Increased dynamic stiffness of trabeculae carneae from senescent rats

Dynamic stiffness was measured in both adult and senescent Wistar rats using sinusoidal length perturbations from 17 to 40 Hz, superimposed on isometric contractions at low and below Lmax. The slope of the stiffness-tension relationship was found to be increased in senescent muscles of both sexes and at two different temperatures. The age dependence of the slope was independent of resting muscle length. The slope also exhibited frequency dependence and hysteresis that indicates the presence of viscoelasticity during activation. No age dependence was seen in peak active tension, peak dT/dt, or resting stiffness. The findings of this study, taken together with other studies that have shown a decreased shortening ability in the senescent muscle, explain in part the maintenance of active tension development in the face of decreased shortening ability associated with the senescent muscle.     

Etomidate and fentanyl for maintenance of anaesthesia

An infusion of etomidate and fentanyl was compared with halothane or morphine plus nitrous oxide in oxygen for the maintenance of anaesthesia in 200 patients. Cardiovascular and respiratory changes were found to be similar in the two groups. There was a prolongation of recovery time in the etomidate-fentanyl group: this was possibly a result of lack of flexibility in the infusion technique.