Metabolic limits on dive duration and swimming speed in the southern elephant seal Mirounga leonina.

The ability of air-breathing marine predators to forage successfully depends on their ability to remain submerged. This is in turn related to their total O(2) stores and the rate at which these stores are used up while submerged. Body size was positively related to dive duration in a sample of 34 adult female southern elephant seals from Macquarie Island. However, there was no relationship between body size and dive depth. This indicates that smaller seals, with smaller total O(2) stores, make shorter dives than larger individuals but operate at similar depths, resulting in less time being spent at depth. Nine adult female elephant seals were also equipped with velocity time depth recorders. In eight of these seals, a plot of swimming speed against dive duration revealed a cloud of points with a clear upper boundary. This boundary could be described using regression analysis and gave a significant negative relationship in most cases. These results indicate that metabolic rate varies with activity levels, as indicated by swimming speed, and that there are quantifiable limits to the distance that a seal can travel on a dive of a given swimming speed. However, the seals rarely dive to these physiological limits, and the majority of their dives are well within their aerobic capacity. Elephant seals therefore appear to dive in a way that ensures that they have a reserve of O(2) available.

Interscalene brachial plexus blocks in the management of shoulder dislocations.

Interscalene brachial plexus block is a simple and effective alternative to intravenous benzodiazepines or general anaesthesia for manipulation of the dislocated shoulder. Thirty interscalene brachial plexus blocks were performed on 29 patients with dislocations of the shoulder to provide regional anaesthesia for reduction. Pain was abolished by 14 out of the 30 blocks performed, improved by 13 and unchanged by three. Muscle relaxation (MRC grade 3 or less) occurred in 21 patients. In 26 cases the block allowed reduction of the dislocation without additional analgesia or sedative. Reduction was not possible in four cases. There were no significant complications.