Ultrasound guided suprainguinal fascia iliaca compartment block for proximal femoral nailing surgeries under spinal anaesthesia Comparison of efficacy of combination of dexamethasone and dexmedetomidine as adjuvants versus dexamethasone alone with ropivacaine

Ultrasound‑guided fascia iliaca compartment block (FICB), commonly practicing regional technique in proximal femur surgery, for providing effective postoperative analgesia with comparatively less adverse effects. FICB is a procedure that acts by blocking several nerves namely femoral nerve, lateral femoral cutaneous nerve, and obturator nerve. However, single injection technique of FICB is effective for postoperative pain management, it is often inadequate, as postoperative pain can persist for many days.

Many studies demonstrated the effectiveness of various local anaesthetic drugs in FICB. Local anaesthetic drugs like bupivacaine, levobupivacaine, and ropivacaine are the commonly using agents. At low concentrations these local anaesthetic agents produces only sensory block without affecting motor function. Various additives such as opioids, dexamethasone, α-adrenergic agonists (clonidine, dexmedetomidine) are routinely combined with local anaesthetic drugs to magnify the duration of analgesia and shortens the onset of block. Combining two additive agents can improve patient control and enable the use of lower doses of each individual agent without causing unfavourable side effects.

Levobupivacaine is an S-enantiomer of bupivacaine that appears to exhibit less cardiovascular toxicity than bupivacaine. It also has a better efficacy and safety profile. Dexamethasone is a long-acting glucocorticosteroid, numerous studies have shown that, it was highly efficient when used as an adjuvant to local anaesthetics. Short-term use (> 24 h) of single dose of dexamethasone is observed to be safe with infrequent adverse effects. Many researches used dexamethasone in a dose of 8 mg to increase the duration of analgesia. However, some investigations have used less than 8 mg dose of dexamethasone and concluded acceptable outcome. Dexmedetomidine is an α2 agonist, when added to local anaesthetics in peripheral nerve blocks, it improves the quality of anaesthesia as well as increases postoperative analgesia.

The mechanism of dexamethasone and dexmedetomidine in improving the duration of local anaesthetics action are not clearly explained. Both dexamethasone and dexmedetomidine can effectively decreases local inflammation and extend the duration of block through vasoconstriction by conserving the local concentration of the local anesthetic. Vasoconstriction also supress the nociceptive impulse transmission along myelinated C fibers. In peripheral nerve blockade dexmedetomidine appears to involve in suppression of hyperpolarization-activated cation current, thereby preventing the nerve from reverting to its resting membrane potential. Additionally, some investigations reveals that dexmedetomidine may operate as a

local anaesthetic by inhibiting the conduction of nerve signals through C and Aδ fibres rather than through α2 action.

In view of their distinct modes of action, we postulated that levobupivacaine in combination with dexamethasone and dexmedetomidine may further extend he duration of peripheral nerve blocks. Therefore, we conducted this prospective, randomized trial to investigate whether the addition of two adjuvants (dexmedetomidine and dexamethasone) to levobupivacaine for FICB improves the duration of postoperative analgesia, as compared with each adjuvant alone with levobupivacaine. We also examined the quality of block, haemodynamic variations, level of sedation and adverse effects across the groups as secondary outcomes.