Ricciuti F, Fewell J E
Department of Obstetrics and Gynaecology, University of Calgary, Alberta, Canada.
J Dev Physiol. 1992 Jan;17(1):29-38.
Experiments were done on eight young lambs to investigate the effects of hypoxemia on the body temperature, metabolic and cardiovascular responses to intravenous administration of a small dose of bacterial pyrogen (0.3 micrograms lipopolysaccharide extracted from Salmonella Abortus Equi; SAE). Each lamb was anaesthetized with halothane and prepared for sleep staging and measurements of cardiac output, arterial and mixed-venous haemoglobin oxygen saturations, body-core and ear-skin temperatures. Three experiments were done on each lamb, the first being done no sooner than three days after surgery. The first experiment consisted of establishing the thermal neutral environment during normoxemia (ie, environmental temperature at which total body oxygen consumption was minimal while body temperature was maintained) for each lamb. The second and third experiments were done at the lamb's thermoneutral environment as determined on day 1. One experiment was done during normoxemia (ie, control condition, SaO2 approximately 90%) and one experiment was done during hypoxemia (ie, experimental condition, SaO2 approximately 50%). Measurements were made during a control period and during one-minute experimental periods at 10 minute intervals for 120 minutes following administration of 0.3 micrograms of bacterial pyrogen in sterile saline. Administration of SAE produced a short-lived fever of about 0.8 degrees C in the normoxemic lambs, whereas no change in body-core temperature was observed in the hypoxemic lambs. During normoxemia, the increase in body-core temperature was preceded by peripheral vasoconstriction, the onset of shivering, and a surge in total body oxygen consumption. The increase in total body oxygen consumption was met primarily by an increase in total body oxygen extraction during the development of fever. Cardiac index, heart rate, and systemic oxygen transport increased during the peak body-core temperature response. Systemic arterial blood pressure did not change significantly during the febrile response; however, pulmonic arterial blood pressure increased. During hypoxemia, peripheral vasoconstriction and shivering occurred following administration of SAE, but there was no change in total body oxygen consumption or body-core temperature. Thus, our data provide evidence that hypoxemia alters the febrile response of young lambs to bacterial pyrogen. The precise mechanism remains to be determined.
对八只幼羊进行了实验，以研究低氧血症对体温、代谢以及静脉注射小剂量细菌热原（从马流产沙门氏菌中提取的0.3微克脂多糖；SAE）后心血管反应的影响。每只羊用氟烷麻醉，并准备进行睡眠分期以及测量心输出量、动脉和混合静脉血红蛋白氧饱和度、体核温度和耳皮肤温度。每只羊进行了三项实验，第一项实验在手术后至少三天进行。第一项实验包括为每只羊在常氧血症期间（即全身氧消耗最小且体温保持稳定时的环境温度）建立热中性环境。第二项和第三项实验在第1天确定的羊的热中性环境下进行。一项实验在常氧血症期间（即对照条件，SaO2约为90%）进行，另一项实验在低氧血症期间（即实验条件，SaO2约为50%）进行。在无菌盐水中注射0.3微克细菌热原后的120分钟内，在对照期和以10分钟为间隔的一分钟实验期内进行测量。SAE的给药在常氧血症的羔羊中产生了约0.8摄氏度的短暂发热，而在低氧血症的羔羊中未观察到体核温度变化。在常氧血症期间，体核温度升高之前出现外周血管收缩、寒战发作以及全身氧消耗激增。在发热过程中，全身氧消耗的增加主要通过全身氧摄取的增加来满足。在体核温度反应达到峰值时，心脏指数、心率和全身氧运输增加。在发热反应期间，全身动脉血压没有显著变化；然而，肺动脉血压升高。在低氧血症期间，SAE给药后出现外周血管收缩和寒战，但全身氧消耗或体核温度没有变化。因此，我们的数据提供了证据，表明低氧血症改变了幼羊对细菌热原的发热反应。确切机制仍有待确定。
