Search

A rapid emergence from anesthesia combined with an extended duration of adequate analgesia is desired. Difficulties arise when trying to achieve a rapid emergence and provide adequate analgesia for procedures associated with moderate post operative pain. We propose to use pharmacokinetic (PK) and pharmacodynamic (PD) models with optimization techniques to determine anesthetic drugs ratios to improve post-anesthetic outcomes of emergence and analgesia. We hypothesize that optimized propofol, remifentanil, and fentanyl administrations will shorten emergence time and extend the period of adequate analgesia during patient recovery. Anesthesiologists administered a general anesthetic to 21 patients for laparoscopic procedures with propofol, remifentanil, and fentanyl according to their standard practice. The theoretical improvement provided by the optimization was measured by comparing the time differences between the control predictions and the optimized prediction of the TROR time and TRON time. In the control group the TROR was 10.2+-5.8 minutes (mean +- SD) and TRON was 3.5+-5.0 minutes after emergence. In the optimized group the TROR was 7.5+-2.2 minutes or 26% faster (p < .001, paired t-test) and the TRON was 7.4 +-2.4 minutes or 88% longer (p < .00001, t-test). Optimized administrations of propofol, remifentanil, and fentanyl resulted in a theoretically shorter emergence time and a longer period of adequate postoperative analgesia. The optimization algorithm shows potential for real-time clinical guidance in drug management.

Intro-Differences in anesthetic technique when using propofol, remifentanil and fentanyl can result in different emergence and nociception outcomes. After surgery, a brief emergence period combined with an extended duration of analgesia is desired. We propose to use pharmacokinetic (PK)1-4 and pharmacodynamic (PD)5,6 models to find optimized ratios of propofol and remifentanil to shorten emergence time and extend the time until inadequate analgesia is experienced during patient recovery. Modeling has been used to find the optimum effect site concentrations (CeS) for rapid wake up7; however, an optimization technique which also accounts for analgesic effect is desirable. Method-Anesthesiologists gave general anesthesia to 21 patients for laproscopic procedures using propofol, remifentanil, and fentanyl using a standard of care anesthetic technique. Baseline model predictions for CeS were calculated for remifentanil, fentanyl, and propofol. PD response surface models were used to calculate the probabilities of unconsciousness and response to noxious stimulus (30 PSI tibial pressure algometry, a surrogate of postoperative pain) during and after the anesthetic. Post-hoc optimized PK and PD model predictions were made for both sedation and analgesia by varying the ratio of propofol and remifentanil CeS, constrained to the same or higher PD model predicted probabilities, and leaving fentanyl CeS unchanged from baseline. For each patient, optimized changes to the recorded propofol and remifentanil infusions were made every 5 minutes during the general anesthetic. The theoretical improvement provided by the optimization was measured by comparing the time differences between the baseline model predications and the optimized prediction of the emergence time and time to inadequate analgesia. Results-The baseline model predictions found an average emergence time of 8.2 +/- 5.6 minutes after end of surgery and a duration of analgesia of 9.9 +/- 13.6 minutes after patient emergence. The optimized remifentanil and propofol CeS theoretically reduced the emergence time to 3.9 +/- 1.6 (p

Alternative drug combinations are anesthetically equipotent but have different re-emergence and nociception outcomes. The perfect drug combination - causing a short post surgery wake up time and an extended time until pain - is dependent on the patient, surgical stimulus, and previous dosing. Our goal is to create a technique to find optimized drug dosings that lessens re-emergence time and extends nociception. Method - Use records from 20 general anesthestic procedures that involved Remifentanil and Propofol we calculated equipotent concentrations with more desirable results. Results - The optimization technique improved post surgery re-emergence time on average 5.22 minutes and lengthened nociception time on average 4.22, 7.55, and 9.84 minutes for the three different cases. Discussion - This technique fulfills its primary goal to find more optimal concentrations for anesthesia. The technique is capable of clinical practice to offer optimal suggestions to the anesthesiologist during surgery.

What is the best drug concentration during anesthesia? We are creating algorithms to minimize pain and shorten wake up time after surgery. This will be used by anesthesiologist during surgery to continuously provide optimal drug cocktails with surgery and patient specificity.

We have developed graphic technology to display data from the respiratory monitors used during anesthesia. The display uses color, texture, shape and emergent features to highlight abnormal pulmonary physiology. Nineteen anesthesiologists participated in a simulator based evaluation (METI, Sarasota, FL.). Half the subjects used the metaphor display and half did not. Each subject was trained for 10 minutes on the pulmonary display. The time difference during the obstructed endotracheal tube did prove significant (p=0.02) in favor of the pulmonary display condition. During the intrinsic PEEP scenario, the subjects treated the patient earlier (positive trend p=0.l) with the pulmonary display compared to the control condition. The group that used the pulmonary display treated a restricted upper airway more quickly (2.3 min vs. 3.9 min). Subjects liked the simplicity of the design. In future studies, we hope to further reduce the time for the detection and treatment of all scenarios by improving the design's intuitiveness, integration, and emergent features.

As the frequency and duration of space travel increase, the potential need for emergency medical care in space grows, and with it the need for patient monitoring devices supporting therapeutic treatment. Providing emergency care to an injured astronaut may necessitate immediate surgery. During such events, the timely administration of anesthetic agents will need to be performed by someone who is not a formally trained anesthesiologist. The availability of usable real-time displays of intravenous anesthetic concentrations and effects could significantly enhance intraoperative clinical decision-making both in space and on earth. The effectiveness of the real-time anesthesia display on the management of total intravenous anesthesia was determined by 31 anesthesiologists participating in a simulation study. In the presence of the anesthesia drug display, clinicians maintained physiologic indicators such as blood pressure and heart rate closer to baseline levels. Participants also reported an increase in perceived performance when using the drug display. The results indicate that surgeries on earth and in orbit would benefit from the implementation of this display.

Medical decision making is a crucial process to successfully treat a critical medical emergency. During an unexpected medical event, astronauts, like anesthesiologists, must react quickly in a complex environment. Tools, such as the pulmonary metaphor display, were created to aid the medical caregiver's decision making process. The pulmonary metaphor display is designed to help the caregiver collect and integrate pulmonary data to provide a more accurate, quicker diagnosis and treatment. The following outline anesthesiology simulation study will provide the data to prove that the pulmonary metaphor display is beneficial to medical decision making.

We have implemented a real-time simulator of gas exchange in the human body and lung. The system realistically mimics respiratory gas uptake and production as a function of pulmonary, cardiovascular, and metabolic parameters. The implementation consists of hardware and software to control the flow of gases entering and leaving a ventilated test lung. Such a device could serve as a bench-top resource for testing newly developed anesthesia, hemo-dynamic, and patient monitors. Preliminary tests have been performed for validation of a non-invasive cardiac monitor. The results, while promising, expose the need for more sophisticated models of the human respiratory and circulatory physiology.

A human lung simulator was implemented using a model based on the Fick principle. The simulator is designed to emulate C02 production and 02 consumption in the body and gas exchange in the lung. The implementation consists of hardware and software to control the flow of gases entering and leaving a ventilated test lung. An initial test of C02 production qualitatively demonstrated that the lung simulator behaved as expected. Since this project is in its initial stages, additional experimentation and model refinement is necessary for the simulator to accurately represent physiologic responses of a human lung.