The non-invasive transcranial Doppler for hemodynamic monitoring

The successful development and testing of new thrombolytics in animal models requires monitoring of hemodynamic changes in cerebral circulation before and after stroke. The purpose of the present study was to document that percutaneous transcranial Doppler (TCD) monitoring is able to differentiate two hemodynamic situations induced with two anesthetic protocols. Twelve adult rats divided into two groups underwent general anesthesia (60 min) using combination: 1) ketamine-xylazine-diazepam (KXD); and 2) ketamine-xylazine-urethane-alpha-chloralose (URACH). The TCD was performed with the skin and skull intact. The heart rate, peak systolic velocity, pulsatility index, and resistance index were recorded in a branch of the posterior cerebral artery. Flow detection and measurement was possible in all rat brains bilaterally. The mean heart rate was lower in the KXD 243+/-4 (range: 238 to 249) than in the URACH group 265+/-12 (range: 250 to 279), the difference between means: 22; 95 % CI [8 to 34], p=0.005) only for the first 20 min of monitoring. Peak systolic velocity was lower in the KXD 73.4+/-3.3 mm/s (range 70.3 to 76.5) vs. URACH group 93.7+/-4.0 mm/s (range: 90.0 to 97.4) during the entire observation period (difference between means: 20; 95 % CI [16 to 25], p<0.001). Same difference was observed for pulsatility and resistance indexes. TCD was able to differentiate hemodynamic changes in the rat brains, making the TCD suitable for monitoring of hemodynamic changes and explores, e.g. how such changes contribute to hemorrhagic transformation after thrombolysis. Also, TCD holds promise as a tool for monitoring of recanalization induced by thrombolytics. Key words Non-invasive monitoring " Brain flow velocity " Anesthesia " Animal model.