title: Heart rate variability as a predictor of hypotension following spinal for elective caesarean section: a prospective observational study.
abstract: Post-spinal hypotension remains a common and clinically-important problem during caesarean section, and accurate pre-operative prediction of this complication might enhance clinical management. We conducted a prospective, single-centre, observational study of heart rate variability in 102 patients undergoing elective caesarean section in a South African regional hospital. We performed Holter recording for ≥ 5 min in the hour preceding spinal anaesthesia. The low-frequency/high-frequency ratio component of heart rate variability was compared, using a logistic regression model, with baseline heart rate and body mass index (BMI) as a predictor of hypotension (defined as systolic arterial pressure < 90 mmHg) occurring from the time of spinal insertion until 15 min after delivery of the baby. We also assessed clinically relevant cut-point estimations for low-frequency/high-frequency ratio. Low-frequency/high-frequency ratio predicted hypotension (p = 0.046; OR 1.478, 95%CI 1.008-1.014), with an optimal cut-point estimation of 2.0; this threshold predicted hypotension better than previously determined thresholds (p = 0.003; c-statistic 0.645). Baseline heart rate (p = 0.20; OR 1.022, 95%CI 0.988-1.057) and BMI (p = 0.60; OR 1.017, 95%CI 0.954-1.085) did not predict hypotension. Heart rate variability analysis is a potentially useful clinical tool for the prediction of hypotension. Future studies should consider a low-frequency/high-frequency ratio threshold of 2.0 for prospective validation.
authors.affiliation: Metropolitan Department of Anaesthetics, Critical Care and Pain Management, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
authors.forename: D G
authors.initials: DG
authors.lastname: Bishop
authors.affiliation: Metropolitan Department of Anaesthetics, Critical Care and Pain Management, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
authors.forename: C
authors.initials: C
authors.lastname: Cairns
authors.affiliation: Metropolitan Department of Anaesthetics, Critical Care and Pain Management, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
authors.forename: M
authors.initials: M
authors.lastname: Grobbelaar
authors.affiliation: Metropolitan Department of Anaesthetics, Critical Care and Pain Management, University of KwaZulu-Natal, Pietermaritzburg, South Africa.|Outcomes Research Consortium, Cleveland, Ohio, USA.
authors.forename: R N
authors.initials: RN
authors.lastname: Rodseth
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects; D015992:Body Mass Index; D002585:Cesarean Section / Q000379:methods*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007022:Hypotension / Q000175:diagnosis* / Q000209:etiology*; D007231:Infant, Newborn; D011237:Predictive Value of Tests; D011247:Pregnancy; D011379:Prognosis; D011446:Prospective Studies
keywords: caesarean section; heart rate variability; obstetric; prediction; spinal hypotension