饱胃病人麻醉

Challenges andAdvances inIntubation: RapidSequence Intubation Sharon Elizabeth Mace, MD, FACEP, FAAPa,b,c,d,* Although there are no randomized, controlled trials documenting the benefits of RSI,7 and there is controversy regarding various steps in RSI in adult and pediatric pa- tients,8–13 RSI has become standard of care in emergency medicine airway manage- ment14–17 and has been advocated in the airway management of intensive care unit or critically ill patients.18 RSI has also been used in the prehospital care setting,14,19,20 a Cleveland Clinic Lerner College of Medicine of Case Western Reserve, Cleveland, OH 44195, , OH 44195, USA nue, Cleveland, OH 44195, 500 Metro Health Drive, nue, Cleveland, OH 44195. Emerg Med Clin N Am 26 (2008) 1043–1068 USA b Observation Unit, Cleveland Clinic, 9500 Euclid Avenue, Cleveland c Emergency Services Institute, E19, Cleveland Clinic, 9500 Euclid Ave USA d Case Western Reserve University, Metro Health Medical Center, 8 Cleveland, OH 44109, USA * Emergency Services Institute, E19, Cleveland Clinic, 9500 Euclid Ave E-mail address: maces@ccf.org DEFINITION/OVERVIEW Rapid sequence intubation (RSI) is a process whereby pharmacologic agents, specif- ically a sedative (eg, induction agent) and a neuromuscular blocking agent are admin- istered in rapid succession to facilitate endotracheal intubation.1 RSI in the emergency department (ED) usually is conducted under less than optimal conditions and should be differentiated from rapid sequence induction (also often ab- breviated RSI) as practiced by anesthesiologists in a more controlled environment in the operating room to induce anesthesia in patients requiring intubation.2–6 RSI used to secure a definitive airway in the ED frequently involves uncooperative, nonfasted, unstable, critically ill patients. In anesthesia, the goal of rapid sequence induction is to induce anesthesia while using a rapid sequence approach to decrease the possibil- ity of aspiration. With emergency RSI, the goal is to facilitate intubation with the addi- tional benefit of decreasing the risk of aspiration. KEYS � Intubation � Rapid sequence intubation � Endotracheal intubation doi:10.1016/j.emc.2008.10.002 emed.theclinics.com 0733-8627/08/$ – see front matter ª 2008 Elsevier Inc. All rights reserved. Mace1044 although the results have been mixed, especially in trauma patients (most notably in traumatic brain injury patients), such that an expert panel found that ‘‘the existing literature regarding paramedic RSI was inconclusive.’’20 Furthermore, training and experience ‘‘affect performance’’ and that a successful ‘‘paramedic RSI program is dependent on particular emergency medical services (EMS) and trauma system characteristics.’’20 ADVANTAGES AND DISADVANTAGES OF RAPID SEQUENCE INTUBATION The purpose of RSI is to make emergent intubation easier and safer, thereby increas- ing the success rate of intubation and decreasing the complications of intubation. The rationale behind RSI is to prevent aspiration and its potential problems, including as- piration pneumonia, and to counteract the increase in systemic arterial blood pres- sure, heart rate, plasma catecholamine release, intracranial pressure (ICP), and intraocular pressure (IOP) that occurs with endotracheal intubation. Blunting the rise in ICP may be critical in patients with impaired cerebral antoregulation from central nervous system illness/injury. Similarly, avoiding an increase in IOP may be desirable in the patient with glaucoma or an acute eye injury. RSI eliminates the normal protec- tive airway reflexes (such as coughing, gagging, increased secretions, and laryngo- spasm) that can make intubation more difficult. Use of RSI may limit cervical spine movement, thus, allowing for better control of the cervical spine during intubation with less potential for injury. RSI decreases the trauma to the airway that occurs with intubation. RSI should also decrease or eliminate the discomfort that occurs with intubation and the patient’s recall of the intubation.1 Disadvantages of RSI are (1) the potential for side effects or complications related to the drugs administered for RSI, (2) prolonged intubation leading to hypoxia, and (3) ‘‘emergent’’ or a ‘‘crash’’ airway resulting in a cricothyroidotomy or other ‘‘emer- gent’’ airway procedure.1 RAPID SEQUENCE INTUBATION:THE PROCEDURE RSI generally consists of seven steps: (1) preparation, (2) preoxygenation, (3) pretreat- ment, (4) paralysis with induction, (5) protection and positioning, (6) placement of the tube in the trachea, and (7) postintubation management.1,17 These seven steps can be modified when appropriate to fit the clinical situation.21 Step 1—Preparation Preparation involves having all the necessary equipment and supplies including med- ications that may be needed for an emergency intubation such as oxygen, suction, bag-valvemask (BVM), laryngoscope and blades, endotracheal (ET) tubes with a stylet with one size larger and smaller than the anticipated ET size, resuscitation equipment, and supplies for rescue maneuvers (eg, laryngeal mask airways [LMA] or cricothyrot- omy) in case of a failed intubation according to the Can’t Intubate, Can’t Ventilate American Society of Anesthesiologists (ASA) guidelines.22 The patient should have an intravenous line placed and be put on continuous monitoring to include vital signs (heart rate, respirations, blood pressure, pulse oximetry), cardiac rhythm monitoring, and, preferably, capnography. The mnemonic ‘‘SOAPME’’ is one way to remember the essential equipment needed for intubation: Suction, Oxygen, Airway, Pharmacology, Monitoring, Equip- ment.23 For the airway, include the ET tubes, laryngoscopes, blades, stylets, and BVM. For pharmacology, select, draw up, and label the appropriate medications (sed- ative, neuromuscular blocker, ancillary drugs) based on the history, physical Rapid Sequence Intubation 1045 examination, and equipment available. Monitoring should include pulse oximetry and cardiac monitoring at a minimum; also preferably with capnography.24 Assembling adequate personnel needed to assist in the procedure and assigning their roles is also a key component of the preparation phase. Patient assessment should be done at this time. A focused history and physical examination should be done to identify any condition, illnesses, or injuries that may negatively affect airway procedures/manipulations, medication administration, BVM ventilation, intubation, RSI, or rescue airway procedures. The preparation step is used to ‘‘MAP’’ (Monitor, Assemble, Patient assessment) out a treatment plan for intubation using RSI and a backup contingency plan in case of a failed intubation (can’t ventilate, can’t intubate scenario).25 Step 2—Preoxygenation Preoxygenation should be occurring during the preparation step. The purpose of pre- oxygenation is to replace the nitrogen in the patient’s functional residual capacity (FRC) with oxygen or ‘‘nitrogen wash-out oxygen wash-in.’’ ‘‘Denitrogenation’’ can be accomplished in 3 to 5 minutes by having the patient breathe 100% oxygen via a tight-fitting facemask or, if time is an issue, with four vital capacity breaths. Depend- ing on circumstances, as long a period of preoxygenation as possible, (up to 5 min- utes) should be administered. Ideally, positive pressure ventilation should be avoided during the preoxygenation step because of a risk for gastric insufflation and possible regurgitation. Because effective ventilation by the patient is not feasible in many ED patients, BVM ventilation may be necessary in apneic patients or patients with ineffective spontaneous breathing. In these instances, use of the Sellick proce- dure with gentle cricoid pressure should be applied in an attempt to limit gastric dis- tention and avoid aspiration during BVM ventilation. In the preoxygenation phase, replacing the nitrogen reservoir in the lungs with oxy- gen allows 3 to 5 minutes of apnea without significant hypoxemia in the normoxic adult.26 One caveat to remember is that certain patients have a lesser FRC (eg, infants and children and patients with an elevated diaphragm, specifically obese adults or pregnant patients). These patients will become hypoxic in a shorter time, eg, a normal child or an obese adult may start to desaturate within 2 minutes, while a normal adult may tolerate up to 5 minutes of apnea before they become significantly hypoxic.26 Step 3—Pretreatment Ancillary medications are administered during the pretreatment step to mitigate the negative physiologic responses to intubation. For maximal efficacy, the pretreatment drugs should precede the induction agent by 3 minutes, although this is not always possible. The pretreatment phase and preoxygenation phase can (and usually) do oc- cur simultaneously during most instances of RSI in the ED. Medications and their usual dosages that may be given during the pretreatment phase are lidocaine 1.5 mg/kg, fentanyl 2–3 mcg/kg, and atropine 0.02 mg/kg (minimum 0.1 mg, maximum 0.5 mg). The clinical indications for these drugs are (1) for patients with elevated ICP and im- paired autoregulation: administer lidocaine and fentanyl, (2) patients with major vessel dissection or rupture or those with significant ischemic heart disease give fentanyl, (3) adults with significant reactive airway disease, premedicate with lidocaine, and (4) at- ropine is indicated for pediatric patients%10 years old and in patients with significant bradycardia if succinylcholine is given. One caveat to remember is to give fentanyl with caution to any patient in shock (whether compensated or uncompensated) who is de- pendent on sympathetic drive because of a potential decrease in blood pressure with fentanyl administration. Mace1046 In patients who are receiving succinylcholine as their induction agent and who are at risk for increased ICP, one tenth of the normal paralyzing dose of a nondepolarizing (ND) neuromuscular blocking agent (NMB) can be given 3 minutes before receiving succinylcholine. The purpose of the defasciculating dose of the ND-NMB is to prevent the fasciculations (and therefore, the increase in ICP) that occurs with succinylcholine. For example, the dose would be 10% of the paralyzing dose of rocuronium (10% of 0.6 mg/kg5 0.06 mg/kg). The mnemonic ‘‘LOAD’’ has been used to indicate the pretreat- ment drugs for RSI: L5 lidocaine, O5 opioid (specifically, fentanyl), A5 atropine, and D 5 defasciculation.27 Step 4—Paralysis with Induction Paralysis with induction is achieved by the rapid intravenous administration in quick succession of the induction agent and the NMB. The selection of a specific sedative depends on multiple factors: the clinical scenario, which includes patient factors (in- cludes cardiorespiratory and neurologic status, allergies, comorbidity) and the clini- cian’s experience/training and institutional factors, as well as the characteristics of the sedative.28 Sedatives commonly used for induction during RSI are barbiturates (pentobarbitol, thiopental, and methohexitol),29 opioids (fentanyl),1 dissociative anes- thetics (ketamine),30 and nonbarbiturate sedatives (etomidate,31 propofol,32 and the benzodiazepines).21,33 The dosages and characteristics of these agents and are sum- marized in Table 1. One caveat to remember is that the induction dosages of these sedatives may be different (generally, slightly higher) than the dose used for sedation. For example, for etomidate the usual dose for procedural sedation is 0.2 mg/kg and for RSI is 0.3 mg/kg.31 Step 5—Protection and Positioning Positioning of the head and neck is essential to achieve the best view of the glottic opening for conventional laryngoscopy by aligning the three axes: oral, pharyngeal, and laryngeal. This is achieved by extension and elevation of the neck to obtain the ‘‘sniffing the morning air’’ or the ‘‘sipping English tea’’ position, assuming there are no contraindications such as known or potential cervical spine injury.1 Protection refers to the use of maneuvers to prevent regurgitation of gastric con- tents with possible aspiration. This is achieved via the Sellick maneuver, which is the application of firm pressure on the cricoid cartilage to avoid passive regurgitation of gastric contents. The correct performance of the Sellick maneuver involves the use of the thumb and index or middle finger to apply firm downward pressure on the cri- coid cartilage anteroposteriorly. Several caveats regarding the proper technique need to be considered: location, timing, and amount of pressure. Cricoid pressure should be applied as soon as the pa- tient starts to lose consciousness and should be maintained until the correct endotra- cheal position is verified. Pressure should be gentle but firm enough to compress the esophagus between the cricoid cartilage and the anterior surface of the vertebral body. The cricoid cartilage is opposite the C4–C5 vertebrae in an adult, and C3–C4 in an infant. Common mistakes include premature release of cricoid pressure, which puts the patient at risk for aspiration, especially if accidental esophageal intubation oc- curred; misplaced position (avoid applying pressure over the thyroid cartilage or entire larynx which may impede passage of the tube); and incorrect amount of cricoid pres- sure. The applied pressure should be graded and inversely related to the size of the patient with less force in smaller patients. One recommendation in smaller patients is placing the other hand under the neck to avoid changing the neck position while ap- plying cricoid pressure (with the opposite hand), to avoid malpositioning the neck. This Rapid Sequence Intubation 1047 is assuming there are no contraindications such as cervical spine injury. Should vom- iting occur, cricoid pressure should be released immediately because of possible esophageal rupture, although there are no data to substantiate this possible compli- cation, and neuromuscular blockade eliminates the possibility of active vomiting. Step 6—Placement of the Endotracheal Tube in the Trachea When the jaw becomes flaccid from the paralytics, it is time to begin intubation by standard methods. ET tube placement should be confirmed by the usual techniques. Step 7—Postintubation Management After ET tube placement and confirmation, the ET tube must be secured. A chest ra- diograph is done not only to check for proper ET tube placement but also to evaluate the pulmonary status and to monitor for any complications of the intubation and RSI. Continued sedation and analgesia, sometimes with paralysis as well as cardiopulmo- nary monitoring, is indicated as long as the patient requires advanced airway support. PHARMACOLOGY: SEDATIVE AGENTS FOR RAPID SEQUENCE INTUBATION According to the National Emergency Airway Registry (NEAR) study, the most fre- quently used induction agents were etomidate (69%), midazolam (16%), fentanyl (6%), and ketamine (3%).34 Considering just pediatric patients using the NEAR regis- try,6 etomidate was the most commonly used induction agent but was used in less than half the patients (only 42% compared with 69% for all patients),34 followed by thiopental (22%), midazolam (18%), and ketamine (7%).6 Etomidate Etomidate, the most commonly used sedative for RSI in adults, can also be adminis- tered for pediatric RSI.31 The usual dose is 0.3 mg/kg or 20 mg in a 70-kg adult. It often is used in trauma patients with known or potential bleeding, hypovolemic patients, and patients with limited cardiac reserve, because it does not have significant cardiovas- cular effects. Etomidate also decreases ICP and the cerebral metabolic rate, which suggests that it may have a neuroprotective effect. These features are why some cli- nicians consider it the sedative of choice in a patient who has multiple trauma with both a head injury and hemorrhage or shock. Etomidate does inhibit 11-b-hydroxylase, an enzyme necessary for adrenal steroid production.35 Transient adrenal suppression has been noted after a single dose of eto- midate, although this is probably not clinically significant.36 Some data indicate that etomidate has a negative impact on patient outcome in critically ill patients with sepsis and septic shock.37–39 This has led to the suggestion that a corticosteroid be coadmi- nisteredwhen etomidate is given for RSI.38 Although either dexamethasone (0.1mg/kg) or hydrocortisone (1–2mg/kg) may be given, dexamethasone often is chosen because it does not interfere with the adrenocorticotropin hormone (ACTH) stimulation test, which may be needed to later test for adrenal insufficiency. In any case, infusions of etomidate for continued postintubation sedation are contraindicated.39 Myoclonus is another side effect of etomidate that may interfere with intubation if a paralytic is not used,40 although this is not the situation with RSI in which a sedative and paralytic generally are coadministered in quick succession. Barbiturates Thiopental is the most commonly used barbiturate for pediatric RSI6 and may be the most commonly used barbiturate for anesthesia induction.41 However, it used is less Table 1 Medications for rapid-sequence intubation Sedatives Dose (IV) (mg/kg) for Intubation Indication Side Effects Precautions, Contraindication Reversal Agent Comment Etomidate 0.3 (usual 70 kg Adult dose 5 100 mg) Induction agent (sedative). Often used in hypovolemic, hemorrhaic patients, and in trauma patients, especially if head injury and hemorrhage Can cause myoclonic movements Adrenal insufficiency. Use with caution if in septic shock and sepsis and consider giving corticosteroid - Myoclonic movements may make intubation difficult if NMB not given Barbiturates, Thiopental 3–4 Induction agent (sedative). Used in patients with [ ICP if hemodynamically stable Negative CV effects. Use low doses cautiously if CV disease, shock, hypovolemia Porphyria - Avoid intra-arterial injection (can cause gangrene). Avoid extravasation; causes tissue necrosis Barbiturate, Methohexital 1–1.5 Induction agent (sedative). Used in patients with [ ICP if hemodynamically stable Causes histamine release Use with cause in asthmatics or if hypotensive - Avoid intra-arterial injection (can cause gangrene). Avoid extravasation (causes tissue necrosis). M a ce 1048 Ketamine 0.5–2.0 (Y dose if used with benzodiazepine or thiopental) Induction agent (sedative). Often used if hypovolemic, hemorrhage, shock Sympathomimetic effects [ ICP, [ IOP, [ BP, [ HR Consider alternatives if [ ICP, [ IOP may cause emergence reaction - Use with atropine if age%10 years or significant bradycardia Benzodiazepine, Midazolam 0.5–1.5 Induction agent (sedative) Respiratory depression, apnea, paradoxical agitation Minimal CV effects unless hypovolemic Flumazenil Dose varies widely, Y dose if given with opioids, in elderly, renal failure, liver disease, significant CV disease Propofol 1–2.5 (Y dose with age) Induction agent (sedative) Hypotension, hypoxia, apnea, bradycardia. Use cautiously if volume depletion, hypotension, CV disease Allergy to egg, soybean oil, EDTA - Ultra short acting. Negative CV effects limits its use in man ED-RSI patients Abbreviation: CV, cardiovascular. R a p id Se q u e n ce In tu b a tio n 1049 Mace1050 commonly than etomidate for ED RSI, at least partly because many ED RSI patients are hemodynamically unstable. Thiopental decreases both cerebral blood flow and the metabolic demands of the brain, which makes it an ideal sedative agent in patients with known increased ICP or patients with head injury who are hemodynamically sta- ble. Thiopental has negative cardiovascular effects: myocardial depression and pe- ripheral vasodilatation. Thus, hypotension with associated hypoperfusion can occur in patients who are hypovolemic or have myocardial depression. Generally, when hy- potension occurs, there is a co