The role of plasma volume and fluid overload in the tolerance to ultrafiltration and hypotension in hemodialysis patients

IntroductionUltrafiltration (UF) in hemodialysis (HD) patients is accompanied by irregular falls in plasma volume (PV) and blood pressure (BP).MethodsWe obtained in 321 patients (large cohort), body weight (BW), BP, samples of blood to determine hemoglobin (Hb) and hematocrit (Ht), Pre and Post HD. We estimated the % variation of the PV and its effect on the BP. In a small cohort of 38/321 patients, arterial blood was drawn Pre and Post HD and at 2, 48, and 72 h to determined Hb and Ht and % variation of the PV. Bio-impedance spectroscopy (BIS) was performed, in the same times, to estimate: dry weight (DW), total body water (TBW), extracellular water (ECW), Fluid overload (FO) and phase angle (PhA).ResultsWe divided our large cohort in two groups. The Hypotensive group with a fall equal or more than 20 mmHg (96/321,30%) and Normotensive group with a drop equal or less than 19 mmHg (225/321,70%). The UF was 2.73 ± 0.72 L in the Hypotensive group and 2.53 ± 0.85 L in the Normotensive group (p < 0.0001). The % PV was −11.7 ± 17.8 in the Hypotensive group and −8.53 ± 10.07 in the Normotensive group (p < 0.0001). The systolic blood pressure (SBP) correlated with the % change of the PV (r = -0.232; p < 0.0001). The FO was contrasted with the % of water removed by UF (r = -0.890; p < 0.0001).ConclusionThe SBP drop was secondary to the fall in the PV after UF. The FO was irregular and modulates in part the fall in the SBP.     

Characteristics of hypotension-prone haemodialysis patients: is there a critical relative blood volume?

BACKGROUND: Intradialytic morbid events (IME, mostly hypotension) mainly due to ultrafiltration-induced hypovolaemia still are the most frequent complication during haemodialysis (HD). This study was performed to test the hypothesis that there is an individual critical relative blood volume (RBV(crit)) in IME-prone HD patients. METHODS: In this prospective international multicentre study, 60 IME-prone patients from nine dialysis centres were observed during up to 21 standard HD sessions without trial-specific intervention. The RBV was monitored continuously by an ultrasonic method (BVM; blood volume monitor). Also, the ultrafiltration rate was registered continuously. Blood pressure was measured at regular intervals, and more frequently during IME. All IME and specific therapeutic interventions were noted. RESULTS: In total, 537 IME, some with more than one symptom, were documented during 585 HD sessions. The occurrence of IME increased up to 10-fold from the start to the end of the HD session. RBV(crit) showed a wide inter-individual range, varying from 71 to 98%. However, the intra-individual RBV limit was relatively stable, with an SD of <5% in three-quarters of the patients. In patients with congestive heart failure, cardiac arrhythmia, advanced age, low ultrafiltration volume and low diastolic blood pressure, higher values of RBV(crit) were observed. While all correlations between RBV(crit) and patient characteristics alone were found to be of weak or medium strength, the combination of diastolic blood pressure, ultrafiltration volume and age resulted in a strong correlation with RBV(crit): the linear equation with these parameters allows an estimation of RBV(crit) in patients not yet monitored with a BVM. CONCLUSIONS: An individual RBV limit exists for nearly all patients. In most IME-prone patients, these RBV values were stable with only narrow variability, thus making it a useful indicator to mark the individual window of haemodynamic instabilities.     

Intra-dialytic hypotension and blood volume and blood temperature monitoring

Intra-dialytic hypotension (IDH) is a common problem affecting haemodialysis patients. Its aetiology is complex and influenced by multiple patient and dialysis factors. IDH occurs when the normal cardiovascular response cannot compensate for volume loss associated with ultrafiltration, and is exacerbated by a myriad of factors including intra-dialytic fluid gains, cardiovascular disease, antihypertensive medications and the physiological demands placed on patients by conventional haemodialysis. The use of blood volume monitoring and blood temperature monitoring technologies is advocated as a tool to predict and therefore prevent episodes of IDH. We review the clinical utility of these technologies and summarize the current evidence of their effect on reducing the incidence of IDH in haemodialysis population.     

Efficacy and safety of haemodialysis treatment with the Hemocontrol biofeedback system: a prospective medium-term study.

BACKGROUND: Hypovolaemia has been implicated as a major causal factor of morbidity during haemodialysis (HD). A model biofeedback control system for intra-HD blood volume (BV) changes modelling has been developed (Hemocontrol), Hospal Italy) to prevent destabilizing hypovolaemia. It is based on an adaptive controller incorporated in a HD machine (Integra), Hospal Italy). The Hemocontrol biofeedback system (HBS) monitors BV contraction during HD with an optical device. HBS modulates BV contraction rates by adjusting the ultrafiltration rate (UFR) and the refilling rate by adjusting dialysate conductivity (DC) in order to obtain the desired pre-determined BV trajectories. METHODS: Nineteen hypotension-prone uraemic patients (seven males, 12 females; mean age 64.5+/-3.0 SEM years; on maintenance HD for 80.5+/-13.2 months) volunteered for the present prospective study that compared the efficacy and safety of bicarbonate HD treatment equipped with HBS, as a whole, with the gold-standard bicarbonate treatment equipped with a constant UFR and DC (BD). The study included three phases: Medium-term studies started with one period of 6 months of BD and always had a follow-up period of HBS treatment ranging from 14 to 30 months (mean 24.0+/-1.6); short-term studies started in September 1999, when all patients went back to BD treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase A). Afterwards, they once again started HBS treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase B). Every patient underwent acute studies during a single HD run, once during phase A and once in phase B. Resistance (R) and reactance (Xc) measurements were obtained utilizing a single-frequency (50 kHz) tetrapolar bioimpedance analysis (BIA). Extracellular fluid volume (ECV) was calculated from R, Xc, and height and body weight measurements using the conventional BIA regression equations. RESULTS: The overall occurrence of symptomatic hypotension and muscle cramps was significantly less in HBS treatment in both medium- and short-term studies. Self-evaluation of intra- and inter-HD symptoms (worst score=0, best score=10) revealed a statistically significant difference, as far as post-HD asthenia was concerned (6.2+/-0.2 in HBS treatment vs 4.3+/-0.1 in BD treatment, P<0.0001). No difference was observed between the two treatments when comparing pre- and post-HD lying blood pressure, heart rate, body weights and body weight changes in medium- and short-term studies. The residual BV%/ Delta ECV% ratio, expression of the vascular refilling, was significantly higher during HBS treatment in acute studies. CONCLUSIONS: HBS treatment is effective in lowering hypovolaemia-associated morbidity compared with BD treatment; this could be related to a greater ECV stability. Furthermore, HBS is a safe treatment in the medium-term because these results are not achieved through potentially harmful changes in blood pressure, body weight, and serum sodium concentration.     

Variability of relative blood volume during haemodialysis.

BACKGROUND: A decrease in blood volume is thought to play a role in dialysis-related hypotension. Changes in relative blood volume (RBV) can be assessed by means of continuous haematocrit measurement. We studied the variability of RBV changes, and the relation between RBV and ultrafiltration volume (UV), blood pressure, heart rate, and inferior caval vein (ICV) diameter. METHODS: In 10 patients on chronic haemodialysis, RBV measurement was performed during a total of one hundred 4-h haemodialysis sessions. Blood pressure and heart rate were measured at 5-min intervals. ICV diameter was assessed at the start and at the end of dialysis using ultrasonography. RESULTS: The changes in RBV showed considerable inter-individual variability. The average change in RBV ranged from -0.5 to -8.2% at 60 min and from -3.7 to -14.5% at 240 min (coefficient of variation (CV) 0.66 and 0.35 respectively). Intra-individual variability was also high (CV at 60 min 0.93; CV at 240 min 0.33). Inter-individual as well as intra-individual variability showed only minor improvement when RBV was corrected for UV. We found a significant correlation between RBV and UV at 60 (r= -0.69; P<0.001) and at 240 min (r= -0.63; P<0.001). There was a significant correlation between RBV and heart rate (r= -0.39; P<0.001), but not between RBV or UV and blood pressure. The level of RBV reduction at which hypotension occurred was also highly variable. ICV diameter decreased from 10.3+/-1.7 mm/m(2) to 7.3+/-1. 5 mm/m(2). There was only a slight, although significant, correlation between ICV diameter and RBV (r= -0.23; P<0.05). The change in ICV-diameter showed a wide variation. CONCLUSIONS: RBV changes during haemodialysis showed a considerable intra- and inter-individual variability that could not be explained by differences in UV. No correlation was observed between UV or changes in RBV and either blood pressure or the incidence of hypotension. Heart rate, however, was significantly correlated with RBV. Moreover, IVC diameter was only poorly correlated with RBV, suggesting a redistribution of blood towards the central venous compartment. These data indicate that RBV monitoring is of limited use in the prevention of dialysis-related hypotension, and that the critical level of reduction in RBV at which hypotension occurs depends on cardiovascular defence mechanisms such as sympathetic drive.     

Expressing glomerular filtration rate in terms of extracellular fluid volume.

Glomerular filtration rate (GFR) is routinely calculated from the second exponential of the bi-exponential plasma clearance of filtration markers such as Cr-51 EDTA and Tc-99m DTPA. By ignoring the first exponential, true GFR is overestimated, an error which increases with increasing GFR. The rate constant, lambda 2, of the second exponential represents the rate at which glomerular filtration 'turns over' the extracellular fluid (ECF) and so closely approximates GFR/ECF volume. Again, the error in the estimation of this ratio increases with increasing GFR, although in this case it underestimates the true ratio. Expressing GFR in terms of ECF volume, rather than in terms of body surface area, offers considerable technical and physiological advantages. The relationship between GFR/ECF volume and lambda 2, over a wide range of renal function, expressed as a second order polynomial, was GFR/ECF volume = -0.093 + 1.06 lambda 2 + 0.009 lambda 2(2) ml.min-1.l-1. The corresponding relationship between 'true' GFR (C1) and approximate GFR (i.e. based only on the second exponential--C2) was C1 = -0.58 + 1.012C2 -0.0011 C2(2) ml.min-1 For any level of renal function, the error in GFR/ECF volume, expressed as lambda 2, is less than the error in GFR expressed as C2. Since GFR may change as a direct result of a change in ECF volume, it is physiologically more relevant, and technically very much easier, to express GFR in terms of ECF volume rather than body surface area.     

Norepinephrine-induced vasoconstriction results in decreased blood volume in dialysis patients.

BACKGROUND: Hypotension during haemodialysis results from an inadequate cardiovascular response to ultrafiltration-induced hypovolaemia. It has been suggested that plasma volume could be increased as a result of systemic vasoconstriction. METHODS: We studied the effect of a norepinephrine (NOR) infusion (30 min), compared with no infusion, on relative blood volume (RBV) in six haemodialysis patients. During infusion we measured RBV, systolic blood pressure (SAP), heart rate (HR), stroke volume index (SI), total peripheral resistance (TPRI), ejection fraction (EF), inferior vena cava diameter (VCD) and core temperature. RESULTS: At the end of the NOR infusion, we observed a significant increase in TPRI (47+/-47% vs 4+/-17%; P<0.01) and SAP (27+/-12% vs 0+/-8%; P<0.01). Norepinephrine-induced vasoconstriction resulted in a significant decrease in RBV (-9+/-3% vs 0+/-1%; P<0.01). No significant changes were seen in SI (-4+/-21% vs 0+/-8%), HR (-5+/-19% vs -4+/-5%), EF (7+/-14% vs -2+/-10%), VCD or temperature. CONCLUSIONS: We conclude that norepinephrine-induced vasoconstriction results in a decrease in RBV. This indicates that improved haemodynamic stability during haemodialysis through vasoconstriction can be accompanied by a decrease in RBV and that part of the variability in blood volume may be due to changes in arterial tone. Such changes must be taken into account if RBV measurements are used to improve the haemodynamic tolerance of dialysis.     

Inter-dialytic variations in blood volume and total body water in uraemic patients treated by dialysis.

BACKGROUND: An optimal balance of sodium and water is one of the most important goals of haemodialysis (HD) therapy. However, while inter-dialytic variations in blood volume (BV) have been well described, very little is known about the dynamics of fluid accumulation and distribution in body compartments during the inter-dialysis period. METHODS: We studied inter-dialysis variations in BV, measured as percent variation of plasma haemoglobin (Hb) concentrations (% triangle up BV) and percent variation of total body water (% triangle up TBW), in 24 uraemic patients treated by standard bicarbonate dialysis. These parameters were determined at the end of the last weekly dialysis (T0), after 24 h (T1), 48 h (T2), and at the beginning of the following dialysis session (T3). At each time point we measured Hb, haematocrit (Hct), serum albumin (sAlb), plasma sodium (Na), plasma potassium (K), blood urea nitrogen (BUN), plasma osmolality (Osm), body weight (BW), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). All patients were clinically stable and had no evidence of acute blood loss in the 3 weeks before the study. RESULTS: During the inter-dialysis period, there were increases in BUN, K and Osm, but Na did not change. SBP and DBP also did not change. HR tended to decrease, and showed a significant reduction between T0 and T3. TBW increased in a linear fashion whereas BV increased exponentially, showing a slow rise during the first 24 h followed by a greater increase in the following time intervals. This was confirmed by concomitant but opposite percent variations in Hct and sAlb concentrations. CONCLUSIONS: Despite the limitations of the current methodology, our data show that the increase in TBW is redistributed during the long inter-dialysis period and this may prevent the effects of a too premature expansion of the intra-vascular compartment. This is especially evident during the first 24 h after HD, during which % triangle up BV is lowest, indicating a preferential distribution of the fluid load towards the extra-vascular space. During the following time intervals, the extra-vascular compartment refills in conjunction with an exponential expansion of BV that reaches its maximum in the last 24 h before HD.     

Effects of hypertonic saline (7.5%) on extracellular fluid volumes in healthy volunteers

This study evaluated the effects of 7.5% saline on plasma and other extracellular fluid volumes. After baseline measurements, eight healthy postmenopausal female volunteers received 4 ml.kg-1 of hypertonic saline over 30 min. After the fluid infusion, the volunteers were studied for 60 min. Plasma volume was measured using a dilution of 125-iodine-labelled human albumin. Extracellular water and cardiac output were measured by whole body impedence cardiography. The infused volume was 4 ml.kg-1 (average 260 ml). Plasma volume increased rapidly during the infusion (mean +/- standard deviation, 442 +/- 167 ml). At the end of the 1-h follow-up period, plasma volume had increased by on average 465 ml (SD 83). The increase of extracellular water at the end of infusion and at the end of study was 650 ml (SD 93) and 637 ml (SD 192), respectively. The highest serum sodium recorded in the volunteers was 158 mmol.l-1. The effect of 7.5% saline on plasma volume was rapid and lasted for at least 1 h. Plasma volume remained elevated by more than the infused volume at the end of the study. The increase in plasma and extracellular fluid volumes was partly achieved by mobilizing intracellular water to extracellular compartment.     

Effects of repeated injections of human chorionic gonadotrophin on vascular permeability, extracellular fluid volume and the flow of lymph in the testes of rats

Testicular lymph flow, interstitial fluid volume and vascular permeability have been measured in adult male rats injected subcutaneously with hCG daily for up to 4 consecutive days. Albumin clearance was also measured in rats given two or three hCG injections at 2- or 3-day intervals, or every 2 days for 22 days. While a single dose of hCG increased vascular permeability and lymph flow within 24 h, subsequent daily injections did not produce any additional response and, in fact, values returned towards control levels. A second hCG dose 2 days after an initial dose did produce another similar increase in the clearance of albumin injected directly into the testis and, with continued injections every second day, a response was still evident after 22 days. The response to the second dose of hCG occurred at a time when down-regulation of hCG receptors on Leydig cells is reported to be maximal. These results suggest that in the testis, the vascular response to hCG does not require the normal number of luteinizing hormone (LH) receptors, although other evidence suggests that Leydig cells must somehow be involved.     

Haemoglobin dilution from epidural-induced hypotension with and without fluid loading

The blood haemoglobin concentration (B-Hb) was measured repeatedly to reflect dilution or concentration changes of the blood during onset of lumbar epidural anaesthesia in 90 elderly men. With crystalloid volume loading (10 ml.kg-1 b.w.), the decrease in B-Hb was twice as great for those who developed hypotension during the onset of the blockade as for patients whose arterial pressure remained normal (P less than 0.001), both when epidural anaesthesia was induced with plain mepivacaine, and when mepivacaine plus adrenaline was used. In a control group where no fluid loading was performed, there was no consistent change in the haemoglobin level, irrespective of blood pressure reaction to the blockade. The results suggest that crystalloid fluid loading allows an increase in blood volume in epidural-induced hypotension.     

Relationship between blood pressure during haemodialysis and ambulatory blood pressure in between dialyses

BACKGROUND.: Ambulatory blood pressure measurements in haemodialysis patientsare relevant in view of the high cardiovascular morbidity andmortality in chronic haemodialysis patients. METHODS.: Twelve normotensive patients were studied from the beginningof one dialysis until the end of the next (mean 64 h, SD 19h) using a Spacelabs oscillometric blood-pressure recorder. RESULTS.: A circadian blood pressure rhythm was present in six of the12 patients. In seven patients the lowest pressure recorded(including the dialysis sessions) occurred 5–6 h afterdialysis (late post-dialysis dip). Blood pressure did not increasesharply in the hours before dialysis although it increased slightlyin the interdialytic interval as a whole, at a mean rate of5.6 mmHg per 24 h (SD 4.1, P<0.001). We could not find ablood pressure measurement during dialysis (or combination ofmeasurements) which reliably reflects interdialytic blood pressure:the 95% confidence intervals were 25 mmHg or higher. CONCLUSION.: Ambulatory blood pressure measurements are needed for adequatemonitoring of the control of blood pressure in haemodialysispatients.     

Comparison of volume of blood processed on haemodialysis adequacy measurement sessions vs regular non-adequacy sessions.

BACKGROUND: Knowledge that adequacy measures such as the urea reduction ratio (URR) or Kt/V(urea) are being measured on haemodialysis may influence the behaviour of patients or staff such that the treatment may be better on those days. This study therefore tested the hypothesis that mean volume of blood processed (VBP), utilized as a surrogate for adequacy, is higher on adequacy measurement days than non-measurement days. METHODS: Patients were identified who had been on haemodialysis over the preceding 8 months. Primary outcome was the difference in the mean VBP (in litres) on URR measurement compared with non-URR measurement days (DeltaVBP(U)(-N)). Univariate and multivariate correlates of mean VBP and DeltaVBP(U)(-N) were also determined. RESULTS: Eighty-nine patients were identified who met inclusion and exclusion criteria. Linear regression demonstrated a weak relationship between VBP and URR (r=0.24, P<0.02). This relationship was much stronger when VBP was adjusted for patient weight (mean VBP/weight; r=0.78, P<0.0001). The overall mean VBP was 87.4 l (+/-1.2 l) and the average DeltaVBP(U)(-N) was 1.1 l (+/-0.3 l) (P=0.001). Twenty per cent of patients had a clinically relevant DeltaVBP(U)(-N) of >3.6 l. Patients with a graft or fistula had a significantly higher DeltaVBP(U)(-N) than patients with a tunnelled catheter. CONCLUSIONS: This study demonstrates that the average VBP is less on non-URR than on URR measurement days; this difference was clinically important in >20% of patients. Univariate analysis indicated that the use of a fistula or graft correlated with a higher DeltaVBP(U)(-N). This implies that our current method of assessing dialysis adequacy does systematically overestimate the average delivered dose of dialysis in a subset of patients.     

The impact of fluid optimisation before induction of anaesthesia on hypotension after induction

Intra-operative hypotension is a known predictor of adverse events and poor outcomes following major surgery. Hypotension often occurs on induction of anaesthesia, typically attributed to hypovolaemia and the haemodynamic effects of anaesthetic agents. We assessed the efficacy of fluid optimisation for reducing the incidence of hypotension on induction of anaesthesia. This prospective trial enrolled 283 patients undergoing radical cystectomy and randomly allocated them to goal-directed fluid therapy (n = 142) or standard fluid therapy (n = 141). Goal-directed fluid therapy patients received fluid optimisation based on stroke volume response to passive leg raise before induction; those with positive passive leg raise received intravenous crystalloid fluid boluses until stroke volume was optimised. Baseline mean arterial pressure was measured on the morning of surgery and on arriving in the operating theatre. This post-hoc analysis defined haemodynamic instability as either a > 30% relative drop in mean arterial pressure compared with baseline or absolute mean arterial pressure < 55 mmHg, within 15 min of induction. Forty-two (30%) goal-directed fluid therapy patients underwent fluid optimisation after finding an intravascular fluid deficit via passive leg raise testing; 106 (75%) goal-directed fluid therapy and 112 (79%) standard fluid therapy patients met criteria for haemodynamic instability. There was no significant difference in the incidence of haemodynamic instability between the goal-directed fluid therapy and standard fluid therapy groups using absolute mean arterial pressure drop below 55 mmHg (p = 0.58) or using pre-surgical testing or pre-surgical mean arterial pressure values as baseline (p = 0.21, p = 0.89, respectively); however, the difference in the incidence of haemodynamic instability was significant using the operating theatre baseline mean arterial pressure (p = 0.004). We conclude that fluid optimisation before induction of general anaesthesia did not significantly impact haemodynamic instability.     

Influence of intraoperative fluid volume on cardiopulmonary bypass hematocrit and blood transfusions in coronary artery bypass surgery

A hematocrit (Hct) of less than 25% during cardiopulmonary bypass (CPB) and transfusion of homologous packed red blood cells (PRBC) are each associated with an increased probability of adverse events in cardiac surgery. Although the CPB circuit is a major contributor to hemodilution intravenous (IV) fluid volume may also significantly influence the level of hemodilution. The objective of this study was to explore the influence of asanguinous IV fluid volume on CPB Hct and intraoperative PRBC transfusion. After Institutional Review Board approval, a retrospective chart review of 90 adult patients that had undergone an elective, isolated CABG with CPB was conducted. Regression analysis was used to determine if pre-CPB fluid volume was associated with the lowest CPB Hct and the incidence of an intraoperative PRBC transfusion. In separate multivariate analyses, higher pre-CPB fluid volume was associated with lower minimum CPB Hct (p < .0001), and higher minimum CPB Hct was associated with a decreased probability of PRBC transfusion (p < .0001). Compared to patients that received <1600 mL (n = 55) of pre-CPB fluid, those that received >1600 mL (n = 35) had a decreased mean low CPB Hct (22.4% vs 25.6%, p < .0001), an increased incidence of a CPB Hct <25% (74% vs. 38%, p = .0008) and PRBC transfusion (60% vs. 16%, p < .0001), and increased median PRBC units transfused (2.0 vs 1.0, p = .1446) despite no significant difference in gender, age, patient size, baseline Hct, or CPB prime volume. Patients that received a PRBC transfusion (n = 30) received a significantly higher volume of pre-CPB fluid than nontransfused patients (1800 vs. 1350 mL, p = .0039). These findings suggest that pre-CPB fluid volume can significantly contribute to hemodilutional anemia in cardiac surgery. Optimizing pre-CPB volume may preserve baseline Hct and help limit intraoperative hemodilution.     

Reduction of hypotensive side effects during online-haemodiafiltration and low temperature haemodialysis.

BACKGROUND: This study compares the effect of online-haemodiafiltration (o-HDF, post-dilution mode) with conventional haemodialysis (HD) and 'temperature-controlled' HD (Temp-HD) on the haemodynamic stability of hypotension-prone patients. METHODS: Seventeen patients with a history of frequent hypotensive episodes during dialysis sessions were studied, each patient serving as his or her own control. The first 25 HD treatments in comparison with 25 o-HDF sessions were evaluated using identical dialysate temperature. In the second part of the study, o-HDF (n = 25) was compared with Temp-HD (n = 25). In the latter method, the temperature of the dialysate was adjusted to result in identical energy transfer rates to those in the corresponding o-HDF. The number of hypotensive episodes, blood temperature and blood volume regulation were assessed. RESULTS: Symptomatic hypotension was much more frequent during HD (40%) than during o-HDF (4%) (P < 0.001). During o-HDF, an enhanced energy loss within the extracorporeal system occurred (o-HDF, 16.6 +/- 4.0 W; HD, 5.4 +/- 5.1 W; P < 0.0001), despite identical temperature settings for dialysate and substitution fluid. As a result, the blood returning to the patient was cooler during o-HDF than during HD (o-HDF 35 +/- 0.2 degrees C vs HD 36.5 +/- 0.3 degrees C; P < 0.0001). In o-HDF, even in the patients' circulation, the mean blood temperature was lower (o-HDF 36.7 +/- 0.2 degrees C vs HD 36.9 +/- 0.3 degrees C; P < 0.0001) and blood volume was significantly more reduced (o-HDF, 91.8 +/- 3.1%; HD, 94.0 +/- 3.2%; P < 0.05). Energy transfer rates and blood temperature did not differ significantly between o-HDF and Temp-HD. The rate of hypotensive episodes was low and not different between o-HDF (4%) and Temp-HD (4%). Neither was there any significant difference in blood volume reduction. CONCLUSIONS: O-HDF showed a significant reduction of hypotensive episodes compared with HD. Surprisingly, o-HDF resulted in cooling of the blood via enhanced thermal energy losses within the extracorporeal system, despite use of replacement fluid prepared from pre-warmed dialysate. The incidence of symptomatic hypotension was reduced to that of o-HDF by using cooler Temp-HD. Thus, unexpected blood cooling appears to be the main blood pressure-stabilizing factor in o-HDF.     

基于CT细胞外体积分数用于腹部疾病进展

细胞外基质(ECM)参与细胞生长、分化、迁移和代谢活动,与肿瘤等疾病发生发展相关。基于影像学技术获得的细胞外体积分数(ECV)可量化评价ECM,进而评估病变。本文就基于CT的ECV用于腹部疾病进展进行综述。