What is the cardiac output of a 50kg adult?



Shock vivaWhat is the cardiac output of a 50kg adult?Usually 70-80ml/kg in adult.If they loose 1L of blood, what are the physiological effect?CVSMinimize the change in effective blood volume and maintain COVenoconstriction, reduced venous compliance Transfer of fluid from ISF to plasmaMobilization of reservoir volumesRedistribution of cardiac output‘Restlessness’ increases muscle pump activity in the legsmaintain arterial BPperipheral vasoconstrictiontachycardiaRespMay have relative hypoxia at a tissue levelCan be a driver for increased minute ventilationMetabolic acidosis will also act to increase min vent.RenalDecrease in renal blood flowDecrease urine volumeDrop in BP is particularly effective by causing marked oliguriaEndocrineIncreased ADH due to input from low pressure volume receptorsIncreased release of angiotensin and aldosteroneIncreased thirstRelease of adrenaline and noradrenaline, cortisol and stress responseANP, BNP decreasedCNSIn large haemorrhage, may have decreased autoregulation, manifesting as changes in conscious state‘ischaemic CNS response’ below SBP 50mmHg: massive outflow of sympathetic stimulation from the ischaemic medulla in an effort to maintain cerebral perfusion at the expense of the rest of the bodyWhat are the sensors and effectors? Or: What are low and high pressure baroreceptors? What effect to the baroreceptors have?sensors: high pressure baroreceptors in carotid sinus and aortic archlow pressure baroreceptors in atria and veinsintrarenal baroreceptorseffectorssympathetic nervous system: CVS effectsrenal mechanismshormonal mechanismsWhat are the limits for the baroreceptors?when blood loss is greater than 20%, both arterial blood pressure and cardiac output decrease rapidly because the compensatory mechanisms become inadequateirreversible hypotension can occur with a blood loss of >30% (lactic acid accumulation can depress myocardial performance)Tell me about the effects on starlings forces?changes in starlings forces (notably pressure changes and concentration of proteins causing oncotic changes) result in a net reabsorption of interstitial fluid into bloodstimulation of SNS causes precapillary vasoconstriction, lowers capillary hydrostatic pressure, promotes fluid absorption into vascular compartmentincreases blood volumeup to 1000ml of fluid per hour may be transferred from the interstitial fluid into the intravascular compartmentTell me about the effects on the effects on the venous return and cardiac output curves.decreases mean systemic filling pressure and consequently reduced venous return such that cardiac output fallsmultiple compensatory mechansims activatedWhat are some special populations that may act differently?elderly: little reserve, decompensate quicklyvery young: compensate well initially then rapid deteriorationWhat are the delayed responses to major blood loss?responses aim to restore plasma volume, plasma proteins and red cellsplasma volume should return to normal by 12-72 hrsincreased plasma protein synthesis by the liver: takes several days to return to normal rangeincreased RBC production, EPO levels increase. Reticulocytes peak at 10 days and red cell levels fully restored in 4-8 weeks ................
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