Mild to severe controlled hypotension with nicardipine can maintain intraoperative microcirculatory cerebral blood flow and oxygenation in pigs

Abstract

Background There have been many studies on global cerebral perfusion level, but less attention has been paid to its effect on cerebral microcirculatory perfusion. This study aimed to investigate the effects of nicardipine-induced hypotension on microcirculatory cerebral blood flow and oxygenation in pigs. Methods Six healthy female Landrace pigs, aged 4–6 months, weighing 22-25kg were included in this study. Nicardipine was used for controlled hypotension (20%, 30%, 50% lower than baseline mean arterial pressure (MAP), corresponding to mild, moderate and severe hypotension, respectively) under sevoflurane anesthesia. Oxygen to see(O2C), a monitoring instrument, was used to measure regional cerebral blood flow (rCBF) and regional cerebral oxygen saturation (rSO₂). rCBF, rSO₂, HR, SpO₂ were recorded under different MAP. Results rCBF was moderately correlated with rSO₂(r = 0.671), while MAP was highly correlated with both rCBF and rSO₂(r = 0.800 and 0.860, respectively) during hypotension. Both rCBF and rSO₂ decreased significantly(P < 0.001) from baseline during mild hypotension, with an average decrease of 6.3% and 2.2%, respectively. During moderate hypotension, rCBF decreased by an average of 11.8% (P < 0.001), while rSO₂ fell by an average of 6.5% (P < 0.001). During severe hypotension, the average decrease of rCBF was 19.5%(P < 0.001), while rSO₂ decreased by an average of 15.7%(P < 0.001). When MAP recovered after drug withdrawal, both rCBF and rSO₂ did not restore, which decreased by 2.7% and 4.3% from baseline, respectively. Conclusions The effect of nicardipine on cerebral microcirculation perfusion is limited during mild to severe hypotension. However, for patients with cerebrovascular diseases, there is a high risk of cerebral ischemia and hypoxia during severe hypotension.