Measuring skin to subarachnoid space depth in Egyptian population: A prospective cohort study

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.