Local Anesthetics in Children
By Steven J. Weisman, MD
The local anesthetics have a broad range of applicability in pediatric patients. When used appropriately, they clearly contribute to easing the suffering children experience during the evaluation of or treatment of many diseases. The scope of clinical usefulness of local anesthetics is so broad that I will only review cutaneous analgesia.
Although EMLA cream (eutectic mixture of local anesthetics) has been studied in clinical use for more than 10 years, it has remained a grossly underused mode of local anesthesia in children. Recent reports describing its usefulness in newborn boys undergoing circumcision served as the stimulus for the review of the topic of cutaneous anesthesia/analgesia in children.1
EMLA cream can be easily and safely used to prevent procedure pain in almost every imaginable clinical situation in children. I suspect the single greatest impediment to its widespread use remains the caretakers’ innocent forgetfulness. In the fast-paced world of many pediatric practice settings, it can be difficult or cumbersome to find the 60 minutes needed to apply the cream before a procedure. Others suggest that the cost of the medication prohibits universal use. In many other countries, including Canada, EMLA is available as an over-the-counter medication and also in an easy-to-apply patch form. A combination of both the increased professional sensibility of the need to reduce pain in children and the increased awareness of the possibilities available to reduce pain may lead to more widespread use of agents such as EMLA cream.
In children with chronic illnesses, EMLA has been shown to be effective in preventing or reducing discomfort from a variety of procedures including lumbar punctures and subcutaneous port access.2 EMLA has been successfully employed to reduce the pain of venipuncture in children.3 Port-wine stain removal, in addition to other purely dermatologic procedures, has been facilitated by the use of EMLA.4 The discomfort from immunizations is also reduced with application of EMLA cream.
Taddio and colleagues, in a double-blind, randomized, controlled trial in 68 infants, demonstrated the safety and efficacy of EMLA cream for the prevention of pain from circumcision.5 The treated infants cried less and had a smaller increase in heart rate during the procedure. In addition, these investigators found no differences in methemoglobin levels between the treatment and placebo groups. This study confirmed efficacy and also included carefully collected methemoglobin safety data. Other intriguing work by Taddio et al suggests that children with poorly controlled pain during circumcision go on to demonstrate increased pain and pain behaviors with subsequent immunizations.6
Although not yet approved for use in children under six months of age, EMLA has been studied as indicated above for circumcision as well as for more general use in neonates who undergo repeated painful procedures, such as heel sticks.
Local anesthetics can be delivered by other mechanisms to induce cutaneous analgesia in children. The "gold standard" has been via injection. However, the discomfort of such injections has discouraged many practitioners from adopting this technique. Most of the discomfort from cutaneous infiltration is due to the low pH of the local anesthetic solution. Several investigators have reported that pH buffering of the injectate will eliminate virtually all of the reported discomfort.6 I currently employ 1% lidocaine (9 parts) buffered with standard sodium bicarbonate solution (1 part) for all such infiltrations. In fact, at the Children’s Hospital at Yale-New Haven, the pharmacy prepares buffered lidocaine in multidose vials for general use. Use of a 27-30 g needle will also minimize the discomfort. The use of air-pressurized injectors can also be considered, but these devices are painful and carry a small risk of bloodborne infection spread.
Several other transcutaneous methods are currently available for anesthetizing the skin. Iontophoresis, which employs a small amount of electrical current to drive local anesthetic into the skin, does require specialized equipment but has the advantage of developing cutaneous analgesia in 10 minutes of application. Amethocaine (tetracaine hydrochloride) gel has been used both as a patch and as a "mount" with an occlusive dressing virtually identical to the use of EMLA for venous cannulation in adults and children. This method is not yet available for use in the United States.
The final commonly available method for achieving cutaneous analgesia involves application of a mixture of local anesthetics and vasoconstrictors to open wounds.7 Tetracaine-adrenaline-cocaine (TAC) has been used as a solution or a gel to be applied to lacerations prior to suturing. Unfortunately, fatalities (probably related to cocaine absorption) have been reported. Investigators now propose substitution of the cocaine with lidocaine, which appears to provide similar anesthesia levels.
In conclusion, multiple techniques for providing cutaneous analgesia are readily available for clinical use in children. There is no evidence to support the popular myth that infiltration is viewed by children as badly as the actual procedure to be completed. The spirit of compassionate care for children undergoing painful procedures must prevail so that the clinician adopts some, if not all, of the techniques discussed for delivery of local anesthetics for cutaneous anesthesia in children. (Dr. Weisman is Associate Professor of Anesthesiology and Pediatrics and Director of the Pediatric Pain Service at Yale University School of Medicine.)
References
1. Taddio A, et al. Efficacy and safety of lidocaine-prilocaine cream for pain during circumcision. N Engl J Med 1997;336:1197-1201.
2. Halperin DL, et al. Topical skin anesthesia for venous, subcutaneous drug reservoir and lumbar punctures in children. Pediatrics 1989;84:281-284.
3. Robieux I, et al. Assessing pain and analgesia with a lidocaine-prilocaine emulsion in infants and toddlers during venipuncture. J Pediatr 1991;118:971-973.
4. Sherwood KA. The use of topical anesthesia in removal of port-wine stains in children. J Pediatr 1993;122: S36-S41.
5. Taddio A, et al. Effect of neonatal circumcision on pain responses during vaccination in boys. Lancet 1995; 345:291-292.
6. Christoph RA, et al. Pain reduction in local anesthetic administration through pH buffering. Ann Emerg Med 1988;17:177-181.
7. McCafferty DF, et al. New patch delivery system for percutaneous local anaesthesia. Br J Anaesth 1993; 71:370-374.
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