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Poly-lactic-glycolic acid microspheres: a biodegradable marker for the diagnosis of aspiration in hamsters.

Aspiration is a major cause of lung disease in infants and young children. As the symptoms and signs of aspiration are not specific, the diagnosis is delayed due to a low index of suspicion and low sensitivity and specificity of the available diagnostic tests. In the present study, we evaluated the utility of microspheres composed of a degradable polymer, polylactic glycolic acid (PLGA), as a marker to diagnose aspiration in hamsters. Thirty hamsters underwent direct tracheal instillation of 0.1 mL of a suspension of PLGA. Eighteen other animals served as controls and underwent tracheal instillation of 0.1 mL of saline. Three animals served as naive controls and had no tracheal instillation. Five animals from the PLGA group and three from the saline group underwent whole-lung lavage (WLL) on days 1, 8, 15, 29, 43, and 58. PLGA microspheres were easily identified under light microscopy inside the alveolar macrophages obtained from WLL in all PLGA-instilled animals during all studied days. The number and size of PLGA microspheres within the alveolar macrophages decreased gradually with time with a 90% rate of disappearance of about 36 d. There was a marked neutrophilic response in lung lavage and a mild peribronchial neutrophil infiltration on the first day after tracheal instillation of PLGA which subsequently disappeared. We conclude that PLGA microspheres are a sensitive and specific marker for aspiration in hamsters. The usefulness of this test in diagnosing aspiration in humans should be further evaluated in clinical studies.

Animals↗

Intravenous administration of the proton pump inhibitor omeprazole reduces the risk of acid aspiration at emergency cesarean section.

This study documented gastric pH and volume, and the number of patients at risk for acid aspiration of gastric contents, in a group of mothers undergoing emergency cesarean section under general anesthesia. Patients were randomized in a double-blind fashion to receive omeprazole 40 mg intravenously or placebo at the time of decision to proceed to cesarean section. In addition, all patients received 10 mg intravenous metoclopramide and 30 mL of 0.3 M sodium citrate. Aspiration of gastric contents was undertaken immediately after endotracheal intubation (PI) and before tracheal extubation (PE). Patients with both pH < 3.5 and volume > 25 mL were deemed to be at risk of acid aspiration should regurgitation occur. Only cases where the study-drug-to-PI-aspiration interval was > 30 min were evaluated. There were 282 patients in the study group and 259 in the control group. PI, 11 patients (4.25%; 95% confidence interval [CI] 1.79-6.71) were at risk in the control group compared with 4 (1.42%; 95% CI 0.04-2.8) in the study group (P = 0.045). The omeprazole-to-PI-aspiration interval in these four cases was < or = 40 min. PE, 19 (7.3%; 95% CI 4.17-10.51) patients were at risk in the control group compared with 2 (0.7%; 95% CI 0-1.69) in the study group (P < 0.0001). Mean pH in patients receiving omeprazole was significantly higher (P < 0.001) than in the control group. Gastric volumes were significantly lower in the omeprazole group compared with the control group at both PI (P = 0.006) and PE (P = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Detection and quantification of laryngotracheopulmonary aspiration with scintigraphy.

Aspiration is analyzed by a new scintigraphic technique and standard videofluoroscopy in 78 patients with head and neck pathology and neurologic disorders. When both methods are compared to clinical aspiration and a positive x-ray film of pneumonia, they appear to complement each other and provide a very accurate evaluation. Scintigraphy is a more sensitive method for detecting aspiration below the vocal cords and also provides for flow dynamics and a method of quantifying the amount of aspirated material. Videofluoroscopy shows more clearly the mechanism of the swallowing disorder and how the bolus enters the tracheobronchial tree. Studies in patients following head and neck surgery demonstrate a high incidence of dysphagia, aspiration, and pneumonia.

Deglutition↗

The pathophysiologic changes following bile aspiration in a porcine lung model.

Aspiration of bile is an underpublicized aspiration syndrome. Using a porcine lung model, the physiologic response and the histopathology of lung tissue were evaluated after the intratracheal instillation of sublethal doses of bile. Twenty-one domestic swine (11 to 19 kg) were the studied population. Three groups of five swine were evaluated: a control group received intratracheal physiologic saline (pH 7.45); study group 1 received strained gastric contents (pH 2.24); and study group 2 received strained bile (pH 7.19). All animals received the solutions at 0.5 ml/kg intratracheally. Lungs of six additional animals were studied (two gastric, two bile, and two physiologic saline) after aspiration by scanning electron microscopy (SEM). A seventh untreated animal was used as the SEM control. The physiologic data were analyzed using analysis of variance for repeated measures. The SEM and histopathologic results were graded by an observer blinded to the groups and were analyzed using the analysis of variance (ANOVA) and Scheffe tests. The group with bile aspiration was consistently characterized by significant deterioration of PaO2, the alveolar-arterial (A-a) gradient, shunt fraction, and static compliance (p < 0.01); and the light histopathologic and SEM findings demonstrated pathologic changes in the bile-exposed lung (p < 0.05) greater than the gastric- or saline-exposed lungs. It is concluded that bile aspiration produces a severe chemical pneumonitis leading to noncardiac pulmonary edema.

Animals↗

Hyperoxia exacerbates microvascular lung injury following acid aspiration.

OBJECTIVES: To examine the effects of an increase in ambient oxygen (O2) concentrations on the extent of inflammatory pulmonary damage following acid aspiration. DESIGN: Prospective, controlled laboratory study. SETTINGS: University-affiliated animal research facility. SUBJECTS: Male, Long Evans rats weighing 250 to 300 g. INTERVENTION: Rats were injured by instillation of 1.2 mL/kg normal saline solution/HCl, pH= 1.25 (acid), into the lungs via a tracheotomy. Animals were allowed to awaken and were exposed to 21%, 50%, or 98% O2 for 0 to 5 h (n/group > or = 10). In a separate set of experiments, injured rats exposed to 98% O2 were treated with different doses of deferoxamine, just prior to injury. Uninjured rats and rats injured with normal saline solution, pH = 5.3, were used as the control group. MEASUREMENTS: Injury was determined by assessing lung function (lung compliance and arterial blood gases) and alveolar-capillary wall integrity (wet/dry weight, lung albumin permeability index [PI], and intrapulmonary hemorrhage [HI]). RESULTS: Intrapulmonary instillation of acid increased PI, HI, and decreased static lung compliance compared to uninjured control animals. Increased ambient oxygen following acid aspiration decreased lung compliance, 1.06+/-0.03 mL/kg/cm H2O, in oxygen-exposed lungs when compared to the lungs exposed to air, 1.26+/-0.04, following a low pH aspirate (p<0.05). An increase in protein leakage into the lung tissue was noted in oxygen-exposed animals, PI=1.33+/-0.10, vs air-exposed rats, 0.89+/-0.07 (p<0.05). The hyperoxia-induced increase in lung injury was prevented by 30 mg/kg or higher deferoxamine treatment, 0.78+/-0.05 (p<0.05). Exposure of animals to 98% O2 for 2 h was sufficient to produce the same increase in microvascular protein leakage as 5-h exposure to O2 following low pH aspirate. CONCLUSION: Hyperoxia increases acid aspiration-induced inflammatory microvascular lung injury. This appears to be mediated by production of reactive species of O2.

Animals↗

Efficacy of dye-stained enteral formula in detecting pulmonary aspiration.

STUDY OBJECTIVE: To determine the extent to which a mixture of human gastric juice and enteral formula stained with two concentrations of FD&C Blue No. 1 food dye (0.8 and 1.5 mL/L) is visible in suctioned tracheobronchial secretions following three forced small-volume pulmonary aspirations over a 6-h period in an animal model. DESIGN: Experimental 2 x 3 repeated measures. SETTING: Animal laboratory and an acute care hospital. PARTICIPANTS: Ninety New Zealand white rabbits weighing approximately 3 kg each, and 90 acutely ill adults who furnished gastric juice. INTERVENTIONS: A mixture of human gastric juice and enteral formula stained with 0.8 or 1.5 mL of dye per liter was instilled intratracheally over a 30-min period into anesthetized intubated animals at baseline, 2 h, and 4 h. A total of 0.4 mL/kg of the mixture was instilled at each session. Ninety minutes after each instillation, suctioned secretions were examined for visible dye and blood. MEASUREMENTS AND RESULTS: Dye was visible in 46.3% of the secretions (125 of 270). The concentration of dye had no significant effect on dye visibility. Blood that was present in 114 of 270 of the secretions (42.2%) interfered with dye visibility in all but two secretions. For reasons unknown, even in the absence of blood, dye visibility decreased from 90.2% (55 of 61 secretions) after the first aspiration event to only 61% (25 of 41 secretions) after the third aspiration event. CONCLUSIONS: Findings from this animal model study do not support the use of the dye method to detect repeated small-volume aspirations. For clinicians who choose to use the dye method in selected situations, it appears that a dye concentration of 0.8 mL/L may be as effective in detecting aspiration as a 1.5 mL/L concentration.

Animals↗

Early treatment with pentoxifylline reduces lung injury induced by acid aspiration in rats.

STUDY OBJECTIVES: To evaluate the effect of pentoxifylline treatment on gas exchange and mortality immediately after bilateral instillation of hydrochloric acid. DESIGN: Randomized, prospective, placebo-controlled trial. SETTING: Animal laboratory of a university hospital. SUBJECTS: Twenty-four, adult, male Sprague-Dawley rats. METHODS: Sevoflurane-anesthetized rats (n = 12 in each group) underwent tracheostomy and insertion of a cannula into a hind paw vein and the left carotid artery. All animals received volume-controlled mechanical ventilation (zero positive end-expiratory pressure; fraction of inspired oxygen, 0.21). Acute lung injury was induced by instillation of 0.4 mL/kg 0.1 mol/L hydrochloric acid. The animals were randomized into two groups. The pentoxifylline group (n = 12) received a bolus of 20 mg/kg IV pentoxifylline after aspiration, followed by a continuous infusion of 6 mg/kg/h. The placebo group (n = 12) received an equivalent volume of saline solution. Arterial blood samples were collected for blood gas analysis 15 min and 0 min prior to aspiration and 30, 90, 180, 270, and 360 min after aspiration. Hemodynamic parameters, temperature, and ECG were recorded simultaneously. The primary end point was 6 h after aspiration. All surviving rats were killed by IV administration of pentobarbital. To assess morphologic changes due to lung injury, all animals underwent CT in inspiratory hold at the end of the experiment. MEASUREMENTS AND RESULTS: No difference in baseline measurements was observed. In pentoxifylline-treated rats, Pao(2) was significantly increased (p < 0.05) at 30, 90, 180, 270, and 360 min. Mortality at 6 h was 17% in the pentoxifylline group vs 67% in the placebo group. Placebo-treated rats showed significant abnormalities in CT lung scans compared with the pentoxifylline group. CONCLUSIONS: Acid aspiration impairs gas exchange and induces hypotension. Pentoxifylline administration shortly after acid instillation results in significant alleviation of impaired oxygenation, stabilization of BP with higher heart rates, and improved survival after 6 h.

Animals↗

Prevention and treatment of aspiration pneumonia in intensive care units.

Aspiration is a leading cause of nosocomial infection in the intensive care unit. Techniques to avoid or reduce aspiration are important in preventing pneumonia and pneumonitis. The most important preventive measures include the semi-recumbent position, the surveillance of enteral feeding, the use of promotility agents, and avoiding excessive sedation. The analysis of the pathogens involved in these syndromes usually shows a minor role for the anerobes. With regard to treatment, aspiration pneumonitis does not require any antimicrobials; on the contrary, aspiration pneumonia has to be treated. Empiric antimicrobials treatment should be started on clinical suspicion. The choice of the drug has to be guided by local pathogen epidemiology and clinical features; in fact, community type pneumonia requires a first-line antimicrobial such as amoxicillin/clavulanic acid. On the contrary, a nosocomial type of infection needs to be treated as a ventilator-associated pneumonia in agreement with published guidelines. Nevertheless, quantitative culture should be obtained in order to de-escalate antimicrobials. In conclusion, aspiration pneumonia is a frequently encountered disease that can be prevented by relatively simple measures.

Anti-Bacterial Agents↗

Diffuse bronchiolar disease due to chronic occult aspiration.

OBJECTIVE: To describe clinical, radiological, and histopathologic features of diffuse bronchiolar disease due to chronic occult aspiration. PATIENTS AND METHODS: We identified 4 patients encountered from July 2001 to January 2004 who had persistent respiratory symptoms and lung Infiltrates and who were eventually diagnosed by surgical lung biopsy as having diffuse bronchiolar disease due to chronic occult aspiration. Medical records, radiological studies, and histopathologic specimens were reviewed to assess their clinicoradiologic presentation and diagnostic features. RESULTS: The mean age of these 4 patients was 50 years (age range, 41-59 years), and 2 were women. All presented with persistent dyspnea, cough, and lung infiltrates. Three had a history of gastroesophageal reflux, but only 1 had active symptoms. Chest radiography showed interstitial infiltrates, whereas the predominant finding on computed tomography was numerous centrilobular nodules in all patients. Bronchoscopic lung biopsies had been performed in all patients, and the results were nondiagnostic. Surgical lung biopsy specimens revealed diagnostic features that consisted of bronchiolocentric organizing pneumonia with giant cells that contained material consistent with food in all 4 patients. CONCLUSION: Diffuse bronchiolar disease likely represents an underrecognized form of aspiration-related lung disease and may occur in relatively young Individuals without symptoms suggestive of recurrent aspiration. Radiological features associated with this disorder are distinctively different from those seen in aspiration pneumonia.

Adult↗

Radiographic and computed tomographic evaluation of experimentally induced lung aspiration sites in dogs.

This study was performed to radiographically examine the prevalence of aspiration sites and to evaluate their anatomical correlation with the bronchial patterns. Ten healthy beagle dogs were repeatedly radiographed, at weekly intervals, in the left and right lateral, ventrodorsal (VD) and dorsoventral (DV) positions. Three milliliters of iohexol distilled with same volume of saline was infused into the tracheal inlet. Which lung lobe was aspirated was decided upon by the presence of a significant alveolar pattern due to the contrast medium. Alveolar patterns were identified at the left (100%) and right cranial lung lobes (77%) with the dogs in dependant lateral recumbency, at the right caudal lung lobe (71%) with the dogs in VD recumbency and at the right middle lung lobe (59%) with the dogs in DV recumbency, respectively. The anatomical correlation was evaluated by performing computed tomography. The right principal bronchus (165.8+/-1.6 degrees ) was more straightly bifurcated than was the left principal bronchus (142.7+/-1.8 degrees , p < 0.01). In VD position, the right side lung had a greater opportunity to become aspirated. The ventrally positioned right middle lobar bronchial origin was more easily to be aspirated the other laterally positioned ones. We think that these anatomical characteristics can be one of the causes for aspiration pneumonia to occur more frequently in the right side lung.

Animals↗

Evaluation of ventilator-associated lower respiratory tract infection and tracheobronchial aspiration of gastrointestinal contents.

STUDY OBJECTIVE: Ventilator-associated lower respiratory tract infection (LRTI) in a set up of respiratory intensive care unit was evaluated. Also the incidence of tracheobronchial aspiration of gastrointestinal contents was explored among these patients. DESIGN: Twenty eight patients admitted in the respiratory intensive care unit of referral teaching hospital were studied. All patients were evaluated for tracheobronchial aspiration of gastrointestinal contents in the initial 48 hours of initiating mechanical ventilation using methylene blue as marker and glucostix reagent strip. Protected endotracheal aspirate was secured after 48 hours of beginning of mechanical ventilation and was submitted for microbiological assay. RESULTS: Of the 28 mechanically ventilated patients, 82% were found to have developed LRTI. Aerobic gram-negative bacilli accounted for 79% of the infections, Klesiella responsible for 39% while Pseudomonas and Escherichia accounted for 18% each. The remaining 4% were caused by Acinetobacter. Gram-positive cocci were responsible for 21% of infection with Staphylococcus and enterococci 14% and 7% respectively. Tracheobronchial aspiration of GI contents was found to be present in 72% of the patients which was significantly correlated with the incidence of LRTI (p=0.014). Significant association was also found between the incidence of LRTI and mortality (p=0.05). CONCLUSION: The incidence of gastrointestinal aspiration was found to be high and correlation with LRTI was significant. Both glucostix reagent strip and methylene blue were observed to have same positivity rate.

Adolescent↗

Appraisal of existing methodology in aspiration toxicity testing.

New methods or modifications of currently used methods in aspiration toxicology must be capable of accurately assessing the hazard and toxicity potentials of those products which are capable of being aspirated. The methods evaluated in the rat were intratracheal injections,intravenous injections, and modifications of the Gerarde technique. A product containing petroleum distillates and a standard viscosity petroleum distillate sample were administered to Osborne-Mendel rats, rabbits, and guinea pigs in ml/kg doses. The utility of the methods was determined by comparing lung weight increases, lung-body weight ratios, gross pathological lung changes, and mortality. The modified Gerarde technique showed the best potential for predicting aspiration hazard and toxicity based on the severity of the reactions which, using a radiolabeled oil, was shown to be a function of the amount of product which enters and reacts with the lungs. The influence of preventing the swallowing reflex to assure aspiration of the oil was assessed in the rat. The results show that less than 10% of the dose is aspirated when the swallowing reflex occurs. Methods of sacrifice were investigated for an effect on rat lung weight. No tested method except stunning with cervical dislocation produced an effect. Tests were conducted on rats and rabbits to determine differences in lung reactivity to the influence of inhalation anesthetics, pentothal sodium, or no anesthesia in response to petroleum distillate administration and to determine which test species is the better animal model. The resuls indicate that the rat is the better test model because of degree of lung reaction, size, and economy, and that inhalation anesthesia with ether is preferable over the other choices.

Animals↗

Gastric reflux and pulmonary aspiration in anaesthesia.

Although aspiration is a relatively rare event during anaesthesia, it represent an important cause of anaesthesia related mortality and also of ventilator associated pneumonia in intensive care unit. The incidence of aspiration is markedly increased after trauma owing to the risk of recent ingestion of food, depression of consciousness and airways reflexes, and gastric stasis induced by raised sympathoadrenal tone. The factors which contribute to the likelihood of aspiration include the urgency of surgery, airways problems, inadequate depth of anaesthetic, use of the lithotomy position, gastrointestinal problems, depressed consciousness, increased severity of illness and obesity. Factors that predispose to aspiration pneumonia are: a gastric content with a pH less than 2.5 and a gastric volume of 0.4 ml kg-1; a reduction in lower oesophageal sphincter tone; a reduction of upper oesophageal sphincter tone and a not coordination between the pharyngeal muscle and the upper oesophageal sphincter tone during swallowing; and a depression of protective airway reflexes. Methods to minimize regurgitation and aspiration involve control of gastric contents (preoperative starvation is the method universal accepted), application of cricoid pressure and control of the airways.

Anesthesia↗

[Study on apoptosis of lung tissue cells in patients with severe brain injury complicated with aspiration-induced lung injury].

OBJECTIVE: To investigate the role of apoptosis of pulmonary cells in aspiration induced lung injury in patients with severe brain injury with or without aspiration-induced lung injury. METHODS: The Glasgow scale (GCS) of 11 dead patients with severe closed brain injury was 3-8. There 11 cases were divided into aspiration-induced lung injury (AILI) and non-aspiration-induced lung injury (NAILI) groups. The plasma levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) were measured, and the ratio of apoptosis in lung tissue cells was also determined. RESULTS: The plasma levels of TNF-alpha and IL-8 in NAILI and AILI groups were (2.17+/-0.41)nug/L vs. (3.14+/-0.28)nug/L and (0.42+/-0.05)nug/L vs. (0.91+/-0.08) nug/L (P<0.05) respectively. Lung tissue cell apoptosis ratio was significantly higher in AILI group than NAILI group (P<0.01). CONCLUSION: TNF-alpha and IL-8 may induce apoptosis in lung tissues through different signaling pathway. During the early phase of aspiration-induced lung injury complicating severe closed brain injury, apoptosis in cells of lung tissue may play a role in the pathogenes.

Adult↗

Ranitidine and sodium citrate as prophylaxis against acid aspiration syndrome in obstetric patients undergoing caesarean section.

The efficacy of a single oral dose of 0.3M of sodium citrate alone as a prophylaxis against acid aspiration syndrome in obstetric patients undergoing LSCS (elective and emergency) was compared with that of intravenous ranitidine. One group of patients was given 30 ml of 0.3M sodium citrate orally just before the induction of anaesthesia while the other group was given 50mg of ranitidine intravenously together with the 30ml of 0.3M sodium citrate. This was done for both the elective and the emergency groups of patients. There was no significant difference in the mean pH of the gastric aspirate obtained from those given sodium citrate alone and those given sodium citrate and ranitidine in either the elective or the emergency group. However, in the emergency group, those who were given sodium citrate alone tend to have a larger volume of gastric aspiration when compared with those given ranitidine together with the sodium citrate. There were significantly more patients with gastric aspirates of more than 25ml in the emergency group to which sodium citrate alone was given. It would appear that supplementing an intravenous dose of ranitidine with the oral dose of sodium citrate is useful in emergency LSCS as a prophylaxis against acid aspiration syndrome.

Adult↗

High resolution computed tomography appearances of late sequelae of barium aspiration in an asymptomatic young child.

Barium aspiration is a well-known complication of upper gastro-intestinal studies. Consequences of aspiration are generally insignificant and leave no permanent changes in the lung parenchyma. However, large quantities of high density barium, if aspirated, lead to silent interstitial changes and fibrosis. High-resolution computed tomography HRCT appearances of lung changes have been demonstrated in adults; few such reports are available in the pediatric literature. We report a case of a child who aspirated barium 3 months before this presentation. The HRCT appearances of barium aspiration are presented with a review of the literature.

Barium↗

[An estimation chart for the possibility of aspiration in patients with severe motor and intellectual disabilities: its reliability and accuracy].

Although the most common cause of death in patients with severe motor and intellectual disabilities (SMID) is aspiration pneumonia, there are no criteria to detect aspiration. We have been making an evaluation tool to detect aspiration in patients with SMID easily, in cooperation with the project of comprehensive study of disability, social health, and welfare, supported by the Ministry of Health, Labor and Welfare, Japan. Here we studied the reliability and accuracy of the 2001 edition of the "questionnaires for functions of eating and swallowing" and "estimation chart for the possibility of aspiration" in 20 patients with risk of aspiration (13 with cerebral palsy, six with acquired cerebral palsy and one with muscle disease). Family members or nursing staffs taking care of them answered the questionnaires. A pediatrician and an occupational therapist or speech therapist checked the chart. Reliability was checked by the agreement between the estimation of the two professionals, and accuracy was determined by comparing the results of the chart and videofluolography. The results showed good reliability (kappa 0.63) and accuracy (kappa 0.47). Based on these results and additional analysis of the check items, the new edition of the chart was established.

Cerebral Palsy↗

[Aspiration and ingestion of dental instruments--diagnosis, treatment and prevention].

Aspiration and ingestion of foreign bodies of dental origin during treatment may cause a gastrointestinal and airway obstruction or perforation, and may constitute a life threatening situation. Ingestion occurs more often than aspiration and usually does not cause any clinical signs or symptoms. Most often it will spontaneously rejected from the gastrointestinal tract by peristaltic movement without any coimplication. However aspiration always requires treatment since foreign bodies there may cause inflammatory reaction and even severe obstruction and death. This article describes one case of aspiration and 3 cases of ingestion of dental instruments and materials. We discuss the diagnostic procedure: evidence of clinical signs and plain radiography, CT and the use of contrast material in case of radiolucent foreign bodies. The modern technique of endoscopy is successfully performed for diagnosis and treatment of foreign bodies in case of aspiration with minimal complications. We suggest a step by step protocol of treatment at the dental clinic in the case of ingestion/aspiration of foreign body and discuss several prevention techniques.

Adult↗