The Application Of Ultrasound To Predict The Epidural Space Depth Of Parturients

Objective:The purpose of this study was to explore the feasibility of predicting epidural space depth measured by ultrasound,and to study the correlation between ultrasound-measured depth(UD)and actual needle insertion depth(ND),investigate whether any correlations exist between these distances and age,body weight,height,body mass index(BMI)so as to provide reference for follow-up clinical research.Methods:Sixty patients aged 20-45 years old,ASA I-II,scheduled for cesarean section were enrolled in the second department of the first hospital of Jilin University(August 2020-March 2021).They were all Chinese people.Exclusion criteria were:spinal deformities,spinal diseases,previous surgery to the lumbar region,and infection of puncture site.The general data were collected,including age,height,weight and BMI,the distance from the skin to the posterior complex(UD)in the L3-4 intervertebral space was measured by ultrasound before operation.All data were obtained by the same anesthesiologist.Then,all procedures were performed by another anesthesiologist with more than 3 years of experience in obstetric anesthesia and did not participate in data acquisition and analysis.The L3-4 intervertebral space was the level selected for the puncture.The epidural space detection was performed by eliciting the loss of resistance to air technique.After the puncture needle reached the epidural space,the distance from the skin to the end of the epidural needle was measured by a sterile steel ruler and ND was recorded.The correlation between UD and ND was analyzed by Pearson correlation coefficient,and the consistency between ND and UD was tested by Bland-Altman analysis.The relationships between ND and general physical indicators were analyzed by multiple stepwise linear regression.Results:A total of 60 parturients participated in this study.Of these,4 patients were excluded because of changing puncture path from transverse median approach to paracentesis approach,2 cases changed the puncture space,and finally 54 patients were included.(1)UD and ND were respectively 5.16±0.41 cm and 5.62±0.54 cm,UN was lesser than ND,and the difference was statistically significant(P<0.05).Pearson correlation analysis suggested that there was a positive correlation between them[r=0.944,P<0.05(95%CI:0.902-0.967].The linear regression equation was ND=-0.805+1.246*UD;and the 95%consistency limit was0.06-0.87.(2)Pearson correlation analysis showed that UD and ND were positively correlated with weight,height and BMI.The correlation coefficients between UD and weight,height and BMI were 0.852,0.734 and 0.761 respectively,and the difference were statistically significant(P<0.05).The correlation coefficients between ND and weight,height and BMI were 0.815,0.700 and0.736 respectively,and the difference was statistically significant(P<0.05).(3)Multiple stepwise regression analysis was carried out with age,height,weight and BMI as independent variables and ND as dependent variable.The results showed that there was no obvious linear relationship between ND and other variables except weight.There was a positive correlation between weight and ND.The correlation coefficient was 0.815,and the regression equation was ND=2.229+0.044*weight(r~2=0.664,r=0.815).Conclusion:There was a positive correlation between ultrasound-measured depth(UD)and actual needle insertion depth(ND).UD and ND were positively correlated with weight,height and BMI.There was a linear and positive correlation between ND and body weight.The needle insertion depth could be predicted in advance by using ultrasound to measure the depth of epidural space.