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Abstract Summary 92 Neuraxial block involves spinal anesthesia, epidural anesthesia and combined spinal epidural anesthesia. S.A is used widely for both lower limbs and lower abdominal surgeries. It gives good sensory and motor block, reduces incidence of D.V.T and pulmonary embolism, provides postoperative pain relief and early ambulation. Epidural anesthesia is used for upper abdominal and thoracic surgeries, also as a supplement to general anesthesia for providing excellent control of chronic pain. Neuraxial block is achieved by sympathetic block which lead to decrease venous return to the heart and decrease systemic vascular resistance after blockade of preganglionic sympathetic fibers that causes hypotension. Hypotension is defined as systolic blood pressure less than 90 mmHg or decrease from baseline more than 30%. Preoperative hypotension should be corrected to reduce morbidity and mortality. Prevention of hypotension is of utmost importance. Several techniques and modalities can be used together as no single technique proves its efficacy. Various measures are used such as Trendelenburg position, leg wrapping, lateral left tilt, volume preloading and vasopressors. Fluids used in preloading or co-loading varies between crystalloids and colloids. Crystalloids have short half- life so their expansion abilities are limited. While colloids have longer half-life so they are able to maintain the increase in intravascular volume. Consequently, less volume is required. Colloids are more effective than crystalloid in preloading to prevent hypotension during neuraxial block. Judicious use of vasopressors such as ephedrine and phenylephrine will maintain CO and decrease incidence of hypotension so keep hemodynamics stable. Ephedrine is a mixed α and β receptor agonist. Its mechanism is both direct (binds and stimulates receptors) and indirect (causes release of noradrenaline from presynaptic vesicles). Ephedrine causes an increase in cardiac contractility, HR, CO and systolic and diastolic BP. Phenylephrine is chemically related to adrenaline but pharmacodynamically similar to noradrenaline. It is a potent, rapidly-acting vasopressor with a short duration of action. It increases systolic and diastolic BP in a dose-dependent manner. Neuraxial block is used for elderly patients with caution of hypotension to avoid organ hypoperfusion. Neuraxial block is done widely in obstetric practice to avoid complication of general anesthesia such as difficult intubation, aspiration and fetal hypoxia. Correction of preoperative hemodynamic changes will reduce both maternal and fetal morbidity and mortality. Obstetric patients are more susceptible to hypotension due to aortocaval compression so techniques like left lateral tilt and co-loading with colloid solutions are widely used. Good perioperative management of hypertensive patients by controlling blood pressure will protect patients from end organ damage due to hypotension which may have detrimental effects. Anticipation and early management of hypotension especially in obstetric, cardiac and hypertensive patients will improve outcomes and decrease postoperative morbidity, mortality and hospital stay. |