Fig. 17.1
A 14-year-old 25 kg severely disabled boy in severe pain. According to his mother, flexion of the toes is a typical sign of discomfort or pain
17.2.2 Specific Problems
Gastroesophageal reflux is relatively common among patients with CP and associated with an increased risk of pulmonary aspiration. The presence of scoliosis may restrict ventilation (Fig. 17.2), and these patients are also at high risk for pulmonary complications. Contractures and deformities have to be taken into account because they may significantly limit the possibilities to position the patient. Chronic constipation is common and may lead to rare, but typical, complications, such as superior mesenteric artery syndrome [12]. In addition, many of these patients have cognitive impairments that preclude cooperative behavior even in older children. In adult patients with CP sarcopenia, obesity and sedentary behavior will influence the perioperative course [13]; a lifelong health program is mandatory for these patients [14].
Fig. 17.2
A 15-year-old 12 kg girl scheduled for laparoscopic fundoplication. Positioning is a challenge. The correct position of the endotracheal tube was verified bronchoscopically
17.2.3 Spasticity
A big challenge in patients with CP is controlling spasticity and avoiding contractures. Pharmacologically, this is often attempted with compounds that modulate motor tone; e.g., benzodiazepines, baclofen, vigabatrin, or tizanidine. All these drugs have the potential to cause drowsiness and dose-dependent sedation.
Baclofen is structurally related to GABA. It can be administered orally or intrathecally. Especially after the first intrathecal trial injections, careful observation of the patient is mandatory [15]. Replacement of pumps is required every 5–7 years, and the pumps have to be refilled at least every 3 months. Baclofen should not be withdrawn abruptly as this can induce acute withdrawal symptoms.
Vigabatrin is primarily used as an antiepileptic agent; it is a GABA analogue that inhibits GABA metabolism.
Because of its structural similarity with clonidine, Tizanidine causes sedation, bradycardia, and hypotension in addition to myorelaxation. It is primarily metabolized by CYP1A2, and blocking this enzyme, e.g., by high doses of ciprofloxacin, may lead to excessive concentrations of tizanidine.
Botulinum toxin (Botox) is injected directly into the muscle and provides functional denervation lasting several months by preventing presynaptic acetylcholine release. In addition, Botox can be used in children with excessive salivation [16] or for controlling bladder detrusor hyperactivity.
Injections into the muscles or into the salivary gland are made under ultrasound control, most often in sedated or anesthetized children. Provided the total dose is restricted, severe adverse events are rare [17]. Reported adverse reactions are mostly related to the sedation procedure and not to the injected compound itself [18].
Neurolytic blocks (also called chemodenervation) are mainly suitable for nerves predominantly consisting of motor fibers, e.g., the obturator nerve in case of adductor spasm [19]. To perform these blocks, skilled anesthesiologists use nerve stimulation and ultrasound to identify nerve location. Today, neurolytic blocks have almost universally been replaced by intramuscular Botox injections. However, selective neurolytic nerve blocks using phenol (5–12 % solutions) may still have a place as they provide relief for a period of 4–8 months [20]. Alcohol may be an alternative to phenol for neurolysis [21].
17.2.4 Epilepsy
Up to 30 % of patients with CP have coexisting epilepsy. Perioperatively, seizure frequency and duration can be increased because factors enhancing seizure activity, such as stress, starvation, sleep deprivation, optical stimulation, and hyperventilation, may be unavoidable. On the other hand, most, if not all, anesthetics protect against convulsive activity [22]. With uninterrupted antiepileptic medication and good clinical care, increased seizure activity should rarely occur [23].
Valproic acid has been associated with severe bleeding complications [24]. The mechanisms involved are only poorly understood, but thrombocytopenia and platelet dysfunction, as well as deficiencies of several coagulation factors, such as fibrinogen, factor XIII, and especially von Willebrand factor type 1, have been implied [25, 26]. Preoperative coagulation tests are suggested for children who are on long-term medication with valproic acid [25]. Another severe complication of valproic acid use is acute pancreatitis [27].
17.3 Perioperative Management
17.3.1 Positioning and Venous Access
Positioning can be very demanding for obvious reasons; often, an inventive spirit is needed. Meticulous padding as well as small adjustments in position of all accessible body parts (e.g., arms, head) is key to avoid pressure sores during prolonged surgery. Severely handicapped children may be at high risk to sustain long bone fractures simply through unskilled positioning.
17.3.2 Airway Management
Endotracheal intubation is strongly recommended for children with gastroesophageal reflux and prolonged surgery. On the other hand, for many children with cerebral palsy and no history of reflux, a laryngeal mask airway (LMA) with a gastric access, e.g., LMA Supreme® or LMA ProSeal®, can be a valuable airway tool. In case of scoliosis and severe deformity, optimal positioning for intubation can be challenging, even if the airway itself is normal. Often, the length of the trachea may not be as long as expected for age, and auscultation may not reliably allow identifying bronchial main stem intubation. It is the authors’ practice to use fiberoptic control liberally to verify the correct position of the tip of the endotracheal tube.
Intermittent airway obstruction may occur in some patients with CP – even without anesthesia – because of hypotonia of the pharyngeal muscles; the symptoms tend to become worse with increasing age [30] and ultimately may lead to a tracheostomy in some patients. Perioperatively, special attention must be paid to avoid anesthetic overhang or benzodiazepine medication. During mask induction, the skilled practitioner will generally be able to maintain an open airway with jaw thrust and positive airway pressure.
17.3.3 Thermal Homeostasis
Hypothermia is the most common perioperative complication in children with CP [4]. The etiology is probably multifactorial: undoubtedly, the most important factor in its pathogenesis is a reduced metabolic rate (“vita reducta”) coupled with exaggerated losses due to exposure of large areas of the body necessary for many orthopedic interventions. In addition, these patients often have very little subcutaneous fat tissue to insulate against heat loss. Finally, it has been speculated that there may be abnormal thermoregulatory mechanisms in patients with a compromised central nervous system.
Forced air systems (e.g., Bair Hugger®) are successfully used to prevent perioperative hypothermia. In addition to an elevated room temperature, the authors use two forced air systems in vulnerable patients: one on which the patient is placed and one that covers the body surface as much as possible. Continuous monitoring of the patient’s body temperature using rectal, esophageal, or bladder temperature probes is advisable. With the appropriate use of modern equipment, hypothermia can almost invariably be prevented.
17.3.4 Pharmacodynamics and Pharmacokinetics
Hypnotics: Patients with CP, as well as many other severely handicapped children, seem to be much more sensible to hypnotic agents. Frei et al. reported that the MAC values of halothane are reduced by around 1/3 in children with CP [31]. This is clearly a pharmacodynamic phenomenon: a lower concentration is needed for a certain effect. Similarly, less propofol is needed to reach a target BIS value of 40 [32]. This may also be caused by an altered pharmacodynamic response; however, different pharmacokinetics may also be responsible. Lower BIS values are recorded in children with cerebral palsy while awake, as well as after exposure to different sevoflurane concentrations [33]. Other authors, however, have found similar BIS values before induction among patients with CP when compared with healthy children [34]. The reduced requirement for hypnotic agents seems to be a common phenomenon for most, if not all, severely handicapped children [35]. It is the authors’ practice to monitor the hypnotic state with an EEG-based monitor, i.e., bispectral index (BIS®), in all of these patients despite the fact that the validity of these monitors has not been tested extensively in this patient population, and an individual patient may well present with a very low BIS® value before anesthesia induction.
Opioids: Only limited information is available about the sensitivity to opioids in patients with CP. It has been speculated that chronic hypoxia increases the sensitivity to opioids, especially to the respiratory depressant effects of opioids [36]. Children living in high altitude exposed to chronic hypoxic conditions seem to require less opioids after surgery for sufficient pain relief [37]. Typically, increased sensitivity to opioids is discussed in the context of obstructive sleep apnea [38] where it is associated with relevant morbidity and even mortality [39]. There is little doubt that similar phenomena can be found in children with CP; intermittent nocturnal desaturations up-regulate endorphin receptors and enhance sensitivity to opioids [40]. Therefore, careful dosing and adequate monitoring is very important in this patient population.
Neuromuscular blocking agents: Surprisingly, children with CP, despite the fact that they often have a very reduced muscle mass (Fig. 17.3), seem to be resistant to non-depolarizing neuromuscular blocking agents. Clinically, a given dose has a shorter duration of action [41]. This resistance does not appear to be related to concomitant use of antiepileptic medication [42]. Receptor up-regulation seems to be a suitable explanation. This also explains the increased sensitivity to succinylcholine [43]. Hyperkalemia does not seem to be a problem, likely due to a reduced muscular mass [44]. Despite the fact that the airway is usually normal, difficult intubation is reported to be more common in severely handicapped patients; insufficient doses of non-depolarizing neuromuscular blocking agents may be at least in part responsible in some cases. Given the availability of sugammadex, higher doses of rocuronium, which provide excellent intubation conditions, have become an attractive option in patients with CP or other neuromuscular disorders [45].
Fig. 17.3
Despite severe muscular hypotrophy, this boy is remarkably resistant to atracurium
17.3.5 Uncooperative Behavior at Induction
The preoperative visit is of paramount importance; patients at risk for a stormy and difficult induction should then be recognized. The parents should be asked about and charts be scrutinized for information concerning previous anesthetics; it is the authors’ practice to leave a note in the anesthesia chart on the sedative effects of the premedication and the quality of induction.
Prevention of difficult inductions by using an adequate premedication is of paramount importance. It is the authors’ practice to add ketamine to midazolam if relevant uncooperative behavior can be anticipated [46]. Often, a peaceful induction can be achieved by gentle conviction of the patient and parental support. In addition, success is highly dependent on the skill and empathy of the anesthesiologist. Inhalation of nitrous oxide followed by sevoflurane using a flavored mask while the child is in his/her preferred position is a good option. In the authors’ institution, an uncooperative child is usually left in his/her hospital bed for induction [47].
The management of uncooperative behavior at induction includes several options: postponing surgery, top-up premedication with ketamine, skilful inhalational or intravenous induction using persuasion, and sometimes gentle physical restraint are all valuable options. The choice of a particular method will depend on the individual practitioner: extensive experience with pediatric patients, appropriate skills, as well as empathy with the child and the parents are key factors for success. Often, only a detailed discussion with the parents can disclose the optimal solution for the individual patient. The authors have induced anesthesia in children sitting on the floor in the corridor in front of the operating theatre refusing to enter it. In one child, refusing to enter the hospital, anesthesia was even induced on the street in front of the hospital. Without doubt, the safest drug under these circumstances is ketamine.
17.3.6 Postoperative Analgesia
In patients with CP, pain is not restricted to the perioperative period but rather a predominant symptom [48]; up to 75 % of young people with CP experience some pain in a typical week [49]. Possibly as a consequence, pain appears to be more difficult to treat in this patient population. A first challenge is to recognize whether the patient is in pain. It is likely that pain is often undertreated in these patients [50]. On the other hand, because of the difficulties to distinguish pain and other causes of agitation, overdosing with oversedation can easily occur.
Whenever possible, regional blocks are probably the most elegant way to provide reliable analgesia in these vulnerable patients; continuous epidural analgesia may be considered after major surgery, especially in conditions where spasms of the muscles of the lower extremities can be expected [51].
17.4 Typical Interventions
17.4.1 Orthopedic Surgery
Major orthopedic surgery is commonly undertaken in children with CP [52]. Scoliosis surgery is often extensive involving segments from the high thoracic region down to the sacrum, and pelvic stabilization will assist in sitting. Intraoperative monitoring has become commonplace [53]. Postoperative pain relief is challenging; intrathecal morphine can easily be administered [54], enhances perioperative stability, and thus may reduce blood loss [55]. Epidural catheters, positioned intraoperatively by the surgeons, have also been successfully used [56].
Hip reconstruction involving pelvic and femoral osteotomies is offered even to the most debilitated children with the aim to reduce pain, to facilitate positioning, and even occasionally to allow a sitting position. Palliative surgery, e.g., resection of the femoral head, is nowadays only rarely performed [57]. Postoperative pain relief can be provided through lumbar epidural catheters; in the authors’ practice, however, caudal morphine combined with peripheral nerve blocks, e.g., lumbar plexus [58] or femoral and/or sciatic nerve blocks, are often used.
Blood loss can be major. Antifibrinolytic agents, e.g., tranexamic acid, are recommended by most authorities to reduce blood loss [59]; its effectiveness has been specifically shown in cerebral palsy scoliosis too [60]. However, the pediatric data covering other types of surgery are still very limited [61].
17.4.2 Fundoplication and Gastrostomy
Nissen fundoplication is considered as the treatment of choice for children with gastroesophageal reflux disease. Laparoscopic Nissen fundoplication is offered today as the standard procedure, although the evidence of its superiority over open surgery is limited [64]. The technique involves prolonged pneumoperitoneum with the patient in a head-up position [65]. Ventilation and PEEP have to be adapted to counteract the effects of the elevated intra-abdominal pressure. Pneumothorax can occur by transition of CO2 from the abdominal cavity to the pleural space through lesions caused by dissection; generally, no specific treatment is required provided that a sufficiently high PEEP level is maintained [66]. Hemodynamic monitoring is crucial; the critical phases are the creation of the pneumoperitoneum as well as its release at the end of surgery. The patients usually develop a transient oliguric state during the period with elevated intra-abdominal pressure [67]; there is some consensus that this does not require aggressive treatment.