Lippincott's Anesthesia Review: 1001 Questions and Answers

Chapter 10. Orthopedic Anesthesia

Thomas Halaszynski

    1.   The surgeon is performing a right total knee arthroplasty under a combined spinal–epidural anesthetic. The surgical team is providing you with information that within the next 15 minutes they plan to place bone cement (polymethylmethacrylate) to anchor the prosthesis. The most likely clinical side effect that may occur is

          A.   Hypertension

          B.   Increased work of breathing and hypercapnia

          C.   Cardiac arrhythmias

          D.   Decreased pulmonary shunt

    2.   Potential complications of use of a pneumatic tourniquet include all of the following, except

          A.   Tourniquet pain that is relieved by performing a peripheral nerve block

          B.   A compression nerve injury

          C.   Development of arterial thromboembolism

          D.   Pulmonary embolism

    3.   A 20-year-old male (status post car accident) sustained a right femur and pelvic fracture 2 days prior. In the last 24 hours, he has become progressively more short of breath, requiring 100% FIO2 to maintain an oxygen saturation in the high 80s and is now becoming more confused and disoriented. Physical exam reveals petechiae on the anterior chest wall, arms, and conjunctiva along with decreased breath sounds to auscultation. The most likely diagnosis is

          A.   Cognitive dysfunction

          B.   Pulmonary fat embolism

          C.   Undiagnosed pneumothorax

          D.   Congestive heart failure

    4.   Incorrect statement regarding neuraxial anesthesia and deep-vein thrombosis/pulmonary embolism (DVT/PE) in orthopedic surgical procedures is

          A.   Neuraxial anesthesia may reduce thromboembolic complications

          B.   Neuraxial anesthesia may reduce blood loss

          C.   Neuraxial anesthesia may decrease platelet reactivity

          D.   Neuraxial anesthesia may increase activity of both factor VIII and von Willebrand factor

    5.   On postoperative day 1, an orthopedic surgeon has consulted you about his total knee arthroplasty patient who is in severe pain and has failed a regimen of patient-controlled analgesia using morphine. He is now consulting you for an epidural catheter placement for postoperative pain control, and would like to know for what time interval once-daily prophylactic low-molecular-weight heparin (LMWH) should be held prior to performing the epidural procedure:

          A.   4 hours and no absolute contraindication to placement of a catheter

          B.   6 hours and a relative contraindication to place a catheter

          C.   12 hours and no absolute contraindication to placement of a catheter

          D.   24 hours and absolute contraindication to place a catheter

    6.   In the anesthesia preadmission testing clinic, you are assessing a 58-year-old female with a medical history significant for hypertension, diabetes, fibromyalgia, and rheumatoid arthritis (RA). The RA is affecting the upper extremities bilaterally and the cervical spine, but her RA symptoms are well-controlled with methotrexate. She is now presenting for an elective total hip arthroplasty. The radiographs that should be ordered to rule out atlantoaxial instability are

          A.   Lateral view: flexion of the cervical spine

          B.   Lateral view: extension of the cervical spine

          C.   No radiographs are indicated since the patient is asymptomatic

          D.   Lateral view: both flexion and extension of the cervical spine

    7.   You were involved in a complicated left lower leg procedure (open reduced internal fixation of proximal tibia–fibula fracture repair), where the final total tourniquet time was 3 hours 15 minutes. In the postanesthesia care unit, the patient showed no signs of any peripheral nerve injury of the left lower extremity. However, on postoperative day 2, you discovered that the patient required hemodialysis secondary to rhabdomyolysis. Which of the following could be responsible for the rhabdomyolysis?

          A.   Compartment syndrome

          B.   Prolonged tourniquet inflation time

          C.   Statin medication use that patient started 2 weeks prior

          D.   All of the above

    8.   Concurrent administration of all of the following anticoagulants and thrombolytic therapy should be avoided when planning for neuraxial blockade, except for

          A.   Fibrinolytic and thrombolytic therapy

          B.   Thrombin inhibitors (desirudin, lepirudin, bivalirudin, and Argatroban)

          C.   Therapeutic dosing of low-molecular-weight heparin (LMWH)

          D.   Subcutaneous heparin daily dose of 10,000 U or less

    9.   The most correct statement regarding blood loss that may occur in a patient with a hip fracture is

          A.   Intertrochanteric > base of femoral neck > subcapital

          B.   Transcervical > base of femoral neck > subcapital

          C.   Subtrochanteric > subcapital > transcervical

          D.   Subcapital > base of femoral neck > transcervical

  10.   A 76-year-old female is to undergo a right femoral neck fracture repair. You perform a spinal anesthetic using 1.5 mL 0.5% bupivacaine mixed with 100 μg of preservative-free morphine. How long should the patient be monitored for postoperative apnea/hypoventilation secondary to the intrathecal morphine administration?

          A.   3 days

          B.   48 hours

          C.   12 hours

          D.   24 hours

  11.   A 56-year-old female with medical history significant for obesity (BMI 50), hypertension, diabetes (IDDM), tobacco abuse, and asthma is scheduled for bilateral hip replacement surgery. Preoperative laboratory results show a hematocrit (Hct) of 45%, blood urea nitrogen of 25 mg/dL, and creatinine of 1.0 mg/dL. Immediately following application of cement for the second hip, the patient became hypotension with sinus tachycardia. Arterial blood gas results reveal an Hct of 23% that responds to a crystalloid fluid bolus and blood transfusion (2 L crystalloids, 1 L albumin, and 2 U packed red blood cells). The possible cause(s) for the hypotension is/are

          A.   Hypovolemia and/or low Hct

          B.   Pulmonary embolism

          C.   Vasodilation caused by monomer of the bone cement

          D.   All of the above

  12.   A 68-year-old female (5’1” and 250 lb) with a medical history of chronic lower back pain and radiculopathy in the lumbar 4 to sacral 1 vertebral levels presents for anterior and posterior fusion. Her home medications include methadone 75 mg daily, oxycodone 10 mg every 3 hours as needed, a fentanyl patch (50 μg/h), and lisinopril 10 mg daily. The patient stated she has 7/10 pain daily. All of the following should be considered in the perioperative pain management regimen for this patient, except

          A.   Continue with daily methadone

          B.   Consider a perioperative ketamine infusion

          C.   Consider transversus abdominis plane (TAP) block for the anterior abdomen

          D.   Add ketorolac 30 mg every 6 hours as needed for 14 days

  13.   You are administering anesthesia for a cervical spine procedure, and the surgeon has indicated that she plans to monitor somatosensory-evoked potentials (SSEPs) and motor-evoked potentials (MEPs). Your anesthetic plan includes avoidance of long-acting muscle relaxants in addition to avoiding the use of

          A.   1 MAC or higher of sevoflurane as needed for maintenance anesthesia

          B.   Half MAC of nitrous oxide to supplement the inhalation agent

          C.   Continuous propofol infusion as anesthesia maintenance

          D.   Dexmedetomidine to smooth out the anesthetic delivery

  14.   All of the following can be used to assist in reducing the amount of perioperative surgical blood loss in an orthopedic procedures, except

          A.   Hemodilution

          B.   Controlled hypotension

          C.   Tranexamic acid

          D.   Aprotinin

  15.   All of the following statements when positioning patients for spine surgery in the prone position are true, except

          A.   The neck should be in neutral position (without hyperextension or hyperflexion)

          B.   The eyes must be free of pressure and checked periodically

          C.   The abdomen must always be supported (never permitted to hang freely)

          D.   The arms are kept at less than 90 degrees of extension and flexion

  16.   The most incorrect statement regarding postoperative vision loss (POVL) that may occur during prone positioning in spine surgery patients is

          A.   Ischemic optic neuropathy accounts for the highest incidence of POVL

          B.   Ischemic optic neuropathy is associated with decreased ocular perfusion pressure

          C.   Prone positioning, greater than 1 L intraoperative blood loss, and surgery lasting greater than 6 hours represent the highest risk

          D.   POVL due to central retinal artery occlusion (CRAO) tends to be bilateral

  17.   After 180 minutes of tourniquet time during a difficult right total knee arthroplasty in a patient under sedation and intraoperative anesthesia provided by a combined spinal–epidural, the tourniquet is released and surgical closure is started. The patient may experience all the following subsequent to tourniquet release, except

          A.   Hypotension and tachycardia

          B.   Transient increase of end-tidal carbon dioxide

          C.   Arrhythmia secondary to increased serum potassium

          D.   Arrhythmia secondary to increased total serum calcium

  18.   The most incorrect statement regarding placement of a femoral perineural catheter for pain management during unilateral knee replacement surgery is that a femoral nerve block when compared to neuraxial blockade

          A.   Provides equipotent analgesia

          B.   Is associated with reduced incidence of pruritus, nausea, and vomiting

          C.   Is associated with reduced incidence of urinary retention

          D.   Femoral nerve block when combined with a sciatic nerve block can provide adequate analgesia for knee surgery

  19.   A 56-year-old female is scheduled for a right total shoulder replacement in the beach chair position. Medical history is significant for hypertension, diabetes, and a recent transient ischemic attack. The surgeon is requesting a hypotensive technique to reduce intraoperative blood loss. Where is the most optimal location to place the arterial line transducer?

          A.   The level of the heart as this is the classic way of measuring

          B.   The level of the sternum to measure adequate perfusion to the brain

          C.   Level of the external meatus to monitor brain stem perfusion

          D.   Level of shoulder to measure adequate shoulder perfusion

  20.   The anesthetic agent(s) that can cause adverse changes on the wave forms when monitoring somatosensory-evoked potentials (SSEPs) is/are

          A.   High concentrations of inhalational agents (reduces wave form amplitude)

          B.   1 MAC of nitrous oxide (reduces wave form amplitude)

          C.   Intravenous anesthesia with ketamine (exaggerates wave forms)

          D.   ALL of the above

  21.   Which of the following surgical conditions may negatively influence changes on somatosensory-evoked potentials (SSEPs) wave forms?

          A.   Spinal cord injury

          B.   Ischemia induced by hypoperfusion

          C.   Intraoperative bleeding

          D.   All of the above

CHAPTER 10 ANSWERS

    1.   C.   Placement of bone cement (bone cement implantation syndrome) can result in any combination of adverse events including hypoxia, hypotension, cardiac arrhythmias (possibly heart block or even sinus arrest), pulmonary hypertension, and decreased cardiac output.

    2.   A.   Use of a compression tourniquet on upper and lower extremities can facilitate surgery and decrease blood loss, but it can result in complications and cannot be applied for prolonged periods. Use of such devices can be associated with ischemic pain that is not typically or completely relieved by performing peripheral nerve blocks of the extremity. Metabolic alterations upon tourniquet release, arterial thromboembolism, and pulmonary embolism are other potential complications.

    3.   B.   A venous fat embolism will typically present itself within 72 hours following long-bone and/or pelvic fracture injuries. Such a condition may also occur following cardiopulmonary resuscitation, parental feeding with lipid infusion, and liposuction surgery. The classical triad includes dyspnea, confusion, and petechiae.

    4.   D.   Advantages of neuraxial anesthesia in orthopedic surgery may include reduced incidence of DVT and PE formation, decreased platelet activity, decreased factor VIII and von Willebrand factor activity, and attenuation of stress hormone responses.

    5.   C.   For patients receiving once-daily dosage of LMWH for prophylaxis, both epidural and spinal neuraxial techniques may be performed (or neuraxial catheters placed or removed) 10 to 12 hours following the previous dose of LMWH. In addition, a 4-hour time delay should occur before administering the next dose of daily prophylactic LMWH.

    6.   D.   Advanced RA can affect the cervical spine such that patients may require treatment including steroids, immune therapy, and/or methotrexate. Radiographs of both flexion and extension with lateral views of the cervical spine are necessary to rule out atlantoaxial instability. If atlantoaxial instability is present, intubation should be performed with inline stabilization utilizing video or fiberoptic laryngoscopy to minimize excessive head and neck movement in order to reduce the incidence of cervical spinal cord/nerve root injury.

    7.   D.   Any form of muscle damage of sufficient severity can cause rhabdomyolysis. Multiple causes can be present simultaneously in one individual. Some patients may have an underlying muscle condition, usually hereditary in nature, which may make them more prone to rhabdomyolysis. Rhabdomyolysis can be induced by several conditions including compartment syndrome, prolonged tourniquet inflation time, medications such as statins, and malignant hyperthermia. It is suggested that tourniquet times usually be kept to 2 hours or less to decrease the risk of nerve injury, ischemia, and rhabdomyolysis, which could lead to renal failure.

    8.   D.   According to the American Society of Regional Anesthesia and Pain Medicine anticoagulation guidelines, medications such as antiplatelet agents (Plavix, and intravenous glycoprotein IIb/IIIa inhibitors), thrombolytics, fondaparinux, direct thrombin inhibitors, or therapeutic LMWH present an unacceptable risk for spinal and/or epidural hematoma development without sufficient time lapse between administration of such medications and neuraxial techniques. Maximum administration of subcutaneous heparin of 5,000 U bid is estimated to be safe with epidural and spinal anesthesia. Heparin administration of 5,000 U tid is not known to be accepted in clinical practice in conjunction with neuraxial blockade.

    9.   A.   Blood loss in a patient secondary to a hip fracture can be significant, and some anesthesiologists plan to utilize cell savers and/or perform hypotensive techniques to minimize further blood loss. Blood loss from a hip fracture depends on the actual location of the fracture. As a general rule, intracapsular (subcapital, transcervical) fractures have been associated with less blood loss than extracapsular (base of the femoral neck, intertrochanteric, subtrochanteric) fractures, as the capsule decreases blood loss by acting like a tourniquet. In general, blood loss from a subtrochanteric and intertrochanteric > base of femoral neck > transcervical and subcapital.

  10.   D.    Intrathecal morphine can depress ventilation and CO2 responsiveness that can last for up to 24 hours. The first peak effect occurs about 6 to 8 hours post injection, and the second peak could happen as late as 24 hours later. The physiologic and pharmacologic mechanisms of this include vascular opioid uptake by the epidural or subarachnoid venous plexuses, rostral spread of the aqueous cerebrospinal fluid to the brainstem, and/or direct perimedullary vascular channels.

  11.   D.    Total hip arthroplasty surgery can be characterized by significant blood loss, especially in the situation of bilateral hip replacement. In acute bleeding, measuring an Hct may not accurately reflect the true value as equilibrium takes some time to show the true Hct. In addition, bone cement can cause vasodilation, which can further contribute to the low blood pressure. Cement placement has been associated with pulmonary embolism and pulmonary hypertension.

  12.   D.    Chronic pain is often a common occurrence in patients presented for spine/back surgeries. A multimodal therapeutic pain management strategy aimed at different pain cascade pathways is frequently utilized. It is a common practice to continue methadone if patients are already taking such medications and to consider starting methadone in patients with uncontrolled postoperative pain. Ketamine (GABA agonist) is effective in chronic pain patients. TAP blockade with local anesthetics can provide effective somatic pain relief of the anterior abdomen that will help in the treatment of incisional pain. Evidence supports the use of nonsteroidal anti-inflammatory drugs at low doses in spine surgeries, but higher concentrations have been associated with a rate of nonunion, so are therefore discouraged.

  13.   A.    High concentrations of potent inhalational agents (such as desflurane and sevoflurane) may increase neuromonitoring latency and decrease amplitude of the SSEP and MEP. Therefore, inhalation agents can be used for intraoperative maintenance anesthesia, but are used at less than one full MAC concentration. Intravenous (IV) anesthetics are more commonly used for maintenance of anesthesia, as they are more compatible with SSEP and MEP neuromonitoring (some expected, but tolerable changes on either latency and/or amplitude). These IV anesthetics include propofol, ketamine, etomidate, dexmedetomidine, benzodiazepines, and opioids independently and in various combinations. Opioids have the least potential to interfere SSEP and MEP neuromonitoring.

  14.   D.    Spine surgery can be associated with significant blood loss. Surgical and anesthetic techniques that have been developed to control perioperative blood loss include hemodilution, autologous blood donation preoperatively, use of cell saver, and epinephrine at wound site. Pharmacologically, antifibrinolytics such as tranexamic acid and ε-aminocaproic acid have been used with some efficacy. Tranexamic acid is a synthetic derivative of the amino acid lysine, and it is used to treat or prevent excessive blood loss during surgery and in various other medical conditions. Aprotinin has been associated with a 50% increase of cardiac side effects (myocardial infarction/congestive heart failure), increase (double) of the risk of stroke, and higher death rates (increased mortality).

  15.   C.    Prone positioning of patients needs to be carefully executed, especially during spine surgeries (prolonged procedures) and in patients who have other associated comorbidities such as rheumatoid arthritis and ankylosing spondylitis. The endotracheal tube needs to be properly secured, and eyes and nose should be padded and checked periodically to ensure that they are pressure-free. The neck and arms should be kept positioned in an anatomically neutral position. The abdomen needs to remain free to avoid increased venous pressure (assists in reducing increased venous bleeding) and to reduce the incidence of abdominal compartment syndrome that can develop during prolonged duration of surgical intervention and aggressive fluid administration.

  16.   D.    Ischemic optic neuropathy is a major cause of perioperative POVL accordingly to the vision loss registry collected by the ASA. Any increase of intraocular pressure (IOP) or decrease on mean arterial pressure (MAP) will affect ocular perfusion pressure (OPP), particularly with patients in a head-down position where edema can develop in the orbit that will increase venous pressure. OPP = MAP − IOP. CRAO accounts for a small percentage of patients who experience vision dysfunction according to the vision loss registry. CRAO may be embolic in nature or the result of direct pressure on the eyeball; therefore, it tends to be mostly unilateral.

  17.   D.    Release of a tourniquet used on an extremity during surgery is often associated with the release of metabolic (acidotic) by-products from the ischemic limb that are dumped into the systemic circulation. In patients with poor preoperative functional status or those that may experience significant intraoperative blood loss, the increased systemic metabolic by-products may be enough to result in hypotension and cardiac arrhythmia that may require volume resuscitation and/or pharmacologic support. In rare instances, the hyperkalemia may need to be treated (sodium bicarbonate or calcium).

  18.   D.    During unilateral knee replacement surgery, properly functioning lumbar epidural and femoral perineural catheters can provide equivalent perioperative analgesia. However, a peripheral nerve block using a femoral perineural catheter does not have several of the typical side effects that can be associated with neuraxial blockade, such as more intense sympathectomy, pruritus (when opioids are mixed with local anesthetics), nausea and vomiting, urinary retention, or orthostatic hypotension and lightheadedness. Several studies have shown that patients with regional anesthesia/analgesia (femoral catheter patients may meet discharge criterion earlier) may show earlier improved outcomes. Considering variations of surgical technique, the postoperative pain during total knee arthroplasty is located on the anterior knee that can be equally controlled by either lumbar epidural or femoral nerve block alone. For bilateral knee replacement surgery, either bilateral femoral catheters or lumbar epidural catheter may be a reasonable option.

  19.   C.    Shoulder operations may be performed in either a sitting (“beach chair”) or the lateral decubitus position. The beach chair position may be associated with decreases in cerebral perfusion leading to the potential for increased risk of blindness, stroke, and brain ischemia. If a controlled hypotension technique is chosen, an arterial transducer should be positioned most preferably at the level of the brain stem (i.e., external meatus of the ear).

  20.   D.    Most of the currently used anesthetic agents may have some effects/negative influence on SSEP (differences may be minor or major changes). Several other perioperative variables such as hemoglobin concentration, temperature, CO2, and arterial blood pressure may also influence the SSEP tracing.

  21.   D.    There are a host of reasons causing negative SSEP-tracing changes. In addition to several anesthetic considerations (from anesthetic agent choice to techniques used), there are surgical techniques and considerations that can influence SSEP. Direct trauma, ischemia, and pressure to the spinal cord are capable of inducing acute changes on SSEP. In addition, spinal cord ischemia changes secondary to decreased blood supply, and/or vessel injury (stretching/pressure) may take as much as a half an hour to manifest itself.