Handbook of Clinical Anesthesia
Anesthesia for Orthopaedic Surgery
Many orthopaedic surgical procedures lend themselves to the use of regional anesthesia (intraoperative anesthesia and postoperative analgesia) (Horlocker TT, Wedel DJ: Anesthesia for orthopaedic surgery. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 1375–1392). Anesthesia for orthopaedic surgery requires an understanding of special positioning requirements (risk of peripheral nerve injury), appreciation of the possibility of large intraoperative blood loss and techniques to limit the impact of this occurrence (intraoperative hypotension, salvage techniques), and the risk of venous thromboembolism (emphasizing the need for the anesthesiologist to consider the interaction of anticoagulants and antiplatelet drugs with anesthetic drugs or techniques, especially regional anesthesia).
- Preoperative Assessment (Table 53-1)
A brief neurologic examination with documentation of any pre-existing deficits is recommended.
- Choice of Anesthetic Technique
III. Surgery to the Spine
- Spinal Cord Injuries.Spinal cord injuries must be considered in any patient who has experienced trauma. (Cervical spine injuries are associated with head and thoracic injuries, and lumbar spine injuries are associated with abdominal injuries and long bone fractures.)
Table 53-1 Preoperative Assessment of Orthopaedic Surgical Patients
- Tracheal Intubation
- Airway management is critical because the most common cause of death with acute cervical spinal cord injury is respiratory failure.
- All patients with severe trauma or head injuries should be assumed to have an unstable cervical fracture until proven otherwise radiographically.
- Awake fiberoptic-assisted intubation may be necessary, with general anesthesia induced only after voluntary upper and lower extremity movement is confirmed.
- In a truly emergent situation, oral intubation of the trachea with direct laryngoscopy (minimal flexion or extension of the neck) is the usual approach.
Table 53-2 Advantages of Regional versus General Anesthesia for Orthopaedic Surgical Procedures
- Respiratory considerationsinclude an inability to cough and clear secretions, which may result in atelectasis and infection.
- Cardiovascular considerationsare based on loss of sympathetic nervous system innervation (“spinal shock”) below the level of spinal cord transection. (Cardioaccelerator fiber [T1–T4] loss results in bradycardia and possible absence of compensatory tachycardia if blood loss occurs.)
- Succinylcholine-Induced Hyperkalemia.It is usually safe to administer succinylcholine (Sch) within the first 48 hours after spinal cord injury. It should be avoided after 48 hours in all patients with spinal cord injuries.
- Temperature Control.Loss of vasoconstriction below the level of spinal cord transection causes patients to become poikilothermic. (Body temperature should be maintained by increasing ambient air temperature and warming intravenous [IV] fluids and inhaled gases.)
- Maintaining Spinal Cord Integrity.An important component of anesthetic management is preservation of spinal cord blood flow. (Perfusion pressure should be maintained, and extreme hyperventilation of the lungs should be avoided.) Neurophysiologic monitoring (somatosensory or motor evoked potentials), a “wake-up test,” or both are used to recognize neurologic ischemia before it becomes irreversible.
- Autonomic Hyperreflexia(Table 53-3).
- Pulmonary Considerations.Postoperative ventilation of the patient's lungs is likely to be necessary if
the vital capacity is below 40% of the predicted value. Prolonged arterial hypoxemia, hypercapnia, and pulmonary vascular constriction may result in right ventricular hypertrophy and irreversible pulmonary hypertension.
Table 53-3 Characteristics of Autonomic Hyperreflexia
- Cardiovascular Considerations.Prolonged alveolar hypoxia caused by hypoventilation and ventilation/ perfusion mismatch eventually causes irreversible vasoconstriction and pulmonary hypertension.
- Surgical Approach and Positioning.
- The prone position is used for the posterior approach to the spine. (The hazards of the prone position, including brachial plexus stretch injury [the head should be rotated toward the abducted arm and the eyes taped closed], should be considered.)
- The anterior approach is achieved with the patient in the lateral position, usually with the convexity of the curve uppermost. Removal of a rib may be necessary. A double-lumen endotracheal tube is used to collapse the lung on the operative side.
- A combined anterior and posterior approach in one or two stages yields higher union rates but is associated with increased morbidity, including blood loss and nutritional deficits.
- Anesthetic Management
- Respiratory reserve is assessed by exercise tolerance, vital capacity measurement, and arterial blood gas analysis. Autologous blood donation is often recommended (usually ≥4 U can be collected in the month before surgery).
- There are specific anesthetic considerations for surgical correction of scoliosis by spinal fusion and instrumentation (Table 53-4).
- Adequate hemodynamic monitoring and venous access are essential in the management of patients undergoing spinal fusion and instrumentation (Table 53-5).
- Degenerative Vertebral Column Disease.Spinal stenosis, spondylosis, and spondylolisthesis are forms of degenerative vertebral column disease that may lead to neurologic deficits necessitating surgical intervention.
- Surgical Approach and Positioning
Table 53-4 Anesthetic Considerations for Surgical Correction of Scoliosis
- Cervical laminectomy is most often performed with patients in the prone position (Fig. 53-1).
- Fiberoptic-assisted intubation may be necessary in patients with severely limited cervical movement.
- The anterior approach places the surgical incision (anterior border of the sternocleidomastoid muscle) near critical structures (carotid artery, esophagus, trachea [edema and recurrent nerve injury are possible]).
- The use of the sitting position for cervical laminectomy allows a more blood-free surgical field but introduces the risk of venous air embolism. The incidence is less than for sitting posterior fossa craniotomy, but the patient still needs to be monitored with precordial Doppler.
- Anesthetic Management
- General anesthesia is most often selected for spinal surgery because it ensures airway access
and is acceptable for prolonged operations. Patients undergoing cervical laminectomy should be assessed preoperatively for cervical range of motion and the presence of neurologic symptoms during flexion, extension, and rotation of the head. (Awake fiberoptic intubation of the trachea may be necessary.)
Table 53-5 Monitoring for Patients Undergoing Scoliosis Surgery
Figure 53-1. Prone position with the patient's head turned and the dependent ear and eye protected from pressure. Chest rolls are in place, the arms are extended forward without hyperextension, and the knees are flexed.
- Sch should be avoided if there is evidence of a progressive neurologic deficit.
- Spinal Cord Monitoring.Paraplegia is a feared complication of major spine surgery. The incidence of neurologic injuries associated with scoliosis correction is 1.2%. When patients awaken with paraplegia, neurologic recovery is unlikely, although immediate removal of instrumentation improves the prognosis. It is therefore essential that any intraoperative compromise of spinal cord function be detected as early as possible and reversed immediately. The two methods for detecting intraoperative compromise of spinal cord function are the “wake-up test” and neurophysiologic monitoring.
- The wake-uptest consists of intraoperative awakening of patients after completion of spinal instrumentation. Surgical anesthesia (often including opioids) and neuromuscular blockers are allowed to dissipate, and the patient is asked to move the hands and feet before anesthesia is re-established. Recall may occur but is rarely viewed as unpleasant, especially if the patient is fully informed before surgery.
- Neurophysiologic monitoring (as an adjunct or an alternative to the wake-up test) includes
somatosensory evoked potentials (SSEPs) (waveforms may be altered by volatile anesthetics, hypotension, hypothermia, hypercarbia), motor evoked potentials (MEPs) (neuromuscular blocking drugs cannot be used), and electromyography.
- SSEPs reflect the dorsal columns of the spinal cord (proprioception and vibration) supplied by the posterior spinal artery.
- MEPs reflect the motor pathways and the portion of the spinal cord supplied by the anterior spinal artery.
- The combined use of SSEPs and MEPs may increase the early detection of intraoperative spinal cord ischemia.
- If both SSEPs and MEPs are to be monitored during major spine surgery, one might consider providing anesthesia with an ultrashort-acting opioid infusion with a low dose of inhaled anesthetic and monitoring the electroencephalogram to minimize the potential for intraoperative awareness.
- Blood Loss
- A combination of IV hypotensive agents and volatile anesthetics is frequently used in an attempt to decrease blood loss during surgery.
- Perioperative coagulopathy from dilution of coagulation factors, platelets, or fibrinolysis may be predicted from measurement of either the prothrombin time or activated partial thromboplastin time.
- Visual Loss After Spine Surgery.Most cases are associated with complex instrumented fusions often associated with prolonged intraoperative hypotension, anemia, large intraoperative blood loss, and prolonged surgery (also present in patients who do not develop blindness). The American Society of Anesthesiologists' Closed Claims Registry concludes that patients at high risk for postoperative visual loss after major spine surgery are those in whom blood loss is 1000 mL or greater or undergoing surgery lasting 6 hours or longer.
- Venous Air Embolus.Venous air embolism can occur in all positions used for laminectomies because the operative site is above the heart level. Presenting signs are usually unexplained hypotension and an increase in the end-tidal nitrogen concentration.
Table 53-6 Changes After Major Spine Surgery That May Influence the Ability to Perform Epidural or Spinal Anesthesia
- Postoperative Care
- Most patients' tracheas can be extubated immediately after posterior spinal fusion operations if the procedure was relatively uneventful and preoperative vital capacity values were acceptable. The presence of severe facial edema may prevent prompt tracheal extubation.
- Aggressive postoperative pulmonary care, including incentive spirometry, is necessary to avoid atelectasis and pneumonia.
- Continued hemorrhage in the postoperative period is a concern.
- Epidural and Spinal Anesthesia After Major Spine Surgery
- Postoperative anatomic changes make needle or catheter placement more difficult after major spine surgery (Table 53-6).
- Spinal anesthesia may be a more reliable technique than epidural anesthesia if a regional technique is selected.
- The presence of postoperative spinal stenosis or other degenerative changes in the spine or pre-existing neurologic symptoms may preclude the use of regional anesthesia in these patients.
- Surgery to the Upper Extremities
Orthopaedic surgical procedures to the upper extremities are well suited to regional anesthetic techniques (Table 53-7). Upper extremity peripheral nerve blocks may be
used in the treatment and prevention of reflex sympathetic dystrophy. Continuous catheter techniques provide postoperative analgesia and facilitate early limb mobilization. The patient should be examined preoperatively to document any neurologic deficits because orthopaedic surgical procedures often involve peripheral nerves with pre-existing deficits (ulnar nerve transposition at the elbow, carpal tunnel release of the median nerve at the wrist) or may be adjacent to neural structures (total shoulder arthroplasty or fractures of the proximal humerus). Improper surgical positioning, the use of a tourniquet, and the use of constrictive casts or dressings may also result in perioperative neurologic ischemia. Local anesthetic selection should be based on the duration and degree of sensory or motor block required. (Prolonged anesthesia in the upper extremity in contrast to the lower extremity is not a contraindication to hospital discharge.)
Table 53-7 Regional Anesthetic Techniques for Upper Extremity Surgery
- Surgery to the Shoulder and Upper Arm
- A significant incidence of neurologic deficits in patients undergoing this type of surgery demon-strates the importance of clinical examination before regional anesthetic techniques are performed.
- Total shoulder arthroplastymay be associated with a postoperative neurologic deficit (brachial plexus injury) that is at the same level of the nerve trunks at which an interscalene block is performed. It is impossible to determine a surgical or anesthetic cause. Most of these injuries represent neurapraxia and resolve in 3 to 4 months.
- Radial nerve palsyis associated with humeral shaft fractures, and axillary nerve injury is associated with proximal humeral shaft fractures.
- Surgical Approach and Positioning
- Typically, the patient is flexed at the hips and knees (“beach chair position”) and placed near the edge of the operating table to allow unrestricted access by the surgeon to the upper extremity.
- The head and neck are maintained in a neutral position because excessive rotation or flexion of the head away from the side of surgery may result in stretch injury to the brachial plexus.
- Anesthetic Management.Surgery to the shoulder and humerus may be performed under regional
(interscalene or supraclavicular brachial plexus block) or general anesthesia. The ipsilateral diaphragmatic paresis and 25% loss of pulmonary function produced by interscalene block mean that this block is contraindicated in patients with severe pulmonary disease.
- Surgery to the Elbow.Surgical procedures to the distal humerus, elbow, and forearm are suited to regional anesthetic techniques. Supraclavicular block of the brachial plexus is more reliable than the axillary approach (which may miss the musculocutaneous nerve) but introduces the risk of pneumothorax (typically manifests 6–12 hours after hospital discharge such that postoperative chest radiography may not be useful).
- Surgery of the Wrist and Hand
- Brachial plexus block (axillary approach) is most commonly used for surgical procedures of the forearm, wrist, and hand. The interscalene approach is seldom used for wrist and hand procedures because of possible incomplete block of the ulnar nerve (15%–30% of patients), and the supraclavicular approach introduces the risk of pneumothorax.
- IV regional anesthesia (“Bier block”) permits the use of a tourniquet but has disadvantages of limited duration (90–120 minutes), possible local anesthetic systemic toxicity, and rapid termination of anesthesia (and postoperative analgesia) on tourniquet deflation.
- Continuous Brachial Plexus Anesthesia
- Catheters placed in the sheath surrounding the brachial plexus permit continuous infusion of local anesthetic solution. (Bupivacaine 0.125% prevents vasospasm and improves circulation after limb reimplantation or vascular repair.)
- Indwelling catheters may be left in place for 4 to 7 days after surgery.
- Surgery to the Lower Extremities
Orthopaedic procedures to the lower extremity may be performed under general or regional anesthesia, although regional anesthesia may provide some unique advantages (Table 53-8).
- Surgery to the Hip
Table 53-8 Lumbosacral Techniques for Major Lower Extremity Surgery
- Surgical Approach and Positioning.The lateral decubitus position is frequently used to facilitate surgical exposure for total hip arthroplasty, and a fracture table is often used for repair of femur fractures. The patient must be carefully monitored for hemodynamic changes during positioning when under general or regional anesthesia. (Adequate hydration and gradual movement minimize blood pressure decreases.) Care should be taken to pad and position the arms and to avoid compression of the brachial plexus. (A “chest roll” is placed caudad to the axilla to support the upper part of the dependent thorax.)
- Anesthetic Technique.Spinal or epidural anesthesia is well suited to procedures involving the hip. Deliberate hypotension can also be used with general anesthesia as a means of decreasing surgical blood loss.
- Total Knee Arthroplasty (TKA)
- Patients undergoing TKA experience significant postoperative pain, which impedes physical therapy and rehabilitation.
- Regional anesthetic techniques that can be used for surgical procedures on the knee include epidural, spinal, and peripheral leg blocks. Spinal anesthesia is often selected, but an advantage of a continuous epidural is postoperative pain management. (Aggressive postoperative regional analgesic techniques for 48–72 hours shorten the rehabilitation period more than systemic opioids.)
- Patients undergoing amputation of a lower limb often benefit from the use of regional anesthesia, although adequate sedation is imperative.
- Postoperative Analgesia after Major Joint Replacement.Pain after total joint replacement, particularly total knee replacement, is severe. Single-dose and continuous peripheral nerve techniques that block the lumbar plexus (femoral nerve block) with or without sciatic nerve block provide excellent postoperative analgesia.
- Knee Arthroscopy and Anterior Cruciate Ligament (ACL) Repair.Diagnostic knee arthroscopy may be performed under local anesthesia with sedation. (A single dose or continuous lower extremity block is not warranted in most patients.) ACL repair requires
postoperative analgesia (femoral nerve blocks should be considered).
- Intra-articular injectionof local anesthetics (bupivacaine), opioids (morphine), or both has become routine for perioperative management after arthroscopic knee surgery.
- Surgery to the Ankle and Foot
- The selection of a regional technique is based on the surgical site, use of a tourniquet (use of a high tourniquet for longer than 15–20 minutes necessitates a neuraxial or general anesthetic), and need for postoperative analgesia.
- Peripheral nerve blocks (femoral and sciatic nerve) provide acceptable anesthesia for surgery on the foot and ankle.
- Microvascular Surgery
Table 53-9 Anesthetic Considerations for Microvascular Surgery for Limb Replantation
VII. Pediatric Orthopaedic Surgery
- Regional anesthetic techniques are adaptable to pediatric patients, especially in those older than 7 years of age.
- IV regional anesthesia is particularly useful in pediatric patients for minor procedures such as closed reduction of forearm fractures.
- The use of local anesthetic creams minimizes patient discomfort during placement of an IV catheter.
- The size of the upper arm often precludes the use of a double tourniquet in pediatric patients, thus limiting the duration of the surgical procedure to 45 to 60 minutes (tourniquet pain typically develops by this time).
VIII. Other Considerations
- Anesthesia for Nonsurgical “Closed” Orthopaedic Procedures.Some minor procedures (cast and dressing changes in pediatric patients, pin removal) require only light sedation, but procedures involving bone and joint manipulation (hip and shoulder relocation, closed reduction of fractures) usually require a general or regional anesthetic.
- Opinions differ as to the pressure required in tourniquets to prevent bleeding (usually 100 mm Hg above patient's systolic blood pressure for the leg and 50 mm Hg above systolic blood pressure for the arm). Before the tourniquet is inflated, the limb should be elevated for about 1 minute and tightly wrapped with an elastic bandage distally to proximally. Oozing despite tourniquet inflation is most likely caused by intramedullary blood flow in long bones.
- The duration of safe tourniquet inflation is unknown (1–2 hours is not associated with irreversible changes). Five minutes of intermittent perfusion between 1 and 2 hours may allow more extended use.
- Transient systemic metabolic acidosis and increased PaCO2(1–8 mm Hg) may occur after tourniquet deflation.
- Tourniquet pain despite adequate operative anesthesia typically appears after about 45 minutes (may
reflect more rapid recovery of C fibers as the block wanes). During surgery, this pain is managed with opioids and hypnotics.
- Fat Embolus Syndrome
- Patients at risk include those with multiple traumatic injuries and surgery involving long bone fractures, intramedullary instrumentation or cementing, or total knee surgery. The incidence of fat embolism syndrome in isolated long bone fractures is 3% to 4%, and the mortality rate is 10% to 20%.
- Clinical and laboratory signs usually occur 12 to 40 hours after injury and may range from mild dyspnea to coma (Table 53-10).
- Treatment includes early stabilization of fractures and support of oxygenation. Steroid therapy may be instituted.
- Methyl Methacrylate
- Insertion of this cement may be associated with hypotension, which has been attributed to absorption of the volatile monomer of methyl methacrylate or embolization of air (nitrous oxide should be discontinued before cement is placed) and bone marrow during femoral reaming.
- Adequate hydration and maximizing oxygenation minimize the hypotension and arterial hypoxemia that may accompany cementing of the prosthesis.
Table 53-10 Criteria for Diagnosis of Fat Embolism Syndrome
Table 53-11 Antithrombotic Regimens to Prevent Thromboembolism in Orthopedic Surgical Patients
- Venous thromboembolismis a major cause of death after surgery or trauma to the lower extremities. Without prophylaxis, 40% to 80% of orthopaedic patients develop venous thrombosis. (The incidence of fatal pulmonary embolism is highest in patients who have undergone surgery for hip fracture.)
- Antithrombotic prophylaxisis based on identification of risk factors (Table 53-11). Several studies show a deceased incidence of deep vein thrombosis (DVT) and pulmonary embolism in patients undergoing hip surgery and knee surgery under epidural and spinal anesthesia (Table 53-12).
- Neuraxial Anesthesia and Analgesia in Patients Receiving Antithrombotic Therapy
Table 53-12 Possible Explanations for Decreased Incidence of Deep Vein Thrombosis in Patients Receiving Regional Anesthesia
Table 53-13 Neuraxial Anesthesia and Analgesia in Orthopedic Patients Receiving Antithrombotic Therapy
- Despite perceived advantages of neuraxial techniques for hip and knee surgery (including a decreased incidence of DVT), patients receiving perioperative anticoagulants and antiplatelet medications are often not considered candidates for spinal or epidural anesthesia because of the risk of neurologic deficit from a spinal or epidural hematoma (Table 53-13).
- The patient should be closely monitored in the perioperative period for signs of paralysis. If a spinal hematoma is suspected, the treatment is immediate decompressive laminectomy. (Recovery of neurologic function is unlikely if >10–12 hours elapse.)
Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine
Title: Handbook of Clinical Anesthesia, 6th Edition
Copyright ©2009 Lippincott Williams & Wilkins
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