Hydrogen sulfide...when rotten eggs save lives

Hydrogen sulfide (H2S), which has a characteristic rotten egg smell, is a colorless, flammable, water-soluble gas that is primarily considered a toxic agent due to its ability to inhibit mitochondrial respiration through blockade of cytochrome c oxidase. Recent research has demonstrated that H2S in low quantities may have the potential to limit cell death (Lefer, 2007). Inhibition of respiration is potentially toxic; however, if depression of respiration occurs in a controlled manner, it may allow non-hibernating species exposed to inhaled H2S to enter a state akin to suspended animation (i.e., a slowing of cellular activity to a point where metabolic processes are inhibited but not terminal) and thereby increase tolerance to stress. H2S also may cause activation of ATP-dependent K+ channels, cause vasodilation properties, and serve as a free radical scavenger. H2S has been shown to protect against whole-body hypoxia, lethal hemorrhage, and ischemia-reperfusion injury in various organs including the kidney, lung, liver, and heart. Currently, effort is underway for development of gas-releasing molecules that could deliver H2S and other therapeutic gases to diseased tissue (Bannenberg and Vieira, 2009). Though H2S has clinical potential, further verification in preclinical models is necessary as is more information regarding the route of delivery, timing, formulation, and concentration of H2S.

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Driving Pressure in ARDS: A new concept!

Driving Pressure and Survival in the Acute Respiratory Distress Syndrome Marcelo B.P. Amato, M.D., Maureen O. Meade, M.D., Arthur S. Slutsky, M.D., Laurent Brochard, M.D., Eduardo L.V. Costa, M.D., David A. Schoenfeld, Ph.D., Thomas E. Stewart, M.D., Matthias Briel, M.D., Daniel Talmor, M.D., M.P.H., Alain Mercat, M.D., Jean-Christophe M. Richard, M.D., Carlos R.R. Carvalho, M.D., and Roy G. Brower, M.D. N Engl J Med 2015; 372:747-755 February 19, 2015 DOI: 10.1056/NEJMsa1410639 BACKGROUND Mechanical-ventilation strategies that use lower end-inspiratory (plateau) airway pressures, lower tidal volumes (V T ), and higher positive end-expiratory pressures (PEEPs) can improve survival in patients with the acute respiratory distress syndrome (ARDS), but the relative importance of each of these components is uncertain. Because respiratory-system compliance (C RS ) is strongly related to the volume of aerated remaining functional lung during disease (termed functional lung size)...

Anaphylaxis updates part 2- Empty Ventricle Syndrome

Patients with anaphylaxis should not suddenly sit, stand, or be placed in the upright position. Instead, they should be placed on the back with their lower extremities elevated or, if they are experiencing respiratory distress or vomiting, they should be placed in a position of comfort with their lower extremities elevated. This accomplishes 2 therapeutic goals: 1) preservation of fluid in the circulation (the central vascular compartment), an important step in managing distributive shock; and 2) prevention of the empty vena cava/empty ventricle syndrome, which can occur within seconds when patients with anaphylaxis suddenly assume or are placed in an upright position. Patients with this syndrome are at high risk for sudden death. They are unlikely to respond to epinephrine regardless of route of administration, because it does not reach the heart and therefore cannot be circulated throughout the body

Epidural catheter tests...not only the test dose

Siphon test The catheter is held upright and a fluid level sought. If the catheter is then elevated, the fluid level should fall (see inset) as the fluid siphons in to the epidural space, which is usually under negative pressure compared with atmospheric. If the fluid column continues to rise, this may suggest subarachnoid placement. The siphon test can be reassuring, but is not mandatory. Aspiration This should be considered mandatory. The Luer connector is attached to the catheter and a syringe is used to apply negative pressure. Free and continued aspiration of clear fluid can indicate subarachnoid placement of the catheter. However, if saline has been used for loss of resistance, it is not unusual for a small amount of this to be aspirated. If there is doubt, the aspirated fluid can be tested for glucose (cerebrospinal fluid will generally test positive) or mixed with thiopentone (cerebrospinal fluid forms a precipitate). If blood is freely and continuously aspirated, this sug...

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