Faculty Bibliography

In this paper, the development and implementation of L-1 adaptive control designs for anesthesia delivery to patients in surgical settings is presented. Our main objectives are the design of model-based feedback controllers ensuring that the patient's bispectral index profile tracks a prespecified reference trajectory, and demonstrates robustness to inter-patient variability. Patient models are constructed based on clinical trial data and gray box system identification methods. Controller switching mechanisms and specific safety measures are considered in the design and discussed in the paper. Simulation results are provided, demonstrating the effectiveness of the control methods. (C) 2015 Elsevier Ltd. All rights reserved.

INTRODUCTION: Serum troponin levels are employed as sensitive markers of perioperative ischemia and/or infarction and result in elevated levels 2-4 hours after myocyte damage, and peak at approximately 12 hours. This measurement is insightful, as ischemia may be subclinical in the perioperative period. Reportedly, infarcts occur 24-48 hours postoperatively. However, we sought to examine this and determine the specific incidence and time period when troponin elevations occurred in our patient population. This data is useful to direct our perioperative specialists when and where to focus increased scrutiny. METHODS: With IRB approval, a retrospective analysis of 44,800 cases during 2013 and the first quarter of 2014 were reviewed to determine if and when troponins were elevated during the perioperative period. All cases were performed at NYU Langone Medical Center with cardiac surgical cases excluded. Surgical services which did not send any troponin values during the course of the study were also excluded. Specifically, time to peak troponin and which surgical service was performing the operation was evaluated. RESULTS: A total of 44,800 non cardiac cases were performed over 2013 and the first quarter of 2014. Troponins were drawn on 3736 patients with 633 cases having a positive troponin. Vascular surgery was the surgical department with the highest percentage of cases having a positive troponin (15%). 13% of troponins peaked immediately post op while 47% of peak troponins occurred greater than 24 hours after departing the operating room. The distribution of positive troponins by service is shown in the pie chart. Ortho Spine & Joints are over-weighted because of the high volume of cases (> 15% of all cases). CONCLUSIONS: Our results confirm a significant intra-operative risk with a majority of peak troponins in the first 24 hours (peak time 12-16 hours after surgery), and an elevated incidence out to 48 hours. There may be an artifact in clustering of times due to fixed collection times for blood samples. As perioperative specialists, knowing when ischemia occurs and which patients are at high risk for having positive troponins will allow us to conduct future studies aimed at preventing and limiting the morbidity and mortality from myocardial ischemia. This study provides quantitative measures of the relative risk of various types of surgery and the timing of myocardial damage in the perioperative period

INTRODUCTION: As the healthcare landscape evolves, hospital administrators are requiring healthcare providers, including anesthesiologists, to be more efficient and cost-effective. Currently, no national benchmark exists for intraoperative anesthesia induction and preparation times. Without an existing standard, healthcare administrators may have unrealistic expectations as to what the average "anesthesia induction time" should be. To help establish a baseline, we have provided the average "anesthesia induction" times for 40,120 out of 52,349 cases performed in our institution based upon the number of anesthetic procedures/interventions performed to prepare a patient for surgery. METHODS: With IRB approval, a retrospective analysis of 52,349 cases was performed from our electronic medical record in a 15-month period. 12,247 anesthetic interventions were excluded for incomplete documentation of data points or for extreme outliers in the data set, considered being five standard deviations away from mean. The average time from "wheels into the operating room" to "ready for surgical preparation and positioning" of 40,102 cases were recorded based upon the number of anesthetic procedures/ interventions performed. RESULTS: CONCLUSIONS: Our results reveal the average intraoperative anesthesia ready time based on the number of anesthetic procedures/ interventions performed in an academic medical center. This data may help administrators and anesthesiology departments create realistic models toward perioperative efficiency. Further analysis of the data is needed to differentiate the average anesthesia ready time of cases based on staffing (attending alone versus with house staff or nurse anesthetist). (Figure Presented)

The bispectral (BIS) monitor uses brain electroencephalographic data to measure the depth of sedation and pharmacological response during anaesthetic procedures. In this case, the BIS monitor was used for another purpose, to demonstrate postoperatively to the nursing staff that a patient with history of locked-in syndrome (LIS), who underwent pressure ulcer debridement, had periods of wakefulness and apparent sensation, even with his eyes closed. Furthermore, as patients with LIS can feel pain, despite being unable to move, local block or general anaesthesia should be provided for sharp surgical debridement and other painful procedures. This use of the BIS has shown that as a general rule, the staff should treat the patient as though he might be awake and sensate even if he does not open his eyes or move his limbs. The goal of this study was to continuously monitor pain level and communicate these findings to the entire wound team, i.e. anaesthesiologists, surgeons and nurses.

INTRODUCTION: The objective of this study was to determine the effects of isoproterenol infusion on level of consciousness during ablation using total intravenous anesthesia. METHODS AND RESULTS: Seven patients undergoing total intravenous anesthesia for atrial fibrillation ablation were monitored for level of consciousness using bispectral EEG levels (BIS). Isoproterenol infusion was performed after the ablation during anesthesia. BIS levels prior to, during, and post-isoproterenol infusion were recorded and correlated to isoproterenol infusion doses. In all patients, BIS levels significantly increased during isoproterenol infusion (median BIS prior to infusion, 46; during infusion, 64 (p < 0.02)). With a subsequent increase in anesthetic medication, BIS levels could again be reduced. CONCLUSION: Isoproterenol infusion alters consciousness level during total intravenous anesthesia for atrial fibrillation ablation. BIS monitoring is a novel way to modulate anesthesia during ablation to potentially optimize patient comfort and ablation success.

Introduction : With the increase in anesthesia utilization in the electrophysiology laboratory, there is greater potential for arrhythmia suppression during electrophysiology study. Intravenous isoproterenol is frequently used to counteract the significant antiadrenergic impact of anesthesia, as well as induce arrhythmias and identify reconnection of pulmonary vein conduction. The effects of isoproterenol on cerebral and respiratory function during the sedated state have not been well studied. The Bispectral (BIS) Vista TM Monitor is a non-invasive device that measures electrical activity of the brain and computes a BIS value, which corresponds to a level of consciousness. The purpose of this study was to determine changes in BIS values during isoproterenol administration. Methods : Twenty consecutive patients underwent electrophysiology study under total intravenous anesthesia using propofol and remifentanil infusions. Isoproterenol was infused at a rate of 5mcg/kg/min and escalated to up to 20mcg/kg/min over 20 minutes. BIS levels were recorded before and throughout isoproterenol administration. Results : Patients demonstrated significant elevation in BIS value during isoproterenol infusion. The mean difference between pre- and post- BIS values was 21.3 [5.4, 37.2] (p = 0.00013). The isoproterenol doses which triggered a BIS spike ranged from 10.8 mcg to 90.8 mcg. The median effective isoproternol dose was 25.2 mcg. The median onset time for an isoproternol stimulated BIS spike was 6.9 minutes with rates from 2 to 20 mcg/minute. Discussion : Isoproterenol significantly increases BIS values during sedated electrophysiology study. Monitoring BIS values may be helpful in assessing the isoproterenol dosage required to overcome the suppressive effects of anesthesia on arrhythmia induction, as well as the potential need for additional anesthetics to prevent patient arousal. Conversely, decreasing BIS values are known to correlate with hypotensive episodes signaling cerebral hypoperfusion. This may be relevant in cases of hemodynamically unstable tachycardias. BIS appears to be an important tool for the optimization of anesthesia when isoproterenol is administered during electrophysiology study

BACKGROUND: The perioperative course of patients undergoing intracranial surgery is frequently complicated by hypertensive episodes. Dexmedetomidine (DEX), an alpha-2 adrenoreceptor agonist, is gaining popularity in neuroanesthesia, because its sympatholytic and antinociceptive properties may improve hemodynamic stability at critical moments of surgery. We designed this study to assess the efficacy of DEX in controlling hypertensive responses in patients undergoing intracranial surgery. METHODS: Patients scheduled for elective craniotomy were randomly assigned to receive either sevoflurane-opioid or sevoflurane-opioid-DEX anesthesia. Bispectral index was used to maintain a similar level of hypnosis in both groups (40-50). Opioids, sevoflurane, and vasoactive medications were titrated in a routine manner, at the discretion of the blinded anesthesiologist managing the case, to maintain systolic blood pressure (SBP) targeted within 90-130 mm Hg and heart rate (HR) between 50 and 90 bpm. Hemodynamic variables were continuously recorded and stored on a computer for analysis. Efficacy of the anesthetic technique in controlling SBP or HR is inversely proportional to the area under the curve (AUC) outside the targeted range. Areas under the curves above and below targeted ranges for SBP-time (AUCsbp mm Hg*min/h) and HR-time (bpm*min/h) were compared. Coefficient of variation was used to assess hemodynamic stability. RESULTS: Seventy-two patients were recruited for the study. Computerized records of 56 patients only were analyzed because of technical problems with data collection in 14 cases. AUCsbp for above the targeted range was significantly lower for patients in the DEX group (P=0.044). The coefficient of variation for SBP or HR did not differ between groups. A significantly smaller proportion of patients in the DEX group required treatment with antihypertensive medications (12 of 28, 42% vs 24 of 28, 86%, P=0.0008). The DEX group required fewer opioids in the intraoperative period, but there were no differences in the use of sevoflurane. In the postanesthesia care unit, patients in the DEX group had fewer hypertensive episodes (1.25+/-1.55 vs 2.50+/-2.00, P=0.0114) and were discharged earlier (91+/-17 vs 130+/-27 min, P<0.0001). There were no differences in the requirement for postoperative opioids or antiemetics. CONCLUSIONS: By using indices, which assess a global hemodynamic stability of the anesthetic, we determined that intraoperative DEX infusion was effective for blunting the increases in SBP perioperatively. The use of DEX did not increase the incidence of hypotension or bradycardia, common side effects of the drug