How do you identify hemolysis in a patient undergoing hemodialysis (HD)?

Identifying Hemolysis During Hemodialysis

Hemolysis during hemodialysis is identified through a combination of clinical symptoms (abdominal pain, malaise, headache), visual inspection of blood in the extracorporeal circuit (pink or red discoloration), and laboratory confirmation with elevated plasma hemoglobin (>3 g/L), elevated LDH, and decreased or unmeasurable haptoglobin.

Clinical Presentation and Immediate Recognition

Cardinal Symptoms

• Abdominal pain (60% of cases), malaise, nausea, and headache are the most common presenting symptoms during acute intradialytic hemolysis 1
• Hypertension develops in approximately 66% of patients experiencing hemolysis during dialysis 1
• Severe cases may progress to intensive care unit admission (36% of cases) with potential mortality 1

Visual Inspection of the Circuit

• Pink or red discoloration of the blood in the extracorporeal circuit or dialysate indicates hemolysis and should prompt immediate investigation 2
• Inspect the arterial and venous blood lines for kinking, particularly at the dialyzer inlet port and just after the pump segment where severe kinking can occur 2
• Check for mechanical obstruction or narrowing of apertures in the blood tubing through which blood is pumped 1

Laboratory Confirmation

Primary Diagnostic Tests

• Plasma hemoglobin elevation (3-21 g/L in documented cases) is the most direct indicator of intravascular hemolysis 1, 2
• Haptoglobin is the most sensitive marker—levels become unmeasurable or severely decreased (<0.09 g/L) during hemolysis 1, 3
• Lactate dehydrogenase (LDH) markedly elevates (542-3,300 IU/L in hemolysis cases) 1, 2
• Unconjugated bilirubin increases as a secondary marker 3, 4

Important Caveats

• Hemolysis interference affects LDH and AST measurements even at undetectable hemolysis levels by visual inspection (plasma hemoglobin <0.5 g/L), potentially confounding interpretation 5
• Potassium and total bilirubin show clinically meaningful variations only in moderately hemolyzed samples (hemoglobin >1 g/L) 5
• Reticulocyte counts typically exceed 120×10⁹/L, except during the very early phase of acute hemolysis or with associated vitamin deficiency 3

Systematic Investigation Algorithm

Step 1: Immediate Assessment During Dialysis

• Monitor for sudden onset of abdominal pain, malaise, headache, or hypertension during treatment 1
• Visually inspect blood lines and dialysate for pink/red discoloration 2
• Check extracorporeal circuit pressures—back pressure without alarm may indicate occluded tubing causing hemolysis 2

Step 2: Equipment Inspection

• Examine blood tubing for kinking at the dialyzer inlet port and immediately after the pump segment 2
• Verify proper fitting of blood lines—extra long pump segments with short remaining tubing can cause severe kinking 2
• Check for narrowing of apertures in disposable hemodialysis blood tubing cartridge sets 1
• Review dialyzer clotting and anticoagulation protocol 6

Step 3: Laboratory Confirmation

• Draw plasma hemoglobin level immediately (target: identify levels >3 g/L) 1
• Measure haptoglobin (expect unmeasurable or <0.09 g/L) 1
• Check LDH (expect >542 IU/L) 1
• Obtain unconjugated bilirubin 3

Step 4: Rule Out Other Causes

• Review for chemical contamination, heat exposure, or mechanical trauma beyond kinked lines 1, 4
• Exclude hemodialyzer blood leak by checking for blood in dialysate 6
• Verify blood pump calibration and review extracorporeal pressures (particularly prepump arterial pressure <-200 mmHg) 6
• Check dialysate temperature—overheating can cause hemolysis 1

Common Pitfalls to Avoid

• Do not rely solely on visual inspection for hemolysis detection—routine determination of plasma free hemoglobin concentrations is recommended to avoid improper sample rejection 5
• Do not dismiss mild symptoms—hemolysis can progress rapidly from malaise to severe illness requiring ICU admission 1
• Do not overlook blood line kinking as a cause—this mechanical trauma produces visible hemolysis within 30 minutes in experimental models 2
• Do not continue dialysis if hemolysis is suspected—immediately release any kinked lines and consider stopping treatment if symptoms persist 2

Specific Hemolysis Thresholds for Laboratory Interference

When interpreting labs in suspected hemolysis:

• Hemoglobin <0.5 g/L: LD and AST already affected 5
• Hemoglobin >1 g/L: Potassium and total bilirubin show clinically meaningful variations 5
• Hemoglobin 2.5-4.5 g/L: ALT, cholesterol, GGT, and inorganic phosphate remain unaffected 5