The oxidation of ferrous ions by dissolved oxygen in aqueous solutions in the presence of such chelating agents as EDTA, DTPA, EDTAOH, EDTP, CyDTA and NTA was studied spectrophotometrically. The rate equation for the oxidation reaction is: d[Fe^III]/dt=4k_p[Fe^IIHZ][O_2]+4k_n[Fe^IIZ][O_2] where kp is the rate constant for the (1) reaction; kn, the rate constant for the (2) reaction; FeIIHZ, protonated chelate, and FeIIZ, the normal chelate. &Fe^IIHZ+O_2\xrightarrowk_pFe^IIIZ+HO_2 \labeleq1 &Fe^IIZ+O_2\xrightarrowk_nFe^IIIZ+O_2^-\labeleq2 The linear relationship between log k and log Rf shown by Eq. (3), was obtained from all the experimental results except for those on the EDTPA and CyDTA systems: logk=0.92+0.13logR_f\labeleq3 In Eq. (3), k is 4kp and Rf is KFeIIIL⁄KFeIIHL, for the protonated chelate, while k is 4kn and Rf is KFeIIIL⁄KFeIIL for the normal chelate. In the cases of the DTPA and CyDTA systems, a deviation from the straight line was observed. This can be explained by steric hindrance of the oxygen attack by these chelates.

HighlightsPresacral epidermoid cysts are extremely rare and require further study.Thorough preoperative imaging evaluation is important for complete resection.Multidisciplinary treatments may be effective.Presacral epidermoid cysts may be malignant.

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Objective:Thepurposeofthisstudywastoclarifytheoutcomesandprognosticfactorsafterpalliativesurgeryinpatientswithmalignantbowelobstructionduetoperitonealdissemination. Methods:Theclinicalrecordsof58patientswereretrospectivelyreviewed,andclinicalfactorsassociatedwithapoorprognosiswereevaluated.Theclinicalfactorsanalyzedinthisstudywereage,sex,performance status (PS), primary malignancy, resection of primary tumor, number of bowel obstructions, amount of ascites, grade of peritoneal metastasis, other distant metastasis, Glasgow Prognostic Score (GPS),PrognosticNutritionIndex,andNeutrophil/LymphocyteRatio. Results:Palliative surgery enabled 84.5% of the patients to resume solid diets and 89.7% of the patientstobedischargedfromthehospital.Thecomplicationrarewas31.0%,andthemediansurvivaltime afterpalliativesurgerywas5.1months.Patientswhoreceivedpostoperativechemotherapylongerthan8 weeksshowedasignificantlybetterprognosisthanpatientswhoreceivedbestsupportivecareorpostoperative chemotherapy shorter than 8 weeks. Multivariate analysis showed male (p ＜0.001), PS 3-4 (p=0.002), moderate/massive ascites (p ＜0.001), multiple bowel obstructions (p=0.001), and GPS of 2 (p=0.01)wereindependentfactorsrelatedtoapoorprognosis. Conclusions:Theoutcomesofpalliativesurgeryinourhospitalwerecomparabletothoseofprevious reports. Palliative surgery might be less indicated for patients with the factors associated with a poor prognosis.

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