Efficiency of oxygen delivery through different oxygen entrainment devices during sedation under low oxygen flow rate: a bench study.

Sedative anesthetic procedures outside the operating room may depend on cylinders as oxygen source. Cylinders have limited storage capacity and a low oxygen flow rate improves the durability. We conducted the bench study to evaluate the fraction of inspired oxygen (FiO2) in different oxygen entrainment devices under low oxygen flow rate. The purpose of the bench study was to provide information to choose appropriate oxygen entrainment devices in non-operating room sedative anesthetic procedures. We utilized a manikin head-test lung-ventilator model and evaluated eight oxygen entrainment devices, including four nasal cannulas, two oral bite blocks, and two masks. Two different minute volumes that defined as the normal ventilation and the hypoventilation group were evaluated. Three pneuflow resistors were placed in turn in the mouth represented ratio of the nasal/oral breathing. Each condition was sampled 70 times after a 3 min ventilation period. Most devices had few drop in FiO2 according to the increased oral breathing ratio in normal ventilation. Most devices had obvious drop in FiO2 related to the increased oral breathing ratio in hypoventilation. Oxygen reservoir units had little effect for accumulating oxygen in normal ventilation. In the hypoventilation group, oxygen reservoir units helped oxygen retention in local area and maintained a higher oxygen concentration. There were multiple factors lead to different oxygen fraction that we measured, such as different devices, respiratory patterns, and oxygen reservoir units. The result of our bench study provided some information for anesthesiologist to choose appropriate oxygen entrainment devices in various sedative anesthetic procedures.

A desflurane and fentanyl dosing regimen for wake-up testing during scoliosis surgery: Implications for the time-course of emergence from anesthesia.

BACKGROUND/PURPOSE: The Stagnara wake-up test assesses neurological deficits during scoliosis surgery, and response surface interaction models for opioids and inhaled agents predicts anesthetic drug effects. We hypothesized that there is an optimal desflurane-fentanyl dosing regimen that can provide a faster and more predictable wake-up time, while also ensuring adequate analgesia during wake-up testing. METHODS: Twenty-three American Society of Anesthesiologists Class I-II scoliosis patients who received desflurane-fentanyl anesthetic regimens were enrolled in this posthoc study, and their intraoperative drug administration data were collected retrospectively. Desflurane and fentanyl effect site concentrations were calculated using pharmacokinetic models, and converted to equivalent remifentanil-sevoflurane concentrations. RESULTS: Results were fitted into Greco models for predicting the probability of an Observers Assessment of Alertness/Sedation score of <2. At time of wake-up, the models correctly predicted the probability that patients would respond to voice prompts and prodding was approximately 50%. The probability of pain intensity was distributed between 50% and 95%, indicating a low degree of pain at emergence. When comparing subgroups defined by calculated effect-site fentanyl concentrations, the wake-up time in the intermediate concentration group was significantly shorter than that in the high concentration group (p = 0.024). CONCLUSION: This study provides evidence that desflurane-fentanyl-based anesthesia is conducive to rapid emergence followed by an immediate neurological evaluation. Intermediate fentanyl effect-site concentrations (1-2 ng/mL) at time of wake-up were associated with good balance between rapid emergence and adequate analgesia. Furthermore, we believe that generalizing response surface models to a variety of inhalation agent-opioid combinations using simple relative potency relationships is possible and practical.

Accuracy of CO2 monitoring via nasal cannulas and oral bite blocks during sedation for esophagogastroduodenoscopy.

Esophagogastroduodenoscopy procedures are typically performed under conscious sedation. Drug-induced respiratory depression is a major cause of serious adverse effects during sedation. Capnographic monitoring of respiratory activity improves patient safety during procedural sedation. This bench study compares the performance of the nasal cannulas and oral bite blocks used to monitor exhaled CO2 during sedation. We used a spontaneously breathing mechanical lung to evaluated four CO2 sampling nasal cannulas and three CO2 sampling bite blocks. We placed pneumatic resistors in the mouth of the manikin to simulate different levels of mouth opening. We compared CO2 measurements taken from the sampling device to CO2 measurements taken directly from the trachea. The end tidal CO2 concentration (PETCO2) measured through the bite blocks and nasal cannulas was always lower than the corresponding PETCO2 measured at the trachea. The difference became larger as the amount of oxygen delivered through the devices increased. The difference was larger during normal ventilation than during hypoventilation. The difference became larger as the amount of oral breathing increased. The two nasal cannulas without oral cups failed to provide sufficient CO2 for breath detection when the mouth was fully open and oxygen was delivered at 10 L/min. Our simulation found that respiratory rate can be accurately monitored during the procedure using a CO2 sampling bite block or a nasal cannula with oral cup. The accuracy of PETCO2 measurements depends on the device used, the amount of supplement oxygen, the amount of oral breathing and the patient's minute ventilation.

Response surface model predictions of wake-up time during scoliosis surgery.

BACKGROUND: With the use of previously published data, new sevoflurane-remifentanil interaction models of various degrees of sedation were created and adapted to desflurane-fentanyl by using minimal alveolar concentration and opioid equivalencies. These models were used to predict return of responsiveness in patients undergoing scoliosis surgery during a wake-up test. Our hypothesis was that one of the interaction models would accurately predict return of responsiveness during a wake-up test. METHODS: Three new sevoflurane-remifentanil interaction models were constructed from previous observations in volunteers by using the Observer's Assessment of Alertness/Sedation (OAA/S) scores. These models included predictions of OAA/S<2 (unresponsive), OAA/S< 3, and OAA/S<4 (sedation). Twenty-three patients scheduled for scoliosis surgery received a fentanyl-desflurane anesthetic. With the use of published pharmacokinetic models, predictions of fentanyl and desflurane effect-site concentrations were recorded throughout surgery and converted to equivalent remifentanil and sevoflurane effect-site concentrations. Data were recorded every 10 seconds from the time when desflurane was turned off until 10 minutes after the patients responded by moving their hands and toes. Model predictions were compared with observations with graphical and temporal analyses. RESULTS: The average difference between the time when a patient first responded and the time when the model predicted that there was a 50% probability that the patient would respond were -2.6 ± 3.6 minutes (mean ± SD) for the OAA/S<2 model, 2.8 ± 5.6 minutes for the OAA/S<3 model and 52.6 ± 32.3 minutes for the OAA/S<4 model. CONCLUSIONS: The results confirmed our study hypothesis; a sevoflurane-remifentanil interaction model built from observations in volunteers and adapted to desflurane and fentanyl accurately predicted patient response during a wake-up test. These results were similar to our previous study comparing model predictions and patient observations after a sevoflurane-remifentanil/fentanyl anesthetic. The OAA/S <2 model most accurately predicted the time patients would respond by moving their fingers and toes. This model may help anesthesiologists better predict return of responsiveness during a wake-up test in patients undergoing spine surgery.

Using the entropy of tracheal sounds to detect apnea during sedation in healthy nonobese volunteers.

BACKGROUND: Undetected apnea can lead to severe hypoxia, bradycardia, and cardiac arrest. Tracheal sounds entropy has been proved to be a robust method for estimating respiratory flow, thus maybe a more reliable way to detect obstructive and central apnea during sedation. METHODS: A secondary analysis of a previous pharmacodynamics study was conducted. Twenty volunteers received propofol and remifentinal until they became unresponsive to the insertion of a bougie into the esophagus. Respiratory flow rate and tracheal sounds were recorded using a pneumotachometer and a microphone. The logarithm of the tracheal sound Shannon entropy (Log-E) was calculated to estimate flow rate. An adaptive Log-E threshold was used to distinguish between the presence of normal breath and apnea. Apnea detected from tracheal sounds was compared to the apnea detected from respiratory flow rate. RESULTS: The volunteers stopped breathing for 15 s or longer (apnea) 322 times during the 12.9-h study. Apnea was correctly detected 310 times from both the tracheal sounds and the respiratory flow. Periods of apnea were not detected by the tracheal sounds 12 times. The absence of tracheal sounds was falsely detected as apnea 89 times. Normal breathing was detected correctly 1,196 times. The acoustic method detected obstructive and central apnea in sedated volunteers with 95% sensitivity and 92% specificity. CONCLUSIONS: We found that the entropy of the acoustic signal from a microphone placed over the trachea may reliably provide an early warning of the onset of obstructive and central apnea in volunteers under sedation.

Graphical user interface simplifies infusion pump programming and enhances the ability to detect pump-related faults.

BACKGROUND: Drug administration errors are frequent and are often associated with the misuse of IV infusion pumps. One source of these errors may be the infusion pump's user interface. METHODS: We used failure modes-and-effects analyses to identify programming errors and to guide the design of a new syringe pump user interface. We designed the new user interface to clearly show the pump's operating state simultaneously in more than 1 monitoring location. We evaluated anesthesia residents in laboratory and simulated environments on programming accuracy and error detection between the new user interface and the user interface of a commercially available infusion pump. RESULTS: With the new user interface, we observed the number of programming errors reduced by 81%, the number of keystrokes per task reduced from 9.2 ± 5.0 to 7.5 ± 5.5 (mean ± SD), the time required per task reduced from 18.1 ± 14.1 seconds to 10.9 ± 9.5 seconds and significantly less perceived workload. Residents detected 38 of 70 (54%) of the events with the new user interface and 37 of 70 (53%) with the existing user interface, despite no experience with the new user interface and extensive experience with the existing interface. CONCLUSIONS: The number of programming errors and workload were reduced partly because it took less time and fewer keystrokes to program the pump when using the new user interface. Despite minimal training, residents quickly identified preexisting infusion pump problems with the new user interface. Intuitive and easy-to-program infusion pump interfaces may reduce drug administration errors and infusion pump-related adverse events.

Evaluation of an integrated intensive care unit monitoring display by critical care fellow physicians.

In the past two far-view displays, which showed vital signs, trends, alarms, infusion pump status, and therapy support indicators, were developed and assessed by critical care nurses (Görges et al. in Dimens Crit Care Nurs. 30(4):206-17, 2011). The aim of the current study is to assess the generalizability of these findings to physicians. The first aim is to test whether an integrated far-view display, designed to be readable from 3 to 5 m, enables critical care physicians to more rapidly and accurately (1) recognize a change in patient condition; (2) identify alarms; and (3) identify near-empty infusion pumps, than a traditional patient monitor and infusion pump. A second aim is to test if the new displays reduce the mental workload required for this decision making. Fifteen critical care fellow physicians (median age of 34 years, with 2-8 years of ICU experience) were asked to use the three displays to compare the data from two patients and decide which patient required their attention first. Each physician made 60 decisions: 20 with each of the two far-view displays and 20 decisions with a standard patient monitor next to an infusion pump. A 41 and 26 % improvement in decision accuracy was observed with the bar and clock far-view displays, respectively. Specifically, the identification of near empty infusion pumps, a task normally performed by nurses, and patients with a single alarm were better with the new displays. Using the bar display physicians made their decision 12 % faster than when using the control display, a median improvement of 2.1 s. No significant differences were observed in measured workload. Displays that present patient data in a redesigned format enables critical care clinicians to more rapidly identify changes in patient conditions and to more accurately decide which patient needs their attention. In a clinical setting, this could improve patient safety. In future work, an evaluation of the display using live patient data from an ICU should be performed.

A far-view intensive care unit monitoring display enables faster triage.

Although nurses perform the majority of the clinical tasks in an intensive care unit, current patient monitors were not designed to support a nurse's workflow. Nurses constantly triage patients, deciding which patient is currently in the most need of care. To make this decision, nurses must observe the patient's vital signs and therapeutic device information from multiple sources. To obtain this information, they often have to enter the patient's room. This study addresses 3 hypotheses. Information provided by far-view monitoring displays (1) reduces the amount of time to determine which patient needs care first, (2) increases the accuracy of assigning priority to the right patient, and (3) reduces nurses mental workload. We developed 2 far-view displays to be read from a distance of 3 to 5 m without entering the patient's room. Both display vital signs, trends, alarms, infusion pump status, and therapy support indicators. To evaluate the displays, nurses were asked to use the displays to decide which of 2 patients required their attention first. They made 60 decisions: 20 with each far-view display and 20 decisions with a standard patient monitor next to an infusion pump. Sixteen nurses (median age of 27.5 years with 2.75 years of experience) participated in the study. Using the 2 far-view displays, nurses more accurately and rapidly identified stable patients and syringe pumps that were nearly empty. Median decision times were 11.3 and 12.4 seconds for the 2 far-view displays and 17.2 seconds for the control display. The 2 far-view displays reduced median decision-making times by 4.8 to 5.9 seconds, increased accuracy in assignment of priority in 2 of 7 patient conditions, and reduced nurses' frustration with the triaging task. In a clinical setting, the proposed far-view display might reduce nurses' mental workload and thereby increase patient safety.

A tool predicting future mean arterial blood pressure values improves the titration of vasoactive drugs.

BACKGROUND: Vasoactive drug infusion rates are titrated to achieve a desired effect, e.g., mean arterial blood pressure (MAP), rather than using infusion rates based on body weight. The purpose of this study is to evaluate a method to automatically identify a patient's sensitivity to sodium-nitroprusside, dobutamine or dopamine and to evaluate, whether an advisory system that predicts MAP 5 min in the future enhances a clinician's ability to titrate sodium-nitroprusside infusions. METHODS: We used published models implemented in MATLAB to simulate the response of 100 individual patients to infusions of sodium-nitroprusside, dopamine and dobutamine. The simulated patient's sensitivity to the three drugs was identified using an adaptive filter approach, where MAP was altered in a binary stepwise fashion. Next, 9 nurses were asked to control the MAP of 6 of the simulated patients. For half of the patients, we used the identified sensitivity to predict and display MAP 5 min into the future. RESULTS: Identifying each individual patient's sensitivity improved the accuracy of the MAP prediction by 75% for sodium-nitroprusside, 82% for dopamine and 52% for dobutamine over the MAP prediction based on an "average" patient's sensitivity. The advisory system shortened the median time to reach the desired MAP from 10.2 to 4.1 min, decreased the median number of infusion rate changes from 6 to 4, and resulted in a significant reduction of mental workload and effort. DISCUSSION: Patient-specific drug sensitivity identifi- cation significantly improved the prediction of future MAP. By predicting and displaying the expected MAP 5 min in the future, the advisory system helped nurses titrate faster, reduced their perceived workload and might improve patient safety.

Response surface model predictions of emergence and response to pain in the recovery room: An evaluation of patients emerging from an isoflurane and fentanyl anesthetic.

INTRODUCTION: Sevoflurane-remifentanil interaction models that predict responsiveness and response to painful stimuli have been evaluated in patients undergoing elective surgery. Preliminary evaluations of model predictions were found to be consistent with observations in patients anesthetized with sevoflurane, remifentanil, and fentanyl. This study explored the feasibility of adapting the predictions of sevoflurane-remifentanil interaction models to an isoflurane-fentanyl anesthetic. We hypothesized that model predictions adapted for isoflurane and fentanyl are consistent with observed patient responses and are similar to the predictions observed in our previous work with sevoflurane-remifentanil/fentanyl anesthetics. METHODS: Twenty-five patients scheduled for elective surgery received a fentanyl-isoflurane anesthetic. Model predictions of unresponsiveness were recorded at emergence, and predictions of a response to noxious stimulus were recorded when patients first required analgesics in the recovery room. Model predictions were compared with observations with graphical and temporal analyses. Results were also compared with our previous predictions after the administration of a sevoflurane-remifentanil/fentanyl anesthetic. RESULTS: Although patients were anesthetized, model predictions indicated a high likelihood that patients would be unresponsive (> or = 99%). After the termination of the anesthetic, model predictions of responsiveness well described the actual fraction of patients observed to be responsive during emergence. Half of the patients woke within 2 min of the 50% model-predicted probability of unresponsiveness; 70% woke within 4 min. Similarly, predictions of a response to a noxious stimulus were consistent with the number of patients who required fentanyl in the recovery room. Model predictions after the administration of an isoflurane-fentanyl anesthetic were similar to model predictions after a sevoflurane-remifentanil/fentanyl anesthetic. DISCUSSION: The results confirmed our study hypothesis; model predictions for unresponsiveness and no response to painful stimuli, adapted to isoflurane-fentanyl were consistent with observations. These results were similar to our previous study comparing model predictions and patient observations after a sevoflurane-remifentanil/fentanyl anesthetic.

An evaluation of remifentanil-sevoflurane response surface models in patients emerging from anesthesia: model improvement using effect-site sevoflurane concentrations.

INTRODUCTION: We previously reported models that characterized the synergistic interaction between remifentanil and sevoflurane in blunting responses to verbal and painful stimuli. This preliminary study evaluated the ability of these models to predict a return of responsiveness during emergence from anesthesia and a response to tibial pressure when patients required analgesics in the recovery room. We hypothesized that model predictions would be consistent with observed responses. We also hypothesized that under non-steady-state conditions, accounting for the lag time between sevoflurane effect-site concentration (Ce) and end-tidal (ET) concentration would improve predictions. METHODS: Twenty patients received a sevoflurane, remifentanil, and fentanyl anesthetic. Two model predictions of responsiveness were recorded at emergence: an ET-based and a Ce-based prediction. Similarly, 2 predictions of a response to noxious stimuli were recorded when patients first required analgesics in the recovery room. Model predictions were compared with observations with graphical and temporal analyses. RESULTS: While patients were anesthetized, model predictions indicated a high likelihood that patients would be unresponsive (> or = 99%). However, after termination of the anesthetic, models exhibited a wide range of predictions at emergence (1%-97%). Although wide, the Ce-based predictions of responsiveness were better distributed over a percentage ranking of observations than the ET-based predictions. For the ET-based model, 45% of the patients awoke within 2 min of the 50% model predicted probability of unresponsiveness and 65% awoke within 4 min. For the Ce-based model, 45% of the patients awoke within 1 min of the 50% model predicted probability of unresponsiveness and 85% awoke within 3.2 min. Predictions of a response to a painful stimulus in the recovery room were similar for the Ce- and ET-based models. DISCUSSION: Results confirmed, in part, our study hypothesis; accounting for the lag time between Ce and ET sevoflurane concentrations improved model predictions of responsiveness but had no effect on predicting a response to a noxious stimulus in the recovery room. These models may be useful in predicting events of clinical interest but large-scale evaluations with numerous patients are needed to better characterize model performance.

Improving alarm performance in the medical intensive care unit using delays and clinical context.

INTRODUCTION: In an intensive care unit, alarms are used to call attention to a patient, to alert a change in the patient's physiology, or to warn of a failure in a medical device; however, up to 94% of the alarms are false. Our purpose in this study was to identify a means of reducing the number of false alarms. METHODS: An observer recorded time-stamped information of alarms and the presence of health care team members in the patient room; each alarm response was classified as effective (action taken within 5 min), ineffective (no response to the alarm), and ignored (alarm consciously ignored or actively silenced). RESULTS: During the 200-h study period, 1271 separate entries by an individual to the room being observed were recorded, 1214 alarms occurred and 2344 tasks were performed. On average, alarms occurred 6.07 times per hour and were active for 3.28 min per hour; 23% were effective, 36% were ineffective, and 41% were ignored. The median alarm duration was 17 s. A 14-s delay before alarm presentation would remove 50% of the ignored and ineffective alarms, and a 19-s delay would remove 67%. Suctioning, washing, repositioning, and oral care caused 152 ignored or ineffective ventilator alarms. DISCUSSION: Introducing a 19-s alarm delay and automatically detecting suctioning, repositioning, oral care, and washing could reduce the number of ineffective and ignored alarms from 934 to 274. More reliable alarms could elicit more timely response, reduce workload, reduce noise pollution, and potentially improve patient safety.

Flow-through versus sidestream capnometry for detection of end tidal carbon dioxide in the sedated patient.

BACKGROUND: End tidal carbon dioxide (ETCO(2)) in non-intubated patients can be monitored using either sidestream or flow-through capnometry [Yamamori et al., J Clin Monit Comput 22(3):209-220, 2008]. The hypothesis of this validation study is that, flow-through capnometry will yield a more accurate estimate of ETCO(2) than sidestream capnometry when evaluated in a bench study during low tidal volumes and high oxygen administration via nasal cannula. Secondarily, when ETCO(2) from each is compared to arterial CO(2) (PaCO(2)) during a study in which healthy, non-intubated volunteers are tested under normocapnic, hypocapnic and hypercapnic conditions, the flow-through capnometer will resemble PaCO(2) more closely than the sidestream capnometer. This will be especially true during periods of lower minute ventilation and high oxygen flow rates via mask in non-intubated, remifentanil sedated, healthy volunteers whose physiologic deadspace is small. METHODS: The performance of a flow-through (cap-ONE, Nihon Kohden, Tokyo, Japan) and a sidestream (Microcap Smart CapnoLine Plus, Oridion Inc., Needham, MA) capnometer were compared in a bench study and a volunteer trial. A bench study evaluated ETCO(2) accuracy using waveforms generated via mechanical lungs during low tidal volumes and high oxygen flow rates. A volunteer study compared the ETCO(2) for each capnometer against PaCO(2) during sedation in which 8 l O(2) was delivered via mask rather than the nasal cannula. RESULTS: In the bench study, the flow-through capnometer gave slightly higher values of ETCO(2) during high-flow oxygen and no discernable differences during variable tidal volumes. Bland and Altman plots comparing ETCO(2) to PaCO(2) showed essentially equal performance between the two capnometers in the volunteers. CONCLUSIONS: Within a wide limit of agreement between the volunteer and bench study, flow-through and sidestream capnometry performed equally well during bench testing and in non-intubated, sedated patients.

Part Task and variable priority training in first-year anesthesia resident education: a combined didactic and simulation-based approach to improve management of adverse airway and respiratory events.

BACKGROUND: Part task training (PTT) focuses on dividing complex tasks into components followed by intensive concentrated training on individual components. Variable priority training (VPT) focuses on optimal distribution of attention when performing multiple tasks simultaneously with the goal of flexible allocation of attention. This study explored how principles of PTT and VPT adapted to anesthesia training would improve first-year anesthesiology residents' management of simulated adverse airway and respiratory events. The authors hypothesized that participants with PTT and VPT would perform better than those with standard training. METHODS: Twenty-two first-year anesthesia residents were randomly divided into two groups and trained over 12 months. The control group received standard didactic and simulation-based training. The experimental group received similar training but with emphasis on PTT and VPT techniques. Participant ability to manage seven adverse airway and respiratory events were assessed before and after the training period. Performance was measured by the number of correct tasks, making a correct diagnosis, assessment of perceived workload, and an assessment of scenario comprehension. RESULTS: Participants in both groups exhibited significant improvement in all metrics after a year of training. Participants in the experimental group were able to complete more tasks and answered more comprehension questions correctly. There was no difference in perceived workload or the number of correct diagnoses between groups. CONCLUSION: This study in part confirmed the study hypotheses. The results suggest that VPT and PTT are promising adjuncts to didactic and simulation-based training for management of adverse airway and respiratory events.

An evaluation of remifentanil propofol response surfaces for loss of responsiveness, loss of response to surrogates of painful stimuli and laryngoscopy in patients undergoing elective surgery.

INTRODUCTION: In this study, we explored how a set of remifentanil-propofol response surface interaction models developed from data collected in volunteers would predict responses to events in patients undergoing elective surgery. Our hypotheses were that these models would predict a patient population's loss and return of responsiveness and the presence or absence of a response to laryngoscopy and the response to pain after surgery. METHODS: Twenty-one patients were enrolled. Anesthesia consisted of remifentanil and propofol infusions and fentanyl boluses. Loss and return of responsiveness, responses to laryngoscopy, and responses to postoperative pain were assessed in each patient. Model predictions were compared with observed responses. RESULTS: The loss of responsiveness model predicted that patients would become unresponsive 2.4 +/- 2.6 min earlier than observed. At the time of laryngoscopy, the laryngoscopy model predicted an 89% probability of no response to laryngoscopy and 81% did not respond. During emergence, the loss of responsiveness model predicted return of responsiveness 0.6 +/- 5.1 min before responsiveness was observed. The mean probability of no response to pressure algometry was 23% +/- 35% when patients required fentanyl for pain control. DISCUSSION: This preliminary assessment of a series of remifentanil-propofol interaction models demonstrated that these models predicted responses to selected pertinent events during elective surgery. However, significant model error was evident during rapid changes in predicted effect-site propofol-remifentanil concentration pairs.

A simulation-based evaluation of a graphic cardiovascular display.

INTRODUCTION: A graphic presentation of complex information can facilitate early detection and management of adverse events. Prior work found that graphical presentation of selected cardiovascular variables led to earlier detection of a simulated ischemic event. Based on these findings, a second evaluation explored the utility of a graphical cardiovascular display (GCD) in a variety of simulated adverse cardiopulmonary events for two different display configurations. In this evaluation, we revised the GCD to present hemodynamic variables with or without a pulmonary artery catheter. Our hypotheses were that the revised GCD would improve detection of adverse cardiopulmonary events and add no additional perceived workload. METHODS: Sixteen anesthesiologists and anesthesia residents were enrolled in a simulation-based evaluation of the GCD. Participants were randomly split into two groups balanced for expertise and asked to manage six simulated adverse cardiopulmonary events. The GCD was present in half of the simulations, balanced across scenarios and groups. Participants' verbalizations and actions during each scenario were recorded and transcribed. Transcripts of treatment interventions were subsequently rated by two blinded expert anesthesiologists. Perceived workload, time to detection, and proper treatment of the adverse event were compared between groups. RESULTS: Experts ranked anesthesiologists using the GCD as being more effective overall and individually in three of six scenarios. Use of the GCD was demonstrated to influence the time to detection and the time to treatment of some critical events. There were no workload differences between display groups. DISCUSSION: Treatment intervention by participants using the GCD was rated superior by two blinded experts. The presence of the GCD resulted in a modest improvement in the time to detect myocardial ischemia and increased pulmonary capillary wedge pressure. The GCD may be a useful adjunct to monitor patients during adverse cardiopulmonary events.

Rapid recovery from sevoflurane and desflurane with hypercapnia and hyperventilation.

BACKGROUND: Hypercapnia with hyperventilation shortens the time between turning off the vaporizer (1 MAC) and when patients open their eyes after isoflurane anesthesia by 62%. METHODS: In the present study we tested whether a proportional shortening occurs with sevoflurane and desflurane. RESULTS: Consistent with a proportional shortening, we found that hypercapnia with hyperventilation decreased recovery times by 52% for sevoflurane and 64% for desflurane (when compared with normal ventilation with normocapnia). CONCLUSION: Concurrent hyperventilation to rapidly remove the anesthetic from the lungs and rebreathing to induce hypercapnia can significantly shorten recovery times and produce the same proportionate decrease for anesthetics that differ in solubility.

Development and evaluation of a just-in-time support system.

OBJECTIVE: To lay the foundation for a framework of just-in-time support (JITS) for novices dealing with urgent, unfamiliar tasks, and to evaluate a JITS system. BACKGROUND: More than 350,000 people die annually of cardiac arrest in the United States. In response, automated defibrillators are advocated that, unfortunately, do not provide important respiratory support. This paper presents elements of a framework for a JITS system that instructs a lay responder to follow a treatment protocol for integrating respiratory support with the use of an automatic external defibrillator. METHOD: We simulated a medical emergency using a high-fidelity patient simulator and asked participants to care for the patient. RESULTS: When using a paper-based NASA treatment protocol, participants made more errors and took longer to stabilize the injured person than when using the JITS system. CONCLUSION: These findings demonstrate the benefit of a JITS system to instruct novices in unfamiliar tasks. APPLICATION: The JITS system has the potential to improve the treatment outcome of victims of cardiac arrest. The JITS framework can be applied to many situations in which novices deal with urgent tasks without expertise available.

Hypercapnia shortens emergence time from inhaled anesthesia in pigs.

BACKGROUND: Anesthetic clearance from the lungs and the circle rebreathing system can be maximized using hyperventilation and high fresh gas flows. However, the concomitant clearance of CO2 decreases PAco2, thereby decreasing cerebral blood flow and slowing the clearance of anesthetic from the brain. This study shows that in addition to hyperventilation, hypercapnia (CO2 infusion or rebreathing) is a significant factor in decreasing emergence time from inhaled anesthesia. METHODS: We anesthetized seven pigs with 2 MACPIG of isoflurane and four with 2 MACPIG of sevoflurane. After 2 h, anesthesia was discontinued, and the animals were hyperventilated. The time to movement of multiple limbs was measured under hypocapnic (end-tidal CO2 = 22 mm Hg) and hypercapnic (end-tidal CO2 = 55 mm Hg) conditions. RESULTS: The time between turning off the vaporizer and to movement of multiple limbs was faster with hypercapnia during hyperventilation. Emergence time from isoflurane and sevoflurane anesthesia was shortened by an average of 65% with rebreathing or with the use of a CO2 controller (P < 0.05). CONCLUSIONS: Hypercapnia, along with hyperventilation, may be used clinically to decrease emergence time from inhaled anesthesia. These time savings might reduce drug costs. In addition, higher PAco2 during emergence may enhance respiratory drive and airway protection after tracheal extubation.

Hypercapnic hyperventilation shortens emergence time from isoflurane anesthesia.

BACKGROUND: To shorten emergence time after a procedure using volatile anesthesia, 78% of anesthesiologists recently surveyed used hyperventilation to rapidly clear the anesthetic from the lungs. Hyperventilation has not been universally adapted into clinical practice because it also decreases the Paco2, which decreases cerebral bloodflow and depresses respiratory drive. Adding deadspace to the patient's airway may be a simple and safe method of maintaining a normal or slightly increased Paco2 during hyperventilation. METHODS: We evaluated the differences in emergence time in 20 surgical patients undergoing 1 MAC of isoflurane under mild hypocapnia (ETco2 approximately 28 mmHg) and mild hypercapnia (ETco2 approximately 55 mmHg). The minute ventilation in half the patients was doubled during emergence, and hypercapnia was maintained by insertion of additional airway deadspace to keep the ETco2 close to 55 mmHg during hyperventilation. A charcoal canister adsorbed the volatile anesthetic from the deadspace. Fresh gas flows were increased to 10 L/min during emergence in all patients. RESULTS: The time between turning off the vaporizer and the time when the patients opened their eyes and mouths, the time of tracheal extubation, and the time for normalized bispectral index to increase to 0.95 were faster whenever hypercapnic hyperventilation was maintained using rebreathing and anesthetic adsorption (P < 0.001). The time to tracheal extubation was shortened by an average of 59%. CONCLUSIONS: The emergence time after isoflurane anesthesia can be shortened significantly by using hyperventilation to rapidly clear the anesthetic from the lungs and CO2 rebreathing to induce hypercapnia during hyperventilation. The device should be considered when it is important to provide a rapid emergence, especially after surgical procedures where a high concentration of the volatile anesthetic was maintained right up to the end of the procedure, or where surgery ends abruptly and without warning.