What is the proper protocol for returning blood to a patient after dialysis, considering the use of anticoagulants like heparin and potential complications such as hypotension?

Returning Blood After Dialysis

Blood should be returned to the patient using the slow flow/stop pump technique, which involves reducing blood pump flow to 50-100 mL/min for 15 seconds, then stopping the pump completely before disconnecting, followed by standard patient disconnection per unit protocol. 1

Standard Blood Return Protocol

Slow Flow/Stop Pump Technique (Preferred Method)

The NKF-K/DOQI guidelines establish this as the gold standard approach for blood return at dialysis completion: 1

• Reduce blood pump flow to 50-100 mL/min for approximately 15 seconds to clear the arterial sampling port of recirculated blood 1
• Stop the blood pump completely before any blood sampling or disconnection procedures 1
• Wait 15-30 seconds after stopping the pump to allow access recirculation to resolve (this occurs within seconds to 0.25-0.50 minutes) 1
• Return blood to the patient using standard reinfusion procedures 1
• Proceed with patient disconnection according to unit protocol 1

Timing Considerations for Blood Return

The timing of blood return critically affects urea rebound and laboratory measurements: 1

• Access recirculation resolves within seconds after stopping dialysis, making immediate blood return safe 1
• Cardiopulmonary recirculation resolves within 1-3 minutes after dialysis cessation 1
• Complete blood reinfusion typically takes at least 5 minutes, during which partial urea rebound occurs 1

Anticoagulation Management During Blood Return

Heparin Considerations

The anticoagulant effect of heparin used during dialysis has minimal impact on blood return safety when performed on schedule: 2, 3

• Unfractionated heparin has a half-life of 1-2 hours, while low molecular weight heparin has a half-life of approximately 4 hours 1, 4
• Standard intradialytic heparin dosing for extracorporeal dialysis is 25-30 units/kg bolus followed by 1,500-2,000 units/hour infusion 2
• Heparin is typically discontinued 30-60 minutes before dialysis completion in standard protocols, allowing partial clearance before blood return 3

High Bleeding Risk Patients

For patients at increased bleeding risk, alternative strategies should be employed: 3

• Heparin-free dialysis is indicated for actively bleeding patients, those within 3 days of bleeding episodes or surgical wounds, or within 2 weeks of cerebral/retinal hemorrhage 3
• Regional anticoagulation with citrate, prostacyclin, or mesilates eliminates systemic anticoagulation effects 3
• Minimal heparinization protocols reduce bleeding risk while maintaining circuit patency 3
• Peritoneal dialysis completely avoids systemic anticoagulation and may be preferred for high-risk patients 3

Preventing Hypotension During Blood Return

Volume management during blood return is critical to prevent hypotensive episodes:

• Slow the ultrafiltration rate or discontinue it entirely during the final 15-30 minutes of dialysis to allow vascular refilling 1
• Monitor blood pressure continuously during blood return, particularly in patients with intradialytic hypotension history 1
• Ensure adequate blood flow rates (50-100 mL/min during the slow flow phase) to prevent access thrombosis while minimizing hemodynamic stress 1

Blood Reinfusion Sampling Technique (Alternative Method)

While less preferred, the blood reinfusion technique is widely used: 1

• Complete blood reinfusion first, which takes at least 5 minutes 1
• Draw post-dialysis samples after reinfusion is complete 1
• This method allows 5-10 minutes of urea rebound, resulting in partially equilibrated BUN samples that underestimate delivered dialysis dose 1
• Variability in reinfusion timing between sessions introduces unacceptable measurement inconsistency 1

Critical Pitfalls to Avoid

Common errors during blood return that compromise patient safety or measurement accuracy:

• Never draw blood samples immediately at time zero after stopping dialysis, as access recirculation causes falsely low BUN and overestimated Kt/V 1
• Never use high blood pump flows (>100 mL/min) during the sampling/disconnection phase, as this perpetuates access recirculation 1
• Never perform blood return in patients with active uncontrolled bleeding without first achieving hemostasis and considering heparin-free dialysis 1, 3
• Never assume heparin has fully cleared at dialysis end—the half-life of 1-2 hours means significant anticoagulant effect persists 2, 4
• Never rush the blood return process in hypotension-prone patients, as rapid volume shifts exacerbate hemodynamic instability 1

Special Populations

Catheter-Based Access

For patients with venous catheters rather than fistulas/grafts: 1

• Withdraw heparin and saline from the arterial port before any blood return procedures 1
• Use sterile technique throughout catheter manipulation 1
• The dead space in venous catheters is 1-2 mL, less than arteriovenous access but still requiring the slow flow technique 1

Pediatric Patients

Pediatric dialysis patients require modified protocols: 1

• Withdraw 3-5 mL (rather than 10 mL in adults) when clearing catheter dead space, according to catheter fill volume 1
• Adjust heparin dosing to 75-100 units/kg bolus with maintenance of 25-30 units/kg/hour in infants 2
• Use preservative-free heparin in neonates and infants to avoid benzyl alcohol toxicity 2