Faculty Bibliography

Near infrared spectroscopy (NIRS) is a non-invasive technique that allows determination of tissue oxygenation based on spectro-photometric quantitation of oxy- and deoxyhemoglobin within a tissue. This technique has gained acceptance as a tool to monitor peripheral tissue perfusion in critically ill patient. NIRS principle is based on the use of near-infrared electromagnetic waves for qualitative and quantitative assessments of molecular factors related to tissue oxygenation. Although this technique can be apllied in any tissue, it is primarily used for monitoring peripheral oxygenation in the muscle. Parameters that are determined using NIRS can be either directly calculated or can be derived from physiological interventions, such as arterial and venous occlusions methods. Information regarding muscle oxygen saturation, muscle oxygen consumption and regional blood flow can therefore be obtained. Clinical applications of NIRS include peripheral oxygenation monitoring during resuscitation of trauma and septic shock as well as the assessment of regional microcirculatory disorders. This review provides a brief discussion of NIRS basic principles and main clinical uses of this technique, with a specific focus on studies that assess the usefulness of NIRS in intensive care and emergency patients.

INTRODUCTION: Computed tomography of the lung has shown that ventilation shifts from dependent to nondependent lung regions. In this study, we investigated whether, at the bedside, electrical impedance tomography (EIT) at the cranial and caudal thoracic levels can be used to visualize changes in ventilation distribution during a decremental positive end-expiratory pressure (PEEP) trial and the relation of these changes to global compliance in mechanically ventilated patients. METHODS: Ventilation distribution was calculated on the basis of EIT results from 12 mechanically ventilated patients after cardiac surgery at a cardiothoracic ICU. Measurements were taken at four PEEP levels (15, 10, 5 and 0 cm H2O) at both the cranial and caudal lung levels, which were divided into four ventral-to-dorsal regions. Regional compliance was calculated using impedance and driving pressure data. RESULTS: We found that tidal impedance variation divided by tidal volume significantly decreased on caudal EIT slices, whereas this measurement increased on the cranial EIT slices. The dorsal-to-ventral impedance distribution, expressed according to the center of gravity index, decreased during the decremental PEEP trial at both EIT levels. Optimal regional compliance differed at different PEEP levels: 10 and 5 cm H2O at the cranial level and 15 and 10 cm H2O at the caudal level for the dependent and nondependent lung regions, respectively. CONCLUSIONS: At the bedside, EIT measured at two thoracic levels showed different behavior between the caudal and cranial lung levels during a decremental PEEP trial. These results indicate that there is probably no single optimal PEEP level for all lung regions.

BACKGROUND: Ventilator-associated pneumonia (VAP) occurs in more than half of mechanically ventilated patients with Guillain-Barre syndrome (GBS) and is associated with prolonged mechanical ventilation (MV). We investigated the impact of selective decontamination of the digestive tract (SDD), an intervention that reduces hospital acquired infections in ICU patients, on duration of MV in GBS and neurological outcome at 6 months. METHODS: We performed a retrospective study in mechanically ventilated GBS patients in the Netherlands. We compared patients treated with and without SDD. Main outcomes were duration of MV and the ability to walk independently at 6 months. Statistical comparison was done with logistic and ordinal regression analyses. RESULTS: We included 124 GBS patients on MV at 2 weeks after first symptoms (SDD, n = 54 and non-SDD, n = 70). The median duration of MV without SDD was 42 days (interquartile range, IQR 25-77 days) versus 29 days with SDD (IQR 17-45 days). Median duration of MV for all included patients was 35 days. The adjusted odds ratio (OR) for duration of MV > 35 days in the SDD versus the non-SDD cohort was 0.37 (95% CI 0.17-0.77). SDD did not affect neurological recovery after 6 months from first symptoms. VAP occurred in 12% (95% CI 2-22%) in the SDD cohort and in 47% (95% CI 35-59%) in the non-SDD cohort. CONCLUSIONS: SDD in mechanically ventilated GBS patients reduced the time on the ventilator, probably by preventing VAP, but did not affect neurological recovery after 6 months.

OBJECTIVE: We conducted this observational study to investigate tissue oxygen saturation during a vascular occlusion test in relationship with the condition of peripheral circulation and outcome in critically ill patients. DESIGN: Prospective observational study. SETTING: Multidisciplinary intensive care unit in a university hospital. PATIENTS: Seventy-three critically ill adult patients admitted to the intensive care unit. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were followed every 24 hrs until day 3 after intensive care admission. Near-infrared spectroscopy was used to measure thenar tissue oxygen saturation, tissue oxygen saturation deoxygenation rate, and tissue oxygen saturation recovery rate after the vascular occlusion test. Measurements included heart rate, mean arterial pressure, forearm-to-fingertip skin-temperature gradient, and physical examination of peripheral perfusion with capillary refill time. Patients were stratified according to the condition of peripheral circulation (abnormal: forearm-to-fingertip skin-temperature gradient >/=4 and capillary refill time >4.5 secs). The outcome was defined based on the daily Sequential Organ Failure Assessment score and blood lactate levels. Upon intensive care unit admission, 35 (47.9%) patients had abnormal peripheral perfusion (forearm-to-fingertip skin-temperature gradient >4 or capillary refill time >4.5 secs). With the exception of the tissue oxygen saturation deoxygenation rate, tissue oxygen saturation baseline and tissue oxygen saturation recovery rate were statistically lower in patients who exhibited abnormal peripheral perfusion than in those with normal peripheral perfusion: 72 +/- 9 vs. 81 +/- 9; p = .001 and 1.9 +/- 0.7 vs. 3.2 +/- 0.9; p = .001, respectively. When a mixed-model analysis was performed over time for estimate (s) calculation, adjusted to the condition of disease, we did not find a significant clinical effect between vascular occlusion test-derived tissue oxygen saturation measurements (as response variables) and mean systemic hemodynamic variables (as independent variables): tissue oxygen saturation vs. heart rate: s (95% confidence interval) = 0.007 (-0.08; 0.09); tissue oxygen saturation vs. mean arterial pressure: s (95% confidence interval) = -0.02 (-0.12; 0.08); tissue oxygen saturation deoxygenation rate vs. heart rate: s (95% confidence interval) = 0.002 (-0.0004; 0.006); tissue oxygen saturation deoxygenation rate vs. mean arterial pressure: s (95% confidence interval) - 0.0007 (-0.003; 0.004); tissue oxygen saturation recovery rate vs. heart rate: s (95% confidence interval) = -0.009 (-0.02; -0.0015); tissue oxygen saturation recovery rate vs. mean arterial pressure: s (95% confidence interval) = 0.01 (0.002; 0.018). However, there was a strong association between tissue oxygen saturation baseline and tissue oxygen saturation recovery rate with abnormal peripheral perfusion: tissue oxygen saturation vs. abnormal peripheral perfusion: s (95% confidence interval) = -10.1 (-13.9; -6.2); tissue oxygen saturation recovery rate vs. abnormal peripheral perfusion: s (95% confidence interval) =-10.1 (-13.9; -6.2); tissue oxygen saturation recovery rate vs. abnormal peripheral perfusion: s (95% confidence interval) = -1.1 (-1.4; -0.81). Poor outcome was more closely related to abnormalities in peripheral perfusion than to tissue oxygen saturation-derived parameters. CONCLUSIONS: We found that the condition of peripheral circulation in critically ill patients strongly influences tissue oxygen saturation resting values and the tissue oxygen saturation reoxygenation rate but not the tissue oxygen saturation deoxygenation rate. In addition, changes in near-infrared spectroscopy-derived variables were independent of condition of disease and were not accompanied by any major differences in systemic hemodynamic variables.

The brain dead patient is the ideal multiorgan donor. Conversely, brain death (BD) is an undesirable outcome of critical care medicine. Conditions that can lead to the state of BD are limited. An analysis showed that a (aneurysmal) subarachnoid hemorrhage, traumatic brain injury, or intracerebral hemorrhage in 83% precede the state of BD. Because of better prevention and treatment options, we should anticipate on an inescapable and desirable decline of BD. In this article, we offer arguments for this statement and discuss alternatives to maintain a necessary level of donor organs for transplantation.

RATIONALE: Measured at intensive care unit admission (ICU), the predictive value of neutrophil gelatinase-associated lipocalin (NGAL) for severe acute kidney injury (AKI) is unclear. OBJECTIVES: To assess the ability of plasma and urine NGAL to predict severe AKI in adult critically ill patients. METHODS: Prospective-cohort study consisting of 632 consecutive patients. MEASUREMENTS AND MAIN RESULTS: Samples were analyzed by Triage immunoassay for NGAL expression. The primary outcome measure was occurrence of AKI based on Risk-Injury-Failure (RIFLE) classification during the first week of ICU stay. A total of 171 (27%) patients developed AKI. Of these 67, 48, and 56 were classified as RIFLE R, I, and F, respectively. Plasma and urine NGAL values at ICU admission were significantly related to AKI severity. The areas under the receiver operating characteristic curves for plasma and urine NGAL were for RIFLE R (0.77 +/- 0.05 and 0.80 +/- 0.04, respectively), RIFLE I (0.80 +/- 0.06 and 0.85 +/- 0.04, respectively), and RIFLE F (0.86 +/- 0.06 and 0.88 +/- 0.04, respectively) and comparable with those of admission estimated glomerular filtration rate (eGFR) (0.84 +/- 0.04, 0.87 +/- 0.04, and 0.92 +/- 0.04, respectively). Plasma and urine NGAL significantly contributed to the accuracy of the "most efficient clinical model" with the best four variables including eGFR, improving the area under the curve for RIFLE F prediction to 0.96 +/- 0.02 and 0.95 +/- 0.01. Serial NGAL measurements did not provide additional information for the prediction of RIFLE F. CONCLUSIONS: NGAL measured at ICU admission predicts the development of severe AKI similarly to serum creatinine-derived eGFR. However, NGAL adds significant accuracy to this prediction in combination with eGFR alone or with other clinical parameters and has an interesting predictive value in patients with normal serum creatinine.

PURPOSE: It is desirable to identify a potential organ donor (POD) as early as possible to achieve a donor conversion rate (DCR) as high as possible which is defined as the actual number of organ donors divided by the number of patients who are regarded as a potential organ donor. The DCR is calculated with different assessment tools to identify a POD. Obviously, with different assessment tools, one may calculate different DCRs, which make comparison difficult. Our aim was to determine which assessment tool can be used for a realistic estimation of a POD pool and how they compare to each other with regard to DCR. METHODS: Retrospective chart review of patients diagnosed with a subarachnoid haemorrhage, traumatic brain injury or intracerebral haemorrhage. We applied three different assessment tools on this cohort of patients. RESULTS: We identified a cohort of 564 patients diagnosed with a subarachnoid haemorrhage, traumatic brain injury or intracerebral haemorrhage of whom 179/564 (31.7%) died. After applying the three different assessment tools the number of patients, before exclusion of medical reasons or age, was 76 for the IBD-FOUR definition, 104 patients for the IBD-GCS definition and 107 patients based on the OPTN definition of imminent neurological death. We noted the highest DCR (36.5%) in the IBD-FOUR definition. CONCLUSION: The definition of imminent brain death based on the FOUR-score is the most practical tool to identify patients with a realistic chance to become brain dead and therefore to identify the patients most likely to become POD.

BACKGROUND: We studied the frequency of withdrawal of mechanical ventilation (MV) and/or vasoactive agents (VAs), the time until death, and dosages of opioids and sedatives in a Dutch academic intensive care unit (ICU), and compared these practices with international observations in this field. METHODS: Retrospective data were collected from the electronic and paper files of all patients who died after withdrawal of treatment in a Dutch ICU between October 2006 and February 2007. RESULTS: In this period, 471 patients were admitted to the ICU, of whom 88 died (18%). In 60 of these patients (68%), MV and/or VAs were withdrawn. This group represented 13% of the total ICU population. Of the 60 patients for whom MV and/or VAs were withdrawn, 54 (90%) died after withdrawal of MV (with or without VAs). Six (10%) died after withdrawal of VAs only, 33 (55%) after withdrawal of MV in combination with VAs, and 21 (35%) after withdrawal of MV only. Death occurred after withdrawal of MV in combination with VAs after a median of 30 minutes (interquartile range [IQR], 10-195 minutes). When only MV was discontinued, the median time until death was 50 minutes (IQR, 15-530 minutes). When only VAs were withdrawn, patients died after a median of 45 minutes (IQR, 20-715 minutes). Ten patients (17%) did not receive opioids or sedatives in their last hours. Fifty patients received opioids in their last hours. Fentanyl, with a median dosage at time of death of 100 mug/h, was the most frequently used opioid. Forty (80%) of the 50 patients mentioned above received some kind of sedative until death. In the MV withdrawal group, 34 of the 54 patients (63%) received sedatives in the last hours of their lives: 16 (27%) received midazolam (median, 10 mg/h), 12 (22%) propofol (median, 160 mg/h), and 6 (11%) lorazepam (2.0 mg/h). Sedatives were administered to all patients in whom only VAs were withdrawn. CONCLUSIONS: Dutch patients who die in the ICU, or die after discharge from the ICU, die after MV and/or VAs are withdrawn. When treatments are withdrawn, death follows within 1 hour in most patients, which is a reflection of the severity of illnesses. At least 80% of patients receive opioids, and 67% receive sedatives until death. Fentanyl is the most used opioid, whereas midazolam is the most used sedative. Dosages of opioids and sedatives did not significantly exceed the ranges described as usual in the international literature.

BACKGROUND: First we aimed to evaluate the ability of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin-C (CyC) in plasma and urine to discriminate between sustained, transient and absent acute kidney injury (AKI), and second to evaluate their predictive performance for sustained AKI in adult intensive care unit (ICU) patients. METHODS: A prospective cohort study of 700 patients was studied. Sample collection was performed over 8 time points starting on admission. RESULTS: After exclusion 510 patients remained for the analysis. All biomarkers showed significant differentiation between sustained and no AKI at all time points (p