The effect of anaesthesia on the bone blood flow of the rabbit

The effect of anaesthesia on the rate of bone blood flow in the rabbit was studied. Two estimates of bone blood flow were performed, using 15 microns radioactively labelled microspheres, in three groups of rabbits. The first group was anaesthetised and the interval between the two estimates was 5 min. The second group was also anaesthetised but the interval between estimates was 60 min. The third group of rabbits was conscious and the interval between the two estimates was 4 h. In the first group, small uniform falls in whole bone blood flow were observed (mean change = -5%). In the second group, larger and less predictable reductions were observed (mean change = -24%). In the third group (conscious), little change was observed in whole bone blood flow during the 4-h experiment (mean change = +7%). It is concluded that substantial falls can occur in bone blood flow in the rabbit during a 1-h anaesthetic. If bone blood flow is to be monitored under anaesthesia, then the effect of the anaesthetic on bone blood flow must be accurately defined. In conscious rabbits, estimates of whole bone blood flow performed at an interval of 4 h under control conditions will give reproducible results.