Acute Renal Failure Flashcards
Functions of the kidney?
- Excretion of nitrogenous waste
- Regulation of water, electrolytes and BP
- Synthesis
Effect of kidney failure on salt and water homeostasis?
- Fluid overload
- peripheral oedema
- pulmonary oedema - Fluid depletion
Effect of kidney failure on BP control?
hypertension
Effect of kidney failure on the removal of uremic toxins?
Uremia
1. encephalopathy
2. pericarditis
3. nausea
4. vomiting
5. hiccup
6. bleeding tendency
7. neuropathy
Effect of kidney failure on calcium/phosphate balance?
- Hyperphosphatemia
- Hypocalcaemia
- Renal bone disease
- Tertiary hyperparathyroidism
Effect of kidney failure on EPO production?
anemia
Effect of kidney failure on potassium balance?
hyperkalemia
Effect of kidney failure on acid-base balance?
metabolic acidosis
Relevance of kidney disease?
- CKD = cardiovascular risk
- CVS events are common and the major cause of morbidity and mortality from CKD
- CKD is now affecting younger populations in their economic prime
- Likelihood of CVS death is far greater than progression to ESRD
Definition of acute renal failure?
Rapid decline in GFR over days or weeks
AKI results in?
- Retention of nitrogenous wastes, creatinine and other toxins
- Oliguria occurs in ≈ 50%
Note: May be reversible
Causes of in hospital morbidity and mortality?
because of underlying illnesses and high incidence of subsequent complications
Complicates ≈ 5% of hospital admissions, ≈ 30% of ICU admissions
Criteria for AKI categories?
- change in serum creatinine levels
- urine output
Category 1 for AKI?
- 1.5 – 1.9 times increase in SCr from baseline or
>0.3mg/dl increase in se - <0.5ml/kg/hr for 6 to 12 hours
Category 2 for AKI?
- 2.0 – 2.9 x increase in SCr from baseline
- <0.5ml/kg/hr for >12 hours
Category 3 for AKI?
- 3.0 x increase in SCr from baseline or Creatinine >4mg/dl
- <0.3ml/kg/hr over 24 hours or
Anuria > 12 hours
Undergraduate classification of AKI?
- Pre Renal - Circulatory Failure = “Shock”
- Renal - The cells of the kidney
- Post Renal - Obstruction
Pre-renal failure?
- 50 – 60% of all cases
- Renal parenchyma preserved
- Falling renal blood flow leads to a falling GFR
- This might be due either to changes in the circulation, or to intrarenal vasomotor changes that drop glomerular perfusion pressures
Prerenal causes of AKI?
- Hypovolaemia
- dehydration or haemorrhage - Hypotension without hypovolaemia
- cirrhosis or septic shock - Low cardiac output
- cardiac failure or cardiogenic shock - Renal artery stenosis
Post renal AKI?
Mechanical obstruction of the urinary collecting system
- Renal pelvis, ureters, bladder, or urethra
- Obstructive uropathy
Postrenal causes of AKI?
- Ureteric obstruction
- Stone disease, tumor, fibrosis, ligation during pelvic surgery - Bladder neck obstruction
- Benign prostatic hypertrophy (BPH), CA prostate, neurogenic bladder, tricyclic antidepressants, ganglion blockers, bladder tumor, stone disease, hemorrhage/clot - Urethral obstruction
- Strictures, tumor, phimosis - Intra-abdominal hypertension
- Tense ascites - Renal vein thrombosis
Describe prerenal AKI?
- caused by renal hypoperfusion
- Integrity of renal parenchyma is preserved = pre-renal
- 50-60% of cases
Causes of intrinsic renal failure?
- tubular
- interstitial nephritis : 10%
- ATN : 75-80%
> ischemic
> toxic - glomerular
- glomerulonephritis - vascular
- vasculitis
Describe postrenal failure?
- Obstruction of urine flow
- < 5%
Urine sediment used in differential diagnosis?
- normal or few RBC, WBC
- granular casts
- RBC casts
- WBC casts
- Eosinophiluria
- Crystalluria
3 phases of acute renal failure?
- Initial phase: exposure to ischemia / toxin.
- Evolution of parenchymal injury
- ARF preventable - Maintenance phase: established injury
- may last 1-2 weeks or months - Recovery phase: repair and regeneration
Management of prerenal ARF?
- replace fluid and what was lost
- controversy colloid vs. crystalloid
- Normal Saline seems best
- Urinary/GI losses usually hypotonic - If CHF treat arrhythmias, inotropes, reduce preload/afterload
- If cirrhosis, paracentesis ± albumin, FFP, shunt
- Remove offending drugs
Management of intrinsic ARF?
- Prevention:- optimize cardiac function, volume status
- caution with ACEI, NSAIDS, vasodilators
- Treat according to specific cause
Diagnosis of ARF?
- History and examination
- Routine bloods
- Extra bloods – bicarbonate, CK, 4. CRP + blood cultures
- ECG
- CXR
Treatment of ARF?
- Immediate - Airway and Breathing
- Circulation
- restore renal perfusion (fluid resuscitation ± inotrope)
- hyperkalaemia
- pulmonary oedema - Remove causes
- drugs
- sepsis - Exclude obstruction & consider ‘renal’ causes
- are the pre-renal causes sufficient to account for ARF? - Ask for help: ICU or renal unit
Indications for dialysis in ARF?
A E I O U
A – severe metabolic acidosis of renal origin and refractory to medical therapy
E – electrolyte abnormalities – refractory hyperkalemia =>6.5
I – intoxication with dialysable compounds
O – fluid overload especially pulmonary edema refractory to diuretic therapy
U- uremia – pericarditis, bleeding, confusion (encephalophathy)
Oligo/anuria
Features of the ECG in hyperkalemia?
- loss of P wave
- tall peaked T wave
- widened QRS with tall T wave
Management of hyperkalemia?
Most important when K+ >6.0
1. Remove offending agent e.g. drugs
2. 10mls of 10% Calcium gluconate IV
3. 10 units of Soluble insulin with 50mls of 50%dextrose IV – then monitor blood sugar
4. Nebulised salbutamol/albuterol
5. Frusemide if in pulmonary edema
6. Oral Kayexelate (K binding resin)
