Dose response of Intravenous Dexamethasone on post operative pain with Subarachnoid block in Lower limb Osteoarticular surgery

Acute postoperative pain causes patient discomfort and also impedes the recovery.  Regional blocks with long-acting local anaesthetics are helpful to achieve surgical anaesthesia and longer duration of post operative analgesia. Spinal anaesthesia is widely used in lower abdominal surgeries, as it plays a crucial role in relieving postoperative pain and enabling ambulatory anaesthesia1. It is safe, cost effective and easy to perform technique, which provides a denser block and so more preferred2.

Multimodal analgesia is method of pain management in which combined medication groups include (local anaesthetics, opioids, NSAIDS, acetaminophen and alpha-2 agonists, gabapentinoids, dexamethasone) are used for pain relief.

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 and post-operative pain3.

Dexamethasone is a potent long acting glucocorticoid with plasma half-life of 36 hrs having minimal mineralocorticoid activity, with anti-inflammatory and analgesic property. It is regarded as one of the ideal perioperative drugs being readily available, cheap, suppresses inflammation, prevent and treats postoperative nausea and vomiting, promotes appetite and provide good analgesia, when given intravenously and as an adjunct to peripheral nerve blocks. It provides good quality of recovery and early discharge of patients.

It acts on hypothalamic pituitary adrenal axis to produce its effect. Systemic administration of dexamethasone has been found to possess anti-inflammatory and immunosuppressive properties, which may contribute to prolonged analgesia when administered intravenously4.

Various studies suggest that intravenous dexamethasone as an adjunct with local anaesthetic prolongs the duration of spinal anaesthesia and also provides post-operative analgesia

IV administration of dexamethasone improves postoperative VAS score and decreases   overall postoperative analgesic consumption in patients given subarachnoid block with hyperbaric bupivacaine5. Higher dose of dexamethasone is superior to lower dose, although both prolongs analgesia and were effective in reducing postoperative opioid consumption.

Various studies show that duration of sensory and motor block was significantly higher in patient receiving higher dose of intravenous dexamethasone as compared to lower dose5,6

Lacunae in existing knowledge

However, to the best of our knowledge and also after searching quite a number of articles and extensive literature search, it has been found that no previous studies have compared the analgesic effect of two doses of intravenous dexamethasone, (0.15 mg/kg and 0.075 mg/kg) supplemented after subarachnoid block given with hyperbaric Bupivacaine in lower limb osteoarticular surgery. Therefore, we will compare the effects of two different doses of intravenous dexamethasone on postoperative pain in patients given subarachnoid block with 0.5% hyperbaric bupivacaine.