OBJECTIVE To observe the changes of the liver blood flow in controlled hypotension by transcutaneous electrical acupoint stimulation (TEAS) combined general anesthesia, thus clarifying the mechanism of liver protection effect in acupuncture anesthesia combined with drugs.
Methods: Forty-two male beagles were randomly divided into seven groups, i.e. , the general anesthesia group, the 50% control group, the 50% experiment group, the 40% control group, the 40% experiment group, the 30% control group, and the 30% experiment group, 6 in each group. Beagles in the latter six groups were administered with isoflurane inhalation and intravenous dripping of sodium nitroprusside (SNP) for controlled hypotension. The mean arterial pressure (MAP) was lowered to 50%, 40%, and 30% basic MAP and lasted for 60 min. Beagles in the general anesthesia group was not treated with controlled hypotension. In the experiment groups, TEAS was applied to bilateral Hegu (LI4), Zusanli (ST36), Sanyinjiao (SP6), and Quchi (LI11) at 2/100 Hz with the stimulation strength of 4 +/- 1 mA. The TEAS started from the stability of physiological conditions to 60 min after maintaining the target MAP. The changes of blood flow of the liver tissue surface at corresponding time points were monitored by laser Doppler blood flow meter.
Results: Between the beginning of hypotension and the maintaining stage of target low blood pressure, the liver blood flow of the 50% control group was significantly lower than the level of the general anesthesia group and the basic level at corresponding time points (P < 0.05). It was significantly reduced in the 50% experiment group only at 30-60 min of maintenance. Besides, in the early period of maintenance (10-30 min), it was significantly higher in the 50% experiment group than in the 50% control group at the same time points (P < 0.05). In this stage, there was no obvious increase in the liver blood flow in the 40% and 30% experiment groups. In the recovery phase of blood pressure (20-30 min), the liver blood flow of the 40% experiment group had been restored to the level of the 40% control group and the basic level, while it had not been restored in the general anesthesia group. In this stage, the similar changing tendency of the liver blood flow occurred in the 50% and 30% experiment groups and the 50% and 30% control groups.
Conclusions: Line to a high level of controlled hypotension (50%), TEAS liver protective effect was obviously embodied in the early step-down phase and the maintenance phase. Line-induced hypotension to a lower level (40%), TEAS liver protective effect was obviously embodied in the recovery phase.