179🔬 USG-Optic Nerve Sheath Diameter (ONSD) | Real-Time ICP Monitoring Without Invasive Probes?

🧠 Can an anesthesiologist detect rising intracranial pressure (ICP) intraoperatively — without invasive monitoring? The answer is yes. Using nothing more than a bedside ultrasound probe, real-time ICP changes can be inferred through ultrasonographic measurement of the optic nerve sheath diameter (ONSD). 📖 This lecture provides a comprehensive, evidence-based review of ONSD for anesthesiologists, intensivists, residents, and medical students — covering the anatomical rationale, measurement technique, technical pitfalls, and perioperative clinical applications. 🔍 Topics Covered Anatomical and physiological basis of ONSD as a noninvasive ICP surrogate — subarachnoid space continuity and CSF dynamics Normative reference values — CT-based adult data (Vaiman 2015) and ultrasound-based pediatric values (Newman 2002) Methodology matters — comparing 4 ultrasound marker placement techniques and their impact on ICP sensitivity (Stevens 2021) Technical pitfalls and imaging artifacts — gain, harmonic imaging, focal zones, acoustic shadowing, comet tail, partial volume effect, and refraction artifact (Hirzallah 2025) ONSD POCUS Quality Criteria Checklist (QCC) ONSD changes during laparoscopic surgery — systematic review & meta-analysis of CO₂ pneumoperitoneum effects (Kim EJ 2018) Reverse Trendelenburg laparoscopic upper abdominal surgery — intraoperative ONSD monitoring patterns (Cesur 2026) Propofol vs inhalational anesthetics in steep Trendelenburg position — which agent better attenuates ICP? (Yang 2021) ONSD elevation and inadequate emergence from anesthesia in robot-assisted laparoscopic prostatectomy (Bang 2021) Spinal anesthesia needle type and tourniquet effects on ONSD (Kumaş Solak 2024) Pediatric applications — ONSD vs transcranial Doppler for noninvasive ICP monitoring in the PICU (Sharawat 2020) Current limitations and future directions — threshold variability, standardization, trend monitoring, and TCCD integration (Robba 2019) 🎯 Whether you are a resident learning ONSD for the first time or an experienced clinician considering its integration into perioperative practice, this review lecture offers a rigorous and practical framework. #ONSD #OpticNerveSheathDiameter #IntracranialPressure #NonInvasiveICP #AnesthesiaPOCUS #LaparoscopicAnesthesia #PointOfCareUltrasound #PerioperativeMonitoring #CriticalCare #AnesthesiaReview #TrendelenburgPosition #Propofol #SpinalAnesthesia #PediatricAnesthesia #IntraoperativeMonitoring #AnesthesiologyEducation #NeuroAnesthesia #ICP