Thrombotic Causes

Thrombotic occlusion is the most common cause of catheter dysfunction after mechanical problems are excluded, with locations of obstruction including intraluminal thrombus, catheter tip thrombus, fibrin sheath, and fibrin tail 1, 2
The American Journal of Kidney Diseases recommends considering thrombolytic therapy for catheter occlusions, with tissue plasminogen activator restoring patency in 67% with one dose and 88% with two doses 2

Non-Thrombotic Mechanical Causes

Catheter malposition, including tip migration, catheter withdrawal, and tip position against the vessel wall, can prevent adequate blood flow 1, 2, 3, 4
Pinch-off syndrome, caused by compression between the clavicle and first rib, can lead to catheter rupture or occlusion 5, 3
Kinking along the catheter path can also cause occlusion 5, 4

Non-thrombotic precipitates, including parenteral nutrition components and medication crystallization, can cause sudden occlusion 5
The American Journal of Kidney Diseases suggests that lipid occlusions may respond to 70% ethyl alcohol 5

The initial assessment algorithm should include determining catheter age, checking patient positioning, evaluating lines and machines, attempting line reversal, and considering imaging to identify kinked catheter, aberrant tip position, or fibrin sheath 1, 2, 3, 4
The American College of Physicians recommends avoiding vigorous suction during attempts to determine catheter occlusion due to the risk of vascular wall damage or soft-walled catheter collapse 1

Neuraxial catheters are considered to have failed when they cannot provide satisfactory analgesia, requiring replacement or alternative pain relief, as defined by the American Society of Anesthesiologists 6, 7, 8
Hemodialysis catheters are considered to have failed when they cannot attain and maintain blood flow ≥300 mL/min at prepump arterial pressure more negative than -250 mmHg, according to the National Kidney Foundation 9

Catheter dysfunction represents progressive deterioration in catheter performance, characterized by blood flow rates <300 mL/min, venous pressure >250 mmHg, and decreased dialysis adequacy, as reported by the American Journal of Kidney Diseases 9, 10, 11
Fibrin sheath formation, catheter migration, and pinch-off syndrome are common mechanical complications that may resemble "fatigue", as described by the Clinical Nutrition journal 9, 11, 12

The age of the catheter determines the likely cause of problems, with new catheters (<2 weeks) typically experiencing mechanical obstruction or improper tip location, and older catheters (≥2 weeks) experiencing progressive occlusion by fibrin or thrombus, according to the American Journal of Kidney Diseases 9
Waiting until blood flow decreases to 300 mL/min may be too late to salvage the catheter, and early detection of catheter dysfunction is crucial to avoid loss of the access site, as recommended by the National Kidney Foundation 9, 10, 11

The National Kidney Foundation defines a catheter as dysfunctional when it cannot achieve and maintain an extracorporeal blood flow of 300 mL/min or greater with a pre-pump arterial pressure more negative than -250 mmHg, with exceptions for pediatric or small adult catheters not designed for flows over 300 mL/min 13
The American Journal of Kidney Diseases recommends that catheter dysfunction be identified by parameters including blood pump flow < 300 mL/min, arterial pressure < -250 mmHg, venous pressure > 250 mmHg, conductance < 1.2, and progressively decreasing URR < 65% or Kt/V < 1.2 14

The American College of Physicians suggests that catheter thrombosis occurs in 30% to 40% of patients and represents 17% to 33% of premature catheter removals 14
The American Journal of Kidney Diseases states that oclusiones lipídicas can be treated with 70% ethanol according to their guidelines 13

Early detection of catheter dysfunction is crucial, as a dysfunctional catheter is easier to rescue than a non-functional one, and waiting until blood flow decreases to 300 mL/min may be too late to save the catheter 14
Trend analysis of changes in access flow is the best predictor of access patency and risk of thrombosis 14