Shock : molecular, cellular, and systemic pathobiological aspects and therapeutic approaches : the official journal the Shock Society, the European Shock Society, the Brazilian Shock Society, the International Federation of Shock Societies
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Early detection and management of shock are important in optimizing clinical outcomes. One regional marker, sublingual capnography (SLCO2), is particularly appealing as redistribution of blood flow away from the sublingual mucosa can happen very early in the compensatory phase of hypovolemic shock. Our objective was to test the hypothesis that SLCO2 would detect early hypovolemia in a human laboratory model of hemorrhage: progressive lower body negative pressure until onset of cardiovascular collapse. ⋯ Average time to presyncope was 1,579 ± 72 s (mean ± SE). At the time of cardiovascular collapse, lower body negative pressure altered (P < 0.001) systolic blood pressure (mean ± SE: 130 ± 3 vs. 98 ± 2 mm Hg), pulse pressure (mean ± SE: 58 ± 2 vs. 33 ± 2 mm Hg), and heart rate (mean ± SE: 63 ± 3 vs. 102 ± 6 beats/min) when compared with baseline, whereas SLCO2 did not change (49.1 ± 1.0 vs. 48.6 ± 1.5 mm Hg, P = 0.624). In a model of progressive central hypovolemia in humans, we did not detect metabolic derangements in the sublingual mucosa as measured by SLCO2.
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The role and source of tumor necrosis factor-α in hemorrhage-induced priming for septic lung injury.
Tumor necrosis factor α (TNF-α) has been reported to be a key component of the functional priming, of both myeloid and nonmyeloid cells, that is thought to contribute to the lung's increased susceptibility to injury following shock. Not surprisingly, we found that mice deficient in TNF-α exhibited reduced acute lung injury (ALI) resultant from the combined insults of hemorrhagic shock and sepsis. However, we found that when we adoptively transferred neutrophils from mice expressing TNF-α to neutrophil-depleted mice that lacked TNF-α, they were not able to serve as priming stimulus for the development of ALI. ⋯ We hypothesized that alternately suppressing expression of TNF-α in lung endothelial (i.v.) or epithelial (i.t.) cells would produce a differential effect in shock-induced ALI. We found that when in vivo siRNA i.t. or i.v. against TNF-α was administered to C57/BL6 mice at 2 h after hemorrhage, 24 h before septic challenge, that systemic/i.v., but not i.t., delivery of TNF-α siRNA following hemorrhage priming significantly reduces expression of indices of ALI compared with controls. These findings suggest that an absence of local lung tissue TNF-α significantly reduces lung tissue injury following hemorrhage priming for ALI and that pulmonary endothelial and/or other possible vascular resident cells, not epithelial cells, play a greater role in mediating the TNF-α priming response in a mouse model of hemorrhage/sepsis-induced ALI.
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The management of severe traumatic brain injury (TBI) focuses on prevention and treatment of intracranial hypertension (ICH) and cerebral hypoperfusion (CH). Predicting which patients will develop these secondary insults is currently not possible. This study investigates the systemic manifestation of neuroinflammation and its role in helping to predict clinical deterioration following severe TBI. ⋯ Interleukin 8 and TNF-α demonstrate promise as candidate serum markers of impending ICH and CH. This suggests that we may be able to "predict" imminent events following TBI before clinical manifestations. Given the morbidity of ICH and CH, minimizing the effects of these secondary insults may have a significant impact on outcome and help guide decisions about timing of interventions.
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Elderly humans are more vulnerable to trauma and hemorrhage than young and elderly men and respond with decreased defense of central blood volume during acute experimental hypovolemia induced by lower body negative pressure (LBNP). However, these defense mechanisms have not been evaluated in elderly women. The aim of this study was to determine the effectiveness of compensatory responses to defend central blood volume during experimental hypovolemia in elderly and young women. ⋯ Mobilization of capacitance blood from the peripheral circulation was both slower and decreased by ∼60% in elderly women (P < 0.001), and net capillary fluid absorption from surrounding tissues was reduced by ∼40% (P < 0.01, LBNP of 44 mmHg). Elderly women responded with less increase in heart rate but with equal forearm vascular resistance (%) response during LBNP. Furthermore, the compensatory capacitance response was both slower and substantially decreased, and net capillary fluid absorption considerably reduced, collectively indicating less efficiency to defend central blood volume in elderly than in young women.
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This study's objective was to investigate the daily dynamics of fibrinogen metabolism and coagulation function for 5 days after hemorrhagic shock in pigs. Sixteen pigs were randomized into the control (C) and the hemorrhage (H) groups. On day 1, hemorrhage was induced in H by bleeding 35% of the estimated total blood volume, followed by resuscitation with lactated Ringer's solution at three times the bled volume. ⋯ Compared with day 1 control value (1.3 ± 0.1 mg/kg per hour), fibrinogen synthesis in H was increased to 3.6 ± 0.1, 5.1 ± 0.5, 2.6 ± 0.4, 2.7 ± 0.5, and 2.3 ± 0.3 mg/kg per hour on days 1 through 5 (all P < 0.05); fibrinogen breakdown in H was elevated on days 1 and 2 but returned to control values afterward. Hemorrhage caused acute decreases in fibrinogen concentration and clot strength, followed by an increase in fibrinogen concentration and recovery of clot strength. The increase in fibrinogen appeared primarily due to a sustained increase in fibrinogen synthesis.