Chapter 11 Choice of Anesthetic Technique
1. What should be accomplished in the preoperative evaluation and visit by the anesthesiologist according to the standard adopted by the American Society of Anesthesiologists?
2. What are some important aspects that should be included in the preoperative medical evaluation of the surgical patient?
Anesthetic technique
3. What are the several anesthetic options available to the anesthesia provider?
4. Name some considerations that influence the choice of anesthetic technique.
5. What are some of the unpleasant side effects associated with anesthesia?
6. Describe some of the optimal conditions to be achieved with the ideal anesthetic technique.
7. What should be included in the discussion of informed consent for anesthesia by the anesthesiologist? Is it required that the anesthesiologist discuss with the patient all the remote risks of anesthesia, including death?
8. How is the induction of general anesthesia often achieved?
9. What is preoxygenation? What is its purpose?
10. What are some methods by which preoxygenation can be achieved?
11. What are some methods by which the proper placement of an endotracheal tube can be confirmed?
12. What is a rapid sequence induction?
13. Describe a rapid sequence induction.
14. When is a rapid sequence induction indicated?
15. Describe an inhalation induction of anesthesia.
16. When is an inhalation induction indicated?
17. What are some objectives during the maintenance of general anesthesia?
18. What are some advantages of nitrous oxide for general anesthesia? What are some advantages of volatile anesthetics for general anesthesia? Why are the two often administered in combination?
19. Why might neuromuscular blocking drugs be used intraoperatively?
20. What are some of the advantages of injected opioids for general anesthesia? What is a disadvantage of injected opioids for general anesthesia?
21. What are some regional anesthetic techniques?
22. What surgical procedures are regional anesthetics often administered for?
23. What are some advantages of spinal anesthesia when compared with epidural anesthesia?
24. What are some advantages of epidural anesthesia when compared with spinal anesthesia?
25. What are some of the conditions that may increase the risk associated with spinal or epidural anesthesia?
26. When is intravenous regional anesthesia or Bier block used?
27. What are some advantages of peripheral nerve blocks for surgical anesthesia?
28. What are some disadvantages of peripheral nerve blocks for surgical anesthesia?
29. What is monitored anesthesia care?
30. What are some anesthesiologist responsibilities during monitored anesthesia care?
31. What are some of the advantages of using monitored anesthesia care?
Answers*
1. According to the standard adopted by the American Society of Anesthesiologists, preoperatively the anesthesia provider is responsible for determining the medical status of the patient: obtaining and reviewing tests and consultations necessary for the conduct of anesthesia, developing a plan of anesthesia care, and reviewing with the patient or a responsible adult the proposed anesthesia care plan. (190)
2. Important aspects that should be included in the preoperative medical evaluation of the surgical patient include data gathering and the imparting of information to the patient. The anesthesiologist needs to gather information regarding the patient’s history and physical examination and current drug therapy regimen, as well as the ordering and interpretation of laboratory data. In turn, the anesthesia provider must present the patient and the patient’s family with information regarding the events of the day of surgery, preoperative instructions regarding medicines and fasting, the anesthetic, and the potential risks of anesthesia. In addition, informed consent for the procedure must be obtained. The overriding goal of the preoperative medical evaluation of the surgical patient is to decrease perioperative morbidity and mortality. (190-191, Table 14-1)
Anesthetic technique
3. Several anesthetic options are available to the anesthesia provider including (1) general anesthetic, (2) regional anesthetic, (3) peripheral nerve block, (4) monitored anesthetic care (MAC), or (5) a combination of techniques. (190)
4. Some considerations that influence the choice of anesthetic technique include the patient’s history of medical problems and diseases, site of surgery, body position of the patient during surgery, whether the surgery is elective or emergent, the likelihood of the aspiration of gastric contents, the age of the patient, and patient preference. (191, Table 14-1)
5. Some of the unpleasant side effects associated with anesthesia include nausea and vomiting, urinary retention, myalgia, pruritus, anxiety, and apprehension caused by the concern of being awake or aware of operating room sights, sounds, and smells during general anesthesia. (191)
6. Ideally, the anesthetic technique would achieve optimal patient safety and satisfaction, provide excellent surgical conditions (e.g., relaxation) for the surgeon, allow rapid recovery, and avoid postoperative side effects. In addition, the anesthetic should be economical, allow early transfer or discharge from the postanesthesia care unit, provide optimal postoperative pain control, and permit optimal operating room efficiency including turnover times. (191)
7. The discussion of informed consent for anesthesia should include a discussion of the planned method of anesthesia and specific potential complications relative to the patient, anesthetic technique, and the surgical case. Informed consent does not require that the anesthesia provider discuss with the patient all the remote risks of anesthesia. The patient or responsible adult should sign an informed consent statement before surgery. The anesthesiologist should document that the patient understands and accepts the anesthetic plan as well as the accompanying risks. (191)
8. The induction of general anesthesia is often achieved with the administration of an intravenous anesthetic, typically thiopental, propofol, or etomidate. These drugs are all beneficial in that they rapidly produce unconsciousness. Then, ventilation can be sustained via a face mask or a laryngeal mask airway (LMA). A neuromuscular blocking drug may be given intravenously to facilitate direct laryngoscopy before tracheal intubation. (191)
9. Preoxygenation is the replacement of nitrogen with oxygen (denitrogenation) in the patient’s functional residual capacity before the induction of general anesthesia. The purpose of preoxygenation is to increase the time period the patient can safely be apneic. Preoxygenation prolongs the time to oxygen desaturation with the apnea that accompanies the induction of anesthesia. (192)
10. There are a few methods by which preoxygenation can be achieved. The patient can take eight vital capacity breaths of 100% oxygen over a period of 1 minute, or the patient can breathe 100% oxygen for 3 minutes at normal tidal volumes. Another method, which is somewhat less efficacious but faster, is to have the patient breathe four vital capacity breaths of 100% oxygen over a 30-second period. (192)
11. Some methods by which the proper placement of an endotracheal tube can be confirmed include the observation of upper chest expansion and reservoir bag collapse with inspiration, refilling of the reservoir bag with exhalation, cyclic waveforms on end-tidal carbon dioxide tracings that cycle from 0 to more than 20 mm Hg with inhalation and exhalation respectively, continuous pulse oximeter readings above 95%, and bilateral breath sounds. Confirmation of endotracheal tube placement can also be achieved by fiber-optic bronchoscopy. (192, Table 14-2)
12. A rapid sequence induction of anesthesia is the intravenous injection of an anesthetic to produce unconsciousness followed immediately by a neuromuscular blocking drug that produces a rapid onset of skeletal muscle paralysis (succinylcholine, rocuronium). (191)
13. A rapid sequence induction of anesthesia should be preceded with preparations such as the placement of routine monitors, confirmation of a functioning suction catheter, positioning the patient in an advantageous position to achieve intubation of the trachea by direct laryngoscopy, premedication with an antacid to neutralize the acidity of gastric contents, preoxygenation, and cricoid pressure. An induction dose of intravenously administered anesthetic, typically thiopental or propofol, followed by a dose of 1 to 2 mg/kg succinylcholine are then administered together in rapid sequence. After approximately 30 seconds, which corresponds to the onset of muscle relaxation, direct laryngoscopy should be instituted with the laryngoscope blade of choice. Only after successful intubation of the trachea has been confirmed by at least two methods should cricoid pressure be released. Alternatives to succinylcholine for neuromuscular blockade for a rapid sequence induction include rocuronium at two to three times ED95. (192)
14. A rapid sequence induction of anesthesia is indicated when patients are at an increased risk of the aspiration of gastric contents with the loss of protective laryngeal reflexes. The patients at an increased risk of the aspiration of gastric contents include those: with neurologic compromise, in cardiopulmonary arrest, with ascites, a hiatal hernia, or history of gastroesophageal reflux, with a history of gastroparesis, with an obstructed bowel, undergoing emergency surgery, or patients that are obese, pregnant, or intoxicated. (192)
15. An inhalation induction of anesthesia allows the patient to spontaneously breathe sevoflurane, possibly in conjunction with nitrous oxide via a face mask. Nitrous oxide mixed with sevoflurane has not been shown to improve the inhalation induction of anesthesia with sevoflurane, however. Sevoflurane is chosen most often because of its lack of pungency. In some cases, the prior administration of a premedicant drug may be indicated. The technique for the inhalation induction of anesthesia with sevoflurane is by priming the circuit, dialing the concentration of sevoflurane to 8%, administering high fresh gas flow of at least 8 L/min, and having the patient breathe deeply. The induction of anesthesia is usually achieved within 1 minute using this technique. Care should be taken to dial back down the sevoflurane concentration administered to avoid excessive anesthetic doses. This can be followed by placement of a laryngeal mask airway or endotracheal intubation facilitated by a neuromuscular blocking drug. Desflurane is not suitable for an inhalation induction due to its pungency and airway irritant effects. (192)
16. An inhalation induction of anesthesia is frequently used in pediatric patients in whom intravenous access is difficult to achieve while awake. Another benefit of an inhalation induction is the maintenance of the capacity to breathe spontaneously, which may avoid the need for paralysis and controlled ventilation. (192)
17. Objectives during the maintenance of general anesthesia are to maintain amnesia, analgesia, and skeletal muscle relaxation and to control sympathetic nervous system responses evoked by noxious simulation. These objectives are often achieved by combining drugs to optimize their effects. (193)
18. Advantages of nitrous oxide for general anesthesia include its relative lack of significant cardiovascular effects and its low blood gas solubility. Advantages of volatile anesthetics for general anesthesia include their high potency, their ability to attenuate sympathetic nervous system responses, and their ease of administration. Nitrous oxide and volatile anesthetics are often administered in combination to decrease the concentration of the volatile anesthetic necessary for a given anesthetic effect. Administration of nitrous oxide decreases the cardiovascular depression that may result from the administration of higher concentrations of volatile anesthetics alone. (193)
19. Neuromuscular blocking drugs are used intraoperatively to ensure lack of patient movement during certain operative procedures, as in neurosurgery. With the administration of neuromuscular blocking drugs during general anesthesia there is the inherent risk of paralysis with an inadequate depth of anesthesia and resultant patient awareness. Therefore, neuromuscular blockade must be accompanied with adequate levels of anesthesia. (193)
20. Advantages of injected opioids during general anesthesia are the increase in depth of anesthesia, and analgesia without added cardiovascular depression. A disadvantage of injected opioids when compared with inhaled anesthetics for general anesthesia is the inability to easily titrate opioids intraoperatively. (193)
21. Regional anesthetic techniques include spinal, epidural, and caudal anesthetics. (193-194)
22. Regional anesthetics are often administered for procedures involving the lower abdomen or lower extremities. (194)
23. Some advantages of spinal anesthesia when compared with epidural anesthesia are (1) it takes less time to perform, (2) it produces a more rapid onset and better quality sensory and motor anesthesia, and (3) it is associated with less pain during surgery. (194)
24. Some advantages of epidural anesthesia when compared with spinal anesthesia are (1) a lower risk for postdural puncture headache, (2) less systemic hypotension than with a spinal anesthetic if epinephrine is not added to the local anesthetic solution, (3) the ability to prolong or extend the anesthesia through an indwelling epidural catheter, and (4) the option of using the epidural catheter to provide postoperative analgesia. (194)
25. Certain preexisting conditions increase the relative risk of spinal or epidural anesthesia and the anesthesia provider must balance the perceived benefits of this technique. These conditions include hypovolemia, increased intracranial pressure, coagulopathy (thrombocytopenia), sepsis, infection at the cutaneous puncture site, and preexisting neurologic disease (e.g., multiple sclerosis). (194, Table 14-3)
26. Intravenous regional anesthesia is used for procedures lasting between 20 and 90 minutes. It provides reliable anesthesia for both the upper and lower extremities and is more cost effective than general anesthesia or brachial plexus block for outpatient hand surgery. (194)
27. Peripheral nerve blocks for surgical anesthesia provide the advantage of an isolated anesthetic effect without manipulation of the airway or prolonged systemic effects. They typically do not cause any cardiopulmonary impairment, nor are protective airway reflexes compromised. (194)
28. One disadvantage of peripheral nerve blocks for anesthesia is the unpredictability of the adequacy of the block for surgery. Other disadvantages of peripheral nerve blocks are related to the potential complications of the peripheral nerve block itself, such as nerve injury and systemic local anesthetic toxicity. (194)
29. Monitored anesthesia care describes when an anesthetic provider is requested or required to provide anesthetic during a procedure. This can include the preoperative evaluation, anesthetic care during the procedure, and management after the procedure. General anesthesia is not given in these cases. (194-195)
30. Some anesthesiologist responsibilities during monitored anesthesia care include the diagnosis and treatment of clinical problems during the procedure, the support of vital functions, the administrations of medicines as necessary for sedation, analgesia, or hemodynamic support, psychological support and physical comfort, and the provision of other services necessary to facilitate the safe completion of the procedure. (194-195)
31. Monitored anesthesia care may facilitate the avoidance of side effects of general or regional anesthesia (sympatholysis, respiratory depression, delayed emergence) and may be particularly cost effective in comparison to general or regional anesthetics in the ambulatory care setting. (195)
Preparation for anesthesia
32. An advantage to having a separate room from the operating room for the induction of anesthesia is that peripheral nerve blocks or epidural catheter placement can be achieved before the operating room is available. The distinct disadvantage to having an induction room is that the practice of moving anesthetized patients may be unsafe. (195)
33. Regardless of the anesthetic technique, there are some routine preparations the anesthesiologist should make before anesthetizing a patient. These include evaluation of the anesthesia machine and monitors, and confirmation of the availability of emergency drugs, anesthetic drugs, and equipment that might be necessary for controlled ventilation or the emergent intubation of the trachea. (195, Table 14-4)
Pharmaco-economics
34. Cost containment in the operating room may lead to recommendations for low cost drugs; for example, antiemetics, intravenous drugs to induce anesthesia, volatile anesthetics, and neuromuscular blocking drugs. In addition, a useful method to decrease the cost of volatile anesthetics is the use of low fresh gas flow (2 L/min) during the maintenance of anesthesia. (196)
