|MadSci Network: Medicine|
May we quickly review the factors leading to the blood pressure regulation? Basically, blood pressure results from the interaction of two parameters. the first one is the volume of blood in the vessels (it is called volhemia), the second is the vascular tone (when increased, the arteries are narrowed, and the pressure inside increases). Regarding diabetes, you are right in stating that an elevation of sugar level in the blood increases the osmolarity. But this leads to the opposite. When osmolarity increases, the kidney lets more fluid escape (urine output is greater), and this leads to dehydratation and eventually shock with a drop in the blood pressure. This is a basic regulation of volhemia, and kidney regulation is a very strong one (try drinking one liter of water, you will not undergo headhache, a symptom of high blood pressure, I guess you will quickly need a quiet place...). But diabetic people have an impairement on their blood pressure, and especially what we call orthostatic hypotension, i.e. a marked drop in arterial blood pressure when you sit up. This impairement is due to a nervous disease (we call it diabetic neuropathia) generated by a chronic elevated arterial sugar level. Hope this helps Luc A. Ronchi, MD Ped Anesthesia Hopital de Saint Nazaire, France
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