An Observational Study to Compare Spinal Anesthesia-Induced Hemodynamic Changes in Normotensive and Hypertensive Patients on Antihypertensive Medications

Abstract

Background: Spinal anesthesia is a popular and widely used anesthetic technique for lower abdominal, pelvic, and lower limb surgery. It has proven to be a convenient, economical, and easily motivated technique that provides excellent anesthesia and post-operative analgesia. Hypotension and bradycardia occur frequently following spinal anesthesia due to blockade of sympathetic outflow. Antihypertensive agents decrease this effect by controlling blood pressure. There are conflicting reports on the continuation of antihypertensive drugs on the day of surgery in patients undergoing spinal anesthesia. Sudden hypotension could have detrimental effect on the organ systems. This study was undertaken to compare the spinal anesthesia-induced hemodynamic changes in normotensive and in hypertensive patients on antihypertensive therapy. Methods: The study was conducted in the Department of Anesthesiology, Gandhi Medical College, and associated Hamidia Hospital Bhopal during January 2019–July 2020. It was an observational study conducted on 100 patients of ASA Grade 2 and Grade 3 in the age group between 35 and 60 years. Undergoing lower limb surgery under spinal anesthesia, patients were allocated into two groups: Group N (n=50) normotensive and Group H (n=50) hypertensive patients receiving antihypertensive medication. Results: Incidence of hypotension was significantly higher in Group II patients. Single episode of hypotension was seen in 12 (24.0%) patients in Group I and 33 (66.0%) in Group II patients respectively. Three episodes of hypotension were seen in 3 (6.0%) Group I and 4 (8.0%) Group II patients, respectively. The frequency of administration of mephentermine was 2 times more significant in Group II who required treatment with mephentermine more than twice as compared to Group I (p=0.001). There was statistically no significant difference found in mean Heart rate between Group I (normotensive) and Group II (hypertensive), respectively (p>0.05). Conclusion: Antihypertensive medications decreased the incidence of hypotension by controlling blood pressure but their varying effects on the cardiovascular system might alter the hemodynamics during the initial phase of subarachnoid block. We found that patients on antihypertensive therapy (calcium channel blockers) had increased incidence of intraoperative hypotension after SAB and when compared to normotensive patients required vasopressors more often to maintain normal blood pressure.