TY - JOUR
T1 - The association between propofol-induced loss of consciousness and the SNAP™ index
AU - Wong, Cynthia A.
AU - Fragen, Robert J.
AU - Fitzgerald, Paul C.
AU - McCarthy, Robert J.
PY - 2005/1
Y1 - 2005/1
N2 - The SNAP™ is a processed electroencephalogram monitor that uses an algorithm based on low- and high-frequency spectral components to derive a SNAP™ index. In this study we sought to determine the relationship of the SNAP™ index with loss of consciousness in subjects receiving a bolus of propofol. Unpremedicated subjects were randomized to receive 1 of 11 doses of IV propofol (0, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, or 2.4 mg/kg; n = 20 per group). The SNAP™ index was recorded when the subject became unconscious (end-point) or at 160 s after the injection. Sixty-five percent of subjects achieved the end-point (defined as the time at which the subject dropped a weighted syringe). The 50% effective dose for propofol was 0.97 mg/kg (95% confidence interval [CI], 0.86-1.07 mg/kg). The median awake SNAP™ index was 92 (range 78-99) and did not differ between subjects who reached the end-point and those who did not. The end-point SNAP™ index decreased from baseline in the subjects who dropped the syringe to a median of 76 (range, 57-94) at doses ≥ 1.0 mg/kg but was not different among doses. The index was not different from baseline at 160 s in subjects who did not reach the end-point. Binary logistic regression models predicted a SNAP™ index 95% effective dose for loss of consciousness of 71 (95% CI, 63-74) and 19 (95% CI, 16-22) for changes in SNAP™ index from baseline. The areas under the receiver operator characteristic curves for these models were 0.837 and 0.864. The SNAP™ index correlated with propofol-induced loss of consciousness. It appears to be a useful indicator of loss of consciousness and should be further investigated as a monitor of anesthesia depth.
AB - The SNAP™ is a processed electroencephalogram monitor that uses an algorithm based on low- and high-frequency spectral components to derive a SNAP™ index. In this study we sought to determine the relationship of the SNAP™ index with loss of consciousness in subjects receiving a bolus of propofol. Unpremedicated subjects were randomized to receive 1 of 11 doses of IV propofol (0, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, or 2.4 mg/kg; n = 20 per group). The SNAP™ index was recorded when the subject became unconscious (end-point) or at 160 s after the injection. Sixty-five percent of subjects achieved the end-point (defined as the time at which the subject dropped a weighted syringe). The 50% effective dose for propofol was 0.97 mg/kg (95% confidence interval [CI], 0.86-1.07 mg/kg). The median awake SNAP™ index was 92 (range 78-99) and did not differ between subjects who reached the end-point and those who did not. The end-point SNAP™ index decreased from baseline in the subjects who dropped the syringe to a median of 76 (range, 57-94) at doses ≥ 1.0 mg/kg but was not different among doses. The index was not different from baseline at 160 s in subjects who did not reach the end-point. Binary logistic regression models predicted a SNAP™ index 95% effective dose for loss of consciousness of 71 (95% CI, 63-74) and 19 (95% CI, 16-22) for changes in SNAP™ index from baseline. The areas under the receiver operator characteristic curves for these models were 0.837 and 0.864. The SNAP™ index correlated with propofol-induced loss of consciousness. It appears to be a useful indicator of loss of consciousness and should be further investigated as a monitor of anesthesia depth.
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U2 - 10.1213/01.ANE.0000138057.61904.FD
DO - 10.1213/01.ANE.0000138057.61904.FD
M3 - Article
C2 - 15616068
AN - SCOPUS:10944240543
SN - 0003-2999
VL - 100
SP - 141
EP - 148
JO - Anesthesia and analgesia
JF - Anesthesia and analgesia
IS - 1
ER -