Effects Of Anesthetic-induced Hypotension On Regional Cerebral Oxygen Saturation Of Elderly Patients Undergoing General Anesthesia

Objective:To research the effect of different levels of anesthetic-induced hypotension on regional cerebral oxygen saturation during general anesthesia in elderly patients and to explain possible reasons.Methods:A total of 63 elderly patients were selected from those who underwent selective lower limb surgery with general anesthesia from August 2019 to December 2019 at the Zhongda Hospital affiliated to Southeast University according to the inclusion and exclusion criteria.The group was divided according to the degree of MAP decline after anesthesia induction.The decline of MAP<20%of baseline was group A（no hypotension after anesthesia induction）,and the decrease of MAP≥20%was group B（hypotension after anesthesia induction）.B group was further divided into group B₁（20%≤the decrease of MAP<30%）,group B₂（30%≤the decrease of MAP<40%）and group B₃（the decrease of MAP≥40%）.Among the included patients,1 patient had persistent and uncorrectable hypotension during operation and another 2patients were transferred to intensive care unit after operation.60 patients were included in the end.Patients were visited within 24 hours before surgery.General data were recorded including age,gender,height,weight,grade of ASA,past medical history,etc.Patients were electrocardiograph monitored routinely after entering operation room.Venous channels were established to infuse balanced salt solution.Percutaneous transradial artery approaches were set up to monitor arterial blood pressure（IBP）in patients.Patients made an arterial blood gas analysis to measure preoperative arterial partial pressure of carbon dioxide（Pa CO₂）and hemoglobin（Hb）.Heart rate（HR）,electrocardiogram（ECG）,pulse oxygen saturation（Sp O₂）,regional cerebral oxygen saturation（rSO₂）and body temperature were also monitored.HR,rSO₂,Et CO₂,Sp O₂ and other indicators were recorded at the time of the patients entering the room（T₁）,finishing anesthesia induction（T₂）,finishing endotracheal intubation（T₃）,30minutes after the beginning of operation（T₄）,1hour after the beginning of operation（T₅）and at the end of the operation（T₆）.Data were collected and analyzed by using SPSS 22.0.Results:1.General situation:There were no statistically significant differences between the two groups in age,weight,BMI,hemoglobin concentration,diabetes history and neurological disease history（P>0.05）.Compared with group A,patients in group B were lower in height,with a higher proportion of women,and a higher proportion of patients with history of hypertension.（P<0.05）.2.30 of the 60 patients had hypotension after induction of anesthesia,with an incidence of50%.Among the patients with hypotension,16 had a decrease in MAP of 20%-30%（group B₁）,accounting for 53.3%of patients with hypotension,9 had a decrease in MAP of 30%-40%（group B₂）,accounting for 30%of patients with hypotension,and 5 had a decrease in MAP of≥40%（group B₃）,accounting for 16.7%of patients with hypotension.3.Compared with T₁,the rSO₂ values of patients were increased at T₃,T₄,T₅ and T₆（P<0.05）;Compared with T₂,the rSO₂ values of T₄,T₅ and T₆ increased differently（P<0.05）.Compared with T₁,the MAP of patients decreased in T₂,T₃,T₄,T₅ and T₆（P<0.05）.Compared with T₂,the MAP of patients was increased in T₃,T₄,T₅ and T₆（P<0.05）.Compared with T₁,the Et CO₂of patients decreased significantly at T₂（P<0.05）.Compared with T₂,the Et CO₂ of patients was increased in T₃,T₄,T₅ and T₆（P<0.05）.Compared with T₁,the HR of patients decreased significantly at T₂,T₄,T₅ and T₆（P<0.05）.Compared with T₂,the HR of patients was increased in T₃ and T₅（P<0.05）.The HR of patients decreased after anesthesia induction and increased after endotracheal intubation.4.At time points T₁,T₂ and T₃,there were differences in rSO₂ values between the two groups（P<0.05）.There was no difference in the increase of rSO₂values at T₁,T₂and T₃in group A（P>0.05）while rSO₂ values were increased in group B（P<0.05）.There was no significant difference in rSO₂values between group A and group B at T₁,T₂ and T₃（P>0.05）.There was no significant difference in rSO₂ values between group B₁,group B₂ and group B₃ at T₁,T₂ and T₃ time points（P>0.05）.5.Baseline rSO₂ was positively correlated with preoperative hemoglobin,with a correlation coefficient of 0.422,which was moderately correlated.Baseline rSO₂was negatively correlated with age,with a correlation coefficient of 0.464,which was moderately correlated.Baseline rSO₂ was independent of gender.Conclusions:1.Hypotension during anesthesia induction is one of the most common perioperative complications,with an incidence of up to 50%in elderly patients.2.Hypotension during anesthesia induction does not make a significant decrease in rSO₂.It may be based on the neurovascular coupling and the integrity of brain automatic regulation function.Hypotension in different levels caused by anesthesia induction also does not make a significant decrease in rSO₂.The application of rSO₂ monitoring on elderly patients undergoing general anesthesia surgery can provide more accurate assessment for anesthesiologists.3.The baseline of rSO₂ was positively correlated with preoperative hemoglobin concentration,while it was negatively correlated with age and it was not correlated with gender.