Efficacy of Intravenous Dexamethasone in Prolonging the Duration of Spinal Anesthesia With Chloroprocaine in Knee Arthroscopy

This is a monocenter, prospective, randomized (1:1 ratio), controlled, parallel-group, double-blind, phase III superiority trial assessing the efficacy and the safety of IV dexamethasone for prolonging sensory block in patients undergoing knee arthroscopy under spinal anesthesia with chloroprocaine.

Participants will be randomly allocated into two groups:

* Group CHLORO (control group): Patients will receive spinal anesthesia with chloroprocaine 40mg (Clorotekal®10 mg/mL, solution for injection, 4 mL) combined with an IV infusion of 3 mL of normal saline solution diluted in 100 mL of 0.9% sodium chloride, administered over 20 minutes. * Group CHLORODEX (experimental group): Patients will receive spinal anesthesia with chloroprocaine 40 mg (Clorotekal®10 mg/mL, solution for injection, 4 mL) combined with an IV infusion of dexamethasone at a dose of 0.15 mg/Kg (maximum 16 mg), diluted in 100 mL of 0.9% sodium chloride, administered over 20 minutes.

To ensure blinding, study infusions (saline or dexamethasone) will be prepared in identical 100 mL bags and labelled by a pharmacy staff member or an "outside protocol" healthcare professional (physician or nurse) not involved in patient care or assessment.

The infusion will start approximately 10-15 minutes before the spinal punction.

In the operating room, patients will receive standard perioperative care for spinal anesthesia, including placement of a peripheral intravenous line, supplemental low-flow oxygen therapy to maintain SpO₂ \> 93%, continuous hemodynamic monitoring, and strict aseptic precautions. Analgesic premedication with paracetamol combined with either ketoprofen or celecoxib will be administered according to institutional practice.

Spinal anesthesia will be performed with the patient in a semi-sitting position via the L3-L4 or L4-L5 interspace using a 25G x 80mm Sprotte needle. After cerebrospinal fluid reflux, 40 mg of chloroprocaine without adjuvant will be injected intrathecally, and patients will then be positioned in the supine position for the procedure.

Knee arthroscopy will be performed according to standard surgical practice, without any modification of the surgical procedure for study purposes.

No additional sedation or analgesia will be administered during the procedure. In the event of failure of spinal anesthesia or early recovery of sensation, conversion to general anesthesia or deep sedation may be performed at the discretion of the anesthesiologist, depending on the clinical situation.

Postoperatively, multimodal analgesia will be initiated according to the institutional protocol, combining paracetamol, nefopam, and either ketoprofen or celecoxib, with morphine administered if necessary.

Sensory and motor blocks will be assessed every 5 minutes after spinal puncture until regression of two dermatomes and then every 10 minutes until recovery of four dermatomes and complete motor function (maximum until hospital discharge).

Motor block will be assessed using the Bromage score and sensory block will be assessed using the Pin Prick test and the cold test.

The primary objective of the study is to evaluate the efficacy of intravenous dexamethasone in prolonging sensory block following spinal anesthesia with chloroprocaine, as assessed by the time from intrathecal injection to regression of sensory block by two dermatomes from the highest level of sensory block achieved, as measured by the pin-prick test.

• Time to complete resolution of motor block [Срок оценки: Up to 8 hours following spinal anesthesia]
• Time to regression of sensory block by four dermatomes (pin-prick test) [Срок оценки: Up to 8 hours following spinal anesthesia]
• Maximum sensory block level [Срок оценки: Up to 30 minutes following spinal anesthesia]
• Time to maximum sensory block level [Срок оценки: Up to 30 minutes following spinal anesthesia]
• Need for additional anesthetic procedure [Срок оценки: From spinal anesthesia to the end of surgery]
• Time to regression of sensory block by two dermatomes (cold test) [Срок оценки: Up to 2 hours following spinal anesthesia]
• Incidence of hypotension [Срок оценки: From spinal anesthesia to 24 hours after surgery]
• Incidence of bradycardia [Срок оценки: From spinal anesthesia to 24 hours after surgery]
• Incidence of nausea [Срок оценки: From spinal anesthesia to 24 hours after surgery]
• Incidence of vomiting [Срок оценки: From spinal anesthesia to 24 hours after surgery]
• Incidence of pruritus [Срок оценки: From spinal anesthesia to 24 hours after surgery]
• Incidence of urinary retention [Срок оценки: From spinal anesthesia to 24 hours after surgery]