Comparison of creatinine and inulin clearances in multiple trauma.

Creatinine clearance (Ccr) is a good predictor of renal dysfunction. However, numerous analytical interferences have been observed with the classical measurement of creatinine by Jaffé's procedure. This prospective study was conducted to compare 4 methods for determining creatinine; and also endogenous creatinine clearance with inulin clearance (Cin) to estimate the glomerular filtration rate. The 4 different techniques for measuring creatinine were: 1) 2 techniques using Jaffé's colorimetric reaction: one with rapid and the other with slow kinetics: 2) 2 more selective methods: enzymatic procedure and high performance liquid chromatography (HPLC). Measurements were performed in 13 multiple trauma patients after stabilization and in 5 comatose patients (control group) over a 3-day period, with strict 24-h urine collection. On the second day, inulin clearance and para-aminohippuric acid clearance (Cpah) were measured. Measurement of creatinine by Jaffé's procedure yields significantly higher levels than those obtained by the other methods. Higher levels of both plasma and urinary creatinine were observed in the multiple trauma patients with all the methods used. There were no significant differences in Ccr, Cin, Cpah between the multiple trauma patients and the control patients. The best correlations between inulin clearance and creatinine clearance were observed for Jaffé's rapid kinetics (r = 0.90) in the control group and for the enzymatic procedure in the multiple trauma group (r = 0.55). Plasma creatinine is not a useful indicator in multiple trauma. The correlation between creatinine clearance and inulin clearance is not very strong in multiple trauma, indicating that the relative evolution (not the absolute values) of creatinine clearance is of interest.

Expanded polytetrafluoroethylene reinforcement material in glaucoma drain surgery.

PURPOSE: To determine whether a synthetic material, expanded polytetrafluoroethylene (E-PTFE), can be used successfully as a reinforcement material over the tubes of glaucoma drainage implants. METHODS: Patches of E-PTFE were sutured over the tubes of Baerveldt glaucoma drains implanted in the eyes of New Zealand white rabbits. Two material thicknesses were tested: 0.5 mm in four eyes and 0.25 mm in five eyes. Rabbit donor scleral patches were used in five eyes as the control. Total ocular health and intraocular pressure were monitored every 2 weeks after the procedure. Six months after implantation, the eyes were harvested and analyzed histologically. RESULTS: Two of the four eyes that received 0.5-mm thick E-PTFE patches showed some conjunctival melting over the anterior corners of the material close to the limbus. All five eyes that received 0.25-mm thick E-PTFE patches showed a healthy cellular wound healing response and no conjunctival melting. Cellular infiltration and collagen deposition in the E-PTFE materials showed integration of the patch material into the surrounding tissue. In the control eyes, marked thinning and resorption of the donor sclera immediately above the drainage tube was noted. CONCLUSION: Thin (0.25 mm) E-PTFE patches were well tolerated in all rabbit eyes tested. Thin E-PTFE should be investigated further as a functional alternative to donor sclera for reinforcement in glaucoma drain surgery.

Determination of yttrium in rare earths by photon activation analysis.

The determination of yttrium in the presence of large amounts of the rare earths by the thermal neutron reaction (89)Y(n, gamma)(90)Y is complicated because of frequent problems of sample self-shielding from major constituents of the sample, and the difficulty of separating (90)Y, a pure beta-emitter, from other elements which are very similar chemically. A non-destructive photon activation analysis method has been developed for this determination. Bremsstrahlung from a 35-muA beam of 35-MeV electrons induces the photonuclear reaction (89)Y(gamma, n)(88)Y. Optimum sensitivity is obtained by coincidence counting of the 0.90 and 1.84 MeV gamma-rays associated with the decay of (88)Y. The detection limit is less than 1 mug of yttrium.

Biocompatibility response to modified Baerveldt glaucoma drains.

Glaucoma implants are designed to increase fluid outflow from the eye in order to decrease intraocular pressure and prevent damage to the optic nerve. The implant consists of a silicone tube that is inserted into the anterior chamber at one end and is attached at the other end to a silicone plate that is sutured to the outside of the globe beneath the conjunctiva. The glaucoma "implant" becomes a "drain" over the first 3 to 6 postoperative weeks as the silicone plate is enclosed by a fibrous capsule that allows a space to form into which fluid can drain and from which fluid can be absorbed by the surrounding tissues. Ideally, the size and thickness of the capsule (the filtering bleb) that surrounds the plate is such that the amount of fluid that passes through the capsule is identical to the amount of fluid produced by the eye at an intraocular pressure of 8 to 14 mmHg. The most common long-term complication of these implants is failure of the filtering bleb 2 to 4 years after surgery due to the formation of a thick fibrous capsule around the device. Micromovement of the smooth drainage plate against the scleral surface may be integral to the mechanism of glaucoma implant failure by stimulating low-level activation of the wound healing response, increased collagen scar formation, and increased fibrous capsule thickness. To test this hypothesis, we modified seven Baerveldt implants by adding porous cellular ingrowth material to the posterior surface of the drainage plate. Seven modified and five unmodified implants were placed in adult rabbit eyes. After 6 months, we found that the fibrous capsule around the modified implants was significantly thinner than the capsule surrounding the unmodified implants (p < 0.05), particularly on the surface between the porous ingrowth material and the sclera (p < 0.05). Although type I collagen predominated in the fibrous capsules around both types of implants, the amount of type III collagen in the capsules around the modified implants was significantly less than the amount around the unmodified implants (p < 0.05). We believe that these data suggest a reduction in the wound healing response to the modified implants, with greater stability of capsule thickness. Long-term studies are needed to verify that the stability of the capsules around the modified implants persists over a period of years, in which case this type of modification may prove useful in prolonging the functional life of these devices in the surgical treatment of glaucoma.