|Year : 2016 | Volume
| Issue : 3 | Page : 468-472
Measuring skin to subarachnoid space depth in Egyptian population: A prospective cohort study
Hani Ibrahim Taman1, Ahmed Mohamed Farid1, Waleed Mohamed Abdelghaffar2
1 Department of Anesthesia and Surgical Intensive Care, Mansoura Faculty of Medicine, Mansoura University, Mansoura, Egypt
2 Department of Gynecology and Obstetrics, Mansoura Faculty of Medicine, Mansoura University, Mansoura, Egypt
|Date of Web Publication||27-Sep-2016|
Hani Ibrahim Taman
Building No 7, Flat No 9, 10 Gehan Street, Masaken Heat Eltadrees, Mansoura, Dakahlya
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Lumbar puncture is a difficult medical skill and is used for administering subarachnoid anesthetic medications. Estimation of skin to subarachnoid space depth (SSD) helps to reduce post spinal anesthetic complications.
Aims: To measure the SDD in overall Egyptian population and to find a formula for predicting SSD in Egyptian patients.
Settings and Design: Four hundred patients of American Society of Anesthesiologist class I and II adult Egyptian patients undergoing surgery using spinal anesthesia in general and obstetric surgery unit, Mansoura University main hospital, were included in this prospective, observational study.
Subjects and Methods: Patients were divided into three groups: Males (Group M), nonpregnant females (Group F), and pregnant females (Group PF). SSD was measured after performing lumbar puncture. The relationship between SSD and patient characteristics was studied; correlated and statistical analysis was used to find a formula for predicting SSD.
Statistical Analysis Used: Statistical analysis was done using Statistical Package for Social Sciences (SPSS 19.0, Chicago, IL, USA). One-way ANOVA with post hoc (Bonferroni correction factor) analysis was applied to compare the three groups. All the covariates in the study further were taken for multivariate analysis. Multivariate regression analysis was performed to evaluate important covariates influencing SSD for each group separately.
Results: Mean SSD was 4.99 ± 0.48 cm in the overall population. SSD in adult males (4.93 ± 0.47 cm) was significantly longer than that observed in females (4.22 ± 0.49 cm) but was comparable with SSD in parturient (4.32 ± 0.47 cm). Formula for predicting SSD in the overall population was 2.1+ (0.009 × height) + (0.03 × weight) + (0.02 × body mass index [BMI]) + (0.15 × body surface area [BSA]). Craig's formula when applied correlated best with the observed SSD.
Conclusions: SSD in adult males was significantly longer than that in both pregnant and nonpregnant females, but it was nearly the same in pregnant and nonpregnant females. SSD in Egyptian population can be calculated based on height, weight, BMI, and BSA. Craig's formula was the most suitable to be applied to Egyptian population.
Keywords: Intrathecal, lumbar puncture, predictive formulae, subarachnoid space depth
|How to cite this article:|
Taman HI, Farid AM, Abdelghaffar WM. Measuring skin to subarachnoid space depth in Egyptian population: A prospective cohort study. Anesth Essays Res 2016;10:468-72
|How to cite this URL:|
Taman HI, Farid AM, Abdelghaffar WM. Measuring skin to subarachnoid space depth in Egyptian population: A prospective cohort study. Anesth Essays Res [serial online] 2016 [cited 2020 Aug 4];10:468-72. Available from: http://www.aeronline.org/text.asp?2016/10/3/468/179312
| Introduction|| |
Lumbar puncture is routinely learned by the junior staff, for administering subarachnoid anesthetic medications through observation then practicing under supervision by an expert physician who has mastered this technique. It is a difficult medical skill because success is dependent on the skill of the physician and the size, anatomy, and comfort of the patient.
An estimation of skin to subarachnoid space depth (SSD) helps to guide spinal needle placement that results in less traumatic or bloody lumbar puncture and reduces unsuccessful and repeated attempts which may worsen the outcome of patients.
Although many studies have focused on estimating SSD with different methods to enable the estimation of the skin to epidural distance for clinical practice in obstetric and pediatric population,, those focusing on SSD in the adult Egyptian population are few and have not evaluated differences, if any, based on gender.
This study hypothesis that remarkable differences in SSD between males, females, and pregnant females would be present in Egyptian populations.
The primary goal of this study was to measure the SSD at the L3–L4 interspace in overall Egyptian population, male, females, and pregnant females and to find differences in SSD between them. The secondary goal was to find formulae for predicting SSD in Egyptian population and to determine which of the previously known formulae (Abe's, Bonadio's, Craig's, Stocker's, and Chong's modified formula) for estimating SSD is appropriate in use for Egyptian.
| Subjects and Methods|| |
After approval from the Research and Ethics Committee of Mansoura University, Mansoura, Egypt, a written informed consent was obtained from 400 adult Egyptian patients of either sex, with American Society of Anesthesiologist I and Π , scheduled for elective surgical procedures using spinal anesthesia in general and obstetric surgery unit, Mansoura University main hospital, were included in this prospective, observational study.
Patient characteristics including name, gender, age, body weight, body height, body surface area (BSA), and body mass index (BMI) were recorded upon arrival to the operating theater. Patients who refused spinal anesthesia or had any hematological or neurological pathology were excluded from the study. All patients had received premedication as per our hospital protocol.
All patients were monitored using electrocardiogram, pulse oximetry, and noninvasive blood pressure and received 10 ml/kg Ringer's lactate solution as preload after intravenous line insertion.
The patients were placed in the sitting position with their back fully flexed and under aseptic precautions. The L3 and L4 intervertebral space were identified by palpatory method, using the Tuffier's line as guide. Puncture of the dura was performed using a 25-gauge Quincke (3.5 inches) spinal needle through the midline approach. The spinal needle was inserted perpendicular to the skin and advanced until loss of resistance was just felt and confirmed by the first appearance of the free flow of cerebrospinal fluid. Patients with bloody cerebrospinal fluid and those in whom either the angle of spinal needle was not perpendicular or the approach was changed from midline to paramedian were excluded from the study. The dose of intrathecal local anesthetic was calculated depending on surgical requirement and patient characteristics. After giving the intrathecal injection, the spinal needle was marked using a sterile skin-marking pen then grasped firmly between the thumb and the index finger abutting the patient's back and removed. The depth of insertion was then measured using a standard scale and noted.
All patients who had completed this study were divided into three groups: Males (Group M), nonpregnant females (Group F), and pregnant females (Group PF).
For all patients, Mosteller formula  BSA (m 2) = ([Height (cm) × weight (kg)]/3600)½ was used for calculation of BSA and BMI was calculated using Quetelet index  (BMI = Weight in kg/height in m 2).
Abe's, Bonadio's, Craig's, Stocker's, and Chong's modified formulae were calculated individually to all the patients to determine predicted SSD in the overall population.
Abe's formula: SSD (cm) = 17 weight (kg)/height (cm) +1
Bonadio's formula: SSD (cm) = 0.77cm + 2.56 × BSA (m 2)
Craig's formula: SSD (cm) = 0.03 cm × height (cm)
Stocker's formula: SSD (mm) = 0.5 × weight (kg) +18
Chong's modified formula: SSD (cm) = 10 weight (kg)/height (cm) +1.
Statistical analysis was done using IBM Corp. Released 2010 (IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY: IBM Corp). One-way ANOVA with post hoc (Bonferroni correction factor) analysis was applied to compare the three groups. All the covariates in the study further were taken for multivariate analysis. Multivariate regression analysis was performed to evaluate important covariates influencing SSD for each group separately. 95% confidence intervals were presented. Independent sample t-tests were used to find significant mean differences between the predicted depth of spinal needle and observed depth of spinal needle separately. P = 0.05 was considered statistically significant level.
| Results|| |
From a total of 400 eligible patients, only 392 patients had completed this study, from which 170 were males, 134 were females who were not pregnant, and 88 were pregnant. The remaining eight patients were excluded as a result of protocol violations. No adverse events were reported during the surgeries and 48 h postoperatively.
Patient's characteristics for overall population are shown in [Table 1]. Both the calculated values of SSD by different formulae and the actual measured SDD in the overall study population are presented in [Table 2]. The difference in mean of actual measured SDD in the overall study population and the calculated means of SSD by different formulae was 3.78 cm, 0.82 cm, 0.15 cm, 0.49 cm, and 0.85 cm when Abe's, Bonadio's, Craig's, Stocker's, and Chong's modified formulae were applied to our study population, respectively. The observed SSD in the overall study population was 4.99 ± 0.48 cm. The mean of actual measured SDD in the overall study population was significantly lower than the calculated means of SSD by Abe's, Chong's modified formulae, and Bonadio's and showed no significant difference when compared to that obtained by Craig's and Stocker's formulae; also the mean of actual measured SDD in the overall study population correlated best with Craig's and Stocker's formulae; thus, in terms of accuracy, it was next to Craig's and Stocker's formulae [Figure 1]. The observed SSD showed strong correlation with height, weight, BMI, and BSA in the overall study population.
|Table 2: Mean difference between the predicted skin to subarachnoid space depth using various formulae and the observed subarachnoid space in the overall study population|
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|Figure 1: Skin to subarachnoid space depth in the overall study population using various formulae, data are presented as mean ± SD. *P< 0.05 significant when the observed SSD compared with the predicted skin to subarachnoid space depth using various formulae. †r< 0.05 significant when the observed SSD correlated with the predicted skin to subarachnoid space depth usning various formulae|
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Patient characteristics and SSD of the three groups (males, nonpregnant females, and pregnant females) are presented in [Table 3] and [Table 4], respectively. Male patients group height, weight, BSA, actual measured SDD, calculated SSD by Abe's, Bonadio's, Stocker's, Craig's, and Chong's modified formulae were significantly higher when compared to nonpregnant females and pregnant females groups individually, and the last two group showed no significance differences between them. Furthermore, BMI was higher in male group than pregnant female only.
|Table 4: The skin to subarachnoid space depth, observed and predicted, using various formulae in the three study groups|
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A multivariate regression analysis was performed to determine covariates (age, weight, height, BMI, and BSA) that determine SSD [Table 5]. In male group, correlation was seen with height and BSA. In nonpregnant group, SDD correlated well with BMI, weight, and BSA; and with height, BSA and BMI in pregnant group.
|Table 5: Multivariate regression analysis to determine covariates that influence skin to subarachnoid space depth in the studied groups|
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The formulae derived from this study for predicting SSD in the overall population and in the three study groups (males, nonpregnant females, and pregnant females) are presented in [Table 6].
|Table 6: Formulae for predicting skin to subarachnoid space depth derived from our study|
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| Discussion|| |
The mean SDD measured in general Egyptian population was 4.99 ± 0.48 cm. The SSD was significantly longer in the adult male patient when compared to both adult nonpregnant and adult pregnant female patients separately, but it was insignificant when compared between adult pregnant and nonpregnant female patients.
Craig et al. formulae  and Stocker andBonsu formulae  results were the most accurate, one in calculating the SDD, but Abe et al., Chong et al., and Bonadio et al. results were far away from the measured SDD in Egyptian population as a whole and in adult male, pregnant, and nonpregnant female individually.
SDD in Egyptian population is 4.99 ± 0.48 cm that is 0.41 cm shorter than SDD measure in Turkish population (5.40 ± 0.66 cm) by Basgul et al. and also is 1.51 cm shorter than SSD in the European population (6.5 ± 1.2 cm) which was measured by Bassiakou et al. This can be explained by the fact that Egyptian population are shorter and less heavy compared to the Western population.
SDD in adult male patients is 4.93 ± 0.47 cm which is 0.47 cm shorter than that measured by Vassiliadis et al. in adult male (5.4 ± 0.7 cm).
The SSD was significantly longer in adult male patient, when compared to both adult nonpregnant and adult pregnant female patients separately. This may be explained by fat collection in the subcutaneous tissue which is common in Egyptian female population and the effects of pregnancy hormones such as weight gain, softening of tissues, and ligaments in pregnant patients.
Height, weight, BMI, and BSA were used in this study to design a mathematical equations for determining SSD in the overall adult population, male, nonpregnant, and pregnant females. Other old formulae were based upon pediatric population studies such as Bonadio et al., Craig et al., Stocker and Bonsu, and Chong et al., but Abe et al. derived a formula for predicting SSD from lumbar puncture depth in adult patients using computed tomography scan.
Craig et al. formula  was the closest one when applied to Egyptian population and is only 0.15 cm longer than the actual measured distance, and it is characterized by being simple, easy to remember, and use only height as the only variable.
Other formula in this study had longer values than predicted, and may lead to selecting spinal needle and excess projection of the needle shaft beyond the skin and this may cause difficulty in controlling the needle while administrating the drug intrathecally, also it may increase the risk of traumatic tap or nerve injury.,
In this study, SSD in the overall population and three groups is depends greatly on BMI, and this matches the results proved by Bassiakou et al. who also reported correlation between SSD, BMI, and body weight in all patients.
Vassiliadis et al. found a positive correlation of SSD with age but not with weight, height, and BMI in adult male patients but this study proved a strong correlation of SSD with height and BSA.
This study tried to find a strong based formula for accurate estimation of the depth to reach subarachnoid space to be an alternative for spinal ultrasound which offers an accurate estimation of the depth to reach subarachnoid space. However, economic aspects may cause inaccessibility to the expensive ultrasound equipment and needs for training together with the lack of skill in performing ultrasound-guided neuraxial approach may limit its role in determining the SSD.
All formulae derived from this study are only applicable when midline approach is used with perpendicular insertion of the spinal needle to the skin. When paramedian approach was used, or congenital deformities of the spine are present, it will be no longer useful and that is the most important limitation of our study.
| Conclusions|| |
SSD in adult males was significantly longer than that in both pregnant and nonpregnant females, but it was nearly the same in pregnant and nonpregnant females.
SDD in Egyptian population can be calculated based on Craig et al., formulae  which were the most suitable to be applied in the Egyptian population.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]