Clinical Focus

  • Anesthesia

Academic Appointments

Professional Education

  • Board Certification: Anesthesia, Saxonian Medical Association (1999)
  • Residency:Dresden-Neustadt Hospital (2002) Germany
  • Residency:Heart Center Dresden (2000) Germany
  • Internship:Herz Jesu Hospital (1999) Germany
  • Medical Education:Philipps University Marburg (1997) Germany

Research & Scholarship

Clinical Trials

  • Measured Hypocretin Levels and Recovery After Hip Surgery Not Recruiting

    A specific group of neurons in the brain produces hypocretin, a peptide which has been established as an important regulator of sleep and wakefulness. Activation of these neurons (increased hypocretin) stabilizes wakefulness; impairing or blocking these neurons (decreased hypocretin) promotes sleep. Evidence suggests that these neurons may be involved in the hypnotic properties of several anesthetics, and play a role in the induction and emergence from anesthesia. In humans there is a considerable inter-individual variability in hypocretin levels. This study aims to investigate how hypocretin levels affect the anesthetic care and recovery of patients undergoing elective hip surgery.

    Stanford is currently not accepting patients for this trial. For more information, please contact Kevin Padrez, (650) 723 - 9433.

    View full details


All Publications

  • Trends and perioperative outcomes for laparoscopic and robotic nephrectomy using the National Surgical Quality Improvement Program (NSQIP) database UROLOGIC ONCOLOGY-SEMINARS AND ORIGINAL INVESTIGATIONS Liu, J., Leppert, J. T., Maxwell, B. G., Panousis, P., Chung, B. I. 2014; 32 (4): 473-479


    We sought to examine the trends in perioperative outcomes of kidney cancer surgery stratified by type (radical nephrectomy [RN] vs. partial nephrectomy [PN]) and approach (open vs. minimally invasive).We queried the National Surgical Quality Improvement Program database to identify kidney cancer operations performed from 2005 to 2011. We examined 30-day perioperative outcomes including operative time, transfusion rate, length of stay, major morbidity (cardiovascular, pulmonary, renal, and infectious), and mortality.A total of 2,902 PN and 5,459 RN cases were identified. The use of PN increased over time, accounting for 39% of all nephrectomies in 2011. Minimally invasive approaches also increased over time for both RN and PN. Open surgery was associated with increased length of stay, receipt of transfusion, major complications, and perioperative mortality. Resident involvement and open approach were independent predictors of major complications for both PN and RN. Additionally, the presence of a medical comorbidity was also a risk factor for complications after RN. The overall complication rates decreased for all approaches over the study period.Minimally invasive approaches to kidney cancer renal surgery have increased with favorable outcomes. The safety of open and minimally invasive PN improved significantly over the study period. Although pathologic features cannot be determined from this data set, these data show that complications from renal surgical procedures are decreasing in an era of increasing use.

    View details for DOI 10.1016/j.urolonc.2013.09.012

    View details for Web of Science ID 000335422300015

    View details for PubMedID 24332644

  • Reinforcement Learning for Closed-Loop Propofol Anesthesia: A Study in Human Volunteers JOURNAL OF MACHINE LEARNING RESEARCH Moore, B. L., Pyeatt, L. D., Kulkarni, V., Panousis, P., Padrez, K., Doufaas, A. G. 2014; 15: 655-696
  • Perioperative Outcomes for Laparoscopic and Robotic Compared With Open Prostatectomy Using the National Surgical Quality Improvement Program (NSQIP) Database UROLOGY Liu, J., Maxwell, B. G., Panousis, P., Chung, B. I. 2013; 82 (3): 579-583


    To examine contemporary outcomes of minimally invasive radical prostatectomy (MIRP) compared with open prostatectomy, using a national, prospective perioperative database reflecting diverse practice settings.The National Surgical Quality Improvement Program database was queried from 2005 to 2010 for laparoscopic or robotic prostatectomy (Current Procedural Terminology code 55866) and open retropubic prostatectomy (Current Procedural Terminology codes 55840, 55842, 55845). Perioperative outcomes examined were surgical and total operation duration, transfusion rates, length of stay, major morbidity (cardiovascular, pulmonary, renal, and infectious), and mortality.The study identified 5319 radical prostatectomies: 4036 MIRP and 1283 open. Although operative time was significantly longer in the MIRP group, there were significantly fewer perioperative blood transfusions and shorter mean length of stay. Major postoperative morbidity and mortality were 5% in the MIRP group and 9% in the open group (P <.001). Age, body mass index, presence of medical comorbidities, and open surgical technique were all independently predictive of major complications and mortality on multivariate analysis.In a nationwide database of diverse medical centers, MIRP was associated with longer operative time, but a significantly decreased rate of blood transfusions, length of stay, perioperative complication rate, and mortality compared with open prostatectomy. The minimally invasive surgical approach was independently associated with significantly fewer complications and deaths on multivariate analysis. Compared with other administrative databases that capture only inpatient events, the National Surgical Quality Improvement Program identifies complications up to 30 days postoperatively, providing more detailed characterization of complications after prostatectomy. These data reflect contemporary practice patterns and suggest that MIRP can be performed with low perioperative morbidity.

    View details for DOI 10.1016/j.urology.2013.03.080

    View details for Web of Science ID 000323790800031

    View details for PubMedID 23876584

  • Experimental Pain and Opioid Analgesia in Volunteers at High Risk for Obstructive Sleep Apnea PLOS ONE Doufas, A. G., Tian, L., Padrez, K. A., Suwanprathes, P., Cardell, J. A., Maecker, H. T., Panousis, P. 2013; 8 (1)
  • Experimental pain and opioid analgesia in volunteers at high risk for obstructive sleep apnea. PloS one Doufas, A. G., Tian, L., Padrez, K. A., Suwanprathes, P., Cardell, J. A., Maecker, H. T., Panousis, P. 2013; 8 (1)


    Obstructive sleep apnea (OSA) is characterized by recurrent nocturnal hypoxia and sleep disruption. Sleep fragmentation caused hyperalgesia in volunteers, while nocturnal hypoxemia enhanced morphine analgesic potency in children with OSA. This evidence directly relates to surgical OSA patients who are at risk for airway compromise due to postoperative use of opioids. Using accepted experimental pain models, we characterized pain processing and opioid analgesia in male volunteers recruited based on their risk for OSA.After approval from the Intitutional Review Board and informed consent, we assessed heat and cold pain thresholds and tolerances in volunteers after overnight polysomnography (PSG). Three pro-inflammatory and 3 hypoxia markers were determined in the serum. Pain tests were performed at baseline, placebo, and two effect site concentrations of remifentanil (1 and 2 µg/ml), an μ-opioid agonist. Linear mixed effects regression models were employed to evaluate the association of 3 PSG descriptors [wake after sleep onset, number of sleep stage shifts, and lowest oxyhemoglobin saturation (SaO(2)) during sleep] and all serum markers with pain thresholds and tolerances at baseline, as well as their changes under remifentanil.Forty-three volunteers (12 normal and 31 with a PSG-based diagnosis of OSA) were included in the analysis. The lower nadir SaO(2) and higher insulin growth factor binding protein-1 (IGFBP-1) were associated with higher analgesic sensitivity to remifentanil (SaO(2), P = 0.0440; IGFBP-1, P = 0.0013). Other pro-inflammatory mediators like interleukin-1β and tumor necrosis factor-α (TNF-α) were associated with an enhanced sensitivity to the opioid analgesic effect (IL-1β, P = 0.0218; TNF-α, P = 0.0276).Nocturnal hypoxemia in subjects at high risk for OSA was associated with an increased potency of opioid analgesia. A serum hypoxia marker (IGFBP-1) was associated with hypoalgesia and increased potency to opioid analgesia; other pro-inflammatory mediators also predicted an enhanced opioid NCT00672737.

    View details for DOI 10.1371/journal.pone.0054807

    View details for PubMedID 23382975

  • Epidural Ropivacaine Concentrations for Intraoperative Analgesia During Major Upper Abdominal Surgery: A Prospective, Randomized, Double-Blinded, Placebo-Controlled Study ANESTHESIA AND ANALGESIA Panousis, P., Heller, A. R., Koch, T., Litz, R. J. 2009; 108 (6): 1971-1976


    The postoperative beneficial effects of thoracic epidural analgesia (TEA) within various clinical pathways are well documented. However, intraoperative data are lacking on the effect of different epidurally administered concentrations of local anesthetics on inhaled anesthetic, fluid and vasopressor requirement, and hemodynamic changes. We performed this study among patients undergoing major upper abdominal surgery under combined TEA and general anesthesia.Forty-five patients undergoing major upper abdominal surgery were randomly assigned to one of three treatment groups receiving intraoperative TEA with either 10 mL of 0.5% (Group 1) or 0.2% (Group 2) ropivacaine (both with 0.5 microg/mL sufentanil supplement), or 10 mL saline (Group 3) every 60 min. Anesthesia was maintained with desflurane in nitrous oxide (60%) initiated at an age-adapted 1 minimum alveolar concentration (MAC) until incision. Desflurane administration was then titrated to maintain an anesthetic level between 50 and 55, as assessed by continuous Bispectral Index monitoring and the common clinical signs (PRST score). Lack of intraoperative analgesia, as defined by an increase in pulse rate, sweating, and tearing (PRST) score >2 or an increase of mean arterial blood pressure (MAP) >20% of baseline, was treated by readjusting the end-tidal concentration of desflurane toward 1 MAC, and above this level by additional rescue i.v. remifentanil infusion. Hypotension, as defined as a decrease in MAP >20% of baseline, was treated by reducing the end-tidal desflurane concentration to a Bispectral Index level of 50-55 and below that with crystalloid or norepinephrine infusion, depending on central venous pressure.End-tidal desflurane concentration could be significantly reduced in Group 1 to 0.7 +/- 0.1 MAC (P < 0.001) and to 0.8 +/- 0.1 MAC (P < 0.001) in Group 2, but not in Group 3. Significant hypotension occurred within 20 min in all patients of Groups 1 and 2 (MAP from 80 +/- 10 to 56 +/- 5) (Group 1), 78 +/- 18 to 58 +/- 7 mm Hg (Group 2), P < 0.01, whereas MAP remained unchanged in Group 3 (74 +/- 12 to 83 +/- 15 mm Hg, P = 0.42). Heart rate did not change significantly over time within any of the groups. Furthermore, groups did not differ significantly regarding i.v. fluid and norepinephrine requirement. Patients in Group 3 received more remifentanil throughout the surgical procedure (7.2 +/- 4.9 mg x kg(-1) x h(-1)) when compared with Group 2 (1.6 +/- 2.2 mg x kg(-1) x h(-1)), P < 0.01. Remifentanil infusion among patients receiving ropivacaine 0.5% was not necessary at any time.Epidural administration of 0.5% ropivacaine leads to a more pronounced sparing effect on desflurane concentration for an adequate anesthetic depth when compared with a 0.2% concentration of ropivacaine at comparable levels of vasopressor support and i.v. fluid requirement.

    View details for DOI 10.1213/ane.0b013e3181a2a301

    View details for Web of Science ID 000266285500044

    View details for PubMedID 19448234