The Analgesic Efficacy of Dexmedetomidine Versus Fentanyl as an Adjuvant to Bupivacaine in Ultrasound Guided Peripheral Nerve Blocks as a Solo Anesthetic Technique in High Risk Patients Undergoing Unilateral Above Knee Amputation .

Above knee amputation (AKA) is a major surgical procedure often performed for non salvageable lower limb such as severe trauma , peripheral arterial diseases or infection . however it carries significant risks and complications . The overall mortality and morbidity rates are also substantial, with one-year mortality rates reported as high as 40-50% in some populations.

Anesthesia in above-knee amputation procedures poses its own set of risks, especially in patients with advanced age or multiple comorbidities. General anesthesia (GA) may be associated with postoperative pulmonary complications, prolonged recovery, and hemodynamic instability. On the other hand, spinal anesthesia offers benefits such as reduced thromboembolic events and faster postoperative recovery, but carries risks including hypotension, spinal hematoma, and post-dural puncture headache .

Peripheral nerve blocks (PNBs) as a solo anesthetic technique offer significant hemodynamic advantages compared to neuroaxial and general anesthesia , this makes them especially beneficial for patients with cardiovascular compromise or bad chest conditions.

Effective pain management is crucial to improve patient outcomes, promoting early mobilization, and reducing the risks of complications such as deep vein thrombosis or chronic pain syndromes .

Patients with multiple risk factors such as cardiovascular disease, respiratory problems have a higher risk of complications when general or spinal anesthesia is used. In such cases ultrasound guided regional anesthesia becomes an excellent alternative .. So The combination of supra-inguinal fascia iliaca block and sciatic nerve block has emerged as a promising regional anesthetic approach for above-knee amputation, particularly in patients who are poor candidates for general or neuraxial anesthesia. This technique provides comprehensive coverage of the femoral, lateral femoral cutaneous, obturator, and sciatic nerves, allowing for adequate surgical anesthesia without the need for airway manipulation. It offers advantages such as hemodynamic stability, reduced opioid consumption, and fewer respiratory complications, making it especially beneficial in elderly and high-risk patients. When performed under ultrasound guidance, this approach enhances block accuracy and safety, positioning it as a viable solo anesthetic technique for AKA. The technique allows for adequate surgical anesthesia with preserved hemodynamic stability and minimal systemic drug exposure. Clinical reports have demonstrated its success in providing effective anesthesia with high patient and surgeon satisfaction, especially when performed under ultrasound guidance.

Dexmedetomidine is a selective alpha 2- adrenoceptor agonist possessing sedative, anxiolytic, and analgesic properties which could improve the quality of the block while reducing opioid consumption and their associated side effects. It reduces pain after knee arthroscopy mainly by peripheral and central mechanisms through stimulation of presynaptic α2- adrenoceptors .

On the other hand, fentanyl, an opioid, is commonly used to provide potent analgesia in regional blocks but carries risks of respiratory depression and other opioid-related complications . There over, this study aims to compare dexmedetomidine versus fentanyl as adjuvant to bupivacaine in ultrasound-guided supra inguinal fascia iliaca and sciatic nerve block for anesthetic management for unilateral above knee amputation in high risk patients as a solo anesthetic technique ..

While several studies have evaluated the efficacy of peripheral nerve blocks in lower limb surgeries, few have investigated their use as a sole anesthetic technique specifically in high-risk patients undergoing above-knee amputation (AKA). Moreover, the comparative role of different adjuvants such as dexmedetomidine versus fentanyl in this setting remains underexplored. There is a clear need for well-designed randomized trials to guide anesthetic decision-making in this fragile patient population.

Inclusion criteria

• - Age ≥18 years
• Both sexes
• ASA III-IV
• Documented cardiac disease (e.g., EF < 40%, NYHA II or higher)
• Documented pulmonary disease (e.g., COPD with FEV1 < 60%)
• Scheduled for above-knee amputations

Exclusion criteria

• Neurological or intellectual disability
• Drug abuse
• Allergy to study drugs
• Pregnancy
• Contraindications to regional anesthesia (e.g., coagulopathy, local infection)
• Significant renal or hepatic impairment( plts <75000 or INR >1.5)
• Current anticoagulant therapy
• severe haemodynamically unstability at the time of block performance, defined as map > 65 mmhg but achieved by high-dose vasopressors (e.g., norepinephrine ≥ 0.1 mcg/kg/min) after fluid ressuscitation .