This Study Aims to Determine Whether Lower Doses (4 µg) of Intrathecal Dexmedetomidine Can Provide Comparable Analgesic Benefits While Minimizing Adverse Hemodynamic Effects in Patients Encountered in Our Setup( Shifa International Hospital Islamabad).

"Effect of adding low-dose intrathecal dexmedetomidine to hyperbaric bupivacaine on the duration and quality of spinal anesthesia in knee arthroplasty." This study aims to determine whether lower doses (4 µg) of intrathecal dexmedetomidine can provide comparable analgesic benefits while minimizing adverse hemodynamic effects in patients encountered in our setup( Shifa International Hospital Islamabad). Studies conducted earlier in other setups have used hyperbaric 0.5% bupivacaine but this study will use 0.75% bupivacaine.

Objectives Primary Objective To compare the time to first postoperative analgesia request between patients receiving intrathecal 0.75% hyperbaric bupivacaine alone and those receiving intrathecal dexmedetomidine as an adjunct.

Secondary Objectives

• To compare the duration of sensory block between two groups.
• To compare the duration of motor block between two groups.
• To evaluate intraoperative and postoperative hemodynamic stability ( Heart rate and Mean Arterial Pressures).
• To determine the incidence of adverse effects (bradycardia, hypotension, nausea, sedation) in both groups.

Methodology Study design Quasi-experimental, non-randomized controlled design Study setting

• Department of anesthesia, Shifa International Hospital Ltd. Study duration
• 12 Months Sample Size and Study Groups Total 60 patients (30 per group) based on power analysis.

Group A: 1.5 mL of 0.75% hyperbaric bupivacaine + 4 µg dexmedetomidine + Normal Saline to make total volume 2.0 mL Group B (Control): 1.5 mL of 0.75% hyperbaric bupivacaine + 0.5 mL Normal Saline to make total volume 2.0 mL Inclusion Criteria

• Patients aged between 18 and 60 years
• Classified as ASA physical status II-III
• Scheduled for elective lower limb joint replacement surgeries ( total knee replacement [TKR])
• Written informed consent Exclusion Criteria
• Allergy to study drugs
• Contraindications to spinal anesthesia
• History of cardiac conduction abnormalities or severe bradycardia
• Neurological or psychiatric illness
• Pregnancy or lactation

Grouping Method A total of 60 participants will be included in the study. Participants will be allocated into intervention and comparison groups based on the treating physician's clinical judgement.. Group I (intervention group) will consist of participants who will receive dexmedetomidine, while Group II (comparison group) will consist of participants who will not receive the dexmedetomidine.

Drug Preparation and Administration Dexmedetomidine (100 µg/mL) will be drawn using an insulin syringe for accuracy and will be added in 9 ml Normal Saline (Total 10 ml) to make a concentration of 10 µg/mL.

For 4 µg: 0.4 mL dexmedetomidine (10 µg/mL) diluted with normal saline to make 0.5 mL will be prepared in an insulin syringe.

The control group will receive 0.5 mL saline in an insulin syringe. All solutions will be clear and identical, prepared immediately before injection. Each patient will receive a total of 2.0 mL intrathecally at L3-L4 or L4-L5 using a 25G Quincke needle.

Outcome Measures

Primary Outcome:

• Time from spinal injection to first postoperative analgesic request.

Secondary Outcomes:

• Total analgesic consumption in 24 hours
• The duration of the sensory and motor block and how they gradually wear off over time
• Hemodynamic parameters (HR, MAP)
• Sedation score (Ramsay Sedation Scale).
• Incidence of adverse events (bradycardia, hypotension, nausea, shivering)

Timeline Total duration: 12 months ( 8 months data collection, 2 months analysis, 2 months reporting).