Continuous-Infusion Etomidate in a Patient Receiving Extracorporeal Membrane Oxygenation.

We describe a 16-year-old, 65-kg male deployed on extracorporeal membrane oxygenation (ECMO) for refractory respiratory failure secondary to ingestion of multiple substances. During his ECMO course, standard sedative and analgesic strategies failed and alternative medications were used. The patient received various dosages of fentanyl, morphine, hydromorphone, clonidine patches, dexmedetomidine, lorazepam, methadone, pentobarbital, olanzapine, and propofol. Despite administration of multiple agents, on day 29 of ECMO the patient experienced elevated blood pressures due to agitation, and continuous infusion etomidate was started. At the time of etomidate initiation, the osmolar gap was 8 mOsm/kg. During etomidate therapy, the blood pressure remained normal, sedative agents were slowly weaned, and the patient required few PRN medications. On day 6 of etomidate, the osmolar gap increased to 127 mOsm/kg and etomidate was discontinued. Continuous-infusion ketamine was started, but the blood pressure was not controlled. Metabolic acidosis is a known side effect of etomidate due to inclusion of propylene glycol as a pharmaceutical solvent in the formulation. Despite high-dose etomidate (20 mcg/kg/min) for approximately 6 days, our patient did not experience metabolic acidosis. Absence of this adverse effect caused us to question the role of the ECMO circuit. To our knowledge, this is the first report of the use of continuous-infusion etomidate during ECMO. Etomidate infusion could be considered in difficult-to-manage patients after other alternatives have failed.

Interferon-Stimulated Gene 15 Upregulation Precedes the Development of Blood-Brain Barrier Disruption and Cerebral Edema after Traumatic Brain Injury in Young Mice.

Recent studies show that myosin light chain kinase (MLCK) plays a pivotal role in development of cerebral edema, a known complication following traumatic brain injury (TBI) in children and a contributing factor to worsened neurologic recovery. Interferon-stimulated gene 15 (ISG15) is upregulated after cerebral ischemia and is neuroprotective. The significant role of ISG15 after TBI has not been studied. Postnatal Day (PND) 21 and PND24 mice were subjected to lateral closed-skull injury with impact depth of 2.0 or 2.25 mm. Behavior was examined at 7 d using two-object novel recognition and Wire Hang tests. Mice were sacrificed at 6 h, 12 h, 24 h, 48 h, 72 h, and 7 d. ISG15 and MLCK were analyzed by Western blot and immunohistochemistry, blood-brain barrier (BBB) disruption with Evans Blue (EB), and cerebral edema with wet/dry weights. EB extravasation and edema peaked at 72 h in both ages. PND21 mice had more severe neurological deficits, compared with PND24 mice. PND24 mice showed peak ISG15 expression at 6 h, and PND21 mice at 72 h. MLCK peaked in both age groups at 12 h and co-localized with ISG15 on immunohistochemistry and co-immunoprecipitation. These studies provide evidence, ISG15 is elevated following TBI in mice, preceding MLCK elevation, development of BBB disruption, and cerebral edema.

Inhibition of Myosin light-chain kinase attenuates cerebral edema after traumatic brain injury in postnatal mice.

Traumatic brain injury (TBI) in children less than 8 years of age leads to decline in intelligence and executive functioning. Neurological outcomes after TBI correlate to development of cerebral edema, which affect survival rates after TBI. It has been shown that myosin light-chain kinase (MLCK) increases cerebral edema and that pretreatment with an MLCK inhibitor (ML-7) reduces cerebral edema. The aim of this study was to determine whether inhibition of MLCK after TBI in postnatal day 24 (PND-24) mice would prevent breakdown of the blood-brain barrier (BBB) and development of cerebral edema and improve neurological outcome. We used a closed head injury model of TBI. ML-7 or saline treatment was administered at 4 h and every 24 h until sacrifice or 5 days after TBI. Mice were sacrificed at 24 h, 48 h, and 72 h and 7 days after impact. Mice treated with ML-7 after TBI had decreased levels of MLCK-expressing cells (20.7±4.8 vs. 149.3±40.6), less albumin extravasation (28.3±11.2 vs. 116.2±60.7 mm(2)) into surrounding parenchymal tissue, less Evans Blue extravasation (339±314 vs. 4017±560 ng/g), and showed a significant difference in wet/dry weight ratio (1.9±0.07 vs. 2.2±0.05 g), compared to saline-treated groups. Treatment with ML-7 also resulted in preserved neurological function measured by the wire hang test (57 vs. 21 sec) and two-object novel recognition test (old vs. new, 10.5 touches). We concluded that inhibition of MLCK reduces cerebral edema and preserves neurological function in PND-24 mice.

Albumin causes increased myosin light chain kinase expression in astrocytes via p38 mitogen-activated protein kinase.

Myosin light chain kinase (MLCK) plays an important role in the reorganization of the cytoskeleton, leading to disruption of vascular barrier integrity in multiple organs, including the blood-brain barrier (BBB), after traumatic brain injury (TBI). MLCK has been linked to transforming growth factor (TGF) and rho kinase signaling pathways, but the mechanisms regulating MLCK expression following TBI are not well understood. Albumin leaks into the brain parenchyma following TBI, activates glia, and has been linked to TGF-ß receptor signaling. We investigated the role of albumin in the increase of MLCK in astrocytes and the signaling pathways involved in this increase. After midline closed-skull TBI in mice, there was a significant increase in MLCK-immunoreactive (IR) cells and albumin extravasation, which was prevented by treatment with the MLCK inhibitor ML-7. Using immunohistochemical methods, we identified the MLCK-IR cells as astrocytes. In primary astrocytes, exposure to albumin increased both isoforms of MLCK, 130 and 210. Inhibition of the TGF-ß receptor partially prevented the albumin-induced increase in both isoforms, which was not prevented by inhibition of smad3. Inhibition of p38 MAPK, but not ERK, JNK, or rho kinase, also prevented this increase. These results are further evidence of a role of MLCK in the mechanisms of BBB compromise following TBI and identify astrocytes as a cell type, in addition to endothelium in the BBB, that expresses MLCK. These findings implicate albumin, acting through p38 MAPK, in a novel mechanism by which activation of MLCK following TBI may lead to compromise of the BBB.

MLCK210 gene knockout or kinase inhibition preserves lung function following endotoxin-induced lung injury in mice.

Barrier dysfunction, involving the endothelium or epithelium, is implicated in the pathophysiology of many disease states, including acute and ventilator-associated lung injury. Evidence from cell culture, in vivo and clinical studies, has identified myosin light chain kinase as a drug discovery target for such diseases. Here, we measured disease-relevant end points to test the hypothesis that inhibition of myosin light chain kinase is a potential therapeutic target for treatment of barrier dysfunction resulting from acute lung injury. We used a combined gene knockout and chemical biology approach with an in vivo intact lung injury model. We showed that inhibition of myosin light chain kinase protects lung function, preserves oxygenation, prevents acidosis, and enhances survival after endotoxin exposure with subsequent mechanical ventilation. This protective effect provided by the small molecule inhibitor of myosin light chain kinase is present when the inhibitor is administered during a clinically relevant injury paradigm after endotoxin exposure. Treatment with inhibitor confers additional protection against acute lung injury to that provided by a standard protective mode of ventilation. These results support the hypothesis that myosin light chain kinase is a potential therapeutic target for acute lung injury and provide clinical end points of arterial blood gases and pulmonary compliance that facilitate the direct extrapolation of these studies to measures used in critical care medicine.

Reducing acquired infections in the NICU: observing and implementing meaningful differences in process between high and low acquired infection rate centers.

BACKGROUND: Acquired infection is one of the most prevalent sources of concern in neonatal intensive care units (NICUs). Center-to-center variation has been noted by both the National Nosocomial Infection Surveillance System and the Vermont Oxford Network suggesting that site of care influences outcomes including acquired infection. OBJECTIVE: To reduce the acquired infection rate by isolating and then implementing meaningful process differences between high and low infection rate centers. DESIGN/METHOD: A multistaged observation and intervention study. The primary outcome measure was defined as a positive blood culture, collected more than 3 days after birth. Hospital patient days along with infection episodes were collected for all NICU admissions in the network during the baseline and post-implementation periods. A detailed observation guide was used during site visits to high and low infection rate centers. The observations recorded in the guide allowed the team to isolate meaningful differences, which were shared with the network. Individual NICUs decided which of the meaningful differences, if any, to implement. To estimate the impact on costs, additional data were gathered in a case-matched series of infants in one demonstration site. RESULTS: In all, 15 meaningful differences were isolated and shared with the network. The network rate for acquired infection dropped from 3.8 to 2.9 episodes per 1000 patient days. In the demonstration site, the infection rate dropped from 7.4 to 4.0 per 1000 patient days. CONCLUSION: Isolation of process level differences between high and low performing centers followed by implementation of these meaningful differences may reduce acquired infections. Other targeted areas of care may benefit from this quality improvement methodology.

Protein kinase involved in lung injury susceptibility: evidence from enzyme isoform genetic knockout and in vivo inhibitor treatment.

Acute lung injury (ALI) associated with sepsis and iatrogenic ventilator-induced lung injury resulting from mechanical ventilation are major medical problems with an unmet need for small molecule therapeutics. Prevailing hypotheses identify endothelial cell (EC) layer dysfunction as a cardinal event in the pathophysiology, with intracellular protein kinases as critical mediators of normal physiology and possible targets for drug discovery. The 210,000 molecular weight myosin light chain kinase (MLCK210, also called EC MLCK because of its abundance in EC) is hypothesized to be important for EC barrier function and might be a potential therapeutic target. To test these hypotheses directly, we made a selective MLCK210 knockout mouse that retains production of MLCK108 (also called smooth-muscle MLCK) from the same gene. The MLCK210 knockout mice are less susceptible to ALI induced by i.p. injection of the endotoxin lipopolysaccharide and show enhanced survival during subsequent mechanical ventilation. Using a complementary chemical biology approach, we developed a new class of small-molecule MLCK inhibitor based on the pharmacologically privileged aminopyridazine and found that a single i.p. injection of the inhibitor protected WT mice against ALI and death from mechanical ventilation complications. These convergent results from two independent approaches demonstrate a pivotal in vivo role for MLCK in susceptibility to lung injury and validate MLCK as a potential drug discovery target for lung injury.