Cell Biochem Biophys (2015) 71:875–880 DOI 10.1007/s12013-014-0277-x
ORIGINAL PAPER
Suitable Depth of Epidural Puncture in Nulliparous Pregnant Woman Yi Luo • Dandan Zhang • Jing Zheng Qiling Yang • Xiaohu An • Yi Chen • Dasong Yu • Zeyong Yang
•
Published online: 10 October 2014 Ó Springer Science+Business Media New York 2014
Abstract We study the suitable depth for epidural puncture in primiparas so as to decrease epidural complications and provide anesthesiologists with an appropriate insertion guide. A prospective study of 87 primipara patients receiving labor analgesia who had epidural punctures in the course of vaginal delivery were randomly divided into 3 groups: the L3,4 group (N = 27), the L2,3 group (N = 29), and the L1,2 group (N = 26). Predictive statistical models were used for the formulation of the ideal epidural puncture needle depth. Eighty two patients who had non-traumatic epidural punctures were studied. There were no significant changes in age, weight, height, weight/ height ratio, gestational weeks, fetus weight, pregnancy weight, weight difference, and fetus weight (P [ 0.05). Compared with L3,4 intervertebral space, the puncture depth in L1,2 and L2,3 was significantly shorter (P \ 0.05) and (P \ 0.001), respectively; Regression equation: PD (cm) = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017. The correlation coefficient for LHZ was 0.351 (95 % CI
Y. Luo Department of Gynaecology and Obstetrics, Qingpu Hospital, Fudan University School of Medicine, Shanghai 201700, China D. Zhang Y. Chen Department of Gynaecology and Obstetrics, International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China J. Zheng Q. Yang X. An D. Yu Z. Yang (&) Department of Anesthesiology, International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China e-mail: [email protected]
0.278–0.424; P \ 0.001), the correlation coefficient for BMI was 0.147 (95 % CI 0.123–0.171; P \ 0.001). This formula is accurate and practical with less complex calculations. However, further validation through a prospective study will be required. It is an accurate way to localize the puncture site in parturients and improve the efficiency of puncture in parturients for analgesia labor.Epidural puncture depth prediction in L1,2, L2,3, and L3,4 can supply with a related reference. Keywords labor
Epidural Logistics regression Analgesia
Introduction The great improvements made over the years for epidural analgesia [1] have not been matched by a corresponding advancement in the identification of the epidural space. Although epidurography [2] and nerve stimulation [3] have been used to evaluate the epidural space position, anatomical landmarks and the loss-of-resistance technique remain the standard techniques to locate the epidural space. The experience of determining the puncture depth from the skin to the epidural space for initiation of an epidural analgesia in different intervertebral spaces has not been described in the literature. Junior doctors sometimes encounter complications of epidural anesthesia such as vascular puncture, dural puncture, and nerve damage. We study the suitable depth for epidural puncture in primipara for analgesia during labor so that this knowledge can help to decrease complications associated with epidural complications. We also aim to provide anesthesia interns and resident physicians with epidural puncture guide.
123
876
Methods After approval of the Research Ethics Board of International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University, School of Medicine was obtained, this prospective cohort study was conducted from March 2014 to July 2014. Women in labor requesting epidural analgesia were recruited after written informed consent was obtained. The inclusion criteria were primiparas with ASA Physical Status grade I–II, and full-term singleton pregnancies. Patient recruitment occurred only when the investigators were available. The inclusion criteria for this study were as follows: (1) Patients had regular prenatal examinations at the outpatient clinic; (2) They were between 22 and 41 years of age; (3) They had a gestational age C37 and \42 weeks; (4) They had an estimated fetal weight C2,500 and \4,200 g. The exclusion criteria were a history of spinal surgery or platelet count \100 9 109/L or the number of attempts at reinsertion of the needle C4. Meanwhile those with previous spinal surgery, marked spinal bony deformity (e.g., scoliosis, as confirmed clinically by two anesthesiologists) and analgesia failure [VAS (visual analog pain score) [4, absence of unilateral or failed block] at 20 min after injection of the loading dose were excluded. Patient recruitment was prospective, and sampling occurred only during times when the investigators were available. Data collection was planned as a cohort study.
Epidural Procedure The epidural needle was inserted to epidural space by either a senior attending physician who was blinded to the experiment. The L3,4, L2,3, L1,2 intervertebral spaces were identified by counting the laminae and the interspaces. Information on the insertion point was provided by the investigator noting the visible skin markings, epidural puncture was done at 0.5 cm lateral to the midline, between superior and inferior spinous processes of L1,2, L2,3, or L3,4. After infiltration of the skin with 2 % lidocaine, after insertion, the needle was not removed, the patient’s back was palpated by both the investigator and senior attending physician, and the findings during the course of the puncture were documented. After the epidural needle insertion was performed using a 17 gauge (8.0 cm) standard epidural needle (E/SII Single-use Puncture set for Local Anesthesia, Shanghai Shangyi Kangge Medical Instrument Co. Ltd, Shanghai, People’s Republic of China) with markings at 1 cm intervals. The needle was introduced through the predetermined insertion point at a vertical angle with the plane of the lower back as instructed by the investigator. We
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measured the distance from the skin to the ligamentum flavum in the paramedian point of puncture. We administrated epidural puncture, which was done according to the following conditions: (1) sudden decrease in the pressure when inserting the needle (2) vertical depth:epidural needle kept vertical to the patient’s lumbar and back during analgesia labor; the catheter can be inserted with ease and without any resistance (3) sufficient and definite epidural analgesia without subdural block and subarachnoid block. Once the epidural space was located using the 2 mL saline method, a sterile marker was placed on the needle, as close to the skin surface as possible, to determine the actual distance from the skin to the epidural space. An epidural catheter U1.0 (E/SII Single-use Puncture set for Local Anesthesia, Shanghai Shangyi Kangge Medical Instrument Co. Ltd, Shanghai, People’s Republic of China) was inserted approximately 4 cm into the epidural space. After the removal of the epidural needle, the distance from the tip of the needle to the marker was measured by the senior attending physician, using a ruler with millimeter markings, and recorded as epidural puncture depth. A test dose with 4 mL 2 % lidocaine, which was administered through the epidural catheter, followed 5 min later by an initial loading dose of 10 mL 0.1 % ropivacaine with sufentanyl 4 lg. HR, ECG, BP, PaO2 were continuously monitored during labor process. The primary outcome was the accuracy and precision of the depth to the epidural space, as measured by the correlation between the epidural puncture depth and intervertebral space (LHZ, L1,2 = 1, L2,3 = 2, L3,4 = 3) or body mass index (BMI). The secondary outcomes were: (a) pre-pregnancy weight, weight at admission, height, weight/height ratio, BMI, intervertebral space used (L1,2, L2,3, and L3,4), gestational weeks, fetus weight at delivery, and anesthesia and obstetrical complications during pregnancy were recorded; (b) the pain experienced during the epidural needle placement was assessed after the completion of the catheter insertion (verbal rating scale [VRS], 0–10, 0 = no pain, 10 = maximum pain); (c) the presence of effective analgesia (VRS = 1, absence of unilateral or failed block) at 20 min after injection of the loading dose; (d) the time to comfort the patient after the administration of the loading dose; (e) the procedure complications (bleeding, dural puncture, paresthesia), (f) the number of attempts at reinsertion of the epidural needle.
Statistical Analysis Descriptive statistics, including the mean and standard deviation (sd), were calculated for the continuous data,
Cell Biochem Biophys (2015) 71:875–880
877
Table 1 Flow diagram for suitable depth of epidural puncture depth in nulliparous women, 87 patients were recruited, 82 of whom were considered for the analysis
Five patients were excluded for reasons such as the number of attempts at reinsertion of the needle C4 (n = 2), platelet count \100 9 109/L (n = 2), or previous spinal operation (n = 1)
continuous variable was expressed as mean ± standard error, and analysis of variance for age, weight, height, weight/height Ratio and depth of epidural puncture was calculated using SPSS17.0. Multivariant gradual regressive analysis regression model with stepwise approach showed a relationship between the effective epidural puncture needle depth (PD) and intervertebral space (LHZ) or BMI, analysis of variance was judged to be a fitting model. Curve estimation: LHZ or BMI was used as independent variable, puncture depth (PD) as dependent variable, *P \ 0.05, ***P \ 0.001 was considered statistically significant.
Results Eighty-two patients who had non-traumatic epidural punctures were studied. Five patients were excluded for reasons such as the number of attempts at reinsertion of the needle C4 (n = 2), platelets count\100 9 109 (n = 2), or previous spinal surgery (n = 1) (Table 1). The patient characteristics were as follows: age: 23–41 year-old; weight: 57–83 kg; height: 152–173 cm. Prepregnancy weight: 40–68 kg; gestational weeks: 35.7–41.6 weeks; fetus weight: 2,800–4,200 g; puncture
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Cell Biochem Biophys (2015) 71:875–880
Table 2 Baseline of patients for labor analgesia in L1,3, L2,3, and L3,4 groups Monitored Variables
L1,2
L2,3
L3,4
Age (year. mean ± SD)
29.04 ± 2.91
30.14 ± 3.92
29.44 ± 2.44
Height (cm, mean ± SD)
162.00 ± 5.29
162.20 ± 5.30
159.90 ± 4.72
Weight (kg, mean ± SD)
69.30 ± 6.62
70.05 ± 6.57
69.30 ± 6.30
BMI (kg.m-2, mean ± SD)
26.43 ± 2.65
26.64 ± 2.14
27.14 ± 2.50
Weight/height ratio (kg/m, mean ± SD)
42.78 ± 0.77
43.17 ± 0.65
43.35 ± 0.73
Gestational weeks (week, mean ± SD)
39.84 ± 2.13
39.52 ± 1.27
39.59 ± 1.24
Fetus Weight (g, mean ± SD)
3391 ± 299
3479 ± 404
3460 ± 721
Pre-pregnancy weight (kg, mean ± SD)
53.40 ± 5.86
56.24 ± 6.37
54.37 ± 7.09
Weight difference (kg, mean ± SD)
15.90 ± 5.20
13.81 ± 5.34
14.93 ± 5.59
Depth of Puncture(cm)
878 8
1(LHZ:L1,2) 2(LHZ:L2,3)
6
3(LHZ:L3,4)
4
2
0 10
20
30
All patients number in 3 groups
There were no statistically significant differences for all the variables between the three groups (P [ 0.05) BMI body mass index Table 3 Epidural puncture depth for labor analgesia in L1,2, L2,3, and L3,4 groups Monitored variables
L1,2
L2,3
L3,4
Puncture depth (cm)
4.25 ± 0.60
4.68 ± 0.74*
5.05 ± 0.53***
Fig. 1 The correlation between the epidural PD and intervertebralspace (LHZ, L1,2 = 1, L2,3 = 2, L3,4 = 3)
Curve estimation: LHZ as independent variable and PD as dependent variable; regression equation: PD (cm) = 0.403 LHZ ? 3.856 (95 % CI 0.316–0.490; P \ 0.0001), analysis of variance (ANOVA) F = 21.478 (Fig. 1). BMI as independent variable and puncture depth as dependent variable, regression equation: PD (cm) = 0.161 LHZ ? 0.351 (95 % CI 0.134–0.188; P \ 0.0001), (ANOVA) F = 34.881 (Fig. 2). Curve estimation: (1) intervertebral space used (LHZ) as independent variable and puncture depth (PD) as dependent variable, regression equation: PD (cm) = 0.403 LHZ ? 3.856 (95 % CI 0.316–0.490; P \ 0.0001), analysis of variance (ANOVA) F = 21.478. Curve estimation: (2) body mass index (BMI) as independent variable and puncture depth as dependent variable, regression equation: PD (cm) = 0.161 LHZ ? 0.351 (95 % CI 0.134–0.188; P \ 0.0001), analysis of variance (ANOVA) F = 34.881.
There were statistically significant differences for L1,2, L2,3, and L3,4 among the three groups (*\0.05, ***\0.001)
Discussion depth: 3.40–7.50 cm. None of the patients had an accidental dural puncture or paresthesia. There were no significant differences in age, weight, height, weight/height ratio, gestational weeks, fetus weight, pregnancy weight, weight difference, and fetus weight (P [ 0.05) (Table 2). Compared to the L3–4 intervertebral space, the puncture depth in L1–2 and L2–3 was significantly shorter, with P \ 0.05 and P \ 0.001 respectively (Table 3). Statistical analysis using predictive regression model with stepwise approach showed a relationship between PD and BMI or LHZ. The correlation coefficient (r) of the LHZ and the PD was 0.147 (95 % CI 0.123–0.171; P \ 0.001). The correlation coefficient (r) of the BMI and the PD was 0.351 (95 % CI 0.278–0.424; P \ 0.001). Regression equation: PD = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017.
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With the two-child policy change in China in recent years, more and more pregnant women are managed in the delivery room, anesthesiologists often need to perform an epidural puncture as soon as possible for acute pain in parturients with cervical dilation [ or = 3 cm who request an epidural analgesia. It is, sometimes, not feasible for an anesthesiologist to assist in the procedure through the use of ultrasound imaging to locate the epidural space because of the number of patients that have to be treated simultaneously, especially in busy hospitals. The presence of adipose tissue and pregnancy-induced softening of the soft tissues and ligaments can increase the false-positive rate when identifying the epidural space for labor analgesia, the combination of which accounts for a higher incidence of technical difficulty [4].
Depth of Puncture(DP)(cm)
Cell Biochem Biophys (2015) 71:875–880
879
8
6
4
2
0 20
25
30
35 -2
Body Mass Index (BMI)(kg.m ) Fig. 2 The correlation between the epidural puncture depth and body mass index (BMI)
Epidural puncture is the golden standard for analgesia during labor in our center for more than fifteen years. Anesthesiologists often need to successfully do an epidural analgesia in the shortest delay possible, such that pain relief for nulliparous woman can be achieved within 10 min. We, therefore, need to administrate epidural puncture in advance in the delivery room. However, resident doctors sometimes encounter epidural complications such as perforation of dura mater, nerve damage, and nonnerve damage. We studied suitable depth parameter of epidural puncture in primipara so that this research work can help to decrease epidural complications such as perforation of dura mater or nerve damage. We also aim to provide anesthesia interns and resident physicians with an epidural puncture guide. Our study used multivariant gradual regressive analysis of effective puncture depth as dependent variable, to establish a regression equation. Regression equation was found to be PD = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017. Our results, involving only nulliparous women for analgesia during labor, the distance for puncture points of L3,4 and of L2,3 was 5.05 ± 0.53 cm and 4.68 ± 0.74 cm, respectively. Previous studies have demonstrated a correlation between the distance from the skin to the lumbar epidural space with the BMI in a mixed population, consisting of obese and non-obese parturients [5–9]. The mean depth to the epidural space from the skin has been described as being in the range of 4.6–5.3 cm [5, 7], which is inconsistent with our result due to the difference in race. It is possible that the distance for obese pregnant women is more than 5.05 ± 0.53 cm, Balki [10] reported that the depth to the epidural space was more than 8 cm in only 17 % of the patients with a mean of 6.6 cm (range 4.5–8.5 cm). It is better to use a standard needle to identify the epidural space in the majority of obese women. BMI is a main marker for fat deposit, it reflects subcutaneous fat thickness as an independent variable and
predicts the lumbar epidural puncture depth. The epidural depth is discordant due to the spinal physiological curve, processus spinosus length in different vertebral body, and spinous process angulated to basivertebral cross section. Anatomical epidural depth is different at the three intervertebral levels, compared to L3–4 intervertebral space, the puncture depth for L1–2 and L2–3 was significantly shorter (P \ 0.05) and(P \ 0.001), respectively. In conclusion, prediction of regression equation is relatively simple, and data about body weight, height, and intervertebral space can be collected with facility. The doctor performing the procedure should consider the puncture depth scope according to the prediction value which equals to vertical puncture depth : the distance from skin to epidural space, the distance from ligamentum flavum to dura mater of spinal cord in median line of back (epidural interspace L3,4 the broadest 0.6 cm for the adult). If the depth from skin to epidural space reached or exceeded the predicted value in primiparas, the clinician should be wary of perforation of the dura mater. Our study suggests that L3,4 and L2,3 in the lumbar vertebra may optimize epidural catheter placement in parturients by providing a reasonable estimation of the depth to the epidural space and the skin puncture site. Acknowledgments The authors would like to acknowledge the nurses and midwives of the delivery room of our hospital for assisting in recruit nulliparous patients for this study. Conflict of interest The authors declared that they have no conflicts of interest to this work. Funding Perinatal Potential Subject (To International Peace Maternity and Child Health Hospital, Shanghai Jiaotong University School of Medicine in May, 2014).
References 1. Frolich, M. A., & Caton, D. (2001). Pioneers in epidural needle design. Anesthesia and Analgesia, 93, 215–220. 2. Collier, C. B. (1996). Why obstetric epidural fail: a study of epidurograms. International journal of obstetric anesthesia., 5, 19–31. 3. Tsui, B. C., Gupta, S., & Finucane, B. (1999). Determination of epidural catheter placement using nerve stimulation in obstetric patients. Regional Anesthesia and Pain Medicine, 24, 17–23. 4. Saravanakumar, K., Rao, S. G., & Cooper, G. M. (2006). Obesity and obstetric anaesthesia. Anaesthesia, 61, 36–48. 5. Clinkscales, C. P., Greenfield, M. L. V. H., Vanarase, M., et al. (2007). An observational study of the relationship between lumbar epidural space depth and body mass index in Michigan parturients. International Journal of Obstetric Anesthesia, 16, 323–327. 6. Palmer, S. K., Abram, S. E., Maitra, A. M., et al. (1983). Distance from the skin to the lumbar epidural space in an obstetric population. Anesthesia and Analgesia, 62, 944–946. 7. Watts, R. W. (1993). The influence of obesity on the relationship between body mass index and the distance to the epidural space from the skin. Anaesthesia and Intensive Care, 21, 309–310.
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880 8. Hamza, J., Smida, M., Benhamou, D., et al. (1995). Parturient’s posture during epidural puncture affects the distance from skin to epidural space. Journal of Clinical Anesthesia, 7, 1–4. 9. Segal, S., Beach, M., & Eappen, S. (1996). A multivariate model to predict the distance from the skin to the epidural space in an obstetric population. Regional Anesthesia, 21, 451–455.
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Cell Biochem Biophys (2015) 71:875–880 10. Balki, M., Lee, Y., Halpern, S., et al. (2009). Ultrasound imaging of the lumbar spine in the transverse plane: The correlation between estimated and actual depth to the epidural space in obese parturients. Anesthesia and Analgesia, 108(6), 1876–1881.
ORIGINAL PAPER
Suitable Depth of Epidural Puncture in Nulliparous Pregnant Woman Yi Luo • Dandan Zhang • Jing Zheng Qiling Yang • Xiaohu An • Yi Chen • Dasong Yu • Zeyong Yang
•
Published online: 10 October 2014 Ó Springer Science+Business Media New York 2014
Abstract We study the suitable depth for epidural puncture in primiparas so as to decrease epidural complications and provide anesthesiologists with an appropriate insertion guide. A prospective study of 87 primipara patients receiving labor analgesia who had epidural punctures in the course of vaginal delivery were randomly divided into 3 groups: the L3,4 group (N = 27), the L2,3 group (N = 29), and the L1,2 group (N = 26). Predictive statistical models were used for the formulation of the ideal epidural puncture needle depth. Eighty two patients who had non-traumatic epidural punctures were studied. There were no significant changes in age, weight, height, weight/ height ratio, gestational weeks, fetus weight, pregnancy weight, weight difference, and fetus weight (P [ 0.05). Compared with L3,4 intervertebral space, the puncture depth in L1,2 and L2,3 was significantly shorter (P \ 0.05) and (P \ 0.001), respectively; Regression equation: PD (cm) = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017. The correlation coefficient for LHZ was 0.351 (95 % CI
Y. Luo Department of Gynaecology and Obstetrics, Qingpu Hospital, Fudan University School of Medicine, Shanghai 201700, China D. Zhang Y. Chen Department of Gynaecology and Obstetrics, International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China J. Zheng Q. Yang X. An D. Yu Z. Yang (&) Department of Anesthesiology, International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China e-mail: [email protected]
0.278–0.424; P \ 0.001), the correlation coefficient for BMI was 0.147 (95 % CI 0.123–0.171; P \ 0.001). This formula is accurate and practical with less complex calculations. However, further validation through a prospective study will be required. It is an accurate way to localize the puncture site in parturients and improve the efficiency of puncture in parturients for analgesia labor.Epidural puncture depth prediction in L1,2, L2,3, and L3,4 can supply with a related reference. Keywords labor
Epidural Logistics regression Analgesia
Introduction The great improvements made over the years for epidural analgesia [1] have not been matched by a corresponding advancement in the identification of the epidural space. Although epidurography [2] and nerve stimulation [3] have been used to evaluate the epidural space position, anatomical landmarks and the loss-of-resistance technique remain the standard techniques to locate the epidural space. The experience of determining the puncture depth from the skin to the epidural space for initiation of an epidural analgesia in different intervertebral spaces has not been described in the literature. Junior doctors sometimes encounter complications of epidural anesthesia such as vascular puncture, dural puncture, and nerve damage. We study the suitable depth for epidural puncture in primipara for analgesia during labor so that this knowledge can help to decrease complications associated with epidural complications. We also aim to provide anesthesia interns and resident physicians with epidural puncture guide.
123
876
Methods After approval of the Research Ethics Board of International Peace Maternity and Child Health Hospital, Shanghai Jiao Tong University, School of Medicine was obtained, this prospective cohort study was conducted from March 2014 to July 2014. Women in labor requesting epidural analgesia were recruited after written informed consent was obtained. The inclusion criteria were primiparas with ASA Physical Status grade I–II, and full-term singleton pregnancies. Patient recruitment occurred only when the investigators were available. The inclusion criteria for this study were as follows: (1) Patients had regular prenatal examinations at the outpatient clinic; (2) They were between 22 and 41 years of age; (3) They had a gestational age C37 and \42 weeks; (4) They had an estimated fetal weight C2,500 and \4,200 g. The exclusion criteria were a history of spinal surgery or platelet count \100 9 109/L or the number of attempts at reinsertion of the needle C4. Meanwhile those with previous spinal surgery, marked spinal bony deformity (e.g., scoliosis, as confirmed clinically by two anesthesiologists) and analgesia failure [VAS (visual analog pain score) [4, absence of unilateral or failed block] at 20 min after injection of the loading dose were excluded. Patient recruitment was prospective, and sampling occurred only during times when the investigators were available. Data collection was planned as a cohort study.
Epidural Procedure The epidural needle was inserted to epidural space by either a senior attending physician who was blinded to the experiment. The L3,4, L2,3, L1,2 intervertebral spaces were identified by counting the laminae and the interspaces. Information on the insertion point was provided by the investigator noting the visible skin markings, epidural puncture was done at 0.5 cm lateral to the midline, between superior and inferior spinous processes of L1,2, L2,3, or L3,4. After infiltration of the skin with 2 % lidocaine, after insertion, the needle was not removed, the patient’s back was palpated by both the investigator and senior attending physician, and the findings during the course of the puncture were documented. After the epidural needle insertion was performed using a 17 gauge (8.0 cm) standard epidural needle (E/SII Single-use Puncture set for Local Anesthesia, Shanghai Shangyi Kangge Medical Instrument Co. Ltd, Shanghai, People’s Republic of China) with markings at 1 cm intervals. The needle was introduced through the predetermined insertion point at a vertical angle with the plane of the lower back as instructed by the investigator. We
123
Cell Biochem Biophys (2015) 71:875–880
measured the distance from the skin to the ligamentum flavum in the paramedian point of puncture. We administrated epidural puncture, which was done according to the following conditions: (1) sudden decrease in the pressure when inserting the needle (2) vertical depth:epidural needle kept vertical to the patient’s lumbar and back during analgesia labor; the catheter can be inserted with ease and without any resistance (3) sufficient and definite epidural analgesia without subdural block and subarachnoid block. Once the epidural space was located using the 2 mL saline method, a sterile marker was placed on the needle, as close to the skin surface as possible, to determine the actual distance from the skin to the epidural space. An epidural catheter U1.0 (E/SII Single-use Puncture set for Local Anesthesia, Shanghai Shangyi Kangge Medical Instrument Co. Ltd, Shanghai, People’s Republic of China) was inserted approximately 4 cm into the epidural space. After the removal of the epidural needle, the distance from the tip of the needle to the marker was measured by the senior attending physician, using a ruler with millimeter markings, and recorded as epidural puncture depth. A test dose with 4 mL 2 % lidocaine, which was administered through the epidural catheter, followed 5 min later by an initial loading dose of 10 mL 0.1 % ropivacaine with sufentanyl 4 lg. HR, ECG, BP, PaO2 were continuously monitored during labor process. The primary outcome was the accuracy and precision of the depth to the epidural space, as measured by the correlation between the epidural puncture depth and intervertebral space (LHZ, L1,2 = 1, L2,3 = 2, L3,4 = 3) or body mass index (BMI). The secondary outcomes were: (a) pre-pregnancy weight, weight at admission, height, weight/height ratio, BMI, intervertebral space used (L1,2, L2,3, and L3,4), gestational weeks, fetus weight at delivery, and anesthesia and obstetrical complications during pregnancy were recorded; (b) the pain experienced during the epidural needle placement was assessed after the completion of the catheter insertion (verbal rating scale [VRS], 0–10, 0 = no pain, 10 = maximum pain); (c) the presence of effective analgesia (VRS = 1, absence of unilateral or failed block) at 20 min after injection of the loading dose; (d) the time to comfort the patient after the administration of the loading dose; (e) the procedure complications (bleeding, dural puncture, paresthesia), (f) the number of attempts at reinsertion of the epidural needle.
Statistical Analysis Descriptive statistics, including the mean and standard deviation (sd), were calculated for the continuous data,
Cell Biochem Biophys (2015) 71:875–880
877
Table 1 Flow diagram for suitable depth of epidural puncture depth in nulliparous women, 87 patients were recruited, 82 of whom were considered for the analysis
Five patients were excluded for reasons such as the number of attempts at reinsertion of the needle C4 (n = 2), platelet count \100 9 109/L (n = 2), or previous spinal operation (n = 1)
continuous variable was expressed as mean ± standard error, and analysis of variance for age, weight, height, weight/height Ratio and depth of epidural puncture was calculated using SPSS17.0. Multivariant gradual regressive analysis regression model with stepwise approach showed a relationship between the effective epidural puncture needle depth (PD) and intervertebral space (LHZ) or BMI, analysis of variance was judged to be a fitting model. Curve estimation: LHZ or BMI was used as independent variable, puncture depth (PD) as dependent variable, *P \ 0.05, ***P \ 0.001 was considered statistically significant.
Results Eighty-two patients who had non-traumatic epidural punctures were studied. Five patients were excluded for reasons such as the number of attempts at reinsertion of the needle C4 (n = 2), platelets count\100 9 109 (n = 2), or previous spinal surgery (n = 1) (Table 1). The patient characteristics were as follows: age: 23–41 year-old; weight: 57–83 kg; height: 152–173 cm. Prepregnancy weight: 40–68 kg; gestational weeks: 35.7–41.6 weeks; fetus weight: 2,800–4,200 g; puncture
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Cell Biochem Biophys (2015) 71:875–880
Table 2 Baseline of patients for labor analgesia in L1,3, L2,3, and L3,4 groups Monitored Variables
L1,2
L2,3
L3,4
Age (year. mean ± SD)
29.04 ± 2.91
30.14 ± 3.92
29.44 ± 2.44
Height (cm, mean ± SD)
162.00 ± 5.29
162.20 ± 5.30
159.90 ± 4.72
Weight (kg, mean ± SD)
69.30 ± 6.62
70.05 ± 6.57
69.30 ± 6.30
BMI (kg.m-2, mean ± SD)
26.43 ± 2.65
26.64 ± 2.14
27.14 ± 2.50
Weight/height ratio (kg/m, mean ± SD)
42.78 ± 0.77
43.17 ± 0.65
43.35 ± 0.73
Gestational weeks (week, mean ± SD)
39.84 ± 2.13
39.52 ± 1.27
39.59 ± 1.24
Fetus Weight (g, mean ± SD)
3391 ± 299
3479 ± 404
3460 ± 721
Pre-pregnancy weight (kg, mean ± SD)
53.40 ± 5.86
56.24 ± 6.37
54.37 ± 7.09
Weight difference (kg, mean ± SD)
15.90 ± 5.20
13.81 ± 5.34
14.93 ± 5.59
Depth of Puncture(cm)
878 8
1(LHZ:L1,2) 2(LHZ:L2,3)
6
3(LHZ:L3,4)
4
2
0 10
20
30
All patients number in 3 groups
There were no statistically significant differences for all the variables between the three groups (P [ 0.05) BMI body mass index Table 3 Epidural puncture depth for labor analgesia in L1,2, L2,3, and L3,4 groups Monitored variables
L1,2
L2,3
L3,4
Puncture depth (cm)
4.25 ± 0.60
4.68 ± 0.74*
5.05 ± 0.53***
Fig. 1 The correlation between the epidural PD and intervertebralspace (LHZ, L1,2 = 1, L2,3 = 2, L3,4 = 3)
Curve estimation: LHZ as independent variable and PD as dependent variable; regression equation: PD (cm) = 0.403 LHZ ? 3.856 (95 % CI 0.316–0.490; P \ 0.0001), analysis of variance (ANOVA) F = 21.478 (Fig. 1). BMI as independent variable and puncture depth as dependent variable, regression equation: PD (cm) = 0.161 LHZ ? 0.351 (95 % CI 0.134–0.188; P \ 0.0001), (ANOVA) F = 34.881 (Fig. 2). Curve estimation: (1) intervertebral space used (LHZ) as independent variable and puncture depth (PD) as dependent variable, regression equation: PD (cm) = 0.403 LHZ ? 3.856 (95 % CI 0.316–0.490; P \ 0.0001), analysis of variance (ANOVA) F = 21.478. Curve estimation: (2) body mass index (BMI) as independent variable and puncture depth as dependent variable, regression equation: PD (cm) = 0.161 LHZ ? 0.351 (95 % CI 0.134–0.188; P \ 0.0001), analysis of variance (ANOVA) F = 34.881.
There were statistically significant differences for L1,2, L2,3, and L3,4 among the three groups (*\0.05, ***\0.001)
Discussion depth: 3.40–7.50 cm. None of the patients had an accidental dural puncture or paresthesia. There were no significant differences in age, weight, height, weight/height ratio, gestational weeks, fetus weight, pregnancy weight, weight difference, and fetus weight (P [ 0.05) (Table 2). Compared to the L3–4 intervertebral space, the puncture depth in L1–2 and L2–3 was significantly shorter, with P \ 0.05 and P \ 0.001 respectively (Table 3). Statistical analysis using predictive regression model with stepwise approach showed a relationship between PD and BMI or LHZ. The correlation coefficient (r) of the LHZ and the PD was 0.147 (95 % CI 0.123–0.171; P \ 0.001). The correlation coefficient (r) of the BMI and the PD was 0.351 (95 % CI 0.278–0.424; P \ 0.001). Regression equation: PD = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017.
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With the two-child policy change in China in recent years, more and more pregnant women are managed in the delivery room, anesthesiologists often need to perform an epidural puncture as soon as possible for acute pain in parturients with cervical dilation [ or = 3 cm who request an epidural analgesia. It is, sometimes, not feasible for an anesthesiologist to assist in the procedure through the use of ultrasound imaging to locate the epidural space because of the number of patients that have to be treated simultaneously, especially in busy hospitals. The presence of adipose tissue and pregnancy-induced softening of the soft tissues and ligaments can increase the false-positive rate when identifying the epidural space for labor analgesia, the combination of which accounts for a higher incidence of technical difficulty [4].
Depth of Puncture(DP)(cm)
Cell Biochem Biophys (2015) 71:875–880
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8
6
4
2
0 20
25
30
35 -2
Body Mass Index (BMI)(kg.m ) Fig. 2 The correlation between the epidural puncture depth and body mass index (BMI)
Epidural puncture is the golden standard for analgesia during labor in our center for more than fifteen years. Anesthesiologists often need to successfully do an epidural analgesia in the shortest delay possible, such that pain relief for nulliparous woman can be achieved within 10 min. We, therefore, need to administrate epidural puncture in advance in the delivery room. However, resident doctors sometimes encounter epidural complications such as perforation of dura mater, nerve damage, and nonnerve damage. We studied suitable depth parameter of epidural puncture in primipara so that this research work can help to decrease epidural complications such as perforation of dura mater or nerve damage. We also aim to provide anesthesia interns and resident physicians with an epidural puncture guide. Our study used multivariant gradual regressive analysis of effective puncture depth as dependent variable, to establish a regression equation. Regression equation was found to be PD = 0.351 [LHZ] ? 0.147 [BMI] ? 0.017. Our results, involving only nulliparous women for analgesia during labor, the distance for puncture points of L3,4 and of L2,3 was 5.05 ± 0.53 cm and 4.68 ± 0.74 cm, respectively. Previous studies have demonstrated a correlation between the distance from the skin to the lumbar epidural space with the BMI in a mixed population, consisting of obese and non-obese parturients [5–9]. The mean depth to the epidural space from the skin has been described as being in the range of 4.6–5.3 cm [5, 7], which is inconsistent with our result due to the difference in race. It is possible that the distance for obese pregnant women is more than 5.05 ± 0.53 cm, Balki [10] reported that the depth to the epidural space was more than 8 cm in only 17 % of the patients with a mean of 6.6 cm (range 4.5–8.5 cm). It is better to use a standard needle to identify the epidural space in the majority of obese women. BMI is a main marker for fat deposit, it reflects subcutaneous fat thickness as an independent variable and
predicts the lumbar epidural puncture depth. The epidural depth is discordant due to the spinal physiological curve, processus spinosus length in different vertebral body, and spinous process angulated to basivertebral cross section. Anatomical epidural depth is different at the three intervertebral levels, compared to L3–4 intervertebral space, the puncture depth for L1–2 and L2–3 was significantly shorter (P \ 0.05) and(P \ 0.001), respectively. In conclusion, prediction of regression equation is relatively simple, and data about body weight, height, and intervertebral space can be collected with facility. The doctor performing the procedure should consider the puncture depth scope according to the prediction value which equals to vertical puncture depth : the distance from skin to epidural space, the distance from ligamentum flavum to dura mater of spinal cord in median line of back (epidural interspace L3,4 the broadest 0.6 cm for the adult). If the depth from skin to epidural space reached or exceeded the predicted value in primiparas, the clinician should be wary of perforation of the dura mater. Our study suggests that L3,4 and L2,3 in the lumbar vertebra may optimize epidural catheter placement in parturients by providing a reasonable estimation of the depth to the epidural space and the skin puncture site. Acknowledgments The authors would like to acknowledge the nurses and midwives of the delivery room of our hospital for assisting in recruit nulliparous patients for this study. Conflict of interest The authors declared that they have no conflicts of interest to this work. Funding Perinatal Potential Subject (To International Peace Maternity and Child Health Hospital, Shanghai Jiaotong University School of Medicine in May, 2014).
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Cell Biochem Biophys (2015) 71:875–880 10. Balki, M., Lee, Y., Halpern, S., et al. (2009). Ultrasound imaging of the lumbar spine in the transverse plane: The correlation between estimated and actual depth to the epidural space in obese parturients. Anesthesia and Analgesia, 108(6), 1876–1881.
