- Email: [email protected]
Effect of Lumbar Flexion on the Extent of Epidural Blockade
Effect of Lumbar Flexion on the Extent of Epidural Blockade Jin-Tae Kim, M.D., Jong-Hwan Lee, M.D., Seung-Zhoo Yoon, M.D., Young-Jin Lim, M.D., Jae-Hyon Bahk, M.D., Chong-Sung Kim, M.D., and Yunseok Jeon, M.D. Background and Objectives: This study examined the effect of lumbar flexion on the extent of the epidural block during lumbar epidural anesthesia. Methods: The epidural catheter was introduced at the L3-4 interspace with the patient in the lateral decubitus position with the surgical side down. After administering a test drug (3 mL of 2% lidocaine and 15 g of epinephrine), the patients were randomly allocated to 1 of 2 groups: Group F (n ⫽ 16, lumbar spine flexed) and Group N (n ⫽ 17, lumbar spine in the neutral position). In both groups, 2% lidocaine (16 mL) mixed with sodium bicarbonate (2 mL) was administered through the epidural catheter while the patient maintained the lateral decubitus position with the lumbar spine either flexed or in the neutral position. All the patients maintained their respective positions for 5 minutes and were subsequently turned to the supine position. The pinprick block level and the degree of motor blockade were assessed every 10 minutes for 60 minutes after administering the local anesthetics. A 2-dermatomal difference in uppermost block between groups was determined to be clinically significant. Results: The median difference between groups in the uppermost pinprick block level was only 1.5 dermatomes and it did not satisfy our criteria for clinical significance. There were no significant differences between the 2 groups in the lowermost pinprick block level and the degree of motor block. Conclusions: Lumbar flexion has no clinically relevant effect on sensory spread during epidural anesthesia. Reg Anesth Pain Med 2007;32:471-474. Key Words:
Anesthesia, Epidural, Lidocaine, Lumbar flexion.
T
he extent of epidural anesthesia is correlated with the spread of local anesthetic solution,1 which in turn may be affected by variations in the epidural space consequent to lumbar flexion. For example, lumbar flexion significantly increases the spinal canal area and the intervertebral foraminal size.2-4 Furthermore, compared with extension, the pressure in the lumbar epidural space is lower after flexing the lumbar spine.5 This suggests that flexion of the spine during epidural anesthesia may influ-
From the Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, Korea. Accepted for publication April 13, 2007. Presented in part at the annual meeting of the Korean Society of Anesthesiologists, Seoul, Korea, November 4, 2006. Reprint requests: Yunseok Jeon, M.D., Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul National University College of Medicine, #28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Korea. E-mail: jeonyunseok@gmail. com © 2007 by the American Society of Regional Anesthesia and Pain Medicine. 1098-7339/07/3206-0001$32.00/0 doi:10.1016/j.rapm.2007.04.010
ence the distribution of local anesthetic and the extent of the blockade. For safe and effective epidural analgesia, it is important to control the level of anesthesia and to identify factors that influence its spread. We have observed that neck flexion and extension significantly affect the distribution of contrast medium in the epidural space at the high thoracic level.6 During epidural anesthesia, local anesthetic is injected into the epidural space with either the lumbar spine flexed or in the neutral position. However, the effect of lumbar flexion on the spread of lumbar epidural anesthesia is unknown. We hypothesized that flexion of the lumbar spine would influence the spread of local anesthetic in the epidural space. This study was performed to evaluate whether lumbar flexion influenced the spread of neuraxial blockade during epidural anesthesia.
Methods After obtaining approval of our Institutional Review Board and written informed consent from patients, 36 male patients with American Society of
Regional Anesthesia and Pain Medicine, Vol 32, No 6 (November–December), 2007: pp 471–474
471
472
Regional Anesthesia and Pain Medicine Vol. 32 No. 6 November–December 2007
Anesthesiologists physical status I were enrolled in this study. The patients were scheduled to undergo elective knee arthroscopy under epidural anesthesia without premedication. The patients were monitored with automated noninvasive blood pressure, electrocardiography, and pulse oximeter. The patients were positioned in the lateral decubitus position with the surgical side down and the hip flexed. The same anesthesiologist (J.-T.K.) performed all epidural catheterizations. After confirming the epidural space using the loss of resistance technique, an epidural catheter was inserted 3 cm through an 18-gauge Tuohy needle with the bevel facing cephalad at the L3-4 interspace. After a test dose (3 mL of 2% lidocaine and 15 g of epinephrine) was injected into the epidural space, the patients were randomly allocated to 1 of 2 groups of 18 patients each using a computer-generated randomization list: lumbar spine flexion group (Group F) and lumbar spine neutral group (Group N). In Group F, the patients maintained the lateral decubitus position with their spines and hips flexed. In Group N, the patients were requested to extend their spine and hips to achieve normal lumbar lordotic curvature. In both groups, a mixed solution of 2% lidocaine 16 mL and 8.4% sodium bicarbonate 2 mL was administered as a single bolus over approximately 60 seconds through an epidural catheter in their respective position. After injection of local anesthetic, all patients maintained their respective position for 5 minutes and then were turned to the supine position. The uppermost pinprick block levels were checked on the dependent midclavicular lines, and the lowermost pinprick block levels were checked only on the nondependent side to avoid the interruption of surgery every 10 minutes for 60 minutes after administering lidocaine. The degree of motor blockade was also assessed every 10 minutes using the modified Bromage scale (0, no block; 1, inability to raise the extended legs; 2, inability to flex the knee; 3, inability to flex the ankle, defined as complete motor block). The second anesthesiologist (Y.J.), who was blinded to the patient grouping, checked the epidural block dermatomal level. Mean arterial blood pressure and heart rate were monitored throughout the operation but only data up to 60 minutes were included in the data analysis. Atropine 0.5 mg was injected when heart rate fell to below 45 beats per minute and 10 mg of ephedrine was injected if the systolic blood pressure decreased to less than 90 mm Hg. The patient was excluded from the statistical analysis if general anesthesia or the additional administration of anesthetics were performed because of pain.
For the purpose of statistical analysis, each dermatomal level was assigned a segmental number such as “lower than S3,” and S3 ⫽ 1, S2⫽ 2, L4 ⫽ 5, T11 ⫽ 10, and T6 ⫽ 15. The required sample size was calculated based on the mean and standard deviation (SD) of the maximal pinprick block level in a previous pilot study. We defined a 2-dermatomal difference in maximal pinprick block level between groups as a clinically significant effect of lumbar flexion. A sample size of 15 patients per group was required for the Mann-Whitney U test to detect a 2-dermatomal difference with an ␣ error of .05 and a  error of .2. Statistical analysis was performed using SPSS version 12 (SPSS Inc., Chicago, IL). The data regarding the patients’ characteristics were analyzed by an unpaired t test. The comparison of the hemodynamic variables at different times within the group was performed by 1-way repeated measures analysis of variance, and the Dunnett test was used as a post hoc analysis using the baseline value as a reference. To determine the difference in hemodynamic variables between the 2 groups, 2-way repeated measures analysis of variance was performed using the Scheffe method as a post hoc analysis. The sensory and motor blocks were analyzed using a Mann-Whitney U test. The values are expressed as mean ⫾ SD or median (interquartile range, range). P ⬍ .05 was considered significant.
Results One patient in Group N and 2 patients in Group F were excluded because additional anesthesia was administered due to pain before the end of surgery. Therefore, the final number of patients was 17 in Group N and 16 in Group F. There was no significant difference in age (22 ⫾ 3 vs. 22 ⫾ 2 y), height (174 ⫾ 4 vs. 173 ⫾ 6 cm), and weight (71 ⫾ 9 vs. 71 ⫾ 8 kg) between the 2 groups. The distribution of uppermost pinprick block levels is shown in Figure 1. The median dermatomal difference in the uppermost pinprick block level between groups was only 1.5, which did not satisfy our criteria for significance. The onset time to the uppermost pinprick block level was similar in the 2 groups. The lowermost pinprick block levels were similar between the groups at 60 minutes. A lower than S3 or S3 block was achieved in all patients except for 1 patient in each group (S1 in group N and L5 in group F). There was no significant difference in the degree of motor block on both sides (Table 1). There was no difference in the mean arterial blood pressure and heart rate between the 2 groups (Table 2).
Lumbar Flexion and Epidural Block
Fig 1. Distribution of the uppermost pinprick block levels. There is wide intersubject variability in the uppermost pinprick block level. The difference in the uppermost sensory block level between the 2 groups is less than 2 dermatomal levels. The open or the closed circle represents each case of which anesthetic level was that height.
Discussion To our knowledge, this is the first study evaluating the effect of lumbar flexion on the level of
•
Kim et al.
473
epidural anesthesia. We failed to find a clinically significant effect of lumbar flexion on the extent of blockade. Although we hypothesized that a 2-dermatomal difference would be clinically significant, we found only a 1.5 dermatomal difference in the uppermost pinprick block level. This difference disproves our hypothesis. In the cervical spinal level, the distance between the spinal cord and the posterior arch of the cervical canal was found to widen by up to 89% during flexion, and to narrow by up to 17% during extension.7 Cervical flexion increases the cranial spread of contrast medium compared with extension or the neutral position.6 Spinal flexion increases the size of the spinal canal and the intervertebral foraminal area.2-4 A widened spinal canal size can increase the volume of the epidural space, and an increased intervertebral foramen opening can result in leakage of the anesthetic solution. In addition, the lumbar epidural space pressure is increased when the lumbar spine is extended.5 A higher pressure gradient between the lumbar and lower thoracic or sacral epidural space can be generated in the neutral position more so than in the flexion position. Accordingly, we hypothesized that the anatomical and physiological changes in the lumbar epidural space associated with lumbar flexion could influence the level of epidural anesthesia. However, different from the cervical level, we could not demonstrate a clinically significant effect of lumbar flexion on the block level. The spread of contrast medium confirmed by xray may be different than that of local anesthetic. Contrary to spread of contrast medium, spread of block extent is affected by other factors such as patient’s sensitivity to local anesthetic, pH in the epidural space, and thickness of the nerve. The different anatomic structure between the cervical and lumbar spine may also be a reason for the different results. In addition to low median difference in the uppermost pinprick block level between groups, relatively small sample size and the wide variation of
Table 1. Characteristics of Epidural Block
Uppermost pinprick block level, D Time to the uppermost pinprick block level, D (min) Lowermost pinprick block level, ND Time to the lowermost pinprick block level, ND (min) Degree of motor block, D Degree of motor block, ND
Group N (n ⫽ 17)
Group F (n ⫽ 16)
T10 (T11-T6, T12-T3) 27.1 ⫾ 14.0 ⱕS3, (ⱕS3-ⱕS3,ⱕS3-S1) 17.6 ⫾ 8.3 2 (2-3, 0-3) 2 (1-3, 0-3)
T12-T11 (T12-T10, L1-T6) 20.0 ⫾ 15.1 ⱕS3, (ⱕS3-ⱕS3, ⱕS3-L5) 23.1 ⫾ 12.0 2 (2-3, 0-3) 2 (1-3, 0-3)
NOTE. Block levels and degree of motor block are expressed as median (interquartile range, range). Abbreviations: ⱕ, lower than; D, dependent side; Group F, lumbar spine flexed; Group N, lumbar spine in the neutral position; ND, nondependent side.
474
Regional Anesthesia and Pain Medicine Vol. 32 No. 6 November–December 2007 Table 2. Hemodynamic Data
Group N MAP HR Group F MAP HR
Baseline
10 min
20 min
30 min
40 min
50 min
60 min
97 ⫾ 13 78 ⫾ 12
97 ⫾ 15 84 ⫾ 13
100 ⫾ 12 81 ⫾ 15
99 ⫾ 14 79 ⫾ 14
98 ⫾ 12 78 ⫾ 14
99 ⫾ 12 72 ⫾ 14
99 ⫾ 11 72 ⫾ 12
95 ⫾ 9 81 ⫾ 14
101 ⫾ 9 88 ⫾ 10
100 ⫾ 9 82 ⫾ 11
102 ⫾ 10 79 ⫾ 11
99 ⫾ 11 76 ⫾ 11
99 ⫾ 11 77 ⫾ 14
97 ⫾ 8 77 ⫾ 13
NOTE. Values are expressed as mean ⫾ SD. Abbreviations: Group F, lumbar spine flexed; Group N, lumbar spine in the neutral position; HR, heart rate (beats per min); MAP, mean arterial blood pressure (mm Hg).
the measurement of block level also limit our results. In conclusion, we showed that lumbar flexion has no clinically relevant effect on the spread of local anesthetic blockade during lumbar epidural anesthesia.
References 1. Yokoyama M, Hanazaki M, Fujii H, Mizobuchi S, Nakatsuka H, Takahashi T, Matsumi M, Takeuchi M, Morita K. Correlation between the distribution of contrast medium and the extent of blockade during epidural anesthesia. Anesthesiolgy 2004;100:15041510. 2. Inufusa A, An HS, Lim TH, Hasegawa T, Haughton VM, Nowicki BH. Anatomic changes of the spinal canal and intervertebral foramen associated with flexion-extension movement. Spine 1996;21:2412-2420. 3. Fujiwara A, An HS, Lim TH, Haughton VM. Morphologic changes in the lumbar intervertebral foramen
4.
5.
6.
7.
due to flexion-extension, lateral bending, and axial rotation: an in vitro anatomic and biomechanical study. Spine 2001;26:876-882. Dai LY, Xu YK, Zhang WM, Zhou ZH. The effect of flexion-extension motion of the lumbar spine on the capacity of the spinal canal. An experimental study. Spine 1989;14:523-525. Takahashi K, Miyazaki T, Takino T, Matsui T, Tomita K. Epidural pressure measurements relationship between epidural pressure and posture in patients with lumbar spinal stenosis. Spine 1995;20:650-653. Lee CJ, Jeon Y, Lim YJ, Bahk JH, Kim YC, Lee SC, Kim CS. The influence of neck flexion and extension on the distribution of contrast medium in the high thoracic epidural space. Anesth Analg 2007;104: 1583-1586. Muhle C, Wiskirchen J, Weinert D, Falliner A, Wesner F, Brinkmann G, Heller M. Biomechanical aspects of the subarachnoid space and cervical cord in healthy individuals using kinematic magnetic resonance imaging. Spine 1998;23:556-567.
Anesthesia, Epidural, Lidocaine, Lumbar flexion.
T
he extent of epidural anesthesia is correlated with the spread of local anesthetic solution,1 which in turn may be affected by variations in the epidural space consequent to lumbar flexion. For example, lumbar flexion significantly increases the spinal canal area and the intervertebral foraminal size.2-4 Furthermore, compared with extension, the pressure in the lumbar epidural space is lower after flexing the lumbar spine.5 This suggests that flexion of the spine during epidural anesthesia may influ-
From the Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, Korea. Accepted for publication April 13, 2007. Presented in part at the annual meeting of the Korean Society of Anesthesiologists, Seoul, Korea, November 4, 2006. Reprint requests: Yunseok Jeon, M.D., Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul National University College of Medicine, #28 Yongon-Dong, Jongno-Gu, Seoul 110-744, Korea. E-mail: jeonyunseok@gmail. com © 2007 by the American Society of Regional Anesthesia and Pain Medicine. 1098-7339/07/3206-0001$32.00/0 doi:10.1016/j.rapm.2007.04.010
ence the distribution of local anesthetic and the extent of the blockade. For safe and effective epidural analgesia, it is important to control the level of anesthesia and to identify factors that influence its spread. We have observed that neck flexion and extension significantly affect the distribution of contrast medium in the epidural space at the high thoracic level.6 During epidural anesthesia, local anesthetic is injected into the epidural space with either the lumbar spine flexed or in the neutral position. However, the effect of lumbar flexion on the spread of lumbar epidural anesthesia is unknown. We hypothesized that flexion of the lumbar spine would influence the spread of local anesthetic in the epidural space. This study was performed to evaluate whether lumbar flexion influenced the spread of neuraxial blockade during epidural anesthesia.
Methods After obtaining approval of our Institutional Review Board and written informed consent from patients, 36 male patients with American Society of
Regional Anesthesia and Pain Medicine, Vol 32, No 6 (November–December), 2007: pp 471–474
471
472
Regional Anesthesia and Pain Medicine Vol. 32 No. 6 November–December 2007
Anesthesiologists physical status I were enrolled in this study. The patients were scheduled to undergo elective knee arthroscopy under epidural anesthesia without premedication. The patients were monitored with automated noninvasive blood pressure, electrocardiography, and pulse oximeter. The patients were positioned in the lateral decubitus position with the surgical side down and the hip flexed. The same anesthesiologist (J.-T.K.) performed all epidural catheterizations. After confirming the epidural space using the loss of resistance technique, an epidural catheter was inserted 3 cm through an 18-gauge Tuohy needle with the bevel facing cephalad at the L3-4 interspace. After a test dose (3 mL of 2% lidocaine and 15 g of epinephrine) was injected into the epidural space, the patients were randomly allocated to 1 of 2 groups of 18 patients each using a computer-generated randomization list: lumbar spine flexion group (Group F) and lumbar spine neutral group (Group N). In Group F, the patients maintained the lateral decubitus position with their spines and hips flexed. In Group N, the patients were requested to extend their spine and hips to achieve normal lumbar lordotic curvature. In both groups, a mixed solution of 2% lidocaine 16 mL and 8.4% sodium bicarbonate 2 mL was administered as a single bolus over approximately 60 seconds through an epidural catheter in their respective position. After injection of local anesthetic, all patients maintained their respective position for 5 minutes and then were turned to the supine position. The uppermost pinprick block levels were checked on the dependent midclavicular lines, and the lowermost pinprick block levels were checked only on the nondependent side to avoid the interruption of surgery every 10 minutes for 60 minutes after administering lidocaine. The degree of motor blockade was also assessed every 10 minutes using the modified Bromage scale (0, no block; 1, inability to raise the extended legs; 2, inability to flex the knee; 3, inability to flex the ankle, defined as complete motor block). The second anesthesiologist (Y.J.), who was blinded to the patient grouping, checked the epidural block dermatomal level. Mean arterial blood pressure and heart rate were monitored throughout the operation but only data up to 60 minutes were included in the data analysis. Atropine 0.5 mg was injected when heart rate fell to below 45 beats per minute and 10 mg of ephedrine was injected if the systolic blood pressure decreased to less than 90 mm Hg. The patient was excluded from the statistical analysis if general anesthesia or the additional administration of anesthetics were performed because of pain.
For the purpose of statistical analysis, each dermatomal level was assigned a segmental number such as “lower than S3,” and S3 ⫽ 1, S2⫽ 2, L4 ⫽ 5, T11 ⫽ 10, and T6 ⫽ 15. The required sample size was calculated based on the mean and standard deviation (SD) of the maximal pinprick block level in a previous pilot study. We defined a 2-dermatomal difference in maximal pinprick block level between groups as a clinically significant effect of lumbar flexion. A sample size of 15 patients per group was required for the Mann-Whitney U test to detect a 2-dermatomal difference with an ␣ error of .05 and a  error of .2. Statistical analysis was performed using SPSS version 12 (SPSS Inc., Chicago, IL). The data regarding the patients’ characteristics were analyzed by an unpaired t test. The comparison of the hemodynamic variables at different times within the group was performed by 1-way repeated measures analysis of variance, and the Dunnett test was used as a post hoc analysis using the baseline value as a reference. To determine the difference in hemodynamic variables between the 2 groups, 2-way repeated measures analysis of variance was performed using the Scheffe method as a post hoc analysis. The sensory and motor blocks were analyzed using a Mann-Whitney U test. The values are expressed as mean ⫾ SD or median (interquartile range, range). P ⬍ .05 was considered significant.
Results One patient in Group N and 2 patients in Group F were excluded because additional anesthesia was administered due to pain before the end of surgery. Therefore, the final number of patients was 17 in Group N and 16 in Group F. There was no significant difference in age (22 ⫾ 3 vs. 22 ⫾ 2 y), height (174 ⫾ 4 vs. 173 ⫾ 6 cm), and weight (71 ⫾ 9 vs. 71 ⫾ 8 kg) between the 2 groups. The distribution of uppermost pinprick block levels is shown in Figure 1. The median dermatomal difference in the uppermost pinprick block level between groups was only 1.5, which did not satisfy our criteria for significance. The onset time to the uppermost pinprick block level was similar in the 2 groups. The lowermost pinprick block levels were similar between the groups at 60 minutes. A lower than S3 or S3 block was achieved in all patients except for 1 patient in each group (S1 in group N and L5 in group F). There was no significant difference in the degree of motor block on both sides (Table 1). There was no difference in the mean arterial blood pressure and heart rate between the 2 groups (Table 2).
Lumbar Flexion and Epidural Block
Fig 1. Distribution of the uppermost pinprick block levels. There is wide intersubject variability in the uppermost pinprick block level. The difference in the uppermost sensory block level between the 2 groups is less than 2 dermatomal levels. The open or the closed circle represents each case of which anesthetic level was that height.
Discussion To our knowledge, this is the first study evaluating the effect of lumbar flexion on the level of
•
Kim et al.
473
epidural anesthesia. We failed to find a clinically significant effect of lumbar flexion on the extent of blockade. Although we hypothesized that a 2-dermatomal difference would be clinically significant, we found only a 1.5 dermatomal difference in the uppermost pinprick block level. This difference disproves our hypothesis. In the cervical spinal level, the distance between the spinal cord and the posterior arch of the cervical canal was found to widen by up to 89% during flexion, and to narrow by up to 17% during extension.7 Cervical flexion increases the cranial spread of contrast medium compared with extension or the neutral position.6 Spinal flexion increases the size of the spinal canal and the intervertebral foraminal area.2-4 A widened spinal canal size can increase the volume of the epidural space, and an increased intervertebral foramen opening can result in leakage of the anesthetic solution. In addition, the lumbar epidural space pressure is increased when the lumbar spine is extended.5 A higher pressure gradient between the lumbar and lower thoracic or sacral epidural space can be generated in the neutral position more so than in the flexion position. Accordingly, we hypothesized that the anatomical and physiological changes in the lumbar epidural space associated with lumbar flexion could influence the level of epidural anesthesia. However, different from the cervical level, we could not demonstrate a clinically significant effect of lumbar flexion on the block level. The spread of contrast medium confirmed by xray may be different than that of local anesthetic. Contrary to spread of contrast medium, spread of block extent is affected by other factors such as patient’s sensitivity to local anesthetic, pH in the epidural space, and thickness of the nerve. The different anatomic structure between the cervical and lumbar spine may also be a reason for the different results. In addition to low median difference in the uppermost pinprick block level between groups, relatively small sample size and the wide variation of
Table 1. Characteristics of Epidural Block
Uppermost pinprick block level, D Time to the uppermost pinprick block level, D (min) Lowermost pinprick block level, ND Time to the lowermost pinprick block level, ND (min) Degree of motor block, D Degree of motor block, ND
Group N (n ⫽ 17)
Group F (n ⫽ 16)
T10 (T11-T6, T12-T3) 27.1 ⫾ 14.0 ⱕS3, (ⱕS3-ⱕS3,ⱕS3-S1) 17.6 ⫾ 8.3 2 (2-3, 0-3) 2 (1-3, 0-3)
T12-T11 (T12-T10, L1-T6) 20.0 ⫾ 15.1 ⱕS3, (ⱕS3-ⱕS3, ⱕS3-L5) 23.1 ⫾ 12.0 2 (2-3, 0-3) 2 (1-3, 0-3)
NOTE. Block levels and degree of motor block are expressed as median (interquartile range, range). Abbreviations: ⱕ, lower than; D, dependent side; Group F, lumbar spine flexed; Group N, lumbar spine in the neutral position; ND, nondependent side.
474
Regional Anesthesia and Pain Medicine Vol. 32 No. 6 November–December 2007 Table 2. Hemodynamic Data
Group N MAP HR Group F MAP HR
Baseline
10 min
20 min
30 min
40 min
50 min
60 min
97 ⫾ 13 78 ⫾ 12
97 ⫾ 15 84 ⫾ 13
100 ⫾ 12 81 ⫾ 15
99 ⫾ 14 79 ⫾ 14
98 ⫾ 12 78 ⫾ 14
99 ⫾ 12 72 ⫾ 14
99 ⫾ 11 72 ⫾ 12
95 ⫾ 9 81 ⫾ 14
101 ⫾ 9 88 ⫾ 10
100 ⫾ 9 82 ⫾ 11
102 ⫾ 10 79 ⫾ 11
99 ⫾ 11 76 ⫾ 11
99 ⫾ 11 77 ⫾ 14
97 ⫾ 8 77 ⫾ 13
NOTE. Values are expressed as mean ⫾ SD. Abbreviations: Group F, lumbar spine flexed; Group N, lumbar spine in the neutral position; HR, heart rate (beats per min); MAP, mean arterial blood pressure (mm Hg).
the measurement of block level also limit our results. In conclusion, we showed that lumbar flexion has no clinically relevant effect on the spread of local anesthetic blockade during lumbar epidural anesthesia.
References 1. Yokoyama M, Hanazaki M, Fujii H, Mizobuchi S, Nakatsuka H, Takahashi T, Matsumi M, Takeuchi M, Morita K. Correlation between the distribution of contrast medium and the extent of blockade during epidural anesthesia. Anesthesiolgy 2004;100:15041510. 2. Inufusa A, An HS, Lim TH, Hasegawa T, Haughton VM, Nowicki BH. Anatomic changes of the spinal canal and intervertebral foramen associated with flexion-extension movement. Spine 1996;21:2412-2420. 3. Fujiwara A, An HS, Lim TH, Haughton VM. Morphologic changes in the lumbar intervertebral foramen
4.
5.
6.
7.
due to flexion-extension, lateral bending, and axial rotation: an in vitro anatomic and biomechanical study. Spine 2001;26:876-882. Dai LY, Xu YK, Zhang WM, Zhou ZH. The effect of flexion-extension motion of the lumbar spine on the capacity of the spinal canal. An experimental study. Spine 1989;14:523-525. Takahashi K, Miyazaki T, Takino T, Matsui T, Tomita K. Epidural pressure measurements relationship between epidural pressure and posture in patients with lumbar spinal stenosis. Spine 1995;20:650-653. Lee CJ, Jeon Y, Lim YJ, Bahk JH, Kim YC, Lee SC, Kim CS. The influence of neck flexion and extension on the distribution of contrast medium in the high thoracic epidural space. Anesth Analg 2007;104: 1583-1586. Muhle C, Wiskirchen J, Weinert D, Falliner A, Wesner F, Brinkmann G, Heller M. Biomechanical aspects of the subarachnoid space and cervical cord in healthy individuals using kinematic magnetic resonance imaging. Spine 1998;23:556-567.