Comparative study of microvascular function: Forearm blood flow versus dynamic retinal vessel analysis.

OBJECTIVE: Recently, dynamic retinal vessel analysis (DVA) has gained interest for investigation of microvascular function but comparative measurements with standard methods like the forearm blood flow technique (FBF) are uncommon till now. METHODS: We recruited 23 high-risk cardiovascular patients (Risk) and 17 healthy persons (Ctrl). During the FBF experiment, postocclusive reactive hyperaemia (RH) as well as endothelium-dependent and independent vasodilation was measured by infusion of acetylcholine (ACh) and sodium nitroprusside (SNP) into the brachial artery. The dynamic vessel analyzer was applied for measurement of the retinal arterial and venous response to flickering light during DVA and for determination of the central retinal arterial (CRAE) and venous equivalent (CRVE). RESULTS: Forearm blood flow technique was significantly attenuated in the patient group during postocclusive RH (p < .005). The increase of FBF in response to SNP did not differ significantly between the two groups (p = .09). In contrast, the FBF response to ACh was significantly blunted in the patient group (p < .05), indicating endothelial dysfunction. DVA did not detect any difference of retinal arterial (p = .68) or retinal venous (p = .93) vasodilation between both groups. The CRAE (p = .55) and CRVE (p = .83) did not differ significantly in either group. CONCLUSIONS: Forearm blood flow and DVA cannot be regarded as equivalent methods for testing of microvascular function. Possible explanations include differences in the vascular beds and vessel diameters examined as well as differences in the trigger mechanisms applied. Further studies are needed to define the role of DVA in this context.

The Pituitary-Thyroid Axis and Prolactin Secretion in Hemodialysis Patients in Two Endemic Regions of Eastern Germany.

INTRODUCTION: Endocrine disorders of the pituitary axes are frequent in patients with hemodialysis (CKD5D). The aim of this multicenter study (Leipzig (L), Quedlinburg and Blankenburg in the Harz region (Hz)) in CKD5D patients was to evaluate influences of CKD5D related factors, morphological and biochemical parameters, and serum iodine and prolactin concentrations on the pituitary-thyroid axis. PATIENTS AND METHODS: 170 patients (L n=58; Hz n=112) were included in this prospective, non-interventional, cross-sectional study. Mann-Whitney-U-test and bivariate correlation analyses with Spearman-Rho test (r correlation coefficient) were used in statistical analysis. RESULTS: TSH was higher in patients with prolactin concentrations>370 mIU/l (p=0.013), in patients with high flux membranes (p=0.0013) and in patients with longer dialysis vintage (p=0.04). Median iodine serum concentrations were slightly elevated in the Leipzig cohort (p=0.001) and correlated with fT4 (p<0.001, r=0.43) and albumin (p=0.001, r=0.245) but not with morphological signs. Albumin was correlated with fT3 (p<0.001, r=0.339) and fT4 (p<0.001, r=0.421). Prolactin was correlated with residual excretion rate (p=0.001, r=- 0.303) and thyroid volume (p=0.027, r=0.217). CONCLUSIONS: In the assessment of the thyroid status in CKD5D patients, the synopsis of the clinical and nutritional status, comorbidities, ultrasound of the thyroid gland and laboratory results is necessary for further intervention with hormone replacement. Standardized reference values of the pituitary-thyroid axis should be critically evaluated and are still lacking in CKD5D.