Dialysis Basics
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![Page 1: Dialysis Basics](https://reader035.fdocuments.in/reader035/viewer/2022081502/55cf9d4c550346d033ad06e2/html5/thumbnails/1.jpg)
Dr. Nirvan MukerjiSouthwest Atlanta Nephrology, P.C.
Dialysis Basics
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OutlineIndications ModalitiesApparatus AccessComplications of dialysis accessAcute complications of dialysisQuestions
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IndicationsPericarditis or pleuritisProgressive uremic encephalopathy or
neuropathy (AMS, asterixis, myoclonus, seizures)Bleeding diathesisFluid overload unresponsive to diureticsMetabolic disturbances refractory to medical
therapy (hyperkalemia, metabolic acidosis, hyper- or hypocalcemia, hyperphosphatemia)
Persistent nausea/vomiting, weight loss, or malnutrition
Toxic overdose of a dialyzable drug
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Goals of DialysisSolute clearance
Diffusive transport (based on countercurrent flow of blood and dialysate)
Convective transport (solvent drag with ultrafiltration)
Fluid removal
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ModalitiesPeritoneal dialysisIntermittent hemodialysisHemofiltrationContinuous renal replacement therapy
Decision of modality determined by catabolic rate, hemodynamic stability, and whether primary goal is fluid or solute removal
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Hemodialysis ApparatusDialyzer (cellulose, substituted cellulose,
synthetic noncellulose membranes)Dialysis solution (dialysate – water must
remain free of Al, Cu, chloramine, bacteria, and endotoxin)
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)
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Hemodialysis AccessAcute dialysis catheter (vascular catheter,
i.e. Quentin catheter)Cuffed, tunneled dialysis catheter
(Permcath)Arteriovenous graftArteriovenous fistula
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Arteriovenous FistulaPreferred form of dialysis accessTypically 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
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Radiocephalic AVF
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Brachiocephalic AVF
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Arteriovenous GraftSynthetic conduit, usually
polytetrafluoroethylene (PTFE, aka Gortex), between an artery and a vein
Either straight or loopedCommon sites
Straight forearm : Radial artery to cephalic veinLooped forearm : brachial artery to cephalic veinStraight upper arm : brachial artery to axillary
veinLooped upper arm : axillary artery to axillary vein
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Arteriovenous Graft cont’dRare sites
Leg graftsLooped chest graftsAxillary-axillary (necklace)Axillary-atrial grafts
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Arteriovenous Graft
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Tunneled Cuffed CathetersDual lumen cathetersMost commonly placed in the internal
jugular vein, exiting at the upper, anterior chest
Can also be placed in the femoral veinSubclavian catheters should be avoided
given the risk of subclavian stenosis
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Cuffed Dialysis Catheter
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Dialysis Access : Time to useGraft
Usually cannulated within weeksVectra or flexine grafts can safely be
cannulated after ~12 hoursFistula
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
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Dialysis Access : LongevityNative 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
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Complications of AVF and AVGThrombosisInfection (10% for AVG, 5% for transposed
AVF, 2% for non-transposed AVF)SeromasSteal (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
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Tunnel Cuffed CathetersIndications
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
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Tunnel Cuffed Catheters : ComplicationsInfection
Risk of bacteremia 2.3 per 1000 catheter days or 20 to 25% over the average duration of use
DysfunctionDefined as inability to sustain blood flow of >300
mL/minBy this definition, 87% of catheters malfunction in
their lifetime
Central venous stenosisMortality (may be influenced by selection bias)
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Tunnel Cuffed Catheters : BacteremiaMetastatic 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
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Tunnel Cuffed Catheters : BacteremiaMicrobiology
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
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Tunnel Cuffed Catheters : BacteremiaClinical 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
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Tunnel Cuffed Catheters : BacteremiaEmpiric 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
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Tunnel Cuffed Catheters : BacteremiaTailored treatment
MRSA : vancomycin, daptomycin if vancomycin allergy
MSSA : cefazolin (Ancef)VRE : daptomycinGram-negative organisms : ceftazidime,
levaquinCandidemia : immediate catheter removal,
Infectious disease consultation for appropriate anti-fungal agent (ex., micafungin)
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Tunnel Cuffed Catheters : BacteremiaDuration
Catheter removal and replacement, early resolution of symptoms, blood cultures quickly negative : 2 to 3 weeks
Uncomplicated S. aureus infection : 4 weeksMetastatic infection or persistently positive
blood cultures : minimum 6 weeksOsteomyelitis : 6 to 8 weeks
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Tunnel Cuffed Catheters : BacteremiaCatheter 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)
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Tunnel Cuffed Catheters : BacteremiaCatheter management
Guidewire exchange Not well studied (small, uncontrolled studies)Theoretically, useful for preservation of vasculatureMay 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
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Acute Complications of DialysisHypotension (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%)
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Acute Complications of DialysisChest 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
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Acute Complications of DialysisHemolysis
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
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Acute Complications of DialysisArrhythmias
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
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Questions