AANA Journal Course 3

Transcription

1 AANA Journal Course 3 Update for nurse anesthetists Aspiration prophylaxis: Is it time for changes in our practice? *6 CE Credits John J. Nagelhout, CRNA, PhD Pasadena, California Pulmonary aspiration of gastric contents during anesthesia is a complication that is fortunately rare, yet potentially catastrophic. Despite its infrequency, techniques geared toward preventing this serious outcome influence many of our routine practices and beliefs. Reports on large-scale clinical studies have opened new insights and questions about the effectiveness of long-standing anesthetic practices. These include conventional beliefs about preoperative fasting guidelines, acceptable gastric fluid volumes and ph, effective pharmacologic interventions, risk factors for pulmonary aspiration, and preventative anesthetic techniques such as rapidsequence induction. This AANA Journal course outlines current knowledge as to the incidence, risk factors, and efficacy of practices geared toward preventing aspiration. It is anticipated that this review will stimulate discussions regarding possible changes in the anesthetic management of patients in individual practice settings. Key words: Aspiration, cricoid pressure, preoperative fasting, preoperative medications, rapid-sequence induction. Objectives At the completion of the course, the reader should be able to: 1. Identify the patient groups that have an increased risk for aspiration. 2. Discuss the controversies regarding standard anesthetic practices to reduce aspiration. 3. Outline patient management and treatment of aspiration. 4. Describe current preoperative fasting and drug prophylaxis recommendations. 5. Contrast the various techniques for rapidsequence induction. Introduction Aspiration is a rare yet serious complication of general anesthesia. Much effort is given to prevention of this untoward event and minimization of sequelae if it does occur. New information is emerging that questions many long-standing practices and beliefs and may change routine clinical practice. This article reviews the incidence, risk factors, prevention, and treatment of this anesthetic complication. Incidence By definition, pulmonary aspiration has 2 compo- nents. First, gastric contents escape from the stomach into the pharynx and, second, enter the lungs. This results from preexisting disease, airway manipulation, and the inevitable compromise in protective reflexes that accompanies the anesthetic process. Aspirates are commonly categorized as contaminated, acidic, particulate, or nonparticulate. Fewer than half of all aspirations lead to pneumonia. 1 Pneumonia occurs most often in patients with pulmonary ingestion of virulent material or who are immunocompromised. Ingestion of highly acidic or particulate aspirate may cause severe respiratory damage without an infectious component. Patients who initially show no signs of infection, however, may develop pneumonia over the longterm due to the severity of the lung injury and prolonged respiratory support. 1 Several major reviews have been published regarding the incidence of aspiration during anesthesia. Olsson et al 2 retrospectively studied 185,358 anesthetics in Sweden and found 83 cases of aspiration for an incidence of 4.7 per 10,000 cases. Of the patients, 53% required no treatment; 47% of the cases were confirmed by x-ray. Of this 47%, 15 patients (17%) required mechanical ventilation and 4 patients died. Factors associated with significant morbidity were *AANA Journal Course No. 23: The American Association of Nurse Anesthetists is accredited as a provider of continuing education in nursing by the American Nurses Credentialing Center Commission on Accreditation. The AANA Journal course will consist of 6 successive articles, each with objectives for the reader and sources for additional reading. At the conclusion of the 6-part series, a final examination will be printed in the AANA Journal. Successful completion will yield the participant 6 CE credits (6 contact hours), code number: 25468, expiration date: July 31, AANA Journal/August 2003/Vol. 71, No

2 emergency procedures, pregnancy, obesity, gastrointestinal disease, elevated intracranial pressure, extremes of age, and airway difficulties. They concluded that clinically significant aspiration occurs in 1 per 35,000 anesthetics. In a multicenter, prospective study in France involving infants and children, the aspiration incidence rate was 5 cases in 40,240 anesthetics. High ASA physical status and emergency procedures were noted as risk factors. 3 The Australian Anaesthetic Incident Monitoring Study noted 133 cases of aspiration in 5,000 reported anesthesia incidents. 4 There were 5 deaths. Aspiration was confirmed by clinical signs or radiography. Predisposing factors included abdominal disease, obesity, diabetes, neurological deficit, lithotomy position, difficult intubation, reflux disease, hiatal hernia, and inadequate anesthesia leading to straining and bucking. Ezri et al 5 studied general anesthesia by mask in obstetric patients who required surgery immediately following vaginal delivery. Procedures included placental extraction; repair of vaginal, cervical, and perineal tears; and uterine manipulation. This database in Israel involved 1,705 anesthetics with 1 case of mild aspiration diagnosed by observation and follow-up chest x-ray. Warner et al 6 from the Mayo Clinic reviewed 215,488 general anesthetics. Pulmonary aspiration defined by particulates visualized in the tracheobronchial tree or radiographic confirmation occurred in 67 patients. Of the 66 patients who survived the surgery, 42 (63%) did not develop symptoms and were discharged the same day. Of the 24 (36%) who did develop symptoms, 13 required mechanical ventilatory support for more than 6 hours. Three of these patients died. The overall mortality was 1 per 71,829 anesthetics. Complications developed in equal percentages among those who received or did not receive pharmacological acid aspiration prophylaxis. Patients who aspirated did not develop problems and could be discharged within 2 hours of the incident if they met these 3 criteria: (1) They did not develop symptoms that included a new cough or a wheeze. (2) There was no decrease in SpO 2 of 10% or more of preoperative levels while breathing room air. (3) There was no radiographic evidence of pulmonary aspiration. Not surprisingly, the largest number of aspirations occurred during induction and intubation or on emergence within 5 minutes of extubation. They found no serious morbidity from pulmonary aspiration in nearly 120,000 elective procedures in patients classified as ASA physical status 1 or 2. In a later study, Warner et al 7 reported on the incidence of aspiration in infants and children. Unlike other reports they found there was no increased incidence in young patients. They noted 24 aspirations in a series of 63,180 general anesthetics. Fifteen of the 24 children did not develop symptoms within 2 hours, and no treatment was required. Five children required respiratory support, 3 for more than 48 hours. There were no deaths. Risk factors Numerous factors have been postulated as increasing the risk of aspiration during anesthesia. A list of the commonly noted factors is given in Table 1. Table 1. Risk factors for aspiration Emergency surgery Full stomach Obstetrics Gastrointestinal obstruction Ascites Diabetic gastroparesis Gastroesophageal reflux disease (GERD) Hiatal hernia Peptic ulcer disease Difficult airway management High gastric pressure/lower esophageal sphincter tone Impaired reflexes Head injury Depression of consciousness Seizures Obesity Scleroderma Trauma or stress Nausea and vomiting Opioids Cricoid pressure Cardiac arrest Severe hypotension Inadequate anesthesia Gastric volume and ph. It has long been thought that gastric fluid volume (GFV) of more than 0.4 ml/kg (25 ml/70 kg) and a ph of less than 2.5 are significant indicators of risk for aspiration sequelae. In 1974, Roberts and Shirley 8 published a classic article advocating these arbitrarily defined surrogate end points in patients undergoing cesarean section. These markers became widely accepted in clinical practice, and efforts to reach these levels preoperatively in many patient groups included insertion of nasogastric tubes and multidrug pharmacologic intervention. Questions are being raised as to the validity of the data behind these recommendations with the suggestion that a reappraisal is in order. 9 Since GFVs of more than 0.4 ml/kg are common, even with fasting, and 300 AANA Journal/August 2003/Vol. 71, No. 4

3 aspiration rarely accompanies these higher levels, the use of this marker seems less than realistic. In a report comparing gastric content differences in healthy obese vs lean patients, a GFV of more than 25 ml/70 kg and a ph of less than 2.5 were noted in 27% of obese and 42% of lean patients. 10 These data suggest that healthy obese patients do not exhibit delayed gastric emptying, and many patients routinely fall into the surrogate range of GFV of more than 25 ml/70 kg and a ph of less than 2.5 without aspiration. Acidity has a role in aspiration-induced lung damage; however, preoperative pharmacologic manipulation of gastric ph has not been proven clinically effective. 6,9,11 It has been suggested that the focus be shifted away from GFV and ph toward patient characteristics, condition, and anesthetic practices that place the patient at risk of pulmonary aspiration. Cricoid pressure. The use of cricoid pressure is another standard practice being questioned. It is difficult to apply properly and may impede intubation due to distortion of the airway, and application of cricoid pressure during rapid-sequence induction reduces upper and lower esophageal sphincter tone. 12,13 It is interesting to note that aspiration occurred despite the use of cricoid pressure in the Mayo Clinic study of 215,488 anesthetics discussed previously. 6 Upon failed intubation, cricoid pressure impedes insertion of a laryngeal mask airway for airway rescue and makes it more difficult to intubate through an in-place laryngeal mask airway. As one author noted in a recent review: There is no convincing evidence to suggest that cricoid pressure has reduced the incidence of aspiration or mortality. 14 Others believe that continued use with safer application and better training is warranted. 15 Laryngeal mask airway. The advent of the laryngeal mask airway has brought into question whether the increasing use of this airway-management technique leads to a greater frequency of aspiration. Several reports addressing this question support the conclusion that there is no increase in aspiration risk compared with the risk associated with a face mask. 16 An endotracheal tube remains the safest technique to ensure airway integrity. Positive pressure ventilation. Sellick 17 in his original article did not describe the need for apnea during rapidsequence induction. The practice of intentional apnea during rapid-sequence induction likely became popular with the 15-step description by Stept and Safar 18 in Concern regarding gastric distention and regurgitation during positive pressure ventilation and cricoid pressure was sufficient to recommend apnea before intubation. This recommendation is clearly opinionbased and not the result of clear data or evidence that the practice ever was or remains warranted. Clinicians are aware of the possibility of straining or bucking during light anesthesia. The rapid effect of modern induction drugs and improved techniques lead to the question of whether a reappraisal is in order. Light ventilation using what is commonly referred to as a modified rapid-sequence induction has not been shown to increase the risk of aspiration. As recently noted: Few things seem more counterintuitive to an anesthesiologist whose main responsibility is to maintain adequate oxygenation than to willfully cause apnea, drop oxygen reserves and reduce oxygen saturation, thereby handicapping themselves with a time constraint to intubate and oxygenate. 19 Prevention Pharmacologic prophylaxis for aspiration has been common practice for many years. Much of the concern arose from the finding that large volumes of acidic gastric contents, if aspirated, caused lung damage and increased the risk of serious morbidity and mortality. Agents such as gastrokinetics, histamine blockers, anticholinergics, antacids, proton pump inhibitors, and antiemetics are used alone or in various combinations to raise the gastric ph and lower gastric volume. Recent evidence questioning the benefit of this practice of routine administration of these agents in healthy patients without an increased aspiration risk has led to new practice guidelines. A task force appointed by the American Society of Anesthesiologists reviewed data with an evidence-based approach to the current fasting guidelines and drug prophylaxis. Their fasting guidelines are given in Table 2, and drug prophylaxis guidelines are in Table Evidence does not support the practice of routine preoperative administration of these gastric-related agents. Use in patients thought to exhibit risk factors should be continued. Table 2. Fasting guidelines* Ingested material Minimum fasting period (h) Clear liquid 2 Breast milk 4 Infant formula 6 Nonhuman milk 6 Light meal 6 * In the United Kingdom, pediatric anesthetists have encouraged 4-hour fasting times for breast milk and 6 hours for formula milk in neonates and nonhuman milk in children. 20 (Adapted from Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American Society of Anesthesiologists Task Force on Preoperative Fasting. 21 ) AANA Journal/August 2003/Vol. 71, No

4 Table 3. Drug prophylaxis for anesthesia Medication type and common examples Recommendation Gastrointestinal stimulants Metoclopramide Gastric acid secretion blockers Cimetidine Famotidine Omeprazole Lansoprazole Antacids Sodium citrate Sodium bicarbonate Magnesium trisilicate Antiemetics Droperidol Ondansetron Anticholinergics No use Atropine Scopolamine Glycopyrrolate Combinations of the above medications * The routine preoperative use of these medications to decrease aspiration risk in patients with no apparent increased risk is not recommended. The use of anticholinergics to decrease aspiration risk is not recommended. (Adapted from Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American Society of Anesthesiologists Task Force on Preoperative Fasting. 21 ) Treatment Treatment for the management of aspiration depends on the severity of the incident, type of aspirant, and rapidity of symptom development As noted earlier, if no significant symptoms develop within 2 hours of the aspiration, the patient is considered unlikely to become seriously compromised and may be discharged safely following a period of observation. Patients with evidence of particulate aspiration may benefit from bronchopulmonary lavage. Those with nonparticulate acid aspiration do not benefit from lavage or instillation of neutralizing solutions. Evidence indicates that the damage is immediate; 23 therefore, efforts to neutralize the aspirant are ineffective. Symptomatic chemical pneumonitis may require mechanical respiratory support to maintain blood gases at normal levels, and radiographic evidence may take a few hours to appear. Steroids that have been used commonly in the past have little efficacy and might, in fact, promote infection. Antibiotics may be used when there is direct evidence of infection. If the infiltrate clears within 24 to 48 hours, it is likely due to a noninfectious origin and antibiotic therapy is not warranted. Summary Synthesis of the data from several large-scale clinical studies and revised practice recommendations indicate that a review of many standard practices with regard to aspiration prophylaxis may be in order. These include the following: 1. The use of GFV of more than 0.4 ml/kg (25 ml/ 70 kg) and a ph of less than 2.5 should be abandoned as surrogate end points for aspiration risk. 2. Cricoid pressure as a requirement for rapidsequence induction may be beneficial as long as it is performed properly and does not impede effective airway management. 3. Patients should be ventilated during rapidsequence induction. There is no evidence that smooth, controlled light ventilation increases the incidence of aspiration. Prolonged periods of apnea should be abandoned. 4. Routine pharmacologic gastric prophylaxis in healthy patients with minimal risk for aspiration should not be given. 5. Realistic preoperative fasting guidelines should be instituted with respect to types of food or liquids ingested, patient age and characteristics, type of anesthetic and surgical procedure, and presence of risk factors. The rule of nothing by mouth after midnight for all patients should be modified. REFERENCES 1. Cassiere HA. Aspiration pneumonia: current concepts and approach to management. Medscape General Medicine. 1998;2:1:1-11. Available at: Accessed April, 12, Olsson GL, Hallen B, Hambraeus-Jonzon K. Aspiration during anaesthesia: a computer-aided study of 185,385 anaesthetics. Acta Anaesthesiol Scand. 1986;30: Tiret L, Nivoche Y, Hatton F, et al. Complications related to anaesthesia in infants and children: a prospective survey of 40,240 anaesthetics. Br J Anaesth. 1986;61: Kluger MT, Short TG. Aspiration during anaesthesia: a review of 133 cases from the Australian Anaesthetic Incident Monitoring Study (AIMS). Anaesthesia. 1999;54: Ezri T, Szmuck P, Stein A, et al. Peripartum general anaesthesia without tracheal intubation: incidence of aspiration pneumonia. Anaesthesia. 2000;55: Warner MA, Warner ME, Weber JG. Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology. 1993;78: Warner MA, Warner ME, Warner DO, et al. Perioperative pulmonary aspiration in infants and children. Anesthesiology. 1999;90: Roberts RB, Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesth Analg. 1974;53: Schreiner MS. Gastric fluid volume: is it really a risk factor for pulmonary aspiration [editorial[? Anesth Analg. 1998;87: Harter RL, Kelly WB, Kramer MG, et al. A comparison of the volume and ph of gastric contents of obese and lean surgical patients. Anesth Analg. 1998;86: Stoelting RK. NPO and Aspiration: New Perspectives in ASA Refresher Course Lectures. Park Ridge, Ill: American Society of Anesthesiologists; 2002;274: Brimacombe JR, Berry AM. Cricoid pressure. Can J Anaesth. 1997;44:4: AANA Journal/August 2003/Vol. 71, No. 4

5 13. Chassard D, Tournadre JP, Berrada KR, et al. Cricoid pressure decreases lower oesaphageal sphincter tone in anaesthetized pigs. Can J Anaesth. 1996;43: Ng A, Smith G. Gastroesophageal reflux and aspiration of gastric contents in anesthetic practice. Anesth Analg. 2001;93: Vanner RG, Asai T. Safe use of cricoid pressure. Anaesthesia. 1999;54: Brimacombe JR, Berry A. The incidence of aspiration associated with the laryngeal mask airway: a meta-analysis of published literature. J Clin Anesth. 1995;4: Sellick BA. Cricoid pressure to prevent regurgitation of stomach contents during induction of anaesthesia. Lancet. 1961;ii: Stept WJ, Safar P. Rapid induction-intubation for prevention of gastric-content aspiration. Anesth Analg. 1970;49: Vadhera RB. Airway management in patients at high risk of aspiration. In: Ovssapian A, Coalson DW, eds. Problems in Anesthesia. Vol. 13. Philadelphia Pa: Lippincott Williams & Wilkins, Inc; 2001: Emerson BM, Wrigley SR, Newton M. Preoperative fasting in paediatric anaesthesia: a survey of current practice. Anaesthesia. 1998;53: Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American Society of Anesthesiologists Task Force on Preoperative Fasting. Anesthesiology. 1999;90: Tasch MD. Pulmonary aspiration. In: Atlee JL, ed. Complications of Anesthesia. Philadelphia, Pa: WB Saunders; 1999: Levison ME. Pneumonia. In: Braunwald E, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, eds. Harrison s Principles of Internal Medicine. 15th ed. New York, NY: McGraw-Hill; 2001: Glover ML, Reed MD. Lower respiratory tract infections. In: Dipiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 5th ed. New York, NY: McGraw-Hill; 2002: AUTHOR John J. Nagelhout, CRNA, PhD, is the director of the Kaiser Permanente School of Anesthesia/California State University Fullerton, Pasadena, Calif. AANA Journal/August 2003/Vol. 71, No