Anesthesia and Perioperative Medicine

Asthma

A common pulmonary disorder in athletes, asthma is marked by restriction of airflow in the lungs, narrowing of the airways, and inflammation of the bronchi. Bronchoconstriction and inflammation induce shortness of breath, wheezing, coughing, and chest tightness. The prevalence of exercise-induced bronchospasm is 8% to 12% in the general population but may be as high as 50% in elite athletes and those competing in cold-weather sports. Several high-profile athletes with asthma, including Billy Jean King, Dennis Rodman, Jackie Joyner-Kersee, and Amy Van Dyken, have performed at the highest level with adequate treatment.

Triggers include smoking, environmental, respiratory viruses, odors, and exercise. The specifics of diagnosis and therapy for persons with asthma are detailed in a separate chapter in this book. Asthma can be diagnosed with a thorough history and physical examination and various provocative tests. Although multiple options are available to treat asthma, an important tenet is prevention by avoidance of triggering agents and maintenance therapy. Common strategies for maintenance and treatment of exacerbations include β ₂ agonists (with albuterol being the most commonly used), inhaled corticosteroids, systemic corticosteroids, anticholinergic drugs, leukotriene-receptor antagonists, and methylxanthine agents. Drugs may be administered by nebulizer, metered-dose inhaler, orally, or intravenously in emergency situations. Before a patient undergoes elective surgery, it is important that asthma be optimally controlled. Despite the bronchodilating properties of most anesthetics, asthmatics are more prone to bronchospasm after airway manipulation under anesthesia. Avoidance of general anesthesia and endotracheal intubation may be beneficial. When a general anesthetic is needed, a laryngeal mask airway has been shown to cause less airway reactivity than an endotracheal tube.

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is defined by periods of hypoventilation or apnea caused by airway obstruction during sleep. The severity of disease can be determined by the number of obstructive episodes, degree of oxygen desaturation, number of micro-arousal episodes, and number of arrhythmias per unit of time. Up to 90% of individuals with moderate to severe sleep apnea may remain undiagnosed.

OSA may be more common in athletes than originally thought. A study of eight randomly selected NFL teams and 302 players demonstrated a 14% incidence of sleep apnea with a 34% incidence in linemen. Dr. Archie Roberts, a retired heart surgeon who has teamed with the Mayo Clinic to screen retired NFL players, has noted an alarming incidence of OSA. The incidence of sleep-disordered breathing was present in 52.3% of the former football players. Furthermore, a study of sumo wrestlers in Tokyo found that 11 of 23 wrestlers had significant sleep-disordered breathing. Clearly, OSA is a problem that entails clinical vigilance, even in athletes who are presumed to be healthy.

Obstruction of the upper airway during sleep or sedation occurs from a decrease in oropharyngeal and laryngopharyngeal tone and leads to partial or complete airway obstruction. An increase in airway resistance, hypoxia, and hypercarbia ensue, resulting in an increase in sympathetic tone and subsequent patient arousal. Complications of OSA include chronic hypoxia, hypoxemia, and hypercarbia leading to pulmonary hypertension, right heart failure, and sudden death. Less obvious associations between OSA and long-term sequelae include depression, hypertension, coronary artery disease, and stroke.

OSA is a significant problem in the postoperative period. Sedatives, narcotic drugs, hypnotic agents, and muscle relaxants can exacerbate symptoms. Because of pain and the inherent stress of surgery, patients experience disturbances in rapid eye movement sleep patterns for several days after the immediate postoperative period. The increased risk of obstruction and other complications should be considered when planning intraoperative and postoperative care. Limiting narcotics, benzodiazepines, and general anesthesia (GA) in addition to educating patients about the risks of OSA may be helpful.

A thorough clinical history and appropriate screening may suggest a diagnosis of OSA. Symptoms of OSA include daytime sleepiness, snoring, witnessed apnea, poor concentration, morning headaches, moodiness, and irritability. Males who have hypertension, are overweight, smoke, and have a larger neck circumference are more likely to have OSA. Fig. 29.1 shows the STOP-BANG questionnaire. Because many risk factors for OSA are well known, various screening tools to help identify patients with OSA are used extensively and include the most validated STOP-Bang scoring system, P-SAP screening tool, Berlin screening tool, and American Society of Anesthesiologists (ASA) checklist.

Diagnosis of OSA can be made with polysomnography and a multiple sleep latency test. The mainstay of treatment is the use of a continuous positive airway pressure (CPAP) machine, which opens the upper airway and prevents obstruction. Oral or nasal masks are custom-fit for ease of use and comfort, but can still be obtrusive for some patients, leading to noncompliance. Other treatments for OSA include weight loss, dental devices, uvulopalatopharyngoplasty, tonsillectomy and/or adenoidectomy, craniofacial advancement techniques, somnoplasties, and nasal surgeries. OSA has been implicated in both inpatient and outpatient deaths and is exacerbated by many factors that occur in the perioperative period.

In 2016, guidelines and recommendations from the Society of Anesthesia and Sleep Medicine (SASM) were released. There is a moderate level of evidence that OSA increases patients’ risk for perioperative complications. While it is generally recommended that adult patients be screened for OSA before surgery, there is little evidence to support benefits of preoperative screening. Despite this, there is consensus that identifying patients with or likely to have OSA allows providers to utilize multi-modal analgesic techniques and avoid general anesthesia when possible. Patients with OSA should be screened for other systemic diseases and all co-morbidities should be optimized prior to proceeding with elective surgery.

Athletic Heart Syndrome

AHS is an adaptive physiologic condition manifested by enlargement of the heart in response to vigorous and frequent exercise, enhanced efficiency, and bradycardia (as low as 30 to 40 beats per minute). First described in 1899 by the Swedish physician Henschen, AHS was discovered by percussing hearts and comparing the heart sizes of cross-country skiers and sedentary patients. The heart increases in size in response to recurrent systemic oxygen deficits, resulting in increased muscle mass and increased ventricular chamber size, which facilitates cardiac output during exercise. AHS is benign yet vital to recognize, because bradycardia and cardiac hypertrophy can be a concern for clinicians and can be confused with life-threatening HCM. Diagnosis is made with electrocardiogram, a chest radiograph, or a transthoracic echocardiogram. Although AHS is not a health concern, a low resting heart rate may predispose athletes to vasovagal reactions manifested by diaphoresis, nausea, and syncope.

Hypertrophic Cardiomyopathy

Also known as hypertrophic obstructive cardiomyopathy , HCM is a disease process that must be expeditiously diagnosed and treated to prevent significant morbidity and mortality. HCM is the most common cause of sudden cardiac death and has led to the untimely death of many well-known athletes. Notable athletes who succumbed to HCM include Gaines Adams of the Chicago Bears, who died at age 26 years; Ryan Shay, a 28-year-old marathoner who died 5.5 miles into a race; and Marc-Vivin Foe, the brilliant Cameroon midfielder, who died at age 28 years during a semifinal soccer match. None of these athletes was diagnosed with HCM prior to their deaths.

HCM is a genetic disorder that leads to asymmetric thickening of the myocardium that can induce life-threatening arrhythmias. Whereas most forms of HCM are inherited, others are caused by sporadic mutations. The prevalence is thought to be as high as 1 in 500 people in the 23- to 35-year age group. Although myocardial hypertrophy usually occurs in the ventricular septum, hypertrophy can occur in various locations, which can lead to outflow obstruction, particularly during vigorous exercise or during states of hypotension or dehydration.

For persons with HCM, it is imperative that medical clearance for participation in athletics be withheld pending consultation with a cardiologist. Obtaining a thorough personal and family history is critical because symptoms and signs typically do not present until teenage years. Common symptoms and signs include chest pain (which may present in the post-exercise period), shortness of breath, arrhythmias or palpitations, syncope, dizziness, and sudden death. Unfortunately, 1% of patients with HCM present with sudden death. In a study of 158 sudden deaths in athletes between the ages of 12 and 40 years in a 10-year period, it was found that 90% of all sudden deaths occurred during or immediately after competition. Postmortem examinations and toxicologic data suggested that 134 of these deaths were related to cardiac pathology, of which 36% were the result of HCM. Physical examination in asymptomatic athletes who have occult HCM may be normal or may reveal a fourth heart sound and/or a left ventricular lift (nonspecific). In persons with a significant obstruction, a harsh crescendo-decrescendo systolic murmur may be heard that begins shortly after S1, is typically best auscultated at the apex and lower left sternal border, and may radiate to the axilla and base, yet not usually into the neck. As a result of increased obstruction, the murmur may increase with an assumption of an upright posture from a supine, sitting, or squatting position or after the Valsalva maneuver.

It is beyond the scope of this chapter to detail various diagnostic and therapeutic tools or to discuss the controversies of screening athletes for HCM. Pre-participation screening for HCM is an ardently debated subject, with conflicting recommendations from varying organizations. The American Heart Association has indicated that a thorough pre-participation history and physical examination may be adequate to detect underlying pathology in many cases and that more detailed testing (to improve sensitivity), including an electrocardiogram and transthoracic echocardiogram, be reserved for cases with features that raise concern on clinical examination. Conversely, in Italy, pre-participation screening for athletes includes a detailed patient and family history, physical examination, and electrocardiogram (with additional cardiac testing as needed). After institution of the mandated nationwide systematic screening program, the incidence of sudden cardiovascular death in young competitive athletes between 1979 and 2004 significantly decreased in the Veneto region of Italy. Therapeutic interventions included medications (β- or calcium channel blockers and antiarrhythmic agents), pacemakers and/or defibrillators, and/or invasive, surgical management (i.e., a myomectomy or ablation of the cardiac septum).

Orthopaedic Surgeries and Pain

A study of ambulatory surgeries showed that orthopedic patients have the highest incidence of postoperative pain. Inadequately treated pain can significantly affect recovery time, rehabilitation, patient satisfaction, and may increase readmission rates. When choosing the anesthetic, various factors should be considered, including the precise location of surgical intervention, extent of bone manipulation, instrumentation, osteotomies, ligamentous involvement, expected or planned nerve manipulation, use of bone or tendon autografts, size of incisions, the use of intraoperative tourniquets, and the requirements for postoperative physical therapy and range-of-motion (ROM) exercises. These perioperative factors will help the health care providers predict the level of postoperative pain, determine if a regional technique is indicated, and determine the needed duration of effect.

A peripheral nerve block (PNB) may provide excellent analgesia postoperatively, but may not be sufficient to cover the entire surgical field or for intraoperative retraction and manipulation. The necessary positioning for surgery can induce non-operative discomfort and can be a limiting factor in using a regional technique as the primary anesthetic. Pain induced by use of a tourniquet can be a source of substantial discomfort for a patient who is awake. Occlusion times more than 45 to 60 minutes may lead to break-through ischemic pain and may be intolerable despite the use of a PNB. Finally, certain surgical procedures put the patient at high risk for nerve injury or compartment syndrome and the surgeon may wish to identify this risk early in the postoperative course. In this setting, a regional technique may confound the postoperative examination for the first 24 hours or may mask a compartment syndrome.

Patient Characteristics

Several clinical features, including the aforementioned medical comorbidities, play an important role in shaping the anesthetic plan. In the younger athletic population, cardiovascular risk factors are fortunately rare, as GA is known to increase the risk of significant cardiac events in persons with certain cardiac risk factors. For persons with OSA, the use of non-narcotic means of analgesia and avoidance of GA is recommended to reduce the risk of perioperative complications. If a patient has a history of difficult intubation, it may be beneficial to avoid airway instrumentation to prevent potential airway complications. Patients with increased risk of aspiration as a result of preexisting esophageal or gastric pathology, or more commonly as a result of gastroesophageal reflux disease, may also benefit from the avoidance of GA. Patient psychological factors may play a prominent role in the anesthetic choice. Promising young athletes may fear a protracted nerve injury after undergoing a regional technique.

Regional Anesthesia

The term regional anesthesia implies analgesia and immobility of a region of the body. Regional anesthesia techniques may be further subdivided into those that target segmental spinal levels (i.e., central or neuraxial blocks such as spinal or epidural blocks), peripheral nerves (e.g., PNBs and plexus blocks), or extremities via IV regional block (i.e., Bier block). Neuraxial blocks and PNBs are achieved with the use of local anesthetic agents, narcotics, and other adjuvant medication. Field blocks typically describe the more superficial injection of local anesthetics. Both neuraxial nerve blocks and PNBs can be modified by the insertion of a catheter to continuously infuse medication during surgery, as well as for postoperative analgesia. Peripheral nerve catheters can be used in an inpatient or outpatient setting with proper patient selection and education. PNBs and neuraxial anesthetic agents may be used as the primary anesthetic or as an adjuvant to GA.

Contraindications to Regional Anesthesia

Absolute and relative contraindications to regional anesthesia typically vary by the type of planned intervention and the patient. Patient refusal, the inability to lie still during administration of a block, infection at the site of injection, recent use of thrombolytic agents, and operator inexperience for the proposed regional technique are perhaps the only shared absolute contraindications. Increased intracranial pressure may lead to brainstem herniation, which precludes use of neuraxial procedures. Other relative contraindications include evidence of systemic infection, preexisting neurologic disease, coagulopathy attributable to intrinsic disease or medication, or aberrant anatomy. All risks and benefits should be weighed thoroughly before proceeding with regional anesthesia.

Complications of Regional Anesthesia

The incidence of infection associated with neuraxial techniques is approximately 1 in 40,000. The risk of PNB infection has yet to be clearly defined, but appears to be greater with the use of continuous, indwelling catheters in the axillary or femoral areas for more than 48 hours. Skin contaminants either by colonization or local infection, systemic infection via seeding of catheter sites, or immune suppression enhance risk. Spinal hematomas may form after induction of spinal or epidural anesthesia in patients with underlying coagulopathy. Detailed recommendations for management are well described in the American Society of Regional Anesthesia 2010 Practice Advisory. Although the data are less instructive for PNBs, the literature includes rare case reports of a hematoma causing nerve injury, which seems to be more prevalent with use of deeper techniques such as lumbar plexus block. Nerve injuries are a major concern for both the orthopedic surgeon and anesthesiologist, yet the overall risk of peripheral nerve injury (PNI) is fortunately small. A meta-analysis in 2007 showed rates of permanent nerve injury between 0 and 7.6 per 10,000 for neuraxial procedures and approximately 1 in 15,000 for PNBs. Recent studies of PNI demonstrate long-term neurologic findings widely ranging from 0.029% to 0.2%, largely due to study methodology. Most commonly, the incidence of neurologic findings after PNB are quoted between 2 and 4/10,000. The incidence of short-term paresthesias or dysesthesias is thought to be much higher at 1% to 3%, with the highest incidence following interscalene brachial plexus blocks.

The American Society of Regional Anesthesia (ASRA) published a practice advisory in 2016 with a specific focus on neurologic injury following regional techniques. In addition to reviewing the incidence, causes, and risks for neurologic injury following regional techniques, the advisory also reviews risks of PNI after common orthopedic procedures and describes treatment algorithms following PNI.

Benefits of Regional Anesthesia in the Sports Medicine Patient

The benefits of regional anesthesia are abundant. Compared with narcotic analgesic agents, postoperative pain control is notably improved with peripheral nerve and neuraxial blocks. As expected, these studies also demonstrate less nausea, vomiting, ileus, pruritus, and sedation because of the opiate-sparing effects. It is also well established that the use of regional anesthesia improves functional recovery in select patients. Peripheral nerve catheters resulted in earlier ambulation, shorter hospital stays, and shorter rehabilitation periods after discharge, as well as improved ROM and mobilization after knee surgery. Epidural catheters also offer similar analgesic benefits when compared with peripheral nerve catheters, although hypotension and nausea are more common. In the ambulatory setting, orthopedic procedures can account for a significant percentage of unplanned readmissions for pain control. Use of outpatient perineural catheters resulted in fewer unplanned admissions after discharge in patients undergoing anterior cruciate ligament (ACL) surgery.

Regional anesthesia may also benefit patients in measures that transcend pain control and its associated secondary gains. Operative blood loss may be decreased through decreased arterial and venous pressure and blockade of sympathetic tone in the affected extremity. The incidence of deep venous thrombosis (DVT) and pulmonary embolism (PE) may be lower with neuraxial anesthesia because of increased blood flow, decreased viscosity, and modification of inflammatory mediators. Neuraxial anesthesia may also reduce the risk of infections at surgical sites, possibly through modulation of inflammation and immune responses. Furthermore, the avoidance of GA in high-risk patient populations is an immeasurable benefit.

Beach Chair Position

The beach chair position has become the chosen intraoperative position for many orthopedic surgeons who perform procedures on the shoulder. This position is favored for many reasons, including better exposure of the shoulder joint, avoidance of the lateral position, decreased risk for brachial plexus injuries, and reduced bleeding in the joint. Nonetheless, the beach chair position has multiple physiologic consequences, including a decrease in mean arterial blood pressure, central venous pressure, stroke volume, cardiac output, and arterial oxygen content. Additional concerns include venous pooling, increased risk for air embolus, and poor access to the airway. Reports of fluid extravasation from the shoulder joint into soft tissue have led to airway compromise.

An important concern is the discrepancy that can exist between cerebral perfusion and the site of blood pressure measurement. This issue is especially vital in the hypertensive patient who may have a rightward shift of the cerebral autoregulatory curve and needs higher mean arterial blood pressure to maintain adequate perfusion. Blood pressure should be measured in the arm at the brachial artery, and the distance between the heart and external auditory meatus should be calculated. The hydrostatic gradient can be determined using the conversion of 0.77 mm Hg decrease for every centimeter height difference between the brain and the site of blood pressure measurement. Additionally, placing a blood pressure cuff on the ankle (which could be as much as 150 cm below the brain) has been implicated in providing the anesthesiologist and surgeon with a false sense of increased cerebral perfusion pressures. Serious neurologic injury, presumably due to inadequate cerebral perfusion during beach chair positioning, has been documented in four patients.

Overview

Surgical anesthesia, immobility, and analgesia can be achieved with the precise deposition of local anesthetics and adjuvants near peripheral nerves. This can be accomplished by using surface landmarks, nerve stimulation, and ultrasound-guided techniques. The duration of the block may be manipulated by altering the type of local anesthetic or adjuvant or by placement of a perineural catheter. Localization of the nerves to be blocked may involve several techniques. Incorporating knowledge of the surface anatomy along with palpation of vessels and bony structures can help identify the location for blockade. PNBs were initially performed by provoking paresthesias in the desired nerve distribution with needle advancement. For nerve stimulation, an insulated needle is used to apply a low-level current at the tip, which can elicit a twitch in a corresponding muscle group supplied by a target nerve. Alternatively, “real-time” ultrasonography may be used to visualize the peripheral nerves and needle, which enables anesthesiologists to administer medications with great anatomic specificity. Thus far, no one technique has been shown to decrease neurologic complications. There is mounting evidence that ultrasound can decrease local anesthetic toxicity by allowing visualization of the spread of local anesthetics and also by decreasing the total amount of local anesthetic needed to provide an adequate block Ultrasound-guided blocks have numerous advantages, including a faster onset of action, improved quality, decreased volume of local anesthetic used, and a decrease in accidental vascular puncture rates.

Upper Extremity Innervation and the Brachial Plexus

The brachial plexus forms from the ventral rami of spinal nerves C5 to T1, with occasional contribution from C4 and T2. Fig. 29.2 shows the brachial plexus. The plexus exits between the anterior and middle scalene muscles of the neck, courses over the first rib and under the clavicle, surrounds the axillary artery, and divides into peripheral nerves that supply motor and sensory innervation to the upper extremity. A fascial sheath surrounds the plexus from the intervertebral foramina to the upper arm and can serve both to compartmentalize injected medication and provide a safe barrier to this approach. Several techniques can be used to block the brachial plexus, each of which differs in coverage of the plexus and adverse effect profiles. Fig. 29.2 demonstrates the different approaches used to block the brachial plexus.