Ketamine for Preventing Post-Spinal Hypotension in Orthopedic Surgery

Spinal anesthesia is commonly used for orthopedic procedures due to its effectiveness and favorable recovery profile. However, spinal-induced hypotension is a frequent complication resulting from sympathetic blockade, which can compromise organ perfusion and increase perioperative risk. This study aims to determine whether a single sub-anesthetic dose of intravenous ketamine administered before spinal anesthesia can reduce the incidence of hypotension. Patients will be randomly allocated to either a ketamine group (receiving 0.5 mg/kg ketamine IV diluted in Ringer's lactate) or a control group (receiving volume-equivalent normal saline). Both interventions are administered over 20 minutes prior to the spinal injection to ensure blinding. All patients will undergo standard spinal anesthesia with 0.5% heavy bupivacaine plus fentanyl. Primary outcome is the incidence of hypotension (defined as a mean arterial pressure drop \>20% from baseline). Secondary outcomes include bradycardia, nausea, vomiting, hallucinations, and total dose of vasopressors required. The findings aim to support or refute the use of ketamine as a prophylactic strategy to stabilize hemodynamics during spinal anesthesia.