Anesthesia and Analgesia for the Ambulatory Management of Children’s Fractures

Techniques to be Avoided

Vocal, or “O.K,” anesthesia is a technique that provides only the verbal assurance to the child that the manipulation of the fracture will be briefly painful. The concept that children are somehow more resilient to pain has been disproved as knowledge of the developmental and psychological makeup of children and their perception of pain has become better understood. The notion that it is acceptable for children to endure pain during the performance of therapeutic or diagnostic procedures has become dated with the evolution of techniques in pediatric pain management. Given the availability of many safe and effective options for pain management during the reduction of children’s fractures, the technique of “verbal reassurance” should be avoided if possible.

Chloral hydrate and the so-called lytic cocktail, a combination of meperidine (Demerol), promethazine (Phenergan), and chlorpromazine (Thorazine) (DPT), two techniques of sedation used frequently in the past, have fallen out of favor. Chloral hydrate was introduced in 1832 and was used commonly for children undergoing painless diagnostic procedures. Although it has been demonstrated to be effective for the sedation of young children (<6 years of age) undergoing therapeutic procedures, it has several disadvantages for the management of fractures in children. The onset of sedation is slow (40–60 minutes), and recovery can be prolonged, taking up to several hours, with residual effects lasting as long as 24 hours. Moreover, chloral hydrate has no analgesic properties, and children can become disinhibited and agitated in response to painful stimuli. For these reasons, chloral hydrate is not a preferred technique for sedation in the management of fractures in children.

DPT has been the second most commonly used method of sedation for children undergoing painless diagnostic tests and the one most widely used in children undergoing therapeutic procedures since 1989. DPT is typically administered in a single intramuscular (IM) injection and provides sedation with some analgesia.

Despite widespread usage, the drugs in the lytic cocktail have many undesirable characteristics. The combination is poorly titrated and has a delayed onset of action (20–30 minutes). The duration of sedation can last 20 hours, but the duration of analgesia is only 1 to 3 hours. The mixture does not have any anxiolytic or amnestic properties. Recently, it was demonstrated that the DPT cocktail is a largely empiric mixture of three drugs, not based on sound pharmacologic data, with a relatively frequent occurrence of therapeutic failure (29%) and a relatively high rate (approximately 4%) of serious adverse effects such as seizures, respiratory depression, and death. For these reasons, the use of DPT is discouraged by both the US Agency for Health Care Policy and Research and the AAP.

Local and Regional Anesthesia

Local anesthetics work by blocking the conduction of nerve impulses. At the cellular level, they depress sodium ion flux across the nerve cell membrane and, in this way, inhibit the initiation and propagation of action potentials. After injection, local anesthetics diffuse toward their intended site of action and also toward nearby vasculature, where uptake is determined by the number of capillaries, the local blood flow, and the affinity of the drug for the tissues. Elimination occurs after vascular uptake by metabolism in the plasma or liver. Vasoconstrictors such as epinephrine are mixed with local anesthetics to decrease the vascular uptake and prolong the anesthetic effect.

Local anesthetics are classified chemically as either amines or esters ( Table 21.1 ). After absorption in the blood, esters are broken down by plasma cholinesterase, but amides are bound by plasma proteins and are then metabolized in the liver. Local adverse effects include erythema, swelling, and, rarely, ischemia when injected into tissues supplied by terminal arteries. Adverse systemic effects are caused by high blood levels of local anesthetics and include tinnitus, drowsiness, visual disturbances, muscle twitching, seizures, respiratory depression, and cardiac arrest. Bupivacaine is a long-acting amide that is particularly dangerous because it binds with high affinity to myocardial contractile proteins and can cause cardiac arrest. Ropivacaine, which is closely related to bupivacaine structurally, is a newer long-acting amide that, at clinically relevant doses, provides a greater sensorimotor differential block, has an increased cardiovascular safety profile, and has a shorter elimination half-life with lower potential for accumulation than bupivacaine. The lower systemic toxicity and cardiotoxicity is desirable when the potential exists for high plasma concentrations of local anesthetics, such as in peripheral nerve blocks or after inadvertent intravascular injections.

A number of local and regional techniques, including hematoma, IV regional, and regional nerve blocks, have been reported to be variably effective in providing anesthesia for fracture treatment in children. These methods require the surgeon to be familiar with regional anatomy, have working knowledge of the pharmacokinetics and dosing of local anesthetic drugs, and be proficient in the techniques of administering them. Compared with the performance of these techniques in adults, the performance of these techniques in children is often technically easier because anatomic landmarks are more readily identifiable. Physiologically, the relatively smaller calibers of the peripheral nerves in children are more susceptible to the pharmacologic actions of anesthetic agents.

Hematoma Block

The hematoma block has been a popular method of anesthesia for the reduction of fractures, particularly in the distal radius but also about the ankle. In this technique, a local anesthetic agent is injected directly into the hematoma surrounding the fracture. The anesthetic inhibits the generation and conduction of painful impulses primarily in small nonmyelinated nerve fibers in the periosteum and local tissues. This block is quick and relatively simple to administer. The skin is prepared with a bactericidal agent and draped at the site of infiltration. The fracture hematoma is aspirated with a 20- or 22-gauge needle and then injected with plain lidocaine. The typical dose of lidocaine is 3 to 5 mg/kg, which should be concentrated so as to limit the total amount of fluid injected to less than 10 mL; limiting the fluid will avoid elevating soft tissue compartment pressures and minimize the risk of creating a compartment syndrome or other neurovascular problem. Although direct injection of the hematoma theoretically converts a closed fracture into an open one, no infections have been reported with this technique.

Recent studies of hematoma blocks administered to children have shown its safety and efficacy. Studies have shown parental satisfaction and shorter length of stays in the emergency department. In three separate studies authored by Dinley and Michelinakis, Case, and Johnson and Noffsinger with a combined total of 491 adult and pediatric patients, hematoma block was shown to be effective for the reduction of a variety of fractures of the distal upper extremity in patients of all ages. Despite the generally favorable experience with hematoma block anesthesia, other methods of regional anesthesia have been shown to be more effective for the management of upper extremity fractures. A study by Abbaszadegan and Johnson found that analgesia during fracture reduction was superior with IV regional (Bier block) anesthesia compared with hematoma block and that fracture alignment after reduction was also better. The authors concluded that the more favorable outcomes achieved with the Bier block were related to better analgesia and muscle relaxation.