How is prilocaine cream used for cannulation?

Prilocaine Cream for Cannulation

For intravenous cannulation, apply 2.5 grams of lidocaine-prilocaine cream (EMLA) to intact skin over 20-25 cm² and cover with an occlusive dressing for at least 1 hour before the procedure. 1

Application Technique

Dosing and Timing

• Apply 2.5 grams (half of a 5g tube) of 2.5%/2.5% lidocaine-prilocaine cream over 20-25 cm² of skin surface 1
• Cover with an occlusive dressing and allow at least 1 hour of contact time before cannulation 1
• Dermal analgesia increases for up to 3 hours under occlusive dressing and persists for 1-2 hours after cream removal 1
• In clinical practice, preparing two sites is recommended in case of technical difficulties at the first cannulation attempt 1

Age-Specific Restrictions and Dosing

Neonates and infants require special precautions due to methemoglobinemia risk:

• Do NOT use in infants <12 months who are receiving methemoglobin-inducing agents (e.g., acetaminophen, sulfonamides, antimalarials) 2, 1
• Do NOT use in neonates with gestational age <37 weeks 1
• For infants 0-3 months or <5 kg: maximum 1g over 10 cm² for 1 hour 1
• For infants 3-12 months and >5 kg: maximum 2g over 20 cm² for 4 hours 1
• For children 1-6 years and >10 kg: maximum 10g over 100 cm² for 4 hours 1
• For children 7-12 years and >20 kg: maximum 20g over 200 cm² for 4 hours 1

Clinical Efficacy Evidence

Pain Reduction

Lidocaine-prilocaine cream provides superior pain relief compared to local infiltration for arterial cannulation:

• In a randomized trial of 538 adults undergoing radial artery cannulation, EMLA reduced pain scores significantly (2 vs 7 on a 0-10 scale, P=0.0001) compared to lidocaine infiltration 3
• EMLA applied 90 minutes prior to radial artery cannulation produced significantly less pain (P<0.001) than either 60-minute application or immediate lidocaine infiltration 4
• Additional lidocaine infiltration was required significantly less frequently with EMLA (relative risk 0.19) 3

Success Rate and Procedure Time

• Cannulation failure rate was significantly lower with EMLA (relative risk 0.38) 3
• Insertion time was shorter with EMLA (4 vs 6 minutes) 3
• In vaccination studies, pretreatment 30-60 minutes before injection with 5% topical lidocaine-prilocaine emulsion decreased pain among infants by causing superficial anesthesia 2

Important Safety Considerations

Methemoglobinemia Risk

The prilocaine component can cause methemoglobinemia through its metabolite ortho-toluidine:

• Very young patients, those with glucose-6-phosphate dehydrogenase deficiencies, and patients taking oxidizing drugs (antimalarials, sulfonamides) are more susceptible 2
• Acetaminophen can cause methemoglobin formation and may interact with lidocaine-prilocaine cream if used concurrently 2
• Use ibuprofen or other non-aspirin analgesics instead if concurrent pain medication is needed 2
• Risks can be minimized by using no more than once daily, on intact skin only, and avoiding concurrent methemoglobin-inducing drugs 2

Application Site Requirements

• Apply only to intact skin - topical anesthetics are not effective for heel-stick blood draws because pain is primarily from squeezing the heel, not the lancet 2
• Occlusion is necessary for optimal absorption on intact skin 1
• Local side effects (transient blanching, erythema, edema) are mild and transient 1, 5

Practical Implementation

Preparation Steps

• Apply cream 1 hour before venous access to reduce pain and anxiety 2
• Use appropriate occlusive dressing to maintain contact and enhance absorption 1
• Perform cannulation immediately after removing the cream for optimal anesthetic effect 1
• In pediatric patients, careful observation is required to prevent accidental ingestion of cream or disruption of the occlusive dressing 1

Common Pitfalls to Avoid

• Insufficient application time - at least 60 minutes is required, with 90 minutes providing superior analgesia 4
• Using in contraindicated populations - avoid in infants <12 months on methemoglobin-inducing agents and neonates <37 weeks gestational age 1
• Inadequate coverage area - ensure 20-25 cm² coverage for venipuncture sites 1
• Concurrent use with acetaminophen - increases methemoglobinemia risk; use ibuprofen instead 2