Anesthesia Review: Blasting the Boards.

No abstract available

http://ift.tt/2ndmKOs

Higher Fresh Gas Flow Rates Decrease Tidal Volume During Pressure Control Ventilation.

BACKGROUND: We observed that increasing fresh gas flow (FGF) decreased exhaled tidal volume (VT) during pressure control ventilation (PCV). A literature search produced no such description whereby unintended VT changes occur with FGF changes during PCV. METHODS: To model an infant's lungs, 1 lung of a mechanical lung model (Dual Adult TTL 1600; Michigan Instruments, Inc, Grand Rapids, MI) was set at a compliance of 0.0068 L/cm H2O. An Rp50 resistor (27.2 cm H2O/L/s at 15 L/min) simulated normal bronchial resistance. The simulated lung was connected to a pediatric breathing circuit via a 3.5-mm cuffed endotracheal tube. A ventilator with PCV capability (Model 7900; Aestiva, GE Healthcare, Madison, WI) measured exhaled VT, and a flow monitor (NICO; Respironics, Murraysville, PA) measured peak inspiratory flow, positive end-expiratory pressure (PEEP), and peak inspiratory pressure. In PCV mode, exhaled VT displayed by the ventilator at FGF rates of 1, 6, 10, and 15 L/min was manually recorded across multiple ventilator settings. This protocol was repeated for the Avance CS2 anesthesia machine (GE Healthcare). RESULTS: For the Aestiva, higher FGF rates in PCV mode decreased exhaled VT. Exhaled VT for FGFs of 1, 6, 10, and 15 L/min were on average 48, 34.9, 16.5, and 10 mL, respectively, at ventilator settings of inspiratory pressure of 10 cm H2O, PEEP of 0 cm H2O, and respiratory rate of 20 breaths/min. This is a decrease by up to 27%, 65.6%, and 79.2% when FGFs of 6, 10, and 15 L/min are compared with a FGF of 1 L/min, respectively. In the GE Avance CS2 at the same ventilator settings, VT for FGF rates of 1, 6, 10, and 15 L/min were on average 46, 43, 40.4, and 39.7 mL, respectively. The FGF effect on VT was not as pronounced with the GE Avance CS2 as with the GE Aestiva. CONCLUSIONS: FGF has a significant effect on VT during PCV in the Aestiva bellows ventilator, suggesting caution when changing FGF during PCV in infants. Our hypothesis is that at higher FGF rates, an inadvertent PEEP is developed by the flow resistance of the ventilator relief valve that is not recognized by the ventilator. In turn, less change in pressure is needed to reach the set inspiratory pressure, resulting in lower VT delivery at higher FGF rates. This underappreciated FGF-VT interaction during PCV with a bellows ventilator may be clinically significant in pediatric patients; prospective data collection in patients is needed for further evaluation. (C) 2017 International Anesthesia Research Society

http://ift.tt/2njhWbH

Massive Transfusion in Cardiac Surgery: The Impact of Blood Component Ratios on Clinical Outcomes and Survival.

BACKGROUND: Cardiac surgery is the most common setting for massive transfusion in medically advanced countries. Studies of massive transfusion after injury suggest that the ratios of administered plasma and platelets (PLT) to red blood cells (RBCs) affect mortality. Data from the Red Cell Storage Duration Study (RECESS), a large randomized trial of the effect of RBC storage duration in patients undergoing complex cardiac, were analyzed retrospectively to investigate the association between blood component ratios used in massively transfused patients and subsequent clinical outcomes. METHODS: Massive transfusion was defined as those who had >=6 RBC units or >=8 total blood components. For plasma, high ratio was defined as >=1 plasma unit:1 RBC unit. For PLT transfusion, high ratio was defined as >=0.2 PLT doses:1 RBC unit; PLT dose was defined as 1 apheresis PLT or 5 whole blood PLT equivalents. The clinical outcomes analyzed were mortality and the change in the Multiple Organ Dysfunction Score ([DELTA]MODS) comparing the preoperative score with the highest composite score through the earliest of death, discharge, or day 7. Outcomes were compared between patients transfused with high and low ratios. Linear and Cox regression were used to explore relationships between predictors and continuous outcomes and time to event outcomes. RESULTS: A total of 324 subjects met the definition of massive transfusion. In those receiving high plasma:RBC ratio, the mean (SE) 7- and 28-day [DELTA]MODS was 1.24 (0.45) and 1.26 (0.56) points lower, (P = .007 and P = .024), respectively, than in patients receiving lower ratios. In patients receiving high PLT:RBC ratio, the mean (SE) 7- and 28-day [DELTA]MODS were 1.55 (0.53) and 1.49 (0.65) points lower (P = .004 and P = .022), respectively. Subjects who received low-ratio plasma:RBC transfusion had excess 7-day mortality compared with those who received high ratio (7.2% vs 1.7%, respectively, P = .0318), which remained significant at 28 days (P = .035). The ratio of PLT:RBCs was not associated with differences in mortality. CONCLUSIONS: This analysis found that in complex cardiac surgery patients who received massive transfusion, there was an association between the composition of blood products used and clinical outcomes. Specifically, there was less organ dysfunction in those who received high-ratio transfusions (plasma:RBCs and PLT:RBCs), and lower mortality in those who received high-ratio plasma:RBC transfusions. (C) 2017 International Anesthesia Research Society

http://ift.tt/2ndDUeG

Inhaled Remimazolam Potentiates Inhaled Remifentanil in Rodents.

BACKGROUND: Remimazolam is an ester-based short-acting benzodiazepine currently in clinical trials for IV administration. This study explored the feasibility of delivering remimazolam alone and as an adjunct to remifentanil via inhalation in rodent models. METHODS: Mice were exposed to remimazolam via inhalation; sedation was assessed using time to movement outside a set perimeter. Rats were also exposed to remimazolam aerosol alone and in combination with inhaled remifentanil, and analgesia was quantified by using a tail flick meter. Pulmonary injury was assessed in mice using mechanics measurements. RESULTS: Mice showed significantly increased time to movement outside a set perimeter after 5-minute exposure to increasing concentrations (10-25 mg/mL solutions) of inhaled remimazolam aerosols. Differences in mean (95% confidence interval) time to movement from pretest baseline group (0.05 [0.01-0.09] minutes) were 11 (4-18), 15 (5-26), 30 (19-41), and 109 (103-115) minutes after exposure to remimazolam aerosol of 10, 15, 20, and 25 mg/mL, respectively (P = .007 - P

http://ift.tt/2njdw4N

Video-Based Physiologic Monitoring During an Acute Hypoxic Challenge: Heart Rate, Respiratory Rate, and Oxygen Saturation.

BACKGROUND: The physiologic information contained in the video photoplethysmogram is well documented. However, extracting this information during challenging conditions requires new analysis techniques to capture and process the video image streams to extract clinically useful physiologic parameters. We hypothesized that heart rate, respiratory rate, and oxygen saturation trending can be evaluated accurately from video information during acute hypoxia. METHOD: Video footage was acquired from multiple desaturation episodes during a porcine model of acute hypoxia using a standard visible light camera. A novel in-house algorithm was used to extract photoplethysmographic cardiac pulse and respiratory information from the video image streams and process it to extract a continuously reported video-based heart rate (HRvid), respiratory rate (RRvid), and oxygen saturation (SvidO2). This information was then compared with HR and oxygen saturation references from commercial pulse oximetry and the known rate of respiration from the ventilator. RESULTS: Eighty-eight minutes of data were acquired during 16 hypoxic episodes in 8 animals. A linear mixed-effects regression showed excellent responses relative to a nonhypoxic reference signal with slopes of 0.976 (95% confidence interval [CI], 0.973-0.979) for HRvid; 1.135 (95% CI, 1.101-1.168) for RRvid, and 0.913 (95% CI, 0.905-0.920) for video-based oxygen saturation. These results were obtained while maintaining continuous uninterrupted vital sign monitoring for the entire study period. CONCLUSIONS: Video-based monitoring of HR, RR, and oxygen saturation may be performed with reasonable accuracy during acute hypoxic conditions in an anesthetized porcine hypoxia model using standard visible light camera equipment. However, the study was conducted during relatively low motion. A better understanding of the effect of motion and the effect of ambient light on the video photoplethysmogram may help refine this monitoring technology for use in the clinical environment. This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (C) 2017 International Anesthesia Research Society

http://ift.tt/2ndtI5Q

The Effect of Sedation on Cortical Activation: A Randomized Study Comparing the Effects of Sedation With Midazolam, Propofol, and Dexmedetomidine on Auditory Processing.

BACKGROUND: Every day, millions of people undergo surgical procedures facilitated by anesthesia. Yet, there is no clinically accepted measure to predict the effects of sedation or anesthesia on the central nervous system. Auditory brain activation may provide an objective and quantifiable method to measure of the effects of sedation on neuronal processing. METHODS: This is a randomized clinical trial. Forty-eight healthy volunteers were randomly assigned to receive 1 of 3 sedative drugs (midazolam [n = 11], propofol [n = 12], or dexmedetomidine [n = 12]) at a concentration adjusted to achieve mild sedation by self-rating, or to a no-drug control group (n = 13). Participants underwent functional magnetic resonance imaging while listening to music in a 5-minute block design experiment. We tested the hypothesis that mild sedation changes the magnitude or extent of cortical activation of an auditory stimulus. RESULTS: We observed a significant reduction in auditory activation in both the dexmedetomidine (P = .001) and midazolam (P = .029) but not the propofol group (P = .619) when compared with saline control. CONCLUSIONS: Our findings indicate that, compared with saline control, there is a significant reduction of brain activation in the auditory cortex in response to midazolam and dexmedetomidine but not propofol when given at mildly sedative doses. This method serves as a novel approach to quantify the effects of sedative agents in an objective fashion. (C) 2017 International Anesthesia Research Society

http://ift.tt/2nj9VUi

Patient Blood Management.

No abstract available

http://ift.tt/2ndwFTU