EFFECTS OF RESUSCITATIVE HYPOTHERMIA ON LIQID PEROXIDATION AND EDEMA OF BRAIN IN RABBITS*

Abstract

S242 INTRODUCTION: Resuscitative (postinsult) hypothermia is less well studied than protective-preservative (pre- and intra-arrest hypothermia [1]. Many patients with cardiopulmonary arrest have been successfully resuscitated with hypothermia in China since 1950 [2]. However, resuscitative hypothermia was hardly clinically used in the West [1]. In order to approach the mechanism of resuscitative hypothermia, we examined the its influences on liqid peroxidation and edema of brain. METHODS: With institute approval, 48 New Zealand rabbits (1.8-2.2 kg, aged 3-5 months) were randomly divided into three large (eight small) groups (see Table 1). The animals were anesthetized with pentobarbitol. After tracheotomy was performed, mechanical ventilation was instituted (ET-CO2 4.5-6%). Animals were monitored EKG, EEG, respiratory and circulatory functions and were critically cared and were maintained stable. The four vessel complete cerebral ischemia [3] was modeled for 18 minutes, following by cerebral reperfusion. In normothermia group, the temperature was kept the same level as preischemia. During the reperfusion period, hypothermia was achieved by immersing the animal's head and neck into ice water. The brain temperature was decreased 27-30 [degree sign]C while 30 minutes and then was kept at this level, and rectal temperature was kept at the level 30-34 [degree sign]C. About 1 g right temporal cerebral cortex were taken from alive animal for water content [4]. About 1 g right parietal cerebral cortex were taken from alive animal and then preserved in liquid nitrogen for liqid peroxidation. The cortex was homogenized with 0.9% NaCl (1g:9ml). Contents of malondialdehyde (MDA) and glutathione (GSH) were measured by Ohkawa's method [5] and Lei method [6]. Homogenations were centrifuged (20,000 g, 30 min at 0-4 [degree sign]C). Superoxide dismutase (SOD) activity was measured by Marklund's method [7]. Data were made by analysis of Student's t test and ANOVA. Satistical significance was set at P<0.05.Table 1RESULTS: The results showed in figures. There were significant differences between the normothermia and hypothermia at any time point (P<0.01). DISCUSSIONS: Our results indicate that resuscitative hypothermia could inhibit the accumulation of peroxidation products, increase the activities of enzymatic and nonenzymatic free radical scavenge systems, and decrease the edema of brain during reperfusion period. The mechanisms responsible for the beneficial effects may include minimized energy failure, reduced ATP consumption, inhibited lipids perioxidations and depressed intracellular acidosis. Figure 1Figure 1This study was partially supported by the grant of National Nature Science Foundation of China, No. 39370569