Giving a second course of IVIG to patients who stayed in refractory GBS may harm the patient. It increases thromboembolic complications. There is no added benefit. A recent study published by the Dutch GBS study group showed no benefit, rather harm.
It was a randomized, double-blind, placebo-controlled trial. Patients were randomly assigned after eligibility for poor prognosis through modified Erasmus Guillain-Barré syndrome Outcome Score. The primary outcome measure was the Guillain-Barré syndrome disability score after 4 weeks. The study spanned over 8 years (Feb 2010 - June 2018). Out of total 337 patients, 93 patients with poor prognosis were included in the modified intention-to-treat analysis: 49 received second course of IVIG, and 44 received placebo. Patients in the treatment group had more serious adverse events (35% vs 16% in the first 30 days), including thromboembolic events. Four patients died in the intervention group (13-24 weeks after randomization).
Walgaard C, Jacobs BC, Lingsma HF, et al. Second intravenous immunoglobulin dose in patients with Guillain-Barré syndrome with poor prognosis (SID-GBS): a double-blind, randomised, placebo-controlled trial. Lancet Neurol. 2021;20(4):275-283. doi:10.1016/S1474-4422(20)30494-4