An observational Study in Optimising Intraperitoneal Gentamicin in peritoneal dialysis patients with peritonitis

Patient selection Patients with clinically defined signs and symptoms of peritonitis who fulfill the inclusion/exclusion criteria below will be eligible for the study. Two groups of patients will be included with 15 patients entering each group. a) Anuric patients (with a urine output of less than 100ml/day) b) Non-anuric patients (with a urine output of more than 100ml/day) Categorisation of patients into the two groups will be based on data from 24-hour urinary collection done within the preceding 6 months. Drug dosing Drug dosing will be based on the current International Society for Peritoneal Dialysis Guidelines (2005). a) Anuric patients 0.6mg/kg gentamicin in a single bag administered intraperitoneally once daily and allowed to dwell for at least 6 hours for 14 days or 21 days depending on the organism grown in peritoneal dialysis fluid b) Non-anuric patients For this group of patients with residual renal function, the dose of gentamicin in group (a) will be increased by 25% Sample collection All patients will be sampled on 2 separate days. Serial plasma and peritoneal dialysis (PD) fluid will be collected as follows: On DAY 1: Plasma samples (5ml each) taken at 1 hour, 3 hours, 6 hours and 7 hours after the administration of the first bag of gentamicin intraperitoneally. PD fluid samples (5ml) will also be collected at 3 hours AND at the end of the dwell time. Between DAY 2 and DAY 5 A plasma sample (5ml) will be taken just prior to the administration of the next bag of gentamicin (to measure ‘trough’ gentamicin levels) followed by plasma samples (5ml each) at 1 hour, 3 hours, 6 hours and 7 hours after the administration of the next bag of gentamicin intraperitoneally. PD fluid samples (5ml) will also be collected prior to the administration of the next bag of gentamicin, at 3 hours AND at the end of the dwell time. For each dose of intraperitoneal gentamicin administered, the type and volume of dialysate and inflow rate of the dialysate plus drug will be recorded. A 5ml sample from the 24 hour urine collection will be collected to measure the concentration of gentamicin excreted in urine. Samples (10ml) from each bag of PD fluid will also be obtained before the dialysis effluent is discarded.