The Effects Of Abdominal Girth And Vertebral Column Length On The Spread Of Local Anesthetics In Subarachnoid Space

Objective:The spread of local anaesthetic during spinal anesthesia is highly unpredictable,espically for plain local anaesthetic.Until now,it is still a challenge for anesthetists to predict the spinal spread.In clinic,a great cephalad spread is often observed in the patients with increased abdominal girth and short vertebral column length.Lumbosacral cerebrospinal fluid volume was normally deemed to the key determinant for spinal spread.Thus,we intended to investigate the correlation between abdominal girth,vertebral column length and spinal spread,to investigate the use of abdominal girth and vertebral column length to predict the dose of local anesthetic individually for preestablished spinal spread level,and to investigate the accuracy of abdominal girth and vertebral column length for predicting the dose of local anesthetic for preestablished spinal spread level.We also used the magnetic resonance to measure lumbosacral cerebrospinal fluid volume,and to demonstrat the strong correlation between abdominal girth,vertebral column length and lumbosacral cerebrospinal fluid volume,thus to certify that abdominal girth and short vertebral column length could predict local anesthetic spread in the subarachnoid space in further.Methods:Part Ⅰ.One hundred and fifteen patients received lower limbs srugeries under spinal anesthesia were punctured at the L3/4 interspace and and 3 ml 0.5%plain bupivacaine was injected into the subarachnoid space.The cephalad spread including loss of pinprick discrimination and loss of temperature sensation was assessed 30 min after the intrathecal injection of local anesthetics.The combined linear contribution of age,weight,height,abdominal girth and vertebral column length was tested by multiple regression analysis.Part Ⅱ.A suitable dose of 0.5%plain bupivacaine was administered at the L3/4 interspace during spinal anesthesia for lower limb surgeries.If the upper cephalad spread(loss of pinprick discrimination)was T12 or T10,the patient would be enrolled in this study.If the sample size were both larger than 92 for T12 and T10 upper cephalad spread.Five patient variables including age,weight,height,abdominal girth,vertebral column length and intrathecal plain bupivacaine dose were recorded.Multiple regression analyses were performed between age,weight,height,abdominal girth,vertebral column length and intrathecal plain bupivacaine dose for the regression equation.Part Ⅲ.One hundred and eighty-seven patients scheduled for lower limbs surgery undergoing spinal anesthesia were enrolled.0.5%plain bupivacaine with room temperature was injected intrathecally at the L3/4 interspace.The dose of bupivacaine was based on the regression equation YT10= 3.848+0.047X1-0.046X2(Y,0.5%plain bupivacaine volume;X1,vertebral column length;and X2,abdominal girth).Block level was measured 30 min after spinal anesthesia.The upper block level for loss of pinprick discrimination was recorded.Part Ⅳ.Forty five healthy volunteers were enrolled in this study for lumbosacral cerebrospinal fluid volume measurement(from T12/T1 intervertebral disk to S5)by magnetic resonance.At first,T2WI sequence was used to locate the T12/T1 intervertebral disk and S5 at sagittal plane.Second,MRM sequence was used for cerebrospinal fluid scanning imaging,and then the magnetic resonance imaging was postprocessed and lumbosacral cerebrospinal fluid volume was measured.Multiple linear regression analysis was used to analyze the correlation between age,weight,height,abdominal girth,vertebral column length and lumbosacral cerebrospinal fluid volume.Results:Part Ⅰ.One hundred and fourteen patients enrolled in this study in the end,and one patient was excluded from this study because of subarachnoid space puncture failure.Multiple linear regression analysis showed that abdominal girth and vertebral column length had a strong correlation with the spread of local anaesthetic in subarachnoid space(both P<0.001),while age,weight and height had low correlation with the spread of local anaesthetic in subarachnoid space(all P>0.059).The determination coefficient(R2)was 0.792 for the lose of pinprick discrimination and 0.805 for the lose of temperatue sensation,respectively.Part Ⅱ.Totals of 121 patients and 111 patients who lost pinprick discrimination at T10 and T12 were enrolled in this study,respectively.Multiple linear regression analysis showed that abdominal girth and vertebral column length were the key determinants of plain bupivacaine dose for T10 and T12 spinal spread(both p<0.0001).while age,weight and height had low correlation with plain bupivacaine dose for T10 and T12 spinal spread(all P>0.164).The two regression equations were YT1O = 3.848+0.047X1-0.046X2 and YT12= 3.547+0.045Xi-0.044X2(Y,0.5%plain bupivacaine volume;X1,vertebral column length:and X2,abdominal girth).The determination coefficient(R2)was 0.860 and 0.874 for the loss of pinprick discrimination at T10 and T12,respectively.Part Ⅲ.A total of 185 patients were enrolled in this study.Two patients were unsuccessful puncture at L3/4 intervertebral space and excluded from this study.Results shown that 144 patients with the T10 spinal spread,accounted for 77.5%of all patients.The upper spinal spread was T8,the lowest spinal spread was T12.The spread level is higher than T10 in 14 patients(7.7%),and the spread level is lower than T10 in 23 patients(13.6%).Part IV.A total of 43 volunteers were enrolled in this study and two volunteers were excluded because of lumbar disc herniation.Multiple linear regression analysis shown that there is a strong correlation between abdominal girth,vertebral column length and lumbosacral cerebrospinal fluid volume(both P<0.01).Age,weight and height only have small correlation with lumbosacral cerebrospinal fluid volume(all P>0.190).The determination coefficient(R2)was 0.644.Conclusion:Abdominal girth and vertebral column length have a high predictive value for the spread of 0.5%plain bupivacaine.They can acculately predict the 0.5%plain bupivacaine dose for an established spinal spread level.The regression equations between vertebral column length,abdominal girth and intrathecal plain bupivacaine dose for the loss of pinprick discrimination at T12 and T10 were YT12=3.547+0.045X1-0.044X2 and YT10=3.848+0.047X1-0.046X2(Y,0.5%plain bupivacaine volume;X1,vertebral column length;and X2,abdominal girth),separately.The regression equation ’for T10 was proved accuracy in clinic.Abdominal girth and vertebral column length have a high correlation with spinal spread maybe because they have a high correlation with lumbosacral cerebrospinal fluid volume.