A considerable proportion of children who undergo elective orthopedic surgery have multiple congenital anomalies and/or neuromuscular disease (see Appendix 1 ). Underlying diseases, particularly those associated with muscle weakness, require special anesthesia care; even minor surgery may be fraught with major anesthesia complications.
General Principles
- 1.
Children with orthopedic deformities may require repeated surgery and spend much time in the hospital; sympathetic management is particularly important, and preoperative sedation should be chosen carefully.
- 2.
Check the history carefully. Neuromuscular disease is particularly relevant. In general, muscle relaxants, particularly succinylcholine, should be avoided in children with myopathies (see Appendix 1 ). Drug selection is influenced by the underlying disease and the type of neuro-monitoring that will be used intraoperatively.
- 3.
Major surgery of the vertebral column deserves special consideration; the operations are extensive and may involve massive blood loss. Be prepared for a major transfusion. Autotransfusion and acute normovolemic hemodilution may be appropriate in some cases. Amicar and tranexamic acid decrease blood loss in spine surgery.
- 4.
Malignant hyperthermia, though very rare, is more common in children with orthopedic diseases. Maintain vigilance for the early signs of a reaction (see Chapter 6, page 197 ).
- 5.
When a tourniquet is used, blood loss is negligible. In other cases, surgery involving bone may result in significant blood loss (e.g., innominate osteotomy). Therefore establish a reliable intravenous route and confirm that blood is available.
- a.
When a tourniquet is inflated, there usually follows a progressive increase in the heart rate and blood pressure. The exact cause is unknown, but it has been attributed to sympathetic stimulation. If the anesthesiologist has been aggressively treating the tourniquet-induced hypertension by giving greater concentrations of inhaled agents, the blood pressure may decrease precipitously on tourniquet release. Therefore use caution with concentrations of potent inhalational agents and other drugs while the tourniquet is being used, and reduce the concentration in anticipation of tourniquet release.
- b.
Hemodynamic and metabolic responses to tourniquet release in children are usually not clinically important. A transient decrease in arterial pH associated with an increase in base deficit and carbon dioxide tension (PaCO 2 ) does occur; this is most marked after long tourniquet times or with the use of double tourniquets. General recommendations include the following:
- i.
Attempt to limit tourniquet times to less than 75 minutes.
- ii.
Use controlled ventilation before and after tourniquet release to remove the respiratory component of the acidosis.
- iii.
Do not release bilateral tourniquets simultaneously.
- iv.
In children in whom metabolic or respiratory acidosis is not easily compensated for (i.e., those with renal disease or pulmonary disease), consider staged release of the tourniquets and close monitoring of SaO 2 and EtCO 2 .
- v.
Serious complications of tourniquet use in children are very rare; however, pulmonary embolism on release has been reported in an obese child. Consider subcutaneous heparin in such children and monitor cardiopulmonary function closely after release.
- vi.
Ensure that the tourniquet is removed from the limb as soon as it is deflated. Residual pressure compromising perfusion of the limb has resulted in serious complications.
- i.
- a.
- 6.
Orthopedic surgery is associated with high levels of postoperative pain. Plan for optimal management, using regional analgesia whenever possible. The introduction of continuous peripheral nerve blocks using disposable pumps has opened up new avenues for postoperative pain control after limb or trunk surgery.
- 7.
Compartment syndrome may complicate orthopedic injuries, especially supracondylar fractures of the humerus, and forearm and tibial fractures. There is a concern that effective analgesia may mask the presenting sign of this syndrome (i.e., increased pain). This is especially of concern when the limb cannot easily be examined (i.e., encased in a cast). Compartment syndrome is rare enough that many question withholding effective analgesia from the majority of children who will not develop this complication. There is a strong consensus that effective postoperative pain relief should be provided for every child. Means to monitor compartment pressure are now readily available; a compartment syndrome must be diagnosed either by direct means (frequent nurse examination) or by the increased need for analgesic medication.
- 8.
Urinary retention may occur in children who have lower limb surgery and are treated with a regional block. This should be noted by postanesthesia care unit (PACU) staff and treated as necessary.
- 9.
Children with cerebral palsy frequently present for orthopedic surgery. These children require special considerations (see Chapter 6 ).
- 10.
Children with Duchenne muscular dystrophy may present for major scoliosis surgery and require careful assessment of their cardiorespiratory status and anticipation that the bleeding will be greater than usual (see later discussion and Appendix 1 ).
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Miscellaneous Orthopedic Procedures and Anesthesia Considerations
Hip Arthrogram
Hip arthrograms are performed in infants to assess the head of the femur and other aspects of the hip joint. As part of the procedure, a small amount of air may be injected into the joint to ensure that the tip of the needle is in the joint space before injecting contrast material; serious air embolism and cardiac arrest have occurred.
Recommendation: If a hip arthrogram is planned, determine whether air will be injected. Monitor the child very carefully during injection, omit nitrous oxide, and monitor for evidence of an air embolism.
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Club Feet
Beware of the high incidence of myopathies in children having clubfeet. Examine the child and the medical history carefully for any indications of a myopathy. If positive, revise the anesthesia technique appropriately.
In some cases, regional analgesia techniques combined with intravenous sedation may be optimal for clubfoot surgery. Caudal epidural analgesia may augment intraoperative management and provide for postoperative pain management.
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Limb Fractures
Closed Limb Fractures
Injuries to upper limbs are common; many of these children are older; therefore regional analgesia can be used. If so:
- 1.
Use a sufficient local analgesic drug to produce a profound block.
- 2.
Perform the block well in advance of the scheduled surgery so that it has plenty of time to become well established.
- 3.
If supplementary sedation is required, midazolam or ketamine is usually very satisfactory.
Fractures of the Forearm
- 1.
Perform a block of the brachial plexus via the axillary route, see Chapter 5, page 164 for drugs and doses. Ultrasonography improves the success with brachial plexus blocks.
- 2.
Intravenous blocks are not satisfactory for reduction of fractures. It is more difficult to apply an optimally tight cast to an exsanguinated limb.
Fractures of the Femur
- 1.
A block of the femoral nerve with lidocaine or bupivacaine is easy to perform and relieves pain and muscle spasm as the traction apparatus is being applied.
- 2.
A catheter may be introduced to the femoral sheath and a continuous femoral nerve block maintained with 0.5% bupivacaine (see continuous femoral block Chapter 5, page 166 ).
General Anesthesia
Every child with a recent fracture must be considered to have a full stomach and a rapid-sequence induction should be performed. Vomiting more frequently occurs during emergence from anesthesia; therefore, the child should be fully awake and in a lateral position before extubation.
Postoperative
- 1.
Pain may be quite severe after routine orthopedic surgery, and should be controlled by either systemic analgesic drugs or regional analgesia or a combination of these:
- a.
Regimens combining acetaminophen and a nonsteroidal antiinflammatory drug (NSAID) are more effective than either drug alone. Acetaminophen (40 mg/kg PR or 15 mg/kg PO) with ketoprofen (2 mg/kg IV) augmented by titrated doses of opioids as required is a suitable basic regimen. Pain should be assessed using standard objective measures (see Chapter 7 ).
- b.
Patient-controlled analgesia (PCA) may be appropriate for many children (see Chapter 7 ).
- c.
Regional analgesia provided by neuraxial or peripheral nerve block. When possible the latter should be chosen as this is less likely to cause complications. In children, it is customary to perform blocks and insert catheters under general anesthesia. Peripheral nerve blocks and catheter placement should be guided by ultrasonography when possible.
- d.
Peripheral nerve blocks may be initiated in the operating room and continued through the PACU to the ward or even to home using a disposable elastomeric infusion pump. The decision to continue this at home will depend upon the home circumstances and the attitude and abilities of the parents. A postoperative infusion of ropivacaine 0.2% at a rate of 0.1 ml/kg/hr has been suggested for continuous peripheral nerve block.
- a.
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Kyphoscoliosis
Kyphoscoliosis may be congenital (15% of cases), idiopathic (65%), or secondary to neuromuscular disease (20%). More than 80% of children with idiopathic scoliosis are female. Pulmonary function may be impaired, and some children with associated diseases (myopathies, cerebral palsy) may be severely disabled, wheelchair bound, and physiologically debilitated.
Pulmonary Function
Changes in pulmonary function are related to the underlying cause, the speed of development of the scoliosis, and the severity of the curvature. The cardiorespiratory effects of scoliosis are summarized in Figure 15-1 .
The pulmonary abnormality is restrictive rather than obstructive; chest wall compliance is reduced. The vital capacity and the total lung capacity may be dramatically reduced, and the functional residual capacity somewhat less so. The residual volume tends to be maintained. The elastic resistance of the chest wall may be high, increasing the work of breathing. If left untreated, severe and prolonged lung compression impairs gas exchange, which becomes evident only in later stages of the disease.
The principal concern for young children with idiopathic scoliosis is the cosmetic effect of the spinal and pelvic or chest wall deformity, especially when the curvature increases during the years of rapid body growth. At this stage, respiratory symptoms are uncommon, but pulmonary function studies may reveal an abnormality. Although lung volumes can be normal, exercise tolerance may be reduced. In severe cases the mechanical effects of scoliosis on respiratory function are apparent even at rest.
Pulmonary function is relatively normal in most children who present for correction of idiopathic scoliosis with a curvature of less than 65%. Respiratory disability is more likely to occur in association with congenital scoliosis or curvature of paralytic etiology.
The High-Risk Scoliotic Child
Scoliosis surgery may be recommended for severely incapacitated children for the purpose of facilitating their ongoing care and arresting the progression of cardiorespiratory compromise. There is a very high incidence of perioperative complications in this group of children and many require very aggressive and prolonged postoperative intensive care; however, the ultimate outcome is judged by many of these children and their caregivers to be worthwhile. It is very important that these children be optimally prepared for their surgery:
- 1.
The nutritional status should be assessed and optimized using TPN or via a gastrostomy as may be appropriate to the individual.
- 2.
The pulmonary system should be evaluated for reversible disease that might be improved by physiotherapy or antibiotic therapy. Those with neuromuscular disease and a preoperative FEV 1 less than 40% of predicted are likely to need postoperative ventilation.
- 3.
The cardiac status should be evaluated by echocardiogram (i.e., myocardial contractility, RV function, etc.) and preoperative therapy initiated as indicated.
- 4.
The pediatric intensive care unit (PICU) should be notified that the child will require admission and they should be familiar with his or her preoperative condition.
Surgical Procedures
- 1.
Posterior spinal fusion may be performed using contoured metal rods to stabilize the spine postoperatively until bony fusion occurs. In some children with a flexible spine, the deformity is corrected solely by a posterior fusion. Adjustable rods may be placed in some young children to permit adjustments during growth.
- 2.
In some, an anterior thoracoabdominal approach may be used to remove the intervertebral discs or a hemivertebra to correct a lateral curve. This may be an open procedure or an endoscopic procedure.
- 3.
In others, the two procedures are combined: an anterior release followed by a posterior fusion. In this case, surgery is often prolonged, and associated with significant blood loss: a challenge for the anesthesiologist. Anterior release procedures may be carried out endoscopically, in which case the special considerations for endoscopic surgery apply (see Chapter 13, page 339 ).
Special Anesthesia Problems
- 1.
Anesthesia management must take into account the following:
- a.
The severity and cause of the curvature. The more severe the curve, the more pulmonary function is impaired, and greater the likelihood of postoperative pulmonary failure.
If the scoliosis is secondary to neuromuscular disease:
- i.
Pulmonary function impairment caused by the mechanical effects of the spinal curvature may be compounded by involvement of respiratory muscles in the disease process. Postoperative respiratory insufficiency is more likely.
- ii.
Increased bleeding may be expected. This may be a result of altered vascular responses and platelet adhesion associated with myopathies (e.g., Duchenne muscular dystrophy).
- iii.
Cardiomyopathy may occur in adolescents with Duchenne muscular dystrophy.
- iv.
Selection of suitable drugs may be limited (i.e., avoid succinylcholine and inhalational anesthetics to prevent rhabdomyolysis if a myopathy is present. Titrate doses of nondepolarizing relaxants if required.
- i.
- b.
The degree of respiratory and cardiovascular impairment:
- i.
Surgery may be expected to stabilize the cardiorespiratory effects of the disease but may not improve these.
- ii.
A further impairment of pulmonary function must be anticipated in the early postoperative phase and may require respiratory support.
- i.
- c.
The type of corrective procedure proposed.
- i.
Posterior fusion only
- ii.
Anterior and posterior fusion combined
- i.
- a.
- 2.
Preoperative assessment must include the following:
- a.
Detailed history and examination for an indication of abilities, stamina, and the presence of any other significant medical conditions.
- b.
Routine hematology studies, biochemistry, and cross matching for transfusion.
- c.
Pulmonary function studies, including blood gas analysis. (These studies may not be possible in very young children due to lack of cooperation.)
- d.
Echocardiogram to assess myocardial function for all children (particularly adolescents) with very severe curves or associated myopathy.
- a.
- 3.
Be alert for signs of significant respiratory impairment (i.e., tachypnea at rest, severely reduced vital capacity, abnormal blood gas values, inability to cough effectively). Postoperatively, hypoventilation, secretion retention, and atelectasis are likely in response to pain, analgesic drugs, and immobilization that will further compound existing problems.
- 4.
Severe impairment of respiratory function is not a contraindication to surgery, provided that resources are available for postoperative intensive respiratory care (including controlled ventilation, if necessary). Fixation of the spinal deformity is essential to prevent further deterioration of respiratory function (but usually does not result in significant improvement).
- 5.
Children with a vital capacity less than 40% of normal may develop major respiratory complications postoperatively and likely require postoperative ventilation.
Corrective Surgery by the Posterior Approach
Special Anesthesia Problems
- 1.
Because the child will be in the prone position, extra care should be taken to secure the tracheal tube and prevent it from becoming dislodged. If preoperative correction of the spinal curvature has been achieved with an exoskeletal apparatus, intubation will probably be difficult; fixation of the head and neck may render adequate direct laryngoscopy impossible, making a fiberoptic technique necessary.
- 2.
Discuss with the family and the child the need for invasive lines, postoperative ventilation (if likely), the need for ICU, and the potential for an intraoperative wake-up test.
- 3.
Blood loss may be severe (in excess of 50% of the estimated blood volume [EBV]). Most bleeding originates from the vertebral veins, which become engorged if there is any pressure on the anterior abdomen. Blood loss is also related to the extent of the surgery (length of spine to be fused) and to the surgeon’s speed and expertise. Those with scoliosis secondary to a recognized neuromuscular disorder usually have a larger blood loss than those with idiopathic scoliosis. Alternatives to homologous transfusion should be considered:
- i.
Autologous blood programs are very suitable for preoperative collections in these children.
- ii.
Intraoperative acute normovolemic hemodilution may be used cautiously.
(These procedures may be optimized by giving oral ferrous sulfate daily beginning 4 weeks before surgery and then administering twice-weekly intramuscular injections of erythropoietin commencing 2 weeks before surgery. The hematocrit (Hct) should not be allowed to exceed 55% preoperatively).
- iii.
The cell saver may be used to salvage erythrocytes from suctioned blood. However, transfusion of large volumes of washed cells may lead to coagulopathy because of dilution of coagulation factors. Fresh-frozen plasma should also be administered if blood loss exceeds one blood volume.
- i.
- 4.
Spinal cord function is usually monitored during surgery: the use of somatosensory evoked potentials (SSEPs) has been augmented by the addition of motor evoked potentials (MEPs), stimulating the cord above the level of the surgery and recording the electromyogram from the limb.
Anesthetic techniques that permit the monitoring of evoked potentials limit inhalational agents to 0.5 MAC, although large doses of opioids may be given. Nitrous oxide decreases the amplitude of evoked potentials and is usually avoided. Propofol/opioid infusions are the mainstay for these anesthetics. Benzodiazepines may be used to induce amnesia. During the testing of MEPs, better results are obtained with minimal neuromuscular blockade (i.e., 2 to 4 twitches on a train of four); specifically, most electrophysiologists permit an intermediate-acting relaxant for tracheal intubation and then no further relaxant during surgery whereas others permit an infusion to maintain a limited degree of neuromuscular blockade. Because of the difficulty in assessing depth of anesthesia during TIVA, a depth of anesthesia monitor is often used.
Despite the use of multimodal neurophysiologic monitoring, a wake-up test may still be required (i.e., a surgical misadventure or failure of the monitoring system). Fortunately, the anesthesia technique that provides for neurophysiologic monitoring also allows for a rapid wake-up test should this be required.
Every child should be awake at the end of the operation, so that both sensory and motor function can be tested immediately. Any defects should be reported to the surgeon promptly.
- 5.
Pulmonary function may be severely impaired. The anesthesiologist must check that the present state is optimal and exclude any superimposed acute respiratory disease.
- 6.
Postoperative pain is considerable; intrathecal opioids administered intraoperatively have been effective for postoperative analgesia and may also facilitate intraoperative BP control and reduce blood loss. Otherwise epidural analgesia or PCA should be planned and these options discussed with the child and family.
- 7.
Visual loss occurs rarely after spine surgery.
- a.
The most common ocular injury is a corneal abrasion. Far less common is visual loss because of posterior ischemic optic neuropathy (PION) (occurring three times more frequently than anterior AION) or central retinal artery occlusion (CRAO) may rarely occur after spine surgery—especially when performed in the prone position.
- b.
Age: occurs rarely in pediatric patients (<18 years).
- c.
Factors associated with visual loss because of ION include preoperative anemia, prolonged surgery, intraoperative hypotension, low hematocrit, and major blood loss. CRAO results from direct facial-orbital compression.
- d.
A possible but unproven factor in the genesis of postspinal visual loss is excessive crystalloid fluid administration intraoperatively. This is known to increase intraocular pressure (IOP) and periorbital edema.
- e.
NB. Visual loss recovers in 44% of those with ION but in 0% of those with CRAO.
Procedures that reduce the risk of intraoperative visual loss:
- a.
- 1.
Assess the child carefully and encourage staged procedures if the proposed operation may be excessively long (>6 hours) or associated with large blood losses (>45% estimated blood volume).
- 2.
Position carefully:
- a.
Avoid pressure on the eyes—check frequently during surgery and document this in the anesthesia record.
- b.
Position the head in a neutral forward position (no neck flexion, extension, or rotation) so that it is level with or above the heart.
- a.
- 3.
Monitor the hematocrit frequently and avoid markedly reduced levels intraoperatively.
- 4.
Monitor central venous pressure and administer balanced crystalloid and colloid solutions to maintain an adequate blood volume.
- 5.
Induced hypotension is an accepted practice for spine surgery but avoid excessively reduced levels from baseline (i.e., within 20% to 25% of baseline mean arterial pressure or a minimum systolic pressure of 80 to 90 mm Hg).
Check the child’s vision immediately upon awakening and seek consultation if there are any defects.
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