In hemodialysis, a patient’s blood is pumped into a dialyzer containing 2 fluid compartments configured as bundles of hollow fiber capillary tubes or as parallel, sandwiched sheets of semipermeable membranes. In either configuration, blood in the first compartment is pumped along 1 side of a semipermeable membrane while a crystalloid solution (dialysate) is pumped along the other side, in a separate compartment, in the opposite direction.- (See Overview of Kidney Replacement Therapy for other kidney replacement therapies [KRTs].)
Concentration gradients of solute between blood and dialysate lead to desired changes in the patient’s serum solutes, such as a reduction in urea nitrogen and creatinine; an increase in bicarbonate; and equilibration of sodium, chloride, potassium, and magnesium. The dialysate compartment is under negative pressure relative to the blood compartment and has a higher osmolality to prevent filtration of dialysate into the bloodstream and to remove the excess fluid from the patient. The dialyzed blood is then returned to the patient.
Hemodialysis
The patient is usually systemically anticoagulated during hemodialysis to prevent blood from clotting in the dialysis machine. However, hemodialysis treatment may also be performed with regional anticoagulation of the dialysis circuit (using heparin or trisodium citrate) or with saline flush, in which 50 to 100 mL of saline every 15 to 30 minutes clears the dialysis circuit of any blood clots.
Immediate objectives of hemodialysis are to:
Correct electrolyte and fluid imbalances
Remove toxins
Longer-term objectives in patients with kidney failure are to:
Optimize the patient’s functional status, comfort, and blood pressure
Prevent complications of uremia
Prolong survival
Bridge to transplant
Hemodialysis regimens
The optimal “dose” of hemodialysis is uncertain, but most patients do well with 3 to 5 hours of hemodialysis 3 times a week (1).
Hemodialysis dose can be increased by increasing time on dialysis, blood flow, membrane surface area, and membrane porosity.
In addition to the standard thrice weekly regimen, regimens that increase the total weekly dialysis dose include long nocturnal hemodialysis (generally 6 to 8 hours, 3 to 6 times per week), and short frequent hemodialysis (< 3 hours, 5 to 6 times per week). Long nocturnal and short frequent sessions, when available, are used selectively for patients who have any of the following (2):
Excessive fluid gain between dialysis sessions
Frequent hypotension during dialysis
Poorly controlled blood pressure
Hyperphosphatemia that is otherwise difficult to control
Evidence comparing the relative efficacy of frequent versus standard hemodialysis is mixed. Studies have shown clinical benefit for more frequent hemodialysis, but vascular access-related and other risks are increased (3, 4, 5). Frequent or daily sessions are most logistically and economically feasible if patients can do hemodialysis at home.
Assessing adequacy of hemodialysis
One way to assess the adequacy of each session is by measuring blood urea nitrogen (BUN) before and after each session. A ≥ 65% decrease of BUN from predialysis level ([predialysis BUN − postdialysis BUN]/predialysis BUN × 100% is ≥ 65%) can indicate an adequate session. Other, more calculation-intensive formulas, such as Kt/V ≥ 1.2 (where K is the urea clearance of the dialyzer in mL/minute, t is dialysis time in minutes, and V is volume of distribution of urea [which is about equal to total body water] in mL) (3), are less error-prone.
Hemodialysis setting
In-center hemodialysis is the most common type of hemodialysis in the United States (6). The main advantage of in-center hemodialysis is that the dialysis staff fully controls the dialysis treatment. The dialysis technician cannulates the fistula, decides how much fluid to remove, and does the entire dialysis treatment under the supervision of the dialysis nurse and the nephrologist.
In-center nocturnal hemodialysis is most suitable for patients who have high fluid gains, low blood pressure, or difficult-to-control phosphorus (2). It is also attractive for those who work during the day but who do not want to do home dialysis.
Home hemodialysis is as viable as in-center hemodialysis. Patients treated with home hemodialysis have longer survival and better control of hypertension (7), phosphorus and fluid levels, and better quality of life than those treated with in-center hemodialysis. Home hemodialysis is most commonly performed 4 to 7 days a week for about 2-3 hours per session. However, home hemodialysis can be performed on short frequent schedule, a standard 3-times-per-week daytime schedule, or on a nocturnal schedule. Most home hemodialysis programs require a care partner capable of helping in case help is needed. As with peritoneal dialysis, home hemodialysis requires more patient involvement than in-center hemodialysis.
Vascular access for dialysis
Surgically created arteriovenous fistula
Central venous catheter
Hemodialysis is usually done through a surgically created arteriovenous fistula.
Surgically created arteriovenous fistulas are better than central venous catheters because they are more durable and less likely to become infected (8). But they are also prone to complications (thrombosis, infection, aneurysm, or pseudoaneurysm). A newly created fistula may take 2 to 3 months to mature and become usable. However, additional time may be needed for fistula revision, so in patients with chronic kidney disease, the fistula is best created at least 6 months before the anticipated need for dialysis. The surgical procedure anastomoses the radial, brachial, or femoral artery to an adjacent vein in an end-of-the-vein to the side-of-the-artery fashion. When the adjacent vein is not suitable for access creation, a piece of prosthetic graft is used. For patients who have poor veins, an autogenous saphenous vein graft is also an option.
Percutaneous endovascular arteriovenous fistulas are also effective and safe, but they are less commonly used than surgically created arteriovenous fistulas (9, 10). Compared with surgically created arteriovenous fistulas, they may require additional procedures to ensure they mature and remain patent.
A central venous catheter can be used for dialysis if an arteriovenous fistula has not yet been created or is not ready for use or if creation of an arteriovenous fistula is impossible. The primary disadvantages of central venous catheters are a relatively narrow caliber that does not allow for blood flow high enough to achieve optimal clearance and a high risk of catheter-site infection and thrombosis. Central venous catheterization for hemodialysis is best done by using the right internal jugular vein (11). Most internal jugular vein catheters remain useful for 2 to 6 weeks if strict aseptic skin care is practiced and if the catheter is used only for hemodialysis. Catheters with a subcutaneous tunnel and fabric cuff have a longer life span and may be useful for patients in whom creation of an arteriovenous fistula is impossible.
Vascular access complications
Complications of vascular access include:
Infection
Stenosis
Thrombosis (often in a stenotic passage)
Aneurysm or pseudoaneurysm
These complications significantly limit the quality of hemodialysis that can be delivered, increase long-term morbidity and mortality, and are common enough that patients and practitioners should be vigilant for suggestive changes. These changes include pain, edema, erythema, breaks in the skin overlying the access, absence of bruit and pulse in the access, hematoma around the access, and prolonged bleeding from the dialysis cannula puncture site. Infection is treated with antibiotics, surgery, or both.
The fistula may be monitored for signs of impending failure by serial Doppler dilution blood flow measurements, thermal or urea dilution techniques, or by measurement of the static venous chamber pressures. Treatment of stenosis, thrombosis, pseudoaneurysm, or aneurysm may involve angioplasty, stenting, or surgery.
General references
1. Flythe JE, Watnick S. Dialysis for Chronic Kidney Failure: A Review. JAMA. 2024;332(18):1559-1573. doi:10.1001/jama.2024.16338
2. Copland M, Komenda P, Weinhandl ED, et al. Intensive hemodialysis, mineral and bone disorder, and phosphate binder use. Am J Kidney Dis. 2016;68(5S1):S24-S32. doi: 10.1053/j.ajkd.2016.05.024
3. National Kidney Foundation. KDOQI clinical practice guideline for hemodialysis adequacy: 2015 Update. Am J Kidney Dis. 2015;66(5):884-930, 2015. doi: 10.1053/j.ajkd.2015.07.015
4. FHN Trial Group, Chertow GM, Levin NW, et al. In-center hemodialysis six times per week versus three times per week. N Engl J Med. 2010;363(24):2287-2300. doi:10.1056/NEJMoa1001593
5. Natale P, Green SC, Rose M, et al. Frequent hemodialysis versus standard hemodialysis for people with kidney failure: Systematic review and meta-analysis of randomized controlled trials. PLoS One. 2024;19(9):e0309773. doi:10.1371/journal.pone.0309773
6. U.S. Renal Data System (USRDS), National Institute of Diabetes and Digestive and Kidney Diseases: End Stage Renal Disease. Accessed May 8, 2026.
7. Weinhandl ED, Liu J, Gilbertson DT, et al. Survival in daily home hemodialysis and matched thrice-weekly in-center hemodialysis patients. J Am Soc Nephrol. 2012;23(5):895-904. doi: 10.1681/ASN.2011080761
8. Fisher M, Golenstaneh L, Allon M. Prevention of bloodstream infections inpatients undergoing hemodialysis. Clin J Am Soc Nephrol. 2020;15(1):132-151. doi:10.2215/CJN.06820619
9. Bontinis A, Bontinis V, Koutsoumpelis A, et al. A systematic review aggregated data and individual participant data meta-analysis of percutaneous endovascular arteriovenous fistula. J Vasc Surg. 2023;77(4):1252-1261.e3. doi:10.1016/j.jvs.2022.10.039
10. Yan Wee IJ, Yap HY, Tang TY, Chong TT. A systematic review, meta-analysis, and meta-regression of the efficacy and safety of endovascular arteriovenous fistula creation. J Vasc Surg. 2020;71(1):309-317.e5. doi:10.1016/j.jvs.2019.07.057
11. Lok CE, Huber TS, Lee T, et al. KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update. Am J Kidney Dis. 2020;75(4 Suppl 2):S1-S164. doi:10.1053/j.ajkd.2019.12.001
Complications of Hemodialysis
Complications are listed in table .
The most common complication of dialysis is:
Hypotension
Hypotension occurs in 4 to 17% of treatments (1); it has multiple causes, including too-rapid water removal, osmotic fluid shifts across cell membranes, acetate in the dialysate, heat-related vasodilation, allergic reactions, sepsis, and underlying conditions (eg, autonomic neuropathy, cardiomyopathy with poor ejection fraction, myocardial ischemia, arrhythmias).
Other frequent complications include:
Cramps
Pruritus
Nausea and vomiting
Headache
Chest and back pain
In most cases, these complications occur for unknown reasons, but some may be part of a first-use syndrome (when the patient’s blood is exposed to residual ethylene oxide used to sterilize the dialyzer, or the membranes in the dialyzer) or dialysis dysequilibrium syndrome, a syndrome thought to be caused by too-rapid removal of urea and other osmolytes from the serum, causing osmotic movement of fluid into the brain. More severe cases of dialysis dysequilibrium manifest as disorientation, restlessness, blurred vision, confusion, seizures, and even death.
Dialysis-related amyloidosis affects some patients who have been on hemodialysis for years and manifests as carpal tunnel syndrome, bone cysts, arthritis, and cervical spondyloarthropathy (2). Dialysis-related amyloidosis decreased 10-fold from 1998 to 2018 because beta-2 microglobulin, the protein causing amyloidosis, is removed more effectively with current high-flux dialyzers (3).
Complications of Kidney Replacement Therapy
Type | Hemodialysis | Peritoneal Dialysis |
|---|---|---|
Cardiovascular | Air embolism Cardiac arrest (rare) | Arrhythmia Hypotension* Pulmonary edema |
Infectious | Colonization of temporary central venous catheters Exit-site infection of both tunneled and temporary central venous catheters Vascular access cellulitis or abscess | Catheter exit-site infection* |
Mechanical | Obstruction of the arteriovenous fistula due to thrombosis or infection Stenosis or thrombosis of the subclavian vein or superior vena cava due to recurrent use of subclavian and internal jugular vein catheters | Catheter obstruction by clots, fibrin, omentum, or fibrous encasement Dialysate leakage around the catheter Dissection of fluid into the abdominal wall Hematoma in the pericatheter tract Perforation of a viscus by the catheter |
Metabolic | Hypoglycemia in patients with diabetes who use insulin Iron loss | Hypoalbuminemia Hyperglycemia Hyperlipidemia Obesity |
Pulmonary | Dyspnea due to anaphylactic reaction to hemodialysis membrane Hypoxia when acetate buffered dialysate is used | |
Miscellaneous | Amyloid deposits Catheter-related hemorrhage Fever due to bacteremia, pyrogens, or overheated dialysate Hemorrhage (gastrointestinal, intracranial, retroperitoneal, intraocular) Insomnia Muscle cramps* Pruritus Restlessness Seizures | Abdominal and inguinal hernias Catheter-related intra-abdominal bleeding Hypothermia Peritoneal sclerosis Seizures |
* Most common complications overall. | ||
Complications references
1. Flythe JE, Watnick S. Dialysis for Chronic Kidney Failure: A Review. JAMA. 2024;332(18):1559-1573. doi:10.1001/jama.2024.16338
2. Danesh F, Ho LT. Dialysis-related amyloidosis: History and clinical manifestations. Semin Dial. 2001;14(2):80-85. doi: 10.1046/j.1525-139x.2001.00035.x
3. Kanda E, Muenz D, Bieber B, et al. Beta-2 microglobulin and all-cause mortality in the era of high-flux hemodialysis: results from the Dialysis Outcomes and Practice Patterns Study. Clin Kidney J. 2020;14(5):1436-1442. doi:10.1093/ckj/sfaa155
Prognosis for Hemodialysis
Overall adjusted annual mortality in hemodialysis-dependent patients is approximately 17% (1). The 5-year survival after hemodialysis initiation is approximately 40%, similar to that of patients receiving peritoneal dialysis (2). Death is generally mostly attributable to cardiovascular disease, followed by infection and withdrawal from hemodialysis. Nonhemodialysis contributors to mortality include comorbidities (eg, hyperparathyroidism, diabetes, undernutrition, other chronic disorders), older age, and late referral for dialysis.
Prognosis references
1. National Institutes of Health. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD). United States Renal Data System (USRDS). End Stage Renal Disease: Chapter 6. Mortality. 2025 Annual Data Report. Accessed May 21, 2026.
2. Flythe JE, Watnick S. Dialysis for Chronic Kidney Failure: A Review. JAMA. 2024;332(18):1559-1573. doi:10.1001/jama.2024.16338
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