Diffusion model for iontophoresis measured by laser-Doppler perfusion flowmetry, applied to normal and preeclamptic pregnancies

We present a physical model to describe iontophoresis time recordings. The model is a combination of monodimensional material diffusion and decay, probably due to transport by blood flow. It has four adjustable parameters, the diffusion coefficient, the decay constant, the height of the response, and the shot saturation constant, a parameter representing the relative importance of subsequent shots (in case of saturation). We test the model with measurements of blood perfusion in the capillary bed of the fingers of women who recently had preeclampsia and in women with a history of normal pregnancy. From the fits to the measurements, we conclude that the model provides a useful physical description of the iontophoresis process. (c) 2007 Society of Photo-Optical Instrumentation Engineers.</p

(Micro) vascular changes in preeclampsia

De ernstige zwangerschapscomplicatie pre-eclampsie, vroeger ook wel zwangerschaps­vergiftiging genoemd, blijft wereldwijd een van de belangrijkste oorzaken van ziekte en sterfte van zowel moeder als kind. Vrouwen die pre-eclampsie hebben doorgemaakt, hebben op latere leeftijd een hogere kans op hoge bloeddruk, obesitas-metabool syndroom en hart- en vaatziekten.Er zijn sterke aanwijzingen dat een veranderde vaatfunctie van de moeder, mogelijk als gevolg van een slecht functionerend endotheel (binnenbekleding van de vaatwand), een belangrijke rol speelt bij het ontstaan van pre-eclampsie. Promovendus Judith Blaauw onderzocht welke veranderingen in vaatfunctie er precies optreden. Uit het onderzoek blijkt onder meer dat zowel endotheel-afhankelijke als endotheel-onafhankelijke vaatverwijding verschilt tussen vrouwen met een ernstige, vroege pre-eclampsie en vrouwen met een normale zwangerschap. Ook constateerde Blaauw bij vrouwen die recent een vroege pre-eclampsie hebben gehad, meerdere factoren die kunnen bijdragen aan een versnelling van het proces van aderverkalking. Blaauw pleit voor nader onderzoek, zodat in de toekomst hoogrisico patiënten beter opgespoord kunnen worden en gerichte preventieve maatregelen kunnen worden genomen.

Abnormal endothelium-dependent microvascular dilator reactivity in pregnancies complicated by normotensive intrauterine growth restriction

OBJECTIVE: Normotensive intrauterine growth restriction and preeclampsia share a similar placenta pathophysiology, whereas maternal clinical manifestations differ. Clinical symptoms of preeclampsia are partly attributed to vascular endothelial dysfunction, but it is unclear whether this phenomenon plays a role in intrauterine growth restriction. Therefore, we investigated microvascular endothelial function in women with intrauterine growth restriction. STUDY DESIGN: Laser Doppler fluxmetry was used combined with iontophoresis of acetylcholine and sodium nitroprusside, namely, endothelium-dependent and endothelium-independent vasodilators. We studied 12 women with intrauterine growth restriction and 16 controls in the third trimester of pregnancy. All women had prepregnancy body mass indexes .99). CONCLUSION: Nonobese women with normotensive intrauterine growth restriction show abnormal endothelium-dependent microvascular vasodilatation, suggesting endothelial dysfunction as in preeclampsia. Obviously, for the clinical manifestation of preeclampsia additional factors are required, and a role of metabolic syndrome and obesity has been suggested

Time Development Models for Perfusion Provocations Studied with Laser-Doppler Flowmetry, Applied to Iontophoresis and PORH

Objective: Clinical acceptance of laser-Doppler perfusion monitoring (LDPM) of microcirculation suffers from lack of quantitatively reliable signal data, due to varying tissue constitution, temperature, hydration, etc. In this article, we show that a novel approach using physiological models for response upon provacations provides quantitatively and clinically relevant time constants. Methods: We investigated this for two provocation protocols: postocclusive reactive hyperemia (PORH) and iontophoresis shots, measured with LDPM on extremities. PORH experiments were performed on patients with peripheral arterial occlusive disease (PAOD) or diabetes mellitus (DM), and on healthy controls. Iontophoresis experiments were performed on pre-eclamptic patients and healthy controls. We developed two dynamical physical models, both based on two characteristic time constants: for PORH, an "arterial" and a "capillary" time constant and, for iontophoresis, a "diffusion" and a "decay" time constant. Results: For the different subject groups, we could extract time constants that could probably be related to physiological differences. For iontophoresis, a shot saturation constant was determined, with very different values for different groups and administered drugs. Conclusions: With these models, the dynamics of the provocations can be investigated and quantitative comparisons between experiments and subject groups become available. The models offer a quantifiable standard that is independent of the type of LDPM instrumentation. Microcirculation (2009) 16, 559-571. doi:10.1080/1073968090295610