Academic Appointments


Clinical Trials


  • Effects of Different Tidal Volume Ventilation Strategies on Fontan Flow and Hemodynamics Not Recruiting

    In patients with Fontan circulation blood is not pumped to the lungs from a ventricle. Instead the superior vena cava and inferior vena cava is connected to the pulmonary artery and blood flow to the lungs occurs passively along this Fontan pathway. This passive blood flow to the lungs occurs best when the patient is breathing on their own (spontaneous ventilation). However for certain surgeries and procedures patients need to have an endotracheal tube inserted and need to be muscle relaxed and receive positive pressure ventilation. Prior studies have shown that positive pressure ventilation can reduce blood flow to the lungs and consequently blood returning to the heart resulting in less blood pumped out to the rest of the body (cardiac output). The purpose of this study is to investigate if changing the volume of the positive pressure ventilation (tidal volume) affects blood flow to the lungs and cardiac output in patients with Fontan circulation.

    Stanford is currently not accepting patients for this trial. For more information, please contact Manchula Navaratnam, MD, 650-714-6014.

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  • Quantra vs TEG for Congenital Cardiac Surgery - a Pilot Validation Study Not Recruiting

    Congenital heart surgery on cardio-pulmonary bypass (CPB) is associated with impacted coagulation quality and increased bleeding after separation of CPB. The current testing device used at our institution is the "TEG 5000" (Haemonetics Corporation). The novel coagulation testing device "Quantra System" (Hemosonics) has favorable properties (result within 20 minutes) allowing for a quicker identification of the coagulation problem and hence faster administration of the correct coagulation products, potentially leading to better coagulation quality and possibly reducing the need of additional blood products. The aim of this prospective observational (non-interventional, investigational only) quality improvement study is to investigate if the Quantra is reliable and valid in predicting the coagulation status when compared with our standard-of-care device TEG 5000.

    Stanford is currently not accepting patients for this trial. For more information, please contact Alexander R Schmidt, MD, 650-441-0719.

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All Publications


  • Incidence of adverse respiratory events after adjustment of clear fluid fasting recommendations to 1 h: a prospective, observational, multi-institutional cohort study. British journal of anaesthesia Schmitz, A., Kuhn, F., Hofmann, J., Habre, W., Erb, T., Preuss, M., Wendel-Garcia, P. D., Weiss, M., Schmidt, A. R. 2023

    Abstract

    Preoperative fasting reduces the risk of pulmonary aspiration during anaesthesia, and 2-h fasting for clear fluids has commonly been recommended. Based on recent evidence of shorter fasting times being safe, the Swiss Society of Paediatric Anaesthesia began recommending 1-h fasting for clear fluids in 2018. This prospective, observational, multi-institutional cohort study aimed to investigate the incidence of adverse respiratory events after implementing the new national recommendation.Eleven Swiss anaesthesia institutions joined this cohort study and included patients aged 0-15 yr undergoing anaesthesia for elective procedures after implementation of the 1-h fasting instruction. The primary outcome was the perioperative (defined as the time from anaesthesia induction to emergence) incidence of pulmonary aspiration, gastric regurgitation, and vomiting. Data are presented as median (inter-quartile range; minimum-maximum) or count (percentage).From June 2019 to July 2021, 22 766 anaesthetics were recorded with pulmonary aspiration occurring in 25 (0.11%), gastric regurgitation in 34 (0.15%), and vomiting in 85 (0.37%) cases. No major morbidity or mortality was associated with pulmonary aspiration. Subgroup analysis by effective fasting times (<2 h [n=7306] vs ≥2 h [n=14 660]) showed no significant difference for pulmonary aspiration between these two groups (9 [0.12%] vs 16 [0.11%], P=0.678). Median effective fasting time for clear fluids was 157 [104-314; 2-2385] min.Implementing a national recommendation of 1-h clear fluid fasting was not associated with a higher incidence of pulmonary aspiration compared with previously reported data.

    View details for DOI 10.1016/j.bja.2023.10.009

    View details for PubMedID 37953199

  • Intensive Care Unit Analgosedation After Cardiac Surgery in Children with Williams Syndrome : a Matched Case-Control Study. Pediatric cardiology Mills, M., Algaze, C., Journel, C., Suarez, G., Lechich, K., Kwiatkowski, M. D., Schmidt, A. R., Collins, R. T. 2023

    Abstract

    OBJECTIVE: Cardiovascular abnormalities are common in patients with Williams syndrome and frequently require surgical intervention necessitating analgesia and sedation in a population with a unique neuropsychiatric profile, potentially increasing the risk of adverse cardiac events during the perioperative period. Despite this risk, the overall postoperative analgosedative requirements in patients with WS in the cardiac intensive care unit have not yet been investigated. Our primary aim was to examine the analgosedative requirement in patients with WS after cardiac surgery compared to a control group. Our secondary aim was to compare the frequency of major ACE and mortality between the two groups.DESIGN: Matched case-control study.SETTING: Pediatric CICU at a Tertiary Children's Hospital.PATIENTS: Patients with WS and age-matched controls who underwent cardiac surgery and were admitted to the CICU after cardiac surgery between July 2014 and January 2021.INTERVENTIONS: None.MEASUREMENTS AND MAIN RESULTS: Postoperative outcomes and total doses of analgosedative medications were collected in the first six days after surgery for the study groups. Median age was 29.8 (12.4-70.8) months for WS and 23.5 (11.2-42.3) months for controls. Across all study intervals (48h and first 6 postoperative days), there were no differences between groups in total doses of morphine equivalents (5.0mg/kg vs 5.6mg/kg, p=0.7 and 8.2mg/kg vs 10.0mg/kg, p=0.7), midazolam equivalents (1.8mg/kg vs 1.5mg/kg, p=0.4 and 3.4mg/kg vs 3.8mg/kg, p=0.4), or dexmedetomidine (20.5 mcg/kg vs 24.4 mcg/kg, p=0.5 and 42.3 mcg/kg vs 39.1 mcg/kg, p=0.3). There was no difference in frequency of major ACE or mortality.CONCLUSIONS: Patients with WS received similar analgosedative medication doses compared with controls. There was no significant difference in the frequency of major ACE (including cardiac arrest, extracorporeal membrane oxygenation, and surgical re-intervention) or mortality between the two groups, though these findings must be interpreted with caution. Further investigation is necessary to elucidate the adequacy of pain/sedation control, factors that might affect analgosedative needs in this unique population, and the impact on clinical outcomes.

    View details for DOI 10.1007/s00246-023-03321-8

    View details for PubMedID 37882809

  • Acute Hemodynamics in the Fontan Circulation: Open-Label Study of Vasopressin. Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies Adamson, G. T., Yu, J., Ramamoorthy, C., Peng, L. F., Taylor, A., Lennig, M., Schmidt, A. R., Feinstein, J. A., Navaratnam, M. 2023

    Abstract

    OBJECTIVE: To describe the acute hemodynamic effect of vasopressin on the Fontan circulation, including systemic and pulmonary pressures and resistances, left atrial pressure, and cardiac index.DESIGN: Prospective, open-label, nonrandomized study (NCT04463394).SETTING: Cardiac catheterization laboratory at Lucile Packard Children's Hospital, Stanford.PATIENTS: Patients 3-50 years old with a Fontan circulation who were referred to the cardiac catheterization laboratory for hemodynamic assessment and/or intervention.INTERVENTIONS: A 0.03 U/kg IV (maximum dose 1 unit) bolus of vasopressin was administered over 5 minutes, followed by a maintenance infusion of 0.3 mU/kg/min (maximum dose 0.03 U/min).MEASUREMENTS AND MAIN RESULTS: Comprehensive cardiac catheterization measurements before and after vasopressin administration. Measurements included pulmonary artery, atrial, and systemic arterial pressures, oxygen saturations, and systemic and pulmonary flows and resistances. There were 28 patients studied. Median age was 13.5 (9.1, 17) years, and 16 (57%) patients had a single or dominant right ventricle. Following vasopressin administration, systolic blood pressure and systemic vascular resistance (SVR) increased by 17.5 (13.0, 22.8) mm Hg (Z value -4.6, p < 0.001) and 3.8 (1.8, 7.5) Wood Units (Z value -4.6, p < 0.001), respectively. The pulmonary vascular resistance (PVR) decreased by 0.4±0.4 WU (t statistic 6.2, p < 0.001), and the left atrial pressure increased by 1.0 (0.0, 2.0) mm Hg (Z value -3.5, p < 0.001). The PVR:SVR decreased by 0.04±0.03 (t statistic 8.1, p < 0.001). Neither the pulmonary artery pressure (median difference 0.0 [-1.0, 1.0], Z value -0.4, p = 0.69) nor cardiac index (0.1±0.3, t statistic -1.4, p = 0.18) changed significantly. There were no adverse events.CONCLUSIONS: In Fontan patients undergoing cardiac catheterization, vasopressin administration resulted in a significant increase in systolic blood pressure, SVR, and left atrial pressure, decrease in PVR, and no change in cardiac index or pulmonary artery pressure. These findings suggest that in Fontan patients vasopressin may be an option for treating systemic hypotension during sedation or general anesthesia.

    View details for DOI 10.1097/PCC.0000000000003326

    View details for PubMedID 37462430

  • Evaluation of continuous ampicillin/sulbactam infusion in critically ill patients. Life sciences Passon, S. G., Schmidt, A. R., Wittmann, M., Velten, M., Baehner, T. 2023; 320: 121567

    Abstract

    Continuous infusion (CI) of beta-lactam-antibiotics may improve pharmacodynamics in critically ill patients, but resulting concentrations have not been studied. Therapeutic drug monitoring is increasingly used to ensure antibiotic concentration. The aim of this study is to evaluate therapeutic ampicillin/sulbactam concentrations of a continuous infusion regimen.Medical records of all patients admitted to ICU between January 2019 and December 2020 were retrospectively reviewed. Each patient received a 2/1 g ampicillin/sulbactam loading dose, followed by a continuous infusion of 8/4 g per 24 h. Ampicillin serum concentrations were measured. Main outcomes were reaching of plasma concentrations breakpoint defined by minimum inhibitory concentration (MIC at 8 mg/l) and 4-fold MIC (MIC at 32 mg/l) during steady state of CI.In 50 patients a total of 60 concentration measurements were performed. The first concentration was measured after a median of 29 h (IQR 21-61 h). Mean ampicillin concentration was 62.6 ± 39.1 mg/l. Furthermore, serum concentrations exceeded the defined MIC breakpoint in all measurements (100 %) and were above the 4-fold MIC in 43 analyses (71.1 %). However, patients suffering from acute kidney injury exhibited significant higher serum concentrations (81.1 ± 37.7 mg/l vs. 38.2 ± 24.8 mg/l; p < 0.001). Also, there was a negative correlation between ampicillin serum concentrations and GFR (r = -0.659; p < 0.001).The described dosing regimen for ampicillin/sulbactam is safe with respect to the defined MIC breakpoints for ampicillin, and continuous subtherapeutic concentration is unlikely. However, with impaired renal function drug accumulation occurs, and with increased renal clearance, drug levels can be below the 4-fold MIC breakpoint.

    View details for DOI 10.1016/j.lfs.2023.121567

    View details for PubMedID 36907327

  • Pre-operative fasting in children: A guideline from the European Society of Anaesthesiology and Intensive Care. European journal of anaesthesiology Frykholm, P., Disma, N., Andersson, H., Beck, C., Bouvet, L., Cercueil, E., Elliott, E., Hofmann, J., Isserman, R., Klaucane, A., Kuhn, F., de Queiroz Siqueira, M., Rosen, D., Rudolph, D., Schmidt, A. R., Schmitz, A., Stocki, D., Sumpelmann, R., Stricker, P. A., Thomas, M., Veyckemans, F., Afshari, A. 2022; 39 (1): 4-25

    Abstract

    Current paediatric anaesthetic fasting guidelines have recommended conservative fasting regimes for many years and have not altered much in the last decades. Recent publications have employed more liberal fasting regimes with no evidence of increased aspiration or regurgitation rates. In this first solely paediatric European Society of Anaesthesiology and Intensive Care (ESAIC) pre-operative fasting guideline, we aim to present aggregated and evidence-based summary recommendations to assist clinicians, healthcare providers, patients and parents. We identified six main topics for the literature search: studies comparing liberal with conservative regimens; impact of food composition; impact of comorbidity; the use of gastric ultrasound as a clinical tool; validation of gastric ultrasound for gastric content and gastric emptying studies; and early postoperative feeding. The literature search was performed by a professional librarian in collaboration with the ESAIC task force. Recommendations for reducing clear fluid fasting to 1 h, reducing breast milk fasting to 3 h, and allowing early postoperative feeding were the main results, with GRADE 1C or 1B evidence. The available evidence suggests that gastric ultrasound may be useful for clinical decision-making, and that allowing a 'light breakfast' may be well tolerated if the intake is well controlled. More research is needed in these areas as well as evaluation of how specific patient or treatment-related factors influence gastric emptying.

    View details for DOI 10.1097/EJA.0000000000001599

    View details for PubMedID 34857683

  • Bronchopulmonary Dysplasia. Paediatric anaesthesia Schmidt, A. R., Ramamoorthy, C. 2021

    Abstract

    Bronchopulmonary dysplasia is the most frequent adverse outcome of prematurity. Before implementation of antenatal steroids and surfactant therapy bronchopulmonary dysplasia was mostly characterized by fibrotic, scarred and hyper-inflated lungs due to pulmonary injury following mechanical ventilation and oxygen toxicity. With advances in neonatal medicine this "old" bronchopulmonary dysplasia has changed to a "new" bronchopulmonary dysplasia characterized by an arrest in lung growth, leading to alveolar simplification and pulmonary vascular dysangiogenesis. While the old definition was based on the need for oxygen supplementation at a postnatal age of 28 days or at a corrected gestational age of 36 weeks, the newer definition looks at the mode of respiratory support required (e.g., invasive versus non-invasive) and then graded as mild, moderate or severe. Patients with bronchopulmonary dysplasia may present with significantly impaired pulmonary function, reactive airways disease or exercise intolerance. Over time these patients may develop asthma or chronic obstructive pulmonary disease. The most serious long term complication is the development of pulmonary vascular disease and pulmonary hypertension. Medical treatment often includes diuretics, steroids, bronchodilators or oxygen supplementation and in the presence of pulmonary hypertension medication to decrease the pulmonary vascular resistance. Perioperative anesthetic risk is increased in children with pulmonary hypertension. These patients might require additional diagnostic imaging and plans for increased resource allocation such as post-operative intensive care admission.

    View details for DOI 10.1111/pan.14365

    View details for PubMedID 34877749

  • Pre-operative fasting times for clear liquids at a tertiary children's hospital; what can be improved? Anesthesia and pain medicine Schmidt, A. R., Fehr, J., Man, J., D'Souza, G., Wang, E., Claure, R., Mendoza, J. 2021

    Abstract

    Background: The goal of preoperative fasting is to prevent pulmonary aspiration during general anesthesia. Fasting times are often prolonged leading to patient discomfort and risk for adverse events. This retrospective quality improvement survey evaluated effective nil-per-os (NPO) times and causes for prolonged NPO times with the aim to suggest improvement strategies by a newly founded fasting task force.Methods: Data from all electronic anesthesia records from 2019 at our institution were reviewed for fasting times. Our NPO instructions follow American Society of Anesthesiology guidelines and are calculated based on the patient's arrival time (90 min before operating room [OR] time). Primary outcome was the effective NPO time for clear liquids, secondary outcomes were incidence of delays and the parental compliance with the NPO instructions. Data are presented as median (interquartile range).Results: In total 9,625 cases were included in the analysis. NPO time was documented in 72.1% with a median effective NPO time of 7:13 h (7:36). OR in room times were documented in 72.8%, 2,075 (29.5%; median time 0:10 h [0:21]) were earlier and 4,939 (70.5%; median time 0:29 h [0:54]) were later than scheduled. Parental NPO compliance showed a median deviation for clear liquid intake of 0:55 h (8:30).Conclusions: This study revealed that effective NPO times were longer than current ASA guidelines. Contributing causes include case delays and parental non-compliance to NPO instructions. Thus, task force recommendations include change NPO instruction calculations to scheduled OR time versus arrival time, and encourage parents to give their child clear liquids at the instructed time.

    View details for DOI 10.17085/apm.21025

    View details for PubMedID 34289299

  • Augmented Reality Visualization Tool For The Future of Tactical Combat Casualty Care. The journal of trauma and acute care surgery Leuze, C., Zoellner, A., Schmidt, A. R., Fischer, M. J., Cushing, R. E., Joltes, K., Zientara, G. P. 2021

    Abstract

    The objective of this project was to identify and develop software for an Augmented Reality (AR) application that runs on the US Army Integrated Visual Augmentation System (IVAS) to support a medical caregiver during training and combat casualty care (TC3) scenarios. In this AR-TC3 application, human anatomy of individual soldiers obtained pre-deployment is superimposed on the view of an injured warfighter through the IVAS. This offers insight into the anatomy of the injured warfighter to advance treatment in austere environments.In this article, we describe various software components required for an AR-TC3-tool. These include a body pose tracking system to track the patient's body pose, a virtual rendering of a human anatomy avatar, speech input to control the application and rendering techniques to visualize the virtual anatomy and treatment information on the AR display. We then implemented speech commands and visualization for four common medical scenarios including injury of a limb, a blast to the pelvis, cricothyrotomy, and a pneumothorax on the Microsoft Hololens 1.The software is designed for a forward surgical care tool on the US Army IVAS, with the intention to provide the medical caregiver with a unique ability to quickly assess affected internal anatomy. The current software components still had some limitations with respect to speech recognition reliability during noise and body pose tracking. These will likely be improved with the improved hardware of the IVAS, which is based on a modified Hololens 2.LEVEL OF EVIDENCE: Basic science paper.

    View details for DOI 10.1097/TA.0000000000003263

    View details for PubMedID 33938509

  • Impact of Modified Anesthesia Management for Pediatric Patients With Williams Syndrome. Journal of cardiothoracic and vascular anesthesia Schmidt, A. R., Collins, R. T., Adusumelli, Y., Ramamoorthy, C., Weng, Y., MacMillen, K. L., Navaratnam, M. 2021

    Abstract

    OBJECTIVE: This study compared the percent change in systolic blood pressure and the incidence of adverse cardiac events (ACEs; defined as cardiac arrest, cardiopulmonary resuscitation, arrhythmias, or ST-segment changes) during anesthesia induction in patients with Williams syndrome (WS) before and after implementation of a perioperative management strategy.DESIGN: Retrospective observational cohort study.SETTING: Single quaternary academic referral center.PARTICIPANTS: The authors reviewed the records of all children with WS at the authors' institution who underwent general anesthesia for cardiac catheterization, diagnostic imaging, or any type of surgery between November 2008 and August 2019. The authors identified 142 patients with WS, 48 of whom underwent 118 general anesthesia administrations. A historic group (HG) was compared with the intervention group (IG).INTERVENTIONS: Change in perioperative management (three-stage risk stratification: preoperative intravenous hydration, intravenous anesthesia induction, and early use of vasoactives).MEASUREMENTS AND MAIN RESULTS: The authors determined event rates within 60 minutes of anesthesia induction. Standardized mean difference (SMD) was calculated (SMD >0.2 suggests clinically meaningful difference). Sixty-seven general anesthesia encounters were recorded in the HG (mean age, 4.8 years; mean weight, 16.3 kg) and 51 in the IG (mean age, 6.0 years; mean weight, 18.2 kg). The change in systolic blood pressure was -17.5% (-30.0, -5.0) in the HG versus -9% (-18.0, 5.0) in the IG (p = 0.015; SMD = 0.419), and the incidence of ACEs was 6% in the HG and 2% in the IG (p = 0.542; SMD = 0.207).CONCLUSIONS: Preoperative risk stratification, preoperative intravenous hydration, intravenous induction, and early use of continuous vasoactives resulted in greater hemodynamic stability, with a 2% incidence of ACEs.

    View details for DOI 10.1053/j.jvca.2021.04.019

    View details for PubMedID 34049787

  • Rabbit training model for establishing an emergency front of neck airway in children. British journal of anaesthesia Both, C. P., Diem, B. n., Alonso, E. n., Kemper, M. n., Weiss, M. n., Schmidt, A. R., Deisenberg, M. n., Thomas, J. n. 2021

    Abstract

    A 'cannot intubate, cannot oxygenate' (CICO) situation is rare in paediatric anaesthesia, but can always occur in children under certain emergency situations. There is a paucity of literature on specific procedures for securing an emergency invasive airway in children younger than 6 yr. A modified emergency front of neck access (eFONA) technique using a rabbit cadaver model was developed to teach invasive airway protection in a CICO situation in children.After watching an instructional video of our eFONA technique (tracheotomy, intubation with Frova catheter over which a tracheal tube is inserted), 29 anaesthesiologists performed two separate attempts on rabbit cadavers. The primary outcome was the success rate and the performance time overall and in subgroups of trained and untrained participants.The overall success rate across 58 tracheotomies was 95% and the median performance time was 67 s (95% confidence interval [CI], 56-76). Performance time decreased from the first to the second attempt from 72 s (95% CI, 57-81) to 61 s (95% CI, 50-81). Performance time was 59 s (95% CI, 49-79) for untrained participants and 72 s (95% CI, 62-81) for trained participants. Clinical experience and age of the participants was not correlated with performance time, whereas the length of the tracheotomy incision showed a significant correlation (P=0.006).This eFONA training model for children facilitates rapid skill acquisition under realistic anatomical conditions to perform an emergency invasive airway in children younger than 2 yr.

    View details for DOI 10.1016/j.bja.2020.12.032

    View details for PubMedID 33526261