# Student Guide to Hemodialysis and Peritoneal Dialysis

> **📚 Educational Pathway:** Nephrology Reference Guide • Hyponatremia Guide • Kidney Biopsy Guide
>
> **🔗 Related Clinical Topics:** AKI Management • Cardiorenal Disease • CKD Management
>
> **🎯 Quality & Projects:** AKI Quality Initiative • Cardiorenal Research • Clinical Reports
>
> **🔧 Technical Support:** Medical AI Tools • Clinical Templates • AI in Healthcare

## Introduction

> **🔗 Clinical Connections:** AKI Workup, CKD Progression, Hyperkalemia, Hyponatremia, Heart Failure

Dialysis serves as renal replacement therapy for patients with end-stage renal disease or acute kidney injury. Two primary modalities exist: hemodialysis and peritoneal dialysis. Both utilize principles of diffusion, convection, and ultrafiltration to remove uremic toxins, excess fluid, and correct electrolyte imbalances including hyperkalemia and hyponatremia that the failing kidneys cannot manage.

## Fundamental Principles of Dialysis

### Diffusion and Clearance

Clearance represents the volume of plasma completely cleared of a substance per unit time, typically expressed in milliliters per minute. This concept forms the foundation for understanding dialysis efficiency. Clearance depends on the concentration gradient between blood and dialysate, membrane permeability, and surface area available for exchange.

The clearance formula demonstrates this relationship: Clearance = (Dialysate flow rate × Extraction ratio). The extraction ratio represents the fraction of substance removed from blood as it passes through the dialyzer, calculated as (Cin - Cout)/Cin, where Cin is inlet concentration and Cout is outlet concentration.

### Factors Affecting Clearance

#### Blood Flow Rate

Higher blood flow rates increase clearance for small solutes by maintaining concentration gradients and reducing recirculation of partially cleared blood. Typical blood flow rates range from 300-450 mL/min in hemodialysis. However, the relationship between blood flow and clearance follows a curvilinear pattern, with diminishing returns at higher flow rates due to membrane limitations.

#### Dialysate Flow Rate

Increased dialysate flow maintains steeper concentration gradients by continuously removing solutes from the dialysate side of the membrane. Standard dialysate flow rates of 500-800 mL/min optimize clearance while balancing efficiency with resource utilization. The counter-current flow pattern maximizes concentration gradients throughout the dialyzer length.

#### Filter Size and Surface Area

Larger dialyzers with increased membrane surface area provide more sites for solute exchange, directly correlating with improved clearance. Surface areas typically range from 1.0-2.5 square meters. The membrane composition also influences permeability characteristics, with synthetic high-flux membranes offering superior clearance compared to conventional low-flux membranes.

#### Treatment Time

Extended treatment duration allows more complete equilibration between blood and dialysate compartments, particularly benefiting larger molecule clearance. The relationship between time and solute removal follows first-order kinetics, where the rate of removal decreases as plasma concentrations decline.

## Dialysis Adequacy Measures

### KT/V Ratio

KT/V represents the most widely used measure of dialysis adequacy, where K equals dialyzer clearance, T represents treatment time, and V indicates the patient’s urea distribution volume. This dimensionless parameter quantifies the fractional clearance of body water during a single treatment session.

The target KT/V for hemodialysis patients typically exceeds 1.2 per session, achieved through optimization of blood flow, dialysate flow, membrane surface area, and treatment duration.^([1](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-1),[2](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-2),[3](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-3)) Higher KT/V values correlate with improved patient outcomes, including reduced mortality and morbidity — though the HEMO trial found no additional mortality benefit beyond standard-dose Kt/V of 1.25.^([4](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-4))

### Urea Reduction Ratio (URR)

URR measures the percentage reduction in blood urea nitrogen concentration during dialysis, calculated as \[(Pre-BUN - Post-BUN)/Pre-BUN\] × 100. Target URR values exceed 65%, with higher percentages indicating more effective treatment. URR provides a simpler calculation than KT/V but offers similar clinical utility for monitoring adequacy.

## Membrane Characteristics and Molecular Clearance

### Pore Size and Molecular Weight Relationship

Dialysis membrane pore size determines which molecules can traverse the membrane barrier. Small pores primarily allow passage of small molecules, while larger pores accommodate middle molecules and even some proteins. This selectivity explains differential clearance patterns for various uremic toxins.

### Urea versus Creatinine Clearance

Blood urea nitrogen (BUN) clearance exceeds creatinine clearance due to molecular size differences. Urea (molecular weight 60 daltons) passes freely through membrane pores, while creatinine (113 daltons) encounters more resistance. Additionally, urea demonstrates greater membrane permeability due to its smaller size and neutral charge characteristics.

This difference becomes clinically relevant when assessing dialysis adequacy, as BUN reduction may appear adequate while creatinine clearance remains suboptimal. High-flux membranes partially address this discrepancy by providing larger pore sizes that improve creatinine removal.

### Middle Molecule Clearance

#### Beta-2 Microglobulin

Beta-2 microglobulin (11,800 daltons) represents the prototype middle molecule. Conventional low-flux dialysis provides minimal clearance, leading to accumulation and dialysis-related amyloidosis. High-flux dialysis and hemodiafiltration significantly improve beta-2 microglobulin removal, reducing long-term complications in chronic dialysis patients.^([5](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-5),[6](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-6),[7](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-7))

#### Vancomycin Clearance

Vancomycin (1,449 daltons) demonstrates intermediate clearance properties. High-flux dialysis removes approximately 30-50% during a standard session, necessitating post-dialysis dosing adjustments. The drug’s protein binding and distribution characteristics further complicate dosing strategies in dialysis patients.

#### Phosphate Clearance

Phosphate clearance presents unique challenges due to its distribution kinetics. While dialysis effectively removes phosphate from the plasma compartment, rapid redistribution from intracellular and bone stores leads to rebound hyperphosphatemia. Extended dialysis times and frequent sessions improve phosphate control by allowing more complete equilibration between compartments.

## Hemodialysis Vascular Access

### Arteriovenous Fistulas

Arteriovenous fistulas represent the gold standard for permanent hemodialysis access. Surgical creation of a direct connection between an artery and vein, typically in the forearm or upper arm, allows vessel maturation and development of adequate flow rates for dialysis.

Benefits include lower infection rates, superior longevity, and reduced thrombosis compared to other access types.^([8](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-8),[9](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-9)) Complications may include steal syndrome, aneurysm formation, and stenosis requiring intervention. Fistula maturation requires 6-12 weeks, necessitating advance planning before dialysis initiation — and clopidogrel reduces early thrombosis but does not improve clinical maturation.^([10](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-10))

### Arteriovenous Grafts

Synthetic grafts connect arteries to veins using prosthetic materials, typically polytetrafluoroethylene (PTFE). Grafts can be used sooner than fistulas, usually within 2-4 weeks of placement, making them suitable when immediate access is needed.

However, grafts demonstrate higher infection rates, increased thrombosis risk, and shorter functional lifespan compared to fistulas. The synthetic material provides a nidus for bacterial colonization and may trigger inflammatory responses leading to stenosis.

### Central Venous Catheters (Permcaths)

Tunneled central venous catheters provide immediate dialysis access when permanent access is unavailable or maturing. These devices consist of dual lumens allowing simultaneous blood withdrawal and return, with a subcutaneous tunnel reducing infection risk.

Complications include catheter-related bloodstream infections, thrombosis, central venous stenosis, and mechanical dysfunction. Despite these risks, catheters serve essential roles in acute dialysis situations and as bridge therapy while permanent access develops.

## Vascular Access Complications

### Steal Syndrome

Steal syndrome occurs when arteriovenous access diverts excessive blood flow away from the distal extremity, causing ischemic symptoms. The low-resistance fistula or graft creates preferential flow patterns that compromise downstream perfusion.

Clinical manifestations include digital ischemia, pain, numbness, and tissue necrosis in severe cases. Risk factors include diabetes, peripheral vascular disease, and high-flow access creation. Treatment options range from access modification to surgical revision or closure in severe cases.

### Cardiac Effects and Right Heart Failure

High-flow arteriovenous access significantly increases cardiac output to maintain adequate systemic perfusion. This chronic volume overload contributes to left ventricular hypertrophy and may precipitate heart failure in susceptible patients.

The increased venous return elevates right-sided filling pressures, potentially leading to right heart failure and pulmonary hypertension. These cardiovascular complications contribute to increased mortality in dialysis patients, particularly those with pre-existing cardiac disease.

Access flow rates exceeding 2 liters per minute significantly increase cardiovascular risk and may warrant intervention. Careful monitoring of cardiac function and access flow helps identify patients requiring access modification to reduce cardiac burden.

## Dialysis Concentrate and Electrolyte Management

### Dialysate Composition

Dialysate concentrate contains precisely formulated electrolyte solutions designed to achieve desired plasma concentrations through diffusive and convective transport. The concentrate typically arrives as acid and bicarbonate components that require mixing with treated water to create the final dialysate.

Water treatment systems remove contaminants, bacteria, and endotoxins that could harm patients during the extended blood-membrane contact time. Reverse osmosis and deionization systems ensure water purity meeting strict quality standards for medical applications.

### Bicarbonate Separation

Bicarbonate concentrate requires separate storage and mixing to prevent precipitation with divalent cations like calcium and magnesium. When bicarbonate combines with these ions in concentrated solutions, insoluble precipitates form that could damage dialysis equipment and compromise patient safety.

The acid concentrate contains sodium, potassium, calcium, magnesium, and chloride, usually dextrose, and a small amount of acid (acetic acid or citric acid) that keeps calcium and magnesium from precipitating. When the concentrates are mixed, that acid becomes acetate (or citrate), which the body converts to bicarbonate, so the total alkali the patient receives is the bicarbonate setting plus the acetate (or citrate).^([20](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-20)) During dialysate preparation, the proportioning system carefully mixes acid and bicarbonate concentrates with treated water to achieve final desired concentrations while preventing precipitation.

### Electrolyte Settings

#### Sodium Management

A default dialysate sodium of 137-140 mEq/L is defensible for most patients, individualized toward the patient's own pre-dialysis sodium when interdialytic weight gain or hypertension is the problem; hypernatremic dialysate should be avoided.^([22](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-22)) Higher sodium concentrations help maintain plasma volume during ultrafiltration but contribute to thirst, interdialytic weight gain, and blood pressure; sodium below 138 mEq/L lowers weight gain and blood pressure slightly but increases intradialytic hypotension and cramps.^([29](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-29))

Sodium modeling (profiling) varies dialysate sodium during treatment, usually from high to low, in an effort to reduce hypotensive episodes. The evidence is limited: in the best randomized crossover trial (33 patients), combined sodium and ultrafiltration profiling reduced symptomatic sessions from 30.6% to 20.4%, with pre-dialysis weight 0.3 kg higher on profiled treatments,^([21](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-21)) and no benefit on hard outcomes has been shown. A profile whose time-averaged sodium sits above the patient's own sodium is a sodium load that raises thirst, interdialytic weight gain, and blood pressure; KDIGO advises that sodium balance during treatment be negative and that hypernatremic dialysate be avoided.^([22](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-22))

#### Potassium Control

Dialysate potassium concentrations of 2-3 mEq/L (1 or 4 mEq/L only by specific order) are the evidence-supported working range and allow control of serum potassium levels, as detailed in our hyperkalemia management protocols.^([28](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-28)) Patients with hyperkalemia require lower dialysate potassium to achieve adequate removal, while those prone to hypokalemia benefit from higher concentrations.

Rapid potassium shifts during dialysis may precipitate cardiac arrhythmias, particularly in patients with underlying heart disease. Careful monitoring and gradual correction help minimize these risks while achieving target serum concentrations.

#### Calcium Balance

Dialysate calcium concentrations of 2.5-3.0 mEq/L (1.25-1.50 mmol/L), as suggested by KDIGO,^([30](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-30)) maintain calcium homeostasis while considering patient medication regimens and bone disease status. Patients receiving calcium-based phosphate binders may require lower dialysate calcium to prevent hypercalcemia.

The interaction between calcium, phosphate, and parathyroid hormone creates complex relationships requiring individualized management. Regular monitoring of mineral metabolism parameters guides appropriate dialysate calcium selection.

#### Magnesium Balance

The standard dialysate magnesium is 1.0 mEq/L (0.5 mmol/L; 1.2 mg/dL).^([20](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-20)) At that concentration most patients lose magnesium during treatment: in 34 patients dialyzed against 0.5 mmol/L, plasma magnesium fell by an average of 0.10 mmol/L per session and was stable only in patients who started near 0.74 mmol/L.^([23](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-23))

#### Bicarbonate Correction

Dialysate bicarbonate concentrations of 32-40 mEq/L correct metabolic acidosis common in renal failure patients. Higher concentrations rapidly normalize acid-base status but may cause alkalosis if excessive. The dose is the total buffer, bicarbonate plus the acetate (or citrate) from the acid concentrate; the UK Renal Association suggests a total buffer at or below 37 mEq/L for most patients,^([20](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-20)) and each 4 mEq/L higher dialysate bicarbonate was associated with 8% higher mortality in DOPPS (HR 1.08).^([27](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-27))

The bicarbonate concentration influences carbon dioxide production and respiratory function during dialysis. Patients with compromised respiratory function may require careful bicarbonate management to prevent respiratory complications.

## Peritoneal Dialysis

Peritoneal dialysis utilizes the peritoneal membrane as a natural dialyzer, introducing dialysate into the peritoneal cavity for solute and fluid exchange. This continuous therapy provides more physiologic clearance patterns compared to intermittent hemodialysis.

The peritoneal membrane demonstrates different transport characteristics among patients, classified as high, high-average, low-average, or low transporters based on peritoneal equilibration testing. These transport characteristics guide prescription optimization and outcome prediction.

Continuous ambulatory peritoneal dialysis involves manual exchanges throughout the day, while automated peritoneal dialysis uses a cycler machine for nocturnal exchanges. Both modalities offer flexibility and independence advantages over hemodialysis but require patient motivation and manual dexterity.

Complications include peritonitis, catheter dysfunction, hernias, and membrane failure over time. Proper technique training and infection prevention protocols minimize these risks while maximizing therapy effectiveness — the ISPD peritonitis recommendations remain the standard reference for prevention, empirical therapy, and catheter-related infection management.^([16](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-16))

## Fluid Removal Kinetics and Hemodynamic Management

### Time Course of Fluid Removal in Hemodialysis

Hemodialysis achieves rapid fluid removal through ultrafiltration across the dialysis membrane, with rates typically ranging from 500-1500 mL per hour during standard treatments. This aggressive fluid removal occurs over a compressed timeframe of 3-4 hours, creating significant physiological stress on the cardiovascular system.

The ultrafiltration rate represents a critical balance between achieving dry weight targets and maintaining hemodynamic stability. Excessive ultrafiltration rates exceeding 10-13 mL per kilogram per hour substantially increase the risk of intradialytic hypotension and associated complications.^([11](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-11),[12](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-12)) The relationship between ultrafiltration rate and hemodynamic tolerance follows a threshold pattern, where modest increases above tolerance limits dramatically increase complication rates.

### Time Course of Fluid Removal in Peritoneal Dialysis

Peritoneal dialysis demonstrates fundamentally different fluid removal kinetics, achieving gradual continuous ultrafiltration over extended periods. Daily fluid removal typically ranges from 1-3 liters distributed across multiple exchanges or continuous cycling, creating minimal acute hemodynamic stress.

The osmotic gradient established by glucose or icodextrin in peritoneal dialysate drives fluid removal at rates generally below 200-300 mL per hour. This gentle approach allows physiological adaptation and maintains cardiovascular stability, particularly benefiting patients with compromised cardiac function or those prone to hypotensive episodes during hemodialysis.

### Fluid Compartment Dynamics and Vascular Refill

The critical concept of vascular refill determines hemodynamic tolerance during fluid removal. Ultrafiltration initially removes fluid from the intravascular compartment, creating a volume deficit that must be replenished from interstitial and intracellular spaces to maintain adequate circulating volume.

Vascular refill occurs through complex mechanisms involving Starling forces, oncotic pressure gradients, and lymphatic drainage. The rate of fluid mobilization from edematous tissues to the vascular compartment becomes the limiting factor in determining safe ultrafiltration rates. When ultrafiltration exceeds vascular refill capacity, intravascular volume depletion develops despite the presence of total body fluid overload.

This physiological principle explains why patients with significant peripheral edema may still experience hypotensive episodes during dialysis. The edematous fluid exists in poorly mobilized compartments that cannot rapidly equilibrate with the vascular space during acute fluid removal. The refill rate typically ranges from 200-400 mL per hour in healthy individuals but may be significantly impaired in patients with heart failure, diabetes, or advanced age.

### Pathophysiology of Intradialytic Hypotension

Intradialytic hypotension represents the most common acute complication during hemodialysis, occurring in approximately 10-12% of sessions by the most commonly used definitions (EBPG criteria or a nadir systolic blood pressure below 90 mmHg).^([19](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-19)) This is particularly problematic in patients with heart failure and reduced cardiac reserve. The pathophysiology involves multiple interconnected mechanisms beyond simple volume depletion, including autonomic dysfunction, cardiac output reduction, and peripheral vascular responses.

The sympathetic nervous system normally compensates for volume reduction through increased heart rate, enhanced contractility, and peripheral vasoconstriction. However, uremic patients frequently demonstrate impaired autonomic responses, reducing their ability to maintain blood pressure during volume challenges. Additionally, the warm dialysate environment and acetate-based solutions may contribute to peripheral vasodilation, further compromising hemodynamic stability.

Chronic volume overload in dialysis patients leads to cardiac remodeling and diastolic dysfunction, reducing the heart’s ability to maintain output during preload reduction. The combination of impaired ventricular filling and reduced contractile reserve creates particular vulnerability to fluid removal-induced hypotension.

### Clinical Manifestations and Consequences

Intradialytic hypotension typically manifests as symptomatic blood pressure reduction accompanied by cramping, nausea, vomiting, dizziness, and altered mental status. Muscle cramping represents a particularly distressing symptom that occurs due to rapid fluid shifts and electrolyte changes, often preceding frank hypotensive episodes.

The cramping phenomenon results from cellular dehydration and altered membrane excitability as fluid is rapidly removed from muscle cells. This process becomes more pronounced when ultrafiltration rates exceed cellular adaptation capacity, leading to painful contractions that may persist beyond the dialysis session.

Severe hypotensive episodes may precipitate cardiac arrhythmias, cerebrovascular events, or vascular access thrombosis. The hemodynamic stress of repeated hypotensive episodes contributes to cardiovascular morbidity and may accelerate the progression of existing cardiac disease in this high-risk population.

### Treatment Strategies for Intradialytic Hypotension

Immediate management of hypotensive episodes focuses on restoring intravascular volume and supporting cardiovascular function. Trendelenburg positioning enhances venous return, while normal saline administration provides rapid volume expansion. Typical saline boluses range from 100-250 mL, though larger volumes may be necessary in severe cases.

Reducing or temporarily stopping ultrafiltration allows vascular refill to occur without ongoing volume depletion. This intervention often provides rapid symptom relief and blood pressure stabilization, though it may compromise achievement of target fluid removal goals for that session.

Hypertonic saline solutions may provide more effective volume expansion with smaller volumes, reducing the risk of fluid overload while maintaining hemodynamic support. Mannitol administration can also enhance vascular refill by increasing plasma osmolality and promoting fluid mobilization from tissue compartments.

### Prevention Strategies

Preventing intradialytic hypotension requires comprehensive assessment of dry weight targets, treatment prescriptions, and patient-specific risk factors. Accurate dry weight determination represents the cornerstone of prevention, as inappropriate targets lead to either inadequate fluid removal or excessive volume depletion.

Gradual ultrafiltration rate adjustment allows physiological adaptation while achieving fluid removal goals. Sequential ultrafiltration, where initial fluid removal occurs without dialysate flow, may improve hemodynamic tolerance by avoiding rapid electrolyte shifts that compound volume-related hypotension.

Dialysate sodium and temperature modification can significantly reduce hypotensive episodes. Higher dialysate sodium preserves plasma volume and reduces hypotensive episodes, but the sodium load is repaid as thirst, weight gain, and blood pressure: raising dialysate sodium from 135 to 140 mEq/L cut the odds of intradialytic hypotension by about a third while raising pre-dialysis blood pressure by 7/4 mmHg.^([31](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-31)) Routine sodium profiling is not recommended; it was associated with higher mortality in DOPPS (HR 1.36).^([32](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-32)) Cool dialysate temperatures reduce peripheral vasodilation and improve cardiovascular stability during treatment.^([13](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-13))

Medication timing adjustments prevent exacerbation of hypotensive tendencies. Antihypertensive medications administered before dialysis may contribute to intradialytic hypotension, particularly when combined with aggressive fluid removal. Coordinating medication schedules with dialysis treatments optimizes blood pressure management while minimizing complications.

### Long-term Management Considerations

Patients with recurrent intradialytic hypotension may benefit from alternative dialysis prescriptions, including longer treatment times, more frequent sessions, or conversion to peritoneal dialysis. Extended treatments allow gentler fluid removal rates that better match physiological refill capacity — the FHN trial demonstrated that six-times-weekly hemodialysis improved a composite of death and left ventricular mass compared to conventional thrice-weekly dialysis.^([15](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-15))

Midodrine, an alpha-agonist given before dialysis, raises blood pressure in small short-term studies (nadir systolic pressure about 13 mmHg higher),^([14](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-14),[33](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-33)) but no outcome trial exists, and in a matched cohort of 1,046 users it was associated with higher mortality and hospitalization rates (confounding by indication is likely).^([34](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-34)) It is reserved for refractory symptomatic hypotension, by physician order, with monitoring for hypertension between treatments.

Cardiac function optimization through appropriate medical management of heart failure, coronary artery disease, and arrhythmias improves overall hemodynamic reserve and reduces susceptibility to volume-related complications during dialysis.

## Dialysis Prescription Components

### Hemodialysis Prescription Elements

The hemodialysis prescription represents a comprehensive treatment plan that specifies all parameters necessary to deliver safe and effective renal replacement therapy. The prescription must address solute clearance, fluid removal, electrolyte management, and hemodynamic considerations while accounting for individual patient characteristics and clinical status.

Treatment frequency constitutes the foundation of the hemodialysis prescription, with conventional therapy typically involving three sessions per week. Alternative schedules including more frequent dialysis or extended treatment times may be prescribed for patients with specific clinical needs or those experiencing complications with standard regimens. The timing between treatments affects interdialytic fluid accumulation and metabolic parameter control.

Treatment duration directly influences adequacy measurements and patient tolerance. Standard sessions range from three to four hours, though longer treatments may be prescribed to achieve adequate clearance in larger patients or those with poor access flow. Extended treatment times also allow gentler fluid removal rates, reducing the risk of intradialytic hypotension while achieving target dry weights.

Blood flow rate specifications determine the efficiency of solute clearance and must be balanced against vascular access limitations. Prescribed blood flow rates typically range from 300 to 450 milliliters per minute, with higher rates improving small solute clearance but requiring adequate access function to prevent recirculation or access dysfunction.

The dialyzer selection influences clearance characteristics and biocompatibility. High-flux dialyzers provide superior middle molecule clearance compared to conventional low-flux membranes, while surface area specifications affect overall solute removal capacity. Membrane material considerations include biocompatibility profiles and potential for allergic reactions in sensitive patients.

Dialysate flow rate prescriptions optimize concentration gradients while balancing efficiency with resource utilization. Standard flow rates of 500 to 800 milliliters per minute provide adequate clearance for most patients, with higher rates offering marginal improvements in small solute removal at increased cost.

Ultrafiltration specifications include target fluid removal volumes and maximum acceptable rates. The dry weight determination represents a critical prescription component that requires ongoing assessment and adjustment based on clinical examination, interdialytic weight gains, and hemodynamic tolerance during treatment.

Anticoagulation protocols prevent clotting within the extracorporeal circuit while minimizing bleeding risks. Heparin dosing regimens typically include initial bolus doses followed by continuous infusion rates adjusted for patient bleeding risk and circuit clotting tendency. Alternative anticoagulation strategies may be prescribed for patients with contraindications to systemic heparin.

### Dialysate Composition Prescription

Electrolyte concentrations within the dialysate require individualized prescription based on serum levels, clinical status, and medication regimens. Sodium prescriptions typically default to 137 to 140 milliequivalents per liter, individualized to the patient; higher concentrations support hemodynamic stability during ultrafiltration but increase interdialytic thirst, weight gain, and blood pressure, and hypernatremic dialysate should be avoided.^([22](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-22))

Potassium concentration selection depends on serum levels and cardiac risk assessment. Most patients are dialyzed against two or three milliequivalents per liter, with one or four reserved for specific orders; lower concentrations are indicated for hyperkalemic patients and higher levels prevent excessive potassium removal in those prone to hypokalemia.^([28](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-28))

Calcium prescriptions must consider bone and mineral metabolism parameters, phosphate binder usage, and parathyroid hormone levels. KDIGO suggests 2.5 to 3.0 milliequivalents per liter (1.25 to 1.50 mmol/L),^([30](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-30)) with adjustments based on serum calcium trends and vitamin D analog therapy.

Magnesium is prescribed at a standard 1.0 milliequivalent per liter (0.5 mmol/L), a concentration at which most patients lose magnesium during treatment.^([20](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-20),[23](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-23))

Bicarbonate concentration prescriptions address metabolic acidosis while avoiding alkalosis complications. Standard prescriptions range from 32 to 40 milliequivalents per liter, with higher concentrations reserved for patients with severe acidosis and lower levels for those prone to alkalemia. The acetate (or citrate) in the acid concentrate adds to the bicarbonate setting, and the total buffer should stay at or below 37 milliequivalents per liter for most patients.^([20](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-20),[27](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-27))

Glucose-containing dialysate is standard for all patients, not a diabetic add-on: the usual concentration is 100 milligrams per deciliter (5.6 mmol/L). Glucose-free dialysate causes frequent, usually silent, hypoglycemia,^([24](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-24)) and 200 milligrams per deciliter raises intradialytic glucose and insulin without further benefit.^([25](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-25)) At 100 to 200 milligrams per deciliter, dialysate glucose provides no meaningful osmotic force for ultrafiltration, which in hemodialysis is driven by transmembrane pressure.^([26](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-26))

### Peritoneal Dialysis Prescription Components

Peritoneal dialysis prescriptions encompass exchange volumes, dwell times, solution compositions, and cycling parameters that collectively determine adequacy and patient tolerance. The prescription must account for peritoneal membrane transport characteristics, patient lifestyle requirements, and clinical treatment goals.

Exchange volume prescriptions typically range from 1.5 to 3.0 liters per exchange, with larger volumes generally providing improved clearance but potentially causing discomfort or hernias in susceptible patients. Volume selection considers patient size, intraperitoneal pressure tolerance, and adequacy requirements determined through kinetic modeling.

Dwell time specifications affect both solute clearance and ultrafiltration efficiency. Longer dwell times enhance clearance of larger molecules but may reduce ultrafiltration as osmotic gradients dissipate. Typical dwell times range from four to eight hours for manual exchanges, with shorter cycles during automated peritoneal dialysis.

Solution glucose concentration determines ultrafiltration capacity and must be prescribed based on fluid removal requirements. Low-concentration solutions containing 1.5 percent glucose provide minimal ultrafiltration, while high-concentration solutions with 4.25 percent glucose achieve aggressive fluid removal. Intermediate concentrations of 2.5 percent glucose offer moderate ultrafiltration for routine fluid management.

Icodextrin solutions may be prescribed for long-dwell exchanges, particularly overnight dwells in continuous ambulatory peritoneal dialysis or daytime dwells in automated peritoneal dialysis. These solutions provide sustained ultrafiltration over extended periods and improve fluid removal in high-transport patients who experience rapid glucose absorption.

Exchange frequency prescriptions depend on the chosen peritoneal dialysis modality and adequacy requirements. Continuous ambulatory peritoneal dialysis typically involves four exchanges daily, while automated peritoneal dialysis may prescribe multiple short cycles during nighttime treatments with or without daytime exchanges.

### Automated Peritoneal Dialysis Programming

Automated peritoneal dialysis prescriptions include detailed programming parameters for cycler machines that perform exchanges during sleep periods. Fill volumes for individual cycles may vary throughout the treatment to optimize comfort and clearance, with initial cycles often using smaller volumes that increase as patient tolerance develops.

Drain time specifications ensure complete fluid removal between cycles while minimizing treatment duration. Inadequate drain times may result in residual fluid that reduces subsequent fill volumes and clearance efficiency. Typical drain times range from 10 to 20 minutes depending on catheter function and patient anatomy.

Number of cycles prescribed affects total treatment time and clearance characteristics. More frequent cycles with shorter dwell times favor small solute clearance, while fewer cycles with longer dwells optimize middle molecule removal. Standard prescriptions range from three to six cycles nightly.

Ultrafiltration monitoring parameters may be programmed to alert patients and providers to inadequate fluid removal or excessive ultrafiltration that could indicate peritoneal membrane changes or prescription adjustments needs.

### Prescription Individualization and Monitoring

Both hemodialysis and peritoneal dialysis prescriptions require regular assessment and modification based on adequacy measurements, laboratory results, and clinical response. Monthly kinetic modeling ensures that prescribed treatments achieve target clearance and adequacy parameters while identifying patients requiring prescription adjustments.

Laboratory monitoring guides prescription modifications for electrolyte management, acid-base balance, and mineral metabolism. Trends in serum parameters inform dialysate composition adjustments and treatment intensity modifications to maintain optimal biochemical control.

Clinical assessment of fluid status, blood pressure control, and symptom management influences prescription modifications for ultrafiltration targets, treatment frequency, and hemodynamic support measures. Patient tolerance and quality of life considerations factor into prescription decisions alongside purely medical parameters.

Adequacy targets specific to each modality guide prescription optimization, with hemodialysis targeting KT/V values exceeding 1.2 and peritoneal dialysis aiming for weekly KT/V values above 1.7. Achievement of these targets may require prescription modifications including treatment time extension, frequency increases, or modality conversion in selected patients.

## Clinical Considerations and Monitoring

Regular monitoring of dialysis adequacy, laboratory parameters, and clinical status ensures optimal patient outcomes. Monthly laboratory assessments include measures of adequacy (KT/V, URR), anemia management, bone and mineral metabolism, and cardiovascular risk factors.

Interdisciplinary care involving nephrologists, nurses, dietitians, and social workers addresses the complex medical and psychosocial needs of dialysis patients. This comprehensive approach optimizes clinical outcomes while maintaining quality of life during chronic renal replacement therapy.

The choice between hemodialysis and peritoneal dialysis depends on patient factors including lifestyle preferences, manual dexterity, support systems, and medical contraindications. Patients may require dialysis urgently for complications detailed in our AKI management guidelines.^([17](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-17)) Both modalities can provide adequate renal replacement when properly prescribed and monitored, with patient preference playing a significant role in modality selection. The IDEAL trial showed no survival benefit from earlier dialysis initiation, supporting symptom-driven timing.^([18](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html#ref-18))

## Sources

1.  NKF-KDOQI Clinical Practice Guideline for Hemodialysis Adequacy: 2015 Update. *Am J Kidney Dis*. 2015;66(5):884–930. [PMID: 26498416](https://pubmed.ncbi.nlm.nih.gov/26498416/)
2.  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. [PMID: 32778223](https://pubmed.ncbi.nlm.nih.gov/32778223/)
3.  Himmelfarb J, Vanholder R, Mehrotra R, Tonelli M. The Current and Future Landscape of Dialysis. *Nat Rev Nephrol*. 2020;16(10):573–585. [PMID: 32733095](https://pubmed.ncbi.nlm.nih.gov/32733095/)
4.  Eknoyan G, Beck GJ, Cheung AK, et al. Effect of Dialysis Dose and Membrane Flux in Maintenance Hemodialysis (HEMO Study). *N Engl J Med*. 2002;347(25):2010–2019. [PMID: 12490682](https://pubmed.ncbi.nlm.nih.gov/12490682/)
5.  Brown EA, Blake PG, Boudville N, et al. International Society for Peritoneal Dialysis practice recommendations: Prescribing high-quality goal-directed peritoneal dialysis. *Perit Dial Int*. 2020;40(3):244-253. [DOI](https://doi.org/10.1177/0896860819895364) \| [PubMed](https://pubmed.ncbi.nlm.nih.gov/32063219/)
6.  KDIGO 2017 Clinical Practice Guideline Update for the Diagnosis, Evaluation, Prevention, and Treatment of CKD–Mineral and Bone Disorder (CKD-MBD). *Kidney Int Suppl*. 2017;7(1):1–59. [PMID: 30675420](https://pubmed.ncbi.nlm.nih.gov/30675420/)

### Sources

1.  National Kidney Foundation. KDOQI Clinical Practice Guideline for Hemodialysis Adequacy: 2015 update. Am J Kidney Dis. 2015;66(5):884-930. [PubMed](https://pubmed.ncbi.nlm.nih.gov/26498416/)
2.  Lowrie EG, Laird NM, Parker TF, Sargent JA. Effect of the hemodialysis prescription on patient morbidity: report from the National Cooperative Dialysis Study. N Engl J Med. 1981;305(20):1176-1181. [PubMed](https://pubmed.ncbi.nlm.nih.gov/7027040/)
3.  Gotch FA, Sargent JA. A mechanistic analysis of the National Cooperative Dialysis Study (NCDS). Kidney Int. 1985;28(3):526-534. [PubMed](https://pubmed.ncbi.nlm.nih.gov/3934452/)
4.  Eknoyan G, Beck GJ, Cheung AK, et al. Effect of dialysis dose and membrane flux in maintenance hemodialysis. N Engl J Med. 2002;347(25):2010-2019. [PubMed](https://pubmed.ncbi.nlm.nih.gov/12490682/)
5.  Locatelli F, Martin-Malo A, Hannedouche T, et al. Effect of membrane permeability on survival of hemodialysis patients. J Am Soc Nephrol. 2009;20(3):645-654. [PubMed](https://pubmed.ncbi.nlm.nih.gov/19092122/)
6.  Grooteman MP, van den Dorpel MA, Bots ML, et al. Effect of online hemodiafiltration on all-cause mortality and cardiovascular outcomes (CONTRAST). J Am Soc Nephrol. 2012;23(6):1087-1096. [PubMed](https://pubmed.ncbi.nlm.nih.gov/22539829/)
7.  Maduell F, Moreso F, Pons M, et al. High-efficiency postdilution online hemodiafiltration reduces all-cause mortality in hemodialysis patients (ESHOL). J Am Soc Nephrol. 2013;24(3):487-497. [PubMed](https://pubmed.ncbi.nlm.nih.gov/23411788/)
8.  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. [PubMed](https://pubmed.ncbi.nlm.nih.gov/32778223/)
9.  Pisoni RL, Arrington CJ, Albert JM, et al. Facility hemodialysis vascular access use and mortality in countries participating in DOPPS: an instrumental variable analysis. Am J Kidney Dis. 2009;53(3):475-491. [PubMed](https://pubmed.ncbi.nlm.nih.gov/19150158/)
10. Dember LM, Beck GJ, Allon M, et al. Effect of clopidogrel on early failure of arteriovenous fistulas for hemodialysis: a randomized controlled trial. JAMA. 2008;299(18):2164-2171. [PubMed](https://pubmed.ncbi.nlm.nih.gov/18477783/)
11. Saran R, Bragg-Gresham JL, Levin NW, et al. Longer treatment time and slower ultrafiltration in hemodialysis: associations with reduced mortality in the DOPPS. Kidney Int. 2006;69(7):1222-1228. [PubMed](https://pubmed.ncbi.nlm.nih.gov/16609686/)
12. Flythe JE, Kimmel SE, Brunelli SM. Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality. Kidney Int. 2011;79(2):250-257. [PubMed](https://pubmed.ncbi.nlm.nih.gov/20927040/)
13. Chesterton LJ, Selby NM, Burton JO, McIntyre CW. Cool dialysate reduces asymptomatic intradialytic hypotension and increases baroreflex variability. Hemodial Int. 2009;13(2):189-196. [PubMed](https://pubmed.ncbi.nlm.nih.gov/19432693/)
14. Cruz DN, Mahnensmith RL, Brickel HM, Perazella MA. Midodrine is effective and safe therapy for intradialytic hypotension over 8 months of follow-up. Clin Nephrol. 1998;50(2):101-107. [PubMed](https://pubmed.ncbi.nlm.nih.gov/9725781/)
15. FHN Trial Group; Chertow GM, Levin NW, Beck GJ, et al. In-center hemodialysis six times per week versus three times per week. N Engl J Med. 2010;363(24):2287-2300. [PubMed](https://pubmed.ncbi.nlm.nih.gov/21091062/)
16. Li PK, Szeto CC, Piraino B, et al. ISPD Peritonitis Recommendations: 2016 Update on Prevention and Treatment. Perit Dial Int. 2016;36(5):481-508. [PubMed](https://pubmed.ncbi.nlm.nih.gov/27282851/)
17. Khwaja A. KDIGO clinical practice guidelines for acute kidney injury. Nephron Clin Pract. 2012;120(4):c179-c184. [PubMed](https://pubmed.ncbi.nlm.nih.gov/22890468/)
18. Cooper BA, Branley P, Bulfone L, et al. A randomized, controlled trial of early versus late initiation of dialysis (IDEAL). N Engl J Med. 2010;363(7):609-619. [PubMed](https://pubmed.ncbi.nlm.nih.gov/20581422/)
19. Kuipers J, Verboom LM, Ipema KJR, et al. The prevalence of intradialytic hypotension in patients on conventional hemodialysis: a systematic review with meta-analysis. Am J Nephrol. 2019;49(6):497-506. [PubMed](https://pubmed.ncbi.nlm.nih.gov/31129661/)
20. Ashby D, Borman N, Burton J, et al. Renal Association clinical practice guideline on haemodialysis. BMC Nephrol. 2019;20(1):379. [PubMed](https://pubmed.ncbi.nlm.nih.gov/31623578/)
21. Oliver MJ, Edwards LJ, Churchill DN. Impact of sodium and ultrafiltration profiling on hemodialysis-related symptoms. J Am Soc Nephrol. 2001;12(1):151-156. [PubMed](https://pubmed.ncbi.nlm.nih.gov/11134261/)
22. Flythe JE, Chang TI, Gallagher MP, et al. Blood pressure and volume management in dialysis: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney Int. 2020;97(5):861-876. [PubMed](https://pubmed.ncbi.nlm.nih.gov/32278617/)
23. Leenders NHJ, van Ittersum FJ, Hoekstra T, Hoenderop JGJ, Vervloet MG. Routine hemodialysis induces a decline in plasma magnesium concentration in most patients: a prospective observational cohort study. Sci Rep. 2018;8(1):10256. [PubMed](https://pubmed.ncbi.nlm.nih.gov/29980722/)
24. Burmeister JE, Scapini A, da Rosa Miltersteiner D, da Costa MG, Campos BM. Glucose-added dialysis fluid prevents asymptomatic hypoglycaemia in regular haemodialysis. Nephrol Dial Transplant. 2007;22(4):1184-1189. [PubMed](https://pubmed.ncbi.nlm.nih.gov/17272314/)
25. Raimann JG, Kruse A, Thijssen S, et al. Metabolic effects of dialyzate glucose in chronic hemodialysis: results from a prospective, randomized crossover trial. Nephrol Dial Transplant. 2012;27(4):1559-1568. [PubMed](https://pubmed.ncbi.nlm.nih.gov/21940484/)
26. Locatelli F, La Milia V, Violo L, Del Vecchio L, Di Filippo S. Optimizing haemodialysate composition. Clin Kidney J. 2015;8(5):580-589. [PubMed](https://pubmed.ncbi.nlm.nih.gov/26413285/)
27. Tentori F, Karaboyas A, Robinson BM, et al. Association of dialysate bicarbonate concentration with mortality in the Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis. 2013;62(4):738-746. [PubMed](https://pubmed.ncbi.nlm.nih.gov/23707043/)
28. Karaboyas A, Zee J, Brunelli SM, et al. Dialysate potassium, serum potassium, mortality, and arrhythmia events in hemodialysis: results from the Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis. 2017;69(2):266-277. [PubMed](https://pubmed.ncbi.nlm.nih.gov/27866964/)
29. Marshall MR, Wang MY, Vandal AC, Dunlop JL. Low dialysate sodium levels for chronic haemodialysis. Cochrane Database Syst Rev. 2024;11:CD011204. [PubMed](https://pubmed.ncbi.nlm.nih.gov/39498822/)
30. KDIGO CKD-MBD Update Work Group. KDIGO 2017 Clinical Practice Guideline Update for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). Kidney Int Suppl. 2017;7(1):1-59. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30675420/)
31. Miskulin DC, Tighiouart H, Hsu CM, Weiner DE. Dialysate sodium lowering in maintenance hemodialysis: a randomized clinical trial. Clin J Am Soc Nephrol. 2024;19(6):712-722. [PubMed](https://pubmed.ncbi.nlm.nih.gov/38349776/)
32. Dasgupta I, Thomas GN, Clarke J, et al. Associations between hemodialysis facility practices to manage fluid volume and intradialytic hypotension and patient outcomes. Clin J Am Soc Nephrol. 2019;14(3):385-393. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30723164/)
33. Prakash S, Garg AX, Heidenheim AP, House AA. Midodrine appears to be safe and effective for dialysis-induced hypotension: a systematic review. Nephrol Dial Transplant. 2004;19(10):2553-2558. [PubMed](https://pubmed.ncbi.nlm.nih.gov/15280522/)
34. Brunelli SM, Cohen DE, Marlowe G, Van Wyck D. The impact of midodrine on outcomes in patients with intradialytic hypotension. Am J Nephrol. 2018;48(5):381-388. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30423552/)

## Educational Resources

- Student Guide: Dialysis Hub — PA/medical student educational guide

### Also on this topic

The same subject at other levels of depth.

- **Student handout:** [Dialysis Fundamentals: Student Handout](https://urinenephrology.org/student-resources/dialysis/dialysis-fundamentals-student-handout.html)


---

[Website version](https://urinenephrology.org/mastery/dialysis-advanced/dialysis-student-guide.html) · Markdown synchronized October 3, 2026.