The effect of preeclampsia on the skin to subarachnoid distance in spinal anesthesia.

Abstract

Preeclampsia is characterized by increased extracellular fluid which manifests as generalized edema due to endothelial injury and subsequent capillary leak. Therefore, preeclampsia may lead to increased skin to subarachnoid distance (SSD) which may influence daily clinical practice in this particular gravid population. Age- and height-matched gravidas with and without preeclampsia were enrolled prospectively at an allocation ratio of 1:4. Spinal anesthesia (SA) was performed in a sitting position by a mid-line approach at the L3-L4 interspace using a 25-gauge Quincke spinal needle. An internal pilot study was performed to determine the sample size. When the protocol violations were excluded, 146 gravidas were included in the study (25 preeclamptics and 121 normotensive controls) for final analysis. On average, SSD was 0.89 cm greater in preeclamptics compared to normotensive controls. Mean values of the SSD in preeclamptic and normotensive control group patients at the L3-L4 interspace were 6.187 ± 0.967 and 5.301 ± 0.834 cm, respectively. SSD was significantly correlated with body weight and body mass index (BMI). The regression formula for the estimation of SSD in preeclamptic gravidas with BMI during SA was SSD = 3.696 + 0.075×BMI. The regression formula for the estimation of SSD in the normotensive control group with BMI during SA was SSD = 3.144 + 0.067×BMI - 0.0001×BMI×BMI. Knowing that the SSD is increased in preeclamptics compared to normotensive gravidas may be of value in terms of selecting needle, and providing safe and comfortable anesthesia.