Ketamine for Preventing Post-Spinal Hypotension in Orthopedic Surgery

Impact of Sub-anesthetic Dose of Ketamine in the Prevention of Post Spinal Hypotension in Patients Undergoing Orthopedic Surgeries

This randomized, double-blind, controlled clinical trial investigates the efficacy of a sub-anesthetic dose of ketamine (0.5 mg/kg IV) in preventing post-spinal hypotension in patients undergoing elective orthopedic surgeries under spinal anesthesia. The study compares ketamine with placebo (normal saline) in terms of blood pressure stability and incidence of hypotensive episodes following spinal anesthesia.

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.

Inclusion Criteria:

• Patients American Society of Anesthesiologists Physical Status (ASA) I to II undergoing orthopedic surgeries under spinal anesthesia.
• Both Sexes.
• Patients aged equal to or above 18 years.
• Body mass index <35 kg/m2
• Duration of operation from 1 hour to 3 hours

Exclusion Criteria:

• Patients' refusal of procedure or participation in the study.
• Patients with contraindication to spinal anesthesia.
• Patients with cardiovascular or pulmonary disease.
• Patients with pre-procedural hypotension (systolic arterial pressure less than 90 mmHg and/or mean arterial pressure less than 60 mmHg).
• Patients aged below 18 years.
• Duration of operation below 1 hour or above 3 hours.