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113CASE 54:POSTOPERATIVEHYPOTENSIONHistoryA 65-year-old man underwent an elective abdominal aortic aneurysm repair. He hada medical history of heart failure secondary to ischaemic heart disease, chronic renalimpairment and type 2 diabetes mellitus.Postoperative complicationsPostoperatively this man developed acute abdominal pain and became hypotensive witha systolic blood pressure between 55 and 60 mmHg. He was given fluid resuscitation andrequired noradrenaline to keep his blood pressure elevated. His blood pressure remainedlow for about 30 minutes before it responded to fluids and vasopressors. He was olig-uric. A haemoglobin from the blood gas machine was 5.5 g/dL. He was taken to surgeryto repair a leak in the aortic graft and transfused 6 units of blood perioperatively. Heremained oliguric for 24 hours until his renal function was repeated on day 3.INVESTIGATIONSPre-opDay 1 post-opDay 3 post-opNormal rangeNa138131129135–145 mmol/LK4.85.86.53.5–5.0 mmol/LUrea1528323.0–7.0 mmol/LCreatinine14028033560–110mmol/LQuestionsWhat is the cause of this man’s acute renal impairment?What is the management of acute renal failure and hyperkalaemia?
114ANSWER 54The most likely cause of the renal impairment is renal failure secondary to hypovolaemiafrom an acute haemorrhage. The patient also has existing renal impairment, diabetesand coronary artery disease, all of which make him more at risk of renal hypoperfusion.Acute renal failure (ARF; also known as acute kidney injury) is defined as an acutedecline in glomerular filtration rate (GFR) from the baseline. The exact rise varies betweenguidelines. The RIFLE classification of ARF uses the level of rise in creatinine as a markerof the extent of renal damage. Urine output can be increased, decreased or absent. ARFis associated with increased mortality.The main causes of ARF can be usefully categorized into pre-, intrinsic and post-renal.The main pre-renal cause is impaired blood flow to the kidneys from hypovolaemia,haemorrhage, dehydration or sepsis. Intrinsic renal causes include nephrotoxic drugs,interstitial nephritis or glomerular disease. Outflow obstructions from stones, enlargedprostate or masses are post-renal causes.By day 3, this patient has developed hyperkalaemia and worsening renal function. Initialinvestigation should be directed at determining a diagnosis (in this case the most likelycause is hypovolaemia from an acute haemorrhage) and treating complications. Renalultrasound is useful as it will determine whether there is an obstructive cause.Immediately after the operation he did receive fluid resuscitation and vasopressor sup-port, but his kidneys were not perfused adequately for at least 30 minutes. Urgent man-agement was to stop the haemorrhage and transfuse with blood products. Now the focusshould be on maintaining euvolaemia to ensure intravascular volume is adequate toperfuse the kidneys. In this case, optimizing cardiac output and volume status presentsan additional challenge in view of his pre-existing renal impairment and heart failure. Acrystalloid such as 0.9% saline is acceptable. The exact volume of replacement should bedecided on parameters such as mean arterial pressure, cardiac index and other invasivemonitoring available. The use of vasopressors and inotropes may be required to maintainrenal perfusion pressures. Caution with intravascular volume replacement is necessary

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Term
Fall
Professor
NoProfessor
Tags
Test, fevers, The Grave,

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