Effects of shivering on airway rewarming / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effects of shivering on airway rewarming.</p><p><b>METHODS</b>The hypothermic dog model without shivering was established by immersing an anesthetized dog in cold water and administering atracurium to inhibit the dog shivering. The model dog respired warm fully humidified (40-45 degrees C, RH 99.9%) air and room temperature air(19 +/- 1 degrees C, RH 30% - 75%) to rewarm each for 2 hours, the priority of different temperature air respired was arranged randomly. After rewarming for 4 hours, the relaxed dog breathed warm humidified air by positive pressure ventilation in order to restore its spontaneous respiratory. Then the dog continued to respire warm humidified air spontaneously until the esophageal (Te) and rectal temperature (Tr) of the dog achieved the same degrees as the dog was immersed in the water. The metabolic heat production was detected by indirect calorimetry during the experiment.</p><p><b>RESULTS</b>(1) When the shivering was inhibited, inhaling warm humidified air for 2 hours made the Tr and Te of the dogs increase 0.26-0.39 degrees C and 0.44-1.11 degrees C per hour respectively, inhaling air at room temperature for 2 hours made Tr and Te of the dogs decrease 0.24-0.51 degrees C and 0.58-0.67 degrees C per hour, respectively. And the changes in Tr and Te of the dogs were unrelated to the priority of inhaling air at different temperature. (2) When the dog with shivering respired spontaneously warm humidified air, the rewarming rates of Tr and Te were 2.26-2.33 degrees C/h and 1.96-2.38 degrees C/h respectively, quicker than those of the dogs whose shivering was inhibited. (3) Compared with metabolic heat production of the unshivering dog respiring warm humidified air by positive pressure ventilation, that of the shivering dog respiring warm humidified air spontaneously increased outstandingly, shivering thermogenesis made the rewarming rates increased obviously.</p><p><b>CONCLUSION</b>Airway rewarming is a method conducive to rewarming of hypothermia. When the body is shivering, the metabolic heat production increases obviously, that makes the rewarming rate increase markedly. So the shivering must be inhibited in order to eliminate the interference of shivering thermogenesis when the effects of airway rewarming are detected.</p>

Establishment of a hypothermic dog model to investigate airway rewarming / 中国应用生理学杂志

<p><b>AIM</b>In order to study airway rewarming method and rewarming devices for hypothermia, hypothermic dog model was established.</p><p><b>METHODS</b>The anesthetized dog was immersed in cold water at 16.7 degrees C until the esophageal temperature (Te) of the dog decreased to 34.0 degrees C, the core temperature and skin temperature were monitored by using a 12-channel scanning thermometers. Atracurium besylate, a skeletal muscle relaxant, was injected intravenously when the core temperature of the dog was basically steady after the dog was out of the cold water, the hypothermic dog model was established.</p><p><b>RESULTS</b>Rectal and esophageal temperature could stand for the core temperature of the hypothermic dog model, but mixing with each other was prohibited because of leading to mistakes. Administering of atracurium besylate could eliminate the effect of shivering on airway rewarming alone, hypothermic dog model in which shivering was inhibited could be used in determination of airway rewarming technique and rewarming devices for hypothermia.</p><p><b>CONCLUSION</b>Hypothermic dog model in which shivering was inhibited can abolish the interference of shivering, experimental repeatability is good, experimental method quite simple, and the model appropriate for application and dissemination.</p>

Role of cellular adhesion molecule ICAM-1 in freezing/thawing injury of vascular endothelial cells / 中国应用生理学杂志

<p><b>AIM</b>To investigate the role of ICAM-1 on the surface of vascular endothelial cell (VEC) in freezing/thawing injury of VEC, in order to elucidate the pathogenesis of freezing/thawing injury.</p><p><b>METHODS</b>VEC separated and cultured from rat aorta and PMN separated from rat peripheral blood were selected as experiment materials. The frozen/thawed VEC model was founded by freezing VEC with the type WKL-V rate cooling instrument and then rewarming them in a water bath. ICAM-1 expression on the surface of frozen/thawed VEC was detected at 4, 12 and 24 h after freezing/thawing with immunohistochemical method. After coincubating frozen/thawed VEC with normal PMN, the adhesion of VEC to PMN was monitored with rose bengal staining assay and the injury level of VEC was indicated by measuring LDH activity in nutrient solution.</p><p><b>RESULTS</b>The ICAM-1 expression on the surface of VEC increased from 13.2% +/- 3.6% before freezing/thawing of VEC to 22.3% +/- 4.4% at 4 hour after freezing/thawing, and reached the peak (37.9% +/- 2.5%) at 12 hour after freezing/thawing of VEC. After coincubation of frozen/thawed VEC with normal PMN, the adherence of frozen/thawed VEC to PMN increased from group control 0.204 +/- 0.025 to 0.363 +/- 0.022 (P < 0.01), LDH activity in nutrient solution increased from group control 104.64 +/- 20.14 U/L to 162.33 +/- 27.88 U/L (P < 0.01), monoclonal antibody against ICAM-1 (ICAM-1 Mab) could partially block the adherence of frozen/thawed VEC to PMN (0.270 +/- 0.021, P < 0.01), and diminish LDH activity in nutrient solution (125.39 +/- 22.26 U/L, P < 0.05).</p><p><b>CONCLUSION</b>The freezing/thawing of VEC can elicit an increase in ICAM-1 expression on the surface of VEC, and then proceed to VEC-PMN adherence and lead to VEC injury.</p>