Resonances from carbons bonded to nitrogen are often broadened and split into asymmetric doublets in 13C NMR spectra of polycrystalline organic molecules obtained with proton decoupling and magic-angle sample spinning.

The dipolar coupling between 14N and 13C is not suppressed by magic angle sample spinning because the relatively large 14N quadrupole interaction shifts the axis of quantization of the 14N spins away from the direction of the applied field. The resulting 13C resonance line shapes are influenced by the sign, magnitude, and asymmetry parameter of the 14N quadrupole coupling tensor; the internuclear distance; the magnitude of the applied magnetic field; and the orientation of the internuclear vector in the principal axis system of the electric field gradient. It is demonstrated that one or more of these parameters can be determined from the 13C NMR data if the others are known by virtue of single crystal studies or molecular symmetry.

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Insulin regulates glucose and potassium metabolism by acting differently upon peripheral tissues (e.g., skeletal muscle) and the splanchnic bed, including the liver. Liver disease is accompanied by "insulin resistance" of glucose metabolism, whereby glucose intolerance occurs despite relatively increased plasma insulin concentration. However, it is unknown whether insulin resistance extends to potassium metabolism. Further, it is uncertain whether the hyperglycemia and alterations of plasma potassium concentration observed during liver transplantation result from changes in circulating insulin concentration, altered sensitivity to insulin, or both, as the diseased liver is removed and replaced with a graft organ. The present study evaluated the role of the liver in maximal insulin responsiveness of whole-body glucose and potassium metabolism, using a hyperinsulinemic clamp technique, to identify the mechanism@) underlying post-reperfusion hyperglycemia and intraoperative hyperkalemia. Two protocols were employed: In protocol 1 (n = lo), no exogenous insulin was administered. In protocol 2 (n = lo), an intravenous insulin bolus (666 mU -kg-') was administered after anesthesia induction, followed by an infusion at 500 mU * m-*-min-l, which continued until 3 hours after portal vein unclamping. Plasma concentrations of glucose and potassium were regulated by glucose and potassium chloride infusion (euglycemic eukalemic clamp). Insulin-stimulated exogenous glucose and potassium uptakes were determined in protocol 2 before skin incision and during the dissection, anhepatic, and neohepatic stages. In both protocols, serial measurements of hemodynamic arterial blood gases, glucose, free fatty acids, potassium, insulin, and glucagon concentrations were made. Without insulin (protocol l), progressive hyperglycemia peaked after portal vein unclamping (postreperfusion hyperglycemia), with no concomitant decrease in plasma insulin concentration. Intraoperative plasma potassium concentration did not change. Insulin infusion (protocol 2) produced a stable hyperinsulinemia (-2000 pU/mL). Hyperinsulinemia did not eliminate post-reperfusion hyperglycemia. Insulin-stimulated glucose uptake, Copyright o 1996 by the American Association for the Study of Liver Diseases atients with liver disease are resistant to the P hypoglycemic action of insulin, which manifests as a spectrum from mild glucose intolerance to overt diabetes mellitus. 1-5 The disturbance of glucose metabolism is exacerbated during orthotopic liver transplantation (OLT) , during which hyperglycemia peaks after reperfusion of the graft liver (post-reperfusion hyperglycemia) and persists into the postoperative ~e t t i n g .~.~ Many patients require insulin therapy during and after OLT for control of plasma glucose concentration. It remains unclear, however, whether postreperfusion hyperglycemia stems from hypoinsulinemia, decreased peripheral sensitivity to insulin, or increased glucose output by the graft liver.

A four-phase proportional-integral-derivative (PID) controller was evaluated under the extremely unstable conditions of liver transplantation. Vecuronium was delivered to achieve 80%-90% neuromuscular blockade as measured by electromyogram (EMG). The first two controller phases delivered boluses and a constant infusion calculated to rapidly achieve setpoint, followed by a proportional-derivative (PD) phase at 35% from setpoint, and PID within 10% of the setpoint. During liver transplantation, the sources of system instability included large blood losses, temperature changes, and loss of hepatic drug metabolism during removal and replacement. During prolonged surgery, and when blood losses were not severe, the EMG remained within 10% of setpoint. Controller performance was more variable during system instability. Plasma sampling and two-compartment modelling of the infusion and response with a weighting factor for blood loss allowed estimation of the sources and degree of instability for improved design of future controllers.