Simultaneous tracheal and oesophageal pH monitoring during mechanical ventilation

Twenty-Four-Hour Esophageal pH Measurement in Mechanically Ventilated Children: A Prospective Cohort Study

OBJECTIVES

To assess the prevalence of gastroesophageal reflux in mechanically ventilated children using 24-hour esophageal pH-metry and its role as a risk factor for ventilator-associated pneumonia.

DESIGN

Prospective cohort study.

SETTING

PICU of a tertiary care hospital from North India.

PATIENTS

Mechanically ventilated children 1-15 years old in PICU from July 2015 to June 2017, excluding those receiving acid suppressants, known cases of gastroesophageal reflux disease, having upper gastrointestinal bleed.

INTERVENTION

Demographic details, baseline investigations, diagnosis, treatment details, and Pediatric Risk of Mortality III score were recorded at enrollment. Gastroesophageal reflux was evaluated using 24-hour esophageal pH-metry. Children were followed up for 7 days or 48 hours after extubation for development of ventilator-associated pneumonia using Centers for Disease Control and Prevention criteria. Pathologic acidic gastroesophageal reflux was defined as fall in esophageal pH less than 4 for more than 4% of total time, whereas pathologic alkaline gastroesophageal reflux as rise in esophageal pH greater than 7 for more than 17% of total time.

MEASUREMENTS AND MAIN RESULTS

Sixty-one children (median [interquartile range], age 73 mo [30-132 mo]; 44 boys [72%]) were enrolled. Median Pediatric Risk of Mortality III score was 10.0 (3-16). Median duration of ventilation was 6 days (3-9 d). Pathologic gastroesophageal reflux (acidic or alkaline) was present in 47 children (77%). Twelve children (19.7%) met criteria for pathologic acidic gastroesophageal reflux, whereas 44 children (72.1%) had pathologic alkaline gastroesophageal reflux; nine children (14.7%) had both pathologic acidic and alkaline gastroesophageal reflux. Of the enrolled children, 17 (27.9 %) developed ventilator-associated pneumonia. No patient had both pathologic acidic gastroesophageal reflux and ventilator-associated pneumonia. Of 17 children who developed ventilator-associated pneumonia, 12 (70.5%) had pathologic alkaline gastroesophageal reflux as compared to 32 children (72.7%) among the 44 children who did not develop ventilator-associated pneumonia (p = 0.87).

CONCLUSIONS

The current study shows high incidence of gastroesophageal reflux on 24-hour esophageal pH-metry in mechanically ventilated children with medical diagnoses. The significance of this finding and its impact on ventilator-associated pneumonia and other ventilator-associated events need to be examined in larger studies.

Influenza Hemagglutinin Protein Stability, Activation, and Pandemic Risk

For decades, hemagglutinin (HA) protein structure and its refolding mechanism have served as a paradigm for understanding protein-mediated membrane fusion. HA trimers are in a high-energy state and are functionally activated by low pH. Over the past decade, HA stability (or the pH at which irreversible conformational changes are triggered) has emerged as an important determinant in influenza virus host range, infectivity, transmissibility, and human pandemic potential. Here, we review HA protein structure, assays to measure its stability, measured HA stability values, residues and mutations that regulate its stability, the effect of HA stability on interspecies adaptation and transmissibility, and mechanistic insights into this process. Most importantly, HA stabilization appears to be necessary for adapting emerging influenza viruses to humans.

Laparoscopic Nissen Fundoplication: An Excellent Treatment of GERD-Related Respiratory Symptoms in Children-Results of a Multicentric Study

INTRODUCTION

Respiratory manifestations of gastroesophageal reflux disease (GERD), particularly chronic cough, are being recognized with increased frequency in children. This survey aimed to investigate the efficacy of laparoscopic Nissen fundoplication for treatment of GERD-related respiratory symptoms not responsive to medical therapy in neurological normal children.

MATERIALS AND METHODS

We collected data of children with GERD-related respiratory complaints not responsive to medical therapy who underwent laparoscopic Nissen fundoplication in four European centers of Pediatric Surgery over a 10-year period. We excluded children with neurological impairment.

RESULTS

A total of 220 laparoscopic Nissen procedures were performed in the period 2005-2015. Twenty-four (12 boys and 12 girls, average age 9.5 years) out of the 220 patients (10.9%) presented with chronic cough and other respiratory manifestations, including asthma, reactive airway disease, and recurrent pneumonia. Average operative time was 65 minutes (range 45-100). As for postoperative complications, two tight wraps requiring endoscopic dilatation (IIIb Clavien) and two relapses of GERD for slipped Nissen requiring reoperation (IIIb Clavien) were recorded. None of these complications occurred in the group of patients with GERD-related respiratory symptoms. At follow-up evaluation, respiratory symptoms disappeared with a significant improvement of quality of life scoring (I Grade Visick) in 22/24 patients (91.6%).

CONCLUSION

Our results confirm that GERD should be investigated as one of the possible etiologic factors in any child with persistent respiratory complaints. In patients with symptoms not responsive to medical therapy, laparoscopic Nissen fundoplication is the treatment of choice with a very high success rate (>90% in our series), a very low morbidity, a significant improvement in airway symptoms, and a marked reduction in the need for medications.

Weakly acidic pH reduces inflammatory cytokine expression in airway epithelial cells

Background

Aspiration lung disease (ALD) is a common cause of respiratory morbidity in children and adults with severe neurodisability (sND). Recent studies suggest that chronic microaspiration of gastric contents is associated with mild rather than low, airway acidification. We investigated inflammatory responses to infection by airway epithelial cells (AECs) exposed to weakly acidic media.

Methods

Using pH measurements from children with sND at high risk of ALD as a guide, we incubated AECs in weakly acidic (pH5.5–7.4) media alone; in combination with lipopolysaccharide (LPS); or prior to LPS stimulation at normal pH. Interleukin (IL) -6 and IL-8 expression were measured.

Results

IL-6/8 expression in AECs simultaneously exposed to weakly acidic media and LPS for 4 h was reduced with no effect on cell viability. Pre-incubation of AECs at weakly acidic pH also reduced subsequent LPS-induced cytokine expression. Suppression of inflammation was greatest at lower pHs (pH 5.5–6.0) for prolonged periods (16/24 h), but this also adversely affected cell viability.

Conclusion

AEC inflammatory responses to bacterial stimuli is markedly reduced in a mildly acidic environment.

Death by acid rain: VAP or EXIT?

Ventilator-associated pneumonia (VAP) is a new (nosocomial) lower respiratory tract infection diagnosed in mechanically ventilated patients 48 or more hours after intubation. There is no gold standard for establishing the diagnosis and its pathogenesis is iatrogenic and multifactorial. Gastro-oesophageal reflux is common in mechanically ventilated children, but its role in VAP remains speculative. VAP is associated with increased mortality and morbidity, prolonged duration of ventilation and hospital stay, and escalated costs of hospitalisation. VAP 'bundles' are championed as the antidote.

A new pepsin assay to detect pulmonary aspiration of gastric contents among newly intubated patients

Aspiration of gastric contents by endotracheally intubated patients is associated with significant morbidity and mortality. Previous studies suggest that pepsin in tracheal aspirates may be a valuable marker of occult aspiration. We sought to show the sensitivity and specificity of a new, pepsin-specific assay in humans. A prospective, case-controlled study was conducted with subjects serving as their own controls. After planned endotracheal and nasogastric intubation for elective surgery, 20 participants had tracheal and gastric aspirates withdrawn. A blinded investigator tested samples for the presence of pepsin using the assay. Positive samples were then tested with pepstatin, a specific pepsin inhibitor, to ensure that positive results were due to pepsin. All tracheal aspirates tested negative and all gastric aspirates tested positive for pepsin. Pepstatin halted pepsin activity in all positive samples, ensuring that positive results were due to pepsin. A pepsin-specific assay is extremely reliable for detecting gastric contents in humans.

Exhaled breath condensates: a potential novel technique for detecting aspiration

There is an urgent need for diagnostic procedures that can detect aspiration of oral and gastrointestinal (GI) secretions into the respiratory tract. Current approaches are limited by poor sensitivity and specificity. These techniques include (1) adding indicators to feedings; (2) recovery of lipid-filled macrophages in respiratory secretions; (3) measurement of changes in the pH of the upper GI and respiratory tracts; (4) endoscopic visualization of reflux events; and (5) measurement of increased glucose concentrations in respiratory secretions. Ideally, specific markers from various sites in the oral and GI tracts might be discovered in respiratory secretions, but conventional bronchoalveolar lavage for sampling respiratory secretions is not practical and involves some risk. Noninvasive measurements of indicators in the exhaled breath condensates could be used to detect aspiration, but a number of theoretical and practical aspects of such studies must be considered before this approach can be applied to the problem of aspiration.

Gastroesophageal reflux and tracheal aspiration in the thoracotomy position: should ranitidine premedication be routine?

Aspiration of gastric contents may contribute to pulmonary complications after thoracotomy. The incidence of gastroesophageal reflux (GER) and tracheal acid aspiration in patients undergoing thoracotomy in the lateral position is unknown. Ranitidine premedication reduces gastric volume, increases gastric pH, and may reduce GER. We used continuous intraluminal esophageal and tracheal pH monitoring probes to investigate the effect of ranitidine on the incidence of GER and tracheal aspiration in 80 adult patients undergoing thoracotomy. The study was placebo-controlled, randomized, and double-blinded. Patients at high risk of GER were excluded from the study. The incidence of acid GER in the placebo and ranitidine groups was 28.2% and 2.5%, respectively (P = 0.006). Multiple episodes of GER occurred in some patients in the placebo group only. The total number of episodes of GER in the placebo and ranitidine groups was 16 and 1, respectively (P = 0.002). The incidence of tracheal acid aspiration in the placebo and ranitidine groups was 7.7% and 2.5%, respectively (not significant). Patients undergoing thoracotomy are therefore at high risk of acid GER, which may lead to tracheal acid aspiration in an appreciable proportion. Premedication with ranitidine significantly reduces, but does not eliminate, the incidence of this potentially life-threatening complication.

IMPLICATIONS

Gastroesophageal reflux (GER) and tracheal aspiration of acid may increase morbidity and mortality in patients undergoing thoracotomy. This randomized, double-blinded, placebo-controlled study demonstrates frequent incidences of both acid GER and tracheal acid aspiration during surgery that are significantly reduced by premedication with ranitidine.

Gastroesophageal reflux disease in asthma: effects of medical and surgical antireflux therapy on asthma control

OBJECTIVE

To critique the English-language reports describing the effects of medical and surgical antireflux therapy on respiratory symptoms and function in patients with asthma.

METHODS

The Medline computerized database (1959-1999) was searched, and all publications relating to both asthma and gastroesophageal reflux disease were retrieved.

RESULTS

Seven of nine trials of histamine-receptor antagonists showed a treatment-related improvement in asthma symptoms, with half of the patients benefiting. Only one study identified a beneficial effect on objective measures of pulmonary function. Three of six trials of proton pump inhibitors documented improvement in asthma symptoms with treatment; benefit was seen in 25% of patients. Half of the studies reported improvement in pulmonary function, but the effect occurred in fewer than 15% of patients. In the one study that used optimal antisecretory therapy, asthma symptoms were improved in 67% of patients and pulmonary function was improved in 20%. Combined data from 5 pediatric and 14 adult studies of anti-reflux surgery indicated that almost 90% of children and 70% of adults had improvement in respiratory symptoms, with approximately one third experiencing improvements in objective measures of pulmonary function.

CONCLUSIONS

Fundoplication has been consistently shown to ameliorate reflux-induced asthma; results are superior to the published results of antisecretory therapy. Optimal medical therapy may offer similar results, but large studies providing support for this assertion are lacking.