Learning Critical Care Medicine

  From respirator lung to ventilator induced lung injury, we have travelled a long distance from the concept of barotrauma-volutrauma to stress-strain. Stress is defined as equal and opposite force developed in a material, when exposed to external force, while strain is change in the area or volume from baseline, brought about in this process. Stress-strain relationship is a function of material property, solid, viscous or viscoelastic. Current strategy of mechanical ventilation as endorsed by ARDS net, is limiting the tidal volume and plateau airway pressure to 6 ml per kg of predicted body weight and 30 cmH 2 O. Baby lung volume in ARDS is variable with severity of disease, worse is the ARDS, smaller is the baby lung. As baby lung has normal compliance, setting tidal volume according to predicted body weight, may be safe to unsafe depending upon baby lung volume. Lung behaves like viscoelastic material, which makes pulmonary mechanics time dependent. For a constant...

“Education is a progressive discovery of our own ignorance” Will Durant Since the inception of human society, people have been intrigued about the mystery of human behavior and emotions. Scholars came up with different explanations based on existing belief system, knowledge and evidences. Greek philosopher Aristotle believed heart as center of intelligence and emotions. Few centuries later, another Greek philosopher Galen explained that animal spirit originates in the heart and travels via the circulatory system to brain. Galen described his assumptions based on dissection of corpse, and further elaborated that cerebral ventricles are the epicenter of reasons and emotions. In the medieval period, accurate reproduction of images by artists like Da Vinci, Michelangelo and Rembrandt as well as rapid dissemination of knowledge by printing press, led to better understanding of human neuroanatomy and neurophysiology. As a result, by the end of eighteenth century, knowledge of huma...

"The difficulty lies, not in new ideas  but escaping old ones,  which ramifies,  for those brought up with them,  as most of us has been,  into every corner of our minds" - John Maynard Keynes  Hyponatremia is defined as serum sodium concentration less than 135 mmol/L. Biochemical severity of hyponatremia has been described as mild (S. Na of 130-135 mmol/L), moderate (125- 129 mmol/L) and Severe/ profound (125 mmol/L). Clinical severity of hyponatremia is recognized based on urgency of treatment. Severe symptoms are the result of cerebral edema and increased intracranial pressure with risk herniation. It manifests as vomiting, seizures, obtundation and cardiorespiratory distress.                                Moderately severe symptoms of hyponatremia are due to mild cerebral edema but no ris...

Pathophysiology of sepsis explains that after fluid resuscitation with 20-30 ml/kg ( which is the pressure volume of intravascular space), it is unlikely that septic shock will respond to additional fluid resuscitation. There may be transient response, as only five percent of the crystalloid will remain in the intravascular space, and rest of the fluid will accumulate in third space, giving rise to further organ damage. Fluid resuscitation further exacerbates the deranged physiology including vasodilatation. Multiple Clinical trials have suggested that positive fluid balance independently causes increased morbidity and mortality. Vasopressors should not be delayed after initial fluid resuscitation with 20-30ml/kg. Thereafter further fluid boluses may be given based on dynamic parameters of fluid responsiveness.