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E47MULTISYSTEM RADIOLOGY
Thea C. Moran, MD • Alan D. Kaye, MD, PhD • Andrew H. Mai, MD Leonard R. Bok, MD, MBA, JD
Sedation, Analgesia, and Local Anesthesia: A Review for General and Interventional Radiologists1
Abbreviations: ASA = American Society of Anesthesiologists, IV = intravenous, LAST = local anesthetic systemic toxicity, NSAID = nonsteroidal anti-inflammatory drug, PCA = patient-controlled analgesia
RadioGraphics 2013; 33:E47–E60 • Published online 10.1148/rg.332125012 • Content Codes: 1From the Departments of Radiology and Anesthesia, LSU School of Medicine, 1542 Tulane Ave, 3rd Floor, New Orleans, LA 70112. Presented as an education exhibit at the 2011 RSNA Annual Meeting. Received February 13, 2012; revision requested April 3 and received August 22; final version accepted December 21. For this journal-based SA-CME activity, the authors, editor, and reviewers have no relevant relationships to disclose. Address correspondence to T.C.M. (e-mail: [email protected]).
■ Discuss the Joint Commission requirements for sedation providers and typical hospital policy components with respect to pa-tient care.
■ Identify circum-stances in which anesthesia consul-tations are most useful.
■ List the different classes of sedatives, analgesics, and anesthetics and identify in what cir-cumstances they are most applicable to the radiologist.
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IntroductionManaging patient discomfort has always been important, but it has become especially important for physicians, given the current licensure, creden-tialing, and legal consequences of poor discomfort control. In 2003, the Federation of State Medical Boards of the United States called for an update to the Model Guidelines for the Use of Controlled Substances for the Treatment of Pain so that state medical boards could identify the inappropriate treatments of pain, including undertreatment, as departures from accepted medical practice (1). There are national standards (2) outlined by the Joint Commission (formerly known as the Joint Commission on Accreditation of Healthcare Orga-nizations) with regard to assessment and manage-ment of pain. Healthcare providers have been held legally responsible for poor pain control (3).
Despite the apparent need to manage pain, it is often undertreated. An obstacle to good pain control is lack of physician experience and educa-tion. Radiologists are an example of physicians who, in general, have limited experience in cases requiring pain control. This, however, does not mean that instances in which pain control is nec-essary do not occur in the radiology department. Biopsy and drainage procedures are painful, as are contrast material extravasations and placement of intravenous (IV) lines. Sedation may be needed in patients undergoing magnetic resonance (MR) im-aging or computed tomography (CT). Inpatients may require pain or sedation orders while they wait for an examination or procedure. These cases may be managed parenterally, but knowledge of nonparenteral pain control is also important. With the impetus for shorter hospital stays and outpa-tient treatment centers, radiologists need to know how to prescribe oral pain medications as well.
The objective of this article is to provide a seda-tion, analgesia, and local anesthesia reference guide for the busy radiologist. Joint Commission require-ments for healthcare providers who administer sedation are discussed. Medications are discussed in the text, and tables with dosages for the best known and most applicable agents are provided. Also discussed are the circumstances in which use of the anesthesia team is most appropriate.
General Concepts and Policies
SedationSedation is the administration of medications that calm the nervous system. Sedatives decrease awareness and responsiveness to external stimuli. They reduce anxiety, thereby making the psycho-logical unpleasantness of a procedure tolerable. Anxiety potentiates the perception of pain; there-fore, good sedation facilitates good pain control. Some sedatives have amnestic properties that are especially advantageous to patients anticipating multiple unpleasant procedures. Sedated patients are more likely to remain immobile, thus resulting in a quicker, safer, and more sterile procedure.
Sedation is classified on a continuum. Four levels of sedation are identified by the American Society of Anesthesiologists (ASA): minimal se-dation, moderate sedation, deep sedation, and general anesthesia (Table 1) (4). If the potential for respiratory depression and airway compromise exists, as in the case of moderate and deep seda-tion, the Joint Commission requires that providers of non-anesthesia sedation perform a preoperative evaluation of patients and monitor them while they are receiving sedation and during the recov-ery period (5). Quality and practice improvement programs exist and are especially important when sedation is performed by both anesthesia providers and nonanesthesiologists (5). Nonanesthesiolo-gists may be credentialed to perform moderate or deep sedation. No credentialing is necessary for minimal sedation. If radiologists are credentialed to perform sedation, they are usually credentialed to perform moderate sedation.
Sedation policies have been implemented at many hospitals. The overall goal of a procedural sedation program is to provide the best standard of care that yields the best outcome for patients in all settings. This program starts with the development of a comprehensive, practical policy that provides an institutional philosophy as a basis for seda-tion care standards (5). Preprocedure assessment and patient monitoring requirements are integral to sedation policies. Sedation consists of three phases: preprocedural assessment, intraprocedural monitoring, and postprocedural monitoring. Each phase has specific requirements intended to ensure patient safety.
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AnalgesiaAnalgesia is the symptomatic relief of pain with use of pharmacologic agents. Pain signals are received, but medication prevents the perception of the pain. Analgesics can be classified as either opioid or nonopioid. Opioids are drugs with opium- or morphine-like pharmacologic action. They act on opioid receptors in the peripheral and central nervous systems. Opiates are either natural alkaloids or synthetic derivatives. They are potent analgesics and are used to treat pain associated with injury, surgery, and medical con-ditions. They also have sedative, antitussive, and antirigor properties. Opioids are associated with undesirable side effects such as nausea, consti-pation, and central nervous system and respira-tory depression. Long term, opioid use can lead to tolerance and addiction. The actions of opi-oids are augmented when they are administered with benzodiazepines. Opioids have no maximal dose; they are titrated to effect. Nonopioid an-algesics are reserved for less severe pain and are not used intraprocedurally. They are not associ-ated with dependency and are the most used drugs worldwide. Their side-effect profiles factor into which nonsteroidal anti-inflammatory drug (NSAID) is most appropriate for a given patient at a given time.
Local AnesthesiaAnesthesia is the pharmacologic blocking of pain signal reception by the nervous system. Anesthesia may be general, regional, or local. Local anesthesia is the type most often used by radiologists. Local anesthetics stabilize nerve membranes by revers-ibly binding to sodium channels. Local anesthesia can be topical or infiltrative. Topical anesthesia is used to numb the surface of a body part. Infiltra-tive anesthetics are injected subcutaneously. Local anesthetics are divided into amides and esters; am-ides are more commonly used because they are, in general, more potent and longer acting.
Single or Combination TherapySedation, analgesia, and local anesthesia can be used alone or in concert, depending on the clinical circumstance. For example, when local anesthesia alone is insufficient to provide pain relief, IV opi-oid analgesia can be added. This is often the case during interventional procedures. Opioids ame-liorate pain but do not treat the anxiety a patient may experience undergoing an invasive procedure in an unfamiliar environment. Not only is anxiety unpleasant for patients, but pain is more resistant to analgesics when the patient is anxious. Sedatives
Table 1 Effects of ASA Levels of Sedation
Level of Sedation Responses to Stimuli AirwaySpontaneous Ventilation
Cardiovascular Function
Minimal Normal response to verbal stimulation
Unaffected Unaffected Unaffected
Moderate Purposeful response to verbal or tactile stimulation
No intervention required
Adequate Usually maintained
Deep Purposeful response after repeated or painful stimulation
Intervention may be required
May be inadequate Usually maintained
General anesthesia
Unarousable, even with painful stimulus
Intervention often required
Frequently inad-equate
May be impaired
Source.—Reference 4.
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treat the anxiety. When used together, sedatives and opioid analgesics act synergistically, enhancing each other’s effects. Local anesthetics, sedatives, and opioids can be used alone. Examples of cases in which they might be used alone are topical anesthetic applied to a small child before place-ment of an IV line, a sedative given to a claustro-phobic patient before the patient undergoes MR imaging, and the prescription of an oral opioid for an outpatient complaining of cramping after hysterosalpingography.
Patient Selection and AssessmentPresedation is the first phase in the care of a pa-tient undergoing moderate or deep sedation. The following measures should be completed before starting sedation: documented patient evalua-tion (history and physical examination within 30 days of the procedure and an update within 24 hours); documented discussion, including risks and benefits, and consent; documented plan for sedation; assurance that the appropriate person-nel and equipment are in place; and documented identification of the patient. Prevention of com-plications starts with a thorough preprocedural patient assessment (5). Age is an important factor to consider when administering sedation because metabolism and elimination are altered. Older patients frequently need a 30%–50% reduction in dose and more frequent dose intervals. Doses may also need to be decreased if kidney or liver function is impaired. On the other hand, people who are habituated to opioids or benzodiazepines may need higher doses than would normally be
expected. Smoking is the main cause of peri-procedural respiratory morbidity and mortality; therefore, cessation should be encouraged before sedation, if possible. Obesity, abnormalities of the neck, tongue, or teeth, and restricted mouth open-ing can lead to difficult airway management. The oropharynx should be examined, and a modified Mallampati score should be determined (Fig 1). A high Mallampati score, short distance between chin and thyroid cartilage, restricted mouth open-ing, short thick neck, and other abnormalities pre-dict difficult intubation and difficult or impossible mask ventilation and should alert the practitioner or physician that the patient is a poor candidate for moderate or deep sedation and may be difficult to intubate in an emergency (5). A medication his-tory, including supplements and prior reactions or allergies to medications and sedatives, must be obtained. Cardiovascular diseases such as hyper-tension, myocardial infarction within the previous 6 months, congestive heart failure, and arrhyth-mias indicate an increased risk of periprocedural complications. A respiratory status report should include whether the patient has asthma, chronic obstructive pulmonary disease, or other lung diseases. A gastrointestinal status report should include a history of gastroesophageal reflux, peptic ulcer disease, and nil per os (NPO) status. Fast-ing status is important as a predictor of aspiration, and it should be noted that fasting guidelines vary among institutions. Cardiovascular medication should be continued. Blood sugar levels should be routinely monitored in all patients with diabetes. If the procedure is emergent and the patient is not fasting, metoclopramide (Reglan) (10 mg IV) and an H2 blocker (eg, famotidine [Pepcid]) (10
Figure 1. Schematics of, A, Mallampati scoring classes during an airway examination and, B, visualization grades during direct laryngoscopy (5).
RG • Volume 33 Number 2 Moran et al E51
mg IV) can be administered to enhance stomach emptying and reduce the chance of aspiration. The ASA physical status is determined after consent is obtained (Table 2). Providers credentialed only for moderate sedation should not provide sedation to patients with an ASA physical status above III. Resuscitation equipment should be available in the procedure room should advanced cardiovascular life support be needed. Anesthesia backup should be available, and good communication with regard to highest-risk patients is essential.
The purpose of the presedation assessment is to determine the level of sedation the patient needs and that the sedation can be administered safely, and whether the nonanesthesiologist is equipped to administer that level of sedation. When the non-anesthesiologist is not equipped to administer the level of sedation needed safely, the provider may request an anesthesia consultation for monitored anesthesia care. Monitored anesthesia care is the administration of sedation under the supervision of an anesthesiologist. The essential component of monitored anesthesia care is the assessment and management of anticipated physiologic changes during the procedure, with the provider of the anesthetic prepared and qualified to convert to general anesthesia, if necessary (5). Examples of patients who may benefit from monitored anesthe-sia care include those with Pickwickian syndrome or sleep apnea (5); both have tenuous airways that have the potential for obstruction. Patients who poorly tolerate invasive procedures or are undergo-ing painful procedures may require deep sedation. Deep sedation depresses consciousness; patients can be aroused only with painful stimuli. Although deep sedation is an effective anxiolytic technique, the ability to independently maintain ventilatory function may be impaired. Patients requiring deep sedation usually need monitored anesthesia care. Radiologists are rarely credentialed to administer deep sedation. A discussion of the most common deep sedatives is included in the next section.
Medications
Sedatives
Sedatives for Minimal and Moderate Sedation.—Sedatives act on the nervous system by a variety of mechanisms. The most common types of seda-tives are benzodiazepines. They facilitate the ac-tions of g-aminobutyric acid, the main inhibitory neurotransmitter in the central nervous system. Benzodiazepines act synergistically with opioids; they possess anxiolytic and amnestic properties. Most sedatives can be administered by a variety of routes, but IV is the most commonly used route before and during the procedure. Midazolam (Versed), lorazepam (Ativan), and diazepam (Valium) are all benzodiazepines. In addition to anxiolysis and amnesia induction, diazepam has anticonvulsant properties. Midazolam is the most common benzodiazepine used intraprocedurally because of its potency, rapid onset of action, and relatively short elimination half-life (1–4 hours) (6). Midazolam can be administered either intra-muscularly or intravenously. Lorazepam can be administered orally as well as intramuscularly and intravenously and has a mean elimination half-life of 15 hours (7) and a variable peak effect after IV injection (8); therefore, it is a less desirable agent, especially if the anticipated procedure length is short. Diazepam (including active metabolites) has an elimination half-life of 20–100 hours (7), thus making it a less desirable procedural agent. Diazepam is also painful with IV injection, but it can also be administered intramuscularly or orally. Diphenhydramine (Benadryl) is a sedative that blocks histamine-1 receptors. It is most commonly used in the radiology department for pretreatment of contrast reactions. Diphenhydramine has anti-cholinergic properties that limit its use in asthma, narrow angle glaucoma, and urinary retention.
Table 2 ASA Physical Status Classifications
Class Status
I Normal healthy patient without systemic diseaseII Mild to moderate systemic disease (ie, controlled hypertension, diabetes) or elderlyIII Severe systemic disease (ie, limited activity but not incapacitating)IV Severe systemic disease (constant threat to life and incapacitating)V Moribund and will die within 24 hours without surgical interventionVI Patient who is brain dead and undergoing anesthesia care for purposes of organ donationE This modifier is added to any of the classes to signify a procedure that is being performed as an emer-
gency and may be associated with a suboptimal opportunity for risk modification
Note.—Reprinted, with permission, from reference 5.
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The anticholinergic properties also contribute to side effects such as dry mouth, dizziness and seda-tion, which are exacerbated by concomitant use of certain medications, including MAO inhibitors. Adult parenteral dosages for sedatives are given in Table 3.
Sedatives for Deep Sedation.—Propofol, etomi-date, and ketamine are all examples of deep seda-tives. Propofol (Diprivan) is a popular deep seda-tive because of its fast onset time, fast recovery, and easy titratability. There are few residual effects after infusion is discontinued and a low occurrence of nausea and vomiting. Propofol can cause low oxygen and increased carbon dioxide levels and inhibit airway reflexes; it also has a narrow thera-peutic range. Etomidate (Amidate) is a deep seda-tive with hypnotic (without analgesic) properties. It produces minimal hemodynamic effects at clini-cally relevant doses, which makes it especially use-ful in patients with limited hemodynamic reserve. Its effect is rapid, and it has a residual depressant effect. Involuntary myoclonic movements are com-mon with etomidate, but these can be attenuated with a prior administration of an opioid. It is as-sociated with a higher occurrence of nausea and vomiting than propofol and is painful on injection; it can also transiently depress adrenocortical func-tion. Ketamine (Ketalar) is a phencyclidine deriva-tive that induces a dissociative state and analgesia. It is fast acting, with a return to consciousness within 15 minutes after a single dose (5). Respira-tory depression is minimal, so it is especially useful in patients susceptible to ventilatory depression. Hypertonus and purposeful skeletal muscle move-ments often occur with ketamine; it also causes
sympathetic nervous system stimulation and bron-chodilation with increased respiratory secretions. The sympathetic nervous system stimulation can cause an increase in blood pressure, heart rate, and cardiac output, but this can have the opposite effect in the critically ill, as a result of depletion of catecholamine stores. Unpleasant emergence can occur, but this can be lessened by concomitant use of a benzodiazepine.
Analgesics
Opioids: Intraprocedural Agents.—The intrapro-cedural opioids used at our institution are mor-phine, fentanyl, and hydromorphone (Dilaudid). Meperidine (Demerol) is another intraprocedural opioid. It should be mentioned that many opioid medicines are available and that the same prepara-tion may be manufactured by different companies under different names. Table 4 provides a list of opioids most likely to be encountered by radiolo-gists. Morphine and many codeine derivatives are used to treat moderate to severe pain. Morphine is supplied in tablet (sustained released and immedi-ate release), solution, suppository, and injectable forms. Morphine is glucoronidated to morphine-6- glucoronide, an active metabolite that is eliminated by the kidneys. In patients with kidney failure, therefore, morphine is contraindicated. Morphine also releases the most histamine relative to that released by other opioids and should not be used in asthmatic and hypotensive patients.
Fentanyl is a synthetic intraprocedural opioid with 50 to 100 times the potency of morphine; it is short acting, with fewer overall side effects than those associated with morphine. Fentanyl is associated with stiff chest syndrome, a rare but serious condition caused by rapid IV administra-
tion of fentanyl. The syndrome results in rigid-ity of skeletal muscles, including the intercostal muscles. Treatment is with succinylcholine and airway management (usually intubation) while the fentanyl-mediated effects are being reversed. Fentanyl is also supplied in tablet, lozenge, trans-dermal, buccal, and nasal spray forms.
Hydromorphone (Dilaudid) is a semisynthetic derivative of morphine. It has four to eight times the potency of morphine, with fewer side effects, and has antitussive effects in addition to analgesia. In addition to the injectable form, it is available in tablet, liquid, and rectal suppository forms.
Meperidine (Demerol) is a parenteral opi-oid that requires separate discussion. It has one-tenth the potency of morphine, with local
anesthetic and antirigor properties, and is as-sociated with less sedation and itching; how-ever, it has other concerning side effects. It has atropine-like effects that result in dry mouth, tachycardia, and pupil dilation and is a myo-cardial depressant. Meperidine is metabolized to normeperidine, which is a central nervous system stimulant; therefore, seizure risk exists in cases of renal insufficiency or with high doses. It also interacts with many prescription drugs and over-the-counter medications (eg, Prozac and St John’s wort). Coadministration of serotonin reuptake inhibitors with meperidine can cause serotonin syndrome, a life-threatening adverse drug reaction resulting in autonomic instability
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with hypertension, tachycardia, hyperreflexia, dia-phoresis, hyperthermia, and agitation. For these reasons, meperidine is a second-line analgesic. Meperidine use at our institution is limited to patients with sepsis-related rigors in the recov-ery room.
Opioids: Agents Not Used Intraprocedurally.—Codeine, hydrocodone, and oxycodone are opi-oids that are not used during procedures. They are available in nonparenteral forms and are often combined with nonopioids to decrease their re-spective doses. Combining nonopioids with these opioids improves the clinical effectiveness of the opioids without increasing the risk of their side effects. The most common nonopioids used in combination with opioids are acetaminophen and aspirin. The maximum dosage for the combination agent is its maximum dosage when used alone. Exceeding the maximum dosage of the nonopioid increases the risk of side effects due to the nonopi-oid. The administration of a combination of opioid and nonopioid analgesics for this purpose is mul-timodal analgesia (10). A list of these combination
agents, with composition and dosages, can be found in Table 4. Codeine is an opioid that is used both as an antitussive agent and an analgesic and is available in tablet, suspension, and injectable forms. It is combined with a nonopioid in varying concentrations. Hydrocodone is a semisynthetic derivative of codeine that also has antitussive prop-erties and can be administered with a nonopioid in various combinations (Vicodin, Lorcet, and Lortab). These formulations are available in tablet form only. Oxycodone is a semisynthetic derivative of thebaine, another opioid, and can be combined with acetaminophen or aspirin to form Percocet and Percodan, respectively.
Nonopioids.—Nonopioids are not typically used intraprocedurally and are best reserved for outpa-tient use. Nonopioids in use are acetaminophen and NSAIDs. Acetaminophen can cause liver toxicity when taken in excess of 4 g per day but poses no gastrointestinal tract or bleeding risk. NSAIDs are more effective for treating inflam-mation but have side effects that can potentially affect cardiac, gastrointestinal, and renal systems. NSAIDs can also interfere with normal platelet
Table 4 (continued) Adult Dosing for Analgesics: Opioids
Brand Name Composition Tab/Solution/Inj How Supplied Dosing
function. Because of their side-effect profile, NSAIDs should not be taken for more than 2 months. They are divided into nonselective and selective COX-2 inhibitors. Celecoxib (Celebrex) is a selective COX-2 inhibitor, with less gastro-intestinal irritation and bleeding. Nonselective COX-2 inhibitors are divided into carboxylic acid, acetic acid, and propionic acid derivatives. Aspirin is an acetylated carboxylic acid deriva-tive. Diflunisal (Dolobid) is a nonacetylated car-boxylic acid derivative. Aspirin is associated with gastrointestinal irritation and bleeding; diflunisal is better tolerated by the stomach. Indomethacin (Indocin) and ketorolac (Toradol) are acetic acid
derivatives. Indomethacin is associated with cen-tral nervous system and gastrointestinal side ef-fects. Ketorolac provides excellent pain relief and can be administered parenterally. It should, how-ever, not be used longer than 5 days, as long-term use can result in renal toxicity or liver injury. Ibuprofen (Advil, Motrin) and naproxen (Aleve, Naprosyn) are propionic acid derivatives. Both ibuprofen and naproxen can cause hypertension and fluid retention. Adult dosages for nonopioid analgesics are provided in Table 5. Schematics outline the relationships among nonopioids in Figures 2 and 3.
Table 5 Adult Dosing for Analgesics: Nonopioids
Brand name Component Tab/Solution/Inj How Supplied Dosing
Aleve Naproxyn Caplet 220 mg 440 mg po within 1st hr then 220 mg po q 8–12 hrs prn pain
Max 660 mg/d or 440 mg in any 8–12 hr period
Naprosyn Naproxyn Tablet 250, 375, 500 mg 500 mg initially then 250 mg po q 6–8 hrs or 500 mg q 12 hrs prn pain
Max 1500 mg/dNaprosyn Naproxyn Solution 125 mg/5 mL 500 mg initially then 250 mg po
q 6–8 hrs or 500 mg q 12 hrs prn pain
Max 1500 mg/d
Source.—Reference 9.
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Local AnestheticsLocal anesthetics can be topical or infiltrative. Topical anesthetics are available in creams, ointments, aerosols, sprays, lotions, and jellies. Emla Cream is an example of a topical anes-thetic. It is composed of 2.5% prilocaine and 2.5% lidocaine; it is applied to intact skin with an occlusive dressing for at least 1 hour before a minor dermal procedure. Local anesthetics are divided into amides and esters; amides are more commonly used. Lidocaine is an aminoamide local anesthetic and is the most frequently used. Mepivacaine, bupivacaine, and ropivacaine are longer-acting amides. Bupivacaine has shown more cardiac toxicity than lidocaine. Ropiva-caine was developed as a considerably less toxic alternative to bupivacaine, with similar pharma-cologic properties. Procaine and chloroprocaine are aminoester local anesthetics. A list of local anesthetics with their durations of action and toxic doses are presented in Table 6.
Local anesthetic systemic toxicity (LAST) is a risk when a too large subcutaneous dose is ad-ministered, and LAST can be seen as well when the dose is delivered to the wrong location (eg, intravascular injection). Different regions dem-onstrate different related blood levels when in-jected with local anesthetics (eg, intercostal and caudal doses result in the highest blood levels). Lightheadedness, mouth numbness, ringing in the ears, and a metallic taste sensation are early signs of LAST. Later signs include nervousness, blurred vision, tremors, seizures, and cardio-vascular collapse. A rapid anesthesia consulta-tion should be requested if LAST is suspected. Prompt and effective airway management is cru-cial to prevent hypoxia and acidosis, which po-tentiate LAST. Lipid emulsion therapy for intra-vascular bupivacaine toxicity is recommended. Vasopressors reverse cardiovascular collapse; cardiopulmonary bypass should be considered if these therapies fail. Seizures are managed with benzodiazepines and airway support (5).
Figures 2, 3. (2) Diagram shows the relationships among nonopioids. (3) Dia-gram shows the relationships among NSAIDs. ASA = aspirin.
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“Allergies” to local anesthetics have been reported. The putative allergen is para-amino-benzoic acid, a derivative of aminoester local anesthetics. This derivative is used as a preserva-tive in many aminoamide local anesthetic prepa-rations. Allergy to one class of local anesthetics (eg, aminoesters) will result in a similar allergy to other anesthetics within the class (eg, another aminoester). If in doubt, always request an anes-thesiology consultation.
There are ways to lessen pain experienced with anesthetic infiltration. Reassurance, anes-thetic warming, slow injection, sedation, and topical anesthetics all lessen discomfort. Pinch-ing the skin in the area of injection reduces the discomfort because the input from large touch fibers obscures pain signals from smaller pain fibers. If more than one access is needed to provide anesthesia to a large area, later accesses should be in previously anesthetized regions. Alkalinization with 8.4% sodium bicarbonate lessens the acidity of the anesthetic, which also decreases pain. Alkalinization, however, is asso-ciated with precipitation if used in bupivacaine
in ratios similar to those in lidocaine. The sug-gested ratio of sodium bicarbonate to lidocaine is 1:10 and 1:35 to bupivacaine (5).
Intraprocedural Monitoring during Sedation
Intraprocedural monitoring is the second phase in moderate sedation and deep sedation patient care. The respiratory rate and electrocardiogram are monitored continuously, and blood pressure is checked every 5 minutes and before every sedative dose. Monitoring can be done by either a physician or registered nurse, as long as the provider is credentialed for moderate sedation. The minimum monitoring requirements are presented in Table 7. Any deviation from the ex-pected effects of the planned level of sedation or analgesia should be immediately reported to the physician performing the procedure. The level of sedation should be recorded according to the Five-point Observer’s Assessment of Alert-ness/Sedation scale (Table 8). Pain assessment
Table 6 Local Anesthetics: Duration of Action and Maximum Doses
Trade Name Concentration (%)
Maximum Total Recom-mended Dose
Volume of Maximum Total
Recommended Dose
Average Onset and
Duration of Action
Procaine (Novocain) 0.25–0.5 350–600 mg 140–240 mL of 0.25%70–120 mL of 0.5%
should also be done by using the verbal descrip-tor, linear numeric, or face-pain scales.
If the patient becomes difficult to arouse or demonstrates oxygen desaturation or a drop in blood pressure, a reversal agent may be needed. Reversal agents are medications given to coun-teract the effects of drugs used for anesthesia. Reversal agents are used when patients are dif-ficult to arouse or experience cardiorespiratory depression secondary to the effects of opioids or benzodiazepines. Naloxone (Narcan) reverses the effects of opioids, and flumazenil (Romazicon) reverses the effects of benzodiazepines. Onset of opioid reversal is within 1–2 minutes of initiation and lasts 45 minutes (5). If opioids and benzodi-azepines are both contributing to the overdose, the opioid should be reversed first. Repeat doses may be needed because the duration of the effect of opioids is longer than that of the reversal agent (5). Onset of reversal for flumazenil occurs within 1–2 minutes of administration, and the duration of
the effect is 30–60 minutes (5). Refractory seizures may be precipitated in patients habituated to ben-zodiazepines, patients taking tricyclic antidepres-sants, or patients at high risk for seizures. As with Narcan, repeat doses may be needed because the duration of the effect of benzodiazepines is longer than that of the reversal agent (5). Table 9 lists the dosages for reversal agents for adults.
Postprocedural Monitoring
SedationPostprocedural monitoring is the final phase in moderate sedation and deep sedation patient care. The patient is monitored for postprocedural complications: in particular, deepening of seda-tion and respiratory depression, because the sed-atives are now unopposed by the anxiety and pain related to the procedure. The same parameters are monitored at least every 15 minutes until the patient returns to the preprocedural baseline for a minimum of 30 minutes after the last administra-tion of medication. If the patient received a rever-
Table 7 Monitoring Requirements for Different Anesthetic and Sedation Techniques
Parameter Moderate SedationDeep Sedation/
General Anesthesia
Blood pressure (invasive or noninvasive) X X
Pulse oximetry X XEKG X XTemperature XCapnography X (see ASA and other professional
society guidelines)X
Exhaled/inhaled anesthetic gas concentra-tion (intubated patients)
Table 8 Five-Point Observer’s Assessment of Alertness and Sedation
Level Description
1 No response to mild prodding or shaking2 Responds only after mild prodding3 Responds to name only if called repeatedly; slurred speech4 Lethargic response to name; mild slowing of speech5 Responds readily to name; normal speech
Source.—Reference 5.
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sal agent during the procedure, the monitoring period is generally extended to at least 2 hours after administration of the reversal agent (5). The Aldrete postanesthesia discharge score (Table 10) is the guideline used for discharge of patients from postanesthesia care (12). A minimum score of 9 is recommended. Physician reassessment is recommended if discharge criteria are not met within 2 hours.
Patient-controlled AnalgesiaPatient-controlled analgesia (PCA) is an im-portant pain control modality for the radiolo-gist, especially the interventional radiologist. PCA allows the patient to self-administer small doses of opioid analgesic by means of computer-controlled IV infusion. Procedures for which
a PCA pump might be useful include uterine artery and other solid-organ embolizations. PCA pumps can be prescribed by both anesthesiolo-gists and nonanesthesiologists. The PCA pump is programmable to control the dose delivered, time between doses (lock-out interval), total dose limit over a period of time (dose-hour limit), and background continuous infusion. With PCA, pain relief is possible without risk of overdose or long wait times between doses. PCA enhances patient satisfaction and reduces the total dose required to control acute pain. It is most useful in patients with good neurologic, pulmonary, and kidney function. A list of agents and dosages is provided in Table 11.
Table 9 Dosages of Reversal Agents for Adults
Brand Name Agent How Supplied Dosage
Narcan Naloxone 0.4, 1 mg/mL inj Depression–0.1–0.2 mg IV over 2 mins q 2–3 mins until desired response (may repeat q 1–2 hrs)
OD–0.4–2 mg IV q 2–3 mins up to 10 mg (IM/SQ OK if IV not available)
Romazicon Flumazenil 0.1 mg/mL inj 0.2 mg over 15 s; may repeat after 45 s and again at 60 s until desired response up to 1 mg
If resedation–repeat dosing may be given at 20 min intervals up to 1 mg/dose (0.2 mg/min) and 3 mg/hr
Source.—Reference 9.
Table 10 Aldrete Postanesthesia Discharge Score
Variable ParameterPostsedation
Score
Activity: can move voluntarily or on command
4 extremities2 extremities0 extremities
210
Respiration Can deep breathe/cough freelyDyspnea/shallow or limited breathing/
tachypneaApneic/mechanical ventilator
21
0Circulation (preoperative BP _____ mm Hg) BP ± 20% of presedation level
BP ± 20%–49% of presedation levelBP ± 50% of presedation level
210
Consciousness Fully awakeArousable on callingNot responding
210
Oxygen saturation (%) >92% on room airNeeds O2 to remain > 90%<90% with O2
210
Source.—Reference 12.
E60 March-April 2013 radiographics.rsna.org
ConclusionRadiologists must have a solid understanding of sedation, analgesia, and local anesthesia. Poor control of patient discomfort, regardless of the clinical environment, can lead to patient dissat-isfaction, difficulty in completion of radiologic procedures, and morbidity and mortality. If pain control is going to be an important aspect of the job, radiologists should also consider obtain-ing credentials for sedation. Courses are readily available in many venues for physicians and non-physicians. Anesthesia providers are experts in sedation and airway management, making them potential educational resources as well. Radiolo-gists should also recognize their limitations and embrace anesthesia consultation whenever it is in the best interest of the patient.
Acknowledgments.—The authors thank Mordecai Pot-ash, MD, Associate Professor of Clinical Psychiatry at Tulane University School of Medicine; Gregory J. Coff-man, MD, MS, Tulane University School of Medicine; and Franklin Rivera Bueno, Louisiana State University Department of Anesthesia, for their research assistance.
References 1. Federation of the State Medical Boards of the
United States. Model policy for the use of controlled substances for the treatment of pain. http://www.fsm b.org/pdf/2004_grpol_Controlled_Substances.pdf. Published May 2004. Accessed February 1, 2013.
2. Joint Commission comprehensive accreditation manual for hospitals: the official handbook. 2012; PC.01.02.07. C1, C2, C3, C4.
3. D’Arcy Y. Pain management standards, the law, and you. Nursing 2005;35(4):17.
4. American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-Anesthesiolo-gists. Practice guidelines for sedation and analgesia by non-anesthesiologists. Anesthesiology 2002;96 (4):1004–1017.
5. Kaye AD, Gayle J, Kaye AM. Moderate and deep sedation in clinical practice. Cambridge, England: Cambridge University Press, 2012; 4, 8–30, 35, 48–50, 59, 85, 92–94, 110, 124–126, 137, 192, 204, 205, 274, 294.
7. Schuttler J, Schwilden H. Modern anesthetics. New York, NY: Springer, 2008; 344–345.
8. American Academy of Orthopaedic Surgeons, American College of Emergency Physicians. Criti-cal care transport. Sudbury, Mass: Jones & Barlett Learning, 2009; 196.
9. PDR.net. Montvale, NJ: PDR network. Accessed January 3, 2013.
10. Elvir-Lazo OL, White PF. Postoperative pain man-agement after ambulatory surgery: role of multimodal analgesia. Anesthesiol Clin 2010;28(2):217–224.
11. Windle WL. Infiltrative administration of local an-esthetic agents. Medscape reference 2011. http://emedicine.medscape.com/article/149178-overview. Updated May 4, 2011. Accessed June 2011.
12. Aldrete JA, Kroulik D. A postanesthetic recovery score. Anesth Analg 1970;49(6):924–934.
13. MacCallum MJ, Nelson LA, Lind LJ. Sedation, analgesia and anesthesia. In: Handbook of inter-ventional procedures. 4th ed. Baltimore, Md: Lip-pincott, Williams & Wilkins, 2011; 731.
Table 11 Suggested Drugs and IV Doses for PCA (Adult 70 kg)
DrugIntermittent
DoseFrequency (Lockout) Usual Basal Infusion Rate
Hydromorphone 0.2–0.5 mg 6–10 mins 0.2–0.5 mg/hr
Meperidine 10–15 mg 6–10 mins 15–50 mg/hrMorphine 1–2 mg 6–10 mins 0.5–1 mg/hrFentanyl 10–25 µg 2–5 mins 25–50 µg/hrAlfentanil 0.01–0.03 mg 1–3 mins Not recommended
Source.—Reference 13.
This journal-based SA-CME activity has been approved for AMA PRA Category 1 CreditTM. See www.rsna.org/education/search/RG.
Teaching Points March-April Issue 2013
Sedation, Analgesia, and Local Anesthesia: A Review for General and Inter-ventional RadiologistsThea C. Moran, MD • Alan D. Kaye, MD, PhD • Andrew H. Mai, MD • Leonard R. Bok, MD, MBA, JD
RadioGraphics 2013; 33:E47–E60 • Published online 10.1148/rg.332125012 • Content Codes:
Page E48Managing patient discomfort has always been important, but it has become especially important for physi-cians, given the current licensure, credentialing, and legal consequences of poor discomfort control.
Page E48Sedation consists of three phases: preprocedural assessment, intraprocedural monitoring, and postproce-dural monitoring. Each phase has specific requirements intended to ensure patient safety.
Page E51The essential component of monitored anesthesia care is the assessment and management of anticipated physiologic changes during the procedure, with the provider of the anesthetic prepared and qualified to convert to general anesthesia, if necessary (5).
Page E54Combining nonopioids with these opioids improves the clinical effectiveness of the opioids without increas-ing the risk of their side effects.
Page E59Patient-controlled analgesia (PCA) is an important pain control modality for the radiologist, especially the interventional radiologist.
