R. E. Sarginson

Microbial Gut Overgrowth Guarantees Increased Spontaneous Mutation Leading to Polyclonality and Antibiotic Resistance in the Critically Ill

Polyclonality is defined as the occurrence of different genotypes of a bacterial species. We are of the opinion that these different clones originate within the patient. When infections and outbreaks occur, the terms of polyclonal infections and polyclonal outbreaks have been used, respectively. The origin of polyclonality has never been reported, although some authors suggest the acquisition of different clones from different animate and inanimate sources. We think that the gut of the critically ill patient with microbial overgrowth is the ideal site for the de-novo development of new clones, following increased spontaneous mutation.

Prevention of ventilator-associated pneumonia by selective decontamination of the digestive tract

To the Editors: We read with interest the review entitled “Evidence on measures for the prevention of ventilator-associated pneumonia” by Lorente et al. 1. We enjoyed the paper as it is comprehensive and based on an appropriate design. In particular, we welcome the authors’ acknowledgement of the proven clinical benefits of selective decontamination of the digestive tract (SDD). The authors give four explanations why SDD is not yet widely used, but are unable to make a definitive …

Diastolic dysfunction and N-terminal pro-brain natriuretic peptide in children with meningococcal sepsis.

Dear Editor, Myocardial systolic dysfunction is an important problem in children with severe meningococcal disease (MCD) but diastolic function has not been assessed. N-Terminal pro-B-type natriuretic peptide (NT-ProBNP) is released in response to myocyte stretch and is elevated in children with sepsis [1, 2]. We conducted a prospective observational study of children with confirmed MCD between January 2007 and April 2008. Plasma samples were taken at admission and sequentially for estimation of NT-ProBNP. Transthoracic echocardiography utilising tissue Doppler imaging (TDI) was performed whenever blood sampling was carried out. To account for children presenting to PICU at different points in their illness, multiple linear regression analysis was used to assess the independent predictive value of the NT-ProBNP measurement for E/Ea. Twenty ventilated patients, with a median age of 2.5 (IQR 0.96– 4.4) years, were recruited and all survived. Seven had abnormal diastolic function at admission with low Ea velocity. These seven children had an E/Ea ratio above 10, indicating an abnormally raised LV filling pressure. A significant difference between the admission and pre-extubation values was found for the Ea velocity and the E/Ea ratio (p \ 0.05). Median admission NT-proBNP levels in the MCD patients were 2,783.2 fmol/ml (IQR 2,163.7– 5,657.5), compared with 381.5 fmol/ ml (IQR 184.2–511.4) in ten agematched children with a febrile viral illness. There was a negative correlation between admission NTProBNP and Ea value (r = -0.57, p \ 0.05). This was no longer significant 24 h after admission. Multiple linear regression analysis was used to assess the independent ability of NT-ProBNP to predict the E/Ea ratio after adjustment for the duration of illness, including duration of rash prior to PICU admission and duration of ventilation prior to admission to PICU. The results show that NT-ProBNP levels predict LV filling pressure, as assessed by the E/ Ea ratio, irrespective of the stage of illness at the time of admission with an increase of 1,000 fmol/ml in admission BNP increasing the E/Ea ratio by around 1.4 (Table 1). These are the first data to demonstrate diastolic dysfunction and elevated levels of NT-ProBNP in children with severe MCD. We also show an association between the two although the relationship is not necessarily causative. Resuscitation volume could cause elevated filling pressures and hence BNP release, although Roch et al. [3] found that fluid loading was not a significant predictor of a high NT-ProBNP level in a multivariate analysis. An increase in systemic vascular resistance by inotropic support may also contribute to diastolic dysfunction. The method of resuscitation for children not responding to conventional treatment may need to be reconsidered in light of these findings. Agents such as milrinone or levosimendan could reduce excess LV filling pressures in such circumstances by means of their vasodilatory effects [4, 5]. Fried and colleagues compared NT-Pro BNP levels in children with sepsis and those with a febrile viral illness. Higher levels were found in those with sepsis [1], raising the possibility that NT-ProBNP is released as a result of an inflammatory process alone. Larger studies in a similar population are needed to confirm these findings.

The Usefulness of Surveillance Cultures: a Prospective Cohort Study on the ICU

Surveillance samples are defined as samples obtained from body sites where potentially pathogenic micro-organisms (PPM) are carried, i.e., the digestive tract comprising the oropharyngeal cavity and rectum [1]. Surveillance swabs are to be distinguished from surface and diagnostic samples. Surface samples are swabs from the skin such as axilla, groin and umbilicus, and from the nose, eye and ear. They do not belong to a surveillance sampling protocol, because positive surface swabs merely reflect oropharyngeal and rectal carrier state. Diagnostic samples are samples from internal organs that are normally sterile, such as lower airways, blood, bladder, and skin lesions. They are only taken on clinical indication. The endpoint of diagnostic samples is clinical, as they aim to microbiologically prove a clinical diagnosis of inflammation, both generalized and/or local.

The Gut in the Critically Ill: Central Organ in Abnormal Microbiological Carriage, Infections, Systemic Inflammation, Microcirculatory Failure, and MODS

The gut consists of different components, including microcirculation, mucosa, immune system, enteric nervous system, commensal microflora, and–during critical illness–acquired microorganisms. All these components interact with each other during critical illness, and all elements may become disturbed as a consequence of disease as well as its treatment. The importance of the close relation between abnormal microbial carriage, immunity, and intestinal microcirculation in the critically ill is addressed in this chapter. Therapeutic interventions within this context are reviewed.