Dialysis basics


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Basic facts about Hemodialysis Therapy

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Dialysis basics

  1. 1. Dialysis Basics Dr.Ashutosh OjhaMD,DNB(Gen Med)PDCC-Nephro (student) GMCH..Guwahati.
  2. 2. Outline Indications Modalities Apparatus Access Complications of dialysis access Acute complications of dialysis
  3. 3. Indications Pericarditis or pleuritis Progressive uremic encephalopathy or neuropathy ( asterixis, myoclonus, seizures) Bleeding diathesis Fluid overload unresponsive to diuretics Metabolic disturbances refractory to medical therapy (hyperkalemia, metabolic acidosis, hyper- calcemia , hyper- phosphatemia) Persistent nausea/vomiting, weight loss, or malnutrition Toxic overdose of a dialyzable drug….Dialysable substance IgG/>>>>IgM
  4. 4. Indications for RRT Acute management of life-threatening complications of AKI: A: Metabolic acidosis (pH less than 7.1) E: Electrolytes -- Hyperkalemia (K >6.5 meq/L) or rapidly rising K) I: Ingestion -- Certain alcohol and drug intoxications O: Refractory fluid overload U: Uremia, ie. pericarditis, neuropathy, decline in mental status
  5. 5. Goals of Dialysis  Solute clearance  Diffusive transport (based on countercurrent flow of blood and dialysate)  Convective transport (solvent drag with ultrafiltration)  Fluid removal
  6. 6. Modalities Peritoneal dialysis Intermittent hemodialysis Hemofiltration Continuous renal replacement therapy  Decision of modality determined by catabolic rate, hemodynamic stability, and whether primary goal is fluid or solute removal
  7. 7. Principles of dialysis Dialysis = diffusion = passive movement of solutes across a semi- permeable membrane down concentration gradient  Good for small molecules (Ultra)filtration = convection = solute + fluid removal across semi- permeable membrane down a pressure gradient (solvent drag)  Better for removal of fluid and medium- size molecules Faber. Nursing in Critical Care 2009; 14: 4
  8. 8. Principles of dialysis Hemodialysis = solute passively diffuses down concentration gradient  Dialysate flows countercurrent to blood flow.  Urea, creatinine, K move from blood to dialysate  Ca and bicarb move from dialysate to blood. Hemofiltration: uses hydrostatic pressure gradient to induce filtration / convection plasma water + solutes across membrane. Hemodiafiltration: combination of dialysis and filtration. •Millers Anesthesia, 7th ed. 2009 •Foot. Current Anaesthesia and Critical Care 2005; 16:321-329
  9. 9. Hemodialysis Apparatus Dialyzer (cellulose, substituted cellulose, synthetic noncellulose membranes) Dialysis solution (dialysate – water must remain free of Al, Cu, chloramine, bacteria, and endotoxin)ABDEC Tubing for transport of blood and dialysis solution Machine to power and mechanically monitor the procedure (includes air monitor, proportioning system, temperature sensor, urea sensor to calculate clearance)CAPUT
  10. 10. Hemodialysis Access Acute dialysis catheter (vascular catheter, i.e. Quentin catheter) Cuffed, tunneled dialysis catheter (Permcath) Arteriovenous graft Arteriovenous fistula
  11. 11. Arteriovenous Fistula Preferred form of dialysis access Typically end-to-side vein-to-artery anastamosis Types  Radiocephalic (first choice)  Brachiocephalic (second choice)  Brachiobasilic (third choice, requires superficialization of basilic vein, i.e. transposition) Lower extremity fistulae are rare
  12. 12. Radiocephalic AVF
  13. 13. Brachiocephalic AVF
  14. 14. Arteriovenous Graft Synthetic conduit, usually polytetrafluoroethylene (PTFE, aka Gortex), between an artery and a vein Either straight or looped Common sites  Straight forearm : Radial artery to cephalic vein  Looped forearm : brachial artery to cephalic vein  Straight upper arm : brachial artery to axillary vein  Looped upper arm : axillary artery to axillary vein
  15. 15. Arteriovenous Graft cont’d Rare sites  Leg grafts  Looped chest grafts  Axillary-axillary (necklace)  Axillary-atrial grafts
  16. 16. Arteriovenous Graft
  17. 17. Tunneled Cuffed Catheters Dual lumen catheters Most commonly placed in the internal jugular vein, exiting at the upper, anterior chest Can also be placed in the femoral vein Subclavian catheters should be avoided given the risk of subclavian stenosis
  18. 18. Cuffed Dialysis Catheter
  19. 19. Dialysis Access : Time to use Graft  Usually cannulated within weeks  Vectra or flexine grafts can safely be cannulated after ~12 hours Fistula  Median period of 100 days before cannulation in the U.S. and U.K.  Initial cannulation should be performed with small gauge needles and low blood flow  Needles Chart for home care Dialysis
  20. 20. Dialysis Access : Longevity Native fistulas have a high rate of primary failure, but long- term patency is superior to grafts if they mature R-C fistulas 5- and 10-year patency are 53 and 45%, respectively PTFE grafts 1-, 2-, and 4-year patency are 67, 50, and 43%, respectively
  21. 21. Complications of AVF and AVG Thrombosis Infection (10% for AVG, 5% for transposed AVF, 2% for non- transposed AVF) Seromas Steal (6% of B-C AVF, 1% of R-C AVF) Aneurysms and pseudoaneurysms (3% of AVF, 5% of AVG) Venous hypertension (usually 2/2 central venous stenosis) Heart failure (Avoid AVFs in pts with severely depressed LVEF) Local bleeding
  22. 22. Tunnel Cuffed Catheters Indications  Intermediate-duration vascular access during maturation of AVF or AVG  Expected lifespan on dialysis of < 1 year (due to co-morbidities or on living donor transplant list)  Medical contra-indication to permanent dialysis access (severe heart failure)  Patients who refuse AVF or AVG after explanation of the risks of a catheter  All other dialysis access options have been exhausted
  23. 23. Tunnel Cuffed Catheters :Complications Infection  Risk of bacteremia 2.3 per 1000 catheter days or 20 to 25% over the average duration of use Dysfunction  Defined as inability to sustain blood flow of >300 mL/min  By this definition, 87% of catheters malfunction in their lifetime Central venous stenosis Mortality (may be influenced by selection bias)
  24. 24. Tunnel Cuffed Catheters : Bacteremia Metastatic infections  Osteomyelitis, endocarditis, septic arthritis, suppurative thrombophlebitis, or epidural abscess Risk factors : prolonged duration of usage, previous bacteremia, recent surgery, diabetes mellitus, iron overload, immunosuppression, malnutrition
  25. 25. Tunnel Cuffed Catheters : Bacteremia Microbiology  Coagulase-negative staph and S. aureus together account for 40 to 80%  Significant morbidity and mortality with S. aureus, esp. MRSA  Nonstaphylococcal infections predominantly due to enterococci and Gram negative rods (30-40%)  If HIV positive, consider polymicrobial and fungal infections
  26. 26. Tunnel Cuffed Catheters : Bacteremia Clinical manifestations  Fevers or chills in catheter-dependent dialysis patients associated with positive blood cultures in 60 to 80%  Less commonly : hypotension, altered mental status, catheter dysfunction, hypothermia, and acidosis
  27. 27. Tunnel Cuffed Catheters : Bacteremia Empiric Treatment  Vancomycin (load with 15-20 mg/kg and then 500-1000 mg after each HD session) plus either gentamicin (load with 2 mg/kg and then 1 mg/kg after each HD session) or ceftazidime (2 grams after each HD session)  Avoid prolonged use of an aminoglycoside given the risk of ototoxicity with vestibular dysfunction
  28. 28. Tunnel Cuffed Catheters : Bacteremia Tailored treatment  MRSA : vancomycin, daptomycin if vancomycin allergy  MSSA : cefazolin (Ancef)  VRE : daptomycin  Gram-negative organisms : ceftazidime, levaquin  Candidemia : immediate catheter removal, Infectious disease consultation for appropriate anti-fungal agent (ex., micafungin)
  29. 29. Tunnel Cuffed Catheters : Bacteremia Duration  Catheter removal and replacement, early resolution of symptoms, blood cultures quickly negative : 2 to 3 weeks  Uncomplicated S. aureus infection : 4 weeks  Metastatic infection or persistently positive blood cultures : minimum 6 weeks  Osteomyelitis : 6 to 8 weeks
  30. 30. Tunnel Cuffed Catheters : Bacteremia Catheter management  Immediate removal if severe sepsis, hypotension, endocarditis or metastatic infection, persistent bacteremia (usually defined as >72 hrs), tunnel site infection  Consider removal if S. aureus, P. aeruginosa, fungi, or mycobacteria  Consider salvage if coagulase negative staphylococcus (may be a risk factor for recurrence)
  31. 31. Tunnel Cuffed Catheters : Bacteremia Catheter management  Guidewire exchange  Not well studied (small, uncontrolled studies)  Theoretically, useful for preservation of vasculature  May be indicated if coagulopathy or hemodynamic instability precludes catheter removal and temporary catheter placement  Catheter tip should be sent for culture, and if positive, new catheter should be relocated to a new site
  32. 32. Acute Complications of Dialysis Hypotension (25-55%) Cramps (5-20%) Nausea and vomiting (5-15%) Headache (5%) Chest pain (2-5%) Back pain (2-5%) Itching (5%) Fever and chills (<1%)
  33. 33. Acute Complications of Dialysis Chest pain  Can be associated with hypotension and dialysis disequilibrium syndrome  Always consider angina, hemolysis, and (rarely) air embolism  Consider pulmonary embolism if recent manipulation of thrombus and/or occlusion of the dialysis access
  34. 34. Acute Complications of Dialysis Hemolysis  Suggestive findings include port wine appearance of the blood in the venous line, a falling hematocrit, or complaints of chest pain, SOB, and/or back pain  Usually due to dialysis solution problems, including overheating, hypotonicity, and contamination with formaldehyde, bleach, chloramine, or nitrates in the water, or copper in the dialysis tubing  Treatment includes discontinuation of dialysis without blood return to the patient, and evaluation for hyperkalemia with medical treatment as necessary
  35. 35. Acute Complications of Dialysis Arrhythmias  Common during, and between, dialysis treatments  Controversial whether due to disturbances in plasma potassium  Treatment is similar to the non-dialysis population, except for medication dosing adjustments
  36. 36. Thank you Blood and Dialysate have to run opposite to achieve optimum clearance …..Fluid and Solute Learning is always unidirectional …..Institute to Individual.