Effect of needle types and diameters using in spinal anesthesia on optic nerve sheath diameter: Prospective...

This prospective randomized study aimed to investigate the impact of needle types and diameters used in spinal anesthesia (SA) on optic nerve sheath diameter (ONSD) in patients undergoing lower extremity orthopedic surgery.

Patients were randomly assigned to 3 groups based on the needle type and size used for SA: Group 25w (25 gauge Whitacre needle), Group 27q (27 gauge Quincke needle), and Group 25q (25 gauge Quincke needle). Initially, 165 patients (55 in each group) were enrolled, with 146 patients ultimately included in the analysis (Group 25w, n = 49; Group 27q, n = 48; Group 25q, n = 49). ONSD measurements were conducted using ultrasound guidance at 5 time points: T0 (pre-SA), T1 (5 minutes post-SA), T2 (5 minutes post-tourniquet inflation), T3 (5 minutes post-tourniquet deflation), and T4 (24 hours post-operation). Additionally, oxygen saturation, systolic arterial pressure, mean arterial pressure, diastolic arterial pressure, and heart rate were recorded at these time points.

Analysis of ONSD measurements revealed no significant differences among the groups at time points T0,T1,T2, and T4 (P = .7293, P = .4428, P = .3676, and P = .3667, respectively). However, at T3, ONSD values were significantly higher in Group 27q compared to Group 25q (P = .0325). Across all groups, the mean ONSD values measured post-tourniquet release (T3) were higher than those at T0,T2, and T4 (P < .001 for all). The incidence of nausea was similar among the groups, and no cases of headache or visual impairment were reported within the initial 24 hours post-surgery.

In conclusion, our study suggests that while subarachnoid injection and tourniquet inflation do not impact intracranial pressure (ICP), tourniquet deflation leads to an increase in ICP during lower limb surgery under SA. Therefore, caution should be exercised when using a tourniquet in patients at risk of elevated ICP.