Anesthesia and Regional Blockade Techniques for the Direct Anterior Approach

Jinlei Li

Ramya Krishnan

Adriana D. Oprea

Edward R. Mariano

Introduction

Anesthesia and analgesia are essential parts of the DAA to total hip arthroplasty (THA) that impact the perioperative course, recovery process, and surgical outcome. An institution-wide protocol, including a comprehensive and practical anesthesia and analgesia plan, is desirable for consistent care delivery and quality assurance. This standardized protocol should also allow for individualization of care based on each patient’s medical comorbidities and social support system. The details of the anesthetic plan should include a discussion between the anesthesiologist, surgeon, perioperative care team, patient, and family member, with a shared goal to ensure patient safety and satisfaction, provide high-quality care, and expedite recovery. This chapter focuses on the three critical aspects of anesthesia and analgesia care for DAA THAs: (1) preoperative evaluation and enhanced preoperative care, (2) various modalities of intraoperative anesthesia, and (3) postoperative analgesia and peripheral nerve blocks to facilitate discharge.

Preoperative Evaluation and Optimization

The goal of the preoperative evaluation is to optimize patients for the upcoming surgical and anesthetic care while also planning for expedited recovery. The preoperative optimization of a patient undergoing THA is no different from that for any other surgery and should involve a basic medical history and a focused physical examination. When performing a medical history, one has to fully clarify patient comorbidities that will affect perioperative management. A thorough assessment of a patient’s cardiovascular, pulmonary, and neurologic status, among other organ systems, should be conducted to ensure that patients who are at high risk for perioperative complications are appropriately managed.

For patients undergoing elective procedures, such as THA, the presence of any active cardiac conditions such as acute coronary syndrome (unstable angina or acute myocardial infarction), decompensated congestive heart failure or valvular disease, and uncontrolled arrhythmias should lead to the cancellation of surgery until the medical condition is addressed.¹ Otherwise, a combined medical and surgical risk of major adverse cardiac events (MACEs) should be assessed to determine whether further cardiac workup is needed before the procedure. The American College of Surgeons National Surgical Quality Improvement Program calculator is the optimal tool for quantifying the risk of MACEs, but the Revised Cardiac Risk Index in conjunction with the surgical risk can be used. Patients with calculated rates of MACEs > 1% are deemed to be at high risk, and further workup is recommended by the 2014 American College of Cardiology/American Heart Association Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery for patients with poor functional status (<4 metabolic equivalents) if the results of the test have the potential of changing current management. Unfortunately, functional capacity, which is measured in metabolic equivalents, can be difficult to obtain in patients with existing hip pathology, and the approach should be a conservative one.¹

Pulmonary capacity is equally important to elucidate before elective THA. Poor preoperative pulmonary health places patients at high risk for postoperative pulmonary complications, including atelectasis, pneumonia, exacerbation of chronic lung disease, and respiratory failure requiring prolonged mechanical ventilation. A recent retrospective analysis by Malcolm et al² demonstrated that 1.42% of primary THA procedures were complicated by perioperative pulmonary complications, which were associated with an increase in length of stay, hospital costs, and mortality. Patient factors that influence the incidence of postoperative pulmonary complications include obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), smoking history and recent cigarette use, higher American Society of Anesthesiologists (ASA) class, decreased functional status, and age.³ In 2006, the American College of Physicians recommended that preoperative spirometry and thoracic imaging not be used routinely to predict the risk of postoperative pulmonary complications for nonthoracic surgeries.⁴

An additional factor to consider when assessing a patient preoperatively is their risk of developing postoperative delirium, which can result in a prolonged length of stay and increased hospital costs. The prevalence of cognitive impairment in the absence of dementia is
demonstrated to be around 22% in patients older than 71 years of age.⁵ A retrospective review of the current literature demonstrated that preoperative cognitive impairment predisposes patients undergoing elective primary THA to longer hospital stays and discharge to a health care facility rather than home.⁶ There was also a significant correlation between preoperative cognitive impairment and the development of delirium postoperatively.⁶ The detection of the degree of cognitive impairment preoperatively is not performed routinely in clinical practice, particularly if the patient does not have an existing diagnosis. The 3-minute Mini-Cog assessment is a validated tool that can be used in the preoperative setting to assess preoperative cognitive function and is clinically feasible to use.⁷

Additional comorbidities that influence perioperative care include any condition that requires prolonged anticoagulation. In preparation for upcoming surgery, patients should receive appropriate instructions on the duration of interruption of the oral anticoagulation and/or the use of bridging regimens if indicated. This decision should involve collaboration between the medical practitioner prescribing the anticoagulation, the surgeon, and the anesthetic team. Restarting anticoagulation postoperatively could impact pain control options as described later in this chapter.

Hemoglobin A1c is a commonly used indicator for diabetes mellitus control for the immediately preceding 3 months, but there is no consensus on the threshold in predicting adverse outcomes in THA. A multicenter study of total knee arthroplasty (TKA) and THA showed hemoglobin A1C above 7.7%, in contrast to the previously identified threshold of 7%,⁸ is associated with an increase in the periprosthetic joint infection rate from 0.8% to 5.4%.⁹

Finally, patients should be informed of appropriate nil per os guidelines for their procedure. Individualized nil per os instructions take into account the potential for difficult airway management, the presence of gastroesophageal reflux disease, dysphagia symptoms, and other gastrointestinal motility issues (such as poorly controlled diabetes mellitus), which would increase the patient’s risk for perioperative aspiration. In patients at low risk for aspiration, the ASA practice guidelines allow for clear liquids to be ingested for up to 2 hours before the procedure, with additional fasting time if the patient has consumed a meal (6 hours for light meals and 8 hours for heavy meals).¹⁰ Preoperative carbohydrate administration may be considered in accordance with fasting guidelines, but there is no strong evidence to support its routine use.¹¹

Intraoperative Anesthesia Care

The type of anesthetic chosen for THA is linked to perioperative efficiency and surgical outcomes. There are several high-quality studies that detail the benefits and pitfalls of commonly used anesthetic options. It is important for the perioperative team to establish protocols as well as practice flexibility between anesthetic options. This section details two commonly used approaches to anesthetic care: spinal anesthesia (SA) with sedation and general anesthesia (GA).

Spinal Anesthesia

SA involves the injection of a spinal dose of local anesthetic of desired duration of action with or without pain-relieving adjuncts into the intrathecal space to produce a dense sensory and motor blockade within minutes. Contraindications to SA include patient refusal, systemic injection or local infection at the site of injection, uncorrected hypovolemia, allergy to any substance used in the spinal, and increased intracranial pressure. Relative contraindications include coagulopathy, severe aortic stenosis, and neurologic diseases with existing deficits. The procedure is typically performed at the level of L1-L2, L2-L3, or L3-L4 under sterile conditions before the start of the surgery with the patient either in the sitting or the lateral position. The recent adoption of ultrasound guidance and visualization of spine sonoanatomy has made SA easier or possible for patients with prior spine surgery, scoliosis, or challenging body habitus. Hyperbaric bupivacaine is the only Food and Drug Administration (FDA)-approved spinal local anesthetic formulation with a duration of action suitable for the majority of THA surgeries.

With the implementation of enhanced recovery after surgery (ERAS) pathways and ambulatory THA, there has also been interest in finding alternative local anesthetics that allow for adequate surgical analgesia but facilitate faster recovery and earlier rehabilitation. Off-label use of ropivacaine has resulted in similar fast onset, shorter duration of sensory and motor block,¹² and improved time to independent mobilization.¹³ Ropivacaine was also shown to have a lower incidence of hypotension compared with bupivacaine.¹⁴ Compared with bupivacaine, mepivacaine used off-label for SA results in a faster return to sensory and motor function and discharge readiness, a reduced incidence of urinary retention, no difference in postoperative opioid consumption, and a higher incidence of self-limiting transient neurologic syndrome.¹⁵

Even though there is promising evidence for both ropivacaine and mepivacaine, the use of these medications in SA at the time of writing this chapter. 2-Chloroprocaine, recently FDA-approved for SA, has been used in procedures of 30- to 60-minute duration and is associated with earlier ambulation and discharge compared with bupivacaine.¹⁶ There are conflicting data regarding intrathecal morphine in total joint arthroplasty. The decreases in postoperative pain scores and opioid consumption¹⁷ need to be weighed against its effect on respiratory status, postoperative nausea and vomiting (PONV), sedation, and
urinary retention. Slappendel et al¹⁸ performed a dosage optimization study and found that 0.1 mg intrathecal morphine was associated with adequate postoperative pain relief while minimizing side effects. Patients undergoing SA can be additionally sedated using adjunct medications such as midazolam, fentanyl, propofol, dexmedetomidine, and ketamine, and each can be titrated to patient comfort.

Compared with GA, SA is associated with a decreased incidence of major and minor adverse events; these include decreased mortality¹¹ and a decreased incidence of venous thromboembolism, blood loss, and transfusion requirements.¹⁹^,²⁰ Moreover, lower rates of infection,²¹ pulmonary complications such as pneumonia and aspiration, unplanned intubations and need for postoperative ventilator use, stroke, and cardiac arrest,²² as well as a decreased incidence of postoperative falls, have been noted. Many of these associated benefits persist even when GA and SA are used in combination compared with GA alone.¹¹

SA was also shown to decrease the rate of nausea and vomiting compared with GA.²³ In addition, the use of spinal anesthetic has been linked to improved surgical outcomes with decreased operative time²² and postoperative recovery room time, a modestly decreased length of hospital stay,²⁴ and lower hospital costs.²⁵ Potential adverse events include risks of a failed spinal, post-dural puncture headache, urinary retention, infection, hematoma, development of chronic neurologic changes, and total SA resulting in cardiovascular collapse. Based on the previously mentioned benefits, a multinational expert group reached an evidence-based consensus on the optimal anesthetic for THA, stating that neuraxial anesthesia is strongly recommended for primary unilateral THA when there is no significant contraindication to preclude its use.²⁶

General Anesthesia

GA is always an option for DHA TAA, particularly when SA is contraindicated or as the backup anesthetic for failed SA. GA involves rendering the patient unconscious and is typically associated with the placement of an airway device to support respiratory function. This can be in the form of either an endotracheal (ET) tube or a laryngeal mask airway. An ET tube is often used when a deeper anesthetic level or muscle relaxation is required to prevent a sympathetic surge during surgery or surgical exposure. This may occur when pain control is difficult, in a patient with significant chronic pain, for example, or when high-dose opioids are used and suppress the patient’s own respiratory drive. The use of an ET tube may be associated with the risk of postoperative pulmonary complications and prolonged postoperative ventilation.

For DAA THA, a laryngeal mask airway can be used when the anesthetic level required still maintains a patient’s spontaneous unassisted ventilation, which tends to occur when adjunctive peripheral nerve blocks are used or GA and SA are combined. A study by Stambough et al¹⁹ described an enhanced recovery protocol using GA at a high-output total joint arthroplasty center. This protocol used standard optimization of patient risk factors, newer techniques in short-acting muscle relaxants (eg, rocuronium) and reversal agents (eg, sugammadex), periarticular injection, short-acting opioids intraoperatively, and a pre- and postoperative physical therapy regimen with the goal of discharge on postoperative day 1. The length of stay was 1.09 ± 0.82 days for THA, and 96% of patients could partake in same-day physical therapy.¹⁹ In a large retrospective study on hip arthroplasty patients, the use of GA did not increase the length of stay or medical and surgical complications.²⁷

In summary, for THA, SA is the intraoperative anesthetic technique of choice when used alone or in combination with GA. However, there are ways of promoting ERAS principles if, for any reason, GA alone is chosen. As with the majority of surgical interventions, preincisional antibiotic prophylaxis is required for infection prevention.²⁸ Lastly, THA has a higher transfusion risk than TKA²⁹; therefore, tranexamic acid (TXA) use has now become standard practice. Whether administered intravenously, orally, and/or via local/topical application, TXA use is associated with decreased blood loss and transfusion requirements and minimal adverse events in THA.³⁰

Postoperative Analgesia Care

Postoperative pain after THA results from a combination of mechanical trauma, inflammation, and neuropathic pain. “Multimodal analgesia” has been an evolving concept that uses the synergistic effects of different groups of analgesics targeting distinct parts of the pain pathway, from nociception to pain perception, and aiming to improve perioperative pain management and minimize side effects from opioids.

Opioid-Sparing Analgesics

Acetaminophen’s mechanism of action is not completely known, but it likely functions to relieve pain through many pathways,³¹ resulting in reduced pain scores and opioid consumption.³² Other than end-stage hepatic dysfunction, it has few real contraindications. In general, there is no clear advantage of intravenous over oral acetaminophen in patients with a functioning gastrointestinal system, and the intravenous formulation is significantly more expensive.³³ It is typically used around the clock, and the combination of acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) can achieve superior analgesia compared with either drug alone. NSAIDs reduce pain by decreasing cyclooxygenase production and reducing inflammation. Cyclooxygenase-2 inhibitors
selectively inhibit the cyclooxygenase-2 enzyme. Unlike other NSAIDs, they do not influence other enzyme pathways and, therefore, do not increase the risk of gastric bleeding or ulceration.

Gabapentinoids (gabapentin and pregabalin) affect alpha-2-delta calcium channels in the spinal cord and brain, which result in improvement in neuropathic pain. There are conflicting data on the use of gabapentinoids for reducing postoperative pain. Additionally, gabapentinoids are known to cause sedation, confusion, and dizziness, which may be counterproductive to postoperative rehabilitation. Glucocorticoids exert analgesic effects along several levels of the pain pathway, most importantly via anti-inflammatory effects and neuroprotective properties.³⁴ In addition, the antinausea and antifatigue effects of glucocorticoids have proven beneficial post THA.³⁵ Evidence supporting the safety and efficacy of glucocorticoids in TKA is much more robust than in THA; nonetheless, it seems the concerns for infection and poor wound healing are not warranted.³⁶^,³⁷^,³⁸

Regional Anesthesia Techniques for Postoperative Pain Management

Historically, peripheral nerve blocks have been less commonly used for hip surgery than other lower extremity orthopaedic procedures given the complex innervation of the hip by both the lumbar and sacral nerve root plexuses (Figure 43.1). However, recent research has demonstrated the efficacy of several peripheral nerve block techniques when used as part of multimodal analgesia. A review of 18 randomized clinical trials demonstrated that, compared with systemic analgesia, regional analgesia reduced postoperative pain and opioid consumption without reducing the ability to partake in rehabilitation or increasing length of stay.³⁹ This section discusses the options for regional anesthesia in the THA patient starting from neuraxial to the most peripheral nerve blocks.

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