Alastair Gillies

Barriers to Timely Arteriovenous Fistula Creation: A Study of Providers and Patients

BACKGROUND Current clinical practice guidelines recommend a native arteriovenous fistula (AVF) as the vascular access of first choice. Despite this, most patients in western countries start hemodialysis therapy using a catheter. Little is known regarding specific physician and system characteristics that may be responsible for delays in permanent access creation. STUDY DESIGN Multicenter cohort study using mixed methods; qualitative and quantitative analysis. SETTING & PARTICIPANTS 9 nephrology centers in Australia and New Zealand, including 319 adult incident hemodialysis patients. PREDICTOR Identification of barriers and enablers to AVF placement. OUTCOMES Type of vascular access used at the start of hemodialysis therapy. MEASUREMENTS Prospective data collection included data concerning predialysis education, interviews of center staff, referral times, and estimated glomerular filtration rate (eGFR) at AVF creation and dialysis therapy start. RESULTS 319 patients started hemodialysis therapy during the 6-month period, 39% with an AVF and 59% with a catheter. Perceived barriers to access creation included lack of formal policies for patient referral, long wait times for surgical review and access placement, and lack of a patient database for management purposes. eGFR thresholds at referral for and creation of vascular accesses were considerably lower than appreciated (in both cases, median eGFR of 7 mL/min/1.73 m(2)), with median wait times for access creation of only 3.7 weeks. First assessment by a nephrologist less than 12 months before dialysis therapy start was an independent predictor of catheter use (OR, 8.71; P < 0.001). Characteristics of the best performing centers included the presence of a formalized predialysis pathway with a centralized patient database and low nephrologist and surgeon to patient ratios. LIMITATIONS A limited number of patient-based barriers was assessed. Cross-sectional data only. CONCLUSIONS A formalized predialysis pathway including patient education and eGFR thresholds for access placement is associated with improved permanent vascular access placement.

Arm position and blood pressure: a risk factor for hypertension?

The objective of this study was to re-evaluate the effect of arm position on blood pressure (BP) measurement with auscultatory and oscillometric methods including ambulatory blood pressure monitoring (ABPM). The setting was the hospital outpatient department and the subjects chosen were normotensive and hypertensive. The effect of lowering the arm from heart level on indirect systolic BP (SBP) and diastolic BP (DBP) measurement as well as the importance of supporting the horizontal arm were measured. In the sitting position, lowering the supported horizontal arm to the dependent position increased BP measured by a mercury device from 103±10/60±7 to 111±14/67±10 mmHg in normotensive subjects, a mean increase of 8/7 mmHg (P<0.01). In hypertensive subjects, a similar manoeuvre increased BP from 143±21/78±17 to 166±29/88±20 mmHg, an increase of 23/10 mmHg (P<0.01). Combined results from normotensive and hypertensive subjects demonstrate a direct and proportional association between BP (SBP and DBP) and the increase produced by arm dependency. Similar changes and associations were noted with oscillometric devices in the clinic situation. However, supporting the horizontal arm did not alter BP. Of particular interest, analysis of 13 hypertensive subjects who underwent ABPM on two occasions, once with the arm in the ‘usual’ position and once with the arm held horizontally for BP measurement during waking hours, demonstrated changes comparable to the other devices. The mean 12-hour BP was 154±19/82±10 mmHg during the former period and significantly decreased to 141±18/74±9 mmHg during the latter period (P<0.01). Regression analysis of the change in SBP and DBP with arm position change again demonstrated a close correlation (r2=0.8113 and 0.7273; P<0.001) with the artefact being larger with higher systolic and diastolic pressures. In conclusion, arm movements lead to significant artefacts in BP measurement, which are greater, the higher the systolic or diastolic pressure. These systematic errors occur when using both auscultatory and oscillometric (clinic and ABPM) devices and might lead to an erroneous diagnosis of hypertension and unnecessary medication, particularly in individuals with high normal BP levels. Since clinical interpretations of heart level vary, the horizontal arm position should be the unambiguous standard for all sitting and standing BP auscultatory and oscillometric measurements.

Better Management of Cardiovascular Diseases by Pulse Wave Velocity: Combining Clinical Practice with Clinical Research using Evidence-Based Medicine

Arterial stiffness measured by pulse wave velocity (PWV) is an accepted strong, independent predictor of cardiovascular events and mortality. However, lack of a reliable reference range has limited its use in clinical practice. In this evidence-based review, we applied published data to develop a PWV risk stratification model and demonstrated its impact on the management of common clinical scenarios. After reviewing 97 studies where PWV was measured, 5 end-stage renal disease patients, 5 hypertensives, 2 diabetics, and 2 elderly studies were selected. Pooling the data by the “fixed-effect model” demonstrated that the mortality and cardiovascular event risk ratio for one level increment in PWV was 2.41 (1.81–3.20) or 1.69 (1.35–2.11), respectively. There was a significant difference in PWV between survived and deceased groups, both in the low and high risk populations. Furthermore, risk comparison demonstrated that 1 standard deviation increment in PWV is equivalent to 10 years of aging, or 1.5 to 2 times the risk of a 10 mmHg increase in systolic blood pressure. Evidence shows that PWV can be beneficially used in clinical practice for cardiovascular risk stratification. Furthermore, the above risk estimates could be incorporated into currently used cardiac risk scores to improve their predictive power and facilitate the clinical application of PWV.

Inaccuracy of wrist-cuff oscillometric blood pressure devices: an arm position artefact?

BackgroundDespite the increasing popularity of wrist-cuff blood pressure (BP) devices, their accuracy has not been established and international guidelines do not support their use. Because arm position influences BP measurement, it is possible that conflicting reports on wrist-cuff device accuracy reflects diverse arm positions. MethodThis study compared BP measured by two oscillometric devices, the upper arm-cuff OMRON HEM 705 CP and the OMRON R6 oscillometric wrist-cuff device. In the former BP was measured with the arm in two supported positions, dependent on a table (manufacturers instructions) and horizontal (mid sternum), while the latter followed the manufacturers instructions. ResultsIn contrast to the dependent arm where BP was significantly higher (P<0.05), the horizontal arm position with the arm-cuff produced a mean systolic and diastolic BP comparable to the wrist-cuff device where the wrist was at heart level being respectively, 137±29/80±16 and 134±27/77±16 mmHg. A close relationship over a wide BP range was also confirmed by least squares, least product linear regression and Bland–Altman analysis. ConclusionThis study supports the use of wrist-cuff monitors for self/home use and underlines the need for a more precise definition for arm position when using all BP devices – mercury and oscillometric.

Potential roles of erythropoietin in the management of anaemia and other complications diabetes

Erythropoietin (EPO) is a haematopoietic cytokine, mainly generated in the renal cortex, and its secretion and action is impaired in chronic kidney disease (CKD). Early renal damage in diabetes mellitus (DM) is usually not detected because diabetes‐induced nephron hypertrophy maintains glomerular filtration rate (GFR) and an elevated plasma creatinine concentration is a relatively late manifestation of diabetic nephropathy. However, anaemia occurs more frequently in subjects with DM when compared with those with non‐DM renal disease. While reduced production and a blunted response to EPO occurs in DM with early renal damage, other factors including chronic inflammation, autonomic neuropathy and iron deficiency are also important. Although recombinant human erythropoietin (rhEPO) has been an effective therapeutic agent in CKD anaemia, it appears to be more effective in patients with DM, even in earlier stages. Nevertheless, patients with DM are also more likely to be iron deficient, a barrier to effective rhEPO therapy. The effect of treatment on the reliability of haemoglobin A1c as an index of glycaemic control must be remembered. It is proposed that anaemia and its causes must be important components of care in subjects with early diabetic renal damage.

Circulatory Syndrome: An Evolution of the Metabolic Syndrome Concept!

The metabolic syndrome has been a useful, though controversial construct in clinical practice as well as a valuable model in order to understand the interactions of diverse cardiovascular risk factors. However the increasing importance of the circulatory system in particular the endothelium, in both connecting and controlling organ function has underlined the limitations of the metabolic syndrome definition. The proposed “Circulatory Syndrome” is an attempt to refine the metabolic syndrome concept by the addition of recently documented markers of cardiovascular disease including renal impairment, microalbuminuria, arterial stiffness, ventricular dysfunction and anaemia to more classic factors including hypertension, dyslipidemia and abnormal glucose metabolism; all of which easily measured in clinical practice. These markers interact with each other as well as with other factors such as aging, obesity, physical inactivity, diet and smoking. The final common pathways of inflammation, oxidative stress and hypercoagulability thereby lead to endothelial damage and eventually cardiovascular disease. Nevertheless, the Circulatory (MARC) Syndrome, like its predecessor the metabolic syndrome, is only a small step toward an understanding of these complex and as yet poorly understood markers of disease.

Pro-haemorrhagic effects of calcium antagonists : a comparison of isradipine and atenolol on ex vivo platelet function in hypertensive subjects

It has been suggested that long term treatment with calcium antagonist drugs might inhibit platelet function and lead to an anti-atheromatous effect. However recent data have also suggested that such an effect might increase mortality due to an increased incidence of gastrointestinal bleeding. We identified 43 subjects from general practice with uncomplicated mild to moderate hypertension to compare the effects of the calcium antagonist isradipine with that of the β-blocker atenolol on platelet function, plasma β-thromboglobulin levels, fibrinolysis, and serum lipids in a randomised double-blind parallel group study. After careful evaluation to exclude concomitant aspirin use, only 24 subjects were eligible to enter the study. While isradipine and atenolol produced comparable and clinically significant falls in blood pressure (167 ± 2 /102 ± 1 to 153 ± 3/91 ± 2 mm Hg, and 165 ± 2/101 ± 1 to 156 ± 4/91 ± 2 mm Hg, respectively), neither drug produced a detectable effect on ex vivo platelet aggregation, platelet retention, or thromboxane generation with adrenaline, collagen, adenosine- di-phosphate, or platelet activating factor. However a decrease in plasma β-thromboglobulin levels was observed which reached statistical significance (P < 0.05) after 12 weeks treatment in the isradipine but not the atenolol group. a 39% reduction with isradipine compared with 34% following atenolol treatment. euglobulin clot lysis time was not altered by either drug. serum cholesterol concentrations were also unaltered by drug treatment. therapeutic doses of the calcium antagonist isradipine may produce a minor indirect effect on platelet function after several weeks of treatment. however, this is of doubtful clinical importance and may simply reflect an effect of lowered blood pressure on platelet function.

ACUTE EFFECT OF ETHANOL ON RENAL ELECTROLYTE TRANSPORT IN THE RAT

1. Despite human and animal studies, the direct effect of ethanol on renal water and electrolyte transport is poorly understood. The acute effect of increasing plasma concentrations of ethanol was evaluated in a water diuretic anaesthetized rat model which inhibits endogenous arginine vaso‐pressin (AVP) release.

Hypertension and asthma: Psychological aspects

Essential hypertensive and asthmatic patients, plus normal non-clinical controls, were compared on a number of psychological measures in order to identify the relationship between psychological distress, coping strategies and compliance behaviour. The hypothesised relationship between chronic clinical ailments and psychological distress was confirmed. The association between the presence of physical symptoms in the symptomatic condition, asthma, and greater psychological distress was also confirmed. The coping strategies adopted by the patients did not discriminate between the two clinical groups. Compliance with medication was negatively correlated with measures of psychological distress. Compliance with an appropriate healthy lifestyle was not correlated with medication compliance, although it too was negatively correlated with other measures of psychological distress.

Increased Dietary Sodium Chloride in Patients Treated with Antihypertensive Drugs

Eleven patients on a normal diet with mild to moderate essential hypertension satisfactorily treated with diverse hypotensive agents entered a randomized double-blind cross-over study to evaluate the effect of additional sodium chloride (100 mmol slow sodium) compared with placebo on blood pressure control over a 6 week period. Despite excellent tablet compliance, sodium chloride failed to significantly alter mean supine or erect blood pressure. These findings as well as a review of the relevant literature suggest that excess dietary sodium does not jeopardize blood pressure control in such patients.