question: STUDY OBJECTIVE To study changes in BIS values and metabolic parameters during an infusion of isoproterenol in pediatric patients. DESIGN Retrospective study approved By Committee For The Protection Of Human Subjects at University Of Texas Medical School at Houston. SETTING University-affiliated children's hospital. MEASUREMENTS The records of pediatric patients undergoing general anesthesia for electrophysiology procedures were analyzed. Electronic data collected included Bispectral Index (BIS) values, anesthetics (eg, opioids, expired concentration of inhaled anesthetics, muscle relaxants), hemodynamic values (ie, heart rate, invasive blood pressure), respiratory parameters [ie, tidal volume, respiratory rate, end-tidal CO2 (ETCO2)], and routine arterial blood gases. These parameters were analyzed 10 minutes prior to the start of the isoproterenol infusion (T-pre) and 10 minutes after isoproterenol had reduced the cardiac cycle length by 20% (T-infusion). MAIN RESULTS Of the 29 records that were screened, 22 met the above criteria (mean age 13 ± 5 yrs). BIS values increased by an average of 8 (33 ± 8 to 41 ± 10; P < 0.001) during the isoproterenol infusion. Statistically significant increases in ETCO2 (median 33 - 36 mmHg; P = 0.01), PaCO2 (35 - 38 mmHg; P = 0.002), and lactate (1.1 -1.5 mg/dL; P < 0.001) occurred with infusion of isoproterenol. Patients undergoing controlled mechanical ventilation showed an increase in ETCO2 (mean 34 ± 6 mmHg to 37 ± 5 mmHg; P = 0.001) whereas those breathing spontaneously had an increase in minute ventilation (average increase 111 ± 30 mL/kg). CONCLUSIONS Isoproterenol increases metabolic, respiratory, and BIS values in pediatric patients during general anesthesia. We recommend the use of BIS, close monitoring of ETCO2, and careful titration of anesthetics during isoproterenol infusion, especially when lighter planes of general anesthesia are requested for pediatric electrophysiologic procedures.