4 Regional versus General Anesthesia for Fractures of the Proximal Femur
Anesthesia is commonly classified into two main techniques: general anesthesia, in which inhalational agents or intravenous drugs produce central nervous system depression; and regional anesthesia, in which drugs are administered directly to the spinal cord or nerves to block afferent and efferent nerve input locally.1 The selection of one of these techniques for the repair of fractures of the proximal femur depends on certain factors, including the patient’s comorbidities, the overall requirements of the surgical procedure, and the postoperative analgesic requirements.
Anesthesia for proximal femur fracture repair presents a challenge because patients are typically elderly and may have significant comorbid conditions, such as ischemic heart disease, hypertension, renal dysfunction, chronic obstructive pulmonary disease (COPD), diabetes, and obesity, all of which can adversely affect patient management in the perioperative period. It is therefore important to choose an effective anesthetic technique that the patient will tolerate with minimal side effects. The anesthetic technique must also allow optimal functional recovery and decrease postoperative morbidity and mortality. Despite the large number of proximal femur fracture repairs performed, an evidence-based international consensus on anesthetic technique does not exist. Anesthetic management tends to be influenced at an institutional level by factors such as local experience and skills.
General anesthesia involves rendering a patient unconscious by using intravenous medications, inhalational agents, or a combination. For general anesthesia to be safe and adequate, the anesthesiologist must address the combined needs for unconsciousness, analgesia, and muscle relaxation in the patient to provide the best operative conditions for the surgeon.
Administering a general anesthetic regimen encompasses several stages, including preoperative preparation, premedication, induction, maintenance, extubation, postoperative care, and postoperative pain management.
Ideally, preparation for anesthesia should be preformed well in advance of the surgery date. Preoperative preparation involves obtaining a targeted history, performing a focused physical examination, ordering and reviewing investigations, and optimizing the patient for surgery. The anesthesiologist will look for specific factors that may cause a patient to be a better candidate for general or neuraxial anesthesia.
The targeted anesthetic history includes the history of presenting illness, medications, allergies, previous anesthetics, family history of malignant hyperthermia, and past medical history. Important comorbidities that may affect candidacy for surgery and choice of anesthesia are sought, including the presence of cardiac dysfunction (coronary artery disease, valvulopathy), respiratory illness (COPD, asthma), bleeding diathesis (von Willebrand’s disease, hemophilia), diabetes, and acid reflux.
The focused physical examination includes an airway examination that will determine the patient’s ease of intubation, identification and inspection of potential regional landmarks for neuraxial techniques, and a cardiorespiratory assessment. Laboratory investigations may include an electrocardiogram, a complete blood count, electrolyte determinations, coagulation studies, or other more involved studies, depending on the disorders elicited during the history and physical examination.
Preoperative optimization may be required if the patient is taking anticoagulant medication, insulin, or oral hypoglycemic agents or has poorly controlled comorbidities. For example, a patient with poorly controlled COPD may need a course of antibiotics, corticosteroids, bronchodilators, and a respirology assessment before general anesthesia can be considered. Optimization may also include stopping anticoagulants, reversing an elevated international normalized ratio (INR), discontinuation of oral hypoglycemic agents the evening before the surgical procedure, initiating antihypertensive medications, and obtaining consultations from other services or specialists to help with comorbidity management or simply to obtain a risk assessment. For fractures of the proximal femur, the Royal College of Physicians’ guidelines recommend surgical repair within 24 hours after hospital admission; however, the effect of operative delay on mortality remains controversial. According to one study, operative delay beyond 48 hours after admission may increase the odds of 30-day all-cause mortality by 41% and of 1-year all-cause mortality by 32%.2
The first phase of administering general anesthesia starts with premedication, which can include anxiolytics, antibiotics, bronchodilators, antisialagogues, and antireflux medications. Induction is one of the most important stages of anesthesia because the patient transitions from the awake to the unconscious state. Induction of anesthesia can be achieved with intravenous medications or inhalational agents. Medications given intravenously include the following: benzodiazepines, which reduce anxiety and cause amnesia; opioids, which are used for both analgesia and suppression of the sympathetic response to intubation; the induction agent (propofol, thiopental); and the muscle relaxant, which relaxes the oropharyngeal muscles to allow the passage of an endotracheal tube (ETT) through the vocal cords. The specific combination of these drugs depends on the patient’s characteristics and the anesthesiologist’s preference. The dose of medication may be precalculated based on weight or titrated to effect. Muscle relaxation given during induction or repeated doses of muscle relaxants given throughout the operation may provide optimal operating conditions; however, caution is exercised with muscle relaxation near the end of a procedure because it may prolong extubation time.
Rendering a patient unconscious requires airway protection in the form of an ETT or a laryngeal mask airway (LMA) because induction of anesthesia results in the loss of protective airway reflexes. The ETT or LMA allows the delivery of oxygen and inhalational agents for maintenance of anesthesia. Maintenance can usually be achieved with inhalational agents, continuous intravenous infusions, or a combination. Analgesic medications can be given in the form of long-acting opioids, frequent doses of shorter-acting opioids, or continuous infusions.
Once the surgical procedure is complete, muscle relaxants are generally reversed, and inhalational agents or intravenous anesthestics are discontinued. Most nondepolarizing muscle relaxants can be reversed only if they have already begun to wear off. Only when patients are breathing spontaneously, maintaining adequate respiratory parameters, obeying commands, and displaying adequate strength to maintain airway reflexes should they be extubated. Patients are then usually monitored for a brief period in the postanesthesia care unit after the surgical procedure. Patients must meet certain institutional criteria before they are discharged to the ward or home. Certain patients, such as those with sleep apnea or a personal history of malignant hyperthermia, may require a prolonged hospital stay to monitor for respiratory depression or a malignant hyperthermia crisis, respectively. Patients who do not meet criteria for extubation or those with significant comorbidities that put them at higher risk for postoperative morbidity and mortality may require postoperative monitoring in a more intensive setting. After receiving general anesthesia, patients may be given a patient-controlled analgesia (PCA) pump, in which a preset amount of narcotic is given by the intravenous route at set intervals on demand.
The patient’s preference is a reasonable indication for general anesthesia unless comorbid conditions preclude the delivery of a safe anesthetic regimen. General anesthesia is considered safer than neuraxial anesthesia in patients with fixed cardiac output states such as aortic stenosis. General anesthesia is also considered prudent in patients with massive hemorrhage or hemodynamic instability and is safer than regional anesthesia in coagulopathic patients or those who have had a recent intake of low-molecular-weight heparin (LMWH).
No single contraindication to general anesthesia exists. Certain patients may be at higher risk for not tolerating intubation and ventilation (i.e., severe COPD), whereas others may not tolerate the hemodynamic changes induced by anesthetic agents. Death secondary to anesthesia alone occurs in less than 1 in 10,000 patients (average figures incorporating both elective and emergency patients and including all comorbidities).3 Postoperative nausea and vomiting, drowsiness, and sore throat occur at rates of 5%, 15%, and 25%, respectively.3