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PubMed1990

Time-related increase in hematocrit on chronic hemodialysis: uncertain role of renal cysts.

We studied the long-term changes in hematocrit in 283 center hemodialysis patients. Mean duration of dialysis (+/- SD) was 53.8 +/- 43.4 months, with a range of 6 to 176 months. The correlations of hematocrit with clinical factors, laboratory values, and renal cystic changes were investigated. Time on dialysis was the strongest single predictor of hematocrit for the whole group (r = 0.351, P less than 0.001) and for men and women analyzed separately. Longitudinal 5-year (n = 83) and 10-year (n = 21) data showed a continuous increase in hematocrit levels over time (r = 0.414, P less than 0.001 over 10 years). Patients at the dialyzer reuse center (n = 224) had higher hematocrit levels than those at the center that did not reuse (n = 59). Although time on dialysis was strongly correlated with increasing extent of renal cystic change (r = 0.387, P less than 0.001), the correlations of cyst extent and time on dialysis with hematocrit were not independent by multiple regression analysis. We conclude that hematocrit increases progressively over time in patients on chronic hemodialysis. The mechanisms responsible for this do not seem to involve cystic transformation of the kidneys and remain unclear.

Adult↗
PubMed2001

Influence of baseline hematocrit and hemodilution on BOLD fMRI activation.

Current understanding of blood oxygenation level dependent (BOLD) fMRI physiology predicts a close relationship between BOLD signal and blood hematocrit level. However, neither this relationship nor its effect on BOLD percent activation (BPA) has been empirically examined in man. To that end, BPA in primary visual cortex in response to photic stimulation was determined in a group of 24 normal subjects. A positive linear relationship between BPA and hematocrit was seen, particularly in men. To evaluate the effect of change in hematocrit on BPA, 9 men were studied before and following isotonic saline hemodilution, resulting in an average 6% reduction in hematocrit and an 8-31% reduction in BPA. No significant change in the number of activated pixels was seen. A model of predicted BPA as a function of hematocrit and vessel size was developed, and results from this model closely mirrored the empiric data. These results suggest that hematocrit significantly influences the magnitude of BPA and that such baseline factors should be accounted for when comparing BOLD data across groups of subjects, particularly in the many instances in which hematocrit may vary systematically. Such instances include several disease states as well as studies involving sex differences, drug administration, stress and other factors. Finally, the robust agreement between predicted and empiric data serves to validate a semiquantitative approach to the analysis of BOLD fMRI data.

Brain↗
PubMed1998

Perioperative myocardial ischemic episodes are related to hematocrit level in patients undergoing radical prostatectomy.

BACKGROUND: The anemia associated with perioperative blood conservation has raised concerns regarding the safety of these strategies in patients with ischemic cardiovascular disease. Therefore the relationship between hematocrit level and myocardial ischemic episodes in a group of elderly patients undergoing elective noncardiac surgery was studied. STUDY DESIGN AND METHODS: One hundred ninety patients undergoing radical prostatectomy were randomly assigned to one of three blood conservation groups: preoperative autologous blood donation, acute normovolemic hemodilution, and preoperative erythropoietin therapy with acute normovolemic hemodilution. Patients underwent ambulatory electrocardiography monitoring to evaluate for myocardial ischemia at randomization (baseline), 7 days preoperatively, throughout surgery, and for 24 hours after surgery. RESULTS: Myocardial ischemic episodes occurred in 61 (34%) of 181 evaluable patients. Patients with hematocrit levels < 28 percent immediately after surgery were significantly (p = 0.05) more likely to have intraoperative and postoperative ECG ischemic episodes. Intraoperative ischemia and tachycardia correlated (r = 0.21, p = 0.008) with hematocrit levels. Hematocrit levels after surgery were associated with postoperative ischemia (r = 0.14, p = 0.03) and duration of myocardial ischemic episodes (r = 0.14, p = 0.04). After adjusting for other risk factors, intraoperative tachycardia episodes, hematocrit level < 28 percent immediately after surgery, and risk factors for coronary artery disease were independently associated with the likelihood of intraoperative ischemia (r = 0.36, p = 0.002, area under receiver operating characteristic curve = 0.73). Similarly, tachycardia episodes and hematocrit levels < 28 percent immediately after surgery were independently associated with ischemic episodes during the first postoperative day (r = 0.30, p = 0.004, area under receiver operating characteristic curve = 0.71). CONCLUSION: A hematocrit level < 28 percent is independently associated with risk for myocardial ischemia during and after noncardiac surgery. Avoidance of cardiac complications may require higher transfusion thresholds, closer attention to tachycardia, or better monitoring for ischemia.

Electrocardiography↗
PubMed2000

Adequacy of dialysis and differences in hematocrit among dialysis facilities.

Despite the clearly established relationship between adequacy of dialysis and response to erythropoietin, recent guidelines on anemia management in end-stage renal disease (ESRD) omit mention of dialysis adequacy while advocating the use of large amounts of intravenous iron. To determine the relative effects of adequacy of dialysis and intravenous iron on hematocrit, we studied 309 hemodialysis patients and analyzed data from 141 hemodialysis facilities in New York State (ESRD Network 2), as well as data from all 18 ESRD Networks in the United States, for the last quarter of 1997. Among the 309 subjects, mean hematocrit differed between quartiles of urea reduction ratio (URR; F statistic = 4; P: = 0.008). Patients with URRs greater than 70% were 2.6 times more likely to have hematocrits greater than 33% (odds ratio, 2.6; 95% confidence interval [CI], 1.3 to 5.3; P: = 0.009) after adjustment for other factors. Mean dialysis facility (n = 141) hematocrits correlated directly with mean URRs (r = 0.32; P: = 0.001). Facilities with a mean URR greater than 70% were three times more likely to have a mean hematocrit greater than 33% (odds ratio, 3; 95% CI, 1.2 to 7.5; P: = 0.02). The percentage of patients in each of the 18 ESRD Networks with hematocrits of 33% or greater correlated inversely with the percentage of patients administered intravenous iron (r = -0.53; P: = 0.03) after adjustment for dose of erythropoietin. We conclude that adequacy of dialysis predicts the response to erythropoietin at both patient and dialysis facility levels. Patients with low hematocrits primarily because of inadequate dialysis may inappropriately be administered excess intravenous iron intended as a corrective measure.

Hematocrit↗
PubMed2003

Comparison of urea reduction ratio and hematocrit data reported in different data systems: results from the Centers for Medicare & Medicaid Services and the Renal Network Inc.

BACKGROUND: Urea reduction ratio (URR) and hematocrit values reported on the Centers for Medicare & Medicaid Services (CMS) claims were compared with data from two different databases. METHODS: URRs and hematocrits from two different CMS databases (National Claims History and End-Stage Renal Disease Clinical Performance Measures [CPM] Project) and one Network database (The Renal Network Data System [TRNDS]) were compared for October through December 1998 and December 1998, respectively. A sample of records from the regional database was validated by independent chart review. RESULTS: Nationally, the percentage of agreement for patients with URRs of 65% or greater and less than 65% was 94% (kappa, 0.81; 95% confidence interval [CI], 0.80 to 0.83); regionally, the percentage of agreement was 95% (kappa, 0.85; 95% CI, 0.84 to 0.86). Nationally, linear regression of hematocrit values from both data sources yielded r(2) congruent with 0.61 each month and r(2) = 0.70 for average values during the 3-month study period. Nationally, the percentage of agreement for patients with hematocrits of 33% or greater and less than 33% was 84% (kappa approximately 0.66) each month. Regionally, linear regression of monthly hematocrit values from both data sources yielded r(2) = 0.66, and percentage of agreement for patients with hematocrits of 33% or greater and less than 33% was 87% (kappa, 0.71; 95% CI, 0.70 to 0.73). Validation of a sample of records in the TRNDS database resulted in 98% agreement for patients with URRs of 65% or greater and less than 65% and 96% agreement for patients with hematocrits of 33% or greater and less than 33%. CONCLUSION: Although there is general agreement between clinical variables submitted on the claims and in the CPM Project, some variation exists. Data from either source yield the same information when classifying patients as above or below threshold values.

Anemia↗
PubMed2000

Normalization of hematocrit in hemodialysis patients does not affect silent ischemia.

UNLABELLED: Transient ST-segment depression measured on ambulatory ECG monitors has been described as representing silent ischemia. Patients who demonstrate silent ischemia have been reported to show increased mortality compared to patients without silent ischemia. We undertook this study to determine if the correction of anemia in End Stage Renal Disease (ESRD) patients from (+/- = standard deviation) 30 +/- 3 to 42 +/- 3 with the use of Epoietin alfa would result in decreased silent ischemia in patients with clinically evident ischemic heart disease or congestive heart failure. METHODS: Thirty one ESRD patients with congestive heart failure or patients with clinically-evident ischemic heart disease were randomized into one of two arms. Patients in Group A had their hematocrit increased with the use of slowly escalating doses of Epoietin alfa to 42 +/- 3% and patients in Group B were maintained with a hematocrit of 30 +/- 3% throughout the course of the study. All patients had a 24 hour Holter monitor recording at baseline and at 28 weeks after randomization (when they had reached their target hematocrit). Significant silent ischemia was considered to be present if patients demonstrated at least 60 seconds of > or = 1 mm ST segment depression. RESULTS: Fifteen patients were randomized to Group A and 16 patients were randomized to Group B. The mean hematocrit increased in group A from 29.1 +/- 2.4% to 40.8 +/- 5.2% after 30 weeks. The mean hematocrit in Group B remained stable at 30 +/- 3% throughout the course of the study. Ten patients demonstrated silent ischemia at baseline. At follow up patients in group A demonstrated a mean of 1.7 +/- 4.9 minutes of ischemia compared to 1.1 +/- 3.4 minutes in group B. These were not significantly different. A similar number of patients in group A and Group B required adjustments in their anti-anginal medication during the course of the study. CONCLUSION: It is possible to increase hematocrit to near normal levels in hemodialysis with the administration of exogenous Epoietin alfa. The increase in hematocrit form 30 +/- 3% to 42 +/- 3% is not associated with a change in the level of silent ischemia these patients demonstrate.

Anemia↗
PubMed2005

Do blood tests cause anemia in hospitalized patients? The effect of diagnostic phlebotomy on hemoglobin and hematocrit levels.

OBJECTIVE: To determine whether phlebotomy contributes to changes in hemoglobin and hematocrit levels in hospitalized general internal medicine patients. DESIGN: Retrospective cohort study. SETTING: General internal medicine inpatient service at a tertiary care hospital. PARTICIPANTS: All adult patients discharged from the Toronto General Hospital's internal medicine service between January 1 and June 30, 2001. A total of 989 hospitalizations were reviewed and 404 hospitalizations were included in our analysis. MEASUREMENTS AND MAIN RESULTS: Mean (SD) hemoglobin and hematocrit changes during hospitalization were 7.9 (12.6) g/L (P<.0001) and 2.1% (3.8%) (P<.0001), respectively. The mean (SD) volume of phlebotomy during hospital stay was 74.6 (52.1) mL. On univariate analysis, changes in hemoglobin and hematocrit were predicted by the volume of phlebotomy, length of hospital stay, admission hemoglobin/hematocrit value, age, Charlson comorbidity index, and admission intravascular volume status. The volume of phlebotomy remained a strong predictor of drop in hemoglobin and hematocrit after adjusting for other predictors using multivariate analysis (P<.0001). On average, every 100 mL of phlebotomy was associated with a decrease in hemoglobin and hematocrit of 7.0 g/L and 1.9%, respectively. CONCLUSIONS: Phlebotomy is highly associated with changes in hemoglobin and hematocrit levels for patients admitted to an internal medicine service and can contribute to anemia. This anemia, in turn, may have significant consequences, especially for patients with cardiorespiratory diseases. Knowing the expected changes in hemoglobin and hematocrit due to diagnostic phlebotomy will help guide when to investigate anemia in hospitalized patients.

Aged↗
PubMed1983

Importance of perfusate hematocrit for insulin- and glucagon-induced choleresis in the perfused rat liver.

Insulin and glucagon stimulate bile production in the intact rat without affecting the biliary excretion rate of bile acids. This effect was not demonstrable in rat liver perfused with human erythrocytes suspended in a Krebs-Henseleit-bicarbonate buffer at a hematocrit of about 18%. The present experiments demonstrate that the choleretic effect of insulin and glucagon observed in the intact rat is reproducible in perfused rat liver if the hematocrit of the perfusate is raised to about 35%. An increase in perfusate hematocrit is also accompanied by a 65% rise in hepatic oxygen consumption and a 27% rise in the basic production of bile, due to an increase in bile acid-independent bile formation. The mechanism by which these changes in perfusate hematocrit influence the function of the perfused liver is obscure. The difference in oxygen content of the perfusates appears to be without importance. Judged from lactate-pyruvate and beta-hydroxybutyrate-acetoacetate ratios of perfusate as well as electron microscopy, maldistribution of perfusate flow and local hypoxia were not evident in perfusions with low hematocrit. A part of the increase in hepatic oxygen consumption seen with a rise in perfusate hematocrit can, however, be explained by an increase in lactate supply from erythrocyte glycolysis. The results stress the importance of perfusate hematocrit for optimal bile production of the perfused rat liver.

Animals↗
PubMed1986

Regional lung hematocrit in humans using positron emission tomography.

Regional lung hematocrit ratio (R) was measured in five normal subjects and five patients (2 with pneumonia, 2 with nephrotic syndrome with anemia, and 1 with pancreatitis) using positron emission tomography, a red cell marker 11CO, and a plasma marker [methyl-11C]albumin). The measurements were made in a transaxial thoracic section at midheart level with the subject in supine posture and with a spatial resolution of 1.7 cm. The normal regional hematocrit ratio (means +/- SE) calculated for the lung was 0.90 +/- 0.014, 0.94 +/- 0.023 for the thoracic wall, and 1.00 +/- 0.003 for the heart chambers. The regional lung hematocrit ratio in the patients ranged between 0.81 and 0.86. No correlation was found among the regional lung hematocrit ratio and regional blood volume, lung extravascular density, and the peripheral hematocrit (obtained from venous blood samples). To the extent that 70% of the pulmonary blood in the field of view is in larger vessels with normal hematocrit, the hematocrit in the capillary bed is approximately two-thirds that of the peripheral venous value. Blood volume measurements on the basis of single vascular tracers need to take account of these results.

Adult↗
PubMed1986

Distortion of calculated whole-body hematocrit during lower-body immersion in water.

We found a difference between the venous hematocrits of immersed and nonimmersed arms during immersion of the lower body in cold water but not during a comparable exposure to warm water. Fourteen healthy men were exposed to three different experimental conditions: arm immersion, body immersion, and control. The men always sat upright while both upper extremities hung vertically at their sides. During arm immersion, one forearm was completely immersed for 30 min in either cold water (28 degrees C, n = 7) or warm water (38 degrees C, n = 7). This cold-warm water protocol was repeated on separate days for exposure to the remaining conditions of body immersion (immersion of 1 forearm and all tissues below the xiphoid process) and control (no immersion). Blood samples were simultaneously drawn from cannulated veins in both antecubital fossae. Hematocrit difference (Hct diff) was measured by subtracting the nonimmersed forearm's hematocrit (Hct dry) from the immersed forearm's hematocrit (Hct wet). Hct diff was approximately zero when the men were exposed to the control condition and body immersion in warm water. In the remaining conditions, Hct wet dropped below Hct dry (P less than 0.01, 3-way analysis of variance). The decrements of Hct diff showed there were differences between venous hematocrits in immersed and nonimmersed regions of the body, indicating that changes of the whole-body hematocrit cannot be calculated from a large-vessel hematocrit soon after immersing the lower body in cold water.

Adult↗
PubMed2006

The use of erythropoietin in patients undergoing radical prostatectomy: effects on hematocrit, transfusion rates and quality of life.

OBJECTIVE: It was the aim of this study to prospectively study the effects on hematocrit levels, transfusion rates and quality of life (QOL) indices in men preoperatively supplemented with recombinant erythropoietin (rEPO) undergoing radical prostatectomy for clinically localized prostate cancer. METHODS: Thirty men undergoing radical prostatectomy were randomized either to receive rEPO (n=25) or to serve as controls (n=25). Outcome measurements obtained preoperatively, as well as 10 days and 6 weeks postoperatively included serum hematocrit levels, transfusion rates and QOL indices (using SF-12 validated questionnaires). RESULTS: The rEPO group had a significant increase in preoperative hematocrit (median increase=4 points; p=0.002). Although there were no significant differences in hematocrit at 10 days, the rEPO had a significantly higher hematocrit value at 6 weeks (p=0.0086). No differences were observed in transfusions rates between groups (4% in each group). SF-12 mental and SF-12 physical scores were not different between the two groups at any time point. CONCLUSION: Preoperative administration of rEPO significantly increases preoperative and postoperative hematocrit levels. However, no differences were observed with regard to transfusion rates or postoperative QOL indices despite these higher hematocrit values.

Adult↗
PubMed1991

Treatment of azotemic, nonoliguric, anemic patients with human recombinant erythropoietin raises whole-blood viscosity proportional to hematocrit.

It has been reported that patients with azotemia have reduced red blood cell (RBC) deformability. Since this is a major determinant of whole-blood viscosity (WBV) and rigid RBCs increase WBV disproportionately relative to the level of hematocrit, it is conceivable that sustained improvement of hematocrit with recombinant human erythropoietin (rhEPO) therapy in azotemic patients might result in abnormally raised WBV. To address this concern, WBV and plasma viscosity (PV) were measured in 9 adult patients (4 men, 5 women) with anemia (mean hematocrit 29.2 +/- 2.7%) and azotemia [mean serum creatinine concentration 339.85 +/- 102.44 mumol/l (3.8 +/- 1.1 mg/dl)] before and after 6 months of treatment with rhEPO (50-175 U/kg given intravenously thrice weekly). Baseline and post-treatment hematocrit, WBV and PV were compared to values derived in 50 normal adult subjects with normal renal function [25 women, 25 men; mean serum creatinine concentration 79.56 +/- 8.84 mumol/l (0.9 +/- 0.1 mg/dl), mean hematocrit 42.4 +/- 3.7%]. To compare rheologic factors at subnormal hematocrits, blood from subjects with normal renal function was diluted with autologous plasma to achieve a range of hematocrits from 20 to 50%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1975

Dynamics of glomerular ultrafiltration in the rat. VIII. Effects of hematocrit.

This study was undertaken in an effort to examine the effects of selective variations in systemic hematocrit on the preglomerular, glomerular, and postglomerular micocirculation in the rat. By isovolemic exchange transfusions, systemic hematocrit (control 51 ml/100 ml) was either reduced (21 ml/100 ml, N equal 7 rats) or elevated (62 ml/100 ml, N equal 7). Single nephron glomerular filtration rate varied inversely and filtration fraction varied directly with the changes in hematocrit. The fall in filtration fraction with decreased hematocrit was due to a decline in the measured glomerular transcapillary hydraulic pressure difference and to a marked increased in the initial glomerular plasma flow rate. Afferent (RA)and efferent (RE) arteriolar resistance declined with the fall in hematocrit; RA fell proportionately more than did RE. The rise in filtration fraction with the elevation in hematocrit was due to a marked increase in in part due to a relatively greater rise in RE than in RA. These findings provide an attractive explanation for the general tendency for filtration fraction to vary directly with hematocrit in anemic and polycythemic states in man.

Animals↗
PubMed2002

Polycystic kidney disease in patients on the renal transplant waiting list: trends in hematocrit and survival.

BACKGROUND: The patient characteristics and mortality associated with autosomal dominant polycystic kidney disease (PKD) have not been characterized for a national sample of end stage renal disease (ESRD) patients on the renal transplant waiting list. METHODS: 40,493 patients in the United States Renal Data System who were initiated on ESRD therapy between 1 April 1995 and 29 June 1999 and later enrolled on the renal transplant waiting list were analyzed in an historical cohort study of the relationship between hematocrit at the time of presentation to ESRD and survival (using Cox Regression) in patients with PKD as a cause of ESRD. RESULTS: Hematocrit levels at presentation to ESRD increased significantly over more recent years of the study. Hematocrit rose in parallel in patients with and without PKD, but patients with PKD had consistently higher hemoglobin. PKD was independently associated with higher hematocrit in multiple linear regression analysis (p < 0.0001). In logistic regression, higher hematocrit was independently associated with PKD. In Cox Regression analysis, PKD was associated with statistically significant improved survival both in comparison with diabetic (hazard ratio, 0.64, 95% CI 0.53-0.77, p < 0.001) and non-diabetic (HR 0.68, 95% CI 0.56-0.82, p = 0.001) ESRD patients, adjusted for all other factors. CONCLUSIONS: Hematocrit at presentation to ESRD was significantly higher in patients with PKD compared with patients with other causes of ESRD. The survival advantage of PKD in ESRD persisted even adjusted for differences in hematocrit and in comparison with patients on the renal transplant waiting list.

Female↗
PubMed2006

Effect on routine and special coagulation testing values of citrate anticoagulant adjustment in patients with high hematocrit values.

Recommendations to adjust citrate concentration for blood coagulation specimens with high hematocrit values are based on indirect experimental studies and not direct studies of patient samples with high hematocrit values. We compared the effect of adjusted and non-adjusted citrate concentrations on coagulation test results in samples from 28 patients with high hematocrit values (55%-72% [0.55-0.72]). Prothrombin time (PT) and activated partial thromboplastin time (aPTT) results from nonadjusted and adjusted samples were statistically different and exponentially increased with increasing hematocrit values. Results for fibrinogen, factor VIII, and protein C activity were statistically different and increased linearly with increasing hematocrit values; however, the difference was not as clinically significant. The protein C antigen value increased with increasing hematocrit values but was not significant. The effects on PT and aPTT are due to a dilutional effect of plasma and an interference effect of the higher final citrate concentration on the clotting test result. For patients with high hematocrit values, citrate concentrations must be adjusted for accurate results.

Anticoagulants↗
PubMed2000

Distinct increase in hematocrit associated with paroxysm of atrial fibrillation.

In a previous study we found that hemoconcentration, which was identified by an increase in hematocrit, occured during a paroxysm of atrial fibrillation. In the present study we investigated the changes in hematocrit from sinus rhythm to paroxysm in 10 patients who had multiple paroxysms of atrial fibrillation in order to assess the ranges of the changes in hematocrit among the paroxysms. In these patients hematocrit was measured simultaneously with electrocardiographic recording during 3 or more paroxysms and sinus rhythm just before each paroxysm. The changes in hematocrit varied among the paroxysms. The maximum increase in hematocrit in each patient ranged from 3.5 to 8.0 points with an average of 5.1 points. Such a distinct increase in hematocrit which abruptly develops with a paroxysm of atrial fibrillation may be a potential risk for thrombus formation.

Aged↗
PubMed2006

The effect of timing of cord clamping on neonatal venous hematocrit values and clinical outcome at term: a randomized, controlled trial.

BACKGROUND: The umbilical cord is usually clamped immediately after birth. There is no sound evidence to support this approach, which might deprive the newborn of some benefits such as an increase in iron storage. OBJECTIVES: We sought to determine the effect of timing of cord clamping on neonatal venous hematocrit and clinical outcome in term newborns and maternal postpartum hemorrhage. METHODS: This was a randomized, controlled trial performed in 2 obstetrical units in Argentina on neonates born at term without complications to mothers with uneventful pregnancies. After written parental consents were obtained, newborns were randomly assigned to cord clamping within the first 15 seconds (group 1), at 1 minute (group 2), or at 3 minutes (group 3) after birth. The infants' venous hematocrit value was measured 6 hours after birth. RESULTS: Two hundred seventy-six newborns were recruited. Mean venous hematocrit values at 6 hours of life were 53.5% (group 1), 57.0% (group 2), and 59.4% (group 3). Statistical analyses were performed, and results were equivalent among groups because the hematocrit increase in neonates with late clamping was within the prespecified physiologic range. The prevalence of hematocrit at <45% (anemia) was significantly lower in groups 2 and 3 than in group 1. The prevalence of hematocrit at >65% was similar in groups 1 and 2 (4.4% and 5.9%, respectively) but significantly higher in group 3 (14.1%) versus group 1 (4.4%). There were no significant differences in other neonatal outcomes and in maternal postpartum hemorrhage. CONCLUSIONS: Delayed cord clamping at birth increases neonatal mean venous hematocrit within a physiologic range. Neither significant differences nor harmful effects were observed among groups. Furthermore, this intervention seems to reduce the rate of neonatal anemia. This practice has been shown to be safe and should be implemented to increase neonatal iron storage at birth.

Adult↗
PubMed1994

The effect of increasing hematocrit on peritoneal transport kinetics.

Although it is well established that an increase in hematocrit results in a small decrease in solute transport in hemodialysis patients, the effect of hematocrit on solute transport in peritoneal dialysis patients remains controversial. In hemodialysis patients, the inverse relationship between hematocrit and the transport of small solutes may be explained by the dependence of solute clearance on the rapidity of solute movement from the red blood cell to the dialysate. This movement is determined by several in vivo factors, the most important of which is blood flow. However, in peritoneal dialysis, the effective peritoneal capillary blood flow is several times the maximal urea clearance. Therefore, clearances are usually considered to be independent of blood flow rate and variations in hematocrit should not affect solute transport across the peritoneal membrane. In this study, the effect of an increase in hematocrit on the transport of small solutes in peritoneal dialysis patients is analyzed. The peritoneal equilibration test was performed in 25 continuous ambulatory peritoneal dialysis patients before and after an increase in hematocrit of at least seven points. No significant change was found in ultrafiltration rate or in peritoneal transport characteristics as measured by the peritoneal equilibration test or by mass transfer area coefficients for creatinine, urea, or glucose. In addition, there was no change in these parameters in a control group of 13 continuous ambulatory peritoneal dialysis patients with no significant change in hematocrit. These findings are consistent with the observation that solute clearance for urea and creatinine in peritoneal dialysis is not blood flow dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗