Cerebral Blood Oxygen Supply Response To Controlled Low Central Venous Pressure During Open Hepatectomy

Objective To survey the influence of controlled low central venous pressure（CLCVP）on cerebral oxygen saturation and internal carotid artery blood flow in patients undergoing open hepatectomy,and to clarify the effects and causes of CLCVP on cerebral blood oxygen supply in patients undergoing hepatectomy,so as to provide evidence for reducing postoperative complications and promoting rapid recovery of patients.Methods Our study is an observational clinical trial without control groups.Thirty patients undergoing elective open hepatectomy were included,age 18-60 years,BMI 18-30 kg/m²,ASA classification II-III,Child-Pugh classification A,of any gender and expected 2-4 hours’s operation time.All patients included in the study strictly restricted from drinking and fasting without additional infusion.After entering the operating room,peripheral venous access was established and invasive arterial pressure（IBP）,electrocardiogram（ECG）,pulse oxygen saturation（Sp O₂）and BIS index were continuously monitored.Cardiac output（CO）and stroke output（SV）were monitored by Vigileo microhemodynamic monitor.After anesthesia,central venous access was established and central venous pressure（CVP）was monitored.The infusion rate of fluid was strictly restricted to 1-2 ml·kg^-1·h^-1 before hepatectomy.During CLCVP,nitroglycerin was injected with 0.5-1.5 ug·kg^-1·min^-1,and 5-10 mg fursamide was given to ensure the CVP was controlled to less than 5 cm H₂O and was restored to more than 5cm H₂O after hepatectomy.Peak systolic velocity,end diastolic velocity and vessel diameter of the left internal carotid artery were measured by doppler ultrasound at the following time points:before anesthesia induction（T₀）,5 min after anesthesia induction（T₁）,5 min after head-up tilt（T₂）,5 min and 15 min after CVP reaching the target(T_3、4),and 5 min after CVP restoring the base value（T₅）.Mean velocity and internal carotid artery blood flow were calculated.Cerebral oxygen saturation was monitored continuously.Heart rate（HR）,mean arterial blood pressure（MAP）,cardiac output（CO）,stroke volume（SV）,end-tidal carbon dioxide(P_ETCO₂)and maximum airway pressure(P_max)at T₀-T₅ were recorded simultaneously,and the incidence of adverse events related to cerebral ischemia were followed up 7 days after surgery.Results Our study included thirty patients underwent open hepatectomy,two patients had MAP<60 mm Hg for more than 5 min during the operation,and one patient failed to reach the target CVP value.27 patients were actually included in the analysis,and no adverse events related to cerebral ischemia occurred 7 days after surgery.Compared with T₀,internal carotid artery blood flow,vessel diameter,mean velocity,HR,MAP,CO and SV were decreased at T_1-2（P<0.05）,cerebral oxygen saturation had no significant change（P>0.05）;cerebral oxygen saturation,internal carotid artery blood flow,vessel diameter,mean velocity,CO and SV were further declined at T_3-4（P<0.05）,and there was no statistically significant difference of P_ETCO₂and P_maxat all time points（P>0.05）.Multiple regression analysis attributed the fall in cerebral oxygen saturation to the decrease in CO（P<0.001）and the fall in internal carotid artery blood flow to the decrease in CO and MAP（P<0.001）.CO independently affects internal carotid artery blood flow.Conclusion During hepatectomy,cerebral oxygen saturation and internal carotid artery blood flow declined with CLCVP.The fall of cerebral oxygen saturation in close association with reductions in CO.The fall of internal carotid artery blood flow in close association with reductions in CO and MAP.CO mainly affects cerebral blood oxygen supply.