What Happens When The Kidneys Stop Working

What Happens When The Kidneys Stop Working

Loss of excretory function – accumulation of waste productsLoss of homeostatic function – disturbance of electrolyte balance, loss of acid-base control, inability to control volume homeostasisLoss of endocrine functionClinical features are determined by rate of deterioration

What Causes The Symptoms Of Lethargy And Anorexia

Patients with renal failure present with lethargy and anorexiaAccumulation of nitrogenous waste products, hormones, peptidesAcidosisHyponatraemiaVolume depletion (low BP)Anaemia

Salt And Water Imbalance In Patients With Renal Problems

Salt and water loss usually found in patients with tubulointerstitial disorders in which concentrating mechanisms damagedMore usual for patients with renal dysfunction to have difficult excreting salt and water leading to sodium retension (resulting in hypertension, oedema and pulmonary oedema)Salt and water imbalance caused by – inability to decrease sodium excretion, osmotic diuresis due to high conc. of waste substances in urineHigh loss of salt and water results in volume depletion causing low blood pressure

Implications Of Acidosis

Caused by decreased excretion of H+ ions and retention of acid basesBuffered by H+ ions passing into cells in exchange for K+ ions (aggravating tendency to hyperkalaemia)Compensation mechanism – increasing CO2 loss through lungs – air hungerExacerbates anorexia and increases muscle catabolism

Implications Of Hyperkalaemia

Caused by failure of distal tubule to secrete potassiumExacerbated by acidosisCan cause cardiac arrhythmias and arrestClinical features of hyperkalaemia dependent on chronicity of hyperkalaemia

Kidney As A Metabolic Organ

Decreased erythropoietin production in renal failure results in anaemiaLow 1-25 Vit. D levels result in poor intestinal calcium absorption, hypocalcaemia (short term) and hyperparathyroidism (longer term)Increased cardiovascular risk

Major predictor of end stage kidney disease is chronic kidney diseaseMajor outcome for patient with chronic kidney disease is cardiovascular disease

Acute Loss Of Kidney Function

AnaemiaAcidosisTendency to hyperkalaemiaHypocalacemiaRenal size unchangedAcute metabolic complicationsTendency to hyponatraemiaVolume usually overloaded – oedema, hyptertensionPreviously normal creatinine

Chronic Loss Of Kidney Function

AnaemiaAcidosisTendency to hyperkalaemiaRenal osteodystrophyRenal size often reducedChronic uraemic symptomsTendency to hyponatraemiaVolume usually overloaded – oedema, hypertensionPreviously abnormal creatinine

Initial Management Of Patient

Patient has renal failure – lethargy and anorexia, hypotension, hyperkalaemia, hyponatraemia, metabolic acidosisIntravenous normal saline to correct fluid depletionIntravenous sodium bicarbonate to correct acidosisIntravenous insulin and dextrose to lower plasma potassium (by driving K+ back into cells)Transfer to hospital for dialysis

Assessing GFR

Urea – poor indicator, confounded by diet, catabolic state, GI bleeding, drugs, liver functionCreatinine – affected by muscle mass, age, race, sex, need to look at patient when interpreting resultCreatinine clearance – difficult for elderly patients to collect accurate sampleEstimated GFR – equation which automatically calculates GFR from serum creatinine, easiest equation uses age and ethnicity, alternatives can include weight, albumin, generally unreliable once GFR >60 ml/minInulin clearance – laborious, used for research purposes onlyRadionuclide studies – EDTA clearance, reliable but expensive

Stages Of CKD

Stage 1 – normal GFR (>90 ml/min/1.73m2), with other evidence of chronic kidney damage

Stage 2 – mild impairment, GFR 60-89 ml/min/1.73m2, with other evidence of chronic kidney damageStage 3 – moderate impairment, GFR 30-59 ml/min/1.73m2

Stage 4 – severe impairment, GFR 15-29 ml/min/1.73m2

Stage 5 – established renal failure, GFR <15 ml/min/1.73m2 or on dialysis

Long Term Management

Remains on regular haemodialysis for 4hrs 3 times/weekLow potassium diet and fluid restrictionErythropoietin injections to correct anaemia1.25 vitamin D supplements to prevent hyperparathyroid bone disease