Pharmacokinetics of antifungal agents.

The authors have evaluated the pharmacokinetics of four antifungal agents used in the therapy of fungal peritonitis. Amphotericin B (Amph B) poorly diffuses from blood into peritoneal fluid, which intraperitoneal administration induces severe abdominal pain. 5-Fluorocytosine (5FC) easily crosses peritoneum, but resistance may appear when the drug is used alone. Ketoconazole (K) poorly penetrates into peritoneal fluid, while Fluconazole (F), used per os or intraperitoneally, shows a good antifungal activity both in serum and in the peritoneal fluid. In conclusion, from a pharmacokinetic point of view, all the antifungal agents examined, perhaps with the exception of F, do not offer, when used alone, sufficient guarantees in curing peritonitis. Therefore, for treating fungal infections in CAPD, drug combinations such as AmphB + 5FC, K + 5FC or 5FC+F have to be used.

Continuous ambulatory peritoneal dialysis and automated peritoneal dialysis: are there differences in outcome?

The proportion of peritoneal dialysis (PD) patients on automated peritoneal dialysis (APD) has been steadily increasing over the past decade. In the US, the percentage of PD patients on APD has steadily risen from 9% in 1993 to 54% in 2000. In continuous ambulatory peritoneal dialysis (CAPD), PD exchanges are performed manually, while in APD a mechanical device to assist the delivery and drainage of dialysate is employed. In CAPD, the patient or carer must perform at least 4-5 exchanges everyday. Many problems inherent to CAPD such as lack of sustained patient motivation over long periods of time, technique failure and recurrent peritonitis, led to a resurgence of interest in APD. APD has been reported to have several advantages over CAPD including lower incidence of peritonitis, better small solute clearances and reduced incidences of hernias. APD, especially in the form of nocturnal intermittent peritoneal dialysis (NIPD), has also been suggested to offer a number of psychosocial and physical benefits over CAPD mainly on account of fewer connections and being free of fluid in the abdomen during daytime. Such benefits relate to better dialysis acceptability for workers, school students or carers of elderly patients, pain and body image difficulties and reduced intra-abdominal pressures. APD is also considered to be more suitable form of PD in patients who have a rapid rate of solute transfer across their peritoneal membrane (high transporters) because of the ability to perform rapid frequent exchanges with shorter dwell times. It is not still clear if, with APD when compared to CAPD, a more rapid decline in residual renal function is present. Since the direct costs of APD are over 20% greater than CAPD and given this increasing trend towards greater use of APD, the aim of this paper is to understand if there are really differences in terms of quality of life and outcomes in favor of APD when compared to CAPD.

Fluctuation of vasopressin secretion in chronic hypernatremia.

Herein we will describe a case of chronic hypernatremic-hyperosmolar syndrome with cerebral localization of systemic sarcoidosis. Several determinations of plasma arginine vasopressin (p-AVP) at various plasma sodium levels were carried out in this patient. During the study p-AVP values varied between 2.6 and 9.5 pg/ml. A high percentage of them was related to plasma osmolality, pointing out that p-AVP secretion was osmotically mediated. This behavior is in contrast with the tendency of hypernatremic patients previously reported in the literature, in whom p-AVP values were inappropriately low for the corresponding degree of plasma osmolality, suggesting that vasopressin secretion was not influenced by osmotic stimulation. Furthermore, our case, unlike those previously described, showed high values of urinary osmolality. In conclusion, our patient represents, in essence, the 'middle' of the spectrum of the hypodipsic-hypernatremic syndrome, because she is to be inserted between the majority of patients who have little or no osmotically mediated AVP release and the case of a child, recently described, who had completely normal AVP secretion.

Total solute extraction versus clearance in the evaluation of standard and short hemodialysis.

The authors compared the efficiency of standard HD (t = 240 minutes, Qb = 300 ml/min, Qd = 500 ml/min) with short HD (t = 150 minutes, Qb = 500 ml/min, Qd = 700 ml/min). The study was carried out in 11 patients in two sequential dialysis sessions, utilizing the same high surface area hollow fiber dialyzers, after a 2 day interdialytic period. With short HD, as expected, the clearance (Cl) of BUN, creatinine (Cr), and phosphates (P) was significantly higher than in standard HD:Cl BUN = 331 vs. 225, Cl Cr = 286 vs. 193, and Cl P = 231 vs. 176 ml/min. No significant difference in the total BUN extraction (measured on the total amount of exhausted dialysate) was found between the two techniques. As to Cr and P, despite higher Cl in short HD, the total extractions were significantly lower. In conclusion, in the evaluation of short HD efficiency, instantaneous Cl can be adequate for small molecules, while for larger solutes, other parameters, such as total extraction, must be considered.

The importance of ultrafiltration on acid-base status in a dialysis population.

The amount of fluid withdrawn by ultrafiltration in a dialysis session plays an important role in regulating the acid-base status of patients. It has been previously demonstrated that an interdialytic weight gain of 3 kilograms requires the removal of 3 liters, mostly of extracellular fluid, which may contain 60-70 mMols of bicarbonate. Such losses require an increase in the buffer mass transfer to achieve a good buffer balance. The importance of interdialytic weight gain (IWG) on acid-base status was evaluated in two significantly different periods. In the period where the IWG was lower, predialytic pH and HCO3 were significantly higher than in the alternate period. Since dialysis schedule, dialysate buffer, daily protein intake and given medications did not differ during the two periods, we conclude that a reduced ultrafiltration due to less weight gain betters predialytic acid-base status.