What is the protocol for drawing a potassium lab via Peripherally Inserted Central Catheter (PICC) line?

Protocol for Drawing Potassium Lab via PICC Line

When drawing blood samples for potassium measurement from a PICC line, proper technique must be followed to ensure accurate results and prevent complications.

Proper Blood Draw Technique for PICC Lines

Preparation Steps

1. Gather all necessary supplies:

   • Sterile gloves
   • Chlorhexidine solution with alcohol for site preparation 1
   • Appropriate blood collection tubes
   • Syringes (10-20 mL for discard sample, appropriate size for actual draw)
   • Normal saline flush solution
   • Sterile caps/connectors

2. Perform hand hygiene and don sterile gloves 1

3. Prepare the PICC hub:

   • Disinfect the hub with chlorhexidine solution with alcohol 1
   • Allow the hub to dry completely before accessing (critical for preventing contamination)

Blood Drawing Procedure

1. Always draw a discard sample first (5-10 mL) to clear the line of any medications, parenteral nutrition, or heparin that could affect potassium results 1

2. After obtaining the discard sample:

   • Disconnect that syringe
   • Connect a new sterile syringe for the actual blood sample
   • Draw the required amount for potassium testing (typically 3-5 mL)

3. Transfer the blood sample to appropriate collection tubes immediately

4. Post-draw maintenance:

   • Flush the PICC line with 10-20 mL of normal saline 1
   • Resume any infusions that were temporarily stopped

Important Considerations

Preventing False Results

• Hemolysis can falsely elevate potassium levels - avoid excessive suction pressure when drawing samples
• If the PICC was used for parenteral nutrition, ensure adequate discard volume is drawn 1
• For patients receiving multiple incompatible infusions through a multi-lumen PICC, use the dedicated lumen for blood sampling 1

Line Maintenance

• Weekly flushing is recommended for PICC lines not in active use 1
• Use normal saline rather than heparin to maintain catheter patency 1
• Ensure proper documentation of the blood draw procedure

Contraindications and Special Populations

• For patients with chronic kidney disease stage 3b or worse (eGFR <45 mL/min), consider alternative access methods as preservation of upper extremity veins is critical 1, 2
• In patients receiving home parenteral nutrition, PICC lines may not be recommended for long-term use 1

Troubleshooting

If difficulty obtaining blood return:

1. Reposition the patient's arm
2. Have patient perform Valsalva maneuver
3. Consider a small (3-5 mL) normal saline flush if absolutely necessary, but this may affect lab results
4. Never forcefully flush a resistant PICC line

Following this protocol will help ensure accurate potassium results while maintaining the integrity of the PICC line and preventing complications such as infection or catheter occlusion.