Nocturnal hemodialysis increases arterial baroreflex sensitivity and compliance and normalizes blood pressure of hypertensive patients with end-stage renal disease

BACKGROUND: Impaired neural control of heart rate, elevated arterial stiffness, and hypertension place patients with end-stage renal disease (ESRD) at increased risk of cardiovascular mortality. Nocturnal hemodialysis (6 x 8 hours/week), a more intense program than conventional hemodialysis (3 x 4 hours/week), lowers blood pressure and restores brachial dilator responses to hyperemia and nitrates. METHODS: We hypothesized that nocturnal hemodialysis would increase arterial baroreflex sensitivity for heart rate of hypertensive ESRD patients by an afferent vascular mechanism. Ten consecutive hypertensive ESRD patients (age 42 +/- 4) (mean +/- SEM) receiving conventional hemodialysis were studied before and 2 months after conversion to nocturnal hemodialysis. Regression slopes relating RR interval responses to rises or falls in systolic blood pressure were averaged to derive spontaneous baroreflex sensitivity for heart rate for each patient, and the stroke volume/pulse pressure ratio was used to estimate total arterial compliance. RESULTS: Dialysis dose (Kt/V per session) increased from 1.2 +/- 0.05 to 2.1 +/- 0.1 (P < 0.05). Despite withdrawal of antihypertensive medications (from 2.9 to 0.1 drugs/patient), nocturnal hemodialysis lowered systolic blood pressure (from 143 +/- 4 to 120 +/- 6 mm Hg) (P= 0.001). Both baroreflex sensitivity (from 4.76 +/- 1.1 msec/mm Hg to 6.91 +/- 1.1 msec/mm Hg) (P= 0.04) and total arterial compliance (from 0.98 +/- 0.13 mL/mm Hg to 1.43 +/- 0.2 mL/mm Hg) (P= 0.02) were higher following conversion to nocturnal hemodialysis. Increases in baroreflex sensitivity correlated with increases in stroke volume/pulse pressure (r= 0.845, P= 0.002). CONCLUSION: These findings are consistent with the concept that nocturnal hemodialysis increases baroreflex sensitivity via greater afferent baroreceptor responsiveness to pulsatile pressure. A more favorable risk profile, due to enhanced baroreflex regulation of the circulation and vascular compliance, may translate into lower cardiovascular event rates in ESRD patients receiving nocturnal hemodialysis.     

Effects of different dialysis modalities on cardiac autonomic dysfunctions in end-stage renal disease patients: one year prospective study

Cardiac autonomic dysfunction (CAD) is a common problem in patients with end-stage renal disease (ESRD) and may contribute to the risk of cardiac mortality. Long-term effects of dialysis modalities on CAD in ESRD patients are not clear. In this one-year prospective study, we studied the effects of different dialysis modalities on CAD in ESRD patients. The study consisted of 20 ESRD patients who had the indications for initiating dialysis therapy (13 hemodialysis and 7 CAPD patients) and 15 healthy controls (M/F: 5/10; age 30 +/- 4). In all the subjects, first at the beginning of study (in patient groups just before initiating dialysis therapy) and then after 12 months, we studied 24 hours ECG-Holter monitoring and heart rate variability parameters (time and frequency domain analysis parameters; SDNN: standard deviations of nn intervals, rMSSD: square root of the median of standard deviation, HRVI: heart rate variability index, LF/HF: low frequency/high frequency). In ESRD patients, before dialysis therapy, all the parameters of time domain analysis were significantly lower compared to control group (p = 0.001). In patient groups, after dialysis therapy (on the 12th month), significant improvement was observed in time domain analysis parameters (p = 0.001). When dialysis modalities were compared, the increase in the time domain analysis parameters was significantly greater in the CAPD group compared to hemodialysis (HD) group. Our findings suggest that CAD is frequent in ESRD patients, a dialysis therapy of 12 months can cause significant improvement on CAD and the ameliorative effect of CAPD is better than HD.     

Impaired arterial compliance and aerobic endurance in kidney transplant recipients

BACKGROUND: Cardiovascular disease is the leading cause of morbidity and mortality in kidney transplant recipients (KTR). Two risk factors for cardiovascular disease that have not been examined in this population are arterial compliance and aerobic capacity. The primary objective was to determine small and large artery compliance and aerobic endurance in KTR. A secondary objective was to explore the relationship between aging and arterial compliance and aerobic endurance in KTR. METHODS: Sixty-two clinically stable KTR were recruited from the University of Alberta Renal Transplant Clinic. Small and large artery compliance was assessed using computerized arterial pulse waveform analysis. Aerobic endurance was determined using the six-minute walk test. Age-matched normative data from healthy individuals was used for comparison. RESULTS: Small arterial compliance was lower in KTR (5.5+/-3 ml/mm Hg x 100) compared to age-matched healthy individuals' predicted values (7.9+/-0.9 ml/mm Hg x 100, P<0.0001). No difference was found for large artery compliance between KTR (16.0+/-6.6 ml/mm Hg x 10) and age-matched healthy predicted values (15.2+/-1.3 ml/mm Hg x 10, P=0.5). Small and large artery compliance were 35% (P=0.026) and 36% (P=0.005) higher in younger (<51 years) versus older (>51 years) KTR, respectively. The six-minute walk distance was 28% lower in KTR (495+/-92 m) compared to healthy age-predicted values (692+/-56 m P<0.0001). CONCLUSIONS: Compromised arterial compliance and poor aerobic endurance may partially explain the high incidence of cardiovascular disease in KTR. Interventions demonstrated to improve these parameters may afford substantial clinical benefit in this population.     

Angiotensin receptor blockade and arterial compliance in chronic kidney disease: a pilot study

BACKGROUND: Almost 20 million people in the US have chronic kidney disease (CKD). Cardiovascular disease and arterial wall abnormalities are common in this population. Because angiotensin II may have adverse effects on the arterial wall, we hypothesized that an angiotensin receptor blocker (ARB) would improve arterial compliance as compared with placebo in subjects with CKD. METHODS: We performed a double-blinded, placebo-controlled pilot study in which 25 subjects with stages 2 or 3 CKD and proteinuria <1 g were randomized to either the ARB, eprosartan, or placebo and titrated to achieve a goal blood pressure (BP) <130/85 mm Hg. Arterial compliance was measured at baseline and at 8 weeks. RESULTS: Baseline characteristics were similar between the groups and included mean estimated glomerular filtration rate 63 +/- 14 ml/min/1.73 m(2), heart rate 76 +/- 10 beats/min, BP 142 +/- 12/81 +/- 8 mm Hg, 64% diabetic, 44% male, and 40% white, though subjects in the eprosartan group were younger (60 +/- 12 vs. 70 +/- 6 years, p = 0.01). There were no significant differences between the groups in large or small artery compliance measurements either at baseline or at 8 weeks, but there was a statistically significant improvement from baseline in small artery compliance in the eprosartan group (from median 2.5 ml/mm Hg x 100 [90% CI (1.1, 4.7)] to 4.0 ml/mm Hg x 100 [90% CI (1.9, 6.7)] (p = 0.01)) not seen in the placebo group. CONCLUSION: Use of an ARB to achieve recommended BP is associated with improved small artery compliance in people with CKD, though larger studies are needed to confirm these findings.     

Intraocular pressure changes during hemodialysis: prevention of excessive dialytic rise and development of severe metabolic acidosis following acetazolamide therapy

The response of intraocular pressure (IOP) to hemodialysis was investigated in 55 patients with end-stage kidney disease enrolled in a chronic dialysis program. The mean level of IOP, measured by the Goldman applanation tonometer, before dialysis was slightly lower than that of a control group of 50 healthy subjects (14.9 +/- 2 mm Hg vs 15.6 +/- 1.9 mm Hg. p = .07). During dialysis IOP underwent an excessive rise (7.8 to 12.5 mm Hg) in 10 patients (group 1), remained unchanged (variations below 2 mm Hg) in 41 patients (group 2), and decreased (3.1 to 5.1 mm Hg) in 4 patients (group 3). In group 1 patients, gonioscopy showed a narrow angle between iris and lateral cornea. Conversely, the anterior chamber angle was normal in patients of groups 2 and 3. The effect of a 7-day course of acetazolamide therapy (500 mg per day orally) on IOP was investigated in group 1 patients. Acetazolamide was capable of preventing the excessive IOP rise during dialysis. The mean reduction of such a dialytic rise was 8.1 mm Hg. However, despite this effect, in these patients the IOP level after dialysis still remained significantly higher than that of patients of group 2 (18.1 +/- 1 mm Hg vs 14.9 +/- 0.8 mm Hg. p less than .0001). Acetazolamide therapy precipitated in all patients a severe metabolic acidosis (blood pH fell from 7.38 +/- 0.02 to 7.24 +/- 0.03, p less than .0001; and bicarbonate concentration from 21 +/- 2.5 mmol/liter to 12.3 +/- 2.4 mmol/liter, p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of erythropoietin on cardiovascular prognosis parameters in hemodialysis patients

BACKGROUND: Renal anemia is an important determinant for left ventricular hypertrophy in dialysis patients and an independent prognosis parameter for the cardiovascular survival in dialysis patients. In addition, an autonomic dysfunction is associated with the uremic state and influences the cardiovascular risk in patients with end-stage renal disease (ESRD). METHODS: We investigated in this prospective longitudinal study the effect of hemoglobin normalization by a chronic treatment with recombinant human erythropoietin (rhEPO) on cardiovascular prognosis parameters in 23 patients on chronic hemodialysis with renal anemia (hemoglobin concentration < or =10.5 g/dL) and echocardiographically proven left ventricular hypertrophy. We studied muscle sympathetic nerve activity measured by microneurography; cardiopulmonary baroreflex activity by lower-body negative pressure (LBNP-) testing; left ventricular structure and mass index (LVMI) by echocardiography; blood pressure by 24-hour readings; peripheral blood flow and vascular resistance by plethysmography before (U1) and after 7 months of chronic rhEPO treatment (U2). RESULTS: In the anemic state, mean (+/- SD) muscle sympathetic nerve activity in ESRD was elevated (U1 rest, 34 +/- 13 bursts per minute) and cardiopulmonary baroreflex response during LBNP markedly lacking (U1 -15 mm Hg, 34 +/- 13 bursts per minute) reflecting a severely impaired autonomic function. Normalization of the hemoglobin concentration by chronic rhEPO treatment (U1, 10.5 +/- 0.9 g/dL versus U2, 13.4 +/- 3.1 g/dL, P <0.001) did not influence sympathetic nerve activity (U2, 34 +/- 15 bursts per minute, NS) and cardiopulmonary baroreflex sensitivity did not change (U2 -15 mm Hg, 37 +/- 16 bursts per minute, NS). LVMI decreased significantly after chronic treatment with rhEPO (U1, 134 +/- 26 g/m2 versus U2, 97 +/- 25 g/m2, P < 0.001) and left ventricular geometry developed from an asymmetric to a symmetric configuration (U1, relative wall thickness 0.58 versus U2, 0.43, P < 0.001). Under treatment with rhEPO, 24-hour systolic and diastolic blood pressure did not increase (systolic U1, 132 +/- 4 mm Hg versus U2, 128 +/- 3 mm Hg, NS, and diastolic U1, 76 +/- 2 mm Hg versus U2, 73 +/- 2 mm Hg, NS). Peripheral blood flow (U1, 6.1 +/- 3.3 mL/100 mL/min versus U2, 6.2 +/- 0.6 mL/100 mL/min, NS) as well as forearm vascular resistance (U1, 15.7 +/- 3.3 mm Hg/mL/100 mL versus U2, 14.9 +/- 3.1 mm Hg/mL/100 mL, NS) did not change by chronic rhEPO treatment. CONCLUSION: Normalization of hemoglobin by chronic rhEPO treatment in dialysis patients has beneficial cardiovascular effects with regression of left ventricular hypertrophy and improvement of left ventricular geometry. However, a reduction of sympathetic overactivity or a resetting of baroreceptor sensitivity by a rhEPO treatment in dialysis patients in the medium-term could not be demonstrated. The reason for this may be the complex and multifactorial pathomechanism of autonomic dysfunction and cardiovascular disease in ESRD.     

Aortic pulse wave velocity and arterial wave reflections predict the extent and severity of coronary artery disease in chronic kidney disease patients

BACKGROUND: Increased aortic stiffness markers - aortic pulse wave velocity (PWV) and augmentation index (AIx) - are powerful predictors of survival in ESRD patients - well-recognized for the high prevalence of coronary artery disease (CAD) and unusually high PWV and AIx. Recently, decreased aortic compliance has been shown to be predictive of primary coronary events in hypertensive patients with normal renal function. We aimed to explore relationships between arterial stiffness and CAD in cohorts of patients with chronic kidney disease (CKD). METHODS AND RESULTS: 46 patients with chronic kidney disease (33 males, aged 55.7+/- 13.2 years, 20 on dialysis, 18 post renal transplantation, and 8 with glomerular filtration rate (GFR) between 10 and 25 ml/min) underwent coronary angiography for the assessment of CAD. PWV and aortic AIx were determined from pulse waveform analysis of arterial waveforms recorded by applanation tonometry using a SphygmoCortm device. The atherosclerosis burden score was calculated by adding the percentage luminal reduction of the most severe lesion in each artery. Patients with normal angiograms had significantly less arterial stiffness (as reflected by both a lower PWV=8.42+/-1.53 m/s and a lower AIx=17.9+/-5.55 %) compared with the 35 subjects with evidence of obstructive coronary disease at angiography (PWV=9.21+/-1.15 m/s and AIx=23.4+/-5.4 %, P<0.05 for both). Moreover, as more coronary vessels were affected, PWV and AIx increased proportionally. Based on receiver operating characteristics (ROC) curve analysis mean PWV levels showed an optimal cut-off point at 8.35 m/s (sensitivity=0.77; specificity=0.60), while mean AIx levels showed an optimal cut-off point at 17% (sensitivity=0.87; specificity=0.70). There was a statistically significant linear relationship between the atherosclerosis burden and both measures of arterial stiffness: PWV (r=0.31, p=0.007) and AIx (r=0.46, p=0.003). Independent predictors for the arterial stiffness parameters in this CKD population (multiple stepwise regression analysis) were age (r=0.69 for PWV and r=0.62 for AIx), and mean arterial pressure (MAP) (for AIx, p<0.0001). CONCLUSION: This study provides the first direct evidence in a cross-sectional investigation that PWV and AIx are related to the extent of coronary obstruction in CKD patients.     

Acute effects of haemodialysis on endothelial function and large artery elasticity.

BACKGROUND: Disturbances of functional properties of large arteries contribute to increased cardiovascular morbidity and mortality in patients with end-stage renal disease. However, it is not clear whether haemodialysis per se acutely affects mechanical vessel wall properties or endothelial function. METHODS: Twenty-five chronic haemodialysis patients (mean+/-standard error of the mean (SEM): age 52+/-5 years; time on dialysis 63+/-7 months; blood pressure 132+/-4/72+/-2 mmHg) were studied before and immediately after a haemodialysis (HD) session using a polysulphone dialyser (ultrafiltration 1460+/-54 ml), as well as on the following day. Blood pressure was measured with an automatic sphygmomanometer and applanation tonometry. End-diastolic diameter and distension of the brachial and carotid arteries were measured by Doppler frequency analysis of vessel wall movements in M-mode using a multigate pulsed Doppler system and aortic pulse wave velocity (PWV) by an automatic device (Complior). Endothelial function was determined as brachial artery flow-mediated dilation (FMD) and compared with endothelium-independent nitroglycerine-induced dilation (NMD). RESULTS: FMD was 7.9+/-1.8% in patients before HD and did not change significantly after HD or in the dialysis-free intervall (6.7+/-2.1 and 7.1+/-2.0%, respectively; NS). The same was true for NMD and PWV (12.6+/-0.8 m/s before HD, 12.8+/-0.8 m/s after HD, and 11.9+/-0.7 m/s on the HD-free day). Carotid distensibility coefficients decreased significantly during HD (from 18.1+/-1.9 x 10(-3)/kPa to 16.7+/-2.2 x 10(-3)/kPa, P<0.05) and increased again on the HD-free day (19.8+/-2.4 x 10(-3)/kPa). However, when corrected for blood pressure by tonometry, isobaric carotid distensibility did not change significantly. Brachial artery distensibility also did not show significant acute changes. CONCLUSIONS: Haemodialysis per se did not have a significant effect on endothelial function or large artery mechanical vessel wall properties in patients on maintenance dialysis therapy.     

Effects of oxygen breathing and erythropoietin on hypoxic vasodilation in uremic anemia.

Loss of hypoxic vasodilation has been proposed as a causative factor in the development of hypertension in dialysis patients treated with recombinant human erythropoietin (rHuEPO). Venous occlusion plethysmography was therefore performed on 22 dialysis patients (aged 23 to 71 years, dialysis duration 6 to 260 months, 8 males) before and after correction of anemia with rHuEPO, 50 U/kg 3x/week (Hb: 7.4 +/- 0.3 vs. 10.8 +2- 0.3 g/dl, P less than 0.0001). Hypertension (greater than 15 mm Hg rise in mean BP) occurred in 11 patients. The study was performed while breathing room air and repeated after breathing 60% O2 for 10 to 12 minutes. Before rHuEPO therapy, total blood O2 content increased from 10.01 +/- 0.39 to 10.32 +/- 0.29 ml O2/100 ml blood with breathing 60% O2 (P less than 0.01). After correction of anemia it was 14.65 +/- 0.40 ml O2/100 ml blood on room air (P less than 0.001). There was a significant decrease in forearm blood flow (7.9 +/- 0.5 vs. 6.5 +/- 0.6 ml/min/100 ml tissue, P less than 0.05) and increase in forearm vascular resistance (12.8 +/- 0.1 vs. 16.8 +/- 0.2 mm Hg/ml/min/100 ml tissue, P less than 0.05) with O2 breathing prior to rHuEPO therapy in the blood pressure responders, but no change in these parameters in the group in which blood pressure remained unchanged. When all patients were studied on room air, forearm vascular resistance rose significantly after correction of anemia (13.0 +/- 0.8 vs. 16.3 +/- 0.8 mm Hg/ml/min/100 ml tissue, P less than 0.05), compared with that prior to rHuEPO therapy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Delayed hypotensive response to dialysis in hypertensive patients with end-stage renal disease

This study was designed to determine the ambulatory arterial blood pressure profile in hypertensive patients with end-stage renal disease during and following hemodialysis. Blood pressure was noninvasively monitored at 15-min intervals for 24 h using a fully automatic portable recorder, while the 10 patients studied followed their customary activities and were not receiving any antihypertensive medications. Prior to dialysis, the blood pressure was 179 +/- 7.0/101 +/- 3.7 mm Hg. After 4 h of dialysis, the systolic blood pressure did not change, while the diastolic blood pressure fell only slightly (178 +/- 4.2/94 +/- 2.4 mm Hg). After dialysis was completed, a progressive fall in both systolic and diastolic blood pressures was observed reaching the lowest value in the 5th h after dialysis (146 +/- 5.5/75 +/- 3.2 mm Hg). Thereafter, the fall in blood pressure was sustained during sleep (147 +/- 1.7/77 +/- 0.9 mm Hg) and during routine daily activities (147 +/- 2.0/78 +/- 1.0 mm Hg). The delayed fall in blood pressure was observed in patients in whom the plasma renin activity was elevated (8.4 +/- 2.4 ng/ml/h) and in patients in whom the plasma renin activity was low or normal (0.9 +/- 0.2 ng/ml/h). Our data suggest that during dialysis vasopressor mechanisms are activated to sustain blood pressure and that following dialysis such mechanisms are attenuated allowing the blood pressure to fall towards normal levels. The delayed fall in blood pressure documented by this study indicates that in many hypertensive patients with end-stage renal disease antihypertensive drug therapy is not required the day after dialysis.     

Impairments of the biological properties of serum albumin in patients on haemodialysis

BACKGROUND: End-stage renal disease (ESRD) is associated with enhanced oxidative stress and may contribute to substantial cardiovascular complications in dialysis patients. Recent studies suggested that human serum albumin (HSA), the major plasma protein, may possess a direct vasculoprotective antioxidant effect. In this study, we investigated if such protective effect is impaired in uremic milieu. METHODS: Thirty-one ESRD patients on maintenance haemodialysis and 22 age-matched healthy controls were recruited. Serum albumin was purified and changes in biological properties of HSA were analysed by several biochemistry techniques, spectrophotometric measurements, ligand-binding assays and western blot analysis. RESULTS: We found that both dityrosine (0.25 +/- 0.1 vs 0.15 +/- 0.07, P < 0.001), and carbonyl (10.5 +/- 1.88 nmol/mg vs 5.29 +/- 1.21 nmol/mg, P < 0.001) contents were increased in the uremic HSA. Decreased thiol activity of plasma was also noted and may be related to dimerization of HSA. In addition, uremic HSA had shown impaired ligand-binding capability such as haemin (0.37 x 10(7)/M vs 2.18 x 10(7)/M, P < 0.001), bilirubin (0.08 x 10(6)/M vs 0.15 x 10(6)/M, P < 0.05) and cis-parinaric acid (3.8 x 10(7)/M vs 2.9 x 10(7)/M, P < 0.05). Furthermore, using two different systems namely copper mediated oxidation of human low density lipoproteins and the free radicals mediated haemolysis test, we have demonstrated that the observed changes of uremic HSA can affect its antioxidant properties. CONCLUSION: In conclusion, the present study demonstrated that the quality and integrity of HSA molecule in dialysis patients were subtly altered and impaired its biological properties. Oxidative alterations of this major plasma protein might adversely affect its vasculoprotective effects in dialysis patients.     

Effects of Different Dialysis Modalities on Cardiac Autonomic Dysfunctions in End‐Stage Renal Disease Patients: One Year Prospective Study

Cardiac autonomic dysfunction (CAD) is a common problem in patients with end‐stage renal disease (ESRD) and may contribute to the risk of cardiac mortality. Long‐term effects of dialysis modalities on CAD in ESRD patients are not clear. In this one‐year prospective study, we studied the effects of different dialysis modalities on CAD in ESRD patients. The study consisted of 20 ESRD patients who had the indications for initiating dialysis therapy (13 hemodialysis and 7 CAPD patients) and 15 healthy controls (M/F: 5/10; age 30 ± 4). In all the subjects, first at the beginning of study (in patient groups just before initiating dialysis therapy) and then after 12 months, we studied 24 hours ECG‐Holter monitoring and heart rate variability parameters (time and frequency domain analysis parameters; SDNN: standard deviations of nn intervals, rMSSD: square root of the median of standard deviation, HRVI: heart rate variability index, LF/HF: low frequency/high frequency). In ESRD patients, before dialysis therapy, all the parameters of time domain analysis were significantly lower compared to control group (p = 0.001). In patient groups, after dialysis therapy (on the 12th month), significant improvement was observed in time domain analysis parameters (p = 0.001). When dialysis modalities were compared, the increase in the time domain analysis parameters was significantly greater in the CAPD group compared to hemodialysis (HD) group. Our findings suggest that CAD is frequent in ESRD patients, a dialysis therapy of 12 months can cause significant improvement on CAD and the ameliorative effect of CAPD is better than HD.     

A physiologic comparison of external cardiac massage techniques

On the basis of recent investigation, controversy has arisen regarding which of several cardiopulmonary resuscitation methods optimizes hemodynamics. The present study was designed to compare five recently described chest compression techniques: high-impulse manual chest compression at 150/min, mechanical compression at 60/min with simultaneous ventilation, mechanical compression at 60/min with simultaneous ventilation and either systolic or diastolic abdominal compression, and pneumatic vest compression at 60/min. Eight dogs were chronically instrumented with electromagnetic flow probes in the ascending and descending aorta while matched micromanometers measured aortic, left ventricular, and pleural pressures. At study, each dog was anesthetized with morphine, intubated, and the heart was fibrillated by rapid ventricular pacing. The five cardiopulmonary resuscitation methods were performed randomly in each preparation within 7 to 10 minutes of arrest. In four dogs, brachiocephalic blood flow was computed as total cardiac output minus descending aortic blood flow, and in all dogs coronary perfusion pressure was calculated as mean diastolic aortic pressure minus mean diastolic left ventricular pressure. Average cardiac output for seven studies was 662 +/- 61 ml/min with high-impulse manual compression, 340 +/- 46 ml/min with mechanical compression and simultaneous ventilation, 336 +/- 45 ml/min with mechanical compression and simultaneous ventilation with systolic abdominal compression, 366 +/- 52 ml/min with mechanical compression and simultaneous ventilation with diastolic abdominal compression, and 196 +/- 29 ml/min with vest resuscitation (high-impulse manual compression significantly greater than other techniques by multivariate analysis, p less than 0.05). Brachiocephalic blood flow generally followed cardiac output and was statistically the greatest with high-impulse manual compression at 273 +/- 47 ml/min (p less than 0.05). Finally, high-impulse manual compression provided the highest coronary perfusion pressure of 31 +/- 4 mm Hg (p less than 0.05) compared to 23 +/- 2 mm Hg for mechanical compression and simultaneous ventilation, 23 +/- 2 mm Hg for mechanical compression and simultaneous ventilation with systolic abdominal compression, 23 +/- 3 mm Hg for mechanical compression and simultaneous ventilation with diastolic abdominal compression, and 11 +/- 2 mm Hg for vest resuscitation. These data demonstrate that high-impulse manual compression generated physiologically and statistically superior hemodynamics when compared with other methods in this model of cardiopulmonary resuscitation.     

Surgical management of aortic valve disease in the elderly: a longitudinal analysis

From November, 1972, through December, 1986, 219 consecutive patients 70 years of age and older with aortic stenosis (AS) underwent aortic valve replacement. One hundred seven of them had isolated pure AS, and 112 had AS and coronary artery disease (AS + CAD). The mean age of the AS group was 75.4 years (range, 70 to 88 years) and of the AS + CAD group, 74.8 years (range, 70 to 86 years). The mean aortic valve gradient in the AS group was 87.7 +/- 30.6 mm Hg and in the AS + CAD group, 68.0 +/- 51.3 mm Hg (p less than 0.001). Hospital mortality for the AS group was 12.1% (13 patients) and for the AS + CAD group, 8.9% (10 patients). The long-term survival at seven years was 77.2 +/- 5.5% (+/- the standard error of the mean) for the AS group and 57.0 +/- 6.9% for the AS + CAD group (p less than 0.006). Postoperative assessment reveals substantial functional improvement. These early and long-term favorable results provide a much needed reference point when valvuloplasty is being considered. Aortic valve replacement is the treatment of choice in elderly patients with symptomatic AS.     

Reduced angiotensin receptors and pressor responses in hypotensive hemodialysis patients

A sub-set of patients on chronic hemodialysis develop sustained hypotension (systolic pressure less than 100 mm Hg). To determine whether this hypotension could be due to altered production of, or sensitivity to angiotensin II (AII), we measured plasma renin (PRA), AII, and aldosterone in nine hypotensive and nine normotensive dialysis patients; we also assessed their sensitivity to infused AII and studied AII binding to their platelets as an indicator of AII receptors on vascular smooth muscle. All studies were performed just before dialysis when subjects were relatively volume-expanded. Hypotensives had higher PRA (5.7 +/- 2.4 vs. 2.1 +/- 0.8 ng AI/ml/hr, P less than 0.05). AII (56 +/- 15 vs. 31 +/- 3 pg/ml), and aldosterone (91 +/- 35 vs. 21 +/- 7 ng/dl, P less than 0.05) than did normotensives. During AII infusion at 1, 3, 10, and 30 ng/kg/min for 15 minutes each, hypotensives displayed a significantly blunted pressor effect across the range of AII doses. In parallel with this, hypotensives showed reduced AII receptors on their platelets compared to normotensives (0.8 +/- 0.4 vs. 3.6 +/- 1.0% 125I-AII specifically bound; P less than 0.03). Binding analysis revealed a single affinity state for the AII receptors which was similar in both groups (Kd = 3.2 +/- 1.1 for hypotensives vs. 3.8 +/- 0.7 x 10(-10) M for normotensives). The two groups had similar levels of plasma catecholamines, similar slowing of heart rate during AII infusion and no postural hypotension, indicating intact sympathetic nervous system pathways.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative rest and exercise hemodynamics of 23-mm stentless versus 23-mm stented aortic bioprostheses

BACKGROUND: The hemodynamic superiority of stentless valves at rest has been generally accepted, but there is a lack of studies on exercise hemodynamics. METHODS: We assessed aortic valve hemodynamics at rest and during exercise in 10 patients with a 23-mm stentless aortic bioprosthesis (Medtronic Freestyle; Medtronic Europe SA/NV, St. Stevens Woluwe, Belgium), in 10 patients with a 23-mm stented aortic bioprosthesis (Carpentier-Edwards, SAV, model 2650; Baxter Edwards AG, Horw, Switzerland), and in 10 healthy volunteers (control group) by means of Doppler echocardiography. RESULTS: Gradients at rest and gradients on comparable maximum exercise levels were significantly lower in patients with stentless valves compared to those with stented valves (rest: 6 +/- 2/11 +/- 4 mm Hg [mean/peak] versus 12 +/- 3/21 +/- 10 mm Hg; exercise: 9 +/- 3/18 +/- 6 mm Hg [mean/peak] versus 22 +/- 8/40 +/- 11 mm Hg). Patients with stentless valves revealed, in comparison to healthy young men, significantly higher gradients, but the small gradient difference of 3/7 mm Hg (mean/peak) at rest remained nearly unchanged throughout the exercise protocol (4/8 mm Hg [mean/peak] at 25 W, 4/9 mm Hg at 50 W and 4/9 mm Hg at 75 W). In contrast, the gradient difference between patients with stented and stentless valves increased significantly from one exercise level to the next (6/12 mm Hg [mean/peak] at rest, 8/14 mm Hg at 25 W, 12/17 mm Hg at 50 W, and 15/25 mm Hg at 75 W). CONCLUSIONS: A stentless aortic bioprosthesis seems to be an appropriate aortic valve substitute, especially in patients who perform regular physical exercise.     

Effects of exsanguination and sodium nitroprusside on compliance of the spinal canal during aortic occlusion.

To evaluate the effects of sodium nitroprusside (SNP) and partial exsanguination (EXS) on systemic hemodynamics and cerebrospinal fluid dynamics, we monitored proximal and distal blood pressure (BP), cerebrospinal fluid pressure (CSFP), spinal cord perfusion pressure (SCPP), and compliance of the spinal canal (CSC) in 10 mongrel dogs during aortic cross-clamping of the descending thoracic aorta. CSC was measured by serial injections of 2 ml of saline solution into the cisterna cerebellomedullaris via a percutaneously placed catheter with simultaneous measurements of CSFP. Data were acquired at baseline (BL), during aortic cross-clamping with proximal hypertension (AXC), and after control of proximal hypertension with EXS and SNP. During the cross-clamp interval, mean proximal aortic pressure (PxBP) rose from 114 +/- 6 to 150 +/- 3 mm Hg (P less than 0.001), whereas mean blood pressure decreased to 88 +/- 5 and 82 +/- 4 mm Hg during the SNP and EXS intervals, respectively (P less than 0.05 vs BL). EXS and SNP were equally effective in controlling PxBP (82 +/- 4 vs 88 +/- 5 mm Hg, P greater than 0.05). Mean distal aortic pressure (DsBP) decreased from systemic values to 21.5 +/- 1.9 mm Hg during AXC, and to 12.4 +/- 1.0 and to 8 +/- 0.8 mm Hg during EXS and SNP, respectively (P less than 0.05 AXC vs EXS and SNP). SNP lowered DsBP significantly more than EXS, 8 +/- 0.8 vs 12.4 +/- 1.0 mm Hg (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Aortic and large artery compliance in end-stage renal failure

Pulse wave velocity (PWV) was measured in the aorta, right leg and arm of 90 control subjects (CS) and 92 hemodialysis patients (HD) of the same age and mean arterial pressure (MAP). Blood chemistry, including blood lipids, and echographic dimensions of the aorta, were measured in all subjects. Presence of aortic calcification was evaluated by abdominal X-ray and echography. Whereas femoral and brachial PWV were only slightly increased in HD (P less than 0.05), the aortic PWV was significantly elevated (1113 +/- 319 cm/sec) in comparison with CS (965 +/- 216 cm/sec; P = 0.0016). Aortic diameters were larger in HD, both at the root of aorta (32.7 +/- 4 vs. 28.2 +/- 2.8 mm; P less than 0.0001) and aortic bifurcation (16.9 +/- 3.1 vs. 14.6 +/- 2.2 mm; P less than 0.0001). Although the MAP was similar in HD (109.9 +/- 19.3 mm Hg) and CS (110.2 +/- 17.2 mm Hg), the pulse pressure was significantly increased in HD patients (76.6 +/- 23.7 vs. 63.9 +/- 22 mm Hg; P = 0.007). In the two populations, aortic PWV was found to increase with age (P less than 0.0001) and MAP (P less than 0.0001). The presence of aortic calcification showed only a borderline relationship with the increase in aortic PWV (P = 0.050 in CS and P = 0.069 in HD). As change in PWV is directly related to change in distensibility, and the aortic diameters were increased in HD, these results indicate that aortic wall compliance is decreased in HD, resulting in an increase in the pulsatile component of arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of cardiac calcinosis in hemodialysis patients by whole-body scintigraphy with 99m-technetium methylene diphosphonate

A noninvasive method for the diagnosis of cardiac calcinosis, a life-threatening complication in hemodialysis patients with end-stage renal disease (ESRD), has not, as yet, been firmly established. We tested whether whole body scanning with 99m-technetium methylene diphosphonate (MDP) might visualize cardiac calcinosis. In 19 consecutive chronic hemodialysis ESRD patients (13 males and 6 females, aged 40-81, mean 63 +/- 8 years) with cardiovascular disease [mitral annular calcinosis and/or calcified aortic valve (n = 4), hemodialysis cardiomyopathy (n = 1), coronary artery disease (n = 9) and peripheral artery atherosclerotic disease (n = 6)], MDP uptake in the heart was compared to that in 7 non-ESRD controls with hyperparathyroidism due to adenoma. Cardiac and lung field MDP uptake was confirmed in only 3 (16%) and 5 (26%) of the 19 ESRD subjects, respectively, but was absent in controls. Positive cardiac uptake was related to cardiac calcified complications (mobile intracardiac calcinosis, myocardial calcinosis and mitral annular calcification) and the duration of hemodialysis (p = 0.015). While it was statistically insignificant, subjects showing MDP uptake were elder and had higher serum Ca or Ca x P product and lower intact parathyroid hormone levels. These results suggest that cardiac calcinosis in ESRD patients can be detected noninvasively by myocardial scintigraphy with 99m-technetium MDP.     

Optimization of high-efficiency hemodialysis by detection and correction of fistula dysfunction

Recirculation studies were performed in 103 patients treated with high-efficiency dialysis over a 14 month period. Fistulograms were performed on 22 out of 25 patients with greater than 0.15 fractional recirculation at a 400 ml/minute blood pump setting. Clinically significant abnormalities were found in 82% (N = 18) and treated in 17. Two patients had second episodes of elevated recirculations and were treated again within the period of follow-up. Treatment with angioplasty (N = 11) or surgical revision (N = 8) resulted in a fall in recirculation from 0.33 +/- 0.04 to 0.12 +/- 0.02 (P = 0.001). The fractional reduction of urea clearance due to recirculation fell from 0.20 +/- 0.03 to 0.08 +/- 0.02 (P = 0.001) and the effective urea clearance of the dialysis treatment rose by 16% from 193 +/- 7 ml/min to 224 +/- 6 ml/min (P = 0.001). Pre-dialysis BUN fell from 72 +/- 4 mg/100 ml to 62 +/- 3 mg/100 ml (P = 0.012). There was no correlation between venous pressure (VP) at 400 ml/min blood pump setting and recirculation (R2 = 0.04), although VP changed significantly comparing values before and after fistula repair (211 +/- 10 vs. 186 +/- 7 mm Hg, P = 0.012). Venous pressures in 20 of the patients in our dialysis unit with recirculations of less than 0.10 were 201 +/- 6 mm Hg (P = NS compared to patients with recirculation greater than or equal to 0.15 at 400 ml/min blood flow).(ABSTRACT TRUNCATED AT 250 WORDS)