<s>[INST] context: Hea Rate "A significant misconception is that shock occurs only with low B.P.(hypotension). Through various compensatory mechanisms hypotension is often a late .finding. Tachycardia, with or without tachyapnea may be the 1' or only sign of early compensated shock". Shock is an acute dramatic syndrome characterized by inadequate circulatory supply of oxygen so that the metabolic demands of vital organs and tissues are not met. Shock has been categorized into series of recognizable stage: ? Compensated Uncompensated Irreversible An initial insult triggers shock, thus disrupting blood flow to end organs leading to inadequate tissue perfusion. The body's compensatory mechanism is initiated to maintain perfusion to vital organs. If treatment is not introduced during this period, decompensated shock develops causing tissue damage that leads to multisystem organ dysfunction and death. Compensatory shock In the early phases of shock, multiple compensatory physiologic mechanisms act to maintain blood pressure and preserve tissue perfusion. - Blood pressure remains normal, initially, because of peripheral vasoconstriction and increased systemic vascular resistance. - Thus hypotension occurs late and is more a characteristic of uncompensated stage of shock. - Patients in compensated shock have relatively normal cardiac output and normal blood pressures but they have alteration in microcirculation that increase flow to some organs and reduce flow to other. - In infants compensatory increases in cardiac output are achieved primarily by "tachycardia" rather than by increase in stroke volume. - Hea rates of 190-210/min are common in infants with compensated shock. - On the other hand in older patients cardiac contractility (stroke volume) and (hea rate) increase to improve cardiac output. [/INST] question: Most sensitive indicator of intravascular volume depletion in infant aEUR' | options: A: Stroke volume B: Hea rate C: Cardiac output D: lood pressure | answer: B </s>