Effect of inhaled nitric oxide on oxygen therapy, mechanical ventilation, and hypoxic respiratory failure.

To assess the role of inhaled nitric oxide (iNO) in reducing the need for oxygen therapy, decreasing time on mechanical ventilatory support, and attenuating probability of hypoxic respiratory failure severity progression, we reviewed published reports of phase III iNO studies in neonates with hypoxic respiratory failure and pulmonary hypertension, as well as a novel post-hoc analysis of data from the Clinical Inhaled Nitric Oxide Research Group Initiative (CINRGI) study population not been previously reported. The post-hoc analysis of the CINRGI study showed that iNO shortens the duration of oxygen therapy versus placebo (17 vs. 34 days; P<0.05); the CINRGI retrospective analysis by Konduri et al. showed earlier administration of iNO (oxygenation index [OI] 15-25) yielded a 48% relative reduction vs. placebo in number of patients who progressed to OI≥30 (16.7% vs. 32.2%; P=0.002). Golombek and Young's pooled analysis of phase III studies showed a rapid improvement in oxygenation after initiation of iNO therapy versus controls in each study, and a significant reduction in median ventilation duration (11 vs. 14 days; P=0.003). A study by Gonzalez et al. revealed that earlier iNO administration in infants with mild to moderate hypoxic respiratory failure (OI 10-30) resulted in a decreased duration of oxygen therapy versus placebo (11.5 vs. 18.0 days; P<0.03) and reduced the probability of developing severe hypoxic respiratory failure.

Pharmacokinetics of Oral and Intravenous Paracetamol (Acetaminophen) When Co-Administered with Intravenous Morphine in Healthy Adult Subjects.

BACKGROUND AND OBJECTIVE: Several features favor paracetamol (acetaminophen) administration by the intravenous rather than the oral route in the postoperative setting. This study compared the pharmacokinetics and bioavailability of oral and intravenous paracetamol when given with or without an opioid, morphine. METHODS: In this randomized, single-blind, parallel, repeat-dose study in healthy adults, subjects received four repeat doses of oral or intravenous 1000 mg paracetamol at 6-h intervals, and morphine infusions (0.125 mg/kg) at the 2nd and 3rd intervals. Comparisons of plasma pharmacokinetic profiles were conducted before, during, and after opioid co-administrations. RESULTS: Twenty-two subjects were included in the pharmacokinetic analysis. Observed paracetamol peak concentration (C max) and area under the plasma concentration-time curve over the dosing interval (AUC0-6) were reduced when oral paracetamol was co-administered with morphine (reduced from 11.6 to 7.25 µg/mL and from 31.00 to 25.51 µg·h/mL, respectively), followed by an abruptly increased C max and AUC0-6 upon discontinuation of morphine (to 13.5 µg/mL and 52.38 µg·h/mL, respectively). There was also a significantly prolonged mean time to peak plasma concentration (T max) after the 4th dose of oral paracetamol (2.84 h) compared to the 1st dose (1.48 h). However, pharmacokinetic parameters of paracetamol were not impacted when intravenous paracetamol was co-administered with morphine. CONCLUSIONS: Morphine co-administration significantly impacted the pharmacokinetics of oral but not intravenous paracetamol. The abrupt release of accumulated paracetamol at the end of morphine-mediated gastrointestinal inhibition following oral but not intravenous administration of paracetamol suggests that intravenous paracetamol provides a better option for the management of postoperative pain. CLINICALTRIALS. GOV IDENTIFIER: NCT02848729.

Ropivacaine and Bupivacaine prevent increased pain sensitivity without altering neuroimmune activation following repeated social defeat stress.

OBJECTIVE: Mounting evidence indicates that stress influences the experience of pain. Exposure to psychosocial stress disrupts bi-directional communication pathways between the central nervous system and peripheral immune system, and can exacerbate the frequency and severity of pain experienced by stressed subjects. Repeated social defeat (RSD) is a murine model of psychosocial stress that recapitulates the immune and behavioral responses to stress observed in humans, including activation of stress-reactive neurocircuitry and increased pro-inflammatory cytokine production. It is unclear, however, how these stress-induced neuroimmune responses contribute to increased pain sensitivity in mice exposed to RSD. Here we used a technique of regional analgesia with local anesthetics in mice to block the development of mechanical allodynia during RSD. We next investigated the degree to which pain blockade altered stress-induced neuroimmune activation and depressive-like behavior. METHODS: Following development of a mouse model of regional analgesia with discrete sensory blockade over the dorsal-caudal aspect of the spine, C57BL/6 mice were divided into experimental groups and treated with Ropivacaine (0.08%), Liposomal Bupivacaine (0.08%), or Vehicle (0.9% NaCl) prior to exposure to stress. This specific region was selected for analgesia because it is the most frequent location for aggression-associated pain due to biting during RSD. Mechanical allodynia was assessed 12 h after the first, third, and sixth day of RSD after resolution of the sensory blockade. In a separate experiment, social avoidance behavior was determined after the sixth day of RSD. Blood, bone marrow, brain, and spinal cord were collected for immunological analyses after the last day of RSD in both experiments following behavioral assessments. RESULTS: RSD increased mechanical allodynia in an exposure-dependent manner that persisted for at least one week following cessation of the stressor. Mice treated with either Ropivacaine or Liposomal Bupivacaine did not develop mechanical allodynia following exposure to stress, but did develop social avoidance behavior. Neither drug affected stress-induced activation of monocytes in the bone marrow, blood, or brain. Neuroinflammatory responses developed in all treatment groups, as evidenced by elevated IL-1ß mRNA levels in the brain and spinal cord after RSD. CONCLUSIONS: In this study, psychosocial stress was associated with increased pain sensitivity in mice. Development of mechanical allodynia with RSD was blocked by regional analgesia with local anesthetics, Ropivacaine or Liposomal Bupivacaine. Despite blocking mechanical allodynia, these anesthetic interventions did not prevent neuroimmune activation or social avoidance associated with RSD. These data suggest that stress-induced neuroinflammatory changes are not associated with increased sensitivity to pain following RSD. Thus, blocking peripheral nociception was effective in inhibiting enhanced pain signaling without altering stress-induced immune or behavioral responses.

Sympathetic Release of Splenic Monocytes Promotes Recurring Anxiety Following Repeated Social Defeat.

BACKGROUND: Neuroinflammatory signaling may contribute to the pathophysiology of chronic anxiety disorders. Previous work showed that repeated social defeat (RSD) in mice promoted stress-sensitization that was characterized by the recurrence of anxiety following subthreshold stress 24 days after RSD. Furthermore, splenectomy following RSD prevented the recurrence of anxiety in stress-sensitized mice. We hypothesize that the spleen of RSD-exposed mice became a reservoir of primed monocytes that were released following neuroendocrine activation by subthreshold stress. METHODS: Mice were subjected to subthreshold stress (i.e., single cycle of social defeat) 24 days after RSD, and immune and behavioral measures were taken. RESULTS: Subthreshold stress 24 days after RSD re-established anxiety-like behavior that was associated with egress of Ly6C(hi) monocytes from the spleen. Moreover, splenectomy before RSD blocked monocyte trafficking to the brain and prevented anxiety-like behavior following subthreshold stress. Splenectomy, however, had no effect on monocyte accumulation or anxiety when determined 14 hours after RSD. In addition, splenocytes cultured 24 days after RSD exhibited a primed inflammatory phenotype. Peripheral sympathetic inhibition before subthreshold stress blocked monocyte trafficking from the spleen to the brain and prevented the re-establishment of anxiety in RSD-sensitized mice. Last, ß-adrenergic antagonism also prevented splenic monocyte egress after acute stress. CONCLUSIONS: The spleen served as a unique reservoir of primed monocytes that were readily released following sympathetic activation by subthreshold stress that promoted the re-establishment of anxiety. Collectively, the long-term storage of primed monocytes in the spleen may have a profound influence on recurring anxiety disorders.

Stress and social isolation increase vulnerability to stroke.

Stress is a universal experience for living organisms. Under many circumstances activation of the hypothalamic-pituitary adrenal (HPA) axis is an adaptive response to stress. However, when stress or HPA activation is prolonged or its timing immediately precedes or coincides with an ongoing neurodegenerative process, the results can be deleterious. A causal relationship among stress, HPA axis activity, and stroke outcome exists. Stress is one of many potential triggers of ischemic stroke and sustained elevations in glucocorticoids compromise neuronal survival following an ischemic attack. Indeed, glucocorticoid exposure is a critical determinant of stroke outcome; prior exposure to stress and elevated peri-ischemic glucocorticoid concentrations are associated with poor outcome among stroke patients and in rodent models of cerebral ischemia. Likely, stress and glucocorticoid exposure exacerbate stroke by sensitizing the neuroimmune response to ischemia; stroke induces an upregulation of pro-inflammatory cytokines which contributes to migration of leukocytes into cerebral tissue and neuronal death. Social isolation also appears to compromise stroke outcome through priming of the neuroimmune system. Among individuals who survive the stroke, residual inflammation is apt to further compromise quality of life via its effect on cognitive function and affect. A better understanding of the mechanisms through which stress and social environment modulate neuroimmune function could lead to improved treatment of stroke and other neurodegenerative diseases.

Oxytocin mediates social neuroprotection after cerebral ischemia.

BACKGROUND AND PURPOSE: The reduced incidence, morbidity, and mortality of stroke among humans with strong social support have been well-documented; however, the mechanisms underlying these socially mediated phenomena remain unknown, but may involve oxytocin (OT), a hormone that modulates some aspects of social behavior in humans and other animals. METHODS: In the present study, adult male mice were socially isolated (housed individually) or socially paired (housed with an ovariectomized female); social pairing increased hypothalamic OT gene expression. To determine whether a causal relationship exists between increased OT and improved stroke outcome, mice were treated with exogenous OT or OT receptor antagonist beginning 1 week before induction of experimental stroke via middle cerebral artery occlusion. RESULTS: Relative to social isolation, social housing attenuated infarct size, neuroinflammation, and oxidative stress following experimental stroke; the neuroprotective effect of social housing was eliminated by receptor antagonist treatment. In contrast, administration of OT to socially isolated mice reproduced the neuroprotection conferred by social housing. We further report evidence for a direct suppressive action of OT on cultured microglia, which is a key instigator in the development of neuroinflammation after cerebral ischemia. CONCLUSIONS: These findings support the hypothesis that OT mediates the neuroprotective effect of social interaction on stroke outcome.