ABSTRACT
The sphenopalatine ganglion [SPG] is one of four parasympathetic ganglia in the head. The purpose of this pilot study was to assess the efficacy of blocking the SPG with local anesthetic and its effect on cerebral hemodynamics. Validation of the selected blocking technique and the data obtained in this study will then be used in future studies to understand how opioids may influence the effects of the SPG on the cerebral blood vessels. We hypothesize that blocking the SPG with local anesthetics would lead to a change in the tone of the cerebral vessels and may affect the cerebral blood flow. 1KB approval and informed consent was obtained. This is a double-blinded cross-over pilot study. Five out of ten healthy adult volunteers have been recruited. A cross over between the use of a placebo [normal saline N.S.] and a local anesthetic [Lidocaine, 0.2-0.5 mg/Kg in a liquid form] was administered on the same volunteer to determine changes in cerebral hemodynamics between treatment groups. The attempt to block the SPG was done by the application of a local anesthetic on the intranasal mucosa with continuous monitoring of the cerebral hemodynamics via Trans-cranial Doppler [TCD]. EKG, non-invasive arterial pressure, end-tidal carbon dioxide [PeCO[2]], and oxygen saturation [SpO[2]] were monitored. The ipsilateral middle cerebral artery [MCA] was located through the temporal acoustic window using a 2 MHz TCD. During normal breathing, the baseline values were recorded. Thereafter, pressure was applied for few seconds on the side of the neck to compress the carotid artery followed by sudden release. This maneuver elicits the Transient Hyperemic Response Test [THRT] of the MCA. After the application of one of the treatments via Q-tip on the site of the SPG, the first set of measurements for one hour were recorded, and a second set of measurements were taken for another hour after applying the second medicine. We could not find an effect on the cerebral hemodynaminc when lidocaine was applied on the SPG using a modified transnasal approach. Replication of the modified technique to the traditional transnasal block of the SPG with lidocaine has no effect on cerebral hemodynamic