Acute Kidney Injury (AKI) - Clinical Opal
Edward is a 63 year old patient admitted to ICU yesterday following an open AAA repair. Intraoperative cross clamping time of his renal artery was 72 minutes. Edward is currently intubated and ventilated and has become haemodynamically unstable with a MAP of 50 and urine output <0.5 mL/kg.hr. Morning blood shows an elevated urea and creatinine level.
What renal protection strategies should be considered to help manage Edward’s worsening AKI?
Ensure optimal fluid hydration using intravenous crystalloids, maintain Edward’s MAP greater than 65 mmHg with an IV vasopressor and avoid nephrotoxic medications.
Renal protection strategies such as volume and blood pressure control are crucial to minimize kidney damage, support renal recovery, and prevent further complications due to AKI. Close monitoring of renal function, blood pH, electrolytes and urine output is also essential. It is important to consider the medications that Edward is being administered with modifications to those that are nephrotoxic. Assess the specific cause and severity of AKI when planning treatment and medication adjustments.
Optimising blood pressure and fluid balance in acute kidney injury
Management of blood pressure and cardiac output require careful titration of fluids and vasoactive medication. It is recommended that any volume deficit be corrected with isotonic crystalloids, and a positive fluid balance is maintained whilst avoiding fluid overload. Commencement of a noradrenaline infusion titrated to MAP will assist with maintaining adequate perfusion to the kidneys and potentially prevent further injury. Cardiac and blood pressure monitoring via an arterial line is necessary to manage both fluid and vasoactive medications.
Monitoring renal function: key indicators in AKI
Edward’s renal function should be closely monitored with regular serum creatinine levels, as well as hourly urine output measurement to detect and grade severity of his AKI. KDIGO defines Acute Kidney Injury (AKI) as any of the following:
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An increase in serum creatinine by ≥0.3 mg/dL within 48 hours.
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An increase in serum creatinine to ≥1.5 times baseline within the prior 7 days.
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Urine volume <0.5 mL/kg/hour for 6 hours.
Management of hyperkalaemia with calcium gluconate or calcium chloride for cardiac protection, as well as insulin (in dextrose) to lower blood potassium and thus prevent lethal arrhythmias is imperative. Enteral feeding should be considered and insulin therapy may be necessary to ensure a target blood glucose level of 6.1–8.3mmol/l. Metabolic acidosis can be corrected using sodium bicarbonate, although it may become necessary to use dialysis to further manage these imbalances.
Adjusting medications to prevent further kidney damage
Medications that are eliminated by the kidneys such as vancomycin, aminoglycosides, dabigatran and rivaroxaban require dose adjustments based on renal function (creatinine clearance or eGFR) to avoid toxicity. Diuretics should be used with caution in AKI, particularly in those patients with reduced renal perfusion, as they can exacerbate dehydration or electrolyte imbalances.
Nephrotoxic drugs including NSAIDs, ACE inhibitors, ARBs, chemotherapy medications such as cisplatin and methotrexate, as well as contrast drugs should be used with caution or avoided altogether.
Renal replacement therapy and the haemofilter
If Edward’s AKI progresses or if his injury does not respond to conservative measures, dialysis may be necessary to support renal function. Continuous renal replacement therapy (CRRT) would be the recommended method due to Edward’s haemodynamic instability.
Renal protection in AKI involves optimizing hydration and blood pressure, minimizing nephrotoxic insults, and adjusting medications according to renal function. Managing electrolyte abnormalities and considering dialysis in severe cases is essential for improving outcomes.
Related courses
Critical Care Nursing: CRRT and managing patients with acute kidney injury
References
Australian Institute of Health and Welfare 2015. Acute kidney injury in Australia: a first national snapshot. Cat. no. PHE 190. Canberra: AIHW.Acute kidney injury in Australia: a first national snapshot (full publication 27 August 2015 edition) (AIHW)
Farkas, J. (2023) Acute Kidney Injury. The Internet Book of Critical Care. Acute Kidney Injury - EMCrit Project
Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney inter., Suppl. 2012; 2: 1–138 KI_SuppCover_2.1.indd
Nickson, C. (2024) Acute Kidney Injury • LITFL • CCC Renal
Nickson, C. (2020) Renal failure Post AAA Repair • LITFL • CCC Vascular
Nickson, C. (2024) Urea-Creatinine Ratio • LITFL • CCC DDx
Jenny Browne, RN, Cert IV (TAE), CritCareCert, MN(AdvClinEd), has an extensive background in critical care nursing and education. Jenny has worked across a variety of Australian ICUs, including the John Hunter Hospital (Newcastle), Princess Margaret Hospital (Perth) and the Royal Adelaide Hospital. She has been an ALS and PALS instructor for over 12 years, including with the ACCCN, and is also a sessional academic at the University of Newcastle.
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