The role of carotid flow time in the management of hypotension following spinal anesthesia in patients undergoing cesarean section

The Role of Carotid Flow Time in the Management of Hypotension Following Spinal Anesthesia in Patients Undergoing Cesarean Section Objective: The primary aim of the study is to determine the impact of fluid preload administered to patients with preanesthetic FTc value below the cut-off value on the incidence of hypotension. The secondary goal is to determine the predictive value of pre-anesthetic FTc for postspinal hypotension during cesarean delivery. Materials and Methods: A prospective observational controlled study was planned, including female patients aged 20-40 years who were scheduled for cesarean section and classified as ASA (American Society of Anesthesiologists) II. Patients in the preoperative care unit were assigned to two separate groups based on their initial FTc cut-off values. The first group (n=36) consisted of patients with preoperative baseline FTc(W) < 327 ms. These patients received a 500 ml bolus of Ringer's lactate solution. The measurement was repeated after 20 minutes, and if FTc(W) < 327 ms persisted, an additional 500 ml bolus of Ringer's lactate solution was administered. Minimal fluid loading was continued until FTc(W) exceeded 327 ms. In the second group (n=36), patients with preoperative FTc(W) > 327 ms did not receive preload fluids. The demographic data, vital signs, administered fluid amounts and types, vasopressor requirements, sensory block levels, and side effects were recorded for all patients. To prevent hypotension following spinal anesthesia, noradrenaline was initially used, followed by intravenous Ringer's Lactate and/or HES as a second option. Results: There were no significant differences observed between the groups in terms of age, height, weight, body mass index, ASA classification, gestational week, and SpO2, HR, SBP, DBP, and MAP values. However, between minutes 6 and 50, it was found that the mean blood pressure values in the preload group were significantly lower compared to the control group. Post-spinal anesthesia hypotension occurred in 3 patients (8.8%) in the preload group, while it was observed in 5 patients (13.6%) in the group without preload based on FTc values. The incidence of hypotension was similar in both groups and below the expected rate (<20%). Sensory block development at the T5 level was observed in 69% of patients in the preload group, while it was observed in 58% of patients at the T6 level in the control group. When considering all patients who developed hypotension, 62.5% of them had a block level at T4, while only 7.8% of patients without hypotension (5 out of 64 patients) had a block level at T4. No patient developed sensory block above the T4 level. The fasting duration in the preload group was determined to be an average of 11.83±2.31 hours, while the average fasting duration in the control group was 9.16±1.02 hours. The preoperative baseline FTc values were found to be an average of 298.11±16.33 ms in the preload group, while it was 336.52±5.65 ms in the control group. Among patients with an initial FTc value below the cutoff (<327 ms), the majority of patients (33 patients, 91.7%) did not reach the target cutoff value after a 500 ml fluid load. It was determined that achieving the target value with only 500 ml of fluid was possible if the initial measured FTc value was above 308 ms. However, for values below this threshold (<308 ms), it was predicted that patients would likely require 1000-1500 ml of fluid (91.7% probability). Conclusion: The study has demonstrated that the reliable use of FTc values can help prevent hypotension following spinal anesthesia in pregnant women undergoing cesarean section. It can also guide early intervention options for patients who are at risk of developing hypotension. Keywords: Spinal anaesthesia, hypotension, corrected flow time, caesarean sectİon