The effects of 7.5％ NaCl-6％ dextran 70 in small dosage on the cardiovascular func-tion and the survival rate in hemorrhagic shock at a simnlated altitude of 4000 m were observedin dogs.The animals were bled from the...The effects of 7.5％ NaCl-6％ dextran 70 in small dosage on the cardiovascular func-tion and the survival rate in hemorrhagic shock at a simnlated altitude of 4000 m were observedin dogs.The animals were bled from the femoral artery for 8 rain to reduce the mean arterialpressure to 5.73±0.1kPa,which was maintained for an hour.Then the dogs were intravenouslyinjected with 4ml/kg 0.9％ NaCL(NS group,n=7),7.5％ NaCl(HS group,n=6)and 7.5％Naa-6％ dextran 70(HSD group,n=6)respectively.In the 2-hour-period after injection,5out of 7 dogs of NS group died but only 1 out of the 6 of both the HS and HSD groupsdied.Significant increase of mean arterial pressure,left ventricular pressure,±dp/dt max of leftventricle,cardiac output,cardiac index and cardiac minute work index was observed in both theHS and HSD groups.Improvement of the cardiovascular function was even more marked inHSD group than in HS group,thougth the difference between the 2 groups was statisticallyinsignificant.There was a tendency for the pulmonary vascular resistance to decrease in HS andHSD groups as compared with the NS group.The percentage of plasma expansion of HSDgroup was larger than that of HS group(P【0.05)and of NS group(P【0.01),but nosignificant difference existed between the HS and NS groups.It is believed that intravenous injection of hypertonic saline alone or in combination with dextran is effective for the treatment ofhemorrhagic shock at high altitude and the combination of 7.5％ NaCl and 6％ dextran 70seems even more effective.展开更多
To determine the effects of sympathetic denervation and dexamethasone on the individualcerebral vascular pressure profile during hypoxia, the authors measured the pial microvascular pres-sure in 24 anesthetized rabbit...To determine the effects of sympathetic denervation and dexamethasone on the individualcerebral vascular pressure profile during hypoxia, the authors measured the pial microvascular pres-sure in 24 anesthetized rabbits with a servo-null system. At a simulated altitude of 4000 meters, inthe intact group, the mean pressure in pial arterioles of 50-70 μm in diameter decreased markedly.The ratio of pressure drop between the upstream and downstream of the arteriole measured in-creased markedly, and the blood flow in the internal carotid artery was nearly doubled of the nor-mal. The pial arteriolar pressures of both the denervated and dexamethasone groups were significantlyhigher than that of the intact group, but were not different from their prehypoxic values. The ratioof pressure drop between the upstream and downstream of the denervated and dexamethasonegroups remained unchanged, and much lower than that of the intact group, These results lead tothe following conclusions: (1) Sympathetic nerves and dexamethasone exert no effect on thelongitudinal distribution of cerebro-vascular pressure in rabbits during normoxia, normocapnia andnormotension.(2) During hypoxia, pressure drop increases in the upstream arteries and/or decreasesin the downstream vessels of the microvascular pressure measured site (arterioles 50- 70 μm in diame-ter) partly due to the activation of the sympathetic nerve. (3) Dexamethasone can prevent theredistribution of cerebrovascular pressure induced by hypoxia, which can partly explained the ac-tion of dexamethasone in preventing high altitude sickness.展开更多
The effects of chronic hypoxia on calmodulin levels of lung tissues and small pulmonary ar-terial walls were studied in young pigs, The tissue specimens of hypoxic animals were obtained underhypoxic conditions. The fo...The effects of chronic hypoxia on calmodulin levels of lung tissues and small pulmonary ar-terial walls were studied in young pigs, The tissue specimens of hypoxic animals were obtained underhypoxic conditions. The following results were collected:(1) The swine exposed to chronic intermittent hypoxia showed a significant pulmonary pressor re-sponse at a simulated high altitude of 4000 m.(2) A higher level of calmodulin was found in the lung tissues of chronic hypoxic animals. It maybe related to the increased release of some vaosactive substances from pulmonary non-muscularcalls.(3) No significant difference of calmodulin level of small arterial walls was demonstrated between theexperimental animals and the control.The findings suggest that pulmonary vasoconstriction due to hypoxia is not likely to be associatedwith obvious change in calmodulin level in the smooth muscle of blood vessels.展开更多
文摘The effects of 7.5％ NaCl-6％ dextran 70 in small dosage on the cardiovascular func-tion and the survival rate in hemorrhagic shock at a simnlated altitude of 4000 m were observedin dogs.The animals were bled from the femoral artery for 8 rain to reduce the mean arterialpressure to 5.73±0.1kPa,which was maintained for an hour.Then the dogs were intravenouslyinjected with 4ml/kg 0.9％ NaCL(NS group,n=7),7.5％ NaCl(HS group,n=6)and 7.5％Naa-6％ dextran 70(HSD group,n=6)respectively.In the 2-hour-period after injection,5out of 7 dogs of NS group died but only 1 out of the 6 of both the HS and HSD groupsdied.Significant increase of mean arterial pressure,left ventricular pressure,±dp/dt max of leftventricle,cardiac output,cardiac index and cardiac minute work index was observed in both theHS and HSD groups.Improvement of the cardiovascular function was even more marked inHSD group than in HS group,thougth the difference between the 2 groups was statisticallyinsignificant.There was a tendency for the pulmonary vascular resistance to decrease in HS andHSD groups as compared with the NS group.The percentage of plasma expansion of HSDgroup was larger than that of HS group(P【0.05)and of NS group(P【0.01),but nosignificant difference existed between the HS and NS groups.It is believed that intravenous injection of hypertonic saline alone or in combination with dextran is effective for the treatment ofhemorrhagic shock at high altitude and the combination of 7.5％ NaCl and 6％ dextran 70seems even more effective.
文摘To determine the effects of sympathetic denervation and dexamethasone on the individualcerebral vascular pressure profile during hypoxia, the authors measured the pial microvascular pres-sure in 24 anesthetized rabbits with a servo-null system. At a simulated altitude of 4000 meters, inthe intact group, the mean pressure in pial arterioles of 50-70 μm in diameter decreased markedly.The ratio of pressure drop between the upstream and downstream of the arteriole measured in-creased markedly, and the blood flow in the internal carotid artery was nearly doubled of the nor-mal. The pial arteriolar pressures of both the denervated and dexamethasone groups were significantlyhigher than that of the intact group, but were not different from their prehypoxic values. The ratioof pressure drop between the upstream and downstream of the denervated and dexamethasonegroups remained unchanged, and much lower than that of the intact group, These results lead tothe following conclusions: (1) Sympathetic nerves and dexamethasone exert no effect on thelongitudinal distribution of cerebro-vascular pressure in rabbits during normoxia, normocapnia andnormotension.(2) During hypoxia, pressure drop increases in the upstream arteries and/or decreasesin the downstream vessels of the microvascular pressure measured site (arterioles 50- 70 μm in diame-ter) partly due to the activation of the sympathetic nerve. (3) Dexamethasone can prevent theredistribution of cerebrovascular pressure induced by hypoxia, which can partly explained the ac-tion of dexamethasone in preventing high altitude sickness.
文摘The effects of chronic hypoxia on calmodulin levels of lung tissues and small pulmonary ar-terial walls were studied in young pigs, The tissue specimens of hypoxic animals were obtained underhypoxic conditions. The following results were collected:(1) The swine exposed to chronic intermittent hypoxia showed a significant pulmonary pressor re-sponse at a simulated high altitude of 4000 m.(2) A higher level of calmodulin was found in the lung tissues of chronic hypoxic animals. It maybe related to the increased release of some vaosactive substances from pulmonary non-muscularcalls.(3) No significant difference of calmodulin level of small arterial walls was demonstrated between theexperimental animals and the control.The findings suggest that pulmonary vasoconstriction due to hypoxia is not likely to be associatedwith obvious change in calmodulin level in the smooth muscle of blood vessels.
