Chapter 40
Anesthesia for Orthopedics and Podiatry
The Merriam-Webster dictionary defines orthopedics as “a branch of medicine concerned with the correction or prevention of deformities, disorders, or injuries of the skeleton and associated structures (as tendons and ligaments)”.1 Evidence of such “corrections” dates back many centuries. Egyptian artifacts have been found that demonstrate the use of splints for patients, and some of the earliest documented orthopedic interventions came from the battlefields of the gladiators. Jean-Andre Venel established the first orthopedic institute in 1780. Much progress in orthopedics has been made in recent decades including the development of better arthroscopic techniques, total hip and knee replacements, ligament repairs using minimally invasive techniques, spine surgeries, and more. As the baby boomers born after World War II reach retirement age, the demand for orthopedic repair and the incidence of degenerative joint disease are expected to increase.2
Preoperative assessment for orthopedic patients follows much the same guidelines used for any other surgical candidate. A thorough review of systems, review of home medications and the last date taken, current anticoagulant status, and baseline laboratory values are only some of the components of a preoperative assessment of these patients. Often for patients scheduled for total joint replacement, a baseline complete blood count (CBC), a pregnancy test (for females of childbearing age), and a urinalysis may be completed. Also, most orthopedic surgeons prefer to evaluate their patients for the presence of infection before committing to joint replacement surgery.3 Surgical site wound infection is a serious and potentially catastrophic complication after joint arthroplasty.4 Pathogens in the urinary tract are common, and their presence can create a potential reservoir of resistant pathogens and increase patient morbidity.
Many institutions require their health care providers to be responsible for implementing appropriate interventions under the SCIP guidelines and, just as important, require them to document these interventions. These data are abstracted at hospitals across the country, and the data are then fed into a website called Hospital Compare. The Hospital Compare website allows patients and their families to view how a particular hospital participates in the guidelines and how the outcomes of that hospital compare to other hospitals in the area, specific to those guidelines. In addition to creating a best practice environment, and better patient outcomes, compliance with these measures are often incentivized financially through private insurers as well as the CMS. All anesthetists should familiarize themselves with the guidelines their institution has in place and should strive to fulfill their responsibilities accordingly.5 The most up-to-date guidelines related to SCIP can be found at www.jointcommission.org/surgical_care_improvement_project.
Advances in technology are yielding a much higher rate of arthroscopic procedures. Outpatient surgery is now the routine for many orthopedic procedures. Outpatient surgery is being used for everything from shoulder repair to orthopedic repair in the knee, ankle, wrist, and elbow. The advantages of today’s surgical techniques are readily apparent. Smaller incisions mean less pain. Patients who have arthroscopic procedures experience faster recovery from anesthesia, have shorter lengths of stay, use fewer narcotics for pain relief, and return to work more quickly than those undergoing open procedures.6 From an anesthesia standpoint, it means more patients are being managed on an outpatient basis.
Pneumatic Tourniquet
One of the ways blood loss can be diminished in the operating theater is through the application of the pneumatic tourniquet. The advantages of a bloodless field are important for the surgeon. Pneumatic tourniquets maintain a relatively bloodless field during extremity surgery, minimize blood loss, aid identification of vital structures, and expedite the procedure.7,8 The components of the pneumatic tourniquet consist of the inflatable cuff, connective tubing, a pressure device, and usually, a timer. Specialized training and understanding of the application and management of the pneumatic tourniquet is required for proper management of the device intraoperatively. Safety considerations for use of a tourniquet are noted in Box 40-1.
Tourniquets are generally applied after the initiation of anesthesia. The time of inflation should be documented in the anesthesia record and should be in parallel with the time documented in the operating room (OR) record. Interruption of blood supply leads to tissue hypoxia and acidosis.9 The degree of hypoxia and acidosis is partially influenced by the duration of insufflation. For this reason, the inflation device also comes with a built-in timer, generally set for 60-minute increments, with an alarm that will sound as a warning when the allotted time has been exhausted. A maximum of 2 hours is generally considered safe.10 The pressure to which the tourniquet should be inflated depends on the patient’s blood pressure and the shape and size of the extremity.
Deflation of the tourniquet results in the release of metabolic waste into the systemic circulation. The release of these substances can cause metabolic acidosis, hyperkalemia, myoglobinemia, myoglobinuria, and renal failure.11,12 The deflation of the tourniquet may be marked by transient changes in the hemodynamics or pulse oximetry readings for the patient. Most of these resolve quickly, except in those patients with extreme conditions related to their cardiac or vascular status. Box 40-2 lists common physiologic changes that occur with pneumatic tourniquet.
Tourniquet Pain
One of the greatest concerns when the tourniquet is in use is the patient perception of tourniquet pain. In 1944 Denny-Brown and Brenner13 reported the first investigation into the cause of tourniquet discomfort. They listed characteristic anatomic changes associated with tourniquet ischemia that were due to acute compression of the nerves under the inflated cuff. Compression of the intraneural blood vessels caused a secondary ischemia of the nerve fibers. Similar reports of “tourniquet discomfort” or “aching” despite adequate spinal anesthesia prompted considerable attention being directed toward discovering ways to minimizing subjective discomfort. Based on their discoveries and subsequent measurements of “occlusive pressure” in 1979, Klenerman and Hulands14 suggested using tourniquet pressures of two times the patient’s systolic blood pressure to minimize the subjective discomfort and destruction of tissues. Klenerman15 modified this recommendation a year later to between 50 and 75 mmHg more than the patient’s systolic pressure.
The ischemic pain associated with tourniquet application is similar to that of thrombotic vascular occlusion and peripheral vascular disease.16 At about 45 to 60 minutes after tourniquet pressurization, patients report various symptoms associated with dull aching that progress to burning and excruciating pain that may require general anesthesia. Once the pain begins, it is often resistant to analgesics and anesthetic agents, despite the anesthetic technique. Even with a well-controlled general anesthetic at the time of tourniquet inflation, ischemic pain may begin during this same time interval and may cause increasing heart rate and blood pressure that require pharmacologic intervention.17
Myelinated A-delta and unmyelinated C fibers differ in their sensitivity to local anesthetics. As the concentration of local anesthetic decreases, the activation of C fibers increases, but the A-delta fiber activation is still suppressed. This means that C fibers may be more difficult to anesthetize than A-delta fibers, and tourniquet pain therefore seems more consistent with pain sensation carried by C fibers.16 Other research has shown that certain local anesthetics enhance the effect of the blockade in the presence of increased stimulation of the isolated nerve fiber. For example, the potency of bupivacaine is enhanced by an increase in the rate of nerve stimulation and may offer an advantage by lowering the incidence of tourniquet pain.18
Regardless of the sensory level achieved in these patients, they still experience tourniquet pain. It is apparent that a high-quality blockade of the sacral roots is more important than the thoracic sensory level in reducing the incidence of tourniquet pain, because the intensity of pain may be due to ischemia of the entire leg, as well as under the cuff.19 The addition of opioids, ketorolac, and melatonin to local anesthesia solutions have all shown some efficacy in reducing the incidence of tourniquet pain.20–22 Sedation with dexmedetomidine is also effective.23
Patient Positioning
Chapter 21 provides an excellent overview of proper positioning during surgery. It is important to have a thorough understanding of the physiologic changes that occur in various positions. Appropriate patient positioning must allow optimal exposure of the surgical site, allow for appropriate monitoring throughout the procedure, provide good access to the patient’s airway, allow for comfort and warmth, minimize or prevent physiologic functioning compromise, protect all body systems, and maintain patient dignity.24 Positions chosen may include supine, lateral decubitus, prone, and even beach chair/sitting. Neutral alignment and proper padding of exposed neural pathways can help diminish injuries sustained intraoperatively related to positioning. Communication between the entire team (i.e., anesthesia, OR nurse, and surgeon) will yield the best outcomes for the patient.
Over the millennia, human physiology has adapted to being in an upright or erect position for the majority of the wakeful hours. For example, in the upright position there are three zones of ventilation-perfusion within the lungs: (1) areas where alveolar pressure is greater than arterial pressure, (2) areas of complex, variable pressure gradients between alveolar and arterial components, and (3) areas where arterial pressure is greater than alveolar pressure. Figure 40-1 illustrates lung zones 1, 2, and 3. Other examples of physiologic adaptation are the valves found in dependent areas of the venous system, such as the extremities, and the absence of valves in nondependent areas, such as the cranium. Changes from the upright position produce corresponding physiologic changes24,25 (Figure 40-2).
Arthroscopy
Arthroscopy is a minimally invasive surgical procedure performed to examine and sometimes repair damage of the interior of a joint using an arthroscope.26 The concept was introduced in the United States in 1926.27 However, without the availability of practical sources of illumination, arthroscopy languished. The development of fiber-optic light sources in the 1970s brought a resurgence of interest in the use of arthroscopy. Initially, arthroscopy was used to obtain a diagnosis of a patient’s orthopedic malady so a definitive, corrective surgical procedure could be performed. As interest in the procedure and technique increased, coupled with development of the necessary smaller surgical instrumentation, previously open surgical procedures on the knee, such as partial or complete meniscectomy, loose-body removal, or ligament repair or reconstruction, were attempted and refined solely via the arthroscope.
Successful performance of arthroscopic procedures on the knee produce several benefits for the patient, including reduced blood loss, less postoperative discomfort, and reduced length of rehabilitation. The success achieved with arthroscopic procedures on the knee led to application of the principles and techniques to other joints (e.g., the shoulder, elbow, wrist, hip, ankle, and phalangeal joints of the foot).28,29 Many of these surgeries have become routine outpatient procedures. Through the middle portion of the 1990s, application of arthroscopic procedures focused on the shoulder. Accordingly, shoulder arthroscopy use ranges from simple debridements to more complex rotator cuff repairs.27 The development and refinement of shoulder arthroscopic procedures mirrors that of knee arthroscopic procedures; that is, as more skill and comfort are obtained with initial procedures, more traditionally open surgical treatments are attempted solely via the arthroscope.
Anesthetic Management
Arthroscopic procedures may be managed by almost any of the available anesthesia techniques (e.g., general anesthesia, regional anesthesia, combined regional and general anesthesia, and local blockade with sedation). Patient selection for a given anesthetic technique is crucial with arthroscopic procedures, as with all operative procedures. As previously mentioned, for some patients there is absolutely no substitute for receiving general anesthesia. Critical factors in the selection and presentation of the available anesthesia techniques appropriate for arthroscopic procedures are the patient positioning necessary to facilitate the proposed arthroscopic procedure and the overall state of health of the patient. For example, shoulder arthroscopy uses one of two positions to accomplish the surgery, either lateral decubitus or modified Fowler’s (“beach chair”) position.30 The choice of position is determined in part by the nature and extent of the malady being surgically addressed. For some shoulder arthroscopy procedures, supplemental traction with weights and abduction may be necessary to provide optimum operative visualization (Figure 40-3); for others, the modified Fowler’s position may be used with the force of gravity or manual traction providing sufficient operative visibility. Reviewing the patient’s chart and more importantly, personally interviewing the patient, along with understanding the physiologic changes associated with various positions, assist in choosing the best care for each patient.
Patient positioning for arthroscopic procedures can encompass virtually the entire gamut of possible operative positions. Most often, arthroscopic procedures for lower extremity joints use the supine position, as do most arthroscopic procedures on the upper extremities. Arthroscopy on the knee requires the supine position with the foot of the OR bed lowered (Figure 40-4). The nonoperative leg should either be wrapped with an elastic bandage or have some form of compression stocking in place to reduce pooling of blood and the potential for thrombus formation. At times, patients undergoing elbow arthroscopy may be placed in the supine, lateral decubitus, or prone position; the position is dictated by operative necessity and surgeon preference (Figures 40-5 and 40-6). The prone position is advantageous primarily because of the better limb stability during the procedure.31 Shoulder arthroscopy is usually accomplished via either the modified Fowler’s position or the lateral decubitus position, based on optimal access to the injury and surgeon preference (see Figure 40-3).30 Hip arthroscopy is also typically accomplished via the lateral decubitus or the supine position, with the patient on a fracture table (Figure 40-7). The fracture table is used to provide greater stability while traction is applied, using either weights and counterweights (lateral decubitus position) or mechanical traction attached to the leg-holding device of the fracture table (supine position).32
Complications from arthroscopic procedures represent a small percentage of the total number of procedures performed.33–36 Complications that may occur include subcutaneous emphysema, pneumomediastinum, and potentially life-threatening tension pneumothorax. Accordingly, complications resulting from arthroscopic procedures that particularly concern the nurse anesthetist are relatively few. The full range of potential anesthetic complications associated with patient positioning apply (e.g., inadvertent extubation, eye or corneal injury, visual loss from the prone position, and nerve injury from improper patient positioning). Blood loss is not generally a concern, but significant and sustained hypotension warrants immediate and thorough investigation. The pneumatic tourniquet may be used to provide a clear, bloodless surgical field. Trocar insertion sometimes results in inadvertent vessel puncture that may go undetected because of the tourniquet. In cases that are located proximally (i.e., hip or shoulder) and therefore done without a tourniquet, vascular damage is discovered much earlier.
To provide optimal visualization of joint structures during arthroscopic procedures, the irrigating fluid used to distend the operative joint is instilled under pressure. This is achieved through gravity or mechanical pressurization. The typical irrigation setup uses large bags of irrigating solution, 3 to 5 L in volume. The nurse anesthetist should be aware of the fluid being infused in comparison with the outflow. Even small differences can add up to a large volume for the patient, especially in the case of an extended procedure. This absorption could potentially lead to fluid volume overload, congestive heart failure (CHF), pulmonary edema, or even hyponatremia if sterile water is used.33–36
During subacromial decompression, subcutaneous emphysema, tension pneumothorax, and pneumomediastinum have been reported during shoulder arthroscopy.35 These complications appear to be associated at least in part with the use of mechanical irrigation pumps and power-saver suction. Careful assessment during this irrigation period is important. Box 40-3 lists the signs and symptoms of tension pneumothorax. Because tension pneumothorax is a potentially life-threatening event, early recognition and treatment are paramount. Ideally, placement of a chest tube is most desirable to relieve the increased intrathoracic pressure. An immediate and very effective treatment is needle decompression with a 14- to 18-gauge intravenous angiocatheter placed into either the second or third intercostal space anteriorly or the fourth or fifth intercostal space laterally. Successful decompression is accompanied by a sudden rush of air, as well as readjustment of physical symptoms and vital signs back toward the patient’s normal parameters. After successful decompression, the intravenous catheter stylet should remain in place and be covered or capped to prevent air from being sucked back into the chest cavity until a chest tube can be properly inserted.37,38
Arthroplasty
Arthroplasty is the surgical replacement of all (total arthroplasty) or part (hemiarthroplasty) of a joint to achieve a return of natural motion and function of the joint, as well as restoration of the controlling function of the surrounding soft tissues (i.e., muscles, ligaments, and tendons). The goals of arthroplasty are pain relief, stability of joint motion, and deformity correction. The original hip prosthesis was fabricated from stainless steel. Prostheses currently in use are stronger metal alloys, based on nonferrous metals, generally cobalt or titanium. These alloys demonstrate greater tensile strength and are more resistant to fatigue than the original stainless steel. The search for stronger metals that can withstand greater amounts of abuse is persistent because of the increasing demand for these components to last longer. And in fact, even younger groups of patients are lining up for joint replacements as people have become more active and athletic. The rigors of activities such as running and skiing are leading to the need for increased numbers of joint replacements in patients that are younger than ever before.39
Joint Arthroplasty
Several hundred thousand patients in the United States undergo some form of hip arthroplasty each year. The majority of patients are over age 65 and more than 75% have at least one comorbidity when they present for surgery.40 Women are twice as likely as men to require the surgery. Hip arthroplasty is most often indicated for patients experiencing degenerative joint disease or arthritic damage. A report on outcomes noted that, in patients having total joint arthroplasty, younger age and male sex are associated with an increased risk of revision. Older age and male sex are associated with increased risk of mortality and older age is related to worse function, particularly among women. Age and sex do not influence the outcome of pain. Despite these differences, all subgroups derived benefit from total joint arthroplasty.41
Once anesthesia induction is complete, the patient is positioned, prepped, and draped for incision. After a final timeout, skin incision is made. The femoral head and neck are excised, leaving the femoral canal open. The femur is highly vascular, as is the acetabulum, and the reaming required to prepare them for receipt of orthopedic components often opens venous sinuses, which can result in significant blood loss. For these patients, intraoperative blood loss ranges from 500 to 1000 mL per case.42
The hemoglobin threshold at which red-cell transfusion is warranted is controversial. A recent study compared a liberal strategy of transfusion at a hemoglobin below 10 g/dL after hip fracture with a more restrictive strategy of transfusion at a hemoglobin below 8 g/dL. The liberal and restrictive strategy groups were similar with regard to rates of death, inability to walk independently on 60-day follow-up, and in-hospital morbidity in elderly patients at high cardiovascular risk.43
BCIS has no agreed-upon definition, although it is characterized by a number of clinical features that may include hypoxia, hypotension, cardiac arrhythmias, increased pulmonary vascular resistance (PVR), unexpected loss of consciousness when regional anesthesia is administered, and cardiac arrest. The etiology of these effects is poorly understood and only suggested. Some theories involve the role of emboli formed during cementing and prosthesis insertion. Several mechanisms such as histamine release, complement activation, and endogenous cannabinoid-mediated vasodilation have been proposed. It is most commonly associated with hip arthroplasty but may also occur during other cemented procedures including knee arthroplasty and vertebroplasty. Although definitive studies are lacking, it is estimated to occur in 2% to 17% of surgeries. It usually occurs at the following stages in the surgical procedure: femoral reaming, acetabular or femoral cement implantation, insertion of the prosthesis or joint reduction, or occasionally after limb tourniquet deflation. Numerous patient-related risk factors have been implicated and are given in Box 40-4.
