环境低温对非麻醉猪失血性休克血流动力学及氧代谢的影响

目的 探讨环境低温对非麻醉猪失血性休克血流动力学及氧代谢的影响.方法 沈阳军区总医院动物中心提供的巴马香猪16头随机(随机数字法)分为:室温休克组和低温休克组,每组8头.按30 mL/kg放血建立失血性休克模型,记录建模前及建模后4h内不同时点的核心体温、心率、平均动脉压、中心静脉压、心输出量、混合静脉血氧饱和度及血气等变化,并计算氧摄取率、氧供指数和氧耗指数.采用SPSS11.0软件包行计量资料的成组t检验.结果 模型建立后室温组动物的核心体温略有下降,环境低温使核心体温下降更加明显.低温组动物的病死率较室温组明显增加(P＜0.05).休克导致氧供和氧耗明显下降.室温组和低温组的血流动力学指标、氧供和氧耗的差异无统计学意义,但两者在pH值、乳酸和氧提取率上差异具有统计学意义(P＜0.05).结论 环境低温加重了失血性休克后的氧代谢紊乱,使预后进一步恶化.     

麻醉对猪失血性休克模型血流动力学及氧动力学的影响

目的 探讨麻醉对猪失血性休克血流动力学及氧动力学的影响.方法 巴马香猪16头随机分为:麻醉休克组和清醒休克组,每组8头.按30 mL/kg放血建立失血性休克模型,记录建模前及建模后4 h内不同时点的核心体温、心率(HR)、平均动脉压(MAP)、肺动脉压(PAP)、肺动脉楔压(PAWP)、中心静脉压(CVP)、心输出量(CO)、血红蛋白(Hb)、混合静脉血氧饱和度(SvO2)及血气分析变化,并计算氧摄取率(O2ER)、氧供指数(DO2I)和氧耗指数(VO2I).结果 模型建立后清醒组动物核心体温略有下降,但麻醉组动物核心体温下降更加明显.两组的HR、MAP、PaO2、PaCO2及pH值未表现出明显差异,但清醒组乳酸水平明显高于麻醉组.尽管模型建立后两组的DO2I和VO2I都出现了相同幅度的下降,但清醒组的DO2I、VO2I和O2ER在模型建立前后都显著高于麻醉组.结论 麻醉可以减轻失血性休克后的氧代谢紊乱,麻醉引起的诱导性低温可能是造成这种现象的原因.     

Effects of hypothermia on the liver in a swine model of cardiopulmonary resuscitation

BACKGROUND:

The study aimed to explore the effects of hypothermia state induced by 4 ºC normal saline (NS) on liver biochemistry, enzymology and morphology after restoration of spontaneous circulation (ROSC) by cardiopulmonary resuscitation (CPR) in swine.

METHODS:

After 4 minutes of ventricular fibrillation (VF), standard CPR was carried out. Then the survivors were divided into two groups: low temperature group and normal temperature group. The low temperature (LT) group (n=5) received continuously 4 ºC NS at the speed of 1.33 mL/kg per minute for 22 minutes, then at the speed lowering to 10 mL/kg per hour. The normal temperature (NT) group (n=5) received NS with normal room temperature at the same speed of the LT group. Hemodynamic status and oxygen metabolism were monitored and the levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were measured in blood samples obtained at baseline and at 10 minutes, 2 hours and 4 hours after ROSC. At 24 hours after ROSC, the animals were killed and the liver was removed to determine the Na⁺-K⁺-ATPase and Ca²⁺-ATPase enzyme activities and histological changes under a light or electron microscope.

RESULTS:

Core temperature was decreased in the LT group (P<0.05), while HR, MAP and CPP were not significantly decreased (P>0.05) compared with the NT group (P>0.05). The oxygen extraction ratio was lower in the LT group than in the NT group (P<0.05). The serum levels of ALT, AST and LDH increased in both groups but not significantly in the LT group. The enzyme activity of liver ATP was much higher in the LT group (Na⁺-K⁺-ATP enzyme: 8.64±3.32 U vs. 3.28±0.71 U; Ca²⁺-ATP enzyme: 10.92±2.12 U vs. 2.75±0.78 U, P<0.05). The LT group showed less cellular edema, inflammation and few damaged mitochondria as compared with the NT group.

CONCLUSION:

These data suggested that infusing 4 ºC NS continuously after ROSC could quickly lower the core body temperature, while maintaining a stable hemodynamic state and balancing oxygen metabolism, which protect the liver in terms of biochemistry, enzymology and histology after CPR.KEY WORDS: Therapeutic hypothermia, Cardiac arrest, Liver, Hemodynamics     

Comparison of early sequential hypothermia and delayed hypothermia on neurological function after resuscitation in a swine model

Background

We utilized a porcine cardiac arrest model to compare early sequential hypothermia (ESH) with delayed hypothermia (DH) and no hypothermia (NH) to investigate the different effects on cerebral function after resuscitation.

Effects of pentoxifylline on hemodynamics, oxygen transport, and tissue metabolism in experimental, severe hemorrhagic shock

BACKGROUND AND METHODS: It is hypothesized that pentoxifylline may be beneficial during shock states by improving tissue oxygenation. To test this hypothesis, we examined the effect of pentoxifylline on hemodynamics, oxygen delivery (DO2), and tissue metabolism during severe hemorrhagic shock. We conducted a placebo-controlled, randomized trial using anesthetized, mechanically ventilated dogs in hemorrhagic shock maintained at a mean arterial pressure of 45 to 50 mm Hg. Six animals were treated with a 10-mg/kg bolus of iv pentoxifylline followed by a continuous infusion at 5 mg/kg.hr. The controls consisted of six animals treated with saline. RESULTS: There were no significant differences between the groups before treatment. During 150 mins of posttreatment, repeated measurements of the control and pentoxifylline groups showed no significant differences in heart rate (HR), cardiac output, systemic and pulmonary vascular resistances, DO2, or blood lactate concentration (repeated-measures analysis of variance). CONCLUSIONS: In this acute, nonresuscitated, canine hemorrhagic shock model, pentoxifylline did not act as a vasodilator, or have any significant effect on HR, cardiac output, oxygen transport, or lactic acidosis.     

Improved survival of hemorrhagic shock with oxygen and hypothermia in rats.

A previously established model in awake rats of hemorrhagic shock (HS) with 25% spontaneous survival rate (without resuscitation) was used to evaluate the effects of 4 novel life-supporting first aid (LSFA) measures on survival time and rate. After shed blood volume (SBV) of 3.25 ml/100 g, withdrawn over 20 min, hemodynamic and respiratory responses were recorded to 3 h and survival to 24 h. The 5 groups of 20 rats each (total n = 100) were as follows: group I, controls without treatment; II, oxygen 100% inhalation; III, external cooling to rectal temperature 30 degrees C; IV, Ringer's solution 5 ml/100 g rectally; and V, acoustic and surface stimuli for arousal. Survival rates were: control group I, 35% at 3 h and 15% at 24 h; oxygen group II, 75% (P less than 0.05 compared with group I) at 3 h and 60% (P less than 0.05 compared with group I) at 24 h; hypothermia group III, 65% at 3 h and 45% (P less than 0.05 compared with group I) at 24 h; rectal fluid group IV, 50% at 3 h and 40% at 24 h; stimulated group V, 15% at 3 h and 15% at 24 h. Compared with group I, median survival times during HS 0-3 h were longer in groups II and III; and self-resuscitation attempts were longer in groups II, III and IV. We conclude that in untreated severe hemorrhagic shock, chances of survival to delayed arrival of advanced life support with i.v. fluid resuscitation might be increased with O2 inhalation and/or moderate external cooling.     

Effects of arterial oxygen content on oxidative stress during resuscitation in a rat hemorrhagic shock model

Objective

To examine whether reactive oxygen species (ROS) production is affected by arterial oxygen content (CaO₂) in attempted resuscitation to restore blood pressure from hemorrhagic shock (HS) or not.

Methods

Under light anesthesia and spontaneous beating, 16 rats underwent HS for 80 min, during which 3.0 mL/100 g of blood was withdrawn, followed by resuscitation attempt for 70 min. At 80 min, rats were randomized into a high-CaO₂ group (Group 1, transfusion under fractional inspired oxygen (F_IO₂) of 1.0, n = 8) or a low-CaO₂ group (Group 2, fluid administration under F_IO₂ of 0.21, n = 8). In each group, either blood or lactate Ringer's (LR) solution was infused to maintain mean arterial pressure ≥75 mmHg under each F_IO₂ concentration. CaO₂, O₂ utilization coefficient (UC) and plasma %CoQ9 were compared between groups.

Results

Mean infused volume for attempted resuscitation was 7.6 ± 1.0 mL of blood in Group 1, and 31.4 ± 5.5 mL of LR solution in Group 2. At the end of resuscitation, CaO₂ was 18.5 ± 1.2 vol% in Group 1, almost double the 9.1 ± 0.8 vol% in Group 2 (P < 0.01). O₂ UC and %CoQ9 in all rats increased from baselines of 0.25 ± 0.12 and 7.6 ± 1.8% to 0.44 ± 0.13 and 9.7 ± 1.8% after resuscitation, respectively (P < 0.05 vs. baseline for each), but did not differ significantly between the groups.

Conclusion

In a rat HS model, attempted resuscitation to restore blood pressure increased O₂ UC as well as %CoQ9. However, the magnitude of %CoQ9 increase that represents ROS production is not affected by CaO₂ during resuscitation from HS.     

Effects of increased oxygen breathing in a volume controlled hemorrhagic shock outcome model in rats

It is believed that victims of traumatic hemorrhagic shock (HS) benefit from breathing 100% O(2). Supplying bottled O(2) for military and civilian first aid is difficult and expensive. We tested the hypothesis that increased FiO(2) both during severe volume-controlled HS and after resuscitation in rats would: (1) increase blood pressure; (2) mitigate visceral dysoxia and thereby prevent post-shock multiple organ failure; and (3) increase survival time and rate. Thirty rats, under light anesthesia with halothane (0. 5% throughout), with spontaneous breathing of air, underwent blood withdrawal of 3 ml/100 g over 15 min. After HS phase I of 60 min, resuscitation phase II of 180 min with normotensive intravenous fluid resuscitation (shed blood plus lactated Ringer's solution), was followed by an observation phase III to 72 h and necropsy. Rats were randomly divided into three groups of ten rats each: group 1 with FiO(2) 0.21 (air) throughout; group 2 with FiO(2) 0.5; and group 3 with FiO(2) 1.0, from HS 15 min to the end of phase II. Visceral dysoxia was monitored during phases I and II in terms of liver and gut surface PCO(2) increase. The main outcome variables were survival time and rate. PaO(2) values at the end of HS averaged 88 mmHg with FiO(2) 0.21; 217 with FiO(2) 0.5; and 348 with FiO(2) 1. 0 (P<0.001). During HS phase I, FiO(2) 0.5 increased mean arterial pressure (MAP) (NS) and kept arterial lactate lower (P<0.05), compared with FiO(2) 0.21 or 1.0. During phase II, FiO(2) 0.5 and 1. 0 increased MAP compared with FiO(2) 0.21 (P<0.01). Heart rate was transiently slower during phases I and II in oxygen groups 2 and 3, compared with air group 1 (P<0.05). During HS, FiO(2) 0.5 and 1.0 mitigated visceral dysoxia (tissue PCO(2) rise) transiently, compared with FiO(2) 0.21 (P<0.05). Survival time (by life table analysis) was longer after FiO(2) 0.5 than after FiO(2) 0.21 (P<0. 05) or 1.0 (NS), without a significant difference between FiO(2) 0. 21 and 1.0. Survival rate to 72 h was achieved by two of ten rats in FiO(2) 0.21 group 1, by four of ten rats in FiO(2) 0.5 group 2 (NS); and by four of ten rats of FiO(2) 1.0 group 3 (NS). In late deaths macroscopic necroses of the small intestine were less frequent in FiO(2) 0.5 group 2. We conclude that in rats, in the absence of hypoxemia, increasing FiO(2) from 0.21 to 0.5 or 1.0 does not increase the chance to achieve long-term survival. Breathing FiO(2) 0.5, however, might increase survival time in untreated HS, as it can mitigate hypotension, lactacidemia and visceral dysoxia.     

Effects of verapamil and nitroglycerin on coronary and systemic hemodynamics in conscious dogs

Effects of i.v. bolus administration of verapamil (10-300 micrograms/kg) and nitroglycerin (0.01-30 micrograms/kg) on coronary and systemic hemodynamics were studied in chronically instrumented conscious dogs. Verapamil in a dose of 10 micrograms/kg dilated the large epicardial coronary artery, increased the coronary blood flow and heart rate and decreased the aortic pressure. A reduction of left ventricular dP/dt was observed when over 30 micrograms/kg of verapamil was administered. Nitroglycerin in a dose of 0.01 micrograms/kg dilated the large epicardial coronary artery. Other variables such as coronary blood flow, aortic pressure and heart rate were influenced when over 0.1 micrograms/kg of nitroglycerin was given. The effects of these drugs on coronary and systemic hemodynamics were augmented when incremental doses were given. Duration of the increases in coronary diameter and coronary blood flow persisted longer after verapamil than after nitroglycerin. To estimate the changes in coronary diameter, independent of flow change, the effects of verapamil (100 micrograms/kg) and nitroglycerin (20 micrograms/kg) on the large epicardial coronary artery were reexamined when the coronary blood flow was maintained constant using a cuff occluder. The extent of coronary artery dilation, unaffected by coronary blood flow, was 62% with verapamil and 100% with nitroglycerin. Thus, although nitroglycerin preferentially and flow-independently dilates the large epicardial coronary artery, dilation of the large epicardial coronary artery after verapamil is augmented by the process of flow-induced arterial relaxation.     

Molecular mechanisms of therapeutic hypothermia on neurological function in a swine model of cardiopulmonary resuscitation

Objective

To explore the molecular mechanisms by which mild hypothermia following resuscitation improves neurological function in a porcine model of cardiac arrest.

Methods

Thirty-three inbred Chinese Wuzhishan (WZS) minipigs were used. After 8 min of untreated ventricular fibrillation (VF), the surviving animals (n = 29) were randomly divided into two groups including serum group (n = 16) and molecular group (n = 13). Serum group animals were used to measure porcine-specific tumour necrosis factor-alpha (TNF-α), interleukin (IL-6, IL-10), matrix metalloproteinase (MMP9), Aquaporin-4 (AQP4), tissue inhibitor to metalloproteinase-1 (TIMP1), neuron-specific enolase (NSE) and S100B at 0.5 h, 6 h, 12 h, 24 h and 72 h recovery by enzyme-linked immunosorbent assay (ELISA). Molecular group animals were used to measure cerebral cortex messenger RNA (mRNA) and protein expression of nuclear factor-κB (NF-κB), MMP9 and AQP4 by real-time (RT) quantitative polymerase chain reaction (PCR) and Western blotting at 24 h and 72 h recovery. Animals were further divided into either normothermia or hypothermia groups. Hypothermia (33 °C) was maintained for 12 h using an endovascular cooling device. Swine neurologic deficit scores (NDS) were used to evaluate neurological function at 24-h and 72-h recovery.

Results

Twenty-nine of the 33 (87.9%) animals were successfully resuscitated. The hypothermia group exhibited higher survival rates at 24 h (75%) and 72 h (62.5%) compared to the normothermia group (37.5% and 25%, respectively). Hypothermia markedly inhibited expression of NF-κB, TNF-α, MMP9 and NSE, and promoted expression of TIMP1 (P < 0.01). The mean NDS at 24-h and 72-h recovery was 112.5 and 61, respectively, in the hypothermic group, and 230 and 207.5, respectively, in the normothermia group.

Conclusion

Brain protection induced by hypothermia involves inhibition of inflammatory and brain edema pathways.     

低温复苏对大鼠失血性休克肝损伤的影响

目的探讨低温复苏对大鼠失血性休克肝损伤的保护作用及其机制。方法 24只成年雄性Wistar大鼠随机平均分为3组,对照组(S)、常温复苏组(N)(37~38℃)和低温复苏组(H)(33~34℃)。S组只进行外科插管操作,不建立失血性休克模型及复苏,N组和H组在建立失血性休克模型后分别在预定温度下进行复苏。Real-time PCR法检测复苏240 min肝组织PPAR-γ、HSP70和TNF-αm RNA表达变化。ELISA法检测血清TNF-α浓度变化。生化法检测血清ALT和AST浓度变化。结果 (1)休克复苏240 min大鼠血清TNF-α浓度为S组(8.53±1.90)ng/ml,N组(74.08±8.81)ng/ml,H组(32.13±5.82)ng/ml,两个实验组差异具有统计学意义(P<0.05);(2)休克复苏240 min大鼠血清ALT和AST浓度分别为是S组(61±11)U/L、(47±9)U/L,N组(187±20)U/L、(139±15)U/L,H组(141±11)U/L、(97±11)U/L,两个实验组差异有统计学意义(P<0.05);(3)与S组比较,休克复苏240 min N组肝组织PPAR-γm RNA表达量为0.50±0.11,H组PPAR-γm RNA表达量为2.01±0.48(P<0.05);(4)与S组比较,休克复苏240 min N组肝组织HSP70 m RNA表达量为4.12±1.36,H组HSP70 m RNA表达量为11.69±3.88(P<0.05);(5)与S组比较,休克复苏后240 min N组肝组织TNF-αm RNA表达量为15.10±4.99,H组TNF-αm RNA表达量为10.10±2.95(P<0.05)。结论失血性休克后的低温复苏能够上调大鼠肝组织内PPAR-γ和HSP70基因的表达,同时抑制TNF-α基因表达,降低血清中TNF-α、ALT和AST的浓度,减轻肝脏损伤,利于休克的复苏。     

HBOC-201 improves survival in a swine model of hemorrhagic shock and liver injury

BACKGROUND: Blunt abdominal trauma that leads to hemorrhagic shock and cardiac arrest is almost always fatal in the prehospital setting. The current study investigated whether a hemoglobin-based oxygen carrier (HBOC-201) could maintain organ viability during an exsanguinating liver injury and allow for prolonged survival. This hypothesis was tested in a large animal model that simulated blunt abdominal trauma with major organ injury. METHODS: Swine underwent a liver crush, laceration and 50 ml/kg initial blood loss. The liver bled at 3 ml/kg per min during the resuscitation phase. No fluid (NF=6), hetastarch (HES=8), or HBOC-201 (HBOC=8) was given during the resuscitation phase. Swine alive 60 min after the initial injury underwent liver repair and 96 h observation. RESULTS: All HBOC swine survived 60 min versus none of the NF or HES swine (P<0.05). All HBOC swine survived 24 h and 7/8 survived 96 h with good functional recovery. CONCLUSIONS: HBOC resuscitation during liver bleeding in a swine model of hemorrhagic shock and liver injury allowed for 96 h survival. No fluid or HES in the same model was fatal.     

Effect of different resuscitation strategies on neutrophil activation in a swine model of hemorrhagic shock

Activated neutrophils play a pivotal role in resuscitation injury. The strategies used for resuscitation (types of fluids and methods of administration) can affect the degree of neutrophil activation. The aim of this study was to test the commonly available resuscitation fluids in a large animal model of hemorrhagic shock to determine the strategy associated with the least degree of neutrophil activation. Methods: Female swine (n=63, weight 45-60 kg) were anesthetized using isoflurane and catheters were placed for hemodynamic monitoring. After 120 min, they were subjected to a volume controlled hemorrhage (28 ml/kg) over 15 min, kept in shock for 60 min, and then resuscitated. The resuscitation groups were as follows: (1) anesthesia only (n=5); (2) hemorrhage, sham resuscitation (n=5); (3) LR-fast rate 3x blood loss (n=6); (4) LR slow rate-3x blood loss (n=6); (5) LR low volume-1x blood loss (n=6); (6) Dextran 40-1x blood loss (n=6); (7) 6% hetastarch-1x blood loss (n=6); (8) 5% albumin-1x blood loss (n=6); (9) 25% albumin-1/5x blood loss (n=6); (10) whole blood resuscitation-1x blood loss (n=6); (11) 7.5% hypertonic saline (HTS)-0.3x blood loss (n=5). Resuscitation fluids were infused over 1 h in all groups except group 4 (LR slow rate, which was over 3 h). Animals were observed for 180 min following the resuscitation period. Neutrophil oxidative burst activity was determined in whole blood using flow cytometery. Results: Animals resuscitated with dextran and hetastarch showed significantly (P<0.05) higher neutrophil burst activity. Resuscitation with LR also caused neutrophil activation (P<0.05), and the highest degree of activation was seen when a large volume of LR was given at a fast rate (group 8). However, all LR infusion protocols were associated with significant neutrophil activation compared with anesthesia (group 1) or sham resuscitation (group 2). No significant activation was seen in the animals resuscitated with albumin or fresh whole blood. Conclusion: Artificial colloids and LR (independent of rate or volume of infusion) caused significant neutrophil activation, which was not seen with albumin and whole blood resuscitation. These findings suggest that the type of resuscitation fluid and method of infusion can influence neutrophil function.     

A continuous hemorrhage model of fatal hemorrhagic shock in swine

We studied the effect of bleed rate on survival time and hemodynamics in a continuous hemorrhage model of fatal hemorrhagic shock in lightly anesthetized swine. Fasted immature swine (12-16 kg) were sedated with intramuscular (i.m.) ketamine, endotracheally intubated, anesthetized with halothane (0.75%), nitrous oxide, and oxygen, and then prepared for experimentation by placement of a pulmonary artery thermodilution catheter, femoral arterial and venous catheters, and by splenectomy. After instrumentation, halothane was discontinued and sedation was maintained with nitrous oxide and intravenous lorazepam. Thirty minutes later, the animals were bled continuously at 1.0 ml/kg per min (n = 8, Group I) or 1.25 ml/kg per min (n = 8, Group II) by a roller pump connected to the femoral arterial catheter. Hemodynamic parameters were recorded every 15 min until death occurred. Mean survival time was 50.2 +/- 3.0 min in Group I and 39.8 +/- 3.2 min in Group II (P less than 0.001). There was a stepwise decrease in blood pressure and cardiac index consistent with progressive hemorrhagic shock. This model results in reproducible survival times with small standard deviations. Although the animals are lightly anesthetized and the experiments are performed acutely, the hemodynamic responses and survival times observed are similar to those reported in previous studies of chronically instrumented, unanesthetized swine. This model may be more practical than unanesthetized, chronically instrumented swine models for evaluating the effects of various interventions on survival time and hemodynamics in acute hemorrhagic shock.     

Effects of mild hypothermia on survival and serum cytokines in uncontrolled hemorrhagic shock in rats

Previous studies have suggested benefit of mild hypothermia during hemorrhagic shock (HS). This finding needs additional confirmation and investigation into possible mechanisms. Proinflammatory cytokines are mediators of multiple organ failure following traumatic hemorrhagic shock and resuscitation. We hypothesized that mild hypothermia would improve survival from HS and may affect the pro- and anti-inflammatory cytokine response in a rat model of uncontrolled HS. Under light halothane anesthesia, uncontrolled HS was induced by blood withdrawal of 3 mL/100 g over 15 min followed by tail amputation. Hypotensive (limited) fluid resuscitation (to prevent mean arterial pressure [MAP] from decreasing below 40 mmHg) with blood was started at 30 min and continued to 90 min. After hemostasis and resuscitation with initially shed blood and Ringer's solution, the rats were observed for 72 h. The animals were randomized into two HS groups (n = 10 each): normothermia (38 degrees C +/- 0.5 degrees C) and mild hypothermia (34 degrees C +/- 0.5 degrees C) from HS 30 min until resuscitation time (RT) 60 min; and a sham group (n = 3). Venous blood samples were taken at baseline, RT 60 min, and days 1, 2, and 3. Serum interleukin (IL)-1beta, IL-6, IL-10, and tumor necrosis factor (TNF)-alpha concentrations were quantified by ELISA. Values are expressed as median and interquartile range. Survival time by life table analysis was greater in the hypothermia group (P = 0.04). Survival rates to 72 h were 1 of 10 vs. 6 of 10 in the normothermia vs. hypothermia groups, respectively (P = 0.057). All cytokine concentrations were significantly increased from baseline at RT 60 min in both HS groups, but not in the shams. At RT 60 min, in the normothermia vs. hypothermia groups, respectively, IL-1beta levels were 185 (119-252) vs. 96 (57-135) pg/mL (P = 0.15); IL-6 levels were 2242 (1903-3777) vs. 1746 (585-2480) pg/mL (P = 0.20); TNF-alpha levels were 97 (81-156) vs. 394 (280-406) pg/mL (P= 0.02); and IL-10 levels were 1.7 (0-13.3) vs. 15.8 (1.9-23.0) pg/mL (P = 0.09). IL-10 remained increased until day 3 in the hypothermia group. High IL-1beta levels (>100 pg/mL) at RT 60 min were associated with death before 72 h (odds ratio 66, C.I. 3.5-1255). We conclude that mild hypothermia improves survival time after uncontrolled HS. Uncontrolled HS induces a robust proinflammatory cytokine response. The unexpected increase in TNF-alpha with hypothermia deserves further investigation.     

Effects of bovine polymerized hemoglobin on coagulation in controlled hemorrhagic shock in swine

HBOC-201, a bovine polymerized hemoglobin, has been proposed as a novel oxygen-carrying resuscitative fluid for patients with hemorrhagic shock (HS). Herein, we evaluated the hemostatic effects of HBOC-201 in an animal model of HS. A 40% blood loss-controlled hemorrhage and soft tissue injury were performed in 24 invasively monitored Yucatan mini-pigs. Pigs were resuscitated with HBOC-201 (HBOC) or hydroxyethyl starch (HEX), or were not resuscitated (NON) based on cardiac parameters during a 4-h prehospital phase. Afterward, animals received simulated hospital care for 3 days with blood or saline transfusions. Hemostasis measurements included in vivo bleeding time (BT), thromboelastography (TEG), in vitro bleeding time (platelet function; PFA-CT), prothrombin time (PT), and partial thromboplastin time (PTT). Serum lactate was measured and lung sections were evaluated for microthrombi by electron microscopy. During the prehospital phase, BT remained unchanged in the HBOC group. TEG reaction time increased in HBOC pigs during the late prehospital phase and was greater than in NON or HEX pigs at 24 h (P = 0.03). TEG maximum amplitude was similar for the two fluid-resuscitated groups. PFA-CT increased in both resuscitated groups but less with HBOC (P = 0.02) in the prehospital phase; this effect was reversed by 24 h (P = 0.02). In the hospital phase, PT decreased (P < 0.02), whereas PTT increased above baseline (P < 0.01). Lactic acidosis in HBOC and HEX groups was similar. Aspartate aminotransferase was relatively elevated in the HBOC group at 24 h. Electron microscopy showed no evidence of platelet/fibrin clots or microthrombi in any of the animals. Twenty-four-hour group differences mainly reflected the fact that all HEX animals (8/8) received blood transfusions compared with only one HBOC animal (1/8). In swine with HS, HBOC resuscitation induced less thrombopathy than HEX during the prehospital phase. Mild delayed effects on platelet and clot formation during the hospital phase are transient and likely related to fewer blood transfusions. In swine with HS, HBOC resuscitation induced less thrombopathy than HEX during the prehospital phase but more thrombopathy in the hospital phase. The delayed effects on platelet and clot formation during the hospital phase are transient and may be related to the need for fewer blood transfusions.     

亚低温对猪脓毒性休克时心肌的影响

目的 探讨亚低温对猪脓毒性休克时心肌的保护作用.方法 24头贵州小型猪随机(随机数字法)分为休克前亚低温组、休克后亚低温组和常温对照组,每组8头.麻醉后股静脉注入大肠杆菌内毒素制作猪脓毒症模型.制模后各组同时用输液泵以相同速度股静脉持续输入生理盐水,休克前亚低温组用4℃的生理盐水,常温对照组和休克后亚低温组用38℃的生理盐水,休克后亚低温组在动脉收缩压降至基础值的60%,维持1 h后,开始改用4℃的生理盐水.制模前和制模后温度干预6 h、12h时观察各组心脏血流动力学指标、血乳酸、肌钙蛋白I(CTnI)、冠状动脉造影TIMI血流、电镜下心肌超微结构变化.结果 6 h,12 h后,休克前亚低温组各项指标均显著优于休克后亚低温组和常温对照组(P<0.01).6 h后,休克后亚低温组的CTnI、超微结构损伤变化轻于常温对照组(P<0.05),但两组血乳酸、TIMI血流、血流动力学指标变化差异无统计学意义(P>0.05).12 h后,休克后亚低温组各项指标和常温对照组差异无统计学意义(P>0.05).结论 亚低温对猪脓毒症时的心肌有一定的保护作用;猪脓毒性休克发生以前早期使用亚低温对心肌的保护作用和改善心功能较明显;猪脓毒性休克发生以后,亚低温可以延缓心肌损伤的速度,但并不减轻心肌损伤的程度,也不能减少心功能的丧失.     

Effects of mild hypothermia on hemodynamics in cardiac arrest survivors and isolated failing human myocardium

Post-cardiac arrest myocardial dysfunction is a common phenomenon after return of spontaneous circulation (ROSC) and contributes to hemodynamic instability and low survival rates after cardiac arrest. Mild hypothermia for 24 h after ROSC has been shown to significantly improve neurologic recovery and survival rates. In the present study we investigate the influence of therapeutic hypothermia on hemodynamic parameters in resuscitated patients and on contractility in failing human myocardium. We analyzed hemodynamic data from 200 cardiac arrest survivors during the hypothermia period. The initial LVEF was 32.6 ± 1.2% indicating a significantly impaired LV function. During hypothermia induction, the infusion rate of epinephrine could be significantly reduced from 9.1 ± 1.3 μg/min [arrival intensive care unit (ICU) 35.4°C] to 4.6 ± 1.0 μg/min (34°C) and 2.8 ± 0.5 μg/min (33°C). The dobutamine and norepinephrine application rates were not changed significantly. The mean arterial blood pressure remained stable. The mean heart rate significantly decreased from 91.8 ± 1.7 bpm (arrival ICU) to 77.3 ± 1.5 bpm (34°C) and 70.3 ± 1.4 bpm (33°C). In vitro we investigated the effect of hypothermia on isolated ventricular muscle strips from explanted failing human hearts. With decreasing temperature, the contractility increased to a maximum of 168 ± 23% at 27°C (n = 16, P < 0.05). Positive inotropic response to hypothermia was accompanied by moderately increased rapid cooling contractures as a measure of sarcoplasmic reticulum (SR) Ca²⁺ content, but can be elicited even when the SR Ca²⁺ release is blocked in the presence of ryanodine. Contraction and relaxation kinetics are prolonged with hypothermia, indicating increased Ca²⁺ sensitivity as the main mechanism responsible for inotropy. In conclusion, mild hypothermia stabilizes hemodynamics in cardiac arrest survivors which might contribute to improved survival rates in these patients. Mechanistically, we demonstrate that hypothermia improves contractility in failing human myocardium most likely by increasing Ca²⁺-sensitivity.