This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Most sensitive indicator of intravascular volume depletion in infant - \nSelect and explain. \nA. Stroke volume, B. Heart rate, C. Cardiac output, D. Loud pressure', 'role': 'user'}, {'content': 'Answer: B \nExplanation: “A significant misconception is that shock occurs only with low B.P. (hypotension).\nThrough various compensatory mechanisms, hypotension is often a late ending.\nTachycardia, with or without tachy apnea may be the 1 st or only sign of early compensated shock”. Shock is an acute dramatic syndrome characterized by the inadequate\ncirculatory supply of oxygen so that the metabolic demands of vital organs and tissues are not met. Shock has been categorized into a series of the recognizable stage: -\nCompensated Uncompensated Irreversible An initial insult triggers shock, thus disrupting blood flow to end organs leading to inadequate tissue perfusion.\nThe body9s compensatory mechanism is initiated to maintain perfusion to vital organs. If treatment is not introduced during this period,\ndecompensated shock develops causing tissue damage that leads to multisystem organ dysfunction and death. Compensatory shock\n\nIn the early phases of shock, multiple compensatory physiologic mechanisms act to maintain blood pressure and preserve tissue perfusion.\n\nBlood pressure remains normal, initially, because of peripheral vasoconstriction and increased systemic vascular resistance.\nThus hypotension occurs late and is more a characteristic of the uncompensated stage of shock Patients in compensated shock have relatively normal cardiac output and normal blood\npressures but they have an alteration in microcirculation that increases flow to some organs and reduce flow to other.\nIn infants, compensatory increases in cardiac output are achieved primarily by “tachycardia” rather than by an increase in stroke volume.\nHeart rates of 190-210/min are common in infants with compensated shock. On the other hand in older patients, cardiac contractility (stroke volume) and (heart rate) increase to improve cardiac output', 'role': 'assistant'}]