Pulse transit time shows vascular changes caused by propofol in children

Pulse transit time (PTT) is the time that it takes for the arterial pulse pressure wave to travel from the aortic valve to the periphery. It is a simple noninvasive technique for evaluating vascular changes. This study investigated the vascular changes by propofol during the induction of anesthesia in pediatric patients with the measuring of PTT. Without premedication, 2 mg/kg of propofol was administered intravenously with monitoring of electrocardiogram (ECG) and photoplethysmograph (PPG) in 20 pediatric patients aged 3–7 years. The ECG and PPG data were obtained for 1 min before propofol injection (baseline PTT) and 2 min after administration of propofol in the operating room. The PTT was defined as the time interval from the R-wave on the ECG to the maximum upslope of the corresponding PPG. The PTT was calculated off-line after collecting the data. The mean baseline PTT was 166.2 ± 25.9 ms and maximum PTT after propofol injection was 315.9 ± 64.9 ms (the interval between injection and the peak was 17.3 ± 7.6 s). The PTT after the peak changed variously; most of the patients showed no plateau; the PTT decreased progressively after the peak. The PTT after propofol administration prolonged in short time and rapidly recovered toward to the baseline values in pediatric patients. In conclusion, the baseline PTT in children is shorter comparing with adults and the vasodilatory effect of propofol on the vessels as described by the PTT was rapid and the recovery was faster, although the response to propofol was more varied than in adults.