hemodynamic changes in patients on long time dialysis treatment.

In dialysis patients blood pressure can be well controlled with long dialysis (3 times a week for 8 h) in contrast to a more common short dialysis regime (3 times a week for 4 h). We studied whether the good blood pressure control in patients on long dialysis as compared to patients on short dialysis was associated with a decrease in extracellular fluid volume. Two-day interdialytic ambulatory blood pressure monitoring was performed in 26 non-diabetic patients on long dialysis, in 22 patients on short dialysis, matched for the years they were on dialysis treatment, and during 24 h in 19 healthy volunteers. After full equilibration, 24 h after dialysis, echography of the inferior caval vein was performed to determine fluid state. Cardiac dimensions and stroke index were measured by echocardiography. A blood sample was drawn for the determination of electrolytes and vasoactive hormones. 73% of the patients on short dialysis were using antihypertensive medication in contrast to none of the patients on long dialysis. However, blood pressure was significantly lower in patients on long dialysis (115 +/- 21/67 +/- 11 mm Hg) when compared to patients on short dialysis (143 +/- 26/81 +/- 16 mm Hg). Indexed caval vein diameter, left ventricular diameter index, and atrial natriuretic peptide were not significantly different in patients on long dialysis compared to patients on short dialysis. Also the cardiac index was comparable in patients on long and short dialysis. However, the total peripheral resistance index was significantly lower in patients on long dialysis compared to the patients on short dialysis and normal controls. The left ventricular mass index was increased in both patients on long and short dialysis compared to controls. We conclude that patients on long dialysis have adequate blood pressure control that seems mainly to be caused by a low total peripheral resistance. These data also suggest that factors other than a lower fluid state contribute to the good blood pressure control in patients on long dialysis.

Adult↗
PubMed1997

Arterial compliance in patients on long-treatment-time dialysis.

Arterial compliance is found to be reduced in haemodialysis patients. It is not clear whether decreased arterial compliance in uraemic patients is a consequence of long-standing increased mean arterial blood pressure or a consequence of the uraemic state. An adequate blood pressure can be achieved by long-treatment-time dialysis of 8 h three times a week. We studied femoral and carotid artery wall properties in 24 normotensive patients on long-treatment-time dialysis and 24 normal controls matched for mean arterial pressure, age, sex, and body mass index. Arterial distensibility coefficient and compliance coefficient were determined with a vessel wall movement detector system, 24 h after dialysis in the supine position. The patients were 5.9 +/- 6.6 years on long-treatment-time dialysis at a Kt/V of 1.8 +/- 0.4. We found no significant differences in mean arterial pressure or pulse pressure between patients (85 +/- 13, 55 +/- 17 mmHg) and controls (84 +/- 6, 50 +/- 13 mmHg). Femoral distensibility coefficient and compliance coefficient were lower in patients (6.0 +/- 2.4 10(-3)/kPa; P < 0.05, 0.52 +/- 0.28 mm2/kPa; n.s.) compared to the controls (8.8 +/- 4.0 10(-3)/kPa, 0.67 +/- 0.38 mm2/kPa). No differences in carotid distensibility coefficient and compliance coefficient were found between patients (12.8 +/- 4.6 10(-3)/kPa, 0.72 +/- 0.30 mm2/kPa) and controls (14.1 +/- 4.4 10(-3)/kPa, 0.70 +/- 0.23 mm2/kPa). We conclude that patients on long-treatment-time-dialysis have an increased stiffening of the muscular femoral artery but not of the more elastic carotid artery. Results suggest that the uraemic state itself has a deleterious effect on the elastic properties of the muscular femoral artery.

Aged↗
PubMed1997

Central venous catheters for haemodialysis: looking for optimal blood flow.

Central venous catheters are commonly used for haemodialysis patients and represent, in our centre, about 15% of the permanent vascular accesses with a total number of more than 230 central venous catheters over the last 10 years. Inadequate blood flow may occur and upsets the nurses, the patients, and the nephrologist. The aim of this study was to identify the factors of the catheter dysfunction. We studied prospectively 25 chronic haemodialysed patients with central venous catheters, 14 women and 11 men, 65 +/- 16 (55-89) years of age, treated with haemodialysis for 6.7 +/- 7 (1-26) years. Catheters were tunnelled silicone twin catheters (Permcath Quinton n = 18, Twincath Hemotec n = 7) in right (n = 19) and left internal jugular (n = 6) inserted by percutaneous Seldinger techniques. We studied the localization of the catheter tip (superior vena cava, right atrium, right ventricular, inferior vena cava), the central venous pressure before and after haemodialysis, the blood pressure (BP) before and after haemodialysis, the interdialytic weight gain, the number of symptomatic hypotensions during the 10 last dialyses. The patients were divided into two groups: group I with usual adequate catheter function (n = 18) and group II with frequent dysfunctions (n = 7). Central venous pressure before dialysis was significantly higher in group I with adequate blood flow and the catheter's tip was more frequently found localized in the right cardiac cavities than in the vena cava. When central venous pressure before dialysis was over 5 mmHg, no dysfunction occurred. Blood pressure was not different between the two groups. We found no correlation between central venous pressure and BP, interdialytic weight gain and symptomatic hypotensions. We could not predict the central venous pressure from the mean BP but there was a higher frequency of hypotensions in the hypovolaemic patients. Optimal haemodynamic conditions will be provided by a catheter tip in the right cardiac cavities and a central venous pressure over 5 mmHg which can be provided with vascular filling or dry weight revaluation.

Aged↗
PubMed1996

Clinical assessment of dry weight.

Unsatisfactory control of blood pressure (BP) leading to an increased rate of cardiovascular events is the main cause of mortality in haemodialysis. BP control has deteriorated since haemodialysis session times have been reduced. Inadequate BP control most often is due to a failure to achieve and maintain dry weight. Dry weight and normotension have been gradually omitted in the goals of dialysis, satisfactory dialysis being reduced to an 'adequate' urea Kt/V. Ideal dry body weight needs a reappraisal. What is dry weight? How should it be clinically assessed, established and maintained in patients? The problems encountered in estimating dry weight can be solved at the bedside in most cases. The additional laboratory, echography and impedancemetry methods are research tools that hopefully can be made simpler and lower in cost so they can be used everyday at the bedside. In the mean time, with the exception of ambulatory blood pressure measurement, one must rely on careful and repeated clinical observation to determine and maintain dry weight.

Blood Pressure↗
PubMed1996

Multifrequency bioimpedance in assessment of dry weight in haemodialysis.

The use of multifrequency bioimpedance (MFB) for determination of dry weight (DW) in haemodialysis (HD) patients was evaluated in three studies. In Study 1, the fluid state [total body water (TBW) and extracellular volume (ECV)] was measured by MFB in 82 normotensive patients. 41 hypertensive patients and in 30 healthy subjects. TBW and ECV were expressed as per cent of body weight (BW). In Study 2, DW of five hypertensive HD patients was gradually decreased during 3 months and ECV (MFB) and blood pressure (48 h ambulatory blood pressure monitoring) were measured at the beginning and end of study. In Study 3, we measured the fluid status repeatedly by MFB and the diameter of the inferior vena cava (DIVC) by ultrasound before, during and 2 h post-HD. In Study 1, the hypertensive patients had significantly greater TBW (P < 0.05) than the normotensive patients before (50.3 +/- 6.5% vs 47.6 +/- 5.8%) and after HD (48.8 +/- 7.8% vs 45.7 +/- 6.4%) and ECV (P < 0.001) before (29.4 +/- 3.6% vs 26.8 +/- 3.5%) and after HD (27.0 +/- 4.0% vs 24.6 +/- 3.5%), Post-HD ECV in the normotensive patients was similar to that in the healthy subjects. In Study 2, more efficient ultrafiltration resulted in reduction of BW and ECV along with a decrease in blood pressure and need for antihypertensive medication. In Study 3, both ECV and DIVC decreased following the removal of fluid during HD. ECV maintained stable values during the post-HD period, unlike DIVC which increased significantly (P < 0.005) due to refilling from the interstitial space. We conclude that MFB is an appropriate non-invasive method for DW determination, which is highly reproducible and technically simple to use.

Adult↗
PubMed1996

Importance of treatment time and blood pressure control in achieving long-term survival on dialysis.

A drastic reduction in hemodialysis (HD) time has been based on the dialysis dose measurement in terms of urea Kt/V exclusively and on the use of high efficiency dialysers. It was subtly coupled to a de-emphasis of the use of HD to normalize blood pressure. In Tassin we have maintained long slow HD with an overall excellent patient survival. We analyze the influence of the different factors of this survival: the place of dry weight and blood pressure control without use of antihypertensive medication is emphasized, and the role of dialysis dose and nutrition is discussed. Adequacy should be defined in terms of these additive conditions. Long slow HD allows one to fulfill these conditions easily. Shortening of dialysis time should not interfere with the control of blood pressure.

Adult↗
PubMed1995

Segmental necrosis of ascending colon in haemodialysis patients.

A segmental necrosis of the ascending colon sometimes affecting the terminal ileum was observed 13 times in 12 end-stage renal disease patients over a 5400 patient-years observation period. In all but three cases the patient was operated within 24 h of onset of the abdominal pain. Three patients had a bowel perforation; nine had a limited intestinal necrosis. All underwent a partial resection or colectomy. Two died within 1 month. In all cases the mucosa was necrotic, the submucosa small vessels were congested and the mesenteric vessels were normal. Ischaemic bowel disease has been previously reported in uraemic patients, but our cases do not fit with the usual reported features of this complication. The absence of typical mesenteric infarction, vascular thrombosis, stenosis or major atherosclerotic lesions is surprising. The ascending colon topography of the lesions is very unusual. Ischaemia, constipation and other factors may play a role.

Colon↗
PubMed1995

Sleep apnea incidence in maintenance hemodialysis patients: influence of dialysate buffer.

A high prevalence of sleep disorders and sleep apnea syndrome in hemodialysis (HD) patients has been known for 10 years. Acetate, the buffer once most commonly used, favors intradialytic hypoxemia through hypoventilation and ventilation-perfusion changes. The aim of the present study was to assess the influence of buffer, acetate or bicarbonate, on sleep and ventilation during the night subsequent to an afternoon (2-7 p.m.) dialysis session. Ten patients, 8 males and 2 females, aged 35-71 years, dry weight 55-72 kg, on dialysis 15 h a week for 6-67 months, were randomly assigned first to acetate or bicarbonate, then to the other mode of treatment. After a series of six sessions using the same buffer, polysomnographic recordings from 9.00 p.m. to 6.00 a.m. were obtained. Sex, age, weight, data of first dialysis, blood pressure and sleep disorder-related symptoms were not correlated with the sleep apnea syndrome. Prolonged or important oxygen desaturations were never observed. Central apnea occurred more frequently during the night following acetate dialysis: x = 33 (0-180) versus 3 (0-15), p < 0.05. Obstructive apneas were not different. A defective modulation of ventilatory control after acetate HD might be held responsible for central apnea, which would constitute one more case for a widespread use of bicarbonate HD.

Acetates↗
PubMed1995

Interdialysis blood pressure control by long haemodialysis sessions.

High blood pressure (BP) is a major factor contributing to the high incidence of cardiovascular morbidity and mortality in haemodialysis (HD) patients. According to predialysis casual BP measurements, long HD has been shown to provide good BP control. To confirm this result during the period between dialysis sessions, we performed ambulatory monitoring of BP in 91 non-selected HD patients (mean age, 58.7 (14.1) years; 14% incidence of nephrosclerosis and diabetes mellitus; treatment duration, 93.0 (77.2) months; 3 x 8 h/week, cuprophane, acetate buffer in 95% of the patients). Only one patient (1.1%) was receiving an antihypertensive medication. Ambulatory BP results were systolic (S) BP, 119.4 (19.9) mmHg; diastolic (D) BP, 70.6 (12.9) mmHg; mean (M) BP, 87.6 (13.9) mmHg. These values were significantly lower than the casual predialysis BP data and close to the reference values reported by Staessen et al. in a meta-analysis including 3476 normotensive subjects. The MBP was inversely correlated with the treatment duration, but not with interdialysis weight gain. The MBP increased significantly in the last part of the interdialysis period, and this rise was not correlated with the interdialysis weight gain. The nocturnal/diurnal ratios for SBP and DBP for the HD patients (0.97 and 0.92) were higher than the reference values reported by Staessen, (0.87 and 0.83), and argued against a nocturnal decrease in BP. We found that 52.1% of the patients had an abnormal nocturnal BP fall (MBP fall < 5%). This feature worsened during the second night of the interdialysis period.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure Monitoring, Ambulatory↗
PubMed1995

[Peritoneal dialysis of substitution: how to evaluate the quality of purification, the criteria of dialysis efficacy].

Peritoneal dialysis adequacy in the narrowest sense of the world can be evaluated by several indexes. Residual kidney function and caloric protein intake strongly affect the protein metabolism (creatinine, urea) they reflect. The correlation between dialysis adequacy indexes and clinical issue (survival, mortality and morbidity) is rather poor. Each index sets the inferior security limit, but in no way a target to be aimed at. Furthermore, the artificial organ should maintain a normal fluid and electrolyte balance and blood pressure, as performed by the natural kidney. The posology indexes do not materialize this important function. No single indicator can replace clinical evaluation and good sense.

Dietary Proteins↗
PubMed1994

Control of blood pressure in long slow hemodialysis.

Hypertension is a major cause of mortality and morbidity in hemodialysis patients. A long slow dialysis (8 h/session) was used in 692 unselected patients. It allowed for an excellent control of blood pressure without the need of antihypertensive medications. Cardiovascular morbidity and mortality were lower in the subgroups of patients presenting with a lower predialysis mean arterial pressure. The control of the extracellular volume with a low rate of intradialytic hypotensive episodes is the most probable explanation of this result. Another possible mechanism is the restoration by the large dose of dialysis of the nitric oxide vasodilator action inhibited by the accumulation of dimethylarginine in the serum of uremic patients.

Adult↗