BONENT CHN key terms

The kidney's microscopic functional unit, consisting of a glomerulus and a tubule. Each kidney contains about one million nephrons, which filter blood, reabsorb needed substances, and secrete waste into urine.

The volume of fluid filtered from the blood into the kidney's tubules per minute, usually expressed in mL/min. It is the best overall measure of kidney function and falls as kidney disease advances.

Kidney damage or reduced kidney function lasting three months or longer. It is staged 1 through 5 by GFR, and stage 5 (GFR under 15) generally corresponds to the point where dialysis or transplant is needed.

The buildup of urea and other nitrogenous wastes in the blood when the kidneys fail. It produces symptoms such as fatigue, nausea, itching, confusion, and a metallic taste, and it is what dialysis is designed to reverse.

A hormone made mainly by the kidneys that signals the bone marrow to produce red blood cells. Diseased kidneys make too little, causing renal anemia that is treated with erythropoiesis-stimulating agents and iron.

A hormone cascade the kidneys trigger when they sense low blood pressure or low sodium. Renin leads to angiotensin II, a vasoconstrictor, and aldosterone, which retains sodium, raising blood pressure and worsening kidney damage over time.

A blood potassium level above the normal range, roughly over 5.0 to 5.5 mEq/L. In kidney failure the kidneys cannot excrete potassium, and high levels can cause fatal cardiac arrhythmias, so it is a common reason for urgent dialysis.

A condition in which blood pH falls because the kidneys cannot excrete enough acid or regenerate bicarbonate. In CKD it contributes to bone loss, muscle wasting, and protein breakdown and is corrected by bicarbonate dialysate and oral bicarbonate.

The removal of plasma water from the blood across the dialyzer membrane by a pressure gradient. The rate is set to remove the fluid gained between treatments and return the patient to dry weight.

The pressure difference across the dialyzer membrane, calculated roughly as the average blood compartment pressure minus the dialysate compartment pressure. It is the driving force for ultrafiltration.

The volume of blood pumped through the extracorporeal circuit per minute, typically 200 to 500 mL/min in adults. Higher rates generally improve clearance but may be limited by what the vascular access can supply.

The volume of dialysate passing through the dialyzer per minute, commonly 500 to 800 mL/min. Increasing it helps maintain the concentration gradient for diffusion, but the benefit levels off above about twice the blood flow rate.

A measure of dialysis adequacy: clearance (K) times treatment time (t) divided by the patient's urea distribution volume (V). Higher values mean more urea removed; a common target is a single-pool Kt/V of at least 1.2 per treatment.

The percentage drop in blood urea nitrogen across a treatment, calculated from pre-dialysis and post-dialysis BUN. It is a simpler adequacy measure than Kt/V, with a target of at least 65 percent.

The body weight at which the patient has no excess fluid yet is not dehydrated, judged by absence of edema, stable blood pressure, and no cramping or hypotension at the end of treatment. Ultrafiltration targets this weight.

A drop in blood pressure during dialysis, often defined as a fall of 20 to 30 mmHg systolic or below 90 mmHg, with dizziness, nausea, or cramping. Common causes are excessive ultrafiltration, eating during treatment, and blood pressure medications.

Painful involuntary contractions, usually in the legs or feet, that occur during or shortly after dialysis. They are often linked to rapid fluid removal, a dry weight set too low, or electrolyte shifts, and are managed by slowing ultrafiltration or giving saline.

A neurological reaction to overly rapid solute removal, especially in the first treatments, causing headache, nausea, restlessness, confusion, seizures, or coma. Urea leaves the blood faster than the brain, so water shifts into brain cells.

A surgically created connection between an artery and a vein, usually in the forearm, that enlarges the vein so it can carry high blood flow for dialysis. It is preferred because it lasts longest and has the lowest infection rate.

A synthetic tube implanted to connect an artery and a vein when the patient's own vessels cannot support a fistula. It can be used sooner after placement than a fistula but is more prone to clotting and infection.

A tube placed in a large vein, often the internal jugular, with the tip in the right atrium, used for temporary or long-term vascular access. Catheters carry the highest risk of bloodstream infection and clot formation.

The fraction of already-dialyzed blood that returns to the dialyzer instead of reaching the body, usually because of access problems such as stenosis or poorly placed needles. It lowers effective clearance and can falsely lower the post-dialysis BUN.

A dialyzer containing thousands of fine semipermeable capillary fibers through which blood flows while dialysate passes around them. It packs a large surface area for diffusion and ultrafiltration into a compact housing.

A dialyzer specification combining membrane permeability and surface area; a higher KoA means the dialyzer clears urea faster. It helps predict whether a given dialyzer can support high-flux or high-efficiency treatment.

A dialyzer membrane with larger pores that removes small solutes plus larger middle molecules such as beta-2 microglobulin. High-flux dialyzers require ultrapure dialysate because backfiltration can carry contaminants into the blood.

Giving unfractionated heparin, usually as a bolus plus continuous infusion, to prevent clotting in the extracorporeal circuit during dialysis. Dosing is adjusted to the patient's bleeding risk and monitored with clotting times.

A technique in which citrate is infused into the arterial line to bind calcium and block clotting in the circuit while calcium is replaced intravenously. It is used for patients who cannot receive heparin because of bleeding risk.

A water treatment process that pushes tap water through a semipermeable membrane under pressure, removing most dissolved ions, bacteria, and endotoxins. RO water is the base for preparing dialysate.

A water treatment step in which ion exchange resins remove charged minerals from water. It does not remove bacteria or endotoxins and is often used in combination with reverse osmosis.

A measure of how well dialysate conducts electricity, which reflects its total dissolved salt concentration. Machines check conductivity continuously to confirm the dialysate is mixed correctly and is neither too concentrated nor too dilute.

The standard dialysate, made by mixing a bicarbonate solution with an acid concentrate inside the machine. It corrects metabolic acidosis but must be used promptly because calcium and bicarbonate can precipitate and bacteria can grow.

A test of treated water for chlorine and chloramines, performed before treatments because carbon filters remove them. Chlorine breakthrough can cause hemolysis, so the test must read zero before dialysis starts.

Fragments of bacterial cell walls that can cross dialyzer membranes and trigger fever, chills, and inflammation. Water and dialysate are monitored with limulus amebocyte lysate testing and kept within AAMI limits.

Infection control practices applied to every patient, including hand hygiene, gloves, gowns, masks, eye protection as needed, and safe handling of sharps and soiled items. They assume any blood or body fluid may be infectious.

Blood testing of patients and staff for hepatitis B infection. HBsAg-positive patients may need dedicated machines and separation from other patients, and vaccination is recommended for all susceptible patients and dialysis staff.

A bloodstream infection traced to a central venous catheter, presenting with fever, chills, and positive blood cultures. Prevention includes scrupulous hub disinfection, careful dressing care, and removing the catheter as soon as it is no longer needed.

An accidental puncture of the skin by a used needle, a risk when cannulating a fistula or disposing of sharps. Immediate washing, reporting, and post-exposure evaluation for hepatitis B, hepatitis C, and HIV are required.

Reprocessing a dialyzer for multiple treatments in the same patient, requiring validated cleaning, testing of membrane volume and integrity, and correct labeling. Reuse is regulated and a dialyzer must never be shared between patients.