Evaluation of cerebral autoregulation in dogs via transcranial color-coded duplex sonography and transient hyperemia testing

Objective: To evaluate the changes in flow velocities of the middle cerebral artery before and after a carotid compression maneuver using transcranial color-coded duplex sonography (TCCD) in healthy anesthetized dogs under mechanical ventilation.

Design: Prospective study.

Setting: University teaching hospital.

Animals: Eleven healthy adult dogs.

Interventions: A 5-second carotid occlusion maneuver was performed to evaluate cerebral autoregulation (CA).

Measurements and main results: After 10 minutes of stable anesthesia, the middle cerebral artery was evaluated by TCCD. Dogs were positioned in sternal recumbency with the head raised to the level of the phlebostatic axis. The systolic peak velocity (Vp) was measured using pulsed Doppler mode. CA was evaluated through the transient hyperemia test (THT), which assesses changes in the Vp after a 5-second transient compression of the ipsilateral common carotid artery and is expressed as the ratio between the Vp flow before and after carotid compression. The Vp before and after carotid occlusion was compared using the Wilcoxon signed-rank test. The median Vp of the middle cerebral artery after the carotid compression maneuver was significantly higher than the median Vp before compression (median [interquartile range, IQR]: 47.7 cm/s [34.3] vs 64.1 cm/s [24.4]; P = 0.003). The median THT obtained was 1.20 (IQR: 0.37).

Conclusions: The current study demonstrated a significant increase in the Vp of the middle cerebral artery after a 5-second temporary occlusion of the ipsilateral carotid artery in healthy anesthetized dogs under mechanical ventilation. These findings suggest that the noninvasive TCCD methodology could be valuable for assessing CA in dogs. Additional studies using this technique in neurocritical animals are required to confirm its usefulness.