Purpose <p>Hypotension is the most common cause of delayed postoperative neurologic deficit (DPND). Based on previous findings, a 4-h postoperative intensive blood pressure (BP) monitoring protocol was implemented following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). This study aimed to determine the effectiveness of the 4-h postoperative intensive BP monitoring protocol as a predictive tool for identifying postoperative hypotensive events.</p> Methods <p>A case–control study was performed using a prospectively collected dataset of 103 AIS patients who underwent PSF. All patients received 4-h intensive BP monitoring postoperatively before transitioning to standard BP cuff monitoring. Patients who experienced at least one hypotensive event (HE; MAP &lt; 60) were designated as cases, while those with no hypotensive events (NHE) served as controls. Risk factors associated with hypotensive events were then analyzed using <i>t</i> tests and multivariable logistic regression.</p> Results <p>The 4-h postoperative intensive BP monitoring protocol identified 25% of postoperative HEs. The protocol demonstrated a sensitivity of 25%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 88%. Preoperative weight differed significantly between cases and controls (<i>p</i> = 0.02); however, the association did not persist on multivariate analysis. No patients experienced DPND or neurologic deficits.</p> Conclusion <p>The 4-h monitoring protocol identified 25% of HEs, suggesting limited predictive capacity. the protocol demonstrated a sensitivity of 25%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 88%. Hypotensive events remain difficult to predict, illustrating the importance of frequent blood pressure monitoring postoperatively and quick hypotensive response capabilities.</p>