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To determine the effects of mild blast-induced traumatic brain injury (bTBI), several groups of rats were subjected to blast injury or sham injury in a compressed air-driven shock tube. The effects of bTBI on relative cerebral perfusion (laser Doppler flowmetry [LDF]), and mean arterial blood pressure (MAP) cerebral vascular resistance were measured for 2 h post-bTBI. Dilator responses to reduced intravascular pressure were measured in isolated middle cerebral arterial (MCA) segments, ex vivo, 30 and 60 min post-bTBI. Neuronal injury was assessed (Fluoro-Jade C [FJC]) 24 and 48 h post-bTBI. Neurological outcomes (beam balance and walking tests) and working memory (Morris water maze [MWM]) were assessed 2 weeks post-bTBI. Because impact TBI (i.e., non-blast TBI) is often associated with reduced cerebral perfusion and impaired cerebrovascular function in part because of the generation of reactive oxygen and nitrogen species such as peroxynitrite (ONOO−), the effects of the administration of the ONOO− scavenger, penicillamine methyl ester (PenME), on cerebral perfusion and cerebral vascular resistance were measured for 2 h post-bTBI. Mild bTBI resulted in reduced relative cerebral perfusion and MCA dilator responses to reduced intravascular pressure, increases in cerebral vascular resistance and in the numbers of FJC-positive cells in the brain, and significantly impaired working memory. PenME administration resulted in significant reductions in cerebral vascular resistance and a trend toward increased cerebral perfusion, suggesting that ONOO− may contribute to blast-induced cerebral vascular dysfunction.

Vascular hypo-responsiveness to vasopressors during septic shock is a challenging problem. This study is to test the hypothesis that reactive nitrogen species (RNS), such as peroxynitrite, are major contributing factors to vascular hypo-responsiveness in septic shock. We hypothesized that adjunct therapy with peroxynitrite decomposition catalyst (PDC) would reduce norepinephrine requirements in sepsis resuscitation. Fourteen female Merino sheep were subjected to a “two-hit” injury (smoke inhalation and endobronchial instillation of live methicillin-resistant Staphylococcus aureus [1.6–2.5 × 1011 CFUs]). The animals were randomly allocated to control: injured, fluid resuscitated, and titrated norepinephrine, n = 7; or PDC: injured, fluid resuscitated, titrated norepinephrine, and treated with PDC, n = 7. One-hour postinjury, an intravenous injection of PDC (0.1 mg/kg) was followed by a continuous infusion (0.04 mg/kg/h). Titration of norepinephrine started at 0.05 mcg/kg/min based on their mean arterial pressure. All animals were mechanically ventilated and monitored in the conscious state for 24 h. The mean arterial pressure was well maintained in the PDC with significantly less norepinephrine requirement from 7 to 23 h after injury compared with control. Total norepinephrine dose, the highest norepinephrine rate, and time on norepinephrine support were also significantly lower in PDC. Modified sheep organ failure assessment scores at 6 to 18 h postinjury were significantly lower in PDC compared with control. PDC improved survival rate at 24 h (71.4% vs. 28.6%). PDC treatment had no adverse effects. In conclusion, the modulation of RNS may be considered an effective adjunct therapy for septic shock, in the case of hypo-responsiveness to norepinephrine.

Background Sepsis is one of the most frequent causes of death in the intensive care unit. Host vascular hypo-responsiveness to vasopressors during septic shock is one of the challenging problems. This study tested the hypothesis that adjunct therapy with peroxynitrite decomposition catalyst (WW-85) would reduce arginine vasopressin (AVP) requirements during sepsis resuscitation, using ovine sepsis model. Methods Thirteen adult female Merino sheep, previously instrumented with multiple vascular catheters, were subjected to “two-hit” (cotton smoke inhalation and intrapulmonary instillation of live methicillin-resistant Staphylococcus aureus; 3.5 × 1011 colony-forming units) injury. Post injury, animals were awakened and randomly allocated to the following groups: (1) AVP: injured, fluid resuscitated, and titrated with AVP, n = 6 or (2) WW-85 + AVP: injured, fluid resuscitated, treated with WW-85, and titrated with AVP, n = 7. One-hour post injury, a bolus intravenous injection of WW-85 (0.1 mg/kg) was followed by a 23-h continuous infusion (0.02 mg/kg/h). Titration of AVP started at a dose of 0.01 unit/min, when mean arterial pressure (MAP) decreased by 10 mmHg from baseline, despite aggressive fluid resuscitation, and the rate was further adjusted to maintain MAP. After the injury, all animals were placed on a mechanical ventilator and monitored in the conscious state for 24 h. Results The injury induced severe hypotension refractory to aggressive fluid resuscitation. High doses of AVP were required to partially attenuate the sepsis-induced hypotension. However, the cumulative AVP requirement was significantly reduced by adjunct treatment with WW-85 at 17–24 h after the injury (p < 0.05). Total AVP dose and the highest AVP rate were significantly lower in the WW-85 + AVP group compared to the AVP group (p = 0.02 and 0.04, respectively). Treatment with WW-85 had no adverse effects. In addition, the in vitro effects of AVP on isolated artery diameter changes were abolished with peroxynitrite co-incubation. Conclusions The modulation of reactive nitrogen species, such as peroxynitrite, may be considered as a novel adjunct treatment option for septic shock associated with vascular hypo-responsiveness to vasopressors.