Real-time monitoring of cerebral blood flow by laser speckle contrast imaging after cardiac arrest in rat

Abstract

Cardiac arrest (CA) results in global brain ischemia. To explore the role of cerebral blood flow (CBF) during ischemia, laser speckle contrast imaging (LSCI), a full-field high-resolution optical imaging technique, was used for real-time monitoring of the fluctuations of CBF in a rat model of asphyxial-CA. The temporal changes of CBF were characterized and the relationship between CBF and mean arterial pressure (MAP) was evaluated. Asphyxial-CA led to transient CBF dysregulation, manifested by changes in CBF velocity were significantly impacted by MAP. Hyperemia is aligned with a bolus injection of vecuronium, the first two minutes of asphyxia, the time of epinephrine injection and cardiopulmonary resuscitation, and then lasted for 13 min after the return of spontaneous respiratory (ROSC), followed by hypoperfusion about 55-70% of baseline level no later than 40 min after ROSC. Interestingly, we found that the velocity of venule blood flow increased more than that of the arteriole blood flow during the hyperemia (176% vs 120%). Our study, for the first time, shows real-time CBF changes during and immediately after asphyxial-CA, with high spatial and temporal resolution images. The quantified cerebro-vascular response during the different phases of recovery after CA may underlie the mechanism of injury and recovery after brain ischemia. The study provides a new technique to study the neurovascular coupling and metabolic regulation of CBF after CA.

Fig. 1

CBF representative images at typical time points of events. I: baseline; II: 3 min before asphyxia (washout period); III–V: 1, 4, 7 min after asphyxia; VI–IX: 1, 4, 7, 11 min after ROSC; X–XII; 40 min, 120 min and 30 h after ROSC.

Fig. 2

Passive changes of CBF to MAP from one representative rat. MAP was recorded continuously for more than one hour. CBF was recorded continuously for 30min starting from isoflurane washout and periodically thereafter. There were four MAP surcharges. The first two occurred before CA, corresponding to i.v. bolus injection of vecuronium and asphyxia. The 3^rd one was presented after epinephrine injection and CPR. These three peaks were very brief. The fourth peak lasted for more than 5min after ROSC. CBF is shown in the lower panel, four peaks occurred simultaneously with the four surcharges of MAP.

Fig. 3

Representative changes of vessel diameter during asphyxia CA.