High-frequency percussive ventilation attenuates lung injury in a rabbit model of gastric juice aspiration

OBJECTIVE

To test the effects of high-frequency percussive ventilation (HFPV) compared with high-frequency oscillatory ventilation (HFOV) and low-volume conventional mechanical ventilation (LVCMV), on lung injury course in a gastric juice aspiration model.

DESIGN

Prospective, randomized, controlled, in-vivo animal study.

SETTING

University animal research laboratory.

SUBJECTS

Forty-three New Zealand rabbits.

INTERVENTIONS

Lung injury was induced by intratracheal instillation of human gastric juice in order to achieve profound hypoxaemia (PaO2/FIO2< or =50). Animals were ventilated for 4h after randomization in one of the following four groups: HFPV (median pressure 15cmH2O); LVCMV (VT 6mlkg(-1) and PEEP set to reach 15cmH2O plateau pressure); HFOV (mean pressure 15cmH2O); and a high-volume control group HVCMV (VT 12ml kg(-1) and ZEEP).

MEASUREMENTS AND RESULTS

Static respiratory compliance increased after the ventilation period in the HFPV, LVMCV and HFOV groups, in contrast with the HVCMV group. PaO2/FIO2 improved similarly in the HFPV, LVCMV and HFOV groups, and remained lower in the HVCMV group than in the three others. Lung oedema, myeloperoxidase and histological lung injury score were higher in the HVCMV group, but not different among all others. Arterial lactate markedly increased after 4h of ventilation in the HVCMV group, while lower but similar levels were observed in the three other groups.

CONCLUSION

HFPV, like HFOV and protective CMV, improves respiratory mechanics and oxygenation, and attenuates lung damage. The HFPV provides attractive lung protection, but further studies should confirm these results before introducing HFPV into the clinical arena.

Colonization of dental plaque by respiratory pathogens in dependent elderly

Pneumonia can be a life-threatening infection, especially in the elderly, and it is a significant cause of morbidity and mortality. The purpose of this study was to assess the existence of oral infectious pathogens potentially causing the respiratory disease in the dependent elderly. The dental plaques of 138 dependent elderly were examined to identify microorganisms by the culture method. Twenty-one species of microorganisms were detected in the dental plaques in this study. In 89 cases out of 138 (64.5%), potential respiratory pathogens colonized in the dental plaques of the dependent elderly. The results of the present study revealed that bacteria that commonly cause respiratory infection colonized in dental plaques of the aged, dependent subjects. Therefore, dental plaques must be considered a specific reservoir of colonization and subsequent aspiration pneumonia in dependent elderly.

Hyoid Bone and Laryngeal Movement Dependent Upon Presence of a Tracheotomy Tube

The aim of this prospective, consecutive study was to investigate the biomechanical effects, if any, of the presence of a tracheotomy tube and tube cuff status, tube capping status, and aspiration status on movement of the hyoid bone and larynx during normal swallowing. Seven adult patients (5 male, 2 female) with an age range of 46-82 years (mean = 63 years) participated. Criteria for inclusion were no history of cancer of or surgery to the head and neck (except tracheotomy), normal cognition, normal swallowing, and ability to tolerate decannulation. Digital videofluoroscopic swallowing studies were performed at 30 frames/s and with each patient seated upright in the lateral plane. Variables evaluated included maximum hyoid bone displacement and larynx-to-hyoid bone approximation under three randomized conditions: tracheotomy tube in and open with a 5-cc air-inflated cuff; tracheotomy tube in and capped with deflated cuff; and tracheotomy tube out (decannulated). Differences between maximum hyoid bone displacement and larynx-to-hyoid approximation (cm) based on presence/absence of a tracheotomy tube, tube cuff status, and tube capping status were analyzed with the Student's t test. Reliability testing with a Pearson product moment correlation was performed on 21% of the data. No significant differences (p > 0.05) were found for both maximum hyoid bone displacement and larynx-to-hyoid bone approximation during normal swallowing based on tracheotomy tube presence, tube cuff status, or tube capping status. Intraobserver reliability for combined measurements of maximum hyoid displacement and larynx-to-hyoid approximation was r = 0.97 and interobserver reliability for the absence of aspiration was 100%. For the first time with objective data it was shown that the presence of a tracheotomy tube did not significantly alter two important components of normal pharyngeal swallow biomechanics, i.e., hyoid bone movement and laryngeal excursion. The hypothesis that a tracheotomy tube tethers the larynx thereby preventing hyoid bone and laryngeal movement during normal swallowing is not supported.

A review of patients with pulmonary aspiration of gastric contents during anesthesia reported to the Departmental Quality Assurance Committee

STUDY OBJECTIVE

Preoperative risk factors for pulmonary aspiration of gastric contents during anesthesia are well studied. There is lack of information as to factors or circumstances leading to aspiration.

DESIGN

A retrospective review of cases of pulmonary aspiration reported to the Departmental Quality Assurance (QA) Committee was undertaken.

SETTING

This study took place at a large tertiary care university hospital based in a metropolitan city.

PATIENTS

The study identified all patients reported to the QA Committee as having pulmonary aspiration during January 1991 to December 1994 and July 1996 to December 2000.

INTERVENTIONS

No interventions were done.

MEASUREMENTS

The medical records of all patients thus identified were reviewed to see if they had pulmonary aspiration according to strict criteria. Presence of preoperative known risk factors, prophylactic measures used against pulmonary aspiration, and perioperative events were noted.

MAIN RESULTS

A total of 47 patients were reported to the QA Committee as having pulmonary aspiration during this period. Upon review, 23 patients had pulmonary aspiration (definite aspiration, n = 12; probable aspiration, n = 11) and 24 patients did not meet the criteria for pulmonary aspiration of gastric contents. The incidence of pulmonary aspiration overall was 1 per 8671 anesthetics and 1 per 4385 anesthetics in patients younger than 16 years. If all 47 cases reported to QA Committee are presumed to have had pulmonary aspiration, then the overall incidence of aspiration is 1 in 4243 anesthetics. Eighteen of 23 patients had a preoperative risk factor, but preventive measures against aspiration had been used in only 4 patients. Five patients did not have any apparent preoperative risk factor.

CONCLUSIONS

This study confirms that pulmonary aspiration of gastric contents is a rare complication during modern anesthesia. Preoperative risk factor was present in most patients who had pulmonary aspiration. A clear understanding of risk factor/s is needed to prevent further cases of pulmonary aspiration.

Intubation conditions after rocuronium or succinylcholine for rapid sequence induction with alfentanil and propofol in the emergency patient

BACKGROUND AND OBJECTIVE

Previous studies mainly conducted on elective patients recommend doses of 0.9-1.2 mg kg[-1] rocuronium to obtain comparable intubation conditions with succinylcholine 1.0 mg kg[-1] after 60 s during a rapid-sequence induction. We decided to compare the overall intubating conditions of standard doses of rocuronium 0.6 mg kg[-1] and succinylcholine 1.0 mg kg[-1] during a strict rapid-sequence induction regimen including propofol and alfentanil.

METHODS

Male and female patients (ASA I-III) older than 17 yr scheduled for emergency abdominal or gynaecological surgery and with increased risk of pulmonary aspiration of gastric content were randomized to a rapid-sequence induction with succinylcholine 1.0 mg kg[-1] or rocuronium 0.6 mg kg[-1]. Patients with a predicted difficult airway were excluded. A senior anaesthesiologist 'blinded' for the randomization performed the intubation 60 s after injection of the neuromuscular blocker. Intubating conditions were evaluated according to an established guideline. Tracheal intubation not completed within 30 s was recorded as failed.

RESULTS

222 patients were randomized. Three patients had their operation cancelled and 10 did not fulfil the inclusion criteria. Clinically acceptable intubation conditions were present in 93.5% and 96.1% of patients in the succinylcholine group (n=107) and the rocuronium group (n=102), respectively (P=0.59).

CONCLUSIONS

During a rapid-sequence induction with alfentanil and propofol, both rocuronium 0.6 mg kg[-1] and succinylcholine 1.0 mg kg[-1] provide clinically acceptable intubation conditions in 60 s in patients scheduled for emergency surgery. Under the conditions of this rapid-sequence induction regimen rocuronium may be a substitute for succinylcholine.

[The management of dysphagia -- part 2: therapy]

In the first part of the article we described diagnostic methods aiming to resolve the individual underlying pathomechanism of chronic swallowing disorders (dysphagia). From these, we deducted different therapeutic measures that can be applied either alone or in combination. Weakening of the upper esophageal sphincter with botulinum toxin is reserved for patients with structural stenosis or a relative hyperfunction of the sphincter. It can be tried to use the "Passy-Muir Valve" for tracheostomized patients that aspirate. Most cases benefit from a therapy that consists of specific exercises. "Restitution" relies on exercises to practice new movement patterns as well as improvement of muscle strength. "Compensation" is based on exercises to counteract structural and/or functional deficits. Through "adaptation" residual, therapy resistant disease can be alleviated through dietary planning of consistency, temperature, and nutrient content of food. In many cases it is necessary to combine "restitution", "compensation", and "adaptation".

[Unilateral neurogenic pulmonary edema. A case report]

A vascular lesion was identified in the posterior cerebral fossa in a 65-Year-old stroke victim. The patient suddenly developed unilateral pulmonary edema. Bilateral alveolar opacities is the usual radiological aspect of neurogenic pulmonary edema but a unilateral presentation is extremely rare. The differential diagnosis includes excessive vascular filling, infectious pneumonia, gastric fluid aspiration edema, and cardiogenic pulmonary edema. The mechanisms underlying neurogenic pulmonary edema are discussed.

Activated charcoal laryngitis in an intubated patient

Activated charcoal is useful in the management of poisonings, but it is not harmless. We report the case of a patient who developed obstructive laryngitis secondary to aspiration of activated charcoal with a protected airway.

CASE

A 2-year-old girl presented acute mental alteration secondary to presumed poisoning. Mechanical ventilation was initiated, and a single dose of activated charcoal was administered. She had an episode of vomiting during the respiratory weaning. Black-tinted tracheal secretions were suctioned through the tube immediately. Pulmonary auscultation and radiologic examination were normal. When she was extubed, she developed obstructive laryngitis. Fiberbronchoscopy was performed and showed edema and a significant amount of charcoal particles on the epiglottis, arytenoids, and arytenoepiglottic folds. Charcoal particles were removed by bronchoscopy successfully. Later evolution was normal, and no symptoms were present when she was discharged at home.

COMMENTS

Obstructive laryngitis is a new major complication of activated charcoals use in upper airway. It is remarkable that this complication occurred in a protected airway. Charcoal is not an innocuous agent. This case shows that nasogastric administration of activated charcoals presents a significant degree of risk.

North American Summit on Aspiration in the Critically Ill Patient: consensus statement

Aspiration is the leading cause of pneumonia in the intensive care unit and the most serious complication of enteral tube feeding (ETF). Although aspiration is common, the clinical consequences are variable because of differences in nature of the aspirated material and individual host responses. A number of defense mechanisms normally present in the upper aerodigestive system that protect against aspiration become compromised by clinical events that occur frequently in the critical care setting, subjecting the patient to increased risk. The true incidence of aspiration has been difficult to determine in the past because of vague definitions, poor assessment monitors, and varying levels of clinical recognition. Standardization of terminology is an important step in helping to define the problem, design appropriate research studies, and develop strategies to reduce risk. Traditional clinical monitors of glucose oxidase strips and blue food coloring (BFC) should no longer be used. A modified approach to use of gastric residual volumes and identification of clinical factors that predispose to aspiration allow for risk stratification and an algorhythm approach to the management of the critically ill patient on ETF. Although the patient with confirmed aspiration should be monitored for clinical consequences and receive supportive pulmonary care, ETF may be continued when accompanied by appropriate steps to reduce risk of further aspiration. Management strategies for treating aspiration pneumonia are based on degree of diagnostic certainty, time of onset, and host factors.

[Is jejunal feeding efficient in critically ill patients?]

BACKGROUND

The aim of this study is to compare the results of jejunal and gastric nutrition in the ICU.

METHODS

Caloric intake and nutritional complications were recorded for ten days period in patients receiving gastric (n = 21) and jejunal (n = 22) feeding.

RESULTS

Caloric requirements were reached on the 3rd day of nutrition in 86% of jejunal and 28% of gastric feeding patients (p 0.001). In jejunal group, delivered calorie/goal calorie ratio was found 15-20% higher than the gastric group. Serum albumin, triglyceride, cholesterol levels and nitrogen balance did not show significant differences between groups. Vomiting (p 0.01) and colouring of tracheal aspirates (p 0.05) were more frequent in gastric group, however positive tracheal culture frequency did not differ between the groups.

CONCLUSION

It is concluded that higher caloric intakes could be tolerated earlier in patients receiving jejunal feeding.

[A case of carbamate poisoning in which GCMS was useful to identify causal substance and to decide the appropriate treatment]

We often have cases of insecticide poisoning where the patient is unconscious and the causal substances are unknown. We report an 83-year-old unconscious man who had apparently ingested several agricultural chemicals, possibly organophosphate or carbamate. According to his family, there were three kinds of containers of agricultural chemicals with their caps opened around him. When he was transferred to our hospital, he presented hypertension, hypersalivation, and muscle fasciculation. His pupils were markedly miotic. In order to identify the substances ingested we used a gas chromatographymass spectrometer (GCMS) using his gastric content. Within 30 minutes we were able to identify the causal substance as methomyl, one of the popular carbamates, thereby eliminating the need to use pralidoxime (PAM). GCMS makes it possible to identify unknown substances quickly and accurately and is therefore extremely useful in deciding the appropriate treatment.

Pneumonia in pregnancy

Although the advent of broad-spectrum antibiotics has markedly improved the maternal outcomes of pneumonia complicating pregnancy, pneumonia remains a significant condition that may complicate pregnancy. This article has reviewed the inherent physiologic respiratory changes that accompany pregnancy and the common causes of pneumonia in the pregnant woman. The clinical course of bacterial pneumonia seems to be minimally altered by pregnancy, whereas viral pneumonia carries a significantly worse prognosis when encountered during gestation. Prompt diagnosis, the initiation of respiratory support, and appropriate antimicrobial/antiviral therapy are key components of therapy for women in whom pregnancy is complicated by pneumonia. Because preterm labor frequently accompanies pneumonia, women should be monitored closely for the occult onset of preterm labor and appropriate interventions initiated if indicated. Perhaps even more important than interventions to treat acute pneumonia are efforts directed at active immunization or prophylactic therapy to prevent the development of pneumonia in select patient populations. The combination of these efforts is essential to optimize medical care for pregnant women.

Complaints related to respiratory events in anaesthesia and intensive care medicine from 1994 to 1998 in Denmark

BACKGROUND

In Denmark, a National Board of Patients' Complaints (NBPC) was founded in 1988. This study analyses anaesthetic complaints related to adverse respiratory events filed at the NBPC from 1994 to 1998 to point out directions for possible preventive measures.

METHODS

All decisions made by the NBPC from 1994 to 1998 concerning personnel employed in the Danish health care system were scrutinized. Cases related to anaesthesia and intensive care medicine were reviewed. Adverse respiratory events were identified and classified by mechanism of the incident that had caused the complaint. Detailed information on anaesthetic technique, personnel involved, sequence of events, clinical manifestation of injury, and outcome was recorded.

RESULTS

A total of 284 cases was identified. One-fifth (n=60) of the complaints were related to an adverse respiratory event. The overall mortality in these cases was 50% (n=30). In 19 complaints (32%), the treatment was considered substandard.

CONCLUSION

Complaints related to respiratory events reveal that inadequate anaesthetic and intensive care medicine treatment leads to patient damage and death. Preventive strategies should be directed at the development of guidelines for handling the difficult airway, education in the management of the difficult airway, instruction in the correct use of anaesthetic equipment, improvement of interpersonnel communication routines, as well as implementation of simulator training.

Foreign body retrieval in children with respiratory symptoms and no history of aspiration

To asses the role of bronchoscopy and its yield in children with respiratory symptoms and no typical history of radiological evidence of foreign body aspiration (FBA), we reviewed the records of all patients who underwent bronchoscopy at our institution between 1985 and 1995 and had no history of choking, witnessed FBA or clear radiological evidence of FBA (N = 54, age range 4 months to 16 years). These were subdivided into two subgroups, those with positive bronchoscopy, and those with negative bronchoscopy. Respiratory symptoms and their duration, signs and radiological findings did not differ in both subgroups.

Anaesthesia for manipulation of forearm fractures in children: a survey of current practice

Despite recent recommendations that all children presenting for urgent or emergency surgery should be treated as though they have a full stomach, a local audit had shown a wide variation in technique used for anaesthesia in children after trauma. Therefore, a postal questionnaire was sent to 500 anaesthetists regarding their preferred anaesthetic technique for a 6-year-old child requiring manipulation of a forearm fracture. Four clinical situations were presented differing in the timing of surgery in relation to the injury, starvation times before injury and the administration of opioid analgesia. Rapid sequence induction and tracheal intubation was preferred by 83% of all anaesthetists for surgery on the day of injury if the child had eaten 2 h prior to injury and had received opioid analgesia, but the percentage was significantly lower in experienced anaesthetists (P < 0.05) compared with trainees, and was 34.5% overall if surgery was delayed until the following day. Only 19.3% would perform a rapid sequence induction for surgery on the day of injury if the child had not eaten for 6 h before the injury. We conclude that not all anaesthetists believe that rapid sequence induction is necessary for anaesthesia after forearm fractures, despite recent recommendations.

Anatomy of the internal branch of the superior laryngeal nerve

The purpose of this study was to determine the length and distribution of the branches of the internal branch of the superior laryngeal nerve (ibSLN) and describe the initial afferent pathway for the laryngeal cough reflex (LCR). On 25 sides of 19 cadaver specimens, the ibSLN and its branches were dissected from the greater cornu of the hyoid to the mucosa of the larynx and laryngopharynx. The location of these terminal fibers were confirmed by direct observation and fiberoptic laryngoscopy. In 21 specimens, the ibSLN coursed 6.95+/-3.71 mm before piercing the thyrohyoid membrane and splitting into superior, middle, and inferior rami. Four specimens split proximal to the thyrohyoid membrane. The superior ramus distributed to the mucosa of the piriform recess. In this study the large, middle ramus was a new finding and distributed branches to the mucosa of the vestibule of the larynx, specifically the quadrangular membrane. The length of the ibSLN from the greater cornu to the end of the middle ramus at quadrangular membrane was 28.52+/-4.61 mm. The termination of these fibers were confirmed by observation and direct laryngoscopy. The middle ramus probably conveyed the afferent component of the laryngeal cough reflex. The inferior ramus did not distribute to the vestibular mucosa.

Fatal aspiration of sardine fry in a patient with lung cancer

We report a fatal case of death due to unusual aspiration of sardine fry in an elderly Japanese man with lung cancer. The cause of death was sudden respiratory arrest while eating. Autopsy revealed peculiar materials with cell nests and pigmented particles, together with striated muscle and skin, in the ectatic bronchioles of the left lower lobe. Serial histologic sections suggested that the structures observed were the eyeballs of small animals that appeared to have been inhaled. The patient had habitually eaten sardine fry and rice gruel, which were also detected in the gastric contents. Therefore, the eyes were considered to be those of the fry, which is a popular food item in Japan. This was confirmed by histologic examination of fry that were obtained commercially.

Immunopathology of a two-hit murine model of acid aspiration lung injury

In a two-hit model of acid aspiration lung injury, mice were subjected to nonlethal cecal ligation and puncture (CLP). After 48 h, intratracheal (IT) acid was administered, and mice were killed at several time points. Recruitment of neutrophils in response to acid was documented by myeloperoxidase assay and neutrophil counts in bronchoalveolar lavage (BAL) fluid and peaked at 8 h post-IT injection. Albumin in BAL fluid, an indicator of lung injury, also peaked at 8 h. When the contributions of the two hits were compared, neutrophil recruitment and lung injury occurred in response to acid but were not greatly influenced by addition of another hit. Neutrophil sequestration was preceded by elevations in KC and macrophage inflammatory protein-2alpha in plasma and BAL fluid. KC levels in BAL fluid were higher and peaked earlier than macrophage inflammatory protein-2alpha levels. When KC was blocked with specific antiserum, neutrophil recruitment was significantly reduced, whereas albumin in BAL fluid was not affected. In conclusion, murine KC mediated neutrophil recruitment but not lung injury in a two-hit model of aspiration lung injury.

Values and limitations of pharyngolaryngoscopy (transnasal, transoral) in patients with dysphagia

During the last decade, videoendoscopic evaluation of structures and sensorimotor functions of the pharynx and larynx has been established as a valuable tool in the assessment of dysphagia. This method is feasible at a very early stage and in critically ill patients, is not invasive and frequently repeatable. Several authors described the high sensitivity and specificity of this method in detecting the presence of the most important symptoms of swallowing dysfunction: retention, penetration and aspiration. In our study of 39 patients with neurogenic dysphagia, we found high agreement between the results of videoendoscopic and videofluoroscopic examination regarding the registration of the most critical symptom, i.e. aspiration. Moreover, we observed patients who aspirated only their saliva and whose endoscopically verified aspiration problem remained undetected by radiographic examination, probably due to the lower sensory input of saliva as compared to a contrast medium. Since the detection of aspiration of saliva is of high clinical relevance for pulmonary function, the endoscopic examination turned out to be superior, in this particular respect, to the radiographic examination. However, the method fails to provide sufficient information regarding the cause of the observed symptoms or the amount of aspirated material. Six patients in our study exhibited, in addition to the neurological signs, structural changes (diverticula, pouches) or unexpected functional esophageal disturbances (persistent opening of the upper esophageal sphincter, retrograde peristalsis) which could only be detected by radiographic examination. The two methods should therefore be considered complementary.