Effect of Wound Infiltration With Tramadol, Dexmedetomidine, or Magnesium Sulfate as Adjuncts to the Local Anesthetic on Pain Relief After Spine Surgery

The rationale for multimodal analgesia is to achieve additive or synergistic analgesic properties while decreasing the incidence of side effects by reducing the dose of each agent. Nociceptive stimuli are known to activate the release of the excitatory amino acid glutamate in the dorsal horn of the spinal cord. The resultant activation of NMDA receptors causes calcium entry into the cell and triggers central sensitization. This mechanism is involved in the perception of pain and mainly accounts for its persistence during the postoperative period.

Peri-incisional injection of local anesthetics is an effective method for pain relief after many surgical procedures, as it can reduce postoperative analgesic consumption. Ropivacaine is a propyl analog of bupivacaine with a longer duration of action with a much safer cardiotoxicity profile than bupivacaine. Thus, a combination of local anesthetic with other analgesic factors, such as opioids, dexmedetomidine, clonidine, ketamine, magnesium sulfate, dexamethasone is suggested for a better analgesic outcome.

Dexmedetomidine, a highly selective a2-adrenergic receptor agonist, has been the focus of interest for its broad spectrum (sedative, analgesic, and anesthetic sparing) properties, making it a useful and safe adjunct in many clinical applications. The intravenous, intramuscular, intrathecal, epidural, and perineural use of this agent enhances analgesic effects.

Tramadol hydrochloride is a synthetic analog of codeine that acts on both opioid (weak m receptor agonist) and nonopioid receptors (inhibits the reuptake of noradrenaline and serotonin as well as release stored serotonin from nerve endings) which play a crucial role in pain inhibition pathway. It also blocks nerve conduction which imparts its local anesthetics like action on peripheral nerves.

It was reported that NMDA antagonists could prolong the analgesic effect of bupivacaine to even a week, as well as inhibit hyperalgesia. Magnesium sulfate (MGS) is a non-competitive antagonist of N-methyl, D-aspartate (NMDA) receptors with an analgesic effect and is essential for the release of acetylcholine from the presynaptic terminals and, similar to calcium channel blockers (CCB), can prevent the entry of calcium into the cell.

Aim of the study is to evaluate and compare the postoperative analgesic efficacy of tramadol, dexmedetomidine, and magnesium when added to ropivacaine as an adjuvant for wound infiltration following spine surgery.