KUMJ | VOL. 21 | NO. 3 | ISSUE 83 | JULY-SEPTEMBER. 2023
Ultrasound Guided Estimation of Skin to Subarachnoid Space Depth in Patients Scheduled for Elective Surgeries under Subarachnoid Block
Devkota S, Baral BK, Poudel PR
Abstract: Background
Subarachnoid block is one of the commonly used techniques of regional anesthesia
and accurate placement of spinal needle is crucial. A conventional spinal needle
may be too long for a lean patient or too short in obese patients leading to multiple
attempts, inadvertent nerve injuries and patient discomfort. So a pre-procedural
estimation of the skin to subarachnoid space depth may be beneficial.
Objective
To estimate the skin to subarachnoid space depth using ultrasound and correlate it
with the length of spinal needle to be inserted during subarachnoid block.
Method
This was a prospective, observational study conducted at Bir Hospital, Kathmandu in
patients undergoing elective surgeries under subarachnoid block. A pre-procedural
ultrasound of lumbo-sacral spine using 2-5 Hz curvilinear probe was done to measure
skin to subarachnoid space depth (SSD) at the level of L3-L4 interspace. Then under
all aseptic precautions, subarachnoid block was performed and the length of spinal
needle outside the skin was measured and that length was subtracted from the
standard length of needle to get the inserted length of spinal needle. These two
measurements were compared.
Result
In the fifty patients included in the study, ultrasound estimated skin to subarachnoid
space depth was found to be 4.24 ± 0.48 cm and the inserted length of spinal needle
was 4.24 ± 0.46 cm. A significant correlation r=0.96 (p < 0.05) was found between the
two measurements in the study population.
Conclusion
Ultrasound estimated skin to subarachnoid depth in the study population was found
to be 4.24 ± 0.48 cm which correlated with the inserted length of spinal needle. So,
use of ultrasound can be very helpful in performing subarachnoid block.
Keyword : Skin to subarachnoid space depth, Spinal needle, Subarachnoid block, Ultrasound
