Ajeet Vinayak

A randomized trial of intermittent lorazepam versus propofol with daily interruption in mechanically ventilated patients.

Objective:To compare duration of mechanical ventilation for patients randomized to receive lorazepam by intermittent bolus administration vs. continuous infusions of propofol using protocols that include scheduled daily interruption of sedation. Design:A randomized open-label trial enrolling patients from October 2001 to March 2004. Setting:Medical intensive care units of two tertiary care medical centers. Patients:Adult patients expected to require mechanical ventilation for >48 hrs and who required ≥10 mg of lorazepam or a continuous infusion of a sedative to achieve adequate sedation. Interventions:Patients were randomized to receive lorazepam by intermittent bolus administration or propofol by continuous infusion to maintain a Ramsay score of 2–3. Sedation was interrupted on a daily basis for both groups. Measurements and Main Results:The primary outcome was median ventilator days. Secondary outcomes included 28-day ventilator-free survival, intensive care unit and hospital length of stay, and hospital mortality. Median ventilator days were significantly lower in the daily interruption propofol group compared with the intermittent bolus lorazepam group (5.8 vs. 8.4, p = .04). The difference was largest for hospital survivors (4.4 vs. 9.0, p = .006). There was a trend toward greater ventilator-free survival for patients in the daily interruption propofol group (median 18.5 days for propofol vs. 10.2 for lorazepam, p = .06). Hospital mortality was not different. Conclusions:For medical patients requiring >48 hrs of mechanical ventilation, sedation with propofol results in significantly fewer ventilator days compared with intermittent lorazepam when sedatives are interrupted daily.

Daily sedative interruption in mechanically ventilated patients at risk for coronary artery disease.

Objectives:To determine the prevalence of myocardial ischemia in mechanically ventilated patients with coronary risk factors and compare periods of sedative interruption vs. sedative infusion. Design:Prospective, blinded observational study. Setting:Medical intensive care unit of tertiary care medical center. Patients:Intubated, mechanically ventilated patients with established coronary artery disease risk factors. Interventions:Continuous three-lead Holter monitors with ST-segment analysis by a blinded cardiologist were used to detect myocardial ischemia. Ischemia was defined as ST-segment elevation or depression of >0.1 mV from baseline. Measurements and Main Results:Comparisons between periods of awakening from sedation vs. sedative infusion were made. Vital signs, catecholamine levels, and time with ischemia detected by Holter monitor during the two periods were compared. Heart rate, mean arterial pressure, rate–pressure product, respiratory rate, and catecholamine levels were all significantly higher during sedative interruption. Eighteen of 74 patients (24%) demonstrated ischemic changes. Patients with myocardial ischemia had a longer intensive care unit length of stay (17.4 ± 17.5 vs. 9.6 ± 6.7 days, p = .04). Despite changes in vital signs and catecholamine levels during sedative interruption, fraction of ischemic time did not differ between the time awake vs. time sedated [median [interquartile range] of 0% [0, 0] compared with 0% [0, 0] while they were sedated [p = .17]). The finding of similar fractions of ischemic time between awake and sedated states persisted with analysis of the subgroup of 18 patients with ischemia. Conclusions:Myocardial ischemia is common in critically ill mechanically ventilated patients with coronary artery disease risk factors. Daily sedative interruption is not associated with an increased occurrence of myocardial ischemia in these patients.

Diagnostic utility of B-type natriuretic peptide in critically ill patients with pulmonary edema: a prospective cohort study

IntroductionDistinguishing pulmonary edema due to acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS) from hydrostatic or cardiogenic edema is challenging in critically ill patients. B-type natriuretic peptide (BNP) can effectively identify congestive heart failure in the emergency room setting but, despite increasing use, its diagnostic utility has not been validated in the intensive care unit (ICU).MethodsWe performed a prospective, blinded cohort study in the medical and surgical ICUs at the University of Chicago Hospitals. Patients were eligible if they were admitted to the ICU with respiratory distress, bilateral pulmonary edema and a central venous catheter suggesting either high-pressure (cardiogenic) or low-pressure (ALI/ARDS) pulmonary edema. BNP levels were measured within 48 hours of ICU admission and development of pulmonary edema and onward up to three consecutive days. All levels were drawn simultaneously with the measurement of right atrial or pulmonary artery wedge pressure. The etiology of pulmonary edema – cardiogenic or ALI/ARDS – was determined by three intensivists blinded to BNP levels.ResultsWe enrolled a total of 54 patients (33 with ALI/ARDS and 21 with cardiogenic edema). BNP levels were lower in patients with ALI/ARDS than in those with cardiogenic edema (496 ± 439 versus 747 ± 476 pg/ml, P = 0.05). At an accepted cutoff of 100 pg/ml, specificity for the diagnosis of ALI/ARDS was high (95.2%) but sensitivity was poor (27.3%). Cutoffs at higher BNP levels improved sensitivity at considerable cost to specificity. Invasive measures of filling pressures correlated poorly with initial BNP levels and subsequent day BNP values fluctuated unpredictably and without correlation with hemodynamic changes and net fluid balance.ConclusionBNP levels drawn within 48 hours of admission to the ICU do not reliably distinguish ALI/ARDS from cardiogenic edema, do not correlate with invasive hemodynamic measurements, and do not track predictably with changes in volume status on consecutive daily measurements.

The relationship between sedative infusion requirements and permissive hypercapnia in critically ill, mechanically ventilated patients.

Objective:Permissive hypercapnia (PH) may result from mechanical ventilation (MV) strategies that intentionally reduce minute ventilation. Sedative doses required to tolerate PH have not been well characterized. With increased attention to lung-protective ventilation, characterization of sedative requirements with PH and determination of sedative dose changes with PH are needed. Design:Retrospective analysis. Setting:Tertiary care university hospital. Patients:We evaluated 124 patients randomized in a previous study to either propofol or midazolam. PH was employed in ten of 60 patients receiving propofol and 13 of 64 patients receiving midazolam. Interventions:We analyzed dosing of propofol and midazolam in patients undergoing PH through a retrospective analysis of an existing database on MV patients. Total sedative (propofol and midazolam) dose was recorded for the first three days of MV. Linear regression analysis (dependent variable: sedative dose) was used to analyze the following independent variables: PH, age, gender, daily sedative interruption, type of respiratory failure, presence of hepatic and/or renal failure, Acute Physiology and Chronic Health Evaluation II score, morphine dose, and Ramsay sedation score. Measurements and Main Results:Propofol dose was higher in PH patients (42.5 ± 16.2 vs. 27.0 ± 15.3; p = .02); Midazolam dose did not differ between PH and non-PH patients (0.05 [0.04, 0.14] vs. 0.05 [0.03, 0.07]; p = .17). By univariate linear regression analysis, propofol dose was significantly dependent on PH, age, type of respiratory failure, morphine dose, and Ramsay score, with PH (regression coefficient, 11.7; 95% confidence interval, 1.2–22.7; p = .03) and age (regression coefficient, −0.3; 95% confidence interval −0.5 to −0.08; p = .005) remaining significant by multivariate linear regression. By univariate linear regression analysis, midazolam dose was dependent on age, morphine dose, and Ramsay score, but not PH; only morphine dose (regression coefficient, 0.44; 95% confidence interval, 0.22–0.67 for a 0.1-unit increase in morphine dose; p < .001) was significant by multivariate linear regression. Conclusions:We conclude that higher doses of propofol but not midazolam are required to sedate patients managed with PH.

Characterization and detection of physiologic lung changes before and after placement of bronchial valves using hyperpolarized helium-3 MR imaging: preliminary study

RATIONALE AND OBJECTIVES The aim of this study was to determine the efficacy of hyperpolarized (3)He (HHe) ventilation and apparent diffusion coefficient (ADC) HHe magnetic resonance imaging (MRI) in detecting changes in lung function and microstructure in emphysematous lung after bronchial valve (BV) placement. MATERIALS AND METHODS One patient diagnosed with emphysema had nine BVs placed in upper lobe bronchi. Imaging was performed before and 6 months after BV placement. Coronal HHe ventilation MRI was used to assess volume changes in the ventilated portions of the lung. Coronal ADC HHe MRI, acquired with b value pairs of 0 and 1.6 s/cm(2) during a second 10-second breath-hold, was used to compute ADC values. RESULTS HHe ventilation MRI revealed decreased ventilation in the treated segments of the upper lobes after BV placement. Increased ventilation in the lower lobes and two untreated segments of the left upper lobes were also observed, with an upward shift of the major fissure of the right lung. Whole-lung mean ADC decreased by 6.3% from baseline, from 0.48 ± 0.196 to 0.45 ± 0.176 cm(2)/s (toward healthier values) following BV placement. CONCLUSIONS HHe ventilation MRI detected an increase in whole-lung volume and an interlobar fissure shift indicative of increased ventilation of lower relative to upper lobes. Reduced ADC values suggest increased ventilation to healthy lower lobes at the expense of more diseased, expanded alveolar spaces in the upper lobes distal to BV placement. These results suggest that this ionizing radiation-free method of examining the lungs may offer functional and structural information useful in BV intervention planning.