19. Anesthesia for Orthopedic Surgery in Children
KeywordsAnesthesia forearm fracturesScoliosis surgery, anesthesiaAnesthesia cerebral palsy
Children commonly need anesthesia for orthopedic surgery, either urgently because of limb fractures in previously well children, or electively in children who often have coexisting diseases such as cerebral palsy or myopathies. These medical issues are dealt with elsewhere in this book, and this chapter focuses on issues unique to orthopedic surgery. It also outlines the management of anesthesia for scoliosis surgery, so that trainees who are involved with these cases will understand some of the background to their care.
19.1 Emergency Anesthesia for Forearm Fractures
Complete fracture-displacements may be reduced with a variety of techniques in either the ED or the OR. Many of the techniques require skill and patience to perform in frightened young children, and depend on local expertise, preferences and practical issues relating to staff and theatre availability. All of the techniques require proper monitoring, safety guidelines and ability to resuscitate the child if necessary.
Although fasting beforehand to ensure an empty stomach would seem wise, fasting requirements vary from center to center, depending on the anesthetic technique used. Many emergency departments accept fasting durations much shorter than those for anesthesia. The safety of intravenous sedation in the emergency department and the point at which sedation becomes anesthesia are controversial subjects. Nevertheless, general anesthesia is still very commonly used during fracture reduction because it always results in satisfactory conditions for the procedure and has a high level of safety.
19.1.1 General Anesthesia
Children needing surgery for a forearm fracture are usually fit and healthy, and pulmonary aspiration of stomach contents is the main concern. Evidence about minimizing the risk of aspiration for this procedure is scarce and anecdotal, and it would be simple to recommend rapid sequence induction and intubation for all cases. Rapid sequence induction however, is not without risks, does not entirely protect against aspiration, and can be technically challenging to perform for a brief procedure such as this. Although not formally studied, stratification of the risk of aspiration can be attempted by considering several factors. These include the fasting periods before and after injury, the amount of pain and use of opioid analgesics, the age and level of anxiety of the child, and presence of hunger or bowel sounds.
In children undergoing closed reduction of forearm fractures, experience shows children anesthetized with a facemask rarely vomit, even if they have significant stomach contents. This presupposes that an adequate depth of anesthesia is maintained during fracture manipulation to avoid any coughing, straining, or triggering a vomiting reflex. A laryngeal mask airway (LMA) is commonly used for this procedure, and it would seem prudent to use a second generation LMA with an esophageal drainage tube to mitigate the risk of gastric reflux. Intubation should still be considered for patients who are thought more likely to regurgitate. Identifying those children with a forearm fracture who are more likely to regurgitate relies on factors such as a short interval between food and injury, short fasting time or ongoing pain and opioid requirement. As discussed in Chap. 1, an inhalational induction may be an acceptable option even in this group of children when there is difficult venous access.
Fractures above the elbow (supracondylar fractures) are more painful, frequently require opioid analgesia, and tend to be brought to theater sooner than children with forearm fractures. These patients are more at risk of aspiration, and are more commonly intubated—possibly requiring a rapid sequence induction.
19.1.2 Compartment Syndrome
In adults, compartment syndrome is said to be associated with the five ‘P’s of symptoms (pain, paresthesia, paralysis, pallor, pulselessness). In young children, it is said to be associated with the three ‘A’s: anxiety, agitation and analgesia requirements that are increasing. Children are often unsettled after surgery and analgesia is increased in response, and compartment syndrome can easily be missed. It is particularly a concern after supracondylar and tibial fractures, but can occur after other orthopedic and non-orthopedic procedures. Regional analgesia using low concentrations of local anesthetic probably do not prevent the detection of compartment syndrome.
Children at increased risk of gastric aspiration for fracture manipulation include short interval between food and injury, children in more pain or with anxiety, opioid use and supracondylar fractures. Coughing while lightly anesthetized is the most likely mechanism for regurgitation and aspiration during facemask or LMA anesthesia.
19.2 Common Orthopedic Procedures
19.2.1 Procedures for Hip Dislocation and Dysplasia
Hip dislocation can occur in children for congenital reasons such as breech position in-utero, or for acquired reasons such as muscular imbalance around the hip joint. This can occur in children with neuromuscular disorders such as cerebral palsy. The femoral head can be immobilized in the acetabulum in infants using a SPICA cast. General anesthesia may be required for this. The child is positioned at the end of the theater bed and elevated on a box that allows the cast to be placed circumferentially from the umbilicus to the knees or feet. The cast must be applied to allow unimpaired abdominal movement. Because it is awkward to manipulate the airway while the infant is elevated on the box, tracheal intubation is often best.
Open surgical procedures for hip dislocation include the Salter pelvic osteotomy, and the varus de-rotational osteotomy (VDRO). Both procedures carry risks of significant blood loss, although rarely require transfusion. Post-operative pain and muscle spasms can be significant. Regional techniques, such as caudal block or a lumbar epidural are useful if not contraindicated. Sometimes a SPICA cast is applied, limiting access to an epidural site for inspection and catheter removal. If this is the case, a single-shot caudal and opioid infusion may be preferred. Muscle relaxants such as diazepam are useful for controlling spasm, but with caution as the child is also receiving opioids.
19.2.2 Procedures for Talipes Equino Varus
Talipes or ‘club foot’ can be managed with serial casting but surgically releasing the Achilles tendon is often required. This operation is commonly performed transcutaneously under either local or general anesthesia. Factors in considering the best approach to anesthesia include the age of the child, whether the procedure is unilateral or bilateral, and local practice. Local anesthesia for this procedure avoids exposure to general anesthesia and a possible risk of neurotoxicity, and fasting may be avoided. A local anesthetic cream can be applied to the medial side of the Achilles tendon before injection of a mixture of quick acting (lidocaine) and longer lasting (ropivacaine) local anesthetic. Care must be taken to calculate the maximum combined dose of local anesthetic. Other techniques such as awake spinal anesthesia have been described.
19.2.3 Slipped Upper Femoral Epiphysis (SUFE)
The upper femoral epiphysis is prone to subluxing on the femoral neck in adolescence, threatening the vascular supply of the femoral head. It is more common in obese children. The traditional surgery to stabilize the femoral head included placement of pins or screws through the femoral neck into the femoral head. This procedure is performed using a traction table, and anesthetic management requires consideration of the airway in patients with increased body mass, risk of aspiration, comorbidities such as obstructive sleep apnea, and post-operative pain. Femoral nerve blocks are useful for controlling post-op pain, in combination with multi-modal analgesia and the use of judicious doses of opioids. Some recent surgical techniques for the condition are more extensive and prolonged, but require similar anesthetic considerations.
19.3 Cerebral Palsy and Orthopedic Surgery
Orthopedic surgery is required by children with cerebral palsy for three main reasons—to correct hip dysplasia, to relieve limb contractures and improve posture, and to improve gait. Surgery often involves tenotomies, tendon transfers or osteotomies. Pain and muscle spasms can be significant issues after these procedures. Anesthetic care of children with cerebral palsy is discussed further in Chap. 12, Sect. 12.1.