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Potential Injuries Related to Anesthesia or There is the possibility of injury related to anesthesia, and, especially, anesthetic procedures. Patients should also be informed about these, since the general public may not realize that these risks exist.
Peripheral Nerve Injury Proper positioning during surgery is extremely important to prevent peripheral nerve injury. Causes of such injury include prolonged position-related nerve compression or stretching, prolonged elbow flexion, prolonged lithotomy position (greater than four hours), prolonged tourniquet use (greater than two hours), or hereditary neuropathy with tendency to develop pressure palsies. If a patient has pre-existing neuropathy, the site should be noted before surgery. In addition, cigarette smoking and co-morbidities such as diabetes mellitus, alcoholism, cancer, and vitamin deficiency can predispose a patient to peripheral nerve injury. Because an anesthetized patient is unaware and unable to feel how he or she is positioned, it's up to operating room staff to position limbs appropriately. Any position that would not be tolerated by a fully awake patient should not be allowed for an anesthetized patient. The following chart lists interventions for the nerves most at risk for injury.
Tourniquet use for a blood-free surgical field is often needed for orthopedic procedures. The tourniquet is inflated to at least 50 mmHg above the patient's systolic blood pressure, and the application time and pressure are recorded on the anesthesia record. The tourniquet should not remain inflated for more than two hours at a time. The anesthesiologist alerts the surgeon at the end of each hour. If the tourniquet is needed after two hours, it's deflated for about 15 minutes. To avoid peripheral nerve injury, it's crucial that the tourniquet cuff be placed to avoid compressing a nerve against bone. In addition to nerve injury, skin injury can occur after prolonged or excessive pressure during surgery, which can result in ischemia and ulceration. Skin over bony prominences is especially vulnerable. Pressure from the anesthesia mask can cause ischemia on the bridge of the nose, the outer third of the eyebrows (which don't grow back if hair loss occurs), and the buccal branch of the facial nerve, causing paralysis of the orbicularis oris muscle (around the eye). The corner of the mouth can become ulcerated from endotracheal tube pressure, and the ear can be damaged if forcibly folded between the patient's head and operating table for a prolonged time. In surgeries where prolonged neck flexion occurs, severe postoperative macroglossia (enlarged tongue) has been noted, and care must also be taken that the patient's fingers and toes do not get pinched in a mechanically moving operating table. Finally, any orthopedic frames used to support the patient during orthopedic procedures should also be well padded to prevent nerve and skin ischemia.
Oral/Airway Injury Airway management is a crucial part of anesthesia delivery; there are a variety of tubes and techniques available to accomplish this. Tracheal intubation is common for patients undergoing general anesthesia, although mask or laryngeal mask airway (LMA) anesthesia maintenance can be used for short procedures not requiring muscle relaxants (outpatient or orthopedic procedures). To determine the appropriate equipment and technique, the patient's airway should be evaluated before surgery. The patient's upper airway is classified based on the size of the tongue and the pharyngeal structures visible on mouth opening, according to the following chart.
Class I Airway
Oral and upper airway laceration and bruising can occur when physical force and/or multiple attempts are needed during a difficult intubation. Other complications after tracheal tube removal include laryngospasm, sore throat, laryngitis, laryngeal or subglottic edema, laryngeal ulceration, vocal cord paralysis, tracheitis, tracheal stenosis, and arytenoid cartilage dislocation.
Eye Injury The eyes are also susceptible to injury if operating room staff do not take precautions. Anesthetized patients' eyelids should be taped shut to avoid being scratched by overhanging equipment and surgical drapes. Head positioning is also important; in the prone position, pressure on the eyes from headrests can cause thrombosis of the central retinal artery, even
Pulmonary Aspiration General anesthesia depresses airway reflexes, thus aspiration of gastric contents is another complication of tracheal intubation, especially in the period immediately after tube removal. This is most likely in debilitated patients, or if the patient ingested food soon before surgery (as may happen with trauma requiring surgery). Other predisposing conditions include bowel obstruction, pregnancy, morbid obesity, diabetic gastroparesis, symptomatic hiatal hernia, and gastroesophageal reflux. Aspiration can result in bronchospasm, atelectasis, hypoxemia, tachypnea, tachycardia, and hypotension, depending on the amount and pH of gastric contents aspirated. Patients at increased risk for aspiration may be pre-medicated before surgery, when possible, with antacids, H2-receptor antagonists (ranitidine), and/or metoclopramide.
Maternal/Fetal/Newborn Complications Pregnant women undergoing surgery, either nonobstetric-related (for example, appendectomy) or for Cesarean section, are at increased risk for complications from general anesthesia. Aspiration and difficult airway control are especially prevalent during pregnancy. In addition, narcotics and benzodiazepines can result in fetal/newborn depression. If possible, elective maternal procedures should be postponed until six weeks after delivery, but if surgery must be performed during pregnancy, regional anesthesia is preferred, when possible, to minimize fetal exposure to anesthetic. An obstetrician should be consulted. Fetal monitoring can be used perioperatively after the 16th week of gestation, as well as a uterine tocodynamometer to identify preterm labor.
Intraoperative Awareness Intraoperative awareness ("waking up" during surgery) has received a lot of media attention in the last few years. The ASA defines intraoperative awareness as "a rare condition that occurs when surgical patients can recall their surroundings or an event—sometimes even pain—related to their surgery while they were under general anesthesia" (ASA & AANA, 2005). This includes before and after surgery, as well as during. Figures vary, but it's estimated that 1 to 2 per 1000 patients who receive general anesthesia experience awareness, and it occurs more often when neuromuscular blocking agents are used (Orser, Mazer, & Baker, 2008).
Brain-wave monitoring to detect the level of anesthesia during surgery can occasionally be useful. The BIS monitor (Bispectral Index) and the Patient State Analyzer (PSA) are examples of such monitors; the BIS is the most widely used. However, anesthesiology researchers say the value of brain-wave monitoring to prevent intraoperative awareness is uncertain, as there are reported cases of awareness despite BIS monitoring, thus the monitor appears to be less than 100% effective (Avidan, et al., 2008). It's cost prohibitive to use a brain-wave monitor on every surgical patient, and the ASA further states that no technology can replace the expertise of an anesthesia professional (ASA & AANA, 2005). Brain-wave monitoring to detect the level of anesthesia during surgery can occasionally be useful. The BIS monitor (Bispectral Index) and the Patient State Analyzer (PSA) are examples of such monitors; the BIS is the most widely used. However, anesthesiology researchers say the value of brain-wave monitoring to prevent intraoperative awareness is uncertain, as there are reported cases of awareness despite BIS monitoring, thus the monitor appears to be less than 100% effective (O'Connor, Daves, Tung, Cook, Thisted, & Apfelbaum, 2001). It's cost prohibitive to use a brain-wave monitor on every surgical patient, and the ASA further states that "no monitoring device can replace the judgment of a physician…" (ASA, 2004). Although rare, intraoperative awareness can be life-changing for a patient who experiences it; some are left with posttraumatic stress disorder. Patients who have experienced intraoperative awareness should be supported and encouraged to seek counseling, when necessary. Patients who are afraid they may experience awareness in an upcoming surgery should be referred to the anesthesiologist for a complete discussion of the risks specific to the pending procedure. Research studies on the causes and solutions for intraoperative awareness are ongoing.
Allergic Reaction/Anaphylaxis Allergic reactions during surgery primarily result from natural rubber latex or medications. Preoperative assessment of a patient's allergy history is imperative to prevent these avoidable complications. The ASA estimates that natural rubber latex is the cause of at least 10% of the anaphylactic reactions reported under anesthesia (ASA, 2005). Approximately 1-6% of the general population and 8-12% of health care workers are sensitized to latex. Many medical supplies contain natural rubber latex, and sterile latex gloves are often used in surgery. Repeated exposure heightens sensitivity, so patients who have undergone multiple surgeries are one of the groups at highest risk for an anaphylactic reaction. It's imperative that latex precautions be used for latex-sensitive patients, and that those patients be scheduled as the first case of the day to avoid latex contamination from prior surgeries. Medications are another cause of allergic reaction, although it's important to distinguish between true allergic reaction and unpleasant side effects. Skin pruritus with hives or flushing, facial or oral swelling, shortness of breath, wheezing, choking, and vascular collapse are signs of allergic reaction. Antibiotics are the most common medication allergens, especially penicillin, sulfa, and cephalosporin derivatives. Seafood and shellfish allergies can signal the potential for cross-reaction to intravenous contrast dyes and protamine (a heparin-reversal agent), and allergy to soybean oil and egg yolk can signal a potential cross-reaction with propofol (an induction agent). History of an adverse effect to halothane or succinylcholine in a patient or close relative could signify malignant hyperthermia.
The orthopedic surgeon has seen Mrs. Parks and agrees that she needs a hip arthroplasty. As promised, you sit down with Mrs. Parks and her family to discuss her fears about the surgery, as well as what you learned at the Risks of Anesthesia inservice. She's most afraid of waking up during surgery, and asks you what the chances are of it happening again. Directions: 1. You respond that intraoperative awareness occurs:
2. Mrs. Parks' daughter says that she recently learned about BIS monitors in a nursing class. She wants to know how useful they are in preventing intraoperative awareness. You respond:
3. Mrs. Parks asks if she has to have general anesthesia for her hip surgery, or if there is another option. You respond:
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Oral and upper airway injury can occur during the intubation process, particularly if the patient has a difficult airway. The most common and serious type of damage is dental trauma; it's estimated that one in every 4,500 patients undergoing upper airway intubation during anesthesia experiences dental injury that requires further treatment (Stoelting & Miller, 2006). Part of the pre-surgical anesthesia evaluation includes noting the patient's current state of dentition and any areas of poor dentition that are especially likely to cause problems. The best way to avoid dental trauma is to avoid using the teeth as a lever for the laryngoscope while intubating. If a tooth is dislodged, it must be recovered, and appropriate radiographs should be taken of the chest to make sure the tooth hasn't passed into the trachea or distal airways.
leading to permanent blindness. The chance of thrombosis is increased during anesthetic hypotension (accidental or deliberate), and the anesthesiologist should ensure that no external pressure is exerted on the eyes during the procedure.
Awareness can occur in high-risk trauma and cardiac surgeries, or during Cesarean section, when a patient can't tolerate a deep anesthetic. In such cases, the anesthesiologist may decide that the risk of awareness is worth saving the patient's life. Alternatively, awareness can occur by user error, such as administering neuromuscular blocking agents without appropriate levels of hypnotic, or using an empty anesthetic canister. 
