Determinants of vancomycin clearance by continuous venovenous hemofiltration and continuous venovenous hemodialysis

The clearance of vancomycin is significantly reduced in patients with acute, as well as, chronic renal failure. Although multiple-dosage regimen adjustment techniques have been proposed for these patients, there is little quantitative data to guide the individualization of vancomycin therapy in acute renal failure patients who are receiving continuous renal replacement therapy (CRRT). To determine appropriate vancomycin dosing strategies for patients receiving continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodialysis (CVVHD), we performed controlled clearance studies in five stable hemodialysis patients with three hemofilters: an acrylonitrile copolymer 0.6 m2 (AN69), polymethylmethacrylate 2.1 m2 (PMMA), and polysulfone 0.65 m2 (PS). Patients received 500 mg of vancomycin intravenously at least 12 hours before the start of the clearance study. The concentration of vancomycin in multiple plasma and dialysate/ultrafiltrate samples was determined by EMIT (Syva, Palo Alto, CA). The diffusional clearance and sieving coefficient (SC) of vancomycin were compared by a mixed-model repeated-measures analysis of variance (ANOVA) with filter and blood (Q(B)), dialysate inflow (Q(DI)), or ultrafiltration rate (Q(UF)) as the main effects and patient as a random effect. Vancomycin was moderately protein bound in these patients; free fraction ranged from 49% to 83%. The SCs of the three filters were similar and significantly correlated with the free fraction of vancomycin (P = 0.01; r2 = 0.465). Significant linear relationships were observed between the diffusional clearance of vancomycin and Q(DI) for all three filters: AN69 (slope = 0.482; r2 = 0.880); PMMA (slope = 0.853; r2 = 0.966); and PS (slope = 0.658; r2 = 0.887). The slope of this relationship for the PMMA filter was significantly greater than that of the AN69 and PS filters. The clearance of vancomycin, urea, and creatinine, however, was essentially constant at all Q(B)s for all three filters. Thus, the clearance of vancomycin was not membrane dependent during CVVH. However, during CVVHD, membrane dependence of vancomycin clearance was noted at a Q(DI) greater than 16.7 mL/min; vancomycin clearance with PMMA at a Q(DI) of 25 mL/min was 66% and 43% greater than that with the AN69 and PS filters, respectively. CVVH (62% to 262%) and CVVHD (90% to 540%) can significantly augment the clearance of vancomycin in acute renal failure patients. Dosing strategies for individualization of vancomycin therapy in patients receiving CVVH and CVVHD are proposed.     

Active immunization with a synthetic peptide region of growth hormone: increased lean tissue growth.

The effects of active immunization against a specific peptide region of GH (sequence 134-154) were examined in a species relevant for animal production in vivo. Peptide-immunized lambs exhibited significant increases in carcass protein and water contents and consequently increased carcass weight. The comparatively smaller increases in carcass water and protein contents which occurred in GH-treated lambs were offset by decreased fat accretion. Thus, even though peptide immunization improved lean tissue growth, it did not simply enhance all actions of GH or mimic exogenous hormone administration. This is the first definitive demonstration that endogenously produced antibody may enhance endogenous hormone activity and performance in animals.     

Computer-assisted and frameless stereotaxy: the initial Australian experience.

The trends towards minimally invasive surgery coupled with the increasing use of computer software and hardware have led to an increasing use of stereotactic neurosurgery as a part of mainstream neurosurgery. Computer-assisted and frameless stereotactic systems allow the performance of stereotactic procedures without the need for the mechanical linkage to a stereotactic frame. St Vincent's Hospital, Sydney, has used the Radionics Operating Arm System since March 1994 in 106 cases for stereotactic biopsy, localization of superficial lesions and volumetric resection of tumours. The Operating Arm System uses mechanical digitizers and has the advantages of being able to be used for both framed-based and frameless stereotactic procedures, simplicity of use, and the arm as a 'mouse' software program allowing the surgeon control of the computer program within the sterile operative field.     

Splenic abscess: percutaneous drainage

Experience with percutaneous drainage in four cases of splenic abscess is presented. Percutaneous drainage and antibiotics were curative in three of four cases. The one case not adequately treated by antibiotics and percutaneous drainage was also complicated by ascites and multilocular collections. Percutaneous drainage in this case did not adversely affect subsequent curative surgery. Percutaneous catheter drainage of splenic abscess under radiologic guidance can be a safe, effective treatment.