Comparative Evaluation of Magnesium Sulphate Versus Dexamethasone as an Adjuvant to Bupivacaine in Ultrasound Guided Transversus Abdominis Plane Block for Abdominal Hysterectomy as Postoperative Analgesia

Total abdominal hysterectomy (TAH) is accompanied by an extensive inflammatory response resulting in postoperative discomfort and misery. Such patients require appropriate analgesic treatment to reduce morbidity and complications by blunting autonomic, somatic, and endocrine reflexes. As a result, postoperative analgesia following TAH calls for a multimodal approach.

One of the regional techniques routinely used is the transversus abdominis plane (TAP) block. Its widespread use in abdominal surgeries is due to its technical simplicity and trustworthy analgesia. This block implies administering local anesthetic between the internal oblique muscle and transversus abdominis muscle, which is marked by the lumbar Petit triangle. The primary drawback of single-shot regional blocks is their short duration of action when administered with local anesthetic alone. Several adjuvants, including opioids, alpha 2 agonists, N-methylD-aspartate (NMDA) receptor antagonists, and other drugs, have been utilized to extend the duration of blocks. Opioids are by far the most often used adjuvants, but they accompany a host of unpleasant side effects, such as respiratory depression, drowsiness, nausea, and vomiting. In some studies, using alpha 2 agonists such as Dexmedetomidine and Clonidine has been related to drowsiness and bradycardia.

MgSO4 is an N-methyl-D-aspartate (NMDA) receptor antagonist. It acts by non-competitive antagonism blocking the voltage-dependent ion channels.

Dexamethasone is a highly potent, long-acting glucocorticoid. It inhibits potassium conductance by binding to glucocorticoid receptors which decrease the activity of nociceptive C-fibres and may also prolong the analgesia duration through systemic anti'-inflammatory effects and local vasoconstrictive action.