Anesthesia for Orthopedic Surgery

Presentation on theme: "Anesthesia for Orthopedic Surgery"— Presentation transcript:

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Anesthesia for Orthopedic Surgery

Dr abdollahi

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Many orthopedic surgical procedures lend themselves to the use of

regional anesthesia (intraoperative anesthesia and postoperative analgesia.

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Anesthesia for orthopedic 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).

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T

he 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).

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Preoperative Assessment

.A brief neurologic examination with documentation of any pre-existing deficits is recommended.

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Pre-Existing Medical Problems

Coronary artery disease (perioperative β blockade should be considered)

Rheumatoid arthritis (steroid therapy, airway management)Physical Examination

Mouth opening or neck extension

Evidence of infection and anatomic abnormalities at proposed sites for introduction of regional anesthesia (peripheral techniques may be acceptable if a regional technique is contraindicated)

A

rthritic changes and limitations to positioning

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Choice of Anesthetic Technique

Advantages of Regional versus General Anesthesia for Orthopaedic Surgical Procedures

Improved postoperative analgesia

Decreased incidence of nausea and vomiting

Less respiratory and cardiac depression

Improved perfusion because of sympathetic nervous system block

Decreased

intraoperative

blood loss

Decreased blood pressure

Blood flow redistribution to large caliber vessels

Locally decreased venous pressure

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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.)

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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.

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Respiratory considerations

Respiratory considerations include an inability to cough and clear secretions, which may result in atelectasis and infection.

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Cardiovascular considerations

Cardiovascular considerations are 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.)

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Succinylcholine-Induced Hyperkalemia

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.

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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).

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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.

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Autonomic Hyperreflexia

Occurs in 85% of patients with spinal cord transection above T5

Paroxysmal hypertension with bradycardia (baroreceptor

reflex)

Cardiac

dysrhythmias

Cutaneous

vasoconstriction below and

vasodilation

above the level of

transection

Precipitated by any noxious stimulus (distention of a hollow

viscus

)

Treatment is removal of stimulus, deepening of anesthesia, and administration of a vasodilator

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Scoliosis

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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.

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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.

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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.

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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.

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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).

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There are specific anesthetic considerations for surgical correction of scoliosis by spinal fusion and instrumentation .

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Anesthetic Considerations for Surgical Correction of Scoliosis

Management of the prone position

Hypothermia (long procedure and extensive exposed area)

Extensive blood and fluid losses

Maintenance of spinal cord integrity

Prevention and treatment of venous air embolism

Reduction of blood loss through

hypotensive

anesthetic techniques

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Adequate hemodynamic monitoring and venous access are essential in the management of patients undergoing spinal fusion and instrumentation .

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Monitoring for Patients Undergoing Scoliosis Surgery

Cannulation

of radial artery (direct blood pressure measurement and assessment of blood gases)Central venous catheter (evaluates blood and fluid management and aspirate air if venous air embolism occurs)

Pulmonary artery catheter (pulmonary hypertension)

Neurophysiologic monitoring (prompt diagnosis of neurologic changes and early intervention)

Somatosensory

evoked potentials Motor evoked potentials Wake-up test

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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.

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Surgical Approach and Positioning

Cervical laminectomy

is most often performed with patients in the prone position (Fig. 53-1).

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. 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.Slide29

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]).

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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.

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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.)

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Sch

should be avoided if there is evidence of a progressive neurologic deficit.11/26/2011

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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.

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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.

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wake-up

The wake-up test 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.

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Neurophysiologic monitoring

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),

Electromyography.

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SSEPs reflect the dorsal columns of the spinal cord (

proprioception and vibration) supplied by the posterior spinal artery.

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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.

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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

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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.

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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).

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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.

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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.

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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.

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Epidural and Spinal Anesthesia After Major Spine Surgery

Postoperative anatomic changes make needle or catheter placement more difficult after major spine surgery .

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Changes After Major Spine Surgery That May Influence the Ability to Perform Epidural or Spinal Anesthesia

Degenerative changes (spondylothesis below level of fusion) that increase the chance of spinal cord ischemia and neurologic complications with regional anesthesia

Ligamentum

flavum

injury from prior surgery results in adhesions and possible obliteration of the epidural space or interference with spread of local anesthetic solution (“patchy block”)

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3.Increased incidence of accidental

dural puncture if the epidural space is altered by prior surgery (blood patch is difficult to perform if needed)4.Prior bone grafting or fusion may prevent midline insertion of the needle

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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.

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Surgery to the Upper Extremities

Orthopaedic surgical procedures to the upper extremities are well suited to regional anesthetic techniques .

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Regional Anesthetic Techniques for Upper Extremity Surgery

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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.

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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

).

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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.)

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Surgery to the Shoulder and Upper Arm

A significant incidence of neurologic deficits in patients undergoing this type of surgery demonstrates the importance of clinical examination before regional anesthetic techniques are performed.

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Total shoulder

arthroplasty may 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.

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Radial nerve palsy is associated with humeral shaft fractures, and

axillary nerve injury is associated with proximal humeral shaft fractures.

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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.

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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).

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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

.

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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.

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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.

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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 .

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Lumbosacral Techniques for Major Lower Extremity Surgery

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Surgery to the Hip

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.)

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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.)

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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.

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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

.)

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Patients undergoing amputation of a lower limb often benefit from the use of regional anesthesia, although adequate sedation is imperative.

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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.

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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).

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Intra-

articular injection of local anesthetics (bupivacaine), opioids (morphine), or both has become routine for

perioperative management after arthroscopic knee surgery.

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Surgery to the Ankle and Foot

Peripheral nerve blocks (femoral and sciatic nerve) provide acceptable anesthesia for surgery on the foot and ankle.

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Microvascular

Surgery

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Anesthetic Considerations for Microvascular Surgery for Limb

ReplantationMaintain blood flow through

microvascular anastomoses (critical for graft viability).

Prevent hypothermia (increase temperature of operating room to 21°C; warm IV solutions and inhaled gases).

Maintain perfusion pressure.

Avoid

vasopressors

.

Use vasodilators (volatile anesthetics,

nitroprusside

) and sympathetic nervous system block (regional anesthesia).

Consider

normovolemic

hemodilution

.

Administer

antithrombotics

(heparin) with or without

fibrinolytics

(low-molecular-weight

dextran

).

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7.Remember positioning considerations associated with long surgical procedures.

8.Replace blood and fluid losses. 9.Consider the choice of anesthesia (often a combination of regional and general anesthesia)

10.Sympathectomy is helpful, but the long duration of surgery may limit use of single-shot techniques (another option is a continuous technique)11.Ensure airway access and patient immobility.

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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.

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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).

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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.

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Tourniquets

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.

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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.

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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

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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%.

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Clinical and laboratory signs usually occur 12 to 40 hours after injury and may range from mild

dyspnea to coma .Treatment includes early stabilization of fractures and support of oxygenation. Steroid therapy may be instituted

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Criteria for Diagnosis of Fat Embolism Syndrome

MAJOR :Axillary or subconjunctival

petechiae Hypoxemia (PaO

2

< 60 mm Hg)

CNS depression (disproportionate to hypoxemia)

Pulmonary edema

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Criteria for Diagnosis of Fat Embolism Syndrome

MINOR:Tachycardia (>100 bpm)

HyperthermiaRetinal fat emboli

Urinary fat globules

Decreased platelets

Increased ESR

DIC

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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.

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Adequate hydration and maximizing oxygenation minimize the hypotension and arterial hypoxemia that may accompany cementing of the prosthesis.

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Venous

thromboembolism is 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.)

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Antithrombotic prophylaxis is based on identification of risk factors .

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Antithrombotic Regimens to Prevent Thromboembolism

in Orthopedic Surgical PatientsHip and Knee Arthroplasty and Hip Fracture Surgery

LMWH* started 12 hours before surgery or 12 to 24 hours after surgery or 4 to 6 hours after surgery at half the usual dose and then increasing to the usual high-risk dose the following day.

Fondaparinux

(2.5 mg started 6 to 8 hours after surgery)

Adjusted-dose

warfarin

started preoperatively or the evening after surgery (INR target, 2.5; range, 2.0–3.0)

Intermittent pneumatic compression is an alternative option to anticoagulant prophylaxis in patients undergoing total knee (but not hip) replacement.

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Spinal Cord Injury

LMWH after primary hemostasis is evident

Intermittent pneumatic compression is an alternative when anticoagulation is contraindicated early after surgery.

During the rehabilitation phase, conversion to adjusted-dose

warfarin

(INR target, 2.5; range, 2.0–3.0).

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Elective Spine Surgery

Routine use of thromboprophylaxis, apart from early and persistent mobilization, is not recommended.

Knee Arthroscopy

Routine use of

thromboprophylaxis

, apart from early and persistent mobilization, is not recommended.

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Possible Explanations for Decreased Incidence of Deep Vein Thrombosis in Patients Receiving Regional Anesthesia

Rheologic changes resulting in hyperkinetic lower extremity blood flow and associated decrease in venous stasis and thrombus formation

Beneficial circulatory effects from epinephrine added to local anesthetic solution

Altered coagulation and

fibrinolytic

responses to surgery under neural blockade, resulting in decreased tendency for blood to clot

Absence of positive pressure ventilation and its effects on circulation

Direct local anesthetic effects (decreased platelet aggregation)

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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 .

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Neuraxial Anesthesia and Analgesia in Orthopedic Patients Receiving Antithrombotic Therapy

Low-Molecular-Weight HeparinNeedle placement should occur 10 to 12 hours after a dose.

Indwelling neuraxial catheters are allowed with once-

daily (but not twice-daily) dosing of LMWH.

It is optimal to place and remove indwelling catheters in the morning and administer LMWH in the evening to allow normalization of

hemostasis

to occur before catheter manipulation.

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Warfarin

Adequate levels of all vitamin K–dependent factors should be present during catheter placement and removal.Patients chronically on warfarin

should have a normal INR before performance of the regional technique.PT and INR should be monitored daily.

The catheter should be removed when INR <1.5.

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Fondaparinux

Neuraxial techniques are not advised in patients who are anticipated to receive fondaparinux..

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Nonsteroidal Anti-Inflammatory Drugs

No significant risk of regional anesthesia-related bleeding is associated with aspirin-type drugs.

For patients receiving warfarin or LMWH, the combined anticoagulant and

antiplatelet

effects may increase the risk of

perioperative

bleeding.

Other medications affecting platelet function (

thienopyridine

derivatives and glycoprotein

IIb

/

IIIa

platelet receptor inhibitors) should be avoided.

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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.)

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