ACUTE RENAL FAILTURE
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ACUTE RENAL FAILTURE
Acute renal failure (ARF) refers to a sudden and usually reversible loss of renal function, which develops over a period of days or weeks and is usually accompanied by a reduction in urine volume.
Reversible Pre-Renal Acute Renal FailurePathogenesis
Clinical FeaturesHypotension and signs of poor peripheral perfusionPostural hypotension fall in SBP/DBP >20/10 mmHg early sign of hypovolaemia.The cause of reduced renal perfusion may be obvious or concealedMetabolic acidosis and hyperkalaemia may be (+)
ManagementEstablish and correct the underlying cause of the ARF.If hypovolaemia (+) replace with blood, plasma or isotonic salineOptimise systemic haemodynamics. Monitor CPU or pulmonary a wedge pressure.Correct metabolic acidosis- Restoration of blood volume will restore kidney function- Isotonic sodium bicarbonate
Established Acute Renal FailureFollowing severe or prolonged under perfusion of the kidney.Histology: Acute tubular necrosis Acute Tubular Necrosis:Cause(1)Ischaemia(2)Nephrotoxicity
Nephrotoxic ATNDirect toxicity of the causative agent to the tubular cells.
Recovery From ATNTubular cells can regenerateIf the patient is supported during the regeneration phase.Kidney function restoresRecovery phase-Diuretic phase
Other featureUraemic features- anorexia, nausea and vomiting drowsiness, apathy, confusion, muscle twitchingRespiratory rate increased Acidosis, pulmonary oedema, infection.Anaemia Blood loss, haemolysis disordered platelet function and disturbances of the coagulation cascade.
- Clinical Features of Established ARFReflect the causal condition trauma, septicemia or systemic diseases +1.Alterations in urine volume Oliguric (
URINARY TRACTOBSTRUCTIONSUGGESTED BY LOIN PAIN, RENAL COLIC OR DIFFICULTY IN MICTURITIONINVES- USGPROMPT RELIEF OF OBSTRUCTION RESTORES KIDNEY FUNCTION
MAJOR VASCULAR OCCLUTION OR SMALL VESSEL DISEASEURINE SHOW MINIMAL ABNORMALITIESMAY BE PRECIPITATED BY ACE INHIBITORS
RPGNSIGNIFICANT DIP STICK HAEMATURIAASSOSIATED WITH SYSTEMIC FEATURES BLOOD TESTS-ANA, ANCA, ANTI-GBM ANTIBODIESDIAGNOSIS- RENAL BIOPSY
ACUTE INTERSTITIAL NEPHRITISCAUSED BY ADVERSE DRUG REACTIONSMALL AMOUNT OF BLOOD AND PROTIEN IN URINEKIDNEYS NORMAL IN SIZETt-CESSATION OF DRUG AND PREDNISOLONE
DRUGSHAEMODYNAMIC EFFECTS- NSAIDs , ACE INHIBITORSDIRECT TOXICITY TO THE TUBULES- AMINOGLYCOSIDES
HematologyFull blood countBlood filmClotting screen, Group and save
BiochemistryUrea, electrolytes and creatinine calciumUrinalysisUrine MicrocopyQuantitative urinary protein measurement
3.MicrobiologyBlood cultureCRPMid-stream urineOther cultures4.Imaging Renal USGChest X rayECG
Immunoglobulin and protein electrophoresisUrinary Bence Jones ProteinComplementANA and ds DNA Extractable nuclear Antigen (ENA)Rheumatoid factor
Management1.Emergency resuscitationHyperkalaemia treated immediatelyCirculating blood volume restorationAcidosis-Isotonic sodium bicarbonate2.Addressing the underlying causeUSG showing urnary tract obstruction.ATN - restoring renal perfusion.Postrenal obstruction :Due to Pelvic or ureteric dilatation Percutaneous nephrostomy
Fluid and electrolyte balanceDaily fluid intake should = prev. day urine output + 500ml to cover unsensible loss.Abnormal loses like diarrhea electrolyte replacement. Since Na+ and K+ are retained their intake should be restricted Protein and energy intakeIn patients where dialysis is avoided protein restriction to 40g/dayIn patients with dialysis more dietary protein
Infection controlRegular clinical examination and microbiological investigation required.DrugsVasoactive drugs NSAIDs & ACE inhibitors are to be avoided.Renal Replacement therapy This may be required as supportive management in ARF.
Increased Plasma urea andcreatinine urea >30mmol/lCreatinine >6.8mgdlAt lower level Progressive biochemical deterioration.Hyperkalaemia K+ >6mmolMetabolic acidosis raise the plasma potassium further.Fluid overload and pulmonary oedema Uraemic pericarditis/ uraemic encephalopathy.
Best rate of small solute clearance.1 hour tt is prescribed. Subsequently when haemodyamically stable 3 4 hours 3 4 times a week.Haemodialysis 2 3 hrs every day severly catabolic
HaemofiltrationIntermittent 15 30 liters of plasma ultra filtrate exchanged for replacement fluid over 3 5 hours.Continuous1 2 liters of filtrate replaced higher rate of filtration MODS sepsis.
Peritoneal dialysisSeldom achieves adequate biochemical control
EfficientLess efficent4hours 3 times a week4 exchanges per day each 30 60 min. CAPD or 8 -10 hrs Automated PD2-3 day betweenFew hrs between ttRequires visit to hospitalPerformed at homeRequires adequate venous accesRequires an intact peritoneal cavity
Careful compliance to diet and fluid restrictionDiet & fluid less restrictedFluid removal compressed during tt period - haemody instabilitySlow continous fluid removal - asymptomaticInfection reld to vascular accessInfection Peritonitis,catheter reld infectionsPatients are, to some extent dependent on othersPatients can take full reponsibility of their tt