Overview
Definition:
Arterial blood sampling (ABS) is a procedure to obtain arterial blood for analysis of blood gases, pH, and electrolytes
In children, this procedure can be inherently painful and anxiety-provoking, necessitating effective pain control strategies to ensure patient comfort, cooperation, and successful sample acquisition.
Epidemiology:
ABS is performed frequently in critically ill children in neonatal intensive care units (NICUs), pediatric intensive care units (PICUs), and emergency departments
The incidence varies with the severity of illness, with premature infants and neonates being more susceptible to pain due to immature nociceptive pathways and limited reserves.
Clinical Significance:
Accurate arterial blood gas (ABG) analysis is crucial for diagnosing and monitoring respiratory failure, metabolic disturbances, and circulatory compromise in children
Inadequate pain management during ABS can lead to physiological stress responses (tachycardia, hypertension, increased oxygen consumption), sample contamination, repeated attempts, and long-term negative impacts on the child's perception of healthcare.
Procedure Overview
Indications:
Assessment of oxygenation (PaO2), ventilation (PaCO2), and acid-base status
Evaluation of metabolic abnormalities
Monitoring of response to therapy
Detection of certain toxins.
Sites:
Radial artery is the most common site due to its superficial location and collateral circulation from the ulnar artery
Other sites include brachial artery, dorsalis pedis artery, and umbilical artery (in neonates).
Technique Considerations:
Aseptic technique is paramount
Proper patient positioning to optimize access
Adequate lighting
Collection of blood in a heparinized syringe
Avoidance of venous puncture
slow withdrawal of plunger to prevent flashback
Proper sample handling and transport to the lab.
Pain Assessment In Children
Importance:
Accurate pain assessment in non-verbal or pre-verbal children is challenging but essential for guiding effective interventions
Standardized, age-appropriate pain scales should be used consistently.
Neonates Infants:
Neonatal Infant Pain Scale (NIPS)
Facial expression (grimace), cry (acute, sustained), breathing patterns (irregular, groaning), arm/leg movements (stiff/jerky), arousal, and tone (deep/moderate).
Older Children:
Faces, Legs, Activity, Cry, Consolability (FLACC) scale for younger children
Wong-Baker FACES Pain Rating Scale or Numerical Rating Scale (NRS) for older, verbal children.
Physiological Indicators:
Heart rate, respiratory rate, blood pressure, and oxygen saturation can provide indirect evidence of pain or distress, but are less specific than behavioral scales.
Pain Control Strategies
Multimodal Approach:
Combining pharmacological and non-pharmacological methods is often most effective
The goal is to minimize pain and anxiety throughout the procedure.
Non Pharmacological Methods:
Swaddling (infants)
Pacifier with sucrose or glucose solution (neonates)
Kangaroo care (skin-to-skin contact)
Distraction techniques (stories, toys, videos)
Parental presence and reassurance
Environmental modifications (dim lights, quiet room).
Pharmacological Methods:
Local anesthesia (e.g., 1% lidocaine without epinephrine, infiltrated subcutaneously around the puncture site)
Topical anesthetics (e.g., EMLA cream – requires application 30-60 minutes prior to procedure)
Systemic analgesia (e.g., oral or intravenous acetaminophen, ibuprofen)
Procedural sedation (e.g., midazolam, ketamine, fentanyl) for particularly anxious or difficult procedures, especially in combination with analgesics.
Pharmacological Agents And Dosing
Topical Anesthetics:
EMLA cream (lidocaine 2.5%, prilocaine 2.5%): Apply generously to the puncture site and cover with an occlusive dressing 60 minutes prior
Onset of analgesia is 60-90 minutes
Contraindicated in G6PD deficiency and in neonates < 12 months.
Local Anesthetics:
Lidocaine 1% (without epinephrine): Inject 0.1-0.5 mL subcutaneously around the anticipated puncture site
Onset is rapid (within 1-2 minutes)
Duration is about 30-60 minutes
Aspirate to ensure intravascular injection is avoided.
Systemic Analgesics:
Acetaminophen: Oral dose 15 mg/kg every 4-6 hours
Intravenous dose 15 mg/kg every 6 hours
Ibuprofen: Oral dose 10 mg/kg every 6-8 hours
Fentanyl: IV dose 1-2 mcg/kg administered slowly, titrated to effect, for procedural pain during sedation.
Sedatives:
Midazolam: IV dose 0.05-0.2 mg/kg, titrate to effect
Ketamine: IV dose 0.5-1 mg/kg for dissociative anesthesia
Monitor cardiorespiratory status closely.
Challenges And Considerations
Neonatal Population:
Immature metabolic pathways and increased sensitivity to opioids and sedatives
Prioritize non-pharmacological methods and topical/local anesthetics
Monitor closely for respiratory depression and bradycardia.
Repeated Procedures:
Children undergoing frequent ABS may develop anticipatory anxiety and fear
Establishing trust, using a consistent approach, and providing adequate pain relief are crucial.
Sample Volume:
Adequate sample volume is essential for accurate results
Pain control can improve patient cooperation, leading to a successful single puncture and adequate sample volume, reducing the need for repeated attempts and further pain.
Adverse Events:
Potential adverse effects of pain control agents include local anesthetic toxicity, respiratory depression, hypotension, allergic reactions, and paradoxal excitation
Careful monitoring and prompt management of these events are necessary.
Key Points
Exam Focus:
DNB/NEET SS frequently tests knowledge of evidence-based pain management protocols for common pediatric procedures
Understand the principles of multimodal analgesia and when to use specific pharmacological agents.
Clinical Pearls:
Always assess pain before, during, and after the procedure using validated scales
The presence of a parent or guardian can significantly reduce anxiety
Adequate preparation and a calm demeanor of the healthcare provider are vital.
Common Mistakes:
Underestimating pediatric pain
Relying solely on one pain control method
Failing to monitor patients adequately after administration of analgesics or sedatives
Using epinephrine with local anesthetics in digits or extremities
Inadequate sample volume due to poor cooperation.