Hemodialysis: Difference between revisions
| Line 22: | Line 22: | ||
==Vascular Access== | ==Vascular Access== | ||
The establishment and maintenance of reliable vascular access is crucial for long-term hemodialysis. Creating arteriovenous (AV) access by establishing arteriovenous fistula (AVF) is the most reliable vascular access. In the other hand, arteriovenous graft (AVG) may provide access in certain circumstances by placing a prosthetic or biograft. However, majority of patients need temporary access by tunneled catheters for initiating hemodialysis. Insertion of central catheter may cause complications, such as arterial and ventricular dysrhythmias, arterial puncture, hemothorax, pneumothorax, air embolism, perforation of central vein or cardiac chamber, and pericardial tamponade. Infection is another concern regarding catheter care. Migration of bacteria from patient's skin is the mechanism of catheter infection. Skin preparation before procedure by using chlorhexidine at the catheter exit site could prevent catheter infection. Staphylococcus epidermidis, is the most common isolate. Prompt catheter removal is recommended if evidences of site infection is present even in the absence of systemic signs. | The establishment and maintenance of reliable vascular access is crucial for long-term hemodialysis. Creating arteriovenous (AV) access by establishing arteriovenous fistula (AVF) is the most reliable vascular access. In the other hand, arteriovenous graft (AVG) may provide access in certain circumstances by placing a prosthetic or biograft. However, majority of patients need temporary access by tunneled catheters for initiating hemodialysis. Insertion of central catheter may cause complications, such as arterial and ventricular dysrhythmias, arterial puncture, hemothorax, pneumothorax, air embolism, perforation of central vein or cardiac chamber, and pericardial tamponade. | ||
* Infection is another concern regarding catheter care. Migration of bacteria from patient's skin is the mechanism of catheter infection. Skin preparation before procedure by using chlorhexidine at the catheter exit site could prevent catheter infection. Staphylococcus epidermidis, is the most common isolate. Prompt catheter removal is recommended if evidences of site infection is present even in the absence of systemic signs. | |||
* Catheter thrombosis may cause block blood flow is another aspect of catheter care. Instilling alteplase in the affected catheter lumen for 30 to 120 minutes is the prefered treatment. | |||
* Central vein stenosis | |||
==Anticoagulation== | ==Anticoagulation== | ||
Revision as of 16:12, 3 July 2018
|
Dialysis Main Page |
|
|---|
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2]
Overview
The goals of hemodialysis are removing toxins and aim to maintain euvolemia. Ninety three percent of ESRD patients in the United States and 89% worldwide, are under hemodialysis.[1] Solute diffusion across a membrane is the basic principle for hemodialysis. Metabolic waste products move across a semipermeable membrane depending on their concentration gradient between plasma and dialysate. Concentration gradient, membrane surface area, the membrane thickness, and size of solute molecule are important factors determining rate of diffusion. Small molecules clear more efficiently than larger molecules. Fluid removal is another advantage of hemodialysis that could be achieved by ultrafiltration. In-center hemodialysis and home hemodialysis are available for ESRD patients requiring renal replacement therapy; the choice of modality is based on patient condition, patient preference, and the availability of equipments.
Components
The Dialyzer
Dialyzer is usually made of bundles of hollow fibers permitting a high flow rate of blood and dialysate simultaneously. Parallel plates are another type of dialyzer that are barely used recently. Most of the dialyzers are synthetic with a variety of materials including polyamide, polyarylethersulfone, polyvinylpyrrolidone, polyacrylonitrile, and polysulfone. Biocompatible membranes have the advantage of not activating complement system.
The Dialysate
The dialysate is a paramount composition in hemodialysis. Solutes diffuse across the dialyzer between blood and dialysate. The dialysate composition should be individualized to restore plasma normal values. The main solutes in dialysate include sodium, potassium, calcium, magnesium, chloride, bicarbonate , and glucose. These electrolytes are treated with water during the process. About 100 liters of water is needed for each dialysis session. The water used for hemodialysis should be processed in order to have a balanced concentration of solutes. Also, contaminants including bacteria, viruses, and heavy metals, such as aluminium should be removed from water. This removal could be done either by using reverse osmosis or deionization. Filters may be used to improve water quality by removing particles. The dialyzate temperature could also be adjusted to cause vasoconstriction and improve patient's hemodynamic.
The choice of the dialysate is important to maintain or correct the electrolytes.
- Sodium: Usually, sodium concentration of 140-145 mEq/L is suitable for most of the patients but, it could be adjusted based on patient's sodium level.
- Potassium: The potassium concentration in dialysate solution depends on patient potassium level. For example: For patients with hyperkalemia, a potassium concentration of 2-3 mEq/L is appropriate and for patients with hypokalemia, a potassium concentration of 4 mEq/L is appropriate.
- Calcium: Dialysate concentration for calcium are available with 2.5 ,3, or 3.5 mEq/L. In most of the cases a 2.5 mEq/L solution which is equivalent to 5 mg/dl ionized calcium is used.
Blood Delivery System
The blood pump delivers blood from the arterial line to the dialyzer and then return it to the venous line. It's speed could be adjusted based on patient condition typically between 200 to 600 mL/min. This pump allows creating a transmembrane pressure in dialyzer by sucking dialysate. The dialysate flow rate is between 500 to 800 mL/min.
Vascular Access
The establishment and maintenance of reliable vascular access is crucial for long-term hemodialysis. Creating arteriovenous (AV) access by establishing arteriovenous fistula (AVF) is the most reliable vascular access. In the other hand, arteriovenous graft (AVG) may provide access in certain circumstances by placing a prosthetic or biograft. However, majority of patients need temporary access by tunneled catheters for initiating hemodialysis. Insertion of central catheter may cause complications, such as arterial and ventricular dysrhythmias, arterial puncture, hemothorax, pneumothorax, air embolism, perforation of central vein or cardiac chamber, and pericardial tamponade.
- Infection is another concern regarding catheter care. Migration of bacteria from patient's skin is the mechanism of catheter infection. Skin preparation before procedure by using chlorhexidine at the catheter exit site could prevent catheter infection. Staphylococcus epidermidis, is the most common isolate. Prompt catheter removal is recommended if evidences of site infection is present even in the absence of systemic signs.
- Catheter thrombosis may cause block blood flow is another aspect of catheter care. Instilling alteplase in the affected catheter lumen for 30 to 120 minutes is the prefered treatment.
- Central vein stenosis
Anticoagulation
Monitoring and Adequacy
References
- ↑ Collins AJ, Foley RN, Gilbertson DT, Chen SC (June 2015). "United States Renal Data System public health surveillance of chronic kidney disease and end-stage renal disease". Kidney Int Suppl (2011). 5 (1): 2–7. doi:10.1038/kisup.2015.2. PMC 4455192. PMID 26097778.