PubMed Health⌕ Search

Biomedical subjects

C van Guldener

Publications and source records attributed to C van Guldener.

At least 19 recordsLinked to original sources
PubMed2002

[Sudden death following a single oral administration of haloperidol].

A 39-year-old man was admitted with myasthenia, alcoholic hepatitis and electrolyte abnormalities due to an inadequate nutritional state. On admission the ECG showed a prolonged QTc interval (0.46 s). The patient was treated with intravenous fluid and supplementary vitamins and minerals. On the third day of admission the patient developed a delirium, partly due to alcohol withdrawal, and was therefore treated with oxazepam 50 mg 3 times daily and a single dose of haloperidol 5 mg. One hour after ingesting haloperidol, the patient suddenly succumbed and resuscitation was not successful. The autopsy revealed a cardiomyopathy but no explanation for the sudden death. Due to the temporal relationship between the ingestion of haloperidol and this sudden death, we assume that haloperidol induced a fatal arrhythmia in the presence of a preexisting prolonged repolarisation time. To the best of our knowledge, sudden death after a single oral therapeutic dose of haloperidol has not previously been described.

Administration, Oral↗
PubMed2001

Intravascular hemolysis by IgA red cell autoantibodies.

A 66-year-old male patient with severe intravascular hemolysis is presented. Laboratory investigation revealed initially a negative direct antiglobulin test (DAT), suggesting a Coombs-negative hemolytic anemia. Additional testing with monospecific anti-IgA was strongly positive. IgA autoantibodies with anti-e specificity and nonspecific IgA autoantibodies were identified. A diagnosis of IgA-only-associated warm AIHA was made. Treatment included transfusion of multiple e-negative typed red cell concentrates and administration of high-dose prednisone. The pathophysiologic mechanism of the rare IgA-induced warm AIHA is discussed.

Aged↗
PubMed2001

Homocysteine metabolism in renal failure.

Of the many amino acid abnormalities that are present in chronic renal failure, hyperhomocysteinemia has drawn increasing attention because of its proposed role in the development and/or progression of atherothrombotic disease. Renal function is a major determinant of fasting plasma homocysteine level, and the inverse relationship between the glomerular filtration rate (GFR) and plasma homocysteine level is present throughout the whole range of renal function. Although this suggests an active renal homocysteine metabolism, no important urinary excretion or active homocysteine extraction has been demonstrated in the human kidney. Analysis of plasma concentrations of the various cofactors and substrates of homocysteine metabolism, and the effects of different therapies indicate that an abnormal folate metabolism may be the cause of hyperhomocysteinemia in uremia. This is further supported by the finding that homocysteine remethylation, as assessed by stable isotope techniques, is impaired in dialysis patients. It is unclear whether decreased remethylation is also responsible for other abnormalities of homocysteine metabolism in renal failure such as the exaggerated rise and the impaired decline of plasma homocysteine concentration after methionine or homocysteine loading. More studies are necessary to pinpoint the precise mechanisms that lead to hyperhomocysteinemia in renal failure. This should lead to optimal treatment and, ultimately, to the prevention of cardiovascular complications in this vulnerable patient group.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗
PubMed2001

Homocysteine-lowering treatment: an overview.

Elevated fasting plasma concentrations of homocysteine have a high prevalence in subjects with cardiovascular disease and have also been associated with an increased risk of atherothrombosis in most, but not all, prospective studies. The most frequent causes of hyperhomocysteinaemia are genetic defects, such as cystathionine-beta-synthase (CBS) deficiency, deficiencies of folic acid and/or vitamin B12, renal failure and interference in homocysteine metabolism by drugs or metabolic alterations. In most cases, no underlying cause can be established. Subjects with CBS deficiency are treated with pyridoxine with additional folic acid and betaine if necessary. Folic acid and vitamin B12 deficiencies should be corrected by supplementation. Increases in folate intake by dietary changes or fortification can also lower plasma homocysteine in vitamin-replete subjects with normal plasma homocysteine levels. In renal failure, folic acid treatment (1-5 mg/day) ameliorates the plasma homocysteine level in most cases but hyperhomocysteinaemia persists in the majority of patients. Primary (fasting) hyperhomocysteinaemia can be treated with folic acid (0.5-5 mg/day). An abnormal methionine-loading test identifies additional patients at risk and postmethionine-loading hyperhomocysteinaemia should be treated with a combination of pyridoxine and folic acid. In the absence of dose-effect studies, a combination of pyridoxine (50 mg) and folic acid (5 mg) is advised. Large clinical trials are currently underway to establish the role of homocysteine-lowering therapy in the secondary prevention of atherothrombotic disease. In view of the effective, cheap and safe character of therapy with folic acid and pyridoxine, a policy can be accepted to screen and treat high-risk patients until these trials have been concluded.

Animals↗
PubMed2000

[Fever of unknown origin caused by the adult form of Still's disease].

In three patients, two women aged 70 and 19 years and a man aged 33 years with long-lasting fever no diagnosis was made after extensive diagnostic work-up. After exclusion of infectious, malignant and rheumatic diseases, adult-onset Still's disease was diagnosed in all three patients on the basis of clinical and laboratory criteria. Adult-onset Still's disease is an important but less well known cause of fever. Clinically, adult-onset Still's disease is characterized by the triad of fever, skin rash and arthritis/arthralgia. A greatly elevated serum ferritin level proved to be an additional valuable diagnostic clue. Treatment consists of non-steroidal anti-inflammatory drugs, corticosteroids or immunosuppressive agents. The long-term prognosis is usually good, but severe joint destruction may occur. All three patients recovered.

Adult↗
PubMed2000

Homocysteine and renal disease.

Hyperhomocysteinemia refers to an elevated circulating level of the sulfur-containing amino acid homocysteine and has been shown to be a risk factor for vascular disease in the general population. In patients with renal failure, hyperhomocysteinemia is a common feature. The underlying pathophysiological mechanism for this phenomenon is unknown. Proposed mechanisms include reduced renal elimination of homocysteine and impaired nonrenal disposal, possibly because of inhibition of crucial enzymes in the methionine-homocysteine metabolism by the uremic milieu. Absolute or relative deficiencies of folate, vitamin B6, or vitamin B12 may also play a role. Several case-control and prospective studies have now indicated that hyperhomocystenemia is an independent risk factor for atherothrombotic disease in patients with predialysis and end-stage renal disease. In renal patients, plasma homocysteine concentration can be reduced by administration of folic acid in doses ranging from 1 to 15 mg per day. In more than 50% of the cases, however, the homocysteine concentration remains above 15 micromol/L. The effects of vitamin B12 or vitamin B6 are unclear. Large intervention trials are now needed to establish whether homocysteine-lowering therapy will reduce atherothrombotic events in patients with renal failure. These studies are now planned or are ongoing.

Adult↗
PubMed2000

Hyperhomocysteinemia, vascular pathology, and endothelial dysfunction.

Hyperhomocysteinemia has been associated with premature atherothrombotic vascular disease. It is not known whether hyperhomocysteinemia induces a distinct type of vascular disease. Its interaction, if any, with traditional risk factors also remains unclear. The pathophysiological mechanisms linking hyperhomocysteinemia to vascular disease have been extensively studied in vitro and in animals. From these studies, it has been suggested that homocysteine limits the bioavailability of nitric oxide (NO), increases oxidative stress, stimulates smooth cell proliferation, and alters elastic wall properties. The relevance of these proposed mechanisms in vivo is unclear, because clinical studies have yielded controversial results with regard to the relation between plasma homocysteine levels and indices of endothelial function, such as brachial artery flow-mediated vasodilatation and plasma levels of endothelium-derived marker proteins. Up till now, there have been no controlled data on the effects of homocysteine-lowering treatment on vascular function or clinical end points. The precise mechanisms (if any) by which homocysteine mediates its adverse vascular effects are in fact unknown but may relate to impaired endothelial and smooth muscle cell function.

Adult↗
PubMed2000

Carotid artery stiffness in patients with end-stage renal disease: no effect of long-term homocysteine-lowering therapy.

BACKGROUND: The excess of cardiovascular disease in end-stage renal disease (ESRD) patients is unexplained, but could relate to altered intrinsic vascular wall properties, such as increased arterial stiffness, which could be mediated by hyperhomocysteinemia. We investigated potential determinants of carotid artery stiffness in ESRD patients and the effect of long-term homocysteine-lowering treatment. PATIENTS AND METHODS: Fifty-four patients on maintenance dialysis treatment were studied at baseline. Fourty-one patients completed the treatment protocol, which consisted of a 12-week treatment with folic acid 5 mg daily with or without betaine 4 g per day, and of 1 or 5 mg of folic acid thereafter for 40 weeks. Both phases were randomized. Compliance and distensibility coefficients (CC and DC) and the stiffness index (beta) of the common carotid artery were determined at baseline and after 52 weeks of treatment using a non-invasive vessel wall movement detector system. RESULTS: At baseline, plasma total homocysteine was elevated (44.1+/-33.7 micromol/l), but showed no relationship with CC, DC or beta. Age and mean arterial pressure (MAP) were the only independent determinants of CC and DC, whereas beta was associated with age only. Plasma homocysteine showed a sustained decrease after therapy (20.7+/-9.0 micromol/l at week 52). No significant changes occurred in CC (from 0.59+/-0.21 to 0.60+/-0.22 mm2/kPa; p = 0.47), in DC (from 14.9+/-6.1 to 15.3+/-6.2 10(-3)/kPa; p = 0.55), or in beta (from 10.9+/-4.7 to 11.2+/-4.4; p = 0.64). No independent determinants were detected for the change in CC, whereas the change in DC was inversely related to the change in MAP (stand. r = -0.58; p<0.0002). The decrease in MAP after therapy was significant (p = 0.003) and was related to the dialysis mode (p = 0.003) and smoking status (p = 0.02). CONCLUSION: Folic acid treatment of hyperhomocysteinemia has no major effect on carotid artery stiffness in chronic dialysis patients. The results do, however, emphasize the importance of tight blood pressure control in these patients.

Age Factors↗
PubMed1999

[Anti-aldosterone therapy in severe heart failure].

The mortality rate among patients with severe heart failure is still very high despite treatment with loop diuretics and angiotensin-converting enzyme (ACE) inhibitors. The 'randomized aldactone evaluation study' (RALES) has shown that 25 mg spironolactone added to this treatment was safe and reduced all-cause mortality by 30% in patients with severe (previous New York Heart Association (NYHA) functional class IV) heart failure due to systolic left ventricular dysfunction. Blockade of aldosterone in these patients may be necessary to overcome so-called aldosterone escape during chronic ACE-inhibition. The beneficial effects of spironolactone may relate to enhanced diuresis, anti-arrhythmogenic properties and direct effects on the myocardium and blood vessels. At present, addition of spironolactone may be appropriate for patients with severe heart failure, whereas patients with moderate heart failure may benefit more from beta-blockade.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Effect of folic acid and betaine on fasting and postmethionine-loading plasma homocysteine and methionine levels in chronic haemodialysis patients.

OBJECTIVES: To study fasting and postmethionine-loading (increment and decrement) plasma homocysteine levels in end-stage renal disease (ESRD) patients in relation to B-vitamin status and after folic acid treatment without or with betaine. DESIGN: Plasma total homocysteine (tHcy) and methionine levels were measured in chronic haemodialysis patients after an overnight fast, and 6 and 24 h after an oral methionine load (0.1 g kg-1). The patients were subsequently randomized to treatment with folic acid 5 mg daily with or without betaine 4 g daily, and the loading test was repeated after 12 weeks. The patients were then re-randomized to treatment with 1 or 5 mg folic acid daily for 40 weeks, after which a third loading test was performed. SETTING: Haemodialysis unit of university hospital and centre for haemodialysis. SUBJECTS: Twenty-nine consecutive maintenance (> 3 months) haemodialysis patients, not on folic acid supplementation, 26 of whom completed the study. RESULTS: At baseline, the mean fasting, the 6 h postload and the 6 h postload increment plasma tHcy levels were increased as compared with those in healthy controls (46.8 +/- 6.9 (SEM), 92.8 +/- 9.1 and 46.0 +/- 4.2 mumol L-1, respectively) and correlated with serum folate (r = -0.42, P = 0.02; r = -0.61, P = 0.001 and r = -0.54, P = 0.003, respectively), but not with vitamin B6 or vitamin B12. At week 12, these variables had all decreased significantly. Betaine did not have additional homocysteine-lowering effects. At week 52, fasting and postload tHcy levels did not differ significantly between patients on 1 or 5 mg folic acid daily. Plasma tHcy half-life and plasma methionine levels after methionine loading were not altered by folic acid treatment. CONCLUSIONS: In chronic haemodialysis patients, fasting as well as postmethionine-loading plasma tHcy levels depend on folate status and decrease after folic acid therapy. Increased postload homocysteine levels in these patients therefore do not necessarily indicate an impaired transsulphuration capacity only; alternatively, folate may indirectly influence transsulphuration. The elucidation of the complex pathogenesis of hyperhomocysteinaemia in chronic renal failure requires further investigation.

Adult↗
PubMed1999

Homocysteine and methionine metabolism in ESRD: A stable isotope study.

BACKGROUND: Hyperhomocysteinemia has a high prevalence in the end-stage renal disease (ESRD) population, which may contribute to the high cardiovascular risk in these patients. The cause of hyperhomocysteinemia in renal failure is unknown, and therapies have not been able to normalize plasma homocysteine levels. Insight into methionine-homocysteine metabolism in ESRD is therefore necessary. METHODS: Using a primed, continuous infusion of [2H3-methyl-1-13C]methionine, we measured whole body rates of methionine and homocysteine metabolism in the fasting state in four hyperhomocysteinemic hemodialysis patients and six healthy control subjects. RESULTS: Remethylation of homocysteine was significantly decreased in the hemodialysis patients: 2.6+/-0.2 (SEM) vs. 3.8+/-0.3 micromol. kg(-1)x hr(-1) in the control subjects (P = 0.03), whereas transsulfuration was not 2.5+/-0.3 vs. 3.0+/-0.1 micromol. kg(-1) x hr(-1) (P = 0.11). The transmethylation rate was proportionally and significantly lower in the ESRD patients as compared with controls: 5.2+/-0.4 vs. 6.8+/-0.3 micromol. kg(-1) x hr(-1) (P = 0.02). Methionine fluxes to and from body protein were similar. CONCLUSIONS: The conversion of homocysteine to methionine is substantially (approximately 30%) decreased in hemodialysis patients, whereas transsulfuration is not. Decreased remethylation may explain hyperhomocysteinemia in ESRD. This stable isotope technique is applicable for developing new and effective homocysteine-lowering treatment regimens in ESRD based on pathophysiological mechanisms.

Adult↗
PubMed1999

The impact of an amino acid-based peritoneal dialysis fluid on plasma total homocysteine levels, lipid profile and body fat mass.

BACKGROUND: The caloric load from glucose-based peritoneal dialysis (PD) fluids contributes to hypertriglyceridaemia, adiposity and, as result of anorexia, protein malnutrition in PD patients. It has been suggested that replacement of a glucose-based by an amino acids-based PD fluid (AA-PDF) for one exchange per day might improve the nutritional status and lipid profile. Due to the uptake of methionine from the dialysate, however, exposure to AA-PDF might aggravate hyperhomocysteinaemia, a frequently occurring risk factor for atherosclerosis in uraemic patients. METHODS: We studied the impact of a once daily exchange with 1.1% AA-PDF instead of glucose-based PD fluid for 2 months on plasma methionine and total homocysteine (tHcy) levels, lipid profile, butyrylcholinesterase (BChE) and body fat mass of seven stable PD patients. Results are expressed as mean+/-SEM. RESULTS: Methionine levels did not increase significantly during therapy, but tHcy levels increased substantially from 60+/-12 to 84+/-19 micromol/l after 1 month (P=0.039), and to 85+/-22 micromol/l after 2 months of AA-PDF treatment. Serum triglyceride concentration decreased from 3.0+/-0.4 mmol/l at entry to 2.6+/-0.5 mmol/l (at 1 month, P=0.041 vs baseline). Serum BChE also decreased from 6.9+/-0.4 U/ml at entry to 6.3+/-0.4 U/ml after 2 months (P=0.014). Total cholesterol concentration and cholesterol fractions did not change. The reduced exposure to glucose-based PD fluid for 2 months resulted in a 0.5 kg reduction in fat mass which was due mainly to a reduction in fat mass of the trunk region (0.3 kg, P=0.031). CONCLUSIONS: It is concluded that methionine-containing AA-PDF induces an increase in the plasma tHcy level. This might, potentially, offset the beneficial effects of an improved serum lipid profile and reduced fat mass on the risk of cardiovascular disease in PD patients. Lowering the methionine content of the fluid, therefore, may be required to overcome this adverse effect.

Adipose Tissue↗
PubMed1998

[Hyperthyroidism induced by iodinated roentgen contrast media].

Three patients with subclinical hyperthyroid goitre, women aged 63, 72 and 75 years following intravenous administration of an iodinated contrast medium developed hyperthyroidism with a marked rise of the concentration of free T4. Thyreostatic agents were unsuccessful in two patients, the third was left untreated. Hyperthyroidism improved spontaneously in all three. Iodine-induced hyperthyroidism is rare and is usually encountered in patients with a pre-existent autonomous thyroid function. Treatment of iodine-induced hyperthyroidism is essentially exclusively symptomatic. Prophylaxis with sodium perchlorate should be considered in cardiac patients with a goitre and a subnormal level of thyroid-stimulating hormone (TSH).

Aged↗
PubMed1998

The effect of renal transplantation on hyperhomocysteinaemia in dialysis patients, and the estimation of renal homocysteine extraction in patients with normal renal function.

BACKGROUND: The pathophysiology of hyperhomocysteinaemia in chronic renal failure (CRF) is unknown. Possible mechanisms are decreased renal homocysteine (Hcy) catabolism or inhibition of extrarenal Hcy metabolism by uraemic toxins. METHODS: We studied the short-term effect on plasma Hcy concentration of improvement of renal function after successful kidney transplantation (n = 8), and determined renal Hcy extraction by measurement of total Hcy in arterial and renal venous blood in 7 cardiac patients with normal renal function. RESULTS: Post-transplantation, plasma Hcy decreased with improving renal function. In the cardiac patients, no significant renal Hcy extraction could be demonstrated, but tubular disposal of the filtered load could not be excluded. CONCLUSIONS: Because loss of such renal metabolism could lead to hyperhomocysteinaemia in CRF, it is necessary to determine the renal extraction of free Hcy in subjects with normal renal function to further investigate renal homocysteine metabolism.

Adult↗
PubMed1998

No net renal extraction of homocysteine in fasting humans.

BACKGROUND: The pathophysiological mechanism of hyperhomocysteinemia in chronic renal failure in humans is unknown. The loss of a putative renal homocysteine extraction in chronic renal failure has been hypothesized as significant homocysteine uptake has been demonstrated in the normal rat kidney. We studied homocysteine extraction in the normal human kidney. METHODS: We measured plasma total (free and protein-bound) and free homocysteine (tHcy and fHcy, respectively) in arterial and renal venous blood sampled from the aorta and right-side renal vein during cardiac catheterization in 20 fasting patients with normal renal function. Renal homocysteine extraction was calculated as the arteriovenous difference divided by the arterial levels times 100%. RESULTS: No significant renal extraction was demonstrated either for tHcy: 0.9% (SD 5.8; 95% CI -1.8 to +3.6) or for fHcy: -0.2% (11.0; -5.4 to +4.9). CONCLUSIONS: We conclude that no significant net renal uptake of homocysteine occurs in fasting humans with normal renal function. The loss of such uptake, therefore, cannot cause hyperhomocysteinemia in patients with renal failure.

Aged↗