Intrathecal Injection of Hyperbaric Bupivacaine Versus a Mixture of Hyperbaric and Isobaric Bupivacaine in Patients Undergoing Lower Abdominal Surgery

Spinal anesthesia is one of the most commonly used nerve block procedures for surgical operations involving the lower abdomen, the perineum, and the lower limbs, owing to its quick effect and cost-effectiveness. Spinal anesthesia is advantageous in that it uses a small dose of anesthesia, is simple to perform, and offers a rapid onset of action, reliable surgical analgesia, and good muscle relaxation. The Baricity of a solution is defined as the ratio of the density of the solution to that of the cerebrospinal fluid (CSF). The most common anesthetic used for SA in obstetric and non-obstetric surgery is bupivacaine, which can be formulated as an isobaric or hyperbaric solution. Baricity differences between spinal anesthetic solutions are thought to affect hemodynamic parameters and distribution within the subarachnoid space, which may, in turn, affect the onset, extent, and duration of sensory block as well as side effects. Spinal anesthesia has been linked to different adverse effects, out of which hypotension is most common complication. The incidence of hypotension is 25-75% in general population. Factors that increase the risk of hypotension include patient factors (advanced age, pregnancy, obesity, diabetes mellitus, hypertension, and anemia) and technical factors such as a block level at or above T5, use of opioids during premedication, and high local anesthetic dosages.