Subclavian vein ultrasound-guided fluid management to prevent post-spinal anesthetic hypotension during cesarean delivery: a randomized controlled trial

BACKGROUND: Hypotension frequently occurs after spinal anesthesia during cesarean delivery, and fluid loading is recommended for its prevention. We evaluated the efficacy of subclavian vein (SCV) ultrasound (US)-guided volume optimization in preventing hypotension after spinal anesthesia during cesarean delivery. METHODS: This randomized controlled study included 80 consecutive full-term parturients scheduled for cesarean delivery under spinal anesthesia. The women were randomly divided into the SCVUS group, with SCVUS analysis before spinal anesthesia with SCVUS-guided volume management, and the control group without SCVUS assessment. The SCVUS group received 3 mL/kg crystalloid fluid challenges repeatedly within 3 min with a 1-min interval based on the SCV collapsibility index (SCVCI), while the control group received a fixed dose (10 mL/kg). Incidence of post-spinal anesthetic hypotension was the primary outcome. Total fluid volume, vasopressor dosage, changes in hemodynamic parameters, maternal adverse effects, and neonatal status were secondary outcomes. RESULTS: The total fluid volume was significantly higher in the control group than in the SCVUS group (690 [650–757.5] vs. 160 [80–360] mL, p < 0.001), while the phenylephrine dose (0 [0–40] vs. 0 [0–30] µg, p = 0.276) and incidence of post-spinal anesthetic hypotension (65% vs. 60%, p = 0.950) were comparable between both the groups. The incidence of maternal adverse effects, including nausea/vomiting and bradycardia (12.5% vs. 17.5%, p = 0.531 and 7.5% vs. 5%, p = 1.00, respectively), and neonatal outcomes (Apgar scores) were comparable between the groups. SCVCI correlated with the amount of fluid administered (R = 0.885, p < 0.001). CONCLUSIONS: SCVUS-guided volume management did not ameliorate post-spinal anesthetic hypotension but reduced the volume of the preload required before spinal anesthesia. Reducing preload volume did not increase the incidence of maternal and neonatal adverse effects nor did it increase the total vasopressor dose. Moreover, reducing preload volume could relieve the heart burden of parturients, which has high clinical significance. CLINICAL TRIAL REGISTRATION: The trial was registered with the Chinese Clinical Trial Registry at chictr.org.cn (registration number, ChiCTR2100055050) on December 31, 2021. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-023-02242-6.