[Improvement of cerebral oxidative metabolism and cytochrome aa3 redox state by 7.5% hypertonic saline during hemorrhagic hypotension in dogs].

Our previous study reported that 20% (1.5 ml.kg-1 hypertonic saline could significantly improve the disturbances of cerebral oxidative metabolism induced by hemorrhagic hypotension in dogs. The aim of the present study is to evaluate if 7.5% hypertonic saline induces circulatory improvement. Ten dogs were randomly divided into two groups of 5 each resuscitated with either physiological saline as control or 7.5% hypertonic saline (4 ml.kg-1) after their mean arterial blood pressure decreased to 35 mmHg for 45 minutes by hemorrhage. The changes of cerebral tissue oxy- and deoxyhemoglobin, cerebral blood volume (total hemoglobin), and oxy-cytochrome aa3 were continuously monitored by near infrared spectroscopy throughout the experiment. The experimental result showed that oxy-hemoglobin, oxy-cytochrome aa3, and cerebral blood volume decreased but deoxyhemoglobin increased significantly 45 minutes after hemorrhage. Treatment with 7.5% hypertonic saline significantly restored these variables except for cerebral blood volume and all the animals survived to the end of experiment. But in the control group treated with the same dose of physiological saline, the above variables improved little compared with the baseline; and all the animals died before the end of 60 min experimental observation. Therefore we conclude that 7.5% hypertonic saline (4 ml.kg-1) can also effectively improve the disturbance of cerebral oxidative metabolism induced by hemorrhagic hypotension.