title: The Relationship Between Patients' Anthropometric Characteristics and Depth of Spinal Needle Insertion.
abstract: BACKGROUND
  Many surgeries are performed under spinal anesthesia. Inexperienced practitioners may find it difficult to obtain subarachnoid access.
  
  
  OBJECTIVE
  This study aimed to examine the relationship between patients' anthropometric characteristics and depth of spinal needle insertion to the subarachnoid cavity.
  
  
  METHODS
  385 patients with ASA class I - II, aged 18 - 65 years and undergoing elective surgery of the lower abdomen and extremities under spinal anesthesia, were selected for this cross-sectional study. The patients' demographic characteristics, body mass index (BMI), and anthropometric characteristics (height, weight, waist circumference, and arm circumference) were recorded. Linear regression and t-student tests were used to study the relationship between anthropometric characteristics and BMI, and depth of needle insertion.
  
  
  RESULTS
  Of the 385 patients studied, 88 were female and 297 were male. There was a strong correlation between the depth of needle insertion and BMI (24.9 ± 3.9), and between depth and weight/height ratio (r = 0.95 and r = 0.92, respectively). There was no significant correlation between depth of needle insertion and weight, height, gender, or arm circumference, when considered separately. The statistical predicting models showed that the following relationship was observed between the needle depth and the weight/height ratio: A: needle depth = 0.69 + (10.1 × weight/height); B: needle depth = 0.56 + (0.18 × BMI).
  
  
  CONCLUSIONS
  The results of this study show that there is a strong relationship between depth of needle insertion and BMI, and between depth and the weight/height ratio; appropriate depths can be determined according to the equations obtained.
authors.affiliation: Trauma Research Center, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Razavizadeh
authors.affiliation: Trauma Research Center, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Fazel
authors.affiliation: Department of Anesthesiology, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Mosavi
authors.affiliation: Department of Community Medicine, Kashan University of Medical Sciences, Kashan, Iran.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Sehat
keywords: Distance Perception; Needles; Spinal Puncture