Quantitative EEG Monitoring Reduces Postoperative Nausea and Vomiting in
Nonsmoking Patients Undergoing Laproscopic Tubal Ligation
Scott F. Cassingham, M.D.; Jason Harrel, M.D.; Pete Alaniz, M.D.; Paul
George, M.D.; Liz Munsterman, MSNA, CRNA; Christina Smith, MSNA,
CRNA; Sanjay Kaji and Derek Sadler
Louisiana State University Health Science Center in Shreveport, Louisiana,
Department of Anesthesiology

Introduction: This study uses quantitative EEG (QEEG) monitoring to assess anesthetic depth during laproscopic tubal ligation to determine the effect on postoperative nausea and vomiting. Previous studies have documented the efficacy of processed QEEG monitoring in decreasing anesthetic usage and minimizing complications, including postoperative nausea and vomiting (1). Unlike previous studies, this study includes only non-smoking patients.
Method: Following IRB approval, this study randomly assigned 13 ASA I or II non-smoking subjects to QEEG monitoring, group A, n=7, or control, group B, n=5. One control subject was excluded due to complaints of nausea prior to induction. Group A received an Isoflurane/65% N2O/35% O2 anesthetic titrated by QEEG. QEEG monitoring was performed with the Physiometrix PSA 4000. The PSA 4000 expresses the QEEG as the Patient State Index (PSI). PSI range from 0, indicating EEG burst suppression, to 100, indicating full consciousness. A PSI less than or equal to 50 is indicative of an anesthetic depth
sufficient to ensure amnesia. Group B received an Isoflurane/65% N2O/35% O2 anesthetic titrated by standard clinical methods. Premedication, 0.04mg/kg midazolam, and induction agents, 4mg/kg sodium pentothal, 1.5mcg/kg fentanyl, and 1mg/kg rocuronium, were identical in both groups. Muscle relaxation was reversed with 0.05mg/kg neostigmine and 0.6mg atropine in all patients. Postoperative personnel were blinded to anesthetic titration methods.
Results: All subjects experienced an unremarkable operative course. QEEG titration in Group A resulted in a 14% incidence of postoperative nausea and vomiting compared to 20% for the control group. One of seven subjects from group A and one of five controls, Group B experienced nausea followed by emesis. Both patients who experienced nausea and vomiting responded to IV phenergan without further complaint. None of the remaining patients in either group experienced nausea without emesis. Discussion: This study is the first to exclude smoking as a confounding variable in assessing the efficacy of QEEG monitoring in reducing postoperative nausea and vomiting. To avoid the anti-emetic benefit of propofol, sodium pentothal was used as the primary induction agent. Preliminary results of this ongoing study reveal a 30% reduction of postoperative nausea and vomiting in subjects undergoing QEEG anesthetic titration compared to routine clinical titration methods. Comparing the QEEG titrated group to the 45% standard incidence of postoperative nausea in gynecological laproscopic procedures (2,3) yields a significant 68% reduction in postoperative nausea and vomiting. These early findings support QEEG
monitoring as a method to reduce postoperative nausea and vomiting. The utility of QEEG monitoring will be further investigated as this study achieves full enrollment.
References
1) Drover, Anesthesiology. 97(1) 82-9, 2002;
2) Nelskyla, Anesthesia and Analgesia.
93:1165-9, 2001 3) Ericksson, Acta Anaesthesiol Scand 1995;39:377-80

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