Hemodialysis: Vascular Access, Equipment, and Treatment
Access fundamentals
Compare arteriovenous fistula, arteriovenous graft, and central venous catheter. Fistulas have the best patency and lowest infection risk but need maturation; grafts mature faster with higher failure and infection risk; catheters carry the highest infection and thrombosis risk and should be temporary or a last resort. Assess access by palpation (thrill), auscultation (bruit), and surveillance for stenosis. Protect the access arm from blood pressure cuffs, venipuncture, and compression.
Equipment and prescription
Understand the dialyzer (membrane type, surface area, clearance), blood flow and dialysate flow rates, ultrafiltration goal, dialysate composition (sodium, potassium, calcium, bicarbonate), and anticoagulation. Know the meaning of Kt/V and urea reduction ratio as adequacy measures. Recognize machine alarms and their usual causes: arterial pressure alarms (access or needle problem), venous pressure alarms (kinking, infiltration, clotting), air detector alarms, and conductivity or temperature alarms.
Complications and traps
Anticipate hypotension, cramping, disequilibrium syndrome, dialyzer reactions, air embolism, hemolysis, and access infections. Trap: attributing hypotension to the patient's dry weight without checking ultrafiltration rate, food intake, or antihypertensive timing. Trap: assuming a catheter is safe because it is newly placed. Remember that dialysate potassium and calcium settings can cause arrhythmias if mismatched to the patient.
Worked example and rule of thumb
A patient becomes hypotensive with cramping near the end of treatment. Slow or pause ultrafiltration, reposition, and give isotonic fluid as ordered; review the ultrafiltration goal for the next session. Rule of thumb: access choice follows the "fistula first, catheter last" principle, and any access with fever or purulence is a serious infection until proven otherwise.