What is the most likely cause of low arterial pressure in a 63-year-old female patient with chronic kidney disease (CKD) secondary to hypertension, undergoing hemodialysis?

Low Arterial Pressure During Hemodialysis: Most Likely Cause

The most likely culprit is kinks in the tubing (Option B), as this is a mechanical problem that directly causes low arterial pressure readings on the dialysis machine by creating resistance in the arterial line, preventing adequate blood flow from the patient to the dialysis circuit.

Understanding Arterial vs. Venous Pressure in Dialysis

The question specifically asks about low arterial pressure during hemodialysis, which refers to the pressure measured in the arterial line (the line drawing blood from the patient). This is distinct from venous pressure (measured in the return line) and from the patient's systemic blood pressure.

Key Distinction in Dialysis Pressure Monitoring

• Arterial line pressure (pre-pump pressure) is typically negative during dialysis as blood is pulled from the access into the circuit 1
• Venous line pressure (post-pump pressure) is typically elevated as blood is returned to the patient 2
• Low arterial pressure readings indicate inadequate blood flow into the dialysis circuit 1

Why Kinks in Tubing (Option B) is Most Likely

Mechanical Obstruction Creates Low Arterial Pressure

• Kinks in the arterial tubing create resistance that prevents adequate blood withdrawal from the access, resulting in abnormally low (more negative) arterial pressure readings 1
• This is an immediate, acute problem that nurses would detect during routine monitoring and is easily correctable 1
• Kinked tubing is a common technical complication that directly affects pressure measurements in the arterial line 1

Why Other Options Are Less Likely

Option A: Venous Outflow Stenosis - Wrong Pressure System

• Venous outflow stenosis causes elevated venous pressure, not low arterial pressure 2
• This pathology affects the venous return line and access outflow, with stenotic lesions typically at the vein-graft anastomosis or central veins 2
• Venous stenosis presents with high venous dialysis pressure (>150 mmHg at 200 mL/min blood flow), progressive increase in venous pressure ratio ≥0.25 above baseline, and clinical signs like arm edema and prolonged bleeding after decannulation 2
• This is the opposite pressure abnormality from what the question describes 2

Option C: Hypertension - Contradictory to Presentation

• Hypertension refers to elevated systemic blood pressure, not low arterial line pressure during dialysis 3
• While hypertension is prevalent in 50-60% of hemodialysis patients, it would not cause low arterial pressure readings on the dialysis machine 3
• The patient's underlying hypertensive nephrosclerosis (HPNSS) is a chronic condition, not an acute cause of low arterial pressure during a specific dialysis session 3

Option D: Clotting in Venous Blood Lines - Wrong Location

• Clotting in the venous blood lines would cause elevated venous pressure, not low arterial pressure 2
• Clots in the venous line create obstruction in the return pathway, increasing resistance and raising venous pressure readings 2
• If clotting were affecting the arterial side, it would more likely occur at the access itself rather than in the lines, and would present differently 2

Clinical Approach to Low Arterial Pressure Alarms

Immediate Assessment Steps

• Inspect the arterial line for visible kinks, bends, or compression along its entire length from access to dialysis machine 1
• Check arterial needle positioning to ensure it's not against the vessel wall or partially occluded 2
• Verify blood pump speed and flow rate settings 1
• Assess access patency by checking for thrill and bruit 2

Management Algorithm

• First-line intervention: Straighten any kinked tubing and reposition the patient's arm to eliminate mechanical obstruction 1
• If pressure normalizes immediately after straightening tubing, this confirms the diagnosis 1
• If low arterial pressure persists despite correcting tubing position, consider arterial needle malposition or access inflow problems 1, 2
• Document the intervention and pressure response for quality monitoring 1

Important Clinical Caveat

Do not confuse low arterial line pressure with intradialytic hypotension (low systemic blood pressure). The question asks about arterial pressure detected by nurses during routine dialysis monitoring, which refers to machine pressure readings, not the patient's blood pressure. Intradialytic hypotension would present with symptoms like dizziness, nausea, and decreased systemic blood pressure readings, affecting approximately 25% of dialysis sessions 1. The scenario describes an isolated low arterial pressure finding without mention of systemic symptoms, pointing to a technical/mechanical issue rather than hemodynamic instability 1.