Faculty Bibliography

PURPOSE: Monitoring end-expiratory lung volume (EELV) is a valuable tool to optimize respiratory settings that could be of particular importance in mechanically ventilated pediatric patients. We evaluated the feasibility and precision of an intensive care unit (ICU) ventilator with an in-built nitrogen washout/washin technique in mechanically ventilated pediatric patients. METHODS: Duplicate EELV measurements were performed in 30 patients between 5 kg and 43 kg after cardiac surgery (age, median + range: 26, 3-141 months). All measurements were taken during pressure-controlled ventilation at 0 cm H(2)O of positive end-expiratory pressure (PEEP). RESULTS: Linear regression between duplicate measurements was excellent (R (2) = 0.99). Also, there was good agreement between duplicate measurements, bias +/- SD: -0.3% (-1.5 mL) +/- 5.9% (19.2 mL). Mean EELV +/- SD was 19.6 +/- 5.1 mL/kg at 0 cm H(2)O PEEP. EELV correlated with age (p < 0.001, r = 0.92, R (2) = 0.78), body weight (p < 0.001, r = 0.91, R (2) = 0.82) and height (p < 0.001, r = 0.94, R (2) = 0.75). CONCLUSION: This ICU ventilator with an in-built nitrogen washout/washin EELV technique can measure EELV with precision, and can easily be used for mechanically ventilated pediatric patients.

PURPOSE OF REVIEW: Traditionally, the assessment of critical care has focused largely on mortality. However, in the last few years, there is more attention on the quality of survival. Health-related quality of life (HRQOL) is an important issue for both patients and family. The purpose of this review is to describe HRQOL scoring in critically ill patients and to discuss the clinical impact on HRQOL. RECENT FINDINGS: Studies on the effect of critical illness on HRQOL show contradicting results. Several studies found that HRQOL at the time of discharge from hospital was impaired and that a gradual improvement occurred during follow-up, in some cases to preadmission hospital levels. Others show a full recovery to preadmission HRQOL. SUMMARY: In this article, we reviewed the methods and description of measurement instruments used in critically ill patients. The most recently used instruments to measure HRQOL, how to score HRQOL before ICU admission and the impact of critical illness on HRQOL are discussed. Assessment of HRQOL can improve the answers given by critical care physicians and nurses about the prospects of their patients. To get insights in these issues regarding the impact of ICU treatment, we should incorporate not only short-term outcomes, for example length of stay and mortality, but also HRQOL.

OBJECTIVES: To evaluate whether the level and duration of increased blood lactate levels are associated with daily Sequential Organ Failure Assessment (SOFA) scores and organ subscores and to evaluate these associations during the early and late phases of the intensive care unit stay. DESIGN: Retrospective observational study. SETTING: Mixed intensive care unit of a university hospital. PATIENTS: 134 heterogeneous intensive care unit patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We calculated the area under the lactate curve above 2.0 mmol/L (lactateAUC>2). Daily SOFA scores were collected during the first 28 days of intensive care unit stay to calculate initial (day 1), maximal, total and mean scores. Daily lactateAUC>2 values were related to both daily SOFA scores and organ subscores using mixed-model analysis of variance. This was also done separately during the early (<2.75 days) and late (>2.75 days) phase of the intensive care unit stay.Compared with normolactatemic patients (n = 78), all median SOFA variables were higher in patients with hyperlactatemia (n = 56) (initial SOFA: 9 [interquartile range 4-12] vs. 4 [2-7]; maximal SOFA: 10 [5-13] vs. 5 [2-9]; total SOFA: 28 [10-70] vs. 9 [3-41]; mean SOFA: 7 [4-10] vs. 4 [2-6], all p < .001). The overall relationship between daily lactateAUC>2 and daily SOFA was an increase of 0.62 SOFA-points per 1 day.mmol/L of lactateAUC>2 (95% confidence interval, 0.41-0.81, p < .00001). During early intensive care unit stay, the relationship between lactateAUC>2 and SOFA was 1.01 (95% confidence interval, 0.53-1.50, p < .0005), and during late intensive care unit stay, this was reduced to 0.50 (95% confidence interval, 0.28-0.72, p < .0005). Respiratory (0.30, 0.22-0.38, p < .001) and coagulation (0.13, 0.09-0.18, p < .001) subscores were most strongly associated with lactateAUC>2. CONCLUSIONS: Blood lactate levels were strongly related to SOFA scores. This relationship was stronger during the early phase of intensive care unit stay, which provides additional indirect support for early resuscitation to prevent organ failure. The results confirm that hyperlactatemia can be considered as a warning signal for organ failure.

PURPOSE: To study and compare the relationship between end-expiratory lung volume (EELV) and changes in end-expiratory lung impedance (EELI) measured with electrical impedance tomography (EIT) at the basal part of the lung at different PEEP levels in a mixed ICU population. METHODS: End-expiratory lung volume, EELI and tidal impedance variation were determined at four PEEP levels (15-10-5-0 cm H2O) in 25 ventilated ICU patients. The tidal impedance variation and tidal volume at 5 cm H2O PEEP were used to calculate change in impedance per ml; this ratio was then used to calculate change in lung volume from change in EELI. To evaluate repeatability, EELV was measured in quadruplicate in five additional patients. RESULTS: There was a significant but relatively low correlation (r = 0.79; R2 = 0.62) and moderate agreement (bias 194 ml, SD 323 ml) between DeltaEELV and change in lung volume calculated from the DeltaEELI. The ratio of tidal impedance variation and tidal volume differed between patients and also varied at different PEEP levels. Good agreement was found between repeated EELV measurements and washin/washout of a simulated nitrogen washout technique. CONCLUSION: During a PEEP trial, the assumption of a linear relationship between change in global tidal impedance and tidal volume cannot be used to calculate EELV when impedance is measured at only one thoracic level just above the diaphragm.

During recent years increasing attention has been given to the quality of survival in critical care. Health-related quality of life (HRQOL) is an important issue both for patients and their families. Furthermore, admission to the intensive care unit can have adverse psychological effects in critically ill patients. Recent studies conducted in critically ill patients have measured HRQOL. However, usually absent from such reports are evaluations of conceptual issues, addressing factors such as why HRQOL should be measured in critically ill patients, how to define and standardize domains of HRQOL, whether proxies can provide useful information about HRQOL in critically ill patients, whether response shift occurs in critically ill patients, and whether post-traumatic stress disorder (PTSD) occurs in critically ill patients. Some studies reported moderate agreement between patients and their proxies, although lower levels of agreement may be reported for psychosocial or physical functioning. Response shift (adaptation and change in perception) appears to be an important phenomenon and likely to be present, but it is seldom measured when estimating HRQOL in critically ill patients. Furthermore, vigilance for symptoms of PTSD and early interventions to prevent PTSD are needed.

OBJECTIVE: The physical examination of peripheral perfusion based on touching the skin or measuring capillary refill time has been related to the prognosis of patients with circulatory shock. It is unclear, however, whether monitoring peripheral perfusion after initial resuscitation still provides information on morbidity in critically ill patients. Therefore, we investigated whether subjective assessment of peripheral perfusion could help identify critically ill patients with a more severe organ or metabolic dysfunction using the Sequential Organ Failure Assessment (SOFA) score and lactate levels. DESIGN: : Prospective observational study. SETTING: Multidisciplinary intensive care unit in a university hospital. PATIENTS: Fifty consecutive adult patients admitted to the intensive care unit. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were considered to have abnormal peripheral perfusion if the examined extremity had an increase in capillary refill time (>4.5 seconds) or it was cool to the examiner hands. To address reliability of subjective inspection and palpation of peripheral perfusion, we also measured forearm-to-fingertip skin-temperature gradient (Tskin-diff), central-to-toe temperature difference (Tc-toe), and peripheral flow index. The measurements were taken within 24 hours of admission to the intensive care after hemodynamic stability was obtained (mean arterial pressure >65 mm Hg). Changes in SOFA score during the first 48 hours were analyzed (delta-SOFA). Individual SOFA score was significantly higher in patients with abnormal peripheral perfusion than in those with normal peripheral perfusion (9 +/- 3 vs. 7 +/- 2, p < 0.05). Tskin-diff, Tc-toe, and peripheral flow index were congruent with the subjective assessment of peripheral perfusion. The proportion of patients with delta-SOFA score >0 was significantly higher in patients with abnormal peripheral perfusion (77% vs. 23%, p < 0.05). The logistic regression analysis showed that the odds of unfavorable evolution are 7.4 (95% confidence interval 2-19; p < 0.05) times higher for a patient with abnormal peripheral perfusion. The proportion of hyperlactatemia was significantly different between patients with abnormal and normal peripheral perfusion (67% vs. 33%, p < 0.05). The odds of hyperlactatemia by logistic regression analysis are 4.6 (95% confidence interval 1.4-15; p < 0.05) times higher for a patient with abnormal peripheral perfusion. CONCLUSIONS: Subjective assessment of peripheral perfusion with physical examination following initial hemodynamic resuscitation in the first 24 hours of admission could identify hemodynamically stable patients with a more severe organ dysfunction and higher lactate levels. Patients with abnormal peripheral perfusion had significantly higher odds of worsening organ failure than did patients with normal peripheral perfusion following initial resuscitation.

BACKGROUND: Hyperlactatemia and its reduction after admission in the intensive care unit (ICU) have been related to survival. Because it is unknown whether this equally applies to different groups of critically ill patients, we compared the prognostic value of repeated lactate levels (a) in septic patients versus patients with hemorrhage or other conditions generally associated with low-oxygen transport (LT) (b) in hemodynamically stable versus unstable patients. METHODS: In this prospective observational two-center study (n = 394 patients), blood lactate levels at admission to the ICU (Lac(T0)) and the reduction of lactate levels from T = 0 to T = 12 hours (DeltaLac(T0-12)) and from T = 12 to T = 24 hours (DeltaLac(T12-24)), were related to in-hospital mortality. RESULTS: Reduction of lactate was associated with a lower mortality only in the sepsis group (DeltaLac(T0-12): hazard ratio [HR] 0.34, p = 0.004 and DeltaLac(T12-24): HR 0.24, p = 0.003), but not in the LT group (DeltaLac(T0-12); HR 0.78, p = 0.52 and DeltaLac(T12-24); HR 1.30, p = 0.61). The prognostic values of Lac(T0), DeltaLac(T0-12), and DeltaLac(T12-24) were similar in hemodynamically stable and unstable patients (p = 0.43). CONCLUSIONS: Regardless of the hemodynamic status, lactate reduction during the first 24 hours of ICU stay is associated with improved outcome only in septic patients, but not in patients with hemorrhage or other conditions generally associated with LT. We hypothesize that in this particular group a reduction in lactate is not associated with improved outcome due to irreversible damage at ICU admission.

Important ethical aspects apply to the process of obtaining consent in emergency critical care research: the incapacity of almost all patients for giving informed consent and the emergency and life-threatening nature of the conditions involved, resulting in short therapeutic time frames. We argue that deferred proxy consent is the preferable substitute for informed patient consent in emergency critical care research. However, researchers can face two problems when using this consent procedure. First, can proxies give a valid judgment for consent or refusal in the acute phase of the life-threatening illness of their relative, and second, what should researchers do with already obtained data when study procedures are finished (e.g., because the patient has died) before proxies can be informed and consent be sought? We propose approaching the relatives with information about the trial and asking them for consent only if it is ethically valid to do so. The first psychological distress may prohibit a complete understanding of the information, which is necessary for a true and valid informed proxy consent. In addition, we recommend using the study data if study procedures are finished before proxies can be informed and consent be sought, provided sufficient privacy measures have been applied.

OBJECTIVE: Compare duration of mechanical ventilation (MV), weaning time, ICU-LOS (ICU-LOS), efficacy and safety of remifentanil-based regimen with conventional sedation and analgesia. DESIGN: Centre randomised, open-label, crossover, 'real-life' study. SETTING: 15 Dutch hospitals. PATIENTS: Adult medical and post-surgical ICU patients with anticipated short-term (2-3 days) MV. INTERVENTIONS: Patient cohorts were randomised to remifentanil-based regimen (n = 96) with propofol as required, for a maximum of 10 days, or to conventional regimens (n = 109) of propofol, midazolam or lorazepam combined with fentanyl or morphine. MEASUREMENTS AND MAIN RESULTS: Outcomes were weaning time, duration of MV, ICU-LOS, sedation- and analgesia levels, intensivist/ICU nurse satisfaction, adverse events, mean arterial pressure, heart rate. Median duration of ventilation (MV) was 5.1 days with conventional treatment versus 3.9 days with remifentanil (NS). The remifentanil-based regimen reduced median weaning time by 18.9 h (P = 0.0001). Median ICU-LOS was 7.9 days versus 5.9 days, respectively (NS). However, the treatment effects on duration of MV and ICU stay were time-dependent: patients were almost twice as likely to be extubated (P = 0.018) and discharged from the ICU (P = 0.05) on day 1-3. Propofol doses were reduced by 20% (P = 0.05). Remifentanil also improved sedation-agitation scores (P < 0.0001) and intensivist/ICU nurse satisfaction (P < 0.0001). All other outcomes were comparable. CONCLUSIONS: In patients with an expected short-term duration of MV, remifentanil significantly improves sedation and agitation levels and reduces weaning time. This contributes to a shorter duration of MV and ICU-LOS.