A way forward in pulmonary aspiration incidence reduction: ultrasound, mathematics, and worldwide data collection

Abstract Aspiration of gastric contents during induction of general anesthesia remains a significant cause of mortality and morbidity in anesthesia. Recent data show that pulmonary aspiration still accounts for many cases with implications on mortality despite technical and technological evolution. Practical, ethical, and methodological issues prevent high-quality research in the setting of aspiration and rapid sequence induction/intubation, and significant controversy is ongoing. Patients' position, drugs choice, dosing and timing, use of cricoid force, and a reliable risk assessment are widely debated with significant questions still unanswered. We focus our discussion on three approaches to promote a better understanding of rapid sequence induction/intubation and airway management decision-making. Firstly, we review how we can use qualitative and quantitative assessment of fasting status and gastric content with the point-of-care ultrasound as an integral part of preoperative evaluation and planning. Secondly, we propose using imaging-based mathematical models to study different patient positions and aspiration mechanisms, including identifying aspiration triggers. Thirdly, we promote the development of a global data collection system aiming to obtain precise epidemiological data. Therefore, we fill the gap between evidence-based medicine and experts' opinion through easily accessible and diffused computer-based databases. A better understanding of aspiration epidemiology obtained through focused global data gathering systems, the widespread use of ultrasound-based prandial status evaluation, and development of advanced mathematical models might potentially guide safer airway management decision making in the 21st century.

Preoperative fasting for the infusion of "yerba mate": a randomized clinical trial with ultrasound evaluation of gastric contents

Abstract Background The traditional infusion of "yerba mate" is widely consumed in South America and exported to countries around the world. Although generally considered a "clear fluid", there is no data to date on the gastric emptying time of yerba mate and safe preoperative fasting intervals. The objective of this study was to evaluate the gastric emptying time of a standardized infusion of yerba mate using bedside ultrasound and compare it with the time confirm of hot and cold tea. Methods This was a prospective, randomized crossover experimental study. Thirty healthy volunteers were evaluated after 8 hours of fasting for both fluids and solids. Gastric antral area and gastric volume were evaluated at baseline and every 20 minutes after drinking 300 mL of randomly assigned infusion of "yerba mate", hot tea, or cold tea. Results The mean gastric emptying time was: 69.7 ± 22.1 min, 63.1 ± 14.5 min, and 64.3 ± 23.5 min for the mate, hot tea, and cold tea respectively. No significant differences were found in emptying time among the infusion groups (p-value = 0.043). When same time measures were compared, the only significant difference detected was between hot teas and mate infusion at 20 minutes (p-value = 0.012) Conclusion Yerba mate infusion has a similar gastric emptying time to that of tea. All subject's gastric volume returned to baseline values by 100 minutes. It is reasonable to recommend a similar fasting period of 2 hours for mate infusion prior to elective surgery.

Fatores predisponentes do volume residual gástrico após preparo expresso com manitol / Gastric residual volume factors after bowel preparation with mannitol express

ABSTRACT BACKGROUND: Bowel preparation with mannitol is a well-established method in Brazil. However, factors that interfere with the gastric emptying time period are yet to be known. Knowing these factors may favor the examination scheduling logistics and the individualized orientation for each patient. OBJECTIVE: Know the factors that can contribute to the gastric emptying time after intestinal preparation with express mannitol. METHODS: This is a prospective observational study to know factors that may contribute on the gastric emptying timing: predominant type of diet, comorbidities, medication usage, previous surgeries, number of evacuation per week, bearer of bowel obstipation, fecal type, diet type, number of evacuations after the home usage of bisacodyl before the ingestion of mannitol and number of evacuations after the ingestion of mannitol until reaching a proper bowel preparation. Before starting the colonoscopy exam, an upper digestive endoscopy exam was made to aspirate the gastric content. RESULTS: Sample was composed of 103 patients, 55 (53.4%) women, medium age 61 (±12.1) years, medium weight 75.3 (±14.1) kg, medium height 1.7 (±10) m and medium BMI of 26.6 (±3.9) kg/m2. Average gastric residual volume was 120.9 (0-900) mL. Gastric residual volume (GRV) below 100 mL (GRV ≤100 mL) occurred in 45 (43.6%) patients, 24 (53.3%) women, medium age of 61.0 years and medium BMI of 26.7 kg/m2. Gastric residual volume above 100 mL (GRV >100 mL) occurred on 58 (56.3%) patients, 29 (50%) women, medium age of 61.0 years and medium BMI of 26.2 kg/m2. Comparing both groups, average fasting time period after the ingestion of mannitol was significantly higher on the group with GRV ≤100 mL than group with GRV >100 mL, 123.1 (60-246) vs 95.3 (55-195) minutes, respectively. There was also statistical significance concerning the usage of ezetimibe 6 (13.7%) in the group with GRV ≤100 mL and statistical significance in the group with GRV >100 mL concerning the usage of paroxetine 3 (6.7%) and tadalafil 3 (6.7%) and surgical history of prostatectomy 3 (6.7%) and bridle withdrawal 3 (6.7%). CONCLUSION: We may conclude in this study that the usage of ezetimibe and fasting above 2 hours after the ingestion of mannitol decrease significantly the incidence of a GRV >100 mL. The usage of paroxetine, tadalafil and surgical history of prostatectomy or bridle withdrawal may contribute to increase de incidence of a GRV >100 mL.

RESUMO CONTEXTO: O preparo intestinal com manitol é um método bem estabelecido no Brasil. No entanto, os fatores que interferem no tempo de esvaziamento gástrico ainda não são conhecidos. O conhecimento desses fatores pode favorecer a logística de agendamento do exame e a orientação individualizada para cada paciente. OBJETIVO: Estudar os fatores que podem contribuir para o tempo de esvaziamento gástrico após o preparo intestinal com manitol expresso. MÉTODOS: Trata-se de um estudo observacional prospectivo com o objetivo de conhecer os seguintes fatores que podem contribuir no tempo de esvaziamento gástrico: tipo de dieta predominante, comorbidades, uso de medicamentos, cirurgias anteriores, número de evacuações por semana, portador de obstipação intestinal, tipo fecal, tipo de dieta, número de evacuações após o uso domiciliar de bisacodil antes da ingestão de manitol e número de evacuações após a ingestão de manitol até atingir o preparo intestinal adequado. Antes de iniciar o preparo intestinal, os pacientes responderam a um questionário clínico. O endoscópio foi introduzido para aspirar o conteúdo gástrico, antes de iniciar a colonoscopia. RESULTADOS: A amostra foi composta por 103 pacientes, sendo 55 mulheres, com média de idade de 61 anos, peso médio de 75,3 kg, altura média de 1,7 m e IMC médio de 26,6 kg/m2. O volume residual gástrico médio medido foi 120,9 (0-900) mL. Volume residual gástrico inferior a 100 mL (VRG ≤100 mL) foi encontrado em 45 (43,6%) pacientes, sendo 24 (53,3%) mulheres, com média de idade de 61,0 anos e IMC médio de 26,7 kg/m2. Volume residual gástrico acima de 100 mL (VRG >100 mL) ocorreu em 58 (56,3%) pacientes, sendo 29 (50%) mulheres, com idade média de 61,0 anos e IMC médio de 26,2 kg/m2. Comparando os dois grupos, notou-se que o tempo médio de jejum após a ingestão de manitol foi significativamente maior no grupo com VRG ≤100 mL do que no grupo com VRG> 100 mL, 123,1 (60-246) vs 95,3 (55-195) minutos, respectivamente. Também houve significância estatística em relação ao uso de ezetimiba 6 (13,7%), sendo maior no grupo com VRG ≤100 mL. Além disso, houve significância estatística no grupo com VRG >100 mL quanto ao uso de paroxetina 3 (6,7%) e tadalafil 3 (6,7%) e história cirúrgica de prostatectomia 3 (6,7%) e retirada de bridas 3 (6,7%). CONCLUSÃO: Podemos concluir neste estudo que o uso de ezetimiba e o jejum acima de 2 horas após a ingestão de manitol diminuem significativamente a incidência de um VRG> 100 mL. O uso de paroxetina, tadalafil e história cirúrgica de prostatectomia ou retirada de bridas podem contribuir para o aumento da incidência de um VRG >100 mL.

Fatal pulmonary aspiration during balanced sedation with dexmedetomidine and midazolam: A case report

Recently, balanced sedation has commonly been used during procedural sedation. Dexmedetomidine is known for its relative safety to cause “conscious sedation” with little respiratory depression but has some limitations such as frequent awakening and hemodynamic instability during surgery. To facilitate sedation, a small dose of midazolam can be co-administered rather than escalating the dose of dexmedetomidine, especially in elderly patient. Despite the respiratory safety profile of dexmedetomidine, the overall safety of co-administration has not been clarified. We describe the first case of fatal pulmonary aspiration that developed in an elderly patient during balanced sedation with spinal anesthesia for elective femur fracture surgery.

¿El reflujo gastroesofágico y la aspiración de contenido gástrico están implicados en la etiopatogenia y la progresión de la fibrosis pulmonar idiopática? / Does gastroesophageal reflux and gastric content aspiration have some role in the pathogenesis and progression of Idiopathic Pulmonary Fibrosis?

Resumen El reflujo gastroesofágico (RGE) y la aspiración oculta de contenido digestivo están probablemente implicados en la etiopatogenia y progresión de la fibrosis pulmonar idiopática (FPI). Los mecanismos patogénicos involucrados son la disminución de la distensibilidad pulmonar y el consiguiente aumento de la presión negativa intratorácica durante la inspiración, así como la disminución de los mecanismos de control de la motilidad esofágica o del tono del esfínter esofágico inferior. La prevalencia de RGE y anomalías de la motilidad esofágica están aumentadas en los pacientes con FPI comparado con la población general. Entre los pacientes con FPI, el 67-76% demostraron exposición anormal al contenido ácido en el esófago. Sin embargo, no hubo relación entre la gravedad del RGE y la gravedad de la FPI. Los estudios que han examinado el tratamiento antirreflujo en esta población han sido escasos. Incluso, algunos datos sugieren que el tratamiento antiácido puede ser perjudicial en algunos pacientes con esta condición. Después de analizar toda la evidencia relevante encontrada hasta la fecha, concluimos que no se puede establecer una relación causal entre el RGE, la aspiración del contenido gástrico y la patogénesis de la FPI. Además, existe escasa evidencia clínica que haya examinado el tratamiento antirreflujo en pacientes con fibrosis pulmonar idiopática.

ABSTRACT Gastroesophageal reflux (GERD) and hidden aspiration of gastric contents are probably involved in the pathogenesis and progression of idiopathic pulmonary fibrosis (IPF). The pathological mechanisms involved are decreased pulmonary distensibility and consequent increase of intrathoracic negative pressure during inspiration, as well as decreased control mechanisms of esophageal motility or lower esophageal sphincter. The prevalence of GERD and oesophageal dysmotility was higher in patients with IPF as compared with general population. Among patients with IPF, 67-76% demonstrated abnormal oesophageal acid exposure. However, no relationship was demonstrated between severity of GERD and severity of IPF. Data are scant on outcomes of antireflux treatment in patients with IPF. Actually, some data suggests that antacid treatment may be deleterious in some IPF patients. After analyzing all the relevant evidence found to date, a causal relationship between GERD, gastric content aspiration and IPF pathogenesis cannot be established. There is scant evidence examining antireflux treatment in idiopathic pulmonary fibrosis patients.

Effectiveness of the endotracheal tube cuff on the trachea: physical and mechanical aspects / Eficácia do balonete do tubo endotraqueal sobre a traqueia: aspectos físicos e mecânicos

Introduction: The inflation pressure of the endotracheal tube cuff can cause ischemia of the tracheal mucosa at high pressures; thus, it can cause important tracheal morbidity and tracheal microaspiration of the oropharyngeal secretion, or it can even cause pneumonia associated with mechanical ventilation if the pressure of the cuff is insufficient. Objective: In order to investigate the effectiveness of the RUSCH® 7.5 mm endotracheal tube cuff, this study was designed to investigate the physical and mechanical aspects of the cuff in contact with the trachea. Methods: For this end, we developed an in vitro experimental model to assess the flow of dye (methylene blue) by the inflated cuff on the wall of the artificial material. We also designed an in vivo study with 12 Large White pigs under endotracheal intubation. We instilled the same dye in the oral cavity of the animals, and we analyzed the presence or not of leakage in the trachea after the region of the cuff after their deaths (animal sacrifice). All cuffs were inflated at the pressure of 30 cmH2O. Results: We observed the passage of fluids through the cuff in all in vitro and in vivo experimental models. Conclusion: We conclude that, as well as several other cuff models in the literature, the RUSCH® 7.5 mm tube cuffs are also not able to completely seal the trachea and thus prevent aspiration of oropharyngeal secretions. Other prevention measures should be taken. .

Introdução: A pressão de insuflação do balonete (cuff) do tubo endotraqueal tanto pode causar isquemia de mucosa traqueal em pressões elevadas, e assim ocasionar morbidade traqueal importante, quanto pode causar microaspiração traqueal de secreção de orofaringe ou, ainda, ocasionar pneumonia associada à ventilação mecânica, caso a pressão do balonete seja insuficiente. Objetivo: A fim de investigar a eficácia do balonete do tubo endotraqueal RUSCH® 7,5mm, este estudo foi desenhado para investigar aspectos físicos e mecânicos do balonete em contato com a traqueia. Métodos: Para isto, foi desenvolvido modelo experimental in vitro para avaliar o escoamento de corante (azul de metileno) pelo balonete insuflado na parede de material artificial. Também foi desenhado estudo in vivo com 12 porcos da raça Large-White sob intubação endotraqueal. Foi instilado o mesmo corante na cavidade oral do animal e após óbito (sacrifício do animal) foi analisada a presença ou não de vazamento deste na traqueia pós-região do balonete. Todos os balonetes foram insuflados na pressão de 30 cmH2O. Resultados: Houve passagem de fluidos pelo balonete em todos os modelos experimentais in vitro e in vivo. Conclusão: Podemos concluir que, assim como diversos outros modelos de balonetes na literatura, balonetes do tubo RUSCH® 7,5mm também não são capazes de vedar completamente a traqueia e com isso prevenir aspiração de secreções orofaríngeas. Outras medidas para a prevenção devem ser tomadas. .

Effectiveness of milrinone for cardiogenic shock due to massive pulmonary aspiration: a case report / 대한마취과학회지

Pulmonary aspiration of gastric contents is one of the most frightening complications during anesthesia. Although pulmonary aspiration of gastric contents in general surgical patients is not common and resulting long-term morbidity and mortality are rare, severe hypoxemia and other sequelae of pulmonary aspiration continue to be reported. We report a case of massive aspiration of gastric contents during induction of general anesthesia, resulting in cardiac arrest due to severe pulmonary hypertension and myocardial infarction. Sustained cardiac arrest and shock that did not respond the conventional resuscitation was successfully treated using milrinone. The patient was discharged without complications in 20 days.

Usefulness of the Simplified Cough Test in Evaluating Cough Reflex Sensitivity as a Screening Test for Silent Aspiration

OBJECTIVE: To assess cough reflex sensitivity using the simplified cough test (SCT) and to evaluate the usefulness of SCT to screen for silent aspiration. METHODS: The healthy control group was divided into two subgroups: the young (n=29, 33.44+/-9.99 years) and the elderly (n=30, 63.66+/-4.37 years). The dysphagic elderly group (n=101, 72.95+/-9.19 years) consisted of patients with dysphagia, who suffered from a disease involving central nervous system (ischemic stroke 47, intracerebral hemorrhage 27, traumatic brain injury 11, encephalitis 5, hypoxic brain damage 3, and Parkinson disease 8). The SCT was performed using the mist of a 1% citric acid from a portable nebulizer. The time from the start of the inhalation to the first cough was measured as the cough latency. All the dysphagic patients underwent the videofluoroscopic swallowing study. RESULTS: The cough latency was more significantly prolonged in the healthy elderly group than in the healthy young group (p<0.001), and in the dysphagic elderly group than in the healthy elderly group (p<0.001). The sensitivity and specificity of SCT were 73.8% and 72.5% for detecting aspiration in the dysphagic patients, and 87.1% and 66.7% for detecting silent aspiration in the aspirated patients. CONCLUSION: Cough latency measured with the SCT reflects the impairment of cough reflex in healthy elderly and dysphasic subjects. The results of this study show that the SCT test can be a valuable method of screening aspiration with or without cough in dysphasic patients.

Gastric contents in respiratory tract a diagnostic dilemma at autopsy.

Gastric contents in the respiratory tract are commonly found at postmortem in acute alcoholism, occasionally during a fit of epilepsy and in dead bodies that have started decomposing. Quite infrequently it may be found in fresh bodies that have undergone sudden unexpected and unattended death leading to a dilemma as to the real cause of death with dearth of any other substantial evidence. Dead body of a 36-year-old lady was brought for post-mortem examination with history of unattended and unexpected death while taking bath after her afternoon meal. On gross and histopathological examination, there was no significant finding in the cardiovascular system but respiratory tract contained gastric contents with histopathology confirming vegetable matter in the terminal bronchioles. The conflicting literature on the difference between antemortem aspiration and postmortem spill of gastric contents into the respiratory tract led to a dilemma as to the real cause of death in present case. Dilemmas of the case with difficulties in diagnosis are being presented herewith.

Is the Six-hour Fasting before Abdominal Computed Tomography Necessary to Prevent Gastrointestinal Adverse Events in Patients with Abdominal Pain?

PURPOSE: We tried to determine whether six-hour fasting before abdominal computed tomography (CT) scan is necessary to prevent aspiration of gastric contents in patients with acute abdominal pain. METHODS: Adult patients with acute abdominal pain who were checked abdominal CT were enrolled. Exclusion criteria were age 7 days), renal impairment and hypersensitivity to contrast media. We compared Group-I ( or =6-hour fasting). We collected the demographic and clinical data on the causes of abdominal pain, pain duration, presence of nausea and vomiting, and use of medications before and after abdominal CT. In order to estimate the volume of gastric contents, we measured the area on the CT image which showed the largest volume of gastric contents. RESULTS: Among the 122 patients, Group-I consisted of 38 patients(31.1%) and Group-II included 84(68.9%). The demographic makeups of the two groups were similar, except for gender proportion (more males in Group-I). Group-I showed significantly greater gastric contents compared than Group-II(46.8+/-32.1 vs. 33.7+/-28.3, p=0.024). A slightly negative correlation (r=-0.2313; 95% CI=-0.3929 to -0.0559) was observed between the fasting time and the volume of gastric contents. However, the frequencies of the nausea [13/38 (34.2%) vs. 26/84 (31%), p=0.721] and vomiting [6/38 (15.8%) vs. 18/84 (21.4%), p=0.468] showed no difference between two groups. There were no aspiration events in either groups. CONCLUSION: Six hours of fasting before abdominal CT may not be required to prevent aspiration of gastric contents in patients with acute abdominal pain.

Preoperative Glycemic Status Affects the Risk for Acid Aspiration Pneumonia in Elective Cesarean Delivery / 대한마취과학회지

BACKGROUND: Although there are many studies of hypo- or hyperglycemia on gastric function, no studies have been conducted to determine the effect of glycemic status on preoperative gastric contents especially in pregnant women. We investigated the effect of dextrose infusion on preoperative gastric contents and serum gastrin in overfasting pregnant patients. METHODS: After six hours of fasting, forty pregnant patients scheduled for elective cesarean section were randomly assigned to one of two groups to receive either 120 ml/h of 5% dextrose fluid (Dextrose group, n = 20) or same rate of normal saline (Control group) until the induction of anesthesia. Before the start of combined spinal-epidural anesthesia, gastric contents were gently aspirated using a 14-F multiorifice nasogastric tube (Levin tube, Yushin Medical, Shiheung, Korea). Blood samples for the serum gastrin and glucose concentrations were taken. RESULTS: Aspirated gastric pH (2.7 vs. 2.9) and volumes (28.5 vs. 26.5 ml) were similar in the two groups. However, significantly more patients (40%) in the control group were found to be at risk of aspiration syndrome, pH 25 ml, than in the dextrose group (20%). The serum gastrin concentrations of the two groups were not significantly different (32.8 vs. 27.1 pg/ml). Preoperative glucose concentration did not correlate with gastric pH or volumes, but with serum gastrin concentration (tau-b = -0.347, vs. -0.466, P = 0.02). CONCLUSIONS: Preoperative dextrose infusion can decrease the number of patients at risk for pulmonary acid aspiration in overfasting pregnant women undergoing cesarean delivery.

The Suitable Time for the Removal of Laryngeal Mask Airway / 대한마취과학회지

BACKGROUND: There were several studies for the incidence of gastroesophageal reflux associated with the laryngeal mask airway (LMA), but the results of those studies were much different from one another. This conflicting results may be due to the time of the removal of LMA, which has been usually after the arousal (when the patient can open the mouth on command). So, the authors investigated the incidence of the gastroesophageal reflux and the regurgitation of gastric contents above the upper esophageal sphincter associated with the difference of the time of the removal of LMA. METHODS: Sixty three patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were allocated randomly to Group A (n=34, LMA was removed when the rejection signs such as struggle, restlessness, swallowing and cough came out.) or Group B (n=29, LMA was removed after arousal). For the detection of reflux and regurgitation episodes during anesthesia, a pH monitoring probe was positioned in the lower esophagus and a methylene blue (50 mg) gelatine capsule was swallowed just before induction. At the end of anesthesia, the episodes of reflux and regurgitation of gastric contents were analyzed according to the pharyngeal blue staining or pH< or = 4. RESULTS: The incidence of reflux (pH< or = 4) from the time of the rejection signs to the removal of LMA and the total incidence of reflux in Group B were significantly higher than that of Group A. No patient in both group showed pharyngeal staining of methylene blue. There was no clinical evidence of aspiration of gastric contents in either group. CONCLUSION: Maintenance of LMA until the patient can open the mouth on command seems to increase the incidence of the gastroesophageal reflux.

The Incidence of Regurgitation above Upper Esophageal Sphincter: Laryngeal Mask Airway vs Endotracheal Tube / 대한마취과학회지

BACKGROUND: From a clinical perspective, the regurgitation of the gastric contents above the upper esophageal sphincter has greater clinical relevance than gastroesophageal reflux. The authors investigated the incidence of regurgitation of gastric contents above the upper esophageal sphincter associated with the laryngeal mask airway(LMA) and the endotracheal tube(ETT) by methylene blue(50mg) gelatine capsule and pH probe in positive pressure ventilated patients during long surgical procedures . METHODS: Sixty patients scheduled for elective orthopedic surgery with a standardized general anesthetic technique were randomly allocated to receive either a LMA(n=34) or a ETT(n=26) for airway management. For the detection of regurgitation episodes during anesthesia, a pH monitoring probe was positioned in the hypopharynx 30 minutes before induction and a methylene blue capsule was swallowed just before induction. At the end of anesthesia, the episodes of regurgitation of gastric contents above upper esophageal sphincter were analyzed according to the pharyngeal blue staining or pH< or =4. RESULTS: There were no episodes of regurgitation of gastric contents(pH< or =4 or/and methylene blue staining) above the upper esophageal sphincter detected during the course of measurement. There was no clinical evidence of aspiration in either group. CONCLUSIONS: In comparison with ETT, the use of LMA does not appear to result in increased incidence of regurgitation of gastric contents above upper esophageal sphincter in positive pressure ventilated patients during long surgical procedures.