Robert W. Nette

Preload Dependence of New Doppler Techniques Limits Their Utility for Left Ventricular Diastolic Function Assessment in Hemodialysis Patients

Left ventricular (LV) hypertrophy leads to diastolic dysfunction. Standard Doppler transmitral and pulmonary vein (PV) flow velocity measurements are preload dependent. New techniques such as mitral annulus velocity by Doppler tissue imaging (DTI) and LV inflow propagation velocity measured from color M-mode have been proposed as relatively preload-independent measurements of diastolic function. These parameters were studied before and after hemodialysis (HD) with ultrafiltration to test their potential advantage for LV diastolic function assessment in HD patients. Ten patients (seven with LV hypertrophy) underwent Doppler echocardiography 1 h before, 1 h after, and 1 d after HD. Early (E) and atrial (A) peak transmitral flow velocities, peak PV systolic (s) and diastolic (d) flow velocities, peak e and a mitral annulus velocities in DTI, and early diastolic LV flow propagation velocity (V(p)) were measured. In all patients, the E/A ratio after HD (0.54; 0.37 to 1.02) was lower (P < 0.01) than before HD (0.77; 0.60 to 1.34). E decreased (P < 0.01), whereas A did not. PV s/d after HD (2.15; 1.08 to 3.90) was higher (P < 0.01) than before HD (1.80; 1.25 to 2.68). Tissue e/a after HD (0.40; 0.26 to 0.96) was lower (P < 0.01) than before HD (0.56; 0.40 to 1.05). Tissue e decreased (P < 0.02), whereas a did not. V(p) after HD (30 cm/s; 16 to 47 cm/s) was lower (P < 0.01) than before HD (45 cm/s; 32 to 60 cm/s). Twenty-four hours after the initial measurements values for E/A (0.59; 0.37 to 1.23), PV s/d (1.85; 1.07 to 3.38), e/a (0.41; 0.27 to 1.06), and V(p) (28 cm/s; 23 to 33 cm/s) were similar as those taken 1 h after HD. It is concluded that, even when using the newer Doppler techniques DTI and color M-mode, pseudonormalization, which was due to volume overload before HD, resulted in underestimation of the degree of diastolic dysfunction. Therefore, the advantage of these techniques over conventional parameters for the assessment of LV diastolic function in HD patients is limited. Assessment of LV diastolic function should not be performed shortly before HD, and its time relation to HD is essential.

Ultrafiltration improves aortic compliance in haemodialysis patients.

An elevated pulse pressure leads to an increased pulsatile cardiac load, and results from arterial stiffening. The aim of our study was to test whether a reduction in volume overload by ultrafiltration (UF) during haemodialysis (HD) leads to an improvement of aortic compliance. In 18 patients, aortic compliance was estimated noninvasively before and after HD with UF using a pulse pressure method based on the Windkessel model. This technique has not been applied before in a dialysis population, and combines carotid pulse contour analysis by applanation tonometry with aortic outflow measurements by Doppler echocardiography. The median UF volume was 2450 ml (range 1000–4000 ml). The aortic outflow volume after HD (39 ml; 32–53 ml) was lower (P=0.01) than before (46 ml; 29–60 ml). Carotid pulse pressure after HD (42 mmHg; 25–85 mmHg) was lower (P=0.01) than before (46 mmHg; 35–93 mmHg). Carotid augmentation index after HD (22%; 3–30%) was lower (P=0.001) than before (31%; 7–53%). Carotid–femoral pulse wave velocity was not different after HD (8.7 m/s; 5.6–28.9 m/s vs 7.7 m/s; 4.7–36.8 m/s). Aortic compliance after HD (1.10 ml/mmHg; 0.60–2.43 ml/mmHg) was higher (P=0.02) than before (1.05 ml/mmHg; 0.45–1.69 ml/mmHg). The increase in aortic stiffness in HD patients is partly caused by a reversible reduction of aortic compliance due to volume expansion. Volume withdrawal by HD moves the arterial wall characteristics back to a more favourable position on the nonlinear pressure–volume curve, reflected in a concomitant decrease in arterial pressure and improved aortic compliance.

A psychometric analysis of the Rotterdam Renal Replacement Knowledge-Test (R3K-T) using item response theory

Knowledge is a prerequisite for promoting well‐informed decision‐making. Nevertheless, there is no validated and standardized test to assess the level of knowledge among renal patients regarding kidney disease and all treatment options. Therefore, the objective of this study was to investigate the psychometric properties of such a questionnaire for use in research and practice. A 30‐item list was validated in four groups: (1) 187 patients on dialysis, (2) 82 patients who were undergoing living donor kidney transplantation the following day, (3) the general population of Dutch residents (n = 515) and (4) North American residents (n = 550). The psychometric properties of the questionnaire were examined using multidimensional item response theory (MIRT). Norm references were also calculated. Five items were found to distort ability estimates (Differential item functioning; DIF). MIRT analyses were subsequently carried out for the remaining 25 items. Almost all items showed good discrimination and difficulty parameters based on the fitted model. Two stable dimensions with 21 items were retrieved for which norm references for the Dutch and North American, dialysis and transplantation groups were calculated. This study resulted in a thorough questionnaire, the Rotterdam renal replacement knowledge‐test, which enables reliable testing of patients knowledge on kidney disease and treatment options in clinic and research.

Justification for a home-based education programme for kidney patients and their social network prior to initiation of renal replacement therapy

In this article, an ethical analysis of an educational programme on renal replacement therapy options for patients and their social network is presented. The two main spearheads of this approach are: (1) offering an educational programme on all renal replacement therapy options ahead of treatment requirement and (2) a home-based approach involving the family and friends of the patient. Arguments are offered for the ethical justification of this approach by considering the viewpoint of the various stakeholders involved. Finally, reflecting on these ethical considerations, essential conditions for carrying out such a programme are outlined. The goal is to develop an ethically justified and responsible educational programme.

Hemodynamic response to lower body negative pressure in hemodialysis patients

BACKGROUND Hypovolemia is thought to have an important role in the pathogenesis of dialysis-related hypotension. METHODS We studied the effect of hypovolemia simulated by lower body negative pressure (LBNP) in 11 hypotension-prone (HP) and 11 hypotension-resistant (HR) hemodialysis patients. LBNP was applied stepwise from 0 to -20 to -40 mm Hg. Systolic arterial pressure, heart rate, and central venous pressure (CVP) were recorded continuously after cannulation of the right jugular vein. Stroke volume index was measured at each step echocardiographically. At the end of each level of LBNP, blood samples were obtained to measure norepinephrine (NE), epinephrine (E), and atrial natriuretic peptide (ANP) levels. RESULTS At baseline, CVP (12 +/- 5 and 16 +/- 7 mm Hg), heart rate (72 +/- 9 and 70 +/- 13 beats/min), cardiac index (2.3 +/- 0.6 and 2.5 +/- 0.9 L/min), NE (median, 341 pg/mL [range,198 to 789 pg/mL] and 365 pg/mL [range, 177 to 675 pg/mL] or 2.02 nmol/L [range, 1.17 to 4.66 nmol/L] and 2.16 nmol/L [range, 1.05 to 4.00 nmol/L]), E (median, 46 pg/mL [range, 18 to 339 pg/mL] and 58 pg/mL [range, 21 to 122 pg/mL] or 251 pmol/L [range, 98 to 1,951 pmol/L] and 317 pmol/L [range, 115 to 666 pmol/L]) were similar, whereas systolic arterial pressure (141 +/- 26 versus 164 +/- 22 mm Hg) and ANP (median, 441 pg/mL [range, 152 to 1,330 pg/mL] versus 804 pg/mL [range, 517 to 3,560 pg/mL] ng/L) were lower (P < 0.05) in HP patients. In response to LBNP (-40 mm Hg), CVP decreased by 6.5 +/- 4.0 mm Hg in the HP group and 4.9 +/- 4.9 mm Hg in the HR group. In HP patients, this decrease was associated with a greater decrease in SI (37% +/- 16% versus 27% +/- 16%) and systolic arterial pressure (19% +/- 21% versus 4% +/- 14%) than in HR patients. Plasma ANP levels did not change, whereas increases in NE and E levels were similar in HP and HR patients. CONCLUSION Patients who frequently experience episodes of hypotension during dialysis also are prone to develop hypotension during LBNP, which results from reduced myocardial contractile reserve and/or inadequate sympathetic tone.

Increase in Blood Volume during Dialysis without Ultrafiltration

Combined dialysis and ultrafiltration leads to more frequent episodes of hypotension than isolated ultrafiltration. It has been suggested that decreased plasma volume preservation could be responsible for this phenomenon. The present study evaluates the effects of diffusive dialysis on the changes in relative blood volume (RBV). Six stable hemodialysis patients, without the need of ultrafiltration, were studied during 10 sessions of diffusive dialysis (bicarbonate) lasting 4 h. RBV was monitored continuously by measurement of hematocrit. During the 1st and 2nd h RBV increased by 2.4 ± 1.4 and 2.5 ± 0.8% respectively, returning to baseline levels at the end of dialysis. No changes in blood pressure or heart rate were noted. We conclude that during diffusive dialysis without ultrafiltration RBV is increased. A decrease in vascular resistance, or changes in regional blood distribution could explain these findings.