Changes in Vascular Tone Occur Early During Hemodialysis Treatments Independently of Volume Reduction

Hypotension commonly occurs during hemodialysis (HD). Hypotension can result from an absolute reduction in plasma volume following excessive ultrafiltration or from a reduction in vascular tone. We hypothesized that changes in vascular tone could occur during dialysis. Aortic pulse wave velocity (aPWV) was measured in 197 HD patients, mean age 63.3 ± 16.6 years, 62% male, 49% diabetic, during a single HD session. aPWV did not change (9.6 ± 2.2 vs. 9.6 ± 2.2 m/s) with HD. Systolic blood pressure (SBP) declined from 151 ± 31 to 147 ± 32 after 20 min and to 140 ± 36 mm Hg on completion of HD (P < 0.05), with an ultrafiltration volume of 2.2 ± 0.9 L over a 3.9 ± 0.4 h HD session. Aortic SBP declined from 154 ± 32 to 146 ± 29 after 20 min and 143 ± 35 at the end of HD, P < 0.001. Aortic augmentation index (Aortic Aix) decreased from 65% (52–79%) to 36.7% (23.3–52.9%) by 20 min and to 34.3 (15.1–49.1%) on completion of HD (P < 0.05), and brachial augmentation index (brachial Aix) from 5.7% (?25.2 to 27.5%) to ?1.9% (?2.2 to 30.1%) and ?6.6% (?44 to 22.7%), respectively, P < 0.05. Diastolic reflection area (DRA) increased from 36.7 (27.9–46.3) to 40.4 (32.2–51) after 20 min and 47.1 (34.2–60.5) on completion of HD, P < 0.05. We report changes in arterial tone within 20 min of starting HD, when minimal ultrafiltration has occurred, suggesting that volume changes may not be the only predisposing cause of intradialytic hypotension. The combination of a fall in SBP and a rise in DRA would suggest a reduction in coronary blood flow in keeping with reports of “myocardial stunning” during HD.     

WARNING OF HIGH-FLUX HEMODIALYSIS

In order to estimate the influence of flux on plasma refilling during hemodialysis (HD), prospective crossover studies were performed in 10 HD patients with low-flux and high-flux dialyzers. Hematocrit was continuously monitored to assess changes in blood volume. In addition, plasma osmolarity and total protein concentration were measured. Intradialytic reductions in body weight (?5 ± 1 vs ?5 ± 1%) and plasma osmolarity (?5 ± 1 vs ?5 ± 1%) were similar in both conditions. Although mean blood pressure remained unchanged in either state, the decrease in blood volume was larger in high-flux HD (?13 ± 2 vs ?10 ± 2%, p < 0.05). In spite of greater contraction in blood volume during high-flux HD, total proteins were increased equally between low-flux and high-flux HD (11 ± 4 vs 11 ± 4%). Our data that although high-flux HD failed to induce significant drops in blood pressure, it elicited greater magnitude of decreases in blood volume, implicate the judicious application of high-flux HD.     

Characteristics of bioimpedance-determined fluid shifts according to intradialytic blood pressure difference

This study was designed to identify the fluid spaces that are most changed during ultrafiltration (UF) according to intradialytic blood pressure (BP) difference. BP data were collected five times (before hemodialysis [HD] and 1–4 h of HD). Intradialytic BP difference was calculated as the highest minus lowest of these BP measurements. Intradialytic systolic BP (SBP) difference over 20 mm Hg and diastolic BP (DBP) difference over 10 mm Hg were defined as wide intradialytic SBP difference (SYS-W) and DBP difference (DIA-W), respectively. We measured the various fluid spaces before HD and 1–4 h of HD, and 30 min after HD using a portable, whole-body bioimpedance spectroscopy (BIS). In this study, 85 prevalent patients aged over 18 years with a fixed dry weight (65.38 ± 12.45 years, 54.18% men, 52.50% patients with diabetes), undergoing HD had participated. 1) Mean relative reduction of extracellular water (ECW) was significantly higher in SYS-W than in narrow intradialytic SBP difference (SYS-N) patients from 1 h to 30 min after HD. 2) Mean relative reduction of intracellular water (ICW) was significantly lower in DIA-W than in narrow intradialytic DBP difference (DIA-N) patients from 1 h to 30 min after HD. 3) ECW of patients with SYS-W was significantly lower than that of patients with SYS-N. Patients with SYS-W have the characteristics of fluid shifts in which reduction of ECW was steeper than patients with SYS-N whereas fluid shifts of ICW were lower in patients with DIA-W than patients with DIA-N.     

Serum chromogranin A concentration and intradialytic hypotension in chronic haemodialysis patients

Aim The aim of this study was to investigate the influence of haemodialysis on plasma chromogranin A (CgA) concentration and to assess the relationship between CgA, blood pressure, occurrence of intradialytic hypotension episodes and residual renal function, respectively. Methods The study included 38 chronic haemodialysis patients (24 M, 14 F; mean age 56.2 ± 13.6 years). Plasma CgA and blood pressure were measured before and after a mid-week dialysis. Control group included 10 age- and sex-matched healthy subjects. Results Plasma CgA levels were on average 50-fold higher in HD patients than in the controls (699 ± 138 vs. 14 ± 6 U/L). In HD patients plasma CgA corrected for ultrafiltration rates significantly increased (to 836 ± 214 U/L, P < 0.001) at the end of dialysis procedure. In patients with (n = 8) and without frequent symptomatic intradialytic hypotension episodes predialysis values of CgA were similar (701 ± 169 vs. 698 ± 132 U/L) but post-dialysis were significantly lower in the former group (746 ± 312 vs. 860 ± 177 U/L; P = 0.03) despite a similar rate of ultrafiltration (2675 ± 1009 and 2583 ± 1311 ml, respectively). Accordingly, in patients with intradialytic hypotension an increase of plasma CgA during dialysis was also much lower than in patients without hypotension (45 ± 81 vs. 163 ± 144 U/L; P = 0.001). Conclusions CgA undergoes marked accumulation in renal failure. The increase of plasma CgA during dialysis is impaired in subjects with intradialytic hypotension episodes, which confirms the role of autonomic dysfunction in the pathogenesis of this complication.     

The Effect of the Type of Membrane on Intradialytic Complications and Mortality in Crush Syndrome

Aims. There are not enough data about the type of the membrane that should be used in acute intermittent hemodialysis (IHD) in patients with crush syndrome where intradialytic complication rate is high. The effects of dialyzers on outcome have been investigated in this study.?Methods. Patients who required IHD due to crush syndrome after a big earthquake that struck Marmara in 1999 have been studied. Hemodynamic and biochemical analyses at the time of admission were examined. The patients were divided into three groups according to the type of dialyzers (viz., hemophan, polysulfone, and combined).?Results. Forty-five patients were included in the study (mean age: 33.9 ± 13.3 years, mean HD session per patient: 8.8 ± 6.1). In all, 408 dialyzers were used during IHD therapy (21% hemophan). The types of dialyzers used were hemophan (8 patients), polysulfone (18 patients), and the combination of the two (19 patients). The demographic and biochemical parameters related to crush syndrome were not different statistically. All sessions were anticoagulant-free. Hypotension and coagulation of sets were the main intradialytic complications. Five (11%) patients died, but there was no correlation between mortality rates and the type of the dialyzer used. Serum albumin, blood pressure, and thrombocyte counts were found to be related to mortality.?Conclusion. No effect of the type of dialysis membrane on outcome was detected in patients with crush syndrome. Other potential factors, which may responsible for the complications and mortality, should be investigated.     

Treatment of post-dialytic orthostatic hypotension with an inflatable abdominal band in hemodialysis patients

The purpose of this study was to ascertain whether abdominal compression with an inflatable abdominal band, a device we developed, improved post-dialytic orthostatic hypotension (OH) in hemodialysis (HD) patients. Twenty-five chronic HD patients with intractable post-dialytic OH were recruited. Post-HD changes in systolic blood pressure (DeltaSBP) in the supine and standing positions were compared in the patients, measured with or without the use of the band. The study showed DeltaSBP after HD without the band was significantly greater than that measured before HD (-36.1+/-18.2 vs -13.1+/-16.8 mm Hg; P<0.0001). DeltaSBP after HD with the band was reduced significantly in comparison to DeltaSBP after HD without the band (-19.4+/-21.2 vs -36.1+/-18.2 mm Hg; P<0.002). Use of the band did not cause an elevation in SBP in the supine position (149.0+/-29.6 vs 155.4+/-25.7 mm Hg); however, it did increase SBP upon standing (129.6+/-27.3 vs 117.2+/-22.6 mm Hg; P<0.05). Eight patients in whom an increase in SBP of 25 mm Hg or more was achieved with the band were classified as responders. Ejection fraction was significantly higher (76.4+/-11.1 vs 61.9+/-13.6%; P<0.02) and atrial natriuretic peptide concentration significantly lower (27.9+/-22.0 vs 68.9+/-47.5 pg/ml; P<0.02) in responders than in non-responders. We conclude that the abdominal band was effective for overcoming post-dialytic OH, without elevating supine SBP in some patients.     

Effect of Exercise Training on Interdialytic Ambulatory and Treatment‐Related Blood Pressure in Hemodialysis Patients

Background: Exercise training improves blood pressure (BP) in the general population, but prior studies in hemodialysis (HD) patients only used pill counts or treatment‐related BPs. We evaluated the effect of 3 to 6 months of intradialytic exercise training on ambulatory blood pressure (ABP) and treatment‐related pre‐ and postdialysis BP. Patients and Methods: Nineteen chronic HD patients trained with an exercise bicycle for 30 to 60 min in the first 1 to 2 hr of each of thrice weekly HD. Interdialytic 44‐hr ABP was performed a week before training began and repeated at 3 and 6 months. Pre‐ and post‐HD systolic and diastolic BP and pre‐ and post‐HD weight were recorded for 2 months prior to training, throughout the training, and, if available, for the 2 months after training ended. BP medications were recorded throughout. Body composition by bioimpedance, and norepinephrine and epinephrine levels by RIA were done at 0, 3, and 6 months. Results: Thirteen subjects who completed at least 3 months of training exercised 90% of HD sessions for 56 min ± 23 SD each. Systolic and diastolic 44‐hr interdialytic ABP fell during training (systolic 138.4 mmHg ± 19.6 vs. 125.7 mmHg ± 20.0 vs. 125.9 mmHg ± 22.9; diastolic 83.2 mmHg ± 10.2 vs. 74.7 mmHg ± 9.0 vs. 73.9 mmHg ± 11.8 at 0, 3, and 6 months; p < .05 ANOVA). Norepinephrine and epinephrine levels did not independently predict systolic BP. Pre‐HD systolic BP was stable during the pretraining period, fell significantly during the training period (p < .03), and returned toward preexercise levels during the posttraining period (p < .001). Pre‐ or postweight, erythropoietin dose, total body water, and number of BP meds were unchanged. Conclusion: Exercise training during HD significantly improves both interdialytic ABP and treatment‐related BP.     

Variations in Aortic Pressure Affect the Mechanics of the Intra‐Aortic Balloon: An In Vitro Investigation

This study aims to investigate the mechanics of the intra‐aortic balloon (IAB) under different aortic pressure (P_ao) and inclination (0–75°). Pressure and flow were measured in an artificial aorta during IAB pumping with a frequency of 1:3. Volume displaced toward the “coronary arteries” during inflation (V_prox) and “intra‐aortic” pressure reduction during deflation (P_r) were derived. IAB duration of inflation and deflation was determined with a high‐speed camera visualization. When the aorta was horizontal, P_ao raised from 45 mm Hg to 115 mm Hg, V_prox reduced by 18% (25.0 ± 1.0 mL vs. 30.4 ± 1.9 mL) and P_r increased by 117% (106.4 ± 0.3 mm Hg vs. 48.9 ± 0.6 mm Hg). When the aorta was inclined, at low P_ao of 45 mm Hg, V_prox was reduced by 30% from 0° to 45° (19.8 ± 2.3 mL vs. 28.3 ± 1.7 mL) and P_r was reduced by 66% (16.5 ± 0.1 mm Hg vs. 48.9 ± 0.6 mm Hg). However, at high P_ao of 115 mm Hg, V_prox remained unchanged with increasing angle (20.0 ± 1.0 mL) and P_r was reduced by 24% (80.6 ± 0.8 mm Hg vs. 106.4 ± 0.3 mm Hg). Increasing P_ao increased duration of inflation. At low P_ao, increasing angle resulted in increasing duration of inflation, but at high P_ao, increasing angle had the opposite effect. Duration of deflation generally decreased with P_ao and increased with increasing angle. The IAB pump is affected by both P_ao and angle, indicating that non‐normotensive patients or patients in the semi‐recumbent position might not receive the full benefits of IAB counterpulsation.     

Comparison of perfusion values after percutaneous transluminal angioplasty according to the severity of ischaemia in the diabetic foot

Percutaneous transluminal angioplasty (PTA) is now more frequently used to improve tissue perfusion in ischemic diabetic feet. However, there are concerns about its feasibility and effectiveness in severely ischaemic feet. This study aimed to compare the perfusion values after PTA according to the ischaemic degree of diabetic feet. This study included 133 ischaemic diabetic feet. The foot transcutaneous oxygen pressure (TcPO₂) and toe pressure were measured before the procedure and every second postoperative week for 6 weeks. The patients were divided into three groups according to ischaemic severity on the basis of TcPO₂ and toe pressures. In the “severely ischaemic” group, the TcPO₂ increased from 7.5 ± 4.9 to 40.3 ± 11.3 mm Hg (5.4‐fold) 6 weeks after the PTA (P < 0.001). The toe pressure increased from 8.5 ± 8.8 to 42.2 ± 19.3 mm Hg (5.0‐fold, P < 0.001). In the “mild” group, the TcPO₂ increased from 35.4 ± 2.5 to 41.8 ± 12.4 mm Hg (1.2‐fold, P = 0.003), and the toe pressure increased from 45.7 ± 12.3 to 54.3 ± 31.3 mm Hg (1.2‐fold, P > 0.05). Results of the “intermediate” group were in between. The most severely ischaemic group had the most dramatic increase of tissue perfusion after PTA. As such, PTA can be an effective method for increasing tissue perfusion even in the severely ischaemic diabetic feet.     

Relationship between volume status and blood pressure during chronic hemodialysis.

BACKGROUND: The relationship between volume status and blood pressure (BP) in chronic hemodialysis (HD) patients remains incompletely understood. Specifically, the effect of interdialytic fluid accumulation (or intradialytic fluid removal) on BP is controversial. METHODS: We determined the association of the intradialytic decrease in body weight (as an indicator of interdialytic fluid gain) and the intradialytic decrease in plasma volume (as an indicator of postdialysis volume status) with predialysis and postdialysis BP in a cross-sectional analysis of a subset of patients (N=468) from the Hemodialysis (HEMO) Study. Fifty-five percent of patients were female, 62% were black, 43% were diabetic and 72% were prescribed antihypertensive medications. Dry weight was defined as the postdialysis body weight below which the patient developed symptomatic hypotension or muscle cramps in the absence of edema. The intradialytic decrease in plasma volume was calculated from predialysis and postdialysis total plasma protein concentrations and was expressed as a percentage of the plasma volume at the beginning of HD. RESULTS: Predialysis systolic and diastolic BP values were 153.1 +/- 24.7 (mean +/- SD) and 81.7 +/- 14.8 mm Hg, respectively; postdialysis systolic and diastolic BP values were 136.6 +/- 22.7 and 73.9 +/- 13.6 mm Hg, respectively. As a result of HD, body weight was reduced by 3.1 +/- 1.3 kg and plasma volume was contracted by 10.1 +/- 9.5%. Multiple linear regression analyses showed that each kg reduction in body weight during HD was associated with a 2.95 mm Hg (P=0.004) and a 1.65 mm Hg (P=NS) higher predialysis and postdialysis systolic BP, respectively. In contrast, each 5% greater contraction of plasma volume during HD was associated with a 1.50 mm Hg (P=0.026) and a 2.56 mm Hg (P < 0.001) lower predialysis and postdialysis systolic BP, respectively. The effects of intradialytic decreases in body weight and plasma volume were greater on systolic BP than on diastolic BP. CONCLUSIONS: HD treatment generally reduces BP, and these reductions in BP are associated with intradialytic decreases in both body weight and plasma volume. The absolute predialysis and postdialysis BP levels are influenced differently by acute intradialytic decreases in body weight and acute intradialytic decreases in plasma volume; these parameters provide different information regarding volume status and may be dissociated from each other. Therefore, evaluation of volume status in chronic HD patients requires, at minimum, assessments of both interdialytic fluid accumulation (or the intradialytic decrease in body weight) and postdialysis volume overload.     

Impact of Dry Weight Determined by Calf Bioimpedance Ratio on Carotid Stiffness and Left Ventricular Hypertrophy in Hemodialysis Patients

Our previous study has shown that modification of bioimpedance technique by the measurement of bioimpedance ratio in the calf (calf‐BR) was a simple and practical method in assessing fluid status in hemodialysis patients. However, the consequences of periodical dry weight (DW) adjustment under the guidance of calf‐BR on target organ damage have not been investigated. One hundred fifteen hemodialysis patients were enrolled in this pilot trial. Patients were divided into bioimpedance group and control group according to their dialysis schedule. In the bioimpedance group, DW was routinely adjusted under the guidance of calf‐BR every 3 months. In the control group, the assessment of DW remained a clinical judgment. Carotid stiffness, left ventricular mass index (LVMI), and calf‐BR were measured at baseline and at the 12th month in both groups. Home blood pressure (BP) was monitored monthly. Episodes of dialysis‐related adverse events were recorded. No significant differences were observed in parameters between the two groups at baseline. Compared with the control group, the bioimpedance group had significantly lower values in terms of the annual averages of systolic home BP (147.4 ± 15.3 mm Hg vs. 152.6 ± 16.9 mm Hg, P = 0.019), carotid stiffness index β (10.7 ± 3.3 vs. 12.2 ± 3.1, P = 0.003), LVMI (155.21 ± 15.64 g/m² vs. 165.17 ± 16.76 g/m², P < 0.001), and the percentage of individuals with calf‐BR over target range (P = 0.040) at month 12, with less annual averages of antihypertensive medications used and lower frequency of intradialytic hypotension, muscle cramps, or clotted angioaccess. Continued DW control achieved by periodical calf‐BR measurement improved arterial stiffness and left ventricular hypertrophy with good tolerability in hemodialysis patients.     

Preservation of Blood Pressure Stability with Hypertonic Mannitol during Hemodialysis Initiation

Background: Intradialytic hypotensive events are common among hemodialysis patients and are associated with a variety of patient- and procedure-related factors, including intradialytic decline in plasma osmolality. Prior studies and practice have suggested that administration of osmotically active drugs may ameliorate blood pressure decline during chronic hemodialysis. Methods: Clinical and treatment data were collected for 102 consecutive patients requiring initiation of renal replacement therapy in 2 major teaching hospitals. Routine administration of mannitol differed according to institutional protocols, allowing its examination as the primary exposure of interest. Generalized linear models were fit to estimate associations of mannitol use during dialysis initiation with intradialytic blood pressure, as assessed by: (1) intradialytic blood pressure decline; (2) nadir intradialytic blood pressure; (3) absolute systolic blood pressure <90 mm Hg or decline >20 mm Hg. Results: Mean age was 62 years (±16), 70% were male and 44% were diabetic. Mean predialysis and nadir systolic blood pressure were 142 mm Hg (±29) and 121 mm Hg (±26), respectively. Mannitol administration was associated with a lesser decline in intradialytic blood pressure, a higher nadir blood pressure and fewer hypotensive events requiring intervention. No effect modification was evident according to diabetes or acuity of kidney disease (chronic vs. acute). Conclusions: Mannitol administration appears to preserve hemodynamic stability during hemodialysis initiation. Randomized controlled trials are needed to confirm these findings and identify optimal management strategies to prevent intradialytic hypotension.     

Dialysis Reduces Portal Pressure in Patients With Chronic Hepatitis C

The purpose of this study was to characterize changes in hepatic venous pressures in patients with chronic hepatitis C. The histology and laboratory data from patients with chronic hepatitis C who underwent a transjugular liver biopsy (TJLB) and hepatic venous pressure gradient measurement were analyzed. Portal hypertension was defined as hepatic venous pressure gradient ≥6 mm Hg. A single pathologist masked to hepatic venous pressure gradient scored liver sections for inflammation and fibrosis. The patients with high‐grade inflammation (relative risk [RR] 2.82, P = 0.027, multivariate analysis) and late‐stage fibrosis (RR 2.81, P = 0.022) were more likely to have a hepatic venous pressure gradient ≥6 mm Hg, while the patients on dialysis (RR 0.32, P = 0.01) were less likely to have a hepatic venous pressure gradient ≥6 mm Hg. The patients on dialysis (n = 58) had an elevated serum blood urea nitrogen and creatinine when compared with those who were not (n = 75) (47.6 ± 3.3 and 7.98 ± 0.4 vs. 25.9 ± 2.0 and 1.66 ± 0.22 mg/dL, respectively; P < 0.001). While the hepatic venous pressure gradient increased with the rising levels of liver fibrosis in the latter group (P < 0.01), it did not change in the patients on dialysis (P = 0.41). The median hepatic venous pressure gradient was especially low in late‐stage fibrosis patients on dialysis when compared with the latter group (5 vs. 10 mm Hg, P = 0.017). In patients on dialysis, serum transaminases were low across all levels of fibrosis. Twenty‐three of the 92 patients with early fibrosis had a hepatic venous pressure gradient ≥6 mm Hg. In patients with chronic hepatitis C, concomitant TJLB and hepatic venous pressure gradient measurement identify those who have early fibrosis and portal hypertension. Long‐term hemodialysis may reduce portal pressure in these patients.     

Blood pressure assessment in haemodialysis patients: Comparison between pre-dialysis blood pressure and ambulatory blood pressure measurement

Aim: Hypertension is common in haemodialysis (HD) patients. Determining the most appropriate method of blood pressure (BP) measurement, representative of target organ damage, is still an issue. BP variations between pre‐ and post‐HD treatment, or between on‐dialysis day and off‐dialysis day, are common. The aim of this study was to examine the possible differences between pre‐HD office BP (OBP) levels, inter‐HD (iHD) or HD day 24 h ambulatory BP measurement (ABPM) with 48 h ABPM, where the latter was considered the gold standard. Methods: 163 HD patients were studied. BP was monitored consecutively for 48 h with a Takeda TM2421 device, then sub‐analysed into two periods of 24 h: HD and iHD day. An average of 12 sessions pre‐HD OBP measurements was determined. Results: OBP significantly overestimates systolic (SBP) and diastolic BP (DBP) when compared with 48 h ABPM. SBP and DBP are significantly higher on iHD day than on HD day: 141.2 ± 20.8 versus 137.9 ± 20.9, and 77.1 ± 11.1 versus 76.1 ± 10.9 (P < 0.01). No differences of SBP night/day ratio were reported between 48 h ABPM and iHD 24 h ABPM or HD 24 h ABPM. The highest correlations were reported between 48 h SBP/DBP with iHD or HD 24 h ABPM (r² = 0.95, P < 0.001), while the lowest between 48 h SBP/DBP and OBP (r² = 0.40, P < 0.01, r² = 0.12, P < 0.01). The narrowest limits of agreement using the Bland and Altman test were reported between 48 h SBP or DBP and 24 h iHD or HD day ABPM. Considering 48 h ABPM, 80.5% of patients had BP higher than the norm, compared with 61.7% of patients in the case of OBP (χ² = 13.28, P < 0.001). The sensibility for detecting hypertension for iHD day 24 h ABPM was 98.4%, with specificity of 90%. The sensibility of 24 h HD day ABPM was 90.3%, with specificity 96.6%. In the case of OBP, sensibility and specificity were considerably lower, that is, 72.6% and 83.3% respectively. Conclusion: Significant differences are shown between OBP and 48 h ABPM in the recognition of a hypertensive state. OBP measurement has a lower sensibility and specificity than 24 h ABPM, which remains a valid alternative approach to 48 h ABPM in HD patients. Errors of OBP estimation should be taken into account, with possible negative impact on treatment strategies and epidemiology studies.     

In vivo comparison of the coagulation capability of SonoSurg and Harmonic Ace on 4 mm and 5 mm arteries

Introduction Ultrasonic dissectors are useful to ligate arteries, but their effectiveness on larger arteries has not been thoroughly documented in vivo. The purpose of this study is to determine the bursting pressure of sealed arteries and the incidence of failure to adequately seal 4 mm and 5 mm arteries in a porcine model using two commercially available ultrasonic coagulators. Methods The splenic, renal, superior mesenteric and carotid arteries of 60 kg swine were dissected and sealed alternating between SonoSurg (SS), 70% output (Olympus Surgical America) and Harmonic Ace (HA), level 3, (Ethicon Endosurgery).The burst pressures of each sealed segment was measured by subjecting them to infusion of water at 50 ml/hr until the seal burst. The mean burst pressure, incidence of burst pressure less than 360mm Hg and incidence of not sealing were calculated and compared with the t and chi-square tests. Significance was assumed at p = 0.05. Results Each instrument was used to divide 44 arteries measuring between 4 and 5 mm (4.7 ± 0.48 mm vs. 4.7 ± 0.44 mm, p = NS, SS vs. HA, respectively) in diameter. The burst pressure (900.2 ± 574.9 mmHg vs. 896.6 ± 481.0 mmHg, p = NS) was not different comparing SS with. HA. Four vessels (9.1%) failed to seal with each instrument and resulted in immediate hemorrhage. Including the vessel that failed to seal initially, five vessels (11.4%) ligated with SS and six (13.6%) ligated with HA had burst pressure less than 360 mm Hg. This incidence of inadequate sealing was not significantly different between the two instruments when compared with chi-square analysis. Conclusion SS and HA seal 4–5 mm arteries with similar burst pressures. There is no difference in the incidences of failure to initially seal the arteries or in bursting pressure <360 mmHg in 4–5 mm arteries in the porcine model.     

Mathematical modeling of thermal and circulatory effects during hemodialysis

Intradialytic hypotension (IDH) is one of the most common complications of hemodialysis (HD) treatment. The initiating factor of IDH is a decrease in blood volume, which is related to an imbalance between ultrafiltration (UF) and refilling rate. Impaired reactivity of resistance and capacitance vessels in reaction to hypovolemia plays possibly a major role in the occurrence of IDH. These vessels also fulfill an important function in body temperature regulation. UF‐induced cutaneous vasoconstriction would result in a reduced surface heat loss and an increase in core temperature. To release body heat, skin blood flow is increased at a later stage of the HD treatment, whereby possibly IDH can occur. The aim of the study is to develop a mathematical model that can provide insight into the impact of thermoregulatory processes on the cardiovascular (CV) system during HD treatment. The mathematical procedure has been created by coupling a thermo‐physiological model with a CV model to study regulation mechanisms in the human body during HD + UF. Model simulations for isothermal versus thermoneutral HD + UF were compared with measurement data of patients on chronic intermittent HD (n = 13). Core temperature during simulated HD + UF sessions increased within the range of measurement data (0.23°C vs. 0.32 ± 0.41°C). The model showed a decline in mean arterial pressure of ?7% for thermoneutral HD + UF versus ?4% for isothermal HD + UF after 200 min during which relative blood volume changed by ?13%. In conclusion, simulation results of the combined model show possibilities for predicting circulatory and thermal responses during HD + UF.     

Comparison of Continuous‐Flow and Pulsatile‐Flow Blood Pumps on Reducing Pulmonary Artery Pressure in Patients With Fixed Pulmonary Hypertension

Pulmonary hypertension (PH) is considered as a risk factor for morbidity and mortality in patients undergoing heart transplantation. Recently, left ventricular assist device (LVAD) implantation has been increasingly used in reducing pulmonary artery pressure (PAP) in patients with PH unresponsive to medical therapy. Herein, we aimed to compare the efficacy of continuous‐flow and pulsatile‐flow blood pumps on the improvement of PH in mechanical circulatory support patients. Twenty‐seven patients with end‐stage heart failure who underwent LVAD implantation surgery were enrolled. Fifteen of them (55.6%) had continuous‐flow pump (HeartWare Ventricular Assist System, HeartWare, Inc., Miramar, FL, USA), and 12 of them (44.4%) had pulsatile pump (Berlin Heart EXCOR ventricular assist device, Berlin Heart AG, Berlin, Germany). The efficacy of LVADs on the improvement of PH was compared between continuous‐flow and pulsatile pumps by the evaluation of systolic PAP, tricuspid annular plane systolic excursion (TAPSE), right ventricular systolic motion (RVSM), right ventricular ejection fraction (RVEF), and grade of tricuspid insufficiency (TI) for each of the study participants. All of the 15 patients who underwent continuous‐flow blood pump implantation surgery (Group 1) were male with a mean age of 46.9 ± 11.7 years, and in pulsatile‐flow blood pump implanted participants (Group 2), the mean age was 40.6 ± 16.8 years, all of whom were also male (P = 0.259). Mean follow‐up was 313.7 ± 241.3 days in Group 1 and 448.7 ± 120.7 days in Group 2 (P = 0.139). In Group 1, mean preoperative and postoperative systolic PAP were measured as 51.7 ± 12.2 mm Hg and 22.2 ± 3.4 mm Hg, respectively, while those in Group 2 were 54.5 ± 7.5 mm Hg and 33.9 ± 6.4 mm Hg, respectively. A significantly greater decrease in systolic PAP was noticed in patients with continuous‐flow blood pumps (P = 0.023); however, no statistically significant difference was found when we considered the change in TAPSE between study groups (P = 0.112). A statistical significance in the alteration of RVEF, RVSM, and the grade of TI during study visits was not found between the study groups (P = 0.472, P = 0.887, and P = 0.237, respectively). Although the two studied types of LVADs were found to be effective in reducing PAP in heart transplantation candidates with PH, lesser postoperative systolic PAP values were achieved in patients who underwent continuous‐flow pump implantation surgery.     

Prophylactic Use of Intra‐Aortic Balloon Pumps in Open Heart Surgery

During a 1‐year period, intra‐aortic balloon pumps (IABPs) were used in open heart surgery on 57 patients. Indications were prophylactic usage for coronary artery bypass grafting (CABG) in 52 patients, prophylactic usage for valve replacement in three patients, and cardiopulmonary bypass (CPB) weaning during valve replacement in two patients. The 52 CABG patients comprised 94.5% of all CABG procedures during the period. Sheathless 8 Fr IABPs were used in all cases. The 57 patients using IABPs were analyzed. The mean duration of IABP use was 41.7 h. Morbidity was not associated with using IABPs. There was one case of balloon rupture. Hemostasis was performed easily after removing IABP catheters by compressing the groin for approximately 15 min. The lowest blood pressure during anastomosis or cardiac arrest was also assessed. The lowest peak pressure was 55.9 ± 17.3 mm Hg for patients with IABP still turned on, and the lowest mean pressure was 34.7 ± 6.5 mm Hg for patients with IABP temporarily turned off. Peak blood pressure after CPB was 73.8 ± 17.8 mm Hg. During open heart surgery under anesthesia with the low blood pressure presented by this series, use of IABPs enabled patients to tolerate the procedure. In conclusion, aggressive use of IABPs is easy, safe, and effective with no related morbidity.     

Blood volume controlled hemodialysis in hypotension-prone patients: a randomized,multicenter controlled trial

BACKGROUND: Recently we have devised and tested a biofeedback system for controlling blood volume (BV) changes during hemodialysis (HD) along an ideal trajectory (blood volume tracking, BVT), continuously modifying the weight loss rate and dialysate conductivity. This multicenter, prospective, randomized, crossover study aimed to clarify whether BVT (treatment B) can improve hypotension-prone patients' treatment tolerance, compared with conventional hemodialysis (treatment A). METHODS: Thirty-six hypotension-prone patients enrolled from 10 hemodialysis (HD) centers were randomly assigned to either of the study sequences ABAB or BABA, each lasting four months. RESULTS: A 30% reduction in intradialytic hypotension (IDH) events was observed in treatment B as compared with A (23.5% vs. 33.5%, P = 0.004). The reduction was related to the number of IDH in treatment A (y = 0.54x + 5; r = 0.4; P < 0.001): the more IDH episodes in treatment A, the better the response in treatment B. The best responders to treatment B showed pre-dialysis systolic blood pressure values higher than the poor responders (P = 0.04). A 10% overall reduction in inter-dialysis symptoms was obtained also in treatment B compared to A (P < 0.001). Body weight gain, pre-dialysis blood pressure, intradialytic weight loss as well as Kt/V did not differ between the two treatments. CONCLUSIONS: An overall improvement in the treatment tolerance was observed with BVT, particularly intradialytic cardiovascular stability. Patients with the highest incidence of IDH during conventional HD and free from chronic pre-dialysis hypotension seem to respond better. Inter-dialysis symptoms also seem to improve with control of BV.     

The Influence of Colloid Osmotic Pressure on Hydrostatic Pressures in High‐ and Low‐Flux Hemodialyzers

The aim of this study was to examine the relationship between hydrostatic trans‐membrane pressure (TMP_h) and colloid osmotic pressure (COP) in low‐flux (LF) and high‐flux (HF) dialyzers. Hydrostatic pressures were measured in dialyzers distinguished by their ultrafiltration coefficient K_uf (16 and 85 mL/h/mm Hg) under constant dialysate flow and variable blood flow (Q_b) ranging from 0 to 400 mL/min using (i) alginate (70 kDa) dissolved in dialysate, (ii) diluted, undiluted, and concentrated plasma, or (iii) whole blood at different hematocrit, all in absence of ultrafiltration (UF). For a given fluid, TMP_h linearly increased with increasing Q_b. The intercept of the linear TMP_h to Q_b relationship correlated with measured COP with an average bias of 1.00 ± 2.26 mm Hg and a concordance correlation coefficient of 0.98. The slope of the linear TMP_h to Q_b relationship increased with increasing sample viscosity and was much larger in HF dialyzers under otherwise identical operating conditions, most likely because of increased internal filtration. The TMP_h to Q_b relationship measured in dialyzers in absence of UF can be described by the intercept related to measured COP and the slope related to internal filtration. This relationship could be of interest to estimate internal filtration and COP under in vivo conditions.