【持续性肾脏替代治疗crrt英文精品课件】renalreplacementtherapy(63p)

Renal Replacement Therapy,John Mc Donald Consultant Anaesthetist SGH,Criteria for diagnosis of acute renal failure,Fall in urine volume to less than 500 ml per day Rising plasma urea and creatinine concentrations Rising plasma potassium and phosphate plus falling calcium and venous bicarbonate,Investigations that may help to differentiate renal hypoperfusion from acute renal failure in oliguric patients,Relationship between Serum Creatinine and GFR,Measures for minimizing surgical acute renal failure,Optimizing volume status with correction of hypovolaemia by appropriate fluid administration guided by a CVP line, aiming for a CVP 10 cm of water and a urine output of 40 mL/minute Mean arterial pressure 80 mmHg, achieved and maintained by adequate volume replacement with or without inotropic support. Strategies to reduce the incidence of nosocomial infections, such as, the conservative use and rapid removal of intravascular and intravesical catheters. Cautious use of antibiotics. Sepsis needs to be aggressively investigated and treated. Restricted use and where possible the total avoidance of potentially nephrotoxic agents,Drugs that may cause acute interstitial nephritis in intensive care,Antibiotics lactams Rifampicin Sulphonamides Vancomycin Diuretics Thiazides Frusemide,Non-steroidal anti-inflammatory drugs Diclofenac Rofecoxib Others Ranitidine Cimetidine Phenytoin,Drugs that induce renal damage,Decrease in renal perfusion Diuretics, angiotensin converting enzyme inhibitors, blockers, vasodilators Impaired intra-renal haemodynamics Non-steroidal anti-inflammatories, radiocontrast agents Tubular toxicity Aminoglycosides, amphotericin, cisplatin Allergic interstitial nephritis lactams, non-steroidal anti-inflammatories,Guidelines for immediate management of patients with oliguria or anuria,Assess and correct any respiratory or circulatory impairment Manage any life threatening consequences of renal dysfunction (hyperkalaemia, salt and water overload, severe uraemia, extreme acidosis) Exclude obstruction of the urinary tract Establish underlying cause(s) and institute prompt remedial action Get a drug history and alter prescriptions appropriately Get help from senior appropriately trained specialists,The cause of acidosis will determine the treatment,Tissue hypoxia/lactic acidosis optimise circulation and oxygenation Salt and water depletion normal saline Established renal failure (acute or chronic) sodium bicarbonate, ?RRT Poisoning (methanol, ethylene glycol, salicylate) sodium bicarbonate, ?dialysis Diabetes mellitus insulin, saline,Indications for starting RRT,Oliguria Urine output 30 mmol/l and/or Creatinine 300 Hyperkalaemia K+ 6.5 mmols with renal impairment or failure to respond to resonium/ glucose insulin Volume overload Metabolic Acidosis,Indications II,Clinically significant organ dysfunction (especially pulmonary oedema) Ureamic encephalopathy Ureamic pericarditis Ureamic neuropathy/myopathy Severe dysnatremia (Na 160 mEq/L) Hyperthermia Drug overdose with dialyzable toxin,Indications III,Hypothermia for extracorporial warming Meningococcal Septicaemia (Based on a number of case reports) Severe Hypertension,Modes of RRT,Haemodialysis Haemofiltration Peritoneal dialysis,Haemodialysis,Fast efficient ideal for maintenance therapy in established CRF Prone to cause Haemodynamic Instability May cause Cerebral Oedema due to Fluid Shifts Need for Anticoagulation,Haemodialysis,The movement of solutes from a compartment in which they are in high concentration to one in which they are in lower concentration along an electrochemical gradient. An electrolyte solution runs countercurrent to blood flowing on the other side of a semipermeable (small pore) filter. Small molecules such as urea move along the concentration gradient into the dialysate fluid. Larger molecules are poorly removed by this process. Solute removal is directly proportional to the dialysate flow rate,Peritoneal Dialysis,Has the advantage of being simple and cost effective. No Extracorporeal circuit is needed which avoids the need for anticoagulation. The major disadvantages of PD are : poor solute clearance, poor uraemic control, risk of peritoneal infection and mechanical obstruction of pulmonary and cardiovascular performance. It is also unsuitable for patients who have undergone abdominal surgery,Haemofiltration,In the past Arterio-venous haemofiltration was used where the patients own heart pumped blood through the filter from an arterial cannula and returned to the patient via a venous canulae. The system worked but could be unreliable Recently machines which used 2 venous (or a single double lumen ) canulae and a mechanical pump have replaced this and Veno-venous haemofiltration now the treatment of choice in Intensive care units. Modern machines are largely automatic and can accurately monitor removal of effluent and administration of replacement fluid and heparin,ULTRAFILTRATION: The movement of fluid through a membrane caused by a pressure gradient.,Ultrafiltration,Haemofiltration,Solute is carried (in solution) a fluid across a semipermeable membrane in response to a transmembrane pressure gradient The rate of ultrafiltration depends upon the porosity of the membrane and the hydrostatic pressure of the blood, which depends upon blood flow. This is very effective in removal of fluid and middle-sized molecules, which are thought to cause uremia. Moreover, most of the cytokines involved in sepsis are “middle molecules”.,Continuous Veno-venous Haemofiltration,Blood is pumped through a semi-permiable membrane in the filter under pressure. Small and mid sized molecules such as water and urea are squeezed out and form the effluent. The haematocrit of fluid coming out of the filter is higher due to fluid loss. Replacement fluid is then added and the blood is returned to the patient.,Haemodialysis,Process uses dialysis there is a concentration gradient between plasma and the dialysis fluid and Urea and Creatinine move across the membrane The process is more efficient than filtration if Urea and Creatinine levels are high,Solute Clearance,Membrane,Blood,Dialysate/Ultrafitrate,Diffusive Solute Clearance,Membrane,Blood,Dialysate/Ultrafitrate,Diffusive Solute Clearance,Membrane,Blood,Dialysate/Ultrafitrate,HEMODIALYSIS Diffusion,HEMOFILTRATION : Convection,Haemodiafiltration,A mixture of filtration and dialysis The Prisma has to be set up for this mode when priming the filter,Prisma Haemodiafiltration,Advantages of using CRRT,Suitable for use in hemodynamically unstable patients. Precise volume control, which is immediately adaptable to changing circumstances. Very effective control of uremia, hypophosphatemia and hyperkalemia. Rapid control of metabolic acidosis Improved nutritional support (full protein diet). Available 24 hours a day with minimal training. Safer for patients with brain injuries and cardiovascular disorders (particularly diuretic resistant CCF). May have an effect as an adjuvant therapy in sepsis. Probable advantage in terms of renal recovery.,Disadvantages of using CRRT,Expense probably the same as IHD. Anticoagulation to prevent extracorporeal circuit from clotting. Complications of line insertion and sepsis. Risk of line disconnection. Hypothermia. Severe depletion of electrolytes and particularly K+ and PO4, where care is not taken,Setting up and using CRRT,The machine circuit is set up as follows: A double lumen catheter. A line leading to the filter where blood flow is controlled by a series of roller pumps: blood flow is usually set at 120ml/min. Anticoagulant to prevent blood clotting on the filter. A bag to collect the ultrafiltrate. Replacement fluid, to replace the excess ultrafiltrate over and above the required fluid removal.,Vascular Access,Large bore Double lumen catheter 150-250mm length Jugular, Femoral or Subclavian vein Use 150 RIJ, 200 LIJ, 200-250 Femoral,“Dose” of RRT,Clinical bottom line (level 1b) Critically-ill patients with acute renal failure who received continuous veno-venous haemofiltration at ultrafiltration rates of 35 or 45 mg/kg/hr compared with 20 mg/kg/hr were less likely to die (NN T = 6 at days) . There was no clear difference in mortality between the 35 and 45 mg/kg/hr groups. There was no clear difference in complications between the three groups. Ronco C, Bellomo R, Homel P, et al: effects of different doses in continuous veno-venous haemofiltration in outcomes of acute renal failure: a prospective randomised trial. Lancet 2000; 355 : 26-30,Anticoagulation for RRT,Unfractionated Heparin Low Molecular Weight Heparin Prostacycline Citrate Xigris None,Site of Action of Anticoagulants,Unfractionated Heparin,Cheap easy to monitor Usually 5000 units flushed through circuit 3-5,000 units given as a bolus then 1,000 units/hr adjusted to give an INR of around 2 Risk of bleeding and Thrombocytopoenia due to HIT and HAT Little if any relationship between INR and Filter Life,Low Molecular Weight Heparin,More expensive difficult to monitor effect Correct dosage to optimise filter life and reduce bleeding effects problematic Optimal dose varies depending on which LMW Heparin is used,Heparin Induced Thrombocytopoenia,HIT can be suspected when there is a decrease of at least 30% from the initial platelet count, usually commencing 4 to 14 days after institution of heparin. Thrombocytopenia may occur sooner if there has been previous exposure to the drug, including possible undocumented heparin flushes. The mean delay of HIT emergence is dramatically longer when LMWH are used compared with unfractionated heparin (mean delay of 28 vs 14 days). The platelet count declines below 100 109/L, often below 60 109/L, but bleeding is uncommon despite the severe thrombocytopenia. After heparin withdrawal, the platelet count usually rises to normal levels in 5 to 7 days. Thrombocytopenia recurs promptly on rechallenge with heparin.,Prostacycline,Expensive Antiplatelet drug used when there is significant risk of bleeding Can cause Hypotension Can be used with Heparin but problems with assessing dose Filter life may be shorter than that seen with Heparin,Citrate,Not widely used but may be more popular in future Causes anticoagulation by binding Calcium Can be used for regional anticoagulation citrate is infused before the filter and calcium after the filter to leave the patient with normal clotting,Xigris,Very Expensive anti-inflamatory drug with anticoagulant actions If patient is receiving a Xigris infusion no other anticoagulants are usually used because of risk of bleeding Stop Xigris for 2 hours before Surgery or Line Placement,No Anticoagulant,Used when serious clotting disturbances ie platelets 30,000 or seriously prolonged PT or APTT Used if the patient is uraemic with pericardial friction rub due to risk of cardiac tamponade Recent study suggested filter life could be comparable to using Heparin or LMWH,Monitoring RRT,8-12 Hourly U+E and Clotting more frequent if hyperkalaemic Check AGGs for H+, HC03 if bicarbonate levels fall and H+ levels rise during Haemofiltration the cause may be lactate intolerance Replacement fluid contains 25mm/l of Lactate which has to be metabolised to Bicarbonate. If this becomes a problem using a lactate free replacement fluid and infusing 25mmol per litre of replaced fluid as 8.4% sodium bicarbonate will usually correct the acidosis Failure to correct a metabolic acidosis with CRRT and Bicarbonate in a septic patient usually indicates on going shock and impending MSOF,Monitoring Urine output,If patient is producing some urine measure hourly volumes and adjust take off to achieve target fluid balance If patient is anuric remove catheter and leave out until urine flow resumes (leaving the catheter in with no urine is an infection risk,Key points,Circulation must be corrected before any other specific intervention is started The cause of renal dysfunction must be determined and if possible treated Renal replacement therapy should be started and tailored according to the degree of biochemical derangement and the patients underlying condition Primary renal disease is rare in critically ill patients but requires prompt referral to a nephrologist to avoid irreversible renal failure Drug therapy will need to be reviewed if Renal failure develops and RRT is instituted,SGH Guidelines for RRT,The basics Hourly exchange - should be weight adjusted and at least 35 ml/kg/hr as a standard. Blood pump speed is normally started at 100ml/hr. However, a higher speed may help reduce clotting and increase overall efficiency. If access pressures allow the speed can be increased. It can go as high as 180 ml/hr. Rate of fluid removal decide on this based on expected inputs, outputs, the patients overall fluid balance and how dry/wet you have decided to run the patient.,Type of replacement fluid,Generally you should use the lactate bags. If the lactate rises above 2-3 mmol/l or if there is clinical concern despite a lower lactate please change to bicarbonate buffered bags. Use a mix of K+ containing and K+ free bags to obtain the desired K+,Priming the circuit,The circuit is primed with 1 litre of 0.9% NaCl heparinised at a concentration of 5000 units/litre i.e. 5000 units heparin in total. In very high risk bleeding situations e.g. cerebral haemorrhage this fluid can then be flushed out with a further litre of heparin free 0.9% NaCl but this should rarely be required. The volume of the circuits 100ml + bonding of heparin means only a small dose of heparin is delivered to the patient by the prime.,How long should filters last,48 hours is very good 24 hours is acceptable 12 hours is problematic 6 hours is very poor Depending on the patients risk of bleeding one may decide to accept poor filter life if it means avoiding anticoagulation or over anticoagulation. In a patient with consistently short filter life who has had no bleeding complications on the initial starting protocol, where no access or other problems are identified, one may chose to aim for a higher APTT.,Blood testing,A baseline clotting screen and FBC should be sent. You do not necessarily need to delay getting the filter started by waiting on the results in most cases. Use your clinical judgement and make a best guess at where to start the heparin. All patients on unfractionated IV heparin should be Grouped and Saved.,Blood Testing,APTT should be checked 6 hours after starting the filter. Thereafter it should be checked 6 hours after any dose change. If a steady state is achieved interval of testing can be extended to 12 hourly. In rare cases of stability this can be extended to 24 hourly If the APTT is unstable or clinical circumstances dictate increase frequency of testing as required. The patients nurse should document lactate, K+ and haemoglobin from blood gases whenever an ABG is taken. If your patient is stable and has a well working filter; if you understand how RRT works and can prescribe replacement fluids properly you should not need to check formal U & Es more frequently than daily. Patient or biochemical or doctor! factors may mean this needs done more often.,Who and by how much to anticoagulate,This is a balance between prolonging circuit life and minimising the risk of bleeding. Doing this well is as much part of the art as the science of medicine. There is reasonable evidence that for every 10-second increase in APTT, the incidence of circuit clotting decreases by 25%, however, at the cost of a 50% increased risk of haemorrhage. With full anticoagulation in high-risk groups the incidence of significant haemorrhage can be as high as 50%.,Who and by how much to anticoagulate,The relationship between heparin dose, APTT and filter life suggests that, in the typical critically ill patient, as a starting point, an APTT between 35 and 45 sec APTTr 1.3 1.7 gives the best mix between safety and heparin therapy efficacy. Consideration of alteration of this target based on the life of the first couple of filters vs. patients risk of bleeding can be made thereafter. If the filters are clotting quickly one might cautiously aim for a higher target. If the filters are lasting well despite a low APTTr then one does not need to blindly chase a higher APTTr. Always consider access issues if clotting occurs frequently e.g. 2 sequential filters with less than 6 hour run time each. Is the line working well? Is the blood pump speed high enough?,Who and by how much to anticoagulate,In patients with a high risk of bleeding there is good evidence that around 50% - 60% can receive anticoagulant free RRT with acceptable filter life 24hrs. If patients are on Drotrecogin alpha Xigris and are receiving RRT they rarely need additional heparin to achieve acceptable filter life. The default position is no heparin whilst on Xigris. Platelet counts inevitably fall when on RRT. They fall further on anticoagulant free RRT c.f. than with the use of heparin. In a patient with thrombocytopenia e.g. from sepsis where one chooses to avoid heparin consideration can be given to the use of epoprostenol in a bid to prolong filter life and attenuate the anticipated fall in platelets c.f. heparin free RRT.,GROUP 1 - Patient at moderate risk of bleeding,Regard this as the standard option - the typical ITU RRT patient e.g. 1 Average 2 or more organ failures 4. Surgery 48 hours ago 2 No florid coagulopathy 5. No evidence of active bleeding 3 Platelets 50 6. No ureamic complications,GROUP 2 - Patients at low risk of bleedi