Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

44.General Considerations for Pediatric Peripheral Blocks

Giorgio Ivani

Valeria Mossetti

Many factors have contributed to the wide diffusion of regional anesthesia in children: the awareness of pain and the subsequent need for adequate pain relief at any age—from premature babies to adolescents—the demonstration of the efficacy of regional anesthesia in controlling stress, the vast amount of information coming from congresses, and books and papers on this topic. Notwithstanding the criticism surrounding the use of a “double anesthesia” (most blocks in children require sedation or light anesthesia before performing the block) with the supposed “double risk,” evidence from the world of pediatric anesthesia has demonstrated that regional anaesthesia in children is safe. Safety depends on experience and adequate guidelines, but also on the choice of drugs, whose main characteristic must be a reduced toxicity, and on a multimodal approach, which allows low concentrations of multiple drugs for a synergistic action. Some regional blocks, such as caudal blocks, epidural blocks, or penile blocks, have already an established place in pediatric anesthesia, mainly as techniques of postoperative analgesia. Peripheral nerve blocks are not yet as popular but the interest in this technique is growing due to their safety, efficacy, and well-limited localization of analgesia/anesthesia.

Regional anesthesia performed on children presents some differences to that performed on adults because of particular pediatric issues; therefore, to perform peripheral blocks in children some differences from the practice in adults should be considered.

Anatomy

The first obvious anatomic difference between adults and children is the size of the patient; therefore the practitioner must locate peripheral nerves with slow movements and use micro adjustments for precision. Another difference is linked to the anatomic landmarks because the anatomic relationships vary depending on age; moreover, the bony growth is not the same for long, short, or flat bones, and the variations of body fluids affect skin thickness. Therefore, the length of the needle should be the shortest that can easily reach the nerve to be blocked. Despite the potential difficulties that may arise from the anatomic differences in children, there are also anatomic benefits that are offered in the developing child. One such benefit is the ease with which nerves are blocked by local anesthetics due to their thin myelin sheaths, small fiber diameter, and short internodal distances. This allows lower concentrations of local anesthetic to produce an adequate surgical block in infants and younger children. On the other hand, this may lead to an increased risk of toxicity if the dose is not appropriately adjusted. Another anatomic benefit in the pediatric patient is the presence of loose connective tissue around neuroaxial structures centrally, and nerve sheaths that are only loosely attached to the nerve trunks peripherally. These factors should lead to an improved spread of local anesthetic without the dense anatomic barriers that may be present in adults.

Pharmacology

We must consider that in newborns and children there is a lower level of alpha-1-glicoprotein, which means a higher fraction of free local anesthetic. There are also considerable individual variations and little information concerning diffusion, protein binding, and local metabolism; moreover, local spread is easier in children because of the age-related increase in cardiac output and regional blood flow, and fat is less dense. As in adults, absorption depends on the site of injection and increases in the following order: proximal nerve blocks of the lower extremities, brachial plexus blocks, caudal blocks, epidural blocks, intercostal blocks, and topical laryngeal applications.

Assessment of Pain

It is difficult to evaluate pain in newborns, infants, preverbal age, or impaired children. The verbal and visual understanding is limited but pain can be identified through observational items: crying, facial expression, posture of the trunk, posture of the legs, and motor restlessness. For older children, pain can be assessed through the Faces Pain Rating Scale, a pictogram of six faces with different expressions from smiling or happy through to tearful.

Combined Regional and General Anesthesia

Children have fear of needles, and any performance of a block on a screaming, moving child is not only unethical, but could be dangerous when the needle approaches the delicate neural structures. It is therefore mandatory to associate most regional block procedures with general anesthesia. But performing a block on a deeply sedated child could be dangerous as well: any warning signals that something is going wrong could be easily missed. Therefore, deep anesthesia should be avoided before the performance of a block; a light general anesthesia, without muscle relaxation or injection of narcotic, guarantees immobility and avoids the dangerous untoward effects related to respiratory and circulatory failures as well as the adverse events that could result from a faulty technique, such as excruciating pain, convulsions, or tachycardia.