Phosphatidylinositol-bisphosphate regulates intercellular coupling in cardiac myocytes

Changes in the lipid composition of cardiac myocytes have been reported during cardiac hypertrophy, cardiomyopathy, and infarction. Because a recent study indicates a relation between low phosphatidylinositol-bisphosphate (PIP(2)) levels and reduced intercellular coupling, we tested the hypothesis that agonist-induced changes in PIP(2) can result in a reduction of the functional coupling of cardiomyocytes and, consequently, in changes in conduction velocity. Intercellular coupling was measured by Lucifer Yellow dye transfer in cultured neonatal rat cardiomyocytes. Conduction velocity was measured in cardiomyocytes grown on microelectrode arrays. Intercellular coupling was reduced by angiotensin II (43.7±9.3%, N=11) and noradrenaline (58.0±10.7%, N=11). To test if reduced intercellular coupling after agonist stimulation was caused by PIP(2)-depletion, myocytes were stimulated by angiotensin II (57.3±5.7%, N=14) and then allowed to recover in medium with or without wortmannin (an inhibitor of PIP(2) synthesis). Intercellular coupling fully recovered in control medium (102.1±8.9%, N=10), whereas no recovery occurred in the presence of wortmannin (69.3±7.8%, N=12). Inhibition of PKC, calmodulin, or arachidonic acid production did not affect the response to either angiotensin II or noradrenaline. Furthermore, decreasing or increasing PIP(2) also decreased and increased intercellular coupling, respectively. This supports the role of PIP(2) in the regulation of intercellular coupling. In beating myocytes, conduction velocity was reduced by angiotensin II stimulation, and recovery after wash out was prevented by inhibition of PIP(2) production. Reductions in PIP(2) inhibit intercellular coupling in cardiomyocytes, and stimulation by physiologically relevant agonists reduces intercellular coupling by this mechanism. The reduction in intercellular coupling lowered conduction velocity

Non-sedation versus sedation with a daily wake-up trial in critically ill patients receiving mechanical ventilation (NONSEDA Trial) : study protocol for a randomised controlled trial

BACKGROUND: Through many years, the standard care has been to use continuous sedation of critically ill patients during mechanical ventilation. However, preliminary randomised clinical trials indicate that it is beneficial to reduce the sedation level. No randomised trial has been conducted comparing sedation with no sedation, a priori powered to have all-cause mortality as primary outcome.The objective is to assess the benefits and harms of non-sedation versus sedation with a daily wake-up trial in critically ill patients. METHODS/DESIGN: The non-sedation (NONSEDA) trial is an investigator-initiated, randomised, clinical, parallel-group, multinational trial designed to include 700 patients from at least six ICUs in Denmark, Norway and Sweden.Inclusion criteria are mechanically ventilated patients with expected duration of mechanical ventilation >24 hours.Exclusion criteria are non-intubated patients, patients with severe head trauma, coma at admission or status epilepticus, patients treated with therapeutic hypothermia, patients with PaO2/FiO2 < 9 where sedation might be necessary to ensure sufficient oxygenation or place the patient in prone position.Experimental intervention is non-sedation supplemented with pain management during mechanical ventilation.Control intervention is sedation with a daily wake-up trial.The primary outcome will be all cause mortality at 90 days after randomization. Secondary outcomes will be: days until death throughout the total observation period; coma- and delirium-free days; highest RIFLE score; days until discharge from the intensive care unit (within 28 days); days until the participant is without mechanical ventilation (within 28 days); and proportion of patients with a major cardiovascular outcome. Explorative outcomes will be: all cause mortality at 28 days after randomisation; days until discharge from the intensive care unit; days until the participant is without mechanical ventilation; days until discharge from the hospital; organ failure.Trial size: we will include 700 participants (2 × 350) in order to detect or reject 25% relative risk reduction in mortality with a type I error risk of 5% and a type II error risk of 20% (power at 80%). DISCUSSION: The trial investigates potential benefits of non-sedation. This might have large impact on the future treatment of mechanically ventilated critically ill patients. TRIAL REGISTER: ClinicalTrials.gov NCT0196768, 09.01.2014