RESUMO
BACKGROUND: Spinal anesthesia is optimal choice for transurethral resection of the prostate (TURP), but the sensory block should not cross the T10 level. With advancing age, the sensory blockade level increases after spinal injection in some patients with spinal canal stenosis. We optimize the dose of spinal anesthesia according to the decreased ratio of the dural sac cross-sectional area (DSCSA), the purpose of this study is to hypothesis that if DSCSA is an effective parameter to modify the dosage of spinal anesthetics to achieve a T10 blockade in geriatric patients undergoing TURP. METHODS: Sixty geriatric patients schedule for TURP surgery were enrolled in this study. All subjects were randomized divided into two groups, the ultrasound (group U) and the control (group C) groups, patient receive either a dose of 2 ml of 0.5% isobaric bupivacaine in group C, or a modified dose of 0.5% isobaric bupivacaine in group U. We measured the sagittal anteroposterior diameter (D) of the dural sac at the L3-4 level with ultrasound, and calculated the approximate DSCSA (A) according to the following formula: A = π(D/2)2, ( π = 3.14). The modified dosage of bupivacaine was adjusted according to the decreased ratio of the DSCSA. RESULTS: The cephalad spread of the sensory blockade level was significantly lower (P < 0.001) in group U (T10, range T7-T12) compared with group C (T3, range T2-T9). The dosage of bupivacaine was significantly decreased in group U compared with group C (P < 0.001). The regression times of the two segments were delay in group U compared with group C (P < 0.001). The maximal decrease in MAP was significantly higher in the group C than in group U after spinal injection (P < 0.001), without any modifications HR in either group. Eight patients in group C and two patients in group U required ephedrine (P = 0.038). CONCLUSIONS: The DSCSA is a highly effective parameter for spinal anesthesia in geriatric patients undergoing TURP, a modified dose of local anesthetic is a critical factor for controlling the sensory level. TRIAL REGISTRATION: This study was registered in the Chinese Clinical Trial Registry (Registration number: ChiCTR1800015566).on 8, April, 2018.