Critical Care - Latest Articles

Review of "Neurology Emergencies" by Jonathon A. Edlow and Magdy H. Selim

Rajat Dhar — 2012-05-16T00:00:00Z

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The intravascular volume effect of ringer's lactate is below 20%: a prospective study in humans

Matthias Jacob — 2012-05-16T00:00:00Z

Introduction Isotonic crystalloids play a central role in perioperative fluid management. Isooncotic preparations of colloids (e.g. human albumin or hydroxyethyl starch) remain nearly completely intravascular when infused to compensate for acute blood losses. Recent data were interpreted to indicate a comparable intravascular volume effect for crystalloids, challenging the occasionally suggested advantage of using colloids to treat hypovolemia. General physiological knowledge and clinical experience, however, suggest otherwise.Methods In a prospective study, double-tracer blood volume measurements were performed before and after intended normovolemic hemodilution in ten female adults, simultaneously substituting the three-fold amount of withdrawn blood with ringer's lactate. Any originated deficits were substituted with half the volume of 20% human albumin, followed by a further assessment of blood volume. To assess significance between the measurements, repeated measures analysis of variance (ANOVA) according to Fisher were performed. If significant results were shown, paired t-tests (according to Student) for the singular measurements were taken. P<0.05 was considered to be significant.Results 1,097+/-285 ml of whole blood were withdrawn (641+/-155 ml/m2 body surface area) and simultaneously replaced by 3,430+/-806 ml of ringer's lactate. All patients showed a significant decrease in blood volume after hemodilution (-459+/-185 ml; p<0.05) which did not involve relevant hemodynamical changes, and a significant increase in interstitial water content (+2,157+/-606 ml; p<0.05). The volume effect of ringer's lactate was 17+/-10%. The infusion of 245+/-64 ml of 20% human albumin in this situation restored blood volume back to baseline values, the volume effect being 184+/-63%.Conclusions Substitution of isolated intravascular deficits in cardiopulmonary healthy adults with the 3-fold amount of ringer's lactate impedes maintenance of intravascular normovolemia. Main side effect was an impressive interstitial fluid accumulation, which was partly restored by the intravenous infusion of 20% human albumin. We recommend to substitute the 5-fold amount of crystalloids or to use an isooncotic preparation in the face of acute bleeding in patients where edema prevention might be advantageous.

A pilot prospective study on closed loop controlled ventilation and oxygenation in ventilated children during the weaning phase

Philippe Jouvet — 2012-05-16T00:00:00Z

IntroductionThe present study is a pilot prospective safety evaluation of a new closed loop computerized protocol on ventilation and oxygenation in stable, spontaneously breathing children weighting more than 7kg, during the weaning phase of mechanical ventilation. Methods: Mechanically ventilated children ready to start the weaning process were ventilated for 5 periods of 60 minutes in the following order: Pressure Support Ventilation (PSV), Adaptive Support Ventilation (ASV), ASV plus a ventilation controller (ASV-CO2), ASV-CO2 plus an oxygenation controller (ASV-CO2-O2) and PSV again. Based on breath by breath analysis, the percentage of time with normal ventilation as defined by a respiratory rate (RR) between 10 and 40 breath/min, a tidal volume (VT) > 5 ml/kg of predicted body weight and an end tidal CO2 between 25 and 55 mmHg. The number of manipulations and changes on the ventilator were also recorded. Results: Fifteen children, median aged 45 months, were investigated. No adverse event and no premature protocol termination were reported. ASV-CO2 and ASV-CO2-O2, kept the patients within normal ventilation for respectively 94% [91 - 96] and 94% [87 - 96]) of the time. VT, RR, Peak inspiratory airway pressure (Paw-peak) and minute ventilation were equivalent with all modalities, although there were more automatic setting changes in ASV-CO2 and ASV-CO2-O2. PEEP modifications by ASV-CO2-O2 needs further investigation. Conclusions: Over the short study period and in this specific population, ASV-CO2 and ASV-CO2-O2 were safe and kept the patient with normal ventilation most of the time. Further research is needed, especially for PEEP modifications by ASV-CO2-O2.Trial registration: NCT01095406

Antipsychotic use and diagnosis of delirium in the intensive care unit

Joshua Swan — 2012-05-16T00:00:00Z

IntroductionDelirium is an independent risk factor for prolonged hospital length of stay (LOS) and increased mortality. Several antipsychotics have been studied for the treatment of intensive care unit (ICU) delirium that has lead to a high variability in prescribing patterns for these medications. We hypothesize that in clinical practice the documentation of delirium is lower than the incidence of delirium reported in prospective clinical trials. The objective of this study was to document the incidence of delirium diagnosed in ICU patients and to describe the utilization of antipsychotics in the ICU. Methods: Retrospective observational cohort study conducted at seventy-one United States academic medical centers that reported data to the University HealthSystem Consortium Clinical Database/Resource Manager. Included all patients 18 years of age and older admitted to the hospital between January 1, 2010 and June 30, 2010 with at least one day in the ICU. Results: Delirium was diagnosed in 6% (10,034 of 164,996) of hospitalizations with an ICU admission. Antipsychotics were administered to 11% (17,764 of 164,996) of patients. Of the antipsychotics studied, the most frequently used were haloperidol (62%; n=10,958) and quetiapine (31%; n=5,448). Delirium was associated with increased ICU LOS (5 vs. 3 days, P<0.001) and hospital LOS (11 vs. 6 days, P<0.001), but not in-hospital mortality (8% vs. 9%, P=0.419). Antipsychotic exposure was associated with increased ICU LOS (8 vs. 3 days, P<0.001), hospital LOS (14 vs. 5 days, P<0.001) and mortality (12% vs. 8%, P<0.001). Of patients with antipsychotic exposure in the ICU, absence of a documented mental disorder (32%, n=5,760) was associated with increased ICU LOS (9 vs. 7 days, P<0.001), hospital LOS (16 vs. 13 days, P<0.001) and in-hospital mortality (19% vs. 9%, P<0.001) compared to patients with a documented mental disorder (68%, n=12,004). Conclusions: The incidence of documented delirium in ICU patients is lower than that documented in previous prospective studies with active screening. Antipsychotics are administered to one in every ten ICU patients. When administration occurs in the absence of a documented mental disorder, antipsychotic use is associated with an even higher ICU and hospital LOS, as well as in-hospital mortality.

Early course of microcirculatory perfusion in eye and digestive tract during hypodynamic sepsis

Andrius Pranskunas — 2012-05-15T00:00:00Z

IntroductionThe aim of the study is to evaluate and compare the microcirculatory perfusion during experimental sepsis in different potentially available parts of the body, such as sublingual mucosa, conjunctiva of the eye, mucosa of jejunum and rectum. Methods: Pigs were randomly assigned to sepsis (n=9) and sham (n=4) groups. The sepsis group received a fixed dose of alive Escherichia coli infusion over 1 hour (1.8 * 109 /kg colony-forming units). Animals were observed 5 hours after the start of Escherichia coli infusion. In addition to systemic hemodynamic assessment, we performed conjunctival, sublingual, jejunal and rectal evaluation of microcirculation using Sidestream Dark Field (SDF) videomicroscopy at the same time points: at baseline, 3 and 5 hours after the start of live Escherichia coli infusion. Assessment of microcirculatory parameters of convective oxygen transport (microvascular flow index (MFI) and proportion of perfused vessels (PPV)), and diffusion distance (perfused vessel density (PVD) and total vessel density (TVD)) was done using a semi-quantitative method. Results: Infusion of Escherichia coli resulted in a hypodynamic state of sepsis associated with low cardiac output and increased systemic vascular resistance despite fluid administration. Significant decrease in MFI and PPV of small vessels were observed in sublingual, conjunctival, jejunal and rectal lodges 3 and 5 hours after start of Escherichia coli infusion in comparison to baseline variables. Correlation between sublingual and conjunctival (r=0.80, p=0.036), sublingual and jejunal (r=0.80, p=0.044), sublingual and rectal (r=0.79, p=0.03) MFI was observed 3 hours after onset of sepsis. However, this strong correlation between the sublingual and other regions disappeared 5 hours after the start of Escherichia coli infusion. Overall, the sublingual mucosa exhibited the most pronounced alterations of microcirculatory flow in comparison to conjunctival, jejunal and rectal microvasculature (p<0.05). Conclusions: In this pig model there is a time dependent correlation between sublingual and microvascular beds during the course of hypodynamic state of sepsis.

Insulin Therapy Improves Protein Metabolism in the Critically Ill

Marc Jeschke — 2012-05-14T00:00:00Z

Critical illness, trauma and burns are associated with profound metabolic abnormalities, of which protein catabolism, hyperglycemia and insulin resistance are hallmarks of these conditions. Increased protein breakdown and loss results in muscle wasting, weakness and diminished functioning. Interestingly, hyperglycemia and insulin resistance augment catabolic responses. Insulin, which is routinely administered to critically ill patients to prevent excessive hyperglycemia, also stimulates protein synthesis and prevents whole-body protein loss. The present commentary highlights the results of a recent study published in Critical Care and discusses whether moderate insulin therapy is equally as beneficial as conventional insulin therapy in preventing protein catabolism and loss.

Evaluation of a new pocket echoscopic device for focused-cardiac ultrasonography in emergency setting

Matthieu Biais — 2012-05-14T00:00:00Z

IntroductionIn the emergency setting, focused cardiac ultrasound has become a fundamental tool for diagnostic, initiate emergency treatment and triage decisions. A new ultra-miniaturized pocket ultrasound device (PUD) may be suited in this specific setting. Therefore, we aimed to compare the diagnostic ability of an ultra-miniaturized ultrasound device (VscanTM, GE Healthcare, Wauwatosa, WI) and of a conventional high-quality echocardiography system (Vivid S5TM, GE Healthcare) for a cardiac focused ultrasonography in patients admitted in emergency department. Methods: During 4 months, patients admitted to our emergency department and requiring transthoracic echocardiography (TTE) were included in this single-center, prospective and observational study. Patients underwent TTE using pocket ultrasound device (PUD) and conventional echocardiography system. Each examination was performed independently by a physician experienced in echocardiography, unaware of the results found by the alternative device. During the focused cardiac echocardiography, the following parameters were assessed: global cardiac systolic function, identification of ventricular enlargement or hypertrophy, assessment for pericardial effusion and estimation of the size and the respiratory changes of the inferior vena cava (IVC) diameter. Results: One hundred and fifty one (151) patients were analysed. Using the tested PUD, the image quality was sufficient to perform focused cardiac ultrasonography in all patients. Examination using PUD adequately qualified with a very good agreement global left ventricular systolic dysfunction (kappa=0.87; 95%CI: 0.76-0.97), severe right ventricular dilation (kappa=0.87; 95%CI: 0.71-1.00), inferior vena cava dilation (kappa=0.90; 95%CI: 0.80-1.00), respiratory induced variations in inferior vena cava size in spontaneous breathing (kappa=0.84; 95%CI: 0.71-0.98), pericardial effusion (kappa=0.75; 95%CI: 0.55-0.95) and compressive pericardial effusion (kappa=1.00; 95%CI: 1.00-1.00). Conclusions: In emergency setting, this new ultraportable echoscope was reliable for the real-time detection of focused cardiac abnormalities.

Transthoracic Echocardiography with Doppler Tissue Imaging predicts weaning failure from mechanical ventilation: evolution of the left ventricle relaxation rate during a spontaneous breathing trial is the key factor in weaning outcome

Sebastien Moschietto — 2012-05-14T00:00:00Z

IntroductionThere is growing evidence to suggest that transthoracic echocardiography (TTE) should be used to identify the cardiac origin of respiratory weaning failure. The aims of our study were: firstly, to evaluate the ability of transthoracic echocardiography, with mitral Doppler inflow E velocity to annular tissue Doppler Ea wave velocity (E/Ea) ratio measurement, to predict weaning failure from mechanical ventilation in patients, including those with atrial fibrillation; and secondly, to determine whether the depressed left ejection fraction and/or diastolic dysfunction participate in weaning outcome. Methods: The sample included patients on mechanical ventilation for over 48 hours. A complete echocardiography was performed just before the spontaneous breathing trial (SBT) and 10 minutes after starting the SBT. Systolic dysfunction was defined by a left ventricle ejection fraction under 50% and relaxation impairment by a protodiastolic annulus mitral velocity Ea under or equal to 8 cm/second. Results: 68 patients were included. 20 failed the weaning process and the other 48 patients succeeded. Before the SBT, the E/Ea ratio was higher in the failed group than in the successful group. The E/Ea measured during the SBT was also higher in the failed group. The cut-off value, obtained from receiver operating characteristics (ROC) curve analysis, to predict weaning failure gave an E/Ea ratio during the SBT of 14.5 with a sensitivity of 75% and a specificity of 95.8%. The left ventricular ejection fraction did not differ between the two groups whereas Ea was lower in the failed group. Ea increased during SBT in the successful group while no change occurred in the failed group. Conclusions: Measurement of the E/Ea ratio with TTE could predict weaning failure. Diastolic dysfunction with relaxation impairment is strongly associated with weaning failure. Moreover the impossibility of enhancing the left ventricle relaxation rate during the SBT seems to be the key factor of weaning failure. In contrast, the systolic dysfunction was not associated with weaning outcome.

Gender differences in psychological morbidity and treatment in intensive care survivors - a cohort study

Anna Schandl — 2012-05-14T00:00:00Z

IntroductionMany hospitals have initiated follow-up to facilitate rehabilitation after critical illness and intensive care, although the efficacy of such an intervention is uncertain. Studies in trauma research indicate significant differences in psychological reactions to traumatic events between men and women. Our aim was, in a quasi-experimental design, to compare psychological morbidity and treatment effects between men and women enrolled in a multidisciplinary intensive care unit (ICU) follow-up programme (follow-up group) and ICU patients not offered such follow-up (control group). Methods: Men and women treated > 4 days in the ICU in 2006, before ICU follow-up started, were compared with men and women treated in 2007 and 2008, when all patients with ICU stay > 4 days were offered ICU follow-up at 3, 6 and 12 months post-ICU. Fourteen months after ICU discharge, psychological problems were measured with Impact of Event Scale (IES) for posttraumatic stress and Hospital Anxiety and Depression Scale (HADS) for anxiety and depression. Results: Women with no follow-up reported significantly higher IES scores than men. Women in the follow-up group reported significantly lower IES scores compared to women in the control group, both in crude analysis and after adjusting for significant confounders/predictors (age, ICU length of stay and previous psychological problems). Furthermore, the 75th percentile for IES and HADS-Depression scores (high scores and degree of symptoms of psychological problems) in women in the follow-up group was lower than in those without follow-up (IES: -17.4 p, p<.01, HADS-depression: -4.9 p, p<.05). For men, no significant differences were found between the no follow-up and the follow-up group. Conclusion: Psychological problems after critical illness and intensive care appear to be more common in women than in men. A multidisciplinary ICU follow-up may reduce the incidence of long-term symptoms of posttraumatic stress and depression for women.

Comparison of accuracy of optic nerve ultrasound for the detection of intracranial hypertension in the setting of acutely fluctuating vs stable ICP: post-hoc analysis of data from a prospective, blinded single center study

Venkatakrishna Rajajee — 2012-05-11T00:00:00Z

IntroductionOptic nerve sheath diameter (ONSD) measurement with bedside ultrasound has been shown in many studies to accurately detect high intracranial pressure (ICP). The accuracy of point-in-time ONSD measurement in the presence of ongoing fluctuation of ICP between high and normal is not known. Recent laboratory investigation suggests that reversal of optic nerve sheath distension may be impaired following bouts of intracranial hypertension. Our objective was to compare the accuracy of ONSD measurement in the setting of fluctuating versus stable ICP. Methods: Retrospective analysis of data from prospective study comparing ONSD to invasive ICP. Patients with invasive ICP monitors in the ICU underwent ONSD measurement with simultaneous blinded recording of ICP from the invasive monitor. 3 measurements were made in each eye. Significant acute ICP fluctuation (SAIF) was defined in 2 different ways; as the presence of ICP both above and below 20mmHg within a cluster of 6 measurements (Definition 1) and as magnitude of fluctuation >10mmHg within the cluster (Definition 2). The accuracy of point-in-time ONSD measurements for the detection of concurrent ICP>20mmHg within clusters fulfilling a specific definition of SAIF was compared to the accuracy of ONSD measurements within clusters not fulfilling the particular definition by comparison of independent receiver operating characteristic (ROC) curves. Results: 613 concurrent ONSD-ICP measurements in 109 clusters were made in 73 patients. 23 (21%) clusters fulfilled SAIF Definition 1 and 17 (16%) SAIF Definition 2. For Definition 1, the difference in the area under the curve (AUC) of ROC curves for groups with and without fluctuation was 0.10 (P=0.0001). There was a fall in the specificity from 98%(95%CI 96-99%) to 74%(63-83%) and in the positive predictive value from 89%(80-95%) to 76%(66-84%) with fluctuation. For Definition 2 also there was a significant difference between the AUC of ROC curves of groups with fluctuation-magnitude >10mmHg and those with fluctuation-magnitude 5-10mmHg (0.06, P=0.04) as well as <5mmHg (0.07, P=0.01). Conclusions: Specificity and PPV of ONSD for ICP>20mmHg are substantially less in patients demonstrating acute fluctuation of ICP between high and normal. This may be because of delayed reversal of nerve sheath distension.