Hypotension during hemodialysis results from an impairment of arteriolar tone and left ventricular function.

AIMS: Hypotensive episodes are a major complication of hemodialysis. Hypotension during dialysis could be directly related to a reduction in blood volume or to a decrease in cardiovascular activation as a response to decreased cardiac filling. A decreased cardiovascular activation could be due to patient-related or to dialysis-related factors. In order to study the isolated effect of a reduction in filling pressure, lower body negative pressure (LBNP) causes activation of the cardiovascular reactivity with a decrease in cardiac filling, but without the influence of the dialysis procedure that could affect cardiovascular reactivity. METHODS: We studied the relationship between relative blood volume (RBV), central venous pressure (CVP), systolic arterial pressure, heart rate, stroke volume index (SI), and total peripheral resistance index (TPRI) during a combined dialysis/ultrafiltration and during LBNP to -40 mmHg in 21 hemodialysis patients with a high incidence of hypotension. Systolic arterial pressure, heart rate, SI and TPRI were measured by Finapres. CVP was measured after cannulation of the jugular vein. During dialysis RBV was measured by a blood volume monitor (BVM). In order to study the conditions in which hypotension occurred after dialysis, we divided the patients into 2 groups: hypotensive (H) and non-hypotensive (NH) during dialysis. RESULTS: Baseline levels did not show any significant differences. During dialysis systolic arterial pressure declined gradually in the H group from 30 minutes before the onset of hypotension. There was a similar decrease of RBV and increase of heart rate in both groups with a large interindividual variation. At hypotension, H patients showed a significantly smaller increase in TPRI as compared to NH patients. The reduction in SI tended to be greater at hypotension, while CVP decreased to a similar extent in both groups. Moreover, during LBNP, a similar reduction in CVP resulted in a much smaller decrease in SI. Systolic arterial pressure was only slightly lowered due to a much greater increase in TPRI. CONCLUSION: We conclude that dialysis-related hypotension in our patient group did not result from an inability to maintain blood volume or from decreased cardiac filling. Hypotension appeared to result from the inability to adequately increase arteriolar tone and a reduction in left ventricular function. Both vascular tone and left ventricular function appeared to be impaired by the dialysis procedure.

Increase in blood volume during dialysis without ultrafiltration.

Combined dialysis and ultrafiltration leads to more frequent episodes of hypotension than isolated ultrafiltration. It has been suggested that decreased plasma volume preservation could be responsible for this phenomenon. The present study evaluates the effects of diffusive dialysis on the changes in relative blood volume (RBV). Six stable hemodialysis patients, without the need of ultrafiltration, were studied during 10 sessions of diffusive dialysis (bicarbonate) lasting 4 h. RBV was monitored continuously by measurement of hematocrit. During the 1st and 2nd h RBV increased by 2.4+/-1.4 and 2.5+/-0.8% respectively, returning to baseline levels at the end of dialysis. No changes in blood pressure or heart rate were noted. We conclude that during diffusive dialysis without ultrafiltration RBV is increased. A decrease in vascular resistance, or changes in regional blood distribution could explain these findings.

Variability of relative blood volume during haemodialysis.

BACKGROUND: A decrease in blood volume is thought to play a role in dialysis-related hypotension. Changes in relative blood volume (RBV) can be assessed by means of continuous haematocrit measurement. We studied the variability of RBV changes, and the relation between RBV and ultrafiltration volume (UV), blood pressure, heart rate, and inferior caval vein (ICV) diameter. METHODS: In 10 patients on chronic haemodialysis, RBV measurement was performed during a total of one hundred 4-h haemodialysis sessions. Blood pressure and heart rate were measured at 5-min intervals. ICV diameter was assessed at the start and at the end of dialysis using ultrasonography. RESULTS: The changes in RBV showed considerable inter-individual variability. The average change in RBV ranged from -0.5 to -8.2% at 60 min and from -3.7 to -14.5% at 240 min (coefficient of variation (CV) 0.66 and 0.35 respectively). Intra-individual variability was also high (CV at 60 min 0.93; CV at 240 min 0.33). Inter-individual as well as intra-individual variability showed only minor improvement when RBV was corrected for UV. We found a significant correlation between RBV and UV at 60 (r= -0.69; P<0.001) and at 240 min (r= -0.63; P<0.001). There was a significant correlation between RBV and heart rate (r= -0.39; P<0.001), but not between RBV or UV and blood pressure. The level of RBV reduction at which hypotension occurred was also highly variable. ICV diameter decreased from 10.3+/-1.7 mm/m(2) to 7.3+/-1. 5 mm/m(2). There was only a slight, although significant, correlation between ICV diameter and RBV (r= -0.23; P<0.05). The change in ICV-diameter showed a wide variation. CONCLUSIONS: RBV changes during haemodialysis showed a considerable intra- and inter-individual variability that could not be explained by differences in UV. No correlation was observed between UV or changes in RBV and either blood pressure or the incidence of hypotension. Heart rate, however, was significantly correlated with RBV. Moreover, IVC diameter was only poorly correlated with RBV, suggesting a redistribution of blood towards the central venous compartment. These data indicate that RBV monitoring is of limited use in the prevention of dialysis-related hypotension, and that the critical level of reduction in RBV at which hypotension occurs depends on cardiovascular defence mechanisms such as sympathetic drive.

Simulation study of the intercompartmental fluid shifts during hemodialysis.

Hypotension is the most frequent complication during hemodialysis. An important cause of hypotension is a decrease in the intravascular volume. In addition, a decrease in plasma osmolality may be a contributing factor. Modeling of sodium and ultrafiltration (UF) may help in the understanding of underlying relationships. We therefore simulated, in a mathematical model, the intercompartmental fluid shifts during standard hemodialysis (SHD), diffusive hemodialysis (DHD), and isolated ultrafiltration (IU). We analyzed the relative theoretical effect of hydration status, dialysate sodium concentration, the initial plasma concentrations of sodium and urea, and tissue permeation to solutes on the magnitude and direction of intracellular and intravascular volume changes. This theoretical analysis shows that the transcellular fluid shifts taking place during hemodialysis treatment are, to a great part, due to inhomogeneous distribution of regional blood flow and tissue fluid volumes. During hemodialysis treatment, the cellular fluid shifts in tissue groups with relatively high perfusion and small volume occur from the intra- to the extracellular spaces. However, the fluid shift in tissue groups with a low perfusion and large volume takes place in the opposite direction. The UF volume and rates, and the size of the sodium (Na+) gradient between the dialysate and blood side of the dialyzer membrane are the most important factors influencing the fluid shifts. Higher UF volumes and flow rates cause an increasing decline in the plasma volume in both SHD and IU. High dialysate sodium concentration (150 mEq L(-1)) helps plasma refilling slightly when compared with a normal dialysate sodium concentration (140 mEq L(-1)). However, a high dialysate sodium concentration is associated with a high plasma sodium rebound, which in turn may lead to interdialytic water intake resulting from thirst and may cause increased weight gain and hypertension.

Choledochocele presenting with anaemia.

A 31-year-old man presented with abdominal pain and iron deficiency anaemia due to gastrointestinal blood loss. Endoscopic retrograde cholangiopancreatography (ERCP) revealed a choledochocele, located between the ampullary sphincter and the sphincters of the common bile duct and pancreatic duct. The choledochocele was removed surgically and appeared to be covered with duodenal mucosa. Gastrointestinal blood loss is explained by the extensive erosions found in the duodenal mucosa of the choledochocele. Choledochoceles should be treated by radical resection.

Suggestive evidence for bromocriptine-induced pleurisy.

Pleurisy of initially unknown origin was found in a patient who was treated with bromocriptine for Parkinson's disease for 6 years. At presentation, bilateral pleural thickening existed that caused severe restriction of pulmonary function. There were an elevated erythrocyte sedimentation rate, polyclonal hypergammaglobulinaemia, increased levels of acute phase proteins and anaemia. After withdrawal of the bromocriptine the patient's complaints as well as the laboratory parameters markedly improved. Further loss of pulmonary function did not occur. However, the pleural thickening did not resolve, not even upon subsequent corticosteroid treatment, probably due to fibrosis. Together, these findings strongly suggest a causative role of bromocriptine. The results of the laboratory studies suggested an immunopathogenetic mechanism, but in vitro lymphocyte-proliferation studies and skin patch tests with bromocriptine were negative. Bromocriptine should be considered as a cause of pleurisy. The drug must be stopped immediately upon the occurrence of pleural thickening in order to prevent impairment of pulmonary function. In addition, periodic laboratory and X-ray studies in patients on long-term bromocriptine treatment should be considered.

Quantitative interpretation of coprocultures in a population infected with Oesophagostomum bifurcum.

Coproculture is used in northern Togo and Ghana in the research on Oesophagostomum bifurcum, a common parasite of man in these regions. Prior to a follow-up study to investigate patterns of reinfection in Oesophagostomum and hookworm, it was attempted to evaluate the relevance of counting larvae for the assessment of the intensity of infection at the population level. Of 102 samples, one egg count (Kato-smear) and three coprocultures were carried out. Frequency distributions of counts of larvae of Oesophagostomum and of hookworm isolated in three coprocultures, showed log-normality. There was a highly significant correlation between egg counts and the combined number of Oesophagostomum and hookworm larvae (Spearman rank correlation test, r = 0.74, p < 0.01). It is concluded that the mean larval counts of three coprocultures can be interpreted quantitatively, as normally done for egg counts. A quantitative classification of larval counts is proposed.

Reinfection patterns of Oesophagostomum bifurcum after anthelmintic treatment.

Subjects infected with the adult worms of Oesophagostomum bifurcum, diagnosed through semiquantitative detection of characteristic third stage larvae, were treated in the middle of the dry or in the middle of the rainy season with two different dosages of albendazole. A third group was not treated. The pattern of reinfection after treatment was analysed. Transmission of Oesophagostomum infection appeared to be limited to the rainy season and the rate of reinfection was independent of the dose of albendazole received. The impact on transmission of developing stages that might survive in the nodules in the intestinal wall is discussed.

Serological diagnosis of Oesophagostomum infections.

A sensitive and specific enzyme-linked immunosorbent assay (ELISA) is described to diagnose human infection with Oesophagostomum bifurcum. In an ELISA using crude soluble antigen, prepared from adult O. bifurcum, many cross reactions occurred when measuring IgG titres in patients with other helminth infections. An ELISA based on the detection of specific IgG4, however, had a specificity of over 95%. The sensitivity of the IgG4 ELISA was difficult to assess because a reliable parasitological diagnosis is not available. The IgG4-ELISA described seems to be a powerful new tool to study the distribution of this little known but locally very common nematode parasite.

Observations on the morphology of adults and larval stages of Oesophagostomum sp. isolated from man in northern Togo and Ghana.

Infection with Oesophagostomum sp. appears to be extremely common in man in northern Togo and Ghana. Adult specimens were recovered from the intestinal lumen by treatment with pyrantel pamoate and the morphological characteristics of oesophagostomes of man could for the first time be compared with information available on the morphology of oesophagostomes of monkeys. The observations and measurements demonstrated that the species involved is Oesophagostomum bifurcum and that the eggs of this species cannot be differentiated from those of Necator americanus. Both infections occur simultaneously in the population involved. The L1 larvae, too, cannot be differentiated from hookworm L1 larvae. The L3 larvae, however, are characteristic. Diagnoses of human Oesophagostomum infections is based on the detection of these larvae in coprocultures. In the present paper, the eggs, the L1 and L3 larval stages and the adults, are carefully described and photos are given.

Treatment of mixed Oesophagostomum and hookworm infection: effect of albendazole, pyrantel pamoate, levamisole and thiabendazole.

Oesophagostomum bifurcum has recently been recognized as a common parasite of man in northern Togo and in Ghana. In a preliminary trial several anthelmintics were evaluated in the treatment of mixed Oesophagostomum and hookworm infections. Diagnosis was based on faecal culture, since the eggs of Oesophagostomum and hookworm cannot be distinguished morphologically. Of the anthelmintics tested, albendazole was most effective against both parasites. Pyrantel pamoate, 2 x 10 mg/kg, was effective against Oesophagostomum but not against hookworm. The cure rates for both parasites were moderate with thiabendazole and poor with levamisole.

Human Oesophagostomum infection in northern Togo and Ghana: epidemiological aspects.

Recently, it has been established that human infection with Oesophagostomum bifurcum is common in northern Togo and northeastern Ghana. Two surveys were conducted in this area. In a regional survey, O. bifurcum infection appeared to occur in 38 of 43 villages. The highest prevalences (up to 59%) occurred mostly in small isolated villages and were usually associated with high hookworm infection rates. The infection was relatively rare in children under five years of age (7% infected). In older individuals, females showed higher prevalences than males (30% vs. 24%). In a second survey, the entire population of two high-prevalence villages was examined. Infection rates were low in children under three years of age, but rose quickly thereafter, suggesting intense transmission. A stable level of infection was reached by 10 years of age. Oesophagostomum larvae were found more frequently in hookworm-positive than in hookworm-negative coprocultures, and possible explanations for the association between infection with Oesophagostomum and hookworm are discussed.

Egg production of Oesophagostomum bifurcum, a locally common parasite of humans in Togo.

In northern Togo and northeastern Ghana, Oesophagostomum bifurcum is a common parasite in humans. Diagnosis is based on coproculture because the eggs of hookworm and Oesophagostomum are indistinguishable. To determine the level of egg production, 12 subjects were treated with 2 x 10 mg/kg of pyrantel pamoate and the worms they evacuated were then counted. Pretreatment and post-treatment species-specific egg counts were calculated on the basis of larval and total egg counts. The median worm burden was 81 (range 12-300) per person. The calculated median egg production was 33.7 egg/gram of feces per female worm. Assuming a total daily stool production of 150 g/day, this amounts to 5,055 eggs/day, which is comparable with the production of other nematodes of the same superfamily.

Oesophagostomiasis, a common infection of man in northern Togo and Ghana.

Infection with Oesophagostomum sp. is normally considered a rare zoonosis and up to this time its diagnosis has been based on the demonstration of larvae and young adult worms in the typical nodules formed in the intestinal wall. Only in Dapaong, in North Togo, and Bawku, North Ghana, have larger series of clinical cases been described. In the rural areas around these towns, a survey was made in which stool samples were collected and cultured. Third-stage larvae of Oesophagostomum sp. could be found after 5-7 days of incubation at room temperature, and the prevalence of infection with this parasite was often high but varied from one village to another. It was over 30% in seven villages out of the 15 villages surveyed. Anthelmintic treatment resulted in the evacuation of adult males and females of O. bifurcum. It is concluded that O. bifurcum is a locally common parasite of humans, not requiring an animal reservoir for completion of its lifecycle.

[The changed picture of schistosomiasis in The Netherlands]. / Het veranderende beeld van schistosomiasis in Nederland.

Schistosomiasis is a very frequent import infection in the Netherlands. The serotesting for schistosomiasis in Leyden affords reasonable insight into the prevalence of this import infection among different groups of the population in the Netherlands. Out of 3032 serum samples submitted in the period from 1983 to April 1986, 40% was positive. Most people with positive serum tests were of Surinam origin. Currently, there is a shift toward more infections among Dutch travellers. Many of these patients have high IFA titres indicating a recently incurred infection. Often no ova are found in spite of positive serotest: this phenomenon was seen in 36% of the Dutch travellers and in 48% of the Surinam people.