Lower tidal volume strategy (≈3 ml/kg) combined with extracorporeal CO2 removal versus ‘conventional’ protective ventilation (6 ml/kg) in severe ARDS

Background

Acute respiratory distress syndrome is characterized by damage to the lung caused by various insults, including ventilation itself, and tidal hyperinflation can lead to ventilator induced lung injury (VILI). We investigated the effects of a low tidal volume (V _T) strategy (V _T ≈ 3 ml/kg/predicted body weight [PBW]) using pumpless extracorporeal lung assist in established ARDS.

Methods

Seventy-nine patients were enrolled after a ‘stabilization period’ (24 h with optimized therapy and high PEEP). They were randomly assigned to receive a low V _T ventilation (≈3 ml/kg) combined with extracorporeal CO₂ elimination, or to a ARDSNet strategy (≈6 ml/kg) without the extracorporeal device. The primary outcome was the 28-days and 60-days ventilator-free days (VFD). Secondary outcome parameters were respiratory mechanics, gas exchange, analgesic/sedation use, complications and hospital mortality.

Results

Ventilation with very low V _T’s was easy to implement with extracorporeal CO₂-removal. VFD’s within 60 days were not different between the study group (33.2 ± 20) and the control group (29.2 ± 21, p = 0.469), but in more hypoxemic patients (PaO₂/FIO₂ ≤150) a post hoc analysis demonstrated significant improved VFD-60 in study patients (40.9 ± 12.8) compared to control (28.2 ± 16.4, p = 0.033). The mortality rate was low (16.5 %) and did not differ between groups.

Conclusions

The use of very low V _T combined with extracorporeal CO₂ removal has the potential to further reduce VILI compared with a ‘normal’ lung protective management. Whether this strategy will improve survival in ARDS patients remains to be determined (Clinical trials NCT 00538928).     

The volume of returned red blood cells in a large blood salvage program: where does it all go? (CME)

BACKGROUND: Intraoperative blood salvage is the process whereby shed red blood cells (RBCs) are collected and returned to the patient. We analyzed the trends in the volume of returned RBCs by our blood salvage program across a 12‐hospital regional health care system over a 5‐year period. STUDY DESIGN AND METHODS: All quality control, RBC recovery, and patient demographic data relating to blood salvage are stored in a large database covering these 12 hospitals. Cases in which blood salvage was performed over a 5‐year period were stratified based on patient demographics, hospital, type of surgery, and volume of RBCs recovered. RESULTS: There were 19,867 surgeries performed during the study period in which blood salvage was used. The median volume of blood returned to each patient was 405 mL (25th‐75th percentile, 135‐750 mL). Defining the volume of an RBC unit as 200 mL, this represented a median of 1.1 RBC unit equivalents (25th‐75th percentile, 0.37‐2.1 units) returned to each patient. For the majority of patients, not more than 1 RBC unit equivalent was recovered. Overall, the ratio of cases where at least 1 RBC unit equivalent was recovered to cases where less than 1 RBC equivalent was recovered was 2.5:1; this ratio varied considerably between surgical procedures. CONCLUSIONS: Although overall the mean volumes of RBCs returned to the patients by intraoperative blood salvage were high, the actual volumes returned depended on the case mix. There appears to be an opportunity to use blood salvage more selectively to improve efficiency.     

Treatment of a coronary bifurcation lesion with drug-coated balloons: lumen enlargement and plaque modification after 6 months

We report a male with a coronary bifurcation lesion in the mid circumflex artery (CX). After predilatation, the lesion was treated with two drug-coated balloons (DCB). Primary success in the posterolateral branch was good; however the CX lesion had a residual stenosis including a non-flow-limiting type A dissection. After 6 months, angiography showed slight lumen enlargement in both branches of the bifurcation. Intravascular ultrasound identified about 35 % atherosclerotic plaque load within the inner area of the bifurcation but more than 50 % concentric atherosclerotic plaque burden in the vessel areas proximal and distal to the DCB-treated area.     

Global cerebral blood flow and CPP after severe head injury: a xenon-CT study

Objective To evaluate the association between global cerebral blood flow and different cerebral perfusion pressure ranges in severe head injury. Design A retrospective study Setting Neurosurgical and trauma patients in an intensive care unit in a regional hospital. Patients and participants Out of a series of 237 consecutive patients with severe head injuries (GCS ≤ 8), 162 were submitted to ICP monitoring and 89 of them underwent 180 xenon-CT studies and cerebral perfusion pressure (CPP) measurement. The xenon-CT studies did not include any unsalvageable patients nor any mistakenly diagnosed as severe on entry. Interventions None. Measurements and results Most (95.6%) of xenon-CT studies were obtained with CPP values within the 50–90 mmHg range. Perfusion data were grouped according to CPP values: (1) below 50 mmHg, (2) 50–60 mmHg, (3) 60–70 mmHg, (4) above 70 mmHg. Global cerebral blood flow did not differ among the groups (p = 0.49). No differences in physiological variables were found among the CPP groups, except for intracranial pressure, higher in the group with CPP below 50 mmHg, and mean arterial pressure, higher in the CPP above 70 mmHg group (p < 0.0001). No differences were found for cerebral metabolic rate of oxygen and lactate. Conclusions There was little correlation between CPP values and global cerebral blood flow levels in our selected patients, probably because pressure autoregulation was preserved. Global metabolism measurements were constant within the groups, suggesting that in patients with controlled physiological variables an interplay between cerebral blood flow and metabolism might be more relevant than the relationship between CPP and cerebral blood flow.     

New method for quantifying and correcting underestimated cardiac Doppler blood flow velocities: in vitro and in vivo studies

This study was aimed to quantify the underestimation of cardiac Doppler measurements and to explore a method for correction. A dual pulse wave (PW)/Doppler tissue imaging (DTI) mode echocardiographic technique was used in the in vitro and in vivo studies. In the in vitro experiment, we have demonstrated how cardiac valvular motion might interfere with blood velocity estimation using conventional Doppler. When examining the participants, we observed that adding valvular annulus velocity to determine the relative velocity between blood and valvular annulus would result in an increment of 9.3 ± 1.3 cm/s and 6.3 ± 0.9 cm/s for aortic and pulmonary blood flow, 12.8 ± 1.9 cm/s and 8.9 ± 1.4 cm/s for mitral E and A wave, 12.9 ± 1.8 cm/s and 10.2 ± 2.4 cm/s for tricuspid E and A wave. The underestimations of the Doppler measurements markedly influence the hemodynamic parameters commonly used in the clinical practices and researches. This study provides a quantitative method for the correction and would make the Doppler measurement accurate.     

Postoperative volume balance: does stroke volume increase in Trendelenburg's position?

In healthy humans, stroke volume (SV) and cardiac output (CO) do not increase with expansion of the central blood volume by head-down tilt or administration of fluid. Here, we exposed 85 patients to Trendelenburg's position about one hour after surgery while cardiovascular variables were determined non-invasively by Modelflow. In Trendelenburg's position, SV (83 ± 19 versus 89 ± 20 ml) and CO (6·2 ± 1·8 versus 6·8 ± 1·8 l/min; both P<0·05) increased, while heart rate (75 ± 15 versus 76 ± 14 b min⁻¹) and mean arterial pressure were unaffected (84 ± 15 versus 84 ± 16 mmHg). For the 33 patients (39%) with a > 10% increase in SV (from 78 ± 16 to 90 ± 17 ml) corresponding to an increase in CO from 5·9 ± 1·5 to 6·9 ± 1·6 l min⁻¹ (P<0·05) when tilted head-down, administration of 250 ml Ringer's lactate solution increased SV (to 88 ± 18 ml) and CO (to 6·8 ± 1·7 l min⁻¹). In conclusion, determination of SV and/or CO in Trendelenburg's position can be used to evaluate whether a patient is in need of IV fluid as here exemplified after surgery.     

Changes in red blood cell volume during transition of heart failure status: a reflection of cellular hydration status?

This study examined how changes in heart failure (HF) status induce changes in the index of erythrocyte hydration based on mean red blood cell volume (MCV). Data from 47 HF patients (32% men; 78.2?±?9.7?years) that experienced worsening and recovery of HF were analysed. Blood tests included measurements of MCV, albumin, serum solutes and b-type natriuretic peptide (BNP). Among a total of 47 worsening HF events, changes in MCV were positively correlated with changes in body weight (r?=?0.31, p?=?.034), serum sodium (r?=?0.417, p?=?.0036), and chloride (r?=?0.457, p?=?.0012), and negatively correlated with changes in blood urea nitrogen (r=??0.389, p?=?.0069) and creatinine (r=??0.494, p?=?.0004). At recovery from worsening of HF by conventional diuretic therapy, change in MCV was positively correlated with the change in body weight (r?=?0.457, p?=?.0012), serum sodium (r?=?0.466, p?=?.001) and chloride (r?=?0.484, p?=?.0006). Multivariate regression analysis demonstrated an independent association between the increase in serum chloride and MCV from stability to worsening of HF (odds ratio [OR] 6.02, 95% confidence interval [CI] 1.09–33.2, p?=?.039) and the increase or absence of change in serum chloride concentration and preserved MCV after decongestion (OR 11.5, 95% CI 1.53–85.9, p?=?.017). In conclusion, this study demonstrates that the changes in MCV under transition in HF status do not reflect a change that occurs in parallel with changes in HF-related markers, such as body weight and serum BNP level, but is independently associated with a change in the serum chloride concentration. Whether changes in MCV actually reflect the bodily cellular hydration status warrants further research.     

Does methylene blue administration to septic shock patients affect vascular permeability and blood volume?

OBJECTIVE: To assess the effects of the inhibition of guanylate cyclase, an enzyme involved in sepsis-related vascular and myocardial dysfunctions, on hemodynamic variables including blood volume and pulmonary vascular permeability during septic shock. DESIGN: Prospective, open study with repeated measurements. SETTING: A medicosurgical intensive care unit of a university hospital. PATIENTS: Fifteen patients with septic shock associated with persisting hypotension despite conventional treatment including fluid loading, vasopressors, and inotropes. INTERVENTIONS: A fiberoptic catheter was inserted for the determination of blood and extravascular volumes by the thermal-dye double indicator technique, using indocyanine green (COLD system). A bolus dose of methylene blue (3 mg/kg) was infused intravenously over 10 mins. COLD-derived variables were recorded before methylene blue and 20 mins, 1 hr, and 2 hrs after the end of methylene blue infusion. MEASUREMENTS AND MAIN RESULTS: Standard hemodynamic and oxygen-derived variables; total, intrathoracic, systolic, and diastolic cardiac blood volumes; extravascular lung water; plasma osmolarity; and lactate and protein concentrations were recorded. Mean arterial and pulmonary artery pressures, systemic and pulmonary vascular resistances, and left ventricular stroke work index increased, and blood lactate transiently decreased after methylene blue (p <.05). The other variables recorded were unchanged during the 2-hr period following methylene blue infusion. CONCLUSIONS: This study confirmed the acute vasoconstrictive and positive inotropic effects of methylene blue during septic shock. These effects were not associated with changes in blood volume, myocardial diastolic function, or pulmonary vascular permeability assessed by extravascular lung water.     

Effect of body mass index and total blood volume on serum cotinine levels among cigarette smokers: NHANES 1999–2008

IntroductionBody mass index (BMI) and total blood volume are not always considered as variables that affect serum cotinine concentrations.MethodWe used data from the National Health and Nutrition Examination Survey (NHANES) for the years 1999–2008 and fitted regression models for smokers. In addition to traditionally used covariates like age, race, gender, and average number of cigarettes smoked daily, we used BMI and total blood volume (TBV) as continuous variables to evaluate the impact of these variables on serum cotinine levels.ResultsAdjusted serum cotinine levels increased statistically significantly with increase in age (p < 0.001). Serum cotinine levels increased statistically significantly (p < 0.001) with average number of cigarettes smoked daily. Levels of adjusted serum concentrations from high to low by race/ethnicity were: non-Hispanic blacks, non-Hispanic whites, other race/ethnicity, and Mexican-Americans; and all differences were statistically significant.A model of serum cotinine including BMI without TBV found BMI to be a significant predictor (p < 0.001) and similarly a model including TBV without BMI found TBV to be a significant predictor (p < 0.001). When BMI and TBV were both included in the model, the significance of BMI changed markedly (p = 0.93) with substantive changes in the BMI coefficient and the significance of TBV changed also (p = 0.024) with small change in the TBV coefficient.DiscussionTBV and BMI are significant predictors of serum cotinine concentrations. TBV or BMI, but not both, should be included in predictive models of serum cotinine concentrations.