【持续性肾脏替代治疗crrt英文精品课件】introduction to hemodialysis (45p)

Introduction to hemodialysis,History of dialysis,1861 The process diffusion was first described by Thomas Graham (Glasgow) 1913 Artificial kidney developed - John Abel (Baltimore) 1924 First human dialysis - George Haas (Giessen),Vividiffusion machine from Abel,History of dialysis,1943 Rotating drum dialyzer Willem Kolff (Kampen) 1948 Kolff-Brigham machine. As used in the Korean war for acute renal failure,History of dialysis,1960 Scribner shunt (Seattle) 1966 Internal AV fistula developed - Brescia, Cimino (New York),Origins of chronic dialysis in the US,The first outpatient dialysis founded by Scribner in 1962 (Seattle Artificial Kidney Center) Immediately the problem arose of demand outstripping supply “Life or Death Committee” or “God Squad” evaluated the patients “worth” in the community and ultimately decided who got dialysis Considerations included health status, psychological ability to handle stress and financial resources,Origins of chronic dialysis in the US,1971: Shep Glazer dialyzed while testifying before the house ways and means committee Congress responded by passing the ESRD medicare program and president Nixon signed it into law in 1972 Since this time the number of ESRD pts has steadily grown and is now greater than 350,000 and costs more than 17 billion/yr,Types of extracorporeal therapies,Hemodialysis Transport process by which a solute passively diffuses down its concentration gradient from one fluid compartment (either blood or dialysate) into the other Hemofiltration Use of a hydrostatic pressure gradient to induce the filtration (or convection) of plasma water across the membrane of the hemofilter. Hemoperfusion Process whereby blood is passed through an adsorbent cartridge Theurapeutic apheresis Blood separator technology is used to remove abnormal blood cells and plasma consituents eg. Plasmapheresis, leukapheresis, erythrocytapheresis,Mechanisms of solute clearance,Diffusive transport Blood from the patient flowing within the dialysis apparatus interfacing with dialysate fluid via pores located within each fiber of the dialysis membrane Convective transport In this mechanism, solutes are effectively dragged along with fluid as it moves across the membrane depending upon their size relative to the size of the membrane pores.,Fluid removal,Occurs via a hydrostatic pressure gradient across the membrane which is generated by the dialysis machine. This transmembrane pressure (TMP) causes fluid to cross from the side of high pressure (blood compartment) to the side of low pressure (dialysate compartment),Contain thousands of hollow fibers similar in structure to a human capillary Types of membranes Cellulose Substituted cellulose Synthetic,Hollow fiber dialyzers,Types of vascular access,AV fistula AV graft Central venous catheters,AV fistula,Constructed with subcutaneous between an artery and vein (side of artery to side or end of vein) Advantages Excellent patency Lower rates of complications (infection, steal, stenosis) Disadvantages Long maturation time Occasional failure to develop,AV graft,Synthetic conduit, usually polytetrafluoroethylene (PTFE, also known as Gortex), between an artery and vein Advantages Short maturation time Easy cannulation and large surface area Easier surgical handling Disadvantages Inferior long term patency High infection rate than native AVF Good alternative in patients in whom adequate AVF cannot be created,Central venous catheters,Temporary catheters (Vascath) ARF requiring dialysis ESRD but without alternative access Tunneled cuffed catheters Alternative form of long term vascular access for patients in whom AV access cannot readily be created,Accepted indications for RRT in patients with AKI generally include:,Refractory fluid overload Hyperkalemia (plasma potassium concentration 6.5 meq/L) or rapidly rising potassium levels Metabolic acidosis (pH less than 7.1) Signs of uremia, such as pericarditis, neuropathy, or an otherwise unexplained decline in mental status Steadily worsening renal function Less common acute indications Drug intoxication Hypothermia Hypercalcemia,Uremia: Greek for “urine in blood”,Clinical indications to start dialysis in CKD,Pericarditis or pleuritis Progressive uremic encephalopathy or neuropathy, with signs such as confusion, asterixis, myoclonus, wrist or foot drop, or, in severe cases, seizures A clinically significant bleeding diathesis attributable to uremia Fluid overload refractory to diuretics Persistent metabolic disturbances that are refractory to medical therapy; these include hyperkalemia, metabolic acidosis, hypercalcemia, and hyperphosphatemia Persistent nausea and vomiting Hypertension poorly responsive to antihypertensive medications Weight loss or signs of malnutrition,Possible Indications For Early Dialysis,Most nephrologists agree that delaying initiation of dialysis until one or more of these complications is present may put the patient at unnecessary jeopardy An important goal of dialysis is to enhance the quality of life as well as to prolong survival It is therefore important to consider less acute indications for dialysis Estimation of GFR (15 ml/min) Nutritional status,Complications during dialysis,Common,Hypotension (20-50%) Muscle cramps (5-20%) Nausea (5-15%) Headache (5%) Itching (5%) Chest pain/back pain (2-5%) Fever and chills (1%),Less common but serious,Dialysis disequilibrium Arrhythmias Cardiac tamponade Intracranial bleeding Hemolysis Air embolism,Intradialytic hypotension,There are two clinical patterns of dialysis-associated hypotension Episodic hypotension, which typically occurs during the latter stages of dialysis; this is associated with vomiting, muscle cramps, and other vagal symptoms (such as yawning). Chronic persistent hypotension, which may occur in long-term patients in whom predialysis systolic blood pressures of less than 100 mmHg are frequently observed.,Management of intradialytic hypotension,Trendelenberg position Bolus of 0.9% saline Shut off ultrafiltration Albumin, mannitol, hypertonic saline can be used as an alternative,Dialysis disequilibrium syndrome,Neurologic symptoms of varying severity that are thought to be due primarily to cerebral edema Reverse osmotic shift Intracerebral acidosis and idiogenic osmoles Early findings Headache, nausea, disorientation, restlessness, blurred vision, and asterixis Late findings Confusion, seizures, coma, and even death Prevention The initial dialysis should be gentle, but repeated frequently The aim is a gradual reduction in BUN,Serious complications of dialysis (continued),Arrhythmias Especially common in pts on Digoxin Intracranial bleeding Underlying cerebrovascular disease combined with the use of heparin Hemolysis Port wine appearance to blood in return lines Sudden back/chest pain, SOB Associated with obstruction of blood line and problems with the dialysis solutions Air embolism Enters cerebral venous system in seated patients Enters right ventricle in recumbent patients,Continuous renal replacement therapies,CRRT is generally better tolerated than conventional therapy, since many of the complications of intermittent hemodialysis are related to the rapid rate of solute and fluid loss CRRT involves either Dialysis (diffusion-based solute removal) or Filtration (convection-based solute and water removal) treatments that operate in a continuous mode,Continuous renal replacement therapies,Continuous venovenous hemofiltration (CVVH) Dialysis solution is not used, instead large volumes of replacement fluids are given Continuous venovenous hemodialysis (CVVHD) Dialysate is passed through at a slow rate continuously Continuous venovenous hemodiafiltration (CVVHDF) Combination; both dialysate and replacement fluids are used Slow continuous ultrafiltration (SCUF) Sustained low efficiency or extended daily dialysis (SLED),Advantages of CRRT,In addition to better control of azotemia, fluids and hemodyanmic stability ? Enhanced clearance of inflammatory mediators, which may provide benefit in septic patients, particularly using convective modes of continuous therapy. ? Among patients with acute brain injury or fulminant hepatic failure, continuous therapy may be associated with better preservation of cerebral perfusion.,Caveats to CRRT,No evidence from randomized trials to support survival advantage Risk of complications related to anticoagulation is higher Training and equipment costs,Drugs in renal failure,The kidney is the most important organ for