COLLOID VERSUS CRYSTALLOID COLOAD FOR THE PREVENTION OF SPINAL ANEASTHESIA INDUCED HYPOTENSION OF ELECTIVE CAESAREAN SECTION

Background Spinal anaesthesia is the standard technique for elective caesarean section, but hypotension remains the main complication with this technique. This hypotension has detrimental effects on both mother and foetus. To prevent hypotension, crystalloid or colloid coload with vesopressor may be an alternate choice. Aim To compare the efficacy of crystalloid and colloid coload in presence of phenylephrine infusion for the prevention of spinal anaesthesia induced hypotension. Methods Forty subjects (40) are randomly allocated into two groups. Subjects were infused either crystalloid or colloid within 10 minutes after spinal anaesthesia (coload).Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP) and oxygen saturation were recorded in three minutes interval throughout the surgery. Continuous ECG monitoring was done. Adverse events (nausea, vomiting etc) if any were recorded in case report form (CRF).  Phenylephrine infusion was continued at the rate of 40 mcg/min throughout the surgery. Results Demographic parameters were comparable. HR, SBP, DBP, MBP, Oxygen saturation all are comparable between the groups and within the group in various time period. There was no episode of nausea or vomiting and no requirement of rescue medication of phenylephrine 100 mcg intravenously. Conclusion There is no difference of efficacy of crystalloid and colloid, when use as coload with phenylephrine infusion for the prevention of spinal anaesthesia induced hypotension.   Key words –spinal anaesthesia, crystalloid, colloid, hypotensio

Understanding the anomalous behavior of Vegard's law in Ce1-xMxO2 (M = Sn and Ti; 0 < x <= 0.5) solid solutions

The dependence of the lattice parameter on dopant concentration in Ce1-xMxO2 (M = Sn and Ti) solid solutions is not linear. A change towards a steeper slope is observed around x similar to 0.35, though the fluorite structure (space group Fm3m) is preserved up to x = 0.5. This phenomenon has not been observed for Ce1-xZrxO2 solid solutions showing a perfectly linear decrease of the lattice parameter up to x = 0.5. In order to understand this behavior, the oxidation state of the metal ions, the disorder in the oxygen substructure and the nature of metal-oxygen bonds have been analyzed by XPS, Sn-119 Mossbauer spectroscopy and X-ray absorption spectroscopy. It is observed that the first Sn-O coordination shell in Ce1-xSnxO2 is more compact and less flexible than that of Ce-O. The Sn coordination remains symmetric with eight equivalent, shorter Sn-O bonds, while Ce-O coordination gradually splits into a range of eight non-equivalent bonds compensating for the difference in the ionic radii of Ce4+ and Sn4+. Thus, a long-range effect of Sn doping is hardly extended throughout the lattice in Ce1-xSnxO2. In contrast, for Ce1-xZrxO2 solid solutions, both Ce and Zr have similar local coordination creating similar rearrangement of the oxygen substructure and showing a linear lattice parameter decrease up to 50% Zr substitution. We suggest that the localized effect of Sn substitution due to its higher electronegativity may be responsible for the deviation from Vegard's law in Ce1-xSnxO2 solid solutions