enalapril and Dehydration

Renovascular hypertension is an unusual cause of elevated mean arterial pressure in children. When suspected, angiotensin-converting enzyme inhibitor-enhanced renal scintigraphy is usually one of the initial studies done to evaluate patients. The accuracy of this test depends not only on patient selection but also on technical factors involved in performing the study. We report a case of a false-positive angiotensin-converting enzyme inhibitor-enhanced radionuclide renogram in a 5-year-old boy with hypertension.. Angiotensin-converting enzyme inhibitor-enhanced renal scintigraphy was performed and the result was interpreted as positive for bilateral renovascular disease. A review of the anesthesia record from the study revealed that the patient was hypotensive. A repeated study with adequate hydration and blood pressure stability was then done.. The result of the second examination was interpreted as normal, without evidence of abnormal renovascular physiology.. The cause of the initial false-positive result was determined to be dehydration with secondary hypotension. Dehydration, with secondary hypotension, can cause a diminished glomerular filtration rate and mimic bilateral renovascular physiology on angiotensin-converting enzyme inhibitor-enhanced renal scans.

Topics: Anesthesia, General; Angiotensin-Converting Enzyme Inhibitors; Antihypertensive Agents; Blood Pressure; Captopril; Child, Preschool; Dehydration; Diagnosis, Differential; Enalapril; False Positive Reactions; Fluid Therapy; Glomerular Filtration Rate; Humans; Hypertension, Renovascular; Hypnotics and Sedatives; Hypotension; Kidney; Male; Radionuclide Imaging; Radiopharmaceuticals; Technetium Tc 99m Mertiatide

Studies on vasoactive intestinal peptide (VIP) in the anterior pituitary gland have shown that it is synthesized locally, physiologically regulated, and may act as a paracrine/autocrine factor. We have now investigated the regulation of anterior pituitary VIP gene expression in rats during osmotic stimulation. Both salt-loading and dehydration resulted in a progressive and marked reduction in VIP mRNA levels as determined by Northern analysis, to 10% of control levels at 14 days of salt-loading. The 1.7 and 1.0 kb VIP RNA transcripts were equally affected. Since anterior pituitary VIP is partially localized in lactotrophs we also measured prolactin (PRL) mRNA levels. In contrast to VIP, PRL mRNA levels were increased during both osmotic paradigms, the mRNA levels being significantly raised after 5 days of salt-loading to 130% of controls. Further experiments, conducted to examine the mechanism by which VIP gene expression is down-regulated during osmotic stimulation, demonstrated that dopamine and angiotensin II do not appear to be involved. The results show dissociated regulation of VIP and PRL during osmotic stimulation and provide suggestive evidence of a role for anterior pituitary VIP in the animal's osmoregulatory responses. VIP may therefore be a paracrine factor with diverse functional roles.

Topics: Angiotensin II; Animals; Dehydration; Enalapril; Gene Expression Regulation; Male; Osmotic Pressure; Pituitary Gland, Anterior; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sodium Chloride; Vasoactive Intestinal Peptide; Water-Electrolyte Balance

Three patients are described in whom haemodynamic collapse and acute renal failure occurred following intercurrent gastrointestinal fluid loss during treatment with an angiotensin converting-enzyme inhibitor. The possible consequences of blockade of the formation of angiotensin II during fluid loss are discussed.

Topics: Acute Kidney Injury; Aged; Angiotensin-Converting Enzyme Inhibitors; Captopril; Dehydration; Diarrhea; Enalapril; Hemodynamics; Humans; Male; Middle Aged

The role of vasopressin, the renin system, and sympathetic activity in sustaining blood pressure in the dehydrated state was investigated in normotensive nonanesthetized male Wistar rats. After 48-h dehydration, plasma arginine vasopressin was 14.0 +/- 1.7 pg/ml and plasma norepinephrine 0.46 +/- 0.05 ng/ml. In another group of rats in which the angiotensin converting enzyme inhibitor (MK 421, 5 mg po twice daily) was administered throughout the dehydration period, blood pressure was reduced by more than 20% (P less than 0.001), and both plasma arginine vasopressin and norepinephrine were higher at 23.4 +/- 3.9 pg/ml (P less than 0.01) and 0.83 +/- 0.07 ng/ml (P less than 0.01), respectively. Taken together, in rats with or without converting enzyme blockade, there was an inverse correlation between mean blood pressure and plasma arginine vasopressin (r = 0.67, P less than 0.01) as well as plasma norepinephrine (r = 0.82, P less than 0.01) levels. The acute administration of a specific vasopressin pressor inhibitor (dPVDAVP) reduced mean blood pressure in the rats with a blocked renin system by 16.9 mmHg (P less than 0.001). In rats without converting enzyme inhibition, the induced fall was only 6.4 mmHg. These results indicate that following 48-h dehydration the renin angiotensin system interacts with the vasopressin secretory mechanism to sustain blood pressure, with renin playing a predominant role. They further suggest that, following blockade of the renin system, activation of the sympathetic nervous system probably also contributes to blood pressure maintenance.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Arginine Vasopressin; Blood Pressure; Dehydration; Dipeptides; Enalapril; Epinephrine; Heart Rate; Lypressin; Male; Norepinephrine; Peptidyl-Dipeptidase A; Rats; Rats, Inbred Strains; Renin; Wakefulness

Topics: Angiotensin I; Angiotensin II; Animals; Blood Pressure; Dehydration; Dipeptides; Dose-Response Relationship, Drug; Drinking; Enalapril; Estrus; Female; Heart Rate; Isoproterenol; Pregnancy; Rats; Rats, Inbred Strains; Saline Solution, Hypertonic