COMPARATIVE EVALUATION OF BUPIVACAINE VS LEVOBUPIVACAINE FOR DURATION OF ANALGESIA IN SUBARACHNOID BLOCK SUPPLEMENTED WITH INTRAVENOUS DEXAMETHASONE IN LOWER ABDOMINAL SURGERIES

Adequate postoperative analgesia is central to avoid both the acute as well as chronic complications of uncontrolled postoperative pain. An optimal multimodal regimen may be determined based on identifying efficacious, safe, and inexpensive analgesic interventions. Key components of an optimal multimodal analgesic regimen include the preoperative identification of patients at high risk for postoperative pain in addition to patient and caregiver education. Unless contraindicated, all patients should receive a combination of acetaminophen, non-steroidal anti-inflammatory drug or cyclo-oxygenase-2-specific inhibitor, dexamethasone, and procedure-specific regional analgesic technique and/or surgical site local anaesthetic infiltration.[1] Multimodal analgesia approaches have been suggested to manage postoperative pain. One of these is the injection of dexamethasone. Acute inflammation induced by tissue damage has a major role in development of postoperative pain, nausea, and vomiting. Therefore, dexamethasone should be useful in lowering pain, nausea, and vomiting, due to its potential anti- inflammatory effect.[1] Dexamethasone is potent, selective glucocorticoid having minimal mineralocorticoid action. Systemic anti-inflammatory and immunosuppressive properties may be responsible for the prolongation of analgesia when administered intravenously. It has nerve block prolonging effect by blocking transmission of nociceptive myelinated c-fibres and suppressing ectopic neuronal discharge and plasma half-life of >36 hours. [2] It has been found that many drugs, such as opioids (morphine, fentanyl, and sufentanil), α2 adrenergic agonists (dexmedetomidine and clonidine), magnesium sulphate, neostigmine, ketamine, and midazolam, can be used as adjuvants for intrathecal local anaesthetics to improve the quality of spinal anaesthesia. During the intrathecal administration, fentanyl has a more rapid onset and shorter duration of action than morphine, which has become one of the most used neuraxial opioids.[3] Bupivacaine at a concentration of 0.5%, became popular and a drug of choice giving spinal anaesthesia because of its long-term block, sensory block separated from the motor block. Bupivacaine also promotes opioid binding to kappa-opioid receptors, which reduces pruritus. In recent years Levobupivacaine, effective long-acting amide, the pure S (¬) enantiomer of bupivacaine, emerged as a safer alternative for regional anaesthesia than its racemic parent. It demonstrated less affinity and strength of depressant effects on to myocardial and central nervous vital centres in pharmacodynamics studies, and a superior pharmacokinetic profile.[4] Prevention of postoperative pain and post discharge nausea and vomiting requires a multimodal management approach using both pharmacologic and nonpharmacologic interventions. The short half-life of ondansetron (approximately 3h) effectively covers the typical ambulatory post anaesthesia care unit stay.[5] Nonetheless, there is considerable worry about the potential side effects of dexamethasone treatment in the peri-operative context due to the well-known negative effects of corticosteroid use. As an illustration, corticosteroids are known to raise blood glucose levels through promoting insulin resistance and hepatic gluconeogenesis and this could be linked to poor results in people who are critically unwell or recovering from surgery.  Studies have shown that patients given dexamethasone prior to surgery experience postoperative hyperglycaemia.[6]

Lacunae in existing knowledge

However, after extensive literature search, it has been found that previous studies have been done for evaluating the sensory duration of subarachnoid block with hyperbaric bupivacaine supplemented with intravenous dexamethasone.But Uncertainty remains on the potential increase in the duration of sensory block after spinal anaesthesia. Nonetheless, there is no study that showed the duration of analgesia with hyperbaric bupivacaine or levobupivacaine in spinal anaesthesia supplemented with intravenous dexamethasone in lower abdominal surgeries.