We have developed an extracorporeal system for investigating in vitro the biofilm-adherent bacterial microcolonies (BABM) that grow on Tenckhoff catheters (TC), to study peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). A modified Robbins’ device, attached to sampling plugs with TC discs and connected to the dialysate via a peristaltic pump, is run for 24 h; scrapings from pairs of TC discs are processed for assessment of viable BABM, one of each pair for culture by routine microbiology techniques and the other for examination by scanning and transmission electron microscopy (EM). No colonization was noted with fresh dialysis solutions and spent dialysates from patients without clinical peritonits; but, when bacterial suspensions were added to aliquots of the same dialysates, BABM were noted on both culture and EM. In a study of 4 patients on CAPD treatment, who had clinically evident peritonitis, routine cultures of spent dialysate were positive in only 2, but BABM were found in cultures and EM preparations of disc scrapings in all 4 cases. We conclude from these preliminary findings that this extracorporeal system is reliable, and well suited for studying the role of BABM in CAPD-associated peritonitis in vitro.
The effects of hemodialysis on cerebral tissue and cerebrospinal fluid constituents and on intracranial pressure were investigated in dogs. It was shown that the potassium content of the cerebral cortical gray matter is decreased in uremic brain. In uremic animals the urea concentration of cerebral tissues was found to be in equilibrium with that of plasma whereas the urea concentration of cerebrospinal fluid was significantly lower. Hemodialysis for 60 minutes with a Kolff twin-coil artificial kidney rapidly decreased the urea concentration in the plasma and caused a considerable but slower decrease in the urea content of cerebral tissues. The urea level in cerebrospinal fluid was only slightly altered. Consequently, a significant transient difference developed between the urea concentrations in brain and plasma. The difference between the concentration of urea in cerebrospinal fluid and plasma was always more pronounced and of longer duration after hemodialysis. Swelling of cortical gray matter was demonstrated in 50% of dialyzed uremic animals and of white matter in 75%. A rapid rise in cerebrospinal fluid pressure occurred during dialysis in all cases. Similar effects were observed when a concentration gradient for sodium between plasma and the central nervous system was produced in normal animals by dialysis against a hyposmotic, low-sodium bath fluid. It was concluded that, in experimental uremia, hemodialysis results in increased cerebrospinal fluid pressure owing to an osmotically induced increase in cerebrospinal fluid volume and, to a variable extent, to osmotically induced cerebral tissue swelling. Osmotically induced cerebral swelling was shown to be a different phenomenon from cerebral edema associated with trauma.
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