* It is proportionate to body size and the reference value is usually expressed after correction for body surface area as 120 ± 25 ml/min/1.

Transcription

1 Ahmad Al-zoubi Glomerular filtration rate : is the sum of the ultrafiltration rates from plasma into the Bowman s space in each nephron and is a measure of renal excretory function *co : 6L *renal blood flow = 20% co = 1.2 *plasma 50 % of blood = 600 ml * filtration fracion is 20% = 120 ml * It is proportionate to body size and the reference value is usually expressed after correction for body surface area as 120 ± 25 ml/min/1.73 m2 How to estimate glomerular filtration rate (GFR) * estimation?? reflect what? it s a rough measure of the number of functioning nephron reflect how much the damage 1-Direct measurement A) using labelled ethylenediamine-tetra-acetic acid (EDTA) or inulin *note :1- which are completely filtered at the glomerulus and are not secreted or reabsorbed by the renal tubules 2-This is not performed routinely, however, and is usually reserved for special circumstances, such as the assessment of renal function in potential live kidney donors

2 B) Creatinine clearance (CrCl): CrCl (ml/min) = urine creatinine concentration (mol/l)* volume (ml) / plasma creatinine concentration (mol/l) *time (min) *note : Needs 24-hr urine collection (inconvenient and often unreliable) creatinine characteristic : * reabsorption * secretion * drugs effect *Serum creatinine and the glomerular filtration rate (GFR) relationship 2- Estimating GFR with equations A) The Modification of Diet in Renal Disease (MDRD) study equation B) The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation

3 ** The equation does not require weight or height variables because the results are reported normalized to 1.73 m 2 body surface area, which is an accepted average adult surface area. Limitations of estimated glomerular filtration rate (egfr)?? **derived from population-based study ** Assessing GFRs above 60 ml/min/1.73 m 2 which equation to use?? ** Patients under the age of 18??? The Bedside Schwartz equation * Stages of chronic kidney disease (CKD) 5 stages Two GFR values 3 months apart are required to assign a stage. All GFR values are in ml/ min/1.73 m2 chronic kidney disease (CKD): ) refers to an irreversible deterioration in renal function definition :1-2- Common causes of chronic kidney disease?? 1-Diabetic nephropathy most important cause of endstage renal disease (ESRD) a. Pathologic types?

4 Nodular glomerular sclerosis (Kimmelstiel Wilson syndrome) hyaline deposition in one area of glomerulus pathognomonic for DM Diffuse glomerular sclerosis hyaline deposition is global also occurs in HTN Isolated glomerular basement membrane thickening b. Microalbuminuria(Definition of Microalbuminuria 30 to 300 mg/day Albumin creatinine ratio of 0.02 to 0.20)/proteinuria * the effect of Hypertention and glycemic control? Persistent HTN and proteinuria cause a decrease in glomerular filtration rate (GFR), leading to renal insufficiency and eventually ESRD. screening test?? Microalbuminuria/dipstick for urine 2-Interstitial diseases 3-Glomerular diseases 10 20%?? 4-Hypertension 5-Systemic inflammatory diseases 6-Renovascular disease 7-Congenital and inherited Alport syndrome?? GBM renal biopsy in late stage?? Clinical features: mainly due to uremia and fluid over load 1. Cardiovascular a. HTN the most common cause of secondary HTN. b. CHF c. Pericarditis (uremic) 2. GI 3.Neurologic due to hypocalcemia( tetany and confusion) sign?? and uremia ->confusion, peripheral neuropathy, and uremic seizures.

5 Physical findings?? restless legs?? 4. Hematologic anemia type? Causes of anaemia in chronic kidney disease?? Deficiency of erythropoietin Toxic effects of uraemia on marrow precursor cells Reduced red cell survival Blood loss due to capillary fragility and poor platelet function Reduced intake, absorption and utilisation of dietary iron haemodialysis as a result of haemolysis in the dialysis circuit increase risk of bleeding? 5. Endocrine/metabolic A) Calcium disturbances two primary factors?? The FGF23 and PTH / reduced 1,25-dihydroxyvitamin D effects?? renal osteodystrophy( osteitis fibrosa cystica/osteomalacia, and Osteoporosis)/ (adynamic bone disease)?? **tertiary hyperparathyroidism calcium and phosphate deposition vascular calcifications /calciphylaxis? painful syndrome of calcification of the small blood vessels located within the fatty tissue and deeper layers of the skin, blood clots, and the death of skin cells due to too little blood flow./ Calcification of the media of blood vessels, heart valves, myocardium and the conduction system of the heart is also common and may be due, in part, to the high serum phosphate levels b. Sexual/reproductive symptoms due to hypothalamic-pituitary disturbances and gonadal response to sex hormones: in men, decreased testosterone; in women, amenorrhea, infertility, and hyperprolactinemia. c. Pruritus (multifactorial etiology) common and difficult to treat. Dialysis and ultraviolet light 6. Fluid and electrolyte problems a. Volume overload watch for pulmonary edema. b. Hyperkalemia due to decreased urinary secretion. c. Hypermagnesemia occurs secondary to reduced urinary loss. e. Metabolic acidosis due to loss of renal mass (and thus decreased

6 ammonia production) and the kidney s inability to excrete H 7. Immunologic Suggested investigations in chronic kidney disease Urea and creatinine Urinalysis and quantification of proteinuria Electrolytes Calcium, phosphate, parathyroid hormone and 25(OH)D Albumin Full blood count (± Fe, ferritin, folate, B12) Lipids, glucose ± HbA1c Renal ultrasound evaluate size? /rule out obstruction Hepatitis and HIV serology management The aims of management in CKD are to: monitor renal function change in GFR prevent or slow further renal damage limit complications of renal failure treat risk factors for cardiovascular disease prepare for RRT, if appropriate Dialysis: the blood interfaces with an artificial solution resembling human

7 plasma (called the dialysate), and diffusion of fluid and solutes occurs across a semipermeable membrane. The two major methods of dialyzing a patient are hemodialysis and peritoneal dialysis *indications for dialysis: 1. Nonemergent indications: a. Cr and BUN levels are not absolute indications for dialysis b. Symptoms of uremia Nausea and vomiting Lethargy/deterioration in mental status, encephalopathy, seizures Pericarditis 2. Emergent indications (usually in the setting of renal failure) a. Life-threatening manifestations of volume overload Pulmonary edema Hypertensive emergency refractory to antihypertensive agents b. Severe, refractory electrolyte disturbances, for example, hyperkalemia, hypermagnesemia c. Severe metabolic acidosis d. Drug toxicity/ingestions (particularly in patients with renal failure): methanol, ethylene glycol, lithium, aspirin Absolute Indications for Dialysis Acidosis significant, intractable metabolic acidosis Electrolytes severe, persistent hyperkalemia Intoxications methanol, ethylene glycol, lithium, aspirin Overload hypervolemia not managed by other means Uremia (severe) based on clinical presentation, not laboratory

8 values (e.g., uremic pericarditis is an absolute indication for dialysis) Dialyzable Substances Salicylic acid Lithium Ethylene glycol Magnesiumcontaining laxatives Hemodialysis 1. Process a. The patient s blood is pumped by an artificial pump outside of the body through the dialyzer, which typically consists of fine capillary networks of semipermeable membranes.the dialysate flows on the outside of these networks, and fluid and solutes diffuse across the membrane. b. The patient s blood must be heparinized to prevent clotting in the dialyzer. 2. Frequency: Most hemodialysis patients require 3 to 5 hours of dialysis 3 days per week. 3. Access a. the central catheter most often in the subclavian or jugular vein for temporary access. b. Tunneled catheters are placed under the skin which leads to a lower rate of infection. These catheters are often suitable for use up to 6 months. c. Arteriovenous fistula* An audible bruit over the fistula indicates that it is

9 patent. **. Advantages of hemodialysis. a. It is more efficient than peritoneal dialysis. High flow rates and efficient dialyzers shorten the period of time required for dialysis. b. It can be initiated more quickly than peritoneal dialysis, using temporary vascular access in the emergent setting. ** Disadvantages of hemodialysis. a. It is less similar to the physiology of natural kidney function than is peritoneal dialysis, predisposing the patient to the following: Hypotension due to rapid removal of intravascular volume leading to

10 rapid fluid shifts from the extravascular space into cells. Hypo-osmolality due to solute removal. b. Requires vascular access. 2-Peritoneal dialysis 1. Process a. The peritoneum serves as the dialysis membrane. Dialysate fluid is infused into the peritoneal cavity, then fluids and solutes from the peritoneal capillaries diffuse into the dialysate fluid, which is drained from the abdomen. b. A hyperosmolar (high-glucose) solution is used, and water is removed from the blood via osmosis. 2. Frequency: dialysate fluid is drained and replaced every hour in acute peritoneal dialysis, but only once every 4 to 8 hours in CAPD. 3. Access a. With CAPD, dialysate is infused into the peritoneal fluid via an implanted catheter. b. A temporary catheter is used for acute peritoneal dialysis.. Advantages a. The patient can learn to perform dialysis on his or her own. b. It mimics the physiology of normal kidney function more closely than hemodialysis in that it is more continuous. 5. Disadvantages a. High glucose load may lead to hyperglycemia and hypertriglyceridemia. b. Peritonitis is a significant potential complication. c. The patients must be highly motivated to selfadminister it. d. Cosmetic there is increased abdominal girth due to dialysate fluid.

11 First-use syndrome : chest pain, back pain, and rarely, anaphylaxis may occur immediately after a patient uses a new dialysis machine

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