OBJECTIVE: To evaluate the correlation between the bispectral index (BIS) and end-tidal isoflurane (ET(ISO)) concentration and compare the use of 3 BIS sensor positions in dogs. ANIMALS: 6 adult dogs. PROCEDURES: Mechanically ventilated dogs received pancuronium, and depth of anesthesia was altered by increasing ET(ISO) concentration from 1.5% to 2.3% and 3.0%. The BIS, suppression ratio (relative percentage of isoelectric electroencephalographic waveforms), and signal quality index (SQI) were recorded at each ET(ISO) concentration for each of 3 BIS sensor positions (frontal-occipital, bifrontal, and frontal-temporal positions). RESULTS: The BIS and ET(ISO) concentration were poorly correlated; regardless of sensor positioning, mean BIS values did not change significantly as ET(ISO) was increased. At 3% isoflurane, regardless of sensor positioning, there was an increase in suppression ratio coincident with BIS < 40 in some dogs, whereas paradoxic increases in BIS (> 60) were recorded in others. Furthermore, at 3.0% isoflurane, the SQI was significantly lower for the bifrontal sensor position (compared with values for the other positions), but low SQI values prevented recording of BIS values from the frontal-occipital sensor position in 2 dogs. Overall, BIS values derived from the 3 sensor positions did not differ. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, BIS values may not reflect changes in depth of isoflurane anesthesia in the absence of noxious stimulation. Of the 3 sensor positions, frontal-temporal positioning provided better correlation with changes in depth of anesthesia induced via changes in isoflurane concentrations. However, the sensor placements yielded similar results at SQI values > 50.
OBJECTIVE: To evaluate the correlation between the bispectral index (BIS) and end-tidal isoflurane (ET(ISO)) concentration and compare the use of 3 BIS sensor positions in dogs. ANIMALS: 6 adult dogs. PROCEDURES: Mechanically ventilated dogs received pancuronium, and depth of anesthesia was altered by increasing ET(ISO) concentration from 1.5% to 2.3% and 3.0%. The BIS, suppression ratio (relative percentage of isoelectric electroencephalographic waveforms), and signal quality index (SQI) were recorded at each ET(ISO) concentration for each of 3 BIS sensor positions (frontal-occipital, bifrontal, and frontal-temporal positions). RESULTS: The BIS and ET(ISO) concentration were poorly correlated; regardless of sensor positioning, mean BIS values did not change significantly as ET(ISO) was increased. At 3% isoflurane, regardless of sensor positioning, there was an increase in suppression ratio coincident with BIS < 40 in some dogs, whereas paradoxic increases in BIS (> 60) were recorded in others. Furthermore, at 3.0% isoflurane, the SQI was significantly lower for the bifrontal sensor position (compared with values for the other positions), but low SQI values prevented recording of BIS values from the frontal-occipital sensor position in 2 dogs. Overall, BIS values derived from the 3 sensor positions did not differ. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs, BIS values may not reflect changes in depth of isoflurane anesthesia in the absence of noxious stimulation. Of the 3 sensor positions, frontal-temporal positioning provided better correlation with changes in depth of anesthesia induced via changes in isoflurane concentrations. However, the sensor placements yielded similar results at SQI values > 50.
Authors: Samer M Jaber; Sarah Sullivan; F Claire Hankenson; Todd J Kilbaugh; Susan S Margulies Journal: J Am Assoc Lab Anim Sci Date: 2015-09 Impact factor: 1.232
Authors: Matheus Luis Cunha Ubiali; Guilherme Paes Meirelles; Julia Milczewski Vilani; Henrique Erick da Luz; Sabrine Marangoni; Raisa Braul Rodrigues; Ricardo Guilherme D'OCtaviano de Castro Vilani Journal: Vet World Date: 2022-03-08