SPECTRAL-ANALYSIS OF ARTERIAL-PRESSURE VARIABILITY DURING INDUCTION OF PROPOFOL ANESTHESIA

We studied the effect of continuous infusion of propofol on spectral c omponents in systemic arterial pressure (SAP) signals in 35 consenting patients undergoing abdominal surgery. Anesthesia was induced with in travenous bolus administration of propofol (2.0 mg/kg), followed by in fusion at either 5 mg . kg(-1) . h(-1) (Group 1, n = 18) or 10 mg . kg (-1) . h(-1) (Group 2, n = 17). Tracheal intubation was facilitated by administration of vecuronium (0.1 mg/kg). The SAP signal was subjecte d to off-line spectral analysis to obtain changes in power of the very low frequency (VLF; 0.00-0.08 Hz), low frequency (LF; 0.08-0.15 Hz), high frequency (0.15-0.25 Hz), and very high frequency (VHF; 0.80-1.60 Hz) components. Venous blood for the measurement of plasma concentrat ion of propofol was collected at 5 min before bolus injection of propo fol; at 5, 10, and 15 min after infusion of propofol; and immediately after endotracheal intubation. Infusion of propofol significantly decr eased the total power of SAP spectrum in both groups, especially the V LF, LF, and VHF components at all intervals except postintubation. Imm ediately after tracheal intubation, patients in Group 1 showed a signi ficant increase in mean arterial pressure when compared with those in Group 2 (118 +/- 5 mm Hg vs 102 +/- 5 mm Hg, P < 0.05). Similar change was also seen in the VLF component (7.4 +/- 0.7 mm Hg-2 vs 4.4 +/- 0. 5 mm Hg-2, P < 0.05). After tracheal intubation, patients in Group 1 s howed 15.7-, 3.3-, and 4.4-fold increase in the VLF, LF, and VHF compo nents, respectively. There were 14.4-, 2.8-, and 2.8-fold increases in the respective components of the SAP signal in Group 2. At all interv als, the spectral components of SAP, however, did not correlate well w ith the plasma concentration of propofol in either group. These result s suggest that spectral analysis of SAP signals may provide an alterna tive for assessing autonomic activities, such as the sympathetic respo nse, to tracheal intubation during propofol anesthesia.