Renal physiology Flashcards
Which of the following statements do not correspond to the definition of AKI
- Increase in serum creatinine to less than 2 times baseline, which is known or presumed to have occurred within the prior 7 days
- Urine volume >0.5 ml/kg/h for 12 hour
- Increased urine protein levels more than 30 mg/dl
Which of the following statements correspond to the definition of AKI stages?
- Increase of Cr ≥1.5-1.9 times baseline or urine output (UO) <0.5 ml/kg/h for >6 consecutive hours
- Increase of Cr ≥2-2.9 times baseline or UO <0.5 ml/kg/hours for ≥12 hours
- Increase of Cr ≥3 times baseline or UO <0.3 ml/kg/h for ≥24 hours or anuria for ≥12 hours
- Initiation of RRT is defined as AKI stage 3
What period of time do not correspond to AKI?
- Up to 24 hours,
- More than 72 hours,
- More than 7 days,
- More than 90 days
What are the factors leading to mis-diagnosis of AKI?
- High level of ADH,
- Obesity,
- Diabetes mellitus,
- Muscle mass loss
A 42-year-old man has been in intensive care for 108 days after contracting COVID. He has had a tracheostomy and is slowly weaning from the ventilator. He required renal replacement therapy 10 days after admission, although he is now off haemodiafiltration, passing good volumes of urine. His baseline serum creatinine was 95 µmol/L and his current serum creatinine is 178 µmol/L. His serum creatinine peaked at 398 µmol/L prior to renal replacement therapy. The following statement is true regarding his renal function?
B is the correct answer -
The definition of acute kidney disease is the criteria for AKI persisting for more than 7 days but less than 90 days. After 90 days, ongoing renal impairment is considered chronic and staged accordingly. This man developed AKI 10 days after admission and still has renal impairment 98 days later
a.
He has stage 1 acute kidney injury .
b.
He is now classed as having chronic kidney disease.
c.
Although he has developed acute kidney disease, he has a good chance of return to normal renal function.
d.
His acute kidney injury is ongoing with an increased risk of developing acute kidney disease and later chronic kidney disease.
e.
He is now classed as having acute kidney disease, with an increased risk of developing chronic kidney disease.
A 58-year-old man with type 2 diabetes mellitus, obesity, hypertension and chronic kidney disease has been admitted to the intensive care unit after open surgery for an abdominal aortic aneurysm. His weight is estimated at 130 kg. His baseline creatinine is 278 µmol/L and the following day he has a serum creatinine of 341 µmol/L. His urine output averages between 30 and 60 mL/h. The following is true about his renal function?
Patient has stage 1 AKI
A 72-year-old man has had an elective knee replacement. His has a significant past medical history of ischaemic heart disease, type-2 diabetes mellitus, chronic renal disease (CKD stage 3) and sleep apnoea secondary to obesity. His pre-operative serum creatinine was 172 µmol/L. His serum creatinine has increased to 220 µmol/L but he is in considerable pain and you have been asked to review his drug chart. His current medications include; ramipril, bisoprolol, furosemide, atorvastatin and doxazocin (usual medications) and ibuprofen, oral morphine, ondansetron, omeprazole and dalteparin (started since surgery). The following would be the best course of action.?
Continue the bisoprolol, stop ramipril and furosemide and review need for doxazocin. Stop the ibuprofen, change the morphine to oral oxycodone, continue the omeprazole and continue the dalteparin but with anti-Xa monitoring.
Feedback:
Reviews of drug charts can be complicated when considering acute problems on the background of chronic disease. Bisoprolol should be continued if possible because of the risk of tachyarrhythmias secondary to acute withdrawal. Ramipril should be temporarily stopped because of its potential impact on AKI although it had an overall protective effect in many cases of CKD. The need for doxazocin in the immediate post-operative period is very much dictated by the patient’s cardiac status and furosemide should be held until the patient’s fluid status is optimised peri-operatively. Its use should then be guided by the clinical status of the patient. Furosemide does not protect the kidneys from AKI.
Ibuprofen is a potent nephrotoxin and should be avoided in the peri-operative patient with additional risks of AKI (e.g. diabetes mellitus, CKD). Omeprazole is a potential nephrotoxin although most nephrotoxicity is observed after long term use. Its advantages, protecting against stress ulcers, outweigh the risk of AKI in most major peri-operative patients. Morphine has a potent renally excreted metabolite which may accumulate in renal impairment. Oxycodone is less effected by kidney injury. Low molecular weight heparins may accumulate in AKI but they can be safely used if anti-Xa measurements are used to check for accumulation.
An 82 year old woman has been admitted to intensive care with biliary sepsis. She has been in inten-sive care for 24 hours. Although she is frail with a weight of 48 kg, she has minimal past medical his-tory and no known chronic kidney disease and no further information about her is available. She has been given 4.5g piperacillin-tazobactam and has been fluid resuscitated. She is requiring norepinephrine at 0.1 µg/kg/min to maintain a mean arterial pressure of > 65 mmHg. Her urine output over the last 12 hours has averaged 20 mL/hour and her serum creatinine is 88 88 µmol l/L. The following is true regarding her renal function?
She has AKI stage 2 based on her urine output over 12 hours.
Feedback:
The urine output is low and consistent with AKI. Although the serum creatinine is only 88 µmol/L, the woman’s fragility and low weight suggest, in the absence of a past medical history of chronic kidney disease, that her baseline creatinine is likely to be low and an increase of x1.5 or of > 26.5 µmol/L is certainly possible, if not likely.
What is the definition of AKD?
AKD occurs in any patient in whom an AKI persist for more than 7 days and less than 90 days. It is not dependent on the stage of AKI observed nor on the severity of the renal impairment ongoing.
Cytochrome P450 inhibitors?
- Macrolides
Antibiotics associated with an increased risk of acute kidney injury include:
- Penicillin
- Fluoroquinolones
- Aminoglycosides
Certain co-morbidities are associated with an increased risk of developing AKI in hospital. These include?
CCF, COPD , Obesity, HTN
20% of patients admitted to hospital with heart failure will develop an AKI and the development of AKI is associated with an increased risk of mortality. COPD is an independent risk factor for the development of both CKD and AKI. Obesity may increase the risk of AKI through changes to venous blood flow and pressures and through systemic inflammation. Hypertension is an independent risk factor for AKI.
Modifiable risk factors for developing AKI include:?
- High fluid volume resuscitation
- NSAIDs
- PPI
Recovery from sepsis related AKI or AKD?
Is associated with an increased risk of mortality even if renal recovery is complete
Feedback:
Serum creatinine is a poor measure of renal function in AKI. Either SCr may be slow to recover despite improving renal function, or SCr may be falsely low, especially in longer term ICU patients in whom muscle wasting has occurred.
Approximately 50% of patients with sepsis related AKD will not have renal function return to baseline by the time they leave hospital.
Patients who have an AKI which recovers have a higher mortality than patients with no AKI.
Patients with any severity of underlying CKD are more likely to progress to more severe CKD or end stage renal failure if they suffer AKI.
The following may be considered non-modifiable risk factors for developing an acute kidney injury?
- Increasing Age
- COPD
- Afro-Caribbean
- Male gender
Feedback:
Two recent meta-analyses including one with over 6 million patients, found that men are more likely to develop HA-AKI with an odds ratio of 1.23 [1.11, 1.36] Neugarten 2018, Grams 2015)
Older age, Afro-American descent and certain chronic medical conditions increase the risk of developing AKI. Other conditions include, hypertension, diabetes mellitus, cardiac failure, ischaemic heart disease, chronic kidney disease, obesity and some forms of malignancy.