Umbilical Cord Blood Sampling
Umbilical Cord Blood Sampling in Neonates
Umbilical cord blood sampling is a crucial diagnostic procedure performed in neonates for various clinical indications, providing valuable information about the newborn's health status.
Key Indications
- Blood gas analysis for fetal acidosis
- Complete blood count evaluation
- Blood culture for suspected sepsis
- Metabolic and genetic studies
- Bilirubin levels
- Blood typing and Coombs testing
Advantages
- Non-invasive for the newborn
- Large volume of blood available
- Represents fetal status at delivery
- Multiple tests from single sampling
- Reduces need for venipuncture
Anatomical Considerations
Umbilical Cord Structure
- Vessels:
- One umbilical vein (oxygenated blood)
- Two umbilical arteries (deoxygenated blood)
- Vessel Identification:
- Vein: Larger lumen, thinner wall
- Arteries: Smaller lumen, thicker wall
- Arteries located closer to periphery
Timing Considerations
- Optimal sampling window: Within 60 minutes of delivery
- Blood gas analysis: Immediate sampling preferred
- Cord clamping effects on results
Sampling Procedure
Required Equipment
- Sterile gloves
- Antiseptic solution
- Appropriate collection tubes
- Heparinized syringes for blood gas
- Labels and requisition forms
- Clean scissors/clamps
Step-by-Step Technique
- Preparation:
- Verify patient identification
- Assemble all equipment
- Don sterile gloves
- Clean cord segment with antiseptic
- Arterial Sampling:
- Identify smaller arterial vessels
- Insert needle at 15-30° angle
- Apply gentle negative pressure
- Collect required volume
- Venous Sampling:
- Locate larger venous vessel
- Insert needle as above
- Collect sample with steady pressure
- Label specimens immediately
Special Considerations
- Order of collection tubes
- Minimum volume requirements
- Transport conditions
- Documentation requirements
Complications and Management
Common Issues
- Technical Difficulties:
- Vessel collapse
- Clotted specimens
- Insufficient volume
- Contamination
- Sample Quality Issues:
- Hemolysis
- Air bubbles in blood gas samples
- Delayed processing
Troubleshooting
- Unable to obtain sample:
- Try different cord segment
- Change needle angle
- Consider alternative sampling site
- Quality improvement strategies
- Documentation of difficulties
Result Interpretation
Blood Gas Analysis
- Normal Values:
- Arterial pH: 7.18-7.38
- Venous pH: 7.25-7.45
- Base excess: ±10 mEq/L
- pCO2: 35-70 mmHg (arterial)
- Interpretation Guidelines:
- Arterial-venous differences
- Metabolic vs respiratory components
- Clinical correlation
Other Common Tests
- Complete Blood Count:
- Hemoglobin: 14-20 g/dL
- Hematocrit: 42-60%
- WBC: 9,000-30,000/μL
- Blood Type and Antibodies
- Bilirubin Levels
