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Mendelson Syndrome
Authors Irim Salik ; Tara M. Doherty. Affiliations Westchester MC/New York Med. College Maria Fareri Children's Hospital Last Update: June 26, 2021.
Continuing Education Activity
In Curtis Lester Mendelson’s original 1946 description of his namesake syndrome, chemical pneumonitis was described in young and healthy obstetrical patients following aspiration of gastric acid under anesthesia. The standard use of regional anesthesia for most laboring women and increased awareness among anesthesia providers regarding the high risk of aspiration and potential difficult airway management in parturients has increased the safety in this population. This activity reviews the evaluation and management of Mendelson syndrome and highlights the role of the interprofessional team in evaluating and improving care for patients with this condition. Objectives: Review the etiology of Mendelson syndrome. Describe the presentation of a patient with Mendelson syndrome. Summarize the treatment options for Mendelson syndrome. Outline the importance of improving care coordination among interprofessional team members to improve outcomes for patients with Mendelson syndrome. Access free multiple choice questions on this topic.
Introduction
In Curtis Lester Mendelson’s original 1946 description of his namesake syndrome, chemical pneumonitis was described in young and healthy obstetrical patients following aspiration of gastric acid under anesthesia.[1] In the case series by Mendelson, 66 obstetrical patients under anesthesia with ether aspirated gastric contents. Within two hours of the witnessed aspiration, patients developed respiratory distress and cyanosis.[2] Unilateral or bilateral lower lobe infiltrates were present on chest radiography. Although Mendelson’s sample had a positive outcome, subsequent studies have revealed that patients may develop acute respiratory distress syndrome (ARDS) following aspiration pneumonia.[3] Mendelson’s landmark study suggested that chemical pneumonitis was preventable by restricting oral intake during labor, which eventually led to the NPO guidelines we have in place today for parturients. The field of obstetrics and gynecology has come a long way since Mendelson’s time, as the use of general anesthesia is now infrequent for laboring women, and neuraxial analgesia is the standard of care for modern practice. At present, the American College of Obstetricians and Gynecologists encourage the ingestion of clear liquids and the avoidance of solid food during labor. Mendelson’s study reviewed the aspiration of gastric contents among 44000 pregnancies at the New York Lying-In Hospital from 1932 to 1945. His paper has two parts: a clinical report and an animal model. “Mendelson syndrome” 1 2 1 2
was initially described as aspiration of gastric contents causing a chemical pneumonitis characterized by fever, cyanosis, hypoxia, pulmonary edema, and potential death. Among the patients studied, there were 66 cases of aspiration (0.15%) and two deaths (0.0045%). Both patients tragically died following suffocation from solid food aspiration of full meals that were ingested six and eight hours before delivery, respectively. The remaining 64 patients experienced aspiration of liquid material, and they often went unrecognized with complete recovery.[1] Mendelson replicated the gastric acid in the respiratory distress syndrome he witnessed in human patients through his animal model. He placed both neutralized and untreated hydrochloric acid and vomitus from pregnant women into the respiratory tracts of rabbits. Mendelson found that during labor, there is prolonged retention of solids and liquids in parturients’ stomachs, and aspiration commonly occurs after abolishing laryngeal reflexes. During Mendelson’s time, the induction of general anesthesia was not limited to parturients undergoing a cesarean section but was also the method for spontaneous or operative vaginal deliveries. 21% of aspiration cases were among women who delivered via cesarean section, while 79% of women were undergoing general anesthesia for vaginal deliveries. The general anesthetic at this time consisted of a nonspecific mixture of gas, oxygen, and ether. The airway was left unsecured during delivery as parturients were subjected to mask induction and maintenance with an opaque black rubber mask. Following aspiration, the initial clinical course was severe including massive atelectasis with cyanosis, dyspnea, mediastinal shift, and radiographic signs of lung injury. Despite this, the 64 nonfatal cases were almost all liquid aspirations with radiographic resolution within seven days and clinical recovery within 36 hours without the use of antibiotic treatment.[1] Mendelson’s study led to several recommendations that still are in use in the obstetric population to this day. Pregnant women are treated as though they have a “full stomach” regardless of their last meal, and inhalational anesthesia without intubation is strictly avoided. Opaque rubber masks that can conceal regurgitation and vomitus have been replaced with clear plastic masks and ingestion of solid food has been discouraged during labor. Two American anesthesiologists, Paleul Flagg, and James Miller suggested that experienced anesthesiologists could help avoid the complications that Mendelson described. Miller reported over 26000 deliveries at Hartford Hospital with no mortality secondary to asphyxia, partially attributed to expert anesthesiology staff.[1] The argument was that safely administered general anesthesia could reduce the risk of aspiration in parturients. Although Mendelson’s contributions to obstetric anesthesia should not be understated, modern obstetrics has evolved considerably since then. During the last thirty years, aspiration in pregnant women has markedly declined, primarily due to advances in obstetrical anesthesia. The standard use of regional anesthesia for most laboring women and increased awareness among anesthesia providers regarding the high risk of aspiration and potential difficult airway management in parturients has increased the safety in this population. Care has also improved by advances in difficult airway management devices including video laryngoscopes, endotracheal tube introducers, optical stylets, and flexible endoscopes. The routine utilization of pulse oximetry, capnography, and difficult airway algorithms have also helped to mitigate the risks associated with general anesthesia in parturients.[4]
Etiology
There are specific physiologic changes of pregnancy that increase aspiration risk in this population. Minute ventilation, oxygen consumption, and carbon dioxide production are increased in early pregnancy, while the gravid uterus displaces the diaphragm upward in late pregnancy, substantially reducing functional residual capacity. Cardiac output, heart rate, stroke volume and circulating blood volume are all increased during pregnancy. The gravid uterus increases intra-abdominal pressure, predisposing patients to reflux. Progesterone-mediated relaxation of the lower esophageal sphincter (LES) and prolonged gastric emptying time increase the risk of gastroesophageal reflux disease and aspiration of gastric contents during general anesthesia.[5] The upper esophageal sphincter is made of striated muscle and is not affected by progesterone, but anesthetic induction will reduce its tone. Parturients must be on strict NPO guidelines (two hours for clear liquids, six hours for a light meal, and eight hours for a solid fatty meal).[6]
During pregnancy, chemical pneumonitis is more likely due to the plethora of anatomic and physiologic changes that are present. Almost all parturients have a gastric pH of less than 2.5, and greater than 60% of them have gastric volumes greater than 25 mL.[22] The lower esophageal sphincter (LES) is displaced cephalad and anteriorly, predisposing to its incompetence. Secretion of gastrin by the placenta causes hypersecretion of gastric acid in parturients. Opioids and anticholinergics reduce LES pressure and also delay gastric emptying, as does labor. Regardless of last oral intake, all parturients are considered to have a full stomach and to be at risk for pulmonary aspiration. Parturients exhibit an increased risk of difficult intubation following induction of general anesthesia. Circulating blood volume is elevated in these patients as a result of increased estrogen levels, leading to pharyngeal and laryngeal mucosal edema. Laryngeal anatomy is subject to distortion, the glottic diameter reduced, and bleeding is more likely during intubation due to friable pharyngeal mucosa. An enlarged tongue and redundant pharyngeal and palatal soft tissue can make glottic visualization with direct laryngoscopy challenging. Furthermore, mask ventilation may be difficult or impossible in these patients. Abdominal panniculus and enlarged breasts can impair mouth opening and laryngoscope introduction.[23] In a 2009 review by Djabatey et al., 1 in every 150 obstetrical patients is difficult to intubate, and 1 in every 280 patients is a failed intubation, as compared to 1 in 2230 failed intubations in the general population.[24][25] The majority of general anesthetics for the obstetrical population are performed for emergency cesarean sections, subjecting the patient and the medical team to a highly stressful situation. Anesthesiologists must be prepared to induce general anesthesia in this emergent situation where both maternal and fetal lives are potentially at risk. Due to high aspiration risk, pregnant women should undergo rapid sequence induction with cricoid pressure. Aspiration most commonly includes organisms from the oropharynx ( Staphylococcus aureus , anaerobic or gram-negative bacteria) particulate matter, liquids, or gastric acid.
History and Physical
Mendelson syndrome may mimic pulmonary edema in its presentation with an acute onset following aspiration. Patients present with dyspnea, cough, fever, and profuse frothy pink sputum. Symptoms may be indolent or can progress to pulmonary necrosis with lung abscess or empyema. On physical examination the patient is tachypneic, having tachycardia and crackles on auscultation of chest mostly on the right lower part which is the most dependant area for the aspirated contents.
Evaluation
The diagnosis of Mendelson syndrome depends upon clinical history, including a witnessed aspiration, risk factors, and characteristic chest radiography findings, although X-rays may initially be negative. Radiographic films may reveal irregular densities in the dependent pulmonary segments, primarily on the right side, which is at greater risk of aspiration due to the larger diameter and more vertical orientation of the right mainstem bronchus. Pulse oximetry can show oxygen desaturation and tachycardia. A computed tomography scan of the chest can reveal consolidation.
Treatment / Management
Although the best treatment should be primarily preventative, aspiration should be recognized and managed swiftly to curb dangerous sequelae. The patient should be in the Trendelenburg position, and the oropharynx suctioned. If the patient exhibits signs of hypoxia and diminished airway reflexes, swift intubation should follow. After an endotracheal tube is secured, a soft suction catheter should be passed to prevent the dislodgement of aspirated material further into the lung with positive pressure ventilation. In the case of aspiration of particulate matter, bronchoscopy and pulmonary lavage may prove useful. Mechanical ventilation and intensive care unit admission may be appropriate depending on the patient’s clinical status. Prophylactic antibiotics should not be utilized even in patients with radiographic findings of an infiltrate until the patient’s clinical condition warrants their use.
Prevention is via specific recommendations from the American society of anesthesiology (ASA). A modest amount of oral intake of clear liquids may be allowed for uncomplicated laboring patients up to two hours before anesthetic induction. While the volume of liquid ingested is unimportant, the presence of particulate matter is of significance in terms of aspiration risk. Solid foods are to be avoided in laboring patients and those with additional risk factors including diabetes, morbid obesity, and a difficult airway. For patients undergoing elective surgery, patients should fast for 6 or 8 hours depending on the fat content of the meal. Excessive sedation and some antipsychotic medications should be avoided as they can increase aspiration risk.[26] Medication prophylaxis is used routinely for parturients to mitigate the risks of aspiration pneumonitis. Clear nonparticulate antacids such as sodium citrate 15 to 30 mL orally every 3 hours maintain gastric pH greater than 2.5. Histamine receptor-2 antagonists such as ranitidine aid in reducing gastric acid volume and increasing pH. Prokinetic agents such as metoclopramide reduce gastric volume, increase LES tone and reduce peripartum nausea and vomiting. [26] Antiacid therapy has been shown to reduce the risk of chemical pneumonitis by neutralization of gastric pH.[27] Paranjothy et al. concluded that histamine receptor-2 antagonists in addition to nonparticulate antacids, such as sodium citrate, significantly increased gastric pH above 2.5 at intubation as compared to placebo.[28]
Differential Diagnosis
Mendelson syndrome mimics the presentation of many other disorders which should be ruled out. These include: Foreign body aspiration Near drowning Barium aspiration Acute exogenous lipoid pneumonia Chronic exogenous lipoid pneumonia Necrotizing pneumonia Aspiration pneumonia secondary to periodontal disease Pulmonary abscess status post laryngectomy Aspiration bronchiolitis Obliterative bronchiolitis Bronchitis Tuberculosis COPD/emphysema Adult epiglottitis Mycoplasma pneumonia Viral pneumonia
Prognosis
The prognosis of Mendelson syndrome depends upon the comorbid disease, the severity of aspiration, complications, and the patient's underlying health status. In Mendelson's 1946 original series, 66 obstetric patients aspirated gastric acid during their anesthetic, and almost all had a complete clinical recovery. Subsequent studies have included elderly
The outlook for patients with Mendelson syndrome remains guarded. Despite optimal treatment, there are still reports of mortality rates of close to 30%.[30](Level V)
Review Questions
Access free multiple choice questions on this topic. Comment on this article.
References
MENDELSON CL. The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol. 1946 Aug; 52 :191-205. [PubMed: 20993766] Bynum LJ, Pierce AK. Pulmonary aspiration of gastric contents. Am Rev Respir Dis. 1976 Dec; 114 (6):1129-36. [PubMed: 1008348] Doyle RL, Szaflarski N, Modin GW, Wiener-Kronish JP, Matthay MA. Identification of patients with acute lung injury. Predictors of mortality. Am J Respir Crit Care Med. 1995 Dec; 152 (6 Pt 1):1818-24. [PubMed: 8520742] Hawkins JL, Chang J, Palmer SK, Gibbs CP, Callaghan WM. Anesthesia-related maternal mortality in the United States: 1979-2002. Obstet Gynecol. 2011 Jan; 117 (1):69-74. [PubMed: 21173646] Marik PE. Pulmonary aspiration syndromes. Curr Opin Pulm Med. 2011 May; 17 (3):148-54. [PubMed: 21311332] ACOG Committee Opinion No. 441: Oral intake during labor. Obstet Gynecol. 2009 Sep; 114 (3):714. [PubMed: 19701066 ] Roberts RB, Shirley MA. Reducing the risk of acid aspiration during cesarean section. Anesth Analg. 1974 Nov- Dec; 53 (6):859-68. [PubMed: 4473928] Warner MA, Warner ME, Weber JG. Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology. 1993 Jan; 78 (1):56-62. [PubMed: 8424572] Raghavendran K, Nemzek J, Napolitano LM, Knight PR. Aspiration-induced lung injury. Crit Care Med. 2011 Apr; 39 (4):818-26. [PMC free article: PMC3102154] [PubMed: 21263315] Beaumont W. Nutrition Classics. Experiments and observations on the gastric juice and the physiology of digestion. By William Beaumont. Plattsburgh. Printed by F. P. Allen. 1833. Nutr Rev. 1977 Jun; 35 (6):144-5. [PubMed: 327355] Davies JM, Posner KL, Lee LA, Cheney FW, Domino KB. Liability associated with obstetric anesthesia: a closed claims analysis. Anesthesiology. 2009 Jan; 110 (1):131-9. [PubMed: 19104180] McDonnell NJ, Paech MJ, Clavisi OM, Scott KL., ANZCA Trials Group. Difficult and failed intubation in obstetric anaesthesia: an observational study of airway management and complications associated with general anaesthesia for caesarean section. Int J Obstet Anesth. 2008 Oct; 17 (4):292-7. [PubMed: 18617389] D'Angelo R, Smiley RM, Riley ET, Segal S. Serious complications related to obstetric anesthesia: the serious complication repository project of the Society for Obstetric Anesthesia and Perinatology. Anesthesiology. 2014 Jun; 120 (6):1505-12. [PubMed: 24845921] Green SM, Krauss B. Pulmonary aspiration risk during emergency department procedural sedation--an examination of the role of fasting and sedation depth. Acad Emerg Med. 2002 Jan; 9 (1):35-42. [PubMed: 11772667 ] Mhyre JM, Tsen LC, Einav S, Kuklina EV, Leffert LR, Bateman BT. Cardiac arrest during hospitalization for delivery in the United States, 1998-2011. Anesthesiology. 2014 Apr; 120 (4):810-8. [PMC free article: PMC4445354] [PubMed: 24694844] LOCK FR, GREISS FC. The anesthetic hazards in obstetrics. Am J Obstet Gynecol. 1955 Oct; 70 (4):861-75. [PubMed: 13258675] Mandell LA, Niederman MS. Aspiration Pneumonia. N Engl J Med. 2019 Feb 14; 380 (7):651-663. [PubMed: 30763196 ]
Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. 2001 Mar 01; 344 (9):665-71. [PubMed: 11228282 ] Lanspa MJ, Jones BE, Brown SM, Dean NC. Mortality, morbidity, and disease severity of patients with aspiration pneumonia. J Hosp Med. 2013 Feb; 8 (2):83-90. [PMC free article: PMC3774007] [PubMed: 23184866 ] Mays EE, Dubois JJ, Hamilton GB. Pulmonary fibrosis associated with tracheobronchial aspiration. A study of the frequency of hiatal hernia and gastroesophageal reflux in interstitial pulmonary fibrosis of obscure etiology. Chest. 1976 Apr; 69 (4):512-5. [PubMed: 1261317] Sladen A, Zanca P, Hadnott WH. Aspiration pneumonitis--the sequelae. Chest. 1971 Apr; 59 (4):448-50. [PubMed: 5551592] Hoefnagel A, Yu A, Kaminski A. Anesthetic Complications in Pregnancy. Crit Care Clin. 2016 Jan; 32 (1):1-28. [PubMed: 26600441] Goldszmidt E. Principles and practices of obstetric airway management. Anesthesiol Clin. 2008 Mar; 26 (1):109- 25, vii. [PubMed: 18319183] Djabatey EA, Barclay PM. Difficult and failed intubation in 3430 obstetric general anaesthetics. Anaesthesia. 2009 Nov; 64 (11):1168-71. [PubMed: 19825049] Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia. 1987 May; 42 (5):487-
- [PubMed: 3592174] American Society of Anesthesiologists Committee. 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: an updated report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology. 2011 Mar; 114 (3):495-511. [PubMed: 21307770] Lambert AA, Lam JO, Paik JJ, Ugarte-Gil C, Drummond MB, Crowell TA. Risk of community-acquired pneumonia with outpatient proton-pump inhibitor therapy: a systematic review and meta-analysis. PLoS One. 2015; 10 (6):e0128004. [PMC free article: PMC4456166] [PubMed: 26042842] Paranjothy S, Griffiths JD, Broughton HK, Gyte GM, Brown HC, Thomas J. Interventions at caesarean section for reducing the risk of aspiration pneumonitis. Cochrane Database Syst Rev. 2014 Feb 05;(2):CD004943. [PubMed: 24497372] van Westerloo DJ, Knapp S, van't Veer C, Buurman WA, de Vos AF, Florquin S, van der Poll T. Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia. Crit Care Med. 2005 Aug; 33 (8):1770-8. [PubMed: 16096455] Cicala G, Barbieri MA, Spina E, de Leon J. A comprehensive review of swallowing difficulties and dysphagia associated with antipsychotics in adults. Expert Rev Clin Pharmacol. 2019 Mar; 12 (3):219-234. [PubMed: 30700161 ] Copyright © 2022, StatPearls Publishing LLC. This book is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, a link is provided to the Creative Commons license, and any changes made are indicated. Bookshelf ID: NBK539764 PMID: 30969586
