pediatric blood draw limits: how much is safe

by Neoteryx Microsampling on Sep 5, 2018 3:03:00 AM

In pediatric studies, understanding the challenge of blood draws in children is crucial. The safety and well-being of our youngest study cohorts is critical.

The blood volume in children, especially in infants, is significantly lower than in adults. This makes the procedure of drawing blood a delicate matter.

In this article, you'll learn safe pediatric blood draw limits and volumes for infants and children, ensuring best practices are followed to protect young patients.

How Much Blood Can You Safely Draw

According to established pediatric blood draw guidelines, determining the safe limit for a blood draw is predominantly dictated by the age and weight of the child.:

• Total Blood Volume (TBV) and Age: Understanding blood volume in infants is crucial; neonates typically have approximately 85–90 mL/kg of body weight, while older children might have around 70 mL/kg. This knowledge is essential when determining safe blood draw volumes.  This varying blood volume underscores the need for age-specific care during blood draws.
  
  
• Safe Draw Limits: Multiple studies and guidelines suggest that for infants and children, the maximum amount of blood drawn within a 24-hour window should range between 1% and 5% of their TBV. However, the gold standard is to keep it under 3% of the TBV. Advances like microsampling make adhering to these low percentages more achievable. It's noteworthy that for sick children, this limit is even more stringent at 3.8% of TBV within a day. Over a more extended period, such as eight weeks, only up to 10% of the TBV should be drawn.

 

Why The Blood Volume Limitations?

Excessive or frequent blood draws, especially in a short timeframe, can lead to iatrogenic anemia, where the patient becomes anemic due to medical intervention. In neonates and critically ill children, this risk is heightened.

Anemia can have a range of detrimental effects, including increased cardiac workload, hindered oxygen delivery to tissues, and potential developmental complications. Other Challenges in Pediatric Blood Draws include:

1. Smaller Veins: Children's veins are smaller and can be more difficult to access.
2. Anxiety and Fear: Many children are scared of needles, making the procedure more traumatic for them than for adults.
3. Limited Volume: Due to the limited amount of blood that can be drawn, there's a need to ensure that samples are properly handled, especially if multiple tests are required.

 

How Children Experience Venipuncture

For many children, the experience of a venipuncture blood draw can be frightening and traumatic. Young children process pain differently than adults — both neurologically and emotionally.

Studies suggest that children may even perceive pain more intensely, and emotionally, they lack the cognitive tools to contextualize or rationalize medical procedures. To a child, a needle in the arm can feel like an incomprehensible threat.

Beyond the emotional stress, practical challenges also exist. Children's veins are smaller and often buried beneath a protective layer of subcutaneous fat, making them difficult to locate and access.

Finding a suitable vein can take time and may require multiple attempts, which heightens distress. In some cases, physical restraint may be used to complete the blood draw, further compounding the child’s fear and anxiety.

Use Dried Blood Micro Samples as an Alternative

Microsampling provides a far less intimidating alternative. A quick finger-stick or heel-stick typically causes only brief discomfort—so brief, in fact, that many children don’t cry at all.

Instead of vials, the tiny blood sample is absorbed into a small device for lab analysis. This minimally invasive method not only reduces physical pain, but also avoids the psychological burden often associated with traditional blood draws, making it a more compassionate choice for pediatric care.

Advantages of Capillary Blood Sampling

1. Simplicity: The method requires minimal skills, making the collection straightforward.
   
   
2. Less Traumatic: Vein detection can be challenging and traumatic for both the technician and the infant. Capillary blood sampling with a finger-stick or heel-stick doesn't require searching for a vein in the arm, which alleviates much stress.
   
   
3. Minimal Invasiveness: Compared to venipuncture, this method is far less invasive.
   
   
4. Safety: Given that only a minimal amount of blood is collected, it inherently becomes a safer option for children.
   

Microsampling as a Way Forward for Pediatrics

Healthcare professionals and researchers dealing with pediatric patients must be adept in understanding the safe thresholds for blood draws. Given the multiple tests a child may undergo, especially in clinical trials or other studies, it's crucial to account for the cumulative amount of blood drawn.

A steadfast commitment to blood draw guidelines is indispensable. Yes, obtaining blood samples is vital for precise monitoring and medical treatment, but we should also prioritize the child's wellbeing.

Thanks to breakthroughs in microsampling techniques and bioanalytical instruments, the quantity of blood needed for analysis has been significantly reduced.

Embracing less invasive methods like capillary blood microsampling to abide by pediatric blood draw limits strikes a balance between medical and research imperatives and the blood sampling experience for pediatric patients and study cohorts.