Intradialytic Hypotension Causes and Risk Factors

Primary Pathophysiologic Mechanisms

Intradialytic hypotension results from two fundamental mechanisms: insufficient intravascular volume to support the ultrafiltration rate and inadequate cardiovascular compensatory responses to volume removal, according to the American College of Cardiology 1
Excessive ultrafiltration is the most common cause, occurring when fluid removal exceeds the rate of vascular refilling from the interstitial compartment, as reported by the American Journal of Kidney Diseases 2, 3
Ultrafiltration rates as low as 6 mL/h/kg can be associated with higher mortality risk, indicating that even modest rates can overwhelm compensatory mechanisms in vulnerable patients, according to the American College of Cardiology 1
Inadequate dry weight assessment leads to chronic hypovolemia, triggering compensatory mechanisms including increased thirst and paradoxically higher interdialytic weight gains, as stated by the American College of Cardiology 1

Acetate-containing dialysate contributes to hypotension by decreasing total vascular resistance, increasing venous pooling, and increasing myocardial oxygen consumption, according to the American College of Cardiology 1
Elevated dialysate temperature (37°C) promotes peripheral vasodilation and reduces sympathetic tone, whereas the optimal temperature of 34-35°C increases peripheral vasoconstriction through enhanced sympathetic activity, as reported by the American College of Cardiology 1, 4
Bicarbonate-buffered dialysate should replace acetate-based solutions to minimize hypotensive episodes, as recommended by the American Journal of Kidney Diseases 2, 4

Diabetic patients with autonomic neuropathy show exaggerated drops in systolic and diastolic blood pressures compared to those without autonomic dysfunction, according to the American Journal of Kidney Diseases 3
Elderly patients (≥65 years) have increased susceptibility to intradialytic hypotension, as reported by the American Journal of Kidney Diseases 3
Patients with pre-dialysis systolic blood pressure <100 mmHg, including anephric patients and those on long-term dialysis, are at higher risk, according to the American Journal of Kidney Diseases 3
Patients with cardiovascular disease, including left ventricular hypertrophy with diastolic dysfunction, systolic dysfunction with heart failure, valvular disease, or pericardial disease, are at increased risk, as stated by the American Journal of Kidney Diseases 3

Antihypertensive medications taken before dialysis prevent compensatory vasoconstriction and cardiac responses, exacerbating hypotension, according to the American College of Cardiology 1, 4
Dialyzable antihypertensive agents, including enalapril, ramipril, methyldopa, atenolol, acebutolol, nadolol, minoxidil, and nitroprusside, are removed during hemodialysis, potentially causing paradoxical blood pressure changes, as reported by the American Journal of Kidney Diseases 5
Nitrates used before dialysis sessions increase the risk of hypotension in patients with coronary artery disease, according to the American Journal of Kidney Diseases 3

Food intake immediately before or during hemodialysis causes splanchnic vasodilation and decreased peripheral vascular resistance, redirecting blood flow away from the peripheral circulation, as stated by the American College of Cardiology 1
Severe anemia reduces oxygen-carrying capacity and impairs cardiovascular compensation, though correction to hemoglobin ≥11 g/dL can reduce hypotension incidence, according to the American College of Cardiology 1, 4
Hypoalbuminemia and poor nutritional status are associated with increased risk of intradialytic hypotension, as reported by the American Journal of Kidney Diseases 3

Intradialytic hypotension occurs in 25% to 50% of all hemodialysis treatments, making it the most common acute complication, according to the American Journal of Kidney Diseases 3
Recurrent hypotension creates a cascade of end-organ ischemia affecting the heart, brain, liver, gut, and kidneys, contributing to increased morbidity and mortality, as stated by the American College of Cardiology 1
Premature termination of dialysis due to hypotension results in inadequate dialysis dose (suboptimal Kt/V) and failure to meet ultrafiltration goals, according to the American Journal of Kidney Diseases 2, 3
Long-term consequences include volume overload from suboptimal ultrafiltration, left ventricular hypertrophy with associated morbidity and mortality, and interdialytic hypertension, as reported by the American Journal of Kidney Diseases 3