1. What is this study about, and why is it required?

   The goal of this observational study is to learn if anesthesia type (e.g., general anesthesia, spinal anesthesia) affects the safety and efficiency of HoLEP surgery. The main question it aims to answer is:

   - Is a particular type of anesthesia related to less or more bleeding during the surgery?

2. What will be assessed to answer the main question of this study? (Outcome measure(s))

   2.1. Primary outcome measure of this study is:

   - Change in the hemoglobin level perioperatively.

   2.2. Secondary outcome measures are:

   • Requirement for the usage of any vasoactive medication due to low blood pressure
   • Time passed until discharge.
   • Time passed until the removal of the bladder drainage catheter.
   • Ratio of the unwanted events that require additional intervention other than medication, fluids, or blood transfusions (Complications, Clavien-Dindo Grade III or higher).
   • International symptom questionnaire score 3 months after surgery.
   • Quality of life (QoL) score 3 months after surgery.
   • Peak urinary current velocity (Qmax) and post-void residual volume measurement 3 months after surgery.

3. Can anyone participate in this study?

Voluntary participants should meet the following criteria:

• Being older than 18 years old.
• Having bothersome lower urinary tract symptoms due to prostatic enlargement requiring surgical treatment.
• Having no untreated or uncontrolled systemic disease, which refers to having an ASA (American Society of Anesthesiologists Physical Status Classification System) score III at most.

Benign prostatic obstruction (BPO) is the leading cause of lower urinary tract symptoms (LUTS) among men older than 40 years.

Surgery is recommended under circumstances such as:

• Bothersome LUTS resistant to medical treatment.
• Acute kidney injury, bladder stone(s), resistant hematuria and urinary retention.
• Preference of the patient.

Various surgical methods exist to treat BPO, but the most appropriate choice depends on the operator and the patient.

HoLEP is an abbreviation for holmium laser enucleation of prostate, which is one of the endoscopic laser enucleation techniques.

Both spinal and general anesthesia are applicable for HoLEP surgery. The type of anesthesia is determined by the anesthesiologist, independently of the operator's preference, taking into account several factors related to the patient, such as safety and comfort.

Controlled bleeding is one of the expected outcomes in HoLEP, and several factors determine the amount of bleeding. For HoLEP, the type of anesthesia may be one of them, as other studies have claimed. This multicenter, prospective observational study may further reveal the impact of anesthesia type on bleeding.

The amount of bleeding could be "less or more", determined according to the content below:

• Amount of hemoglobin and hematocrit decreased, measured by laboratory examinations, preoperatively, during, and on the day after the surgery.
• Vital changes such as hypotension, tachycardia, that require blood transfusion due to "more" bleeding during either the surgery or hospital stay after surgery.
• Usually, a shorter duration of bladder irrigation to clean blood in the urine during hospital stay after the surgery is required for "less" bleeding.

Participants who are eligible and willing to provide informed consent will undergo HoLEP. Preoperative, perioperative, and postoperative data will be collected without disclosing the participant or any personal data relating to the participant.

Participants will be grouped into two groups based on anesthesia type: general or spinal.

To answer the main question of this study, a power analysis was conducted, concluding that at least 320 participants are required (intention-to-treat population).

All collected data will be recorded and analyzed according to the proper statistical methods. Results will be reported.

Inclusion Criteria:

• 18 years or older men who have BPO requiring surgical treatment.
• Participants who can give written informed consent.
• Having no more than 3 points for the American Society of Anesthesiologists (ASA) physical status classification scale (ASA 1 to 3).

Exclusion Criteria:

• Absolute contraindication for spinal or general anesthesia
• History of previous surgery for prostate (e.g., surgery for prostate cancer, surgery for benign prostate obstruction)
• Uncorrected bleeding disorder (INR > 1.5)
• Participants who are not willing to give informed consent.
• Participants who have a proven urinary tract infection at the time of the surgery.
• Participants who are not able to be contacted for regular follow-ups.

Male patients undergoing HoLEP for BPO.

Individual participant data (IPD) will not be shared due to privacy concerns and data protection regulations, including the Turkish Personal Data Protection Law (KVKK).

Only aggregated, de-identified results will be reported in publications and presentations.