A comparison of renal responses to sevoflurane and isoflurane in patients undergoing donor nephrectomy: a randomized controlled trial

Sevoflurane and isoflurane are volatile halogenated ether widely used in anesthesia. Both have comparable potency and easy titratability but sevoflurane has lower pungency and results in faster patient recovery. Isoflurane, however, is more affordable. The nephrotoxicity of sevoflurane is undisputed but studies on isoflurane nephrotoxicity are lacking. The objective of this paper is to determine the overall nephrotoxicity profile of sevoflurane and isoflurane in donor nephrectomy patients using the renal function markers - nuclear glomerular filtration rate (GFR), serum creatinine, urine protein-to-creatinine ratio, proteinuria, and glucosuria. A randomized comparative study of postoperative renal functions in donor nephrectomy patients who had received either low-flow (< 1 L/min) sevoflurane or isoflurane were analyzed. The renal parameters were repeated 72 hours post anesthesia. Forty-seven subjects (46%) were randomized to receive isoflurane while fifty-five received sevoflurane (54%). Between the two anesthetic groups, there was no significant difference in terms of serum creatinine, total GFR, or nuclear GFR. There was a statistically higher proportion of patients with urine protein-to-creatinine ratios of 0.2 and above in the isoflurane group (64% vs. 38%), while more patients in the sevoflurane group had ratios above 0.2 (62% vs. 36%, P < 0.05). The type of anesthetic agent was not an independent predictor of increasing serum creatinine, total GFR and urine protein-to-creatinine ratio and nuclear GFR. In conclusion, the overall nephrotoxicity profile of sevoflurane and isoflurane-treated donor nephrectomy patients is minimal.

Disruption of a tight cluster surrounding tyrosine 131 in the native conformation of antithrombin III activates it for factor Xa inhibition

The native conformation of antithrombin III (ATIII) is a poor inhibitor of its coagulation pathway target enzymes because of the partial insertion of its reactive center loop (RCL) in its central A beta-sheet. This study focused on tyrosine 131, which is located at the helix D-sheet A interface, adjacent to the ATIII pentasaccharide and heparin cofactor-binding sites and some 17A away from the RCL insertion. Crystallographic structures show that the Tyr(131) ring is buried in native ATIII and then becomes exposed when pentasaccharide binds to the inhibitor and activates it. This change suggested that Tyr(131) might serve as a switch for ATIII conformational activation. The hypothesis is supported by results from this study, which progressively removed atoms from the Tyr(131) side chain. Rates of heparin-independent Y131L and Y131A factor Xa inhibition were 25 and 29 times faster than for the control and Y131F, suggesting that Tyr(131) ring interactions with neighboring helix D and strand 2A residues shift the uncatalyzed native-to-activated conformational equilibrium toward the RCL-inserted state. Thermal denaturation experiments showed Y131A and Y131L were less stable than the control and Y131F, implying an increased tendency toward A-sheet mobility in these genetically activated molecules. Thus, the tight Tyr(131)-Asn(127)-Leu(130)-Leu(140)-Ser(142) cluster at the helix D-strand 2A interface of native antithrombin contributes significantly to the stability of the ground state conformation, and tyrosine 131 serves as a heparin-responsive molecular switch during the allosteric activation of ATIII anticoagulant activity.