Comparison of multiple definitions for ventilator-associated pneumonia in patients requiring mechanical ventilation for non-pulmonary conditions: preliminary data from PULMIVAP, an Italian multi-centre cohort study.

OBJECTIVES: To compare intensivist-diagnosed ventilator-associated pneumonia (iVAP) with four established definitions, assessing their agreement in detecting new episodes. METHODS: A multi-centric prospective study on pulmonary microbiota was carried out in patients requiring mechanical ventilation (MV). Data collected were used to compare hypothetical VAP onset according to iVAP with the study consensus criteria, the European Centre for Disease Control and Prevention definition, and two versions of the latter adjusted for leukocyte count and fever. RESULTS: In our cohort of 186 adult patients, iVAPs were 36.6% (68/186, 95% confidence interval 30.0-44.0%), with an incidence rate of 4.64/100 patient-MV-days, and median MV-day at diagnosis of 6. Forty-seven percent of patients (87/186) were identified as VAP by at least one criterion, with a median MV-day at diagnosis of 5. Agreement between intensivist judgement (iVAP/no-iVAP) and the criteria was highest for the study consensus criteria (50/87, 57.4%), but still one-third of iVAP were not identified and 9% of patients were identified as VAP contrary to intensivist diagnosis. VAP proportion differed between criteria (25.2-30.1%). CONCLUSIONS: Caution is needed when evaluating studies describing VAP incidence. Pre-agreed criteria and definitions that capture VAP's evolving nature provide greater consistency, but new clinically driven definitions are needed to align surveillance and diagnostic criteria with clinical practice.

Ultrasound-tagged near-infrared spectroscopy does not disclose absent cerebral circulation in brain-dead adults.

BACKGROUND: Near-infrared spectroscopy, a non-invasive technique for monitoring cerebral oxygenation, is widely used, but its accuracy is questioned because of the possibility of extra-cranial contamination. Ultrasound-tagged near-infrared spectroscopy (UT-NIRS) has been proposed as an improvement over previous methods. We investigated UT-NIRS in healthy volunteers and in brain-dead patients. METHODS: We studied 20 healthy volunteers and 20 brain-dead patients with two UT-NIRS devices, CerOx™ and c-FLOW™ (Ornim Medical, Kfar Saba, Israel), which measure cerebral flow index (CFI), a parameter related to changes in cerebral blood flow (CBF). Monitoring started after the patients had been declared brain dead for a median of 34 (range: 11-300) min. In 11 cases, we obtained further demonstration of absent CBF. RESULTS: In healthy volunteers, CFI was markedly different in the two hemispheres in the same subject, with wide variability amongst subjects. In brain-dead patients (median age: 64 yr old, 45% female; 20% traumatic brain injury, 40% subarachnoid haemorrhage, and 40% intracranial haemorrhage), the median (inter-quartile range) CFI was 41 (36-47), significantly higher than in volunteers (33; 27-36). CONCLUSIONS: In brain-dead patients, where CBF is absent, the UT-NIRS findings can indicate an apparently perfused brain. This might reflect an insufficient separation of signals from extra-cranial structures from a genuine appraisal of cerebral perfusion. For non-invasive assessment of CBF-related parameters, the near-infrared spectroscopy still needs substantial improvement.

Heart-fatty acid-binding and tau proteins relate to brain injury severity and long-term outcome in subarachnoid haemorrhage patients.

BACKGROUND: Vasospasm and other secondary neurological insults may follow subarachnoid haemorrhage (SAH). Biomarkers have the potential to stratify patient risk and perhaps serve as an early warning sign of delayed ischaemic injury. METHODS: Serial cerebrospinal fluid (CSF) samples were collected from 38 consecutive patients with aneurysmal SAH admitted to the neurosurgical intensive care unit. We measured heart-fatty acid-binding protein (H-FABP) and tau protein (τ) levels in the CSF to evaluate their association with brain damage, and their potential as predictors of the long-term outcome. H-FABP and τ were analysed in relation to acute clinical status, assessed by the World Federation of Neurological Surgeons (WFNS) scale, radiological findings, clinical vasospasm, and 6-month outcome. RESULTS: H-FABP and τ increased after SAH. H-FABP and τ were higher in patients in poor clinical status on admission (WFNS 4-5) compared with milder patients (WFNS 1-3). Elevated H-FABP and τ levels were also observed in patients with early cerebral ischaemia, defined as a CT scan hypodense lesion visible within the first 3 days after SAH. After the acute phase, H-FABP, and τ showed a delayed increase with the occurrence of clinical vasospasm. Finally, patients with the unfavourable outcome (death, vegetative state, or severe disability) had higher peak levels of both proteins compared with patients with good recovery or moderate disability. CONCLUSIONS: H-FABP and τ show promise as biomarkers of brain injury after SAH. They may help to identify the occurrence of vasospasm and predict the long-term outcome.

Neurofilament light chain levels in ventricular cerebrospinal fluid after acute aneurysmal subarachnoid haemorrhage.

PURPOSE: The contribution of axonal injury to brain damage after aneurysmal subarachnoid haemorrhage (aSAH) is unknown. Neurofilament light chain (NF-L), a component of the axonal cytoskeleton, has been shown to be elevated in the cerebrospinal fluid of patients with many types of axonal injury. We hypothesised that patients with aSAH would have elevated cerebrospinal fluid (CSF) NF-L levels and sought to explore the clinical correlates of CSF NF-L dynamics. METHODS: Serial ventricular CSF (vCSF) samples were collected from 35 patients with aSAH for up to 15 days. vCSF NF-L measurements were determined by enzyme-linked immunosorbent assay. NF-L levels were analysed in relation to acute clinical status, radiological findings and 6-month outcomes. RESULTS: vCSF NF-L concentrations were elevated in all patients with aSAH. Patients with early cerebral ischaemia (ECI), defined as a CT hypodense lesion visible within the first 3 days, had higher acute vCSF NF-L levels than patients without ECI. These elevated NF-L levels were similar in patients with ECI associated with intracranial haemorrhage and ECI associated with surgical/endovascular complications. vCSF NF-L levels did not differ as a function of acute clinical status, clinical vasospasm, delayed cerebral ischaemia or 6-month Glasgow Outcome Scale. CONCLUSIONS: Elevated vCSF NF-L levels may in part reflect increased injury to axons associated with ECI. However, our results suggest that axonal injury after aSAH as reflected by release of NF-L into the CSF may not play a major role in either secondary adverse events or long-term clinical outcomes.

Increased levels of CSF heart-type fatty acid-binding protein and tau protein after aneurysmal subarachnoid hemorrhage.

BACKGROUND: Heart-type Fatty Acid-Binding Protein (H-FABP) and tau protein (tau) have been shown to be novel biomarkers associated with brain injury and, therefore, they could represent a useful diagnostic tool in patients with subarachnoid hemorrhage (SAH). The goal of this study was to measure H-FABP and tau in cerebrospinal fluid (CSF) following SAH to test the hypothesis that a relationship exists between SAH severity and H-FABP/tau values. METHODS: Twenty-seven consecutive SAH patients admitted to our ICU were studied. Serial CSF samples were obtained in every patient starting on the day of SAH and daily for up to 2 weeks post-SAH. H-FABP/tau levels were measured by enzyme-linked immunosorbent assay. RESULTS: Patients with severe SAH showed significantly higher peak levels of H-FABP and tau compared to mild-SAH patients (FABP: p = 0.02; tay: p = 0.002). In addition the peak concentrations of H-FABP and tau in CSF from SAH patients correlated significantly with Glasgow Coma Scale motor score (H-FABP: Spearman r = -0.52, p = 0.006; tau: Spearman r = -0.63, p = 0.0004). Based on outcome at discharge from the hospital, patients were categorized into survivors and non-survivors. Peak concentrations of both proteins in the non-survivors group were significantly higher than in the survivors. CONCLUSIONS: H-FABP and tau CSF levels are proportional to SAH severity and may be novel biomarkers that can be used to predict the severity of outcome following clinical SAH.