• Emma Wei Du, Hon Sen Tan, Chin Wen Tan, Rehena Sultana, and Ban Leong Sng.
• From the Department of Anaesthesiology, Singapore General Hospital (EWD), Department of Women's Anaesthesia, KK Women's and Children's Hospital (HST, CWT, BLS), Duke-NUS Medical School (HST, CWT, BLS) and Centre for Quantitative Medicine, Duke-NUS Medical School, Singapore, Singapore (RS).
• Eur J Anaesthesiol. 2022 Mar 1; 39 (3): 219-226.

BackgroundHypotension frequently occurs during spinal anaesthesia for caesarean delivery, with potential adverse effects.ObjectiveTo investigate heart rate variability and haemodynamic factors associated with spinal anaesthesia-induced hypotension.DesignSecondary case-control analysis of a randomised study.SettingSingle obstetric centre.PatientsData were obtained from 230 healthy term singleton parturients who underwent elective caesarean delivery under spinal anaesthesia.InterventionWith parturients at rest, continuous haemodynamic measurements were recorded using a Nexfin cardiac monitor. Baseline pre-operative values were defined as the average of five minutes of continuous measurements. After initiation of standardised spinal anaesthesia, vasopressors were administered to maintain SBP within 10% of pre-operative values. Hypotension was defined as any 10 seconds average SBP less than 80% of pre-operative values from initiation of spinal anaesthesia to foetal delivery. Parturients were classified into cases (hypotensive) or controls (normotensive), and both univariate and multivariable logistic regression models were used to identify independent factors associated with hypotension.Main Outcome MeasuresPre-operative standard deviation of the interbeat interval (SDNN), root mean square of successive interbeat difference, low-frequency to high-frequency ratio, SD1, SD2, approximate entropy, sample entropy, mean arterial pressure, SBP, stroke volume variation and systemic vascular resistance index were recorded, as were sensory block height, intravenous fluid volume and vasopressor use between spinal anaesthesia and foetal delivery.ResultsOf 230 parturients, 113 (49.1%) experienced hypotension. Pre-operative lower SDNN [odds ratio (OR) 0.87, 95% confidence interval (CI) 0.78 to 0.97], higher SD2 (OR 25.06, 95% CI 2.41 to 261.06), and lower SBP (OR 0.98, 95% CI 0.97 to 1.00) were independently associated with hypotension. Between spinal anaesthesia to foetal delivery, lower sensory block height (OR 0.76, 95% CI 0.65 to 0.90) and higher intravenous fluid volume (OR 0.98, 95% CI 0.96 to 0.99 per 15 ml change) were associated with a lower incidence of hypotension. Area under the receiver operating characteristic curve was 0.701.ConclusionPre-operative higher SD2, lower SDNN and lower SBP were associated with hypotension during spinal anaesthesia for caesarean delivery.Trial RegistrationNCT02277730.Copyright © 2021 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.

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