1. What data in particular will be shared?
   Response - Individual participant data that underlie the results reported in this article, after de-identification (text, tables, figures, and appendices).
   


2. What additional supporting information will be shared?
   Response -  Study Protocol
   Response -  Statistical Analysis Plan
   Response - Informed Consent Form
   Response - Clinical Study Report
   Response -  Analytic Code
   
   
3. Who will be able to view these files?
   Response - Researchers whose proposed use of the data has been approved by an independent review committee identified for this purpose.
   


4. For what types of analyses will this data be available?
   Response - To achieve aims in the approved proposal.
   


5. By what mechanism will data be made available?
   Response - Proposals should be directed to [drsuniljoejacob@gmail.com].
   


6. For how long will this data be available start date provided 24-06-2028 and end date provided 24-06-2038?
   Response - Immediately following publication. No end date.
   


7. Any URL or additional information regarding plan/policy for sharing IPD? 
   Additional Information - NIL

This prospective observational study will be conducted in the Departments of Anaesthesiology and Intensive Care in collaboration with Department of Neurosurgery after Institutional Ethics Committee approval. Adult patients undergoing thoracolumbar and lumbar neurosurgical procedures in the prone position will be enrolled following written informed consent. All participants will undergo standard pre-anaesthetic evaluation including detailed history, clinical examination, and review of laboratory and imaging investigations. Routine medications will be continued until the morning of surgery and standard fasting guidelines followed.

In the operating room, standard ASA monitors along with BIS, ABG, TOF, and invasive arterial blood pressure monitoring will be instituted. Anaesthesia will be induced with propofol using target-controlled infusion (Eleveld model), fentanyl, and rocuronium, followed by tracheal intubation. Maintenance will include propofol TCI titrated to maintain BIS 40–60, fentanyl infusion, and rocuronium with volume-controlled ventilation adjusted to maintain normocapnia.

Baseline haemodynamic and Carotid Doppler parameters will be recorded after induction. Fluid preloading with 6 ml/kg hydroxyethyl starch will be administered, followed by reassessment. Patients will then be positioned prone using the dual transverse roll technique, and Carotid Doppler parameters reassessed after stabilization. Carotid Doppler parameters and pulse pressure variation will be recorded hourly until surgery completion. At the end of surgery, patient will be made supine and final measurements will be taken. Neuromuscular blockade will be reversed; trachea will be extubated once patient meets the extubation criteria, and patient will be shifted to Intensive Care Unit (ICU) for further management.