Effect of Spinal Needle Type on Optic Nerve Sheath Diameter

Spinal anesthesia will be performed in sitting position, with 25 G pencil point needle (Whitacre -Egemen®) midline through the L4-5 or L5-S1 interspace, parallel to the dural fibers. Upon clear cerebrospinal fluid (CSF) detection, the needle apertures will be turned towards the cephalad direction, and 3 ml (15 mg) of 0.5% hyperbaric bupivacaine (Marcaine Heavy ®) will be injected into the intrathecal space.

Spinal anesthesia will be performed in sitting position, with 25 G sharp edge needle (Quincke -Egemen®) midline through the L4-5 or L5-S1 interspace, parallel to the dural fibers. Upon clear cerebrospinal fluid (CSF) detection, the needle apertures will be turned towards the cephalad direction, and 3 ml (15 mg) of 0.5% hyperbaric bupivacaine (Marcaine Heavy ®) will be injected into the intrathecal space.

Spinal anesthesia will be performed in sitting position, with 27 G sharp edge needle (Quincke -Egemen®) midline through the L4-5 or L5-S1 interspace, parallel to the dural fibers. Upon clear cerebrospinal fluid (CSF) detection, the needle apertures will be turned towards the cephalad direction, and 3 ml (15 mg) of 0.5% hyperbaric bupivacaine (Marcaine Heavy ®) will be injected into the intrathecal space.

Sonographic measurement of ONSD (EsaoteMyLabFive, Cenova, Italy) for all patients will be performed by a single experienced anesthesiologist. After a thin gel layer apply to the upper eyelid, the patient in the supine position and with the eyes closed, using a 6-13 MHz linear probe, optic sheath nerve measurement will be done 3 mm behind the optic globe, with a total of three measurements of which the final value will be recorded.The measurement will be repeated five times using US guidance at the following time points: T0 (pre-anesthesia), T1 (5 minutes after spinal block), T2 (15 minutes after spinal block, T3 (tourniquet opening), and T4 (24 hours after spinal block ) respectively.