Smart respiratory monitoring: clinical development and validation of the IPI™ (Integrated Pulmonary Index) algorithm.

Continuous electronic monitoring of patient respiratory status frequently includes PetCO2 (end tidal CO2), RR (respiration rate), SpO2 (arterial oxygen saturation), and PR (pulse rate). Interpreting and integrating these vital signs as numbers or waveforms is routinely done by anesthesiologists and intensivists but is challenging for clinicians in low acuity areas such as medical wards, where continuous electronic respiratory monitoring is becoming more common place. We describe a heuristic algorithm that simplifies the interpretation of these four parameters in assessing a patient's respiratory status, the Integrated Pulmonary Index (IPI). The IPI algorithm is a mathematical model combining SpO2, RR, PR, and PetCO2 into a single value between 1 and 10 that summarizes the adequacy of ventilation and oxygenation at that point in time. The algorithm was designed using a fuzzy logic inference model to incorporate expert clinical opinions. The algorithm was verified by comparison to experts' scoring of clinical scenarios. The validity of the index was tested in a retrospective analysis of continuous SpO2, RR, PR, and PetCO2 readings obtained from 523 patients in a variety of clinical settings. IPI correlated well with expert interpretation of the continuous respiratory data (R = 0.83, p <<< 0.001), with agreement of -0.5 ± 1.4. Receiver operating curves analysis resulted in high levels of sensitivity (ranging from 0.83 to 1.00), and corresponding specificity (ranging from 0.96 to 0.74), based on IPI thresholds 3-6. The IPI reliably interpreted the respiratory status of patients in multiple areas of care using off-line continuous respiratory data. Further prospective studies are required to evaluate IPI in real time in clinical settings.

The use of a PID controller to model vecuronium pharmacokinetics and pharmacodynamics during liver transplantation. Proportional-integral-derivative.

A four-phase proportional-integral-derivative (PID) controller was evaluated under the extremely unstable conditions of liver transplantation. Vecuronium was delivered to achieve 80%-90% neuromuscular blockade as measured by electromyogram (EMG). The first two controller phases delivered boluses and a constant infusion calculated to rapidly achieve setpoint, followed by a proportional-derivative (PD) phase at 35% from setpoint, and PID within 10% of the setpoint. During liver transplantation, the sources of system instability included large blood losses, temperature changes, and loss of hepatic drug metabolism during removal and replacement. During prolonged surgery, and when blood losses were not severe, the EMG remained within 10% of setpoint. Controller performance was more variable during system instability. Plasma sampling and two-compartment modelling of the infusion and response with a weighting factor for blood loss allowed estimation of the sources and degree of instability for improved design of future controllers.

Continuous spinal anesthesia for cesarean section in a parturient with severe preeclampsia.

Epidural anesthesia is a widely accepted technique for cesarean section in the preeclamptic patient with normal coagulation. Regional anesthetic techniques avoid the hazards associated with tracheal intubation in the preeclamptic or eclamptic patient. To date, continuous spinal anesthesia in the preeclamptic parturient has not been described. We present a case in which continuous spinal anesthesia was administered for cesarean section in a morbidly obese parturient with severe preeclampsia. Continuous spinal anesthesia was successfully administered without significant hemodynamic consequences or maternal or fetal morbidity. This case suggests that continuous spinal anesthesia may be a viable alternative anesthetic technique for operative delivery in the preeclamptic parturient when epidural anesthesia cannot be established.

Individualized outcome feedback produces voluntary antiemetic prescribing practice changes.

STUDY OBJECTIVE: To determine the impact of individualized outcome feedback on antiemetic prescribing practices and compare outcomes of a cost-effective, standardized antiemetic protocol (PROT) to that of customized antiemetic therapy (NONPROT). DESIGN: Prospective, observational study with randomized component. SETTING: Postanesthesia care unit (PACU) of an academic medical center. PATIENTS: 3027 consecutive ASA physical status I, II, and III patients receiving general anesthesia. INTERVENTIONS: Patients were randomized to receive 0.625 mg droperidol or 4 mg ondansetron for postoperative nausea and/or vomiting (PONV) from a protocol, or received customized antiemetic therapy. MEASUREMENTS AND MAIN RESULTS: Incidence of PACU PONV, selection of PROT versus NONPROT, patient satisfaction, and use of PONV prophylaxis were measured and indexed by an attending anesthesiologist in a monthly report for 4 months. Monthly expenditures for antiemetic therapy prior to, during, and after the study were collected. Literature on PONV outcomes, appropriate timing, and selection of PONV prophylaxis was distributed. The NONPROT group was slightly older than the PROT group; otherwise, demographics were similar between all groups. The incidence of PONV did not differ between the PROT and NONPROT groups (11% vs. 10%), and the incidence of PONV in patients receiving prophylaxis was higher in both groups (17% PROT vs. 15% NONPROT). Patients receiving ondansetron as a first-line drug required rescue therapy less often (5%) than those receiving droperidol (14%); however, patient satisfaction was indistinguishable among all groups. During the study, the use of prophylaxis decreased 47% without an increase in PONV, and PROT selection increased 54%. CONCLUSIONS: Individualized outcome feedback produced a 48% reduction in monthly expenditures for ondansetron and droperidol, which was sustained after the study. Patients satisfaction between ondansetron 4 mg and droperidol 0.625 mg given in the PACU did not differ in spite of a slightly greater efficacy of ondansetron as a first-line drug.

Patient-borne memory device facilitates "point of care" data access.

Although electronic medical records and a central database have made accurate and consistent patient medical information more readily available than with the traditional patient chart, there are many locations in healthcare facilities where terminals for accessing patient data are not available. As patient care becomes decentralized and more patients require anesthesia outside of the operating suites, routing a network-based system to all these locations can be expensive and time consuming. We designed a system whereby essential patient data of interest to anesthesiologists is stored on an electronic memory device the size of a watch battery attached to the patient's wristband. Accessing and editing the data is done via a hand-held computer. This system provides secure patient data storage and management at the "point of care." At the conclusion of the patient's anesthesia-related care, the data is downloaded to a relational database for use in outcome analysis, billing, and quality assurance. After collecting preoperative evaluations, intraoperative data, and postoperative data on 560 patients anesthetized for surgery or other procedures, we find this system to be a reliable, low-cost, medical information management system, with possible application to other medical specialties.

Successful strategies for improving operating room efficiency at academic institutions.

UNLABELLED: In this prospective study, we evaluated the etiology of operating room (OR) delays in an academic institution, examined the impact of multidisciplinary strategies to improve OR efficiency, and established OR timing benchmarks for use in future OR efficiency studies. OR times and delay etiologies were collected for 94 cases during the initial phase of the study. Timing data and delay etiologies were analyzed, and 2 wk of multidisciplinary OR efficiency awareness education was conducted for the nursing, surgical, and anesthesia staff. After the education period, timing data were collected from 1787 cases, and monthly reports listing individual case delays and timing data were sent to the Chiefs of Service. For the first case of the day, patient in room, anesthesia ready, surgical preparation start, and procedure start time were significantly earlier (P < 0.01) in the posteducation period compared with the preeducation period, and the procedure start time for the first case of the day occurred, on average, 22 min earlier than all other procedures. For all cases combined, turnover time decreased, on average, by 16 min. Unavailability of surgeons, anesthesiologists, and residents decreased significantly (P < 0.05) as causes of OR delays. Anesthesia induction times were consistently longer for the vascular and cardiothoracic services, whereas surgical preparation time was increased for the neurosurgical and orthopedic services (P < 0.05). Identification of the etiology of OR inefficiency, combined with multidisciplinary awareness training and personal accountability, can improve OR efficiency. The time savings realized are probably most cost-effective when combined with more flexible OR staffing and improved OR scheduling. IMPLICATIONS: We achieved significant improvements in operating room efficiency by analyzing operating room data on causes of delays, devising strategies for minimizing the most common delays, and subsequently measuring delay data. Personal accountability, streamlining of procedures, interdisciplinary team work, and accurate data collection were all important contributors to improved efficiency.

Closed-loop infusion of atracurium with four different anesthetic techniques.

A new proportional-integral-derivative (PID) controller for the automated closed-loop delivery of atracurium was tested in 32 patients. Groups of 8 patients received halothane, enflurane, isoflurane, or N2O/morphine anesthesia. After induction of anesthesia with sodium thiopental 3-5 mg.kg-1, a bolus of atracurium 0.2 mg.kg-1 was delivered by the controller; this was followed by an infusion calculated by the controller to maintain the electromyogram (EMG) at a setpoint of 90% neuromuscular blockade. The average overshoot for the controller was 10.1% and the mean steady-state error 3.0%. The mean infusion rates for atracurium to maintain 90% blockade were calculated for each anesthetic group, with the inhalation anesthetics at 1 MAC. Infusion rates for N2O/morphine, halothane 0.8%, enflurane 1.7%, and isoflurane 1.4% at 90% blockade were 5.7 +/- 0.6, 4.9 +/- 0.3, 3.5 +/- 0.3, and 4.1 +/- 0.5 micrograms.kg-1.min-1, respectively (mean +/- SE). The infusion rate for atracurium at 90% blockade under N2O/morphine anesthesia was in general agreement with published values. The other infusion rates at 90% blockade have not been reported previously, but correspond to the known potencies of these inhalation anesthetics for augmentation of neuromuscular blockade. This controller performed well in comparison to previously developed controllers, and in addition was used as a research tool for rapid estimation of infusion rates.

"One-stop" surgery: implications for anesthesiologists of an expedited pediatric surgical process.

BACKGROUND: "One-stop surgery" (OSS) allows pediatric patients to undergo initial surgical evaluation, anesthesia, surgery, and discharge home, on the same day. METHODS: Patients referred for umbilical hernia repair, circumcision, or central venous catheter removal completed a screening questionnaire, after which they were scheduled for initial surgical and anesthesia evaluation if eligible and had surgery if indicated on the same day. RESULTS: Three patients had comorbidity precluding OSS, two patients refused indicated surgery, two patients did not require surgery, and 12 patients did not keep their appointment. Eighty patients had surgery without complications. Average total time was significantly shorter for OSS than non-OSS for circumcision (120 vs 142 min) and umbilical hernia repair (139 vs 165 min) but similar for catheter removal (100 vs 109 min). All families were satisfied with OSS. CONCLUSIONS: One-stop surgery appears to be a safe, efficient, and convenient alternative to the traditional process for patients and their families.