Cerebral hemodynamics changes during retrograde brain perfusion in dogs

Area of Science:

• Cardiovascular Surgery
• Neurology
• Critical Care Medicine

Background:

• Hypothermic circulatory arrest (HCA) is used in cardiac surgery but carries risks of cerebral injury.
• Retrograde cerebral perfusion (RCP) is a technique to mitigate these risks by perfusing the brain during HCA.
• Understanding cerebral hemodynamics during HCA with and without RCP is crucial for patient outcomes.

Purpose of the Study:

• To investigate changes in cerebral hemodynamics during HCA with and without RCP.
• To compare cerebral blood flow velocity (CBFV) and pulsatility index (PI) between HCA groups.
• To assess the impact of RCP on cerebral perfusion and identify potential indicators of ischemic injury.

Main Methods:

• Used trans-cranial Doppler ultrasound (TCD) to measure CBFV and PI in the middle cerebral artery (MCA) of hound dogs.
• Animals underwent cardiopulmonary bypass (CPB), cooling to 18°C, and 2 hours of HCA, with or without RCP.
• Monitored hemodynamic parameters at baseline, during CPB, HCA, and post-arrest periods.

Main Results:

• During HCA with RCP, retrograde blood flow was observed in the MCA.
• CBFV during HCA with RCP was comparable to pre- and post-arrest CPB levels.
• Dogs without RCP exhibited significantly increased CBFV during post-arrest CPB (hyperemia) and later decreased CBFV with increased PI, suggesting ischemic injury.

Conclusions:

• RCP effectively maintains cerebral blood flow during HCA, comparable to baseline CPB.
• HCA without RCP leads to immediate post-arrest hyperemia and subsequent decreased CBFV and increased PI, indicative of potential progressive ischemic injury.
• These findings highlight the neuroprotective benefit of RCP during HCA and suggest TCD parameters can monitor cerebral status.