Bio

Clinical Focus


  • Anesthesia

Academic Appointments


Professional Education


  • Medical Education:Baylor College of Medicine Registrar (2004) TX
  • Internship:Baylor College of Medicine Registrar (2005) TX
  • Residency:Stanford University Medical Center - Anesthesia (2008) CA
  • Fellowship, Stanford University Medical Center, Obstetric Anesthesiology (2009)
  • Board Certification: Anesthesia, American Board of Anesthesiology (2010)

Research & Scholarship

Clinical Trials


  • In-vitro Study to Assess the Coagulation Effects of Exogenous Oxytocin Using Thromboelastography. Not Recruiting

    Oxytocin is normally administered following delivery in pregnant patients to reduce postpartum bleeding by increasing uterine tone. It is unclear whether the use of intravenous oxytocin alters coagulation in pregnant patients. The purpose of the in-vitro study is to assess the coagulation changes of oxytocin in blood samples from pregnant patients using thromboelastrography (TEG). TEG is a point-of-care device which measures the viscoelastic properties of clot formation, and can provide rapid and detailed information about coagulation changes. We aim to collect blood samples from pregnant patients to assess the in-vitro effects of synthetic oxytocin on coagulation using TEG.

    Stanford is currently not accepting patients for this trial.

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  • Thromboelastography to Assess Hemostatic Changes in Patients Undergoing Elective Cesarean Delivery. Not Recruiting

    The purpose of the study is to assess the coagulation changes that occur in patients undergoing elective Cesarean delivery using thromboelastography (TEG). We will compare coagulation data to assess potential coagulation changes associated with hemoglobin changes before and after surgery, and related to estimated blood loss.

    Stanford is currently not accepting patients for this trial.

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  • Effects of Epidural Lidocaine on the Pharmacokinetic and Pharmacodynamic Profiles of DepoDur® After Cesarean Delivery Not Recruiting

    To evaluate the levels of morphine in a patient's blood when morphine is given into the epidural space in the form of DepoDur® either alone or following a dose of lidocaine also given in the epidural space.

    Stanford is currently not accepting patients for this trial. For more information, please contact Brendan Carvalho, (650) 861 - 8607.

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Publications

All Publications


  • Prior epidural lidocaine alters the pharmacokinetics and drug effects of extended-release epidural morphine (DepoDur®) after cesarean delivery. Anesthesia and analgesia Atkinson Ralls, L., Drover, D. R., Clavijo, C. F., Carvalho, B. 2011; 113 (2): 251-258

    Abstract

    A potential physicochemical interaction between epidural local anesthetics and extended-release epidural morphine (EREM) could negate the sustained release. In this study, we sought to determine the pharmacokinetic and drug effects of prior epidural lidocaine administration on EREM.Thirty healthy women undergoing cesarean delivery were enrolled in this randomized study. Patients received 8 mg EREM 1 hour after either a combined spinal-epidural (intrathecal bupivacaine and fentanyl 20 μg with no epidural medication; group SE) or an epidural anesthetic (epidural 2% lidocaine with fentanyl 100 μg; group E). Maximal concentration (Cmax), time to Cmax (Tmax), and AUC(0-last) (area under the concentration-time curve until the last plasma concentration that was below the limit of quantitation) for morphine levels were determined from a plasma sample at 0, 5, 10, 15, and 30 minutes, and 1, 4, 8, 12, 24, 36, 48, and 72 hours. Drug effects including pain, analgesic use, and side effects were measured for 72 hours after cesarean delivery.Epidural lidocaine administration (20-35 mL) 1 hour before epidural EREM administration increased the Cmax in group E (11.1 ± 4.9) compared with group SE (8.3 ± 7.1 ng/mL) (P = 0.038). There were no significant effects on Tmax and AUC(0-last) of venous morphine between the groups (P > 0.05). There was an increased incidence in vomiting, oxygen use, and hypotension in group E (patients who received lidocaine before EREM).A large dose of epidural lidocaine 1 hour before EREM administration alters the pharmacokinetics and drug effects of EREM. Clinicians must apply caution when EREM is administered even 1 hour after an epidural lidocaine "top-up" for cesarean delivery.

    View details for DOI 10.1213/ANE.0b013e318222f59c

    View details for PubMedID 21642610

  • Prior Epidural Lidocaine Alters the Pharmacokinetics and Drug Effects of Extended-Release Epidural Morphine (DepoDur (R)) After Cesarean Delivery ANESTHESIA AND ANALGESIA Ralls, L. A., Drover, D. R., Clavijo, C. F., Carvalho, B. 2011; 113 (2): 251-258
  • The Association Between Thromboelastographic Parameters and Total Estimated Blood Loss in Patients Undergoing Elective Cesarean Delivery ANESTHESIA AND ANALGESIA Butwick, A., Ting, V., Ralls, L. A., Harter, S., Riley, E. 2011; 112 (5): 1041-1047

    Abstract

    In this study, we assessed the relationship between coagulation parameters using kaolin-activated thromboelastography (TEG®) and total estimated blood loss (EBL) in patients undergoing elective cesarean delivery (CD).TEG® parameters were recorded in 52 patients before and after elective CD. Laboratory markers of coagulation (prothrombin time, activated partial thromboplastin time, fibrinogen) were also assessed in a smaller subset (21 patients). Correlation and linear regression analysis was used to assess the relationship among TEG® parameters, relevant clinical variables, and total EBL. Secondary analysis included comparisons of TEG® and coagulation profiles pre-CD versus post-CD.EBL weakly correlated with percentage change in maximum amplitude (r=0.3; P=0.04) and post-CD maximum rate of thrombus generation (r=0.31; P=0.02). Post-CD values for split point, reaction time, time to maximum rate of thrombin generation, prothrombin time, and activated partial thromboplastin time were significantly increased compared with baseline values (P<0.05). Post-CD α angle, maximum amplitude, total thrombus generation, fibrinogen, and platelet counts were significantly decreased compared with baseline values (P<0.05).There is a weak association between clot strength (as assessed by kaolin-activated TEG®) and EBL in patients undergoing elective CD under neuraxial anesthesia, and a modest reduction in the degree of maternal hypercoagulability occurs in the early postpartum period after elective CD.

    View details for DOI 10.1213/ANE.0b013e318210fc64

    View details for Web of Science ID 000289785100009

    View details for PubMedID 21474664

  • ED50 and ED95 of Intrathecal Bupivacaine in Morbidly Obese Patients Undergoing Cesarean Delivery ANESTHESIOLOGY Carvalho, B., Collins, J., Drover, D. R., Ralls, L. A., Riley, E. T. 2011; 114 (3): 529-535

    Abstract

    It has been suggested that morbidly obese parturients may require less local anesthetic for spinal anesthesia. The aim of this study was to determine the effective dose (ED(50)/ED(95)) of intrathecal bupivacaine for cesarean delivery in morbidly obese patients.Morbidly obese parturients (body mass index equal to or more than 40) undergoing elective cesarean delivery were enrolled in this double-blinded study. Forty-two patients were randomly assigned to receive intrathecal hyperbaric bupivacaine in doses of 5, 6, 7, 8, 9, 10, or 11 mg (n = 6 per group) coadministered with 200 μg morphine and 10 μg fentanyl. Success (induction) was defined as block height to pinprick equal to or more than T6 and success (operation) as success (induction) plus no requirement for epidural supplementation throughout surgery. The ED(50)/ED(95) values were determined using a logistic regression model.ED(50) and ED(95) (with 95% confidence intervals) for success (operation) were 9.8 (8.6-11.0) and 15.0 (10.0-20.0), respectively, and were similar to corresponding values of a nonobese population determined previously using similar methodology. We were unable to measure ED(50)/ED(95) values for success (induction) because so few blocks failed initially, even at the low-dose range. There were no differences with regard to secondary outcomes (i.e., hypotension, vasopressor use, nausea, and vomiting).Obese and nonobese patients undergoing cesarean delivery do not appear to respond differently to modest doses of intrathecal bupivacaine. This dose-response study suggests that doses of intrathecal bupivacaine less than 10 mg may not adequately ensure successful intraoperative anesthesia. Even when the initial block obtained with a low dose is satisfactory, it will not guarantee adequate anesthesia throughout surgery.

    View details for DOI 10.1097/ALN.0b013e318209a92d

    View details for Web of Science ID 000287660300012

    View details for PubMedID 21307769