Heart rate variability as a predictor of hypotension following spinal for elective caesarean section: a prospective observational study
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, 05% 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.
Three-dimensional printing has rapidly become an easily accessible, innovative and versatile technology, with a vast range of applications across a wide range of industries. There has been a recent emergence in the scientific literature relating to its potential application across a multitude of fields within medicine and surgery; however, its use within anaesthesia has yet to be formally explored. We undertook a systematic review using MEDLINE and EMBASE databases of three-dimensional printing in anaesthesia. We identified eight relevant articles. Due to the paucity of studies, we also completed a narrative review of the applications of three-dimensional printing pertinent to anaesthetic practice that our department are currently exploring, and suggest potential future uses for this technology relevant to our speciality.
The primary goal of this study was to determine the median effective dose (ED50) of spinal chloroprocaine for labour analgesia. Thirty-eight parturients requesting neuraxial analgesia were enrolled. Doses of 1% chloroprocaine were determined by the technique of up–down sequential allocation, with an initial dose of 20 mg and steps of 2 mg. The chloroprocaine spinal dose was given as the spinal component of a combined spinal-epidural, which was then supplemented with an epidural dose of 7.5 μg sufentanil in 7 ml saline. Effective analgesia was defined as a score ≤ 10 mm within 15 min on a 100-mm visual analogue pain scale. Using the isotonic regression estimator method, the ED50 of chloroprocaine for the spinal component of a combined spinal-epidural for labour was calculated to be median (95% CI) 12.0 (9.3–17.0) mg.
The effect of remifentanil on propofol requirements to achieve loss of response to command vs. loss of response to pain
When providing total intravenous anaesthesia, careful selection of end-points is required in titrating dose to effect during induction. Although propofol and remifentanil have predominantly different pharmacodynamic effects, they are seen to interact in achieving loss of consciousness and analgesia. To highlight these differences, we performed a double-blind, randomised controlled trial, comparing one group of patients receiving propofol alone (n = 42) with another group receiving remifentanil plus propofol (n = 46) as a target-controlled infusion of remifentanil (Minto; 3 ng.ml−1). Propofol was also titrated using a target-controlled infusion (Marsh effect model) to produce loss of response to tactile and vocal stimuli, and subsequently to loss of response to pain. The effect-site concentration of propofol at which 50% of patients lost tactile/verbal response was 2.9 μg.ml−1 in the propofol only group and 2.4 μg.ml−1 in the remifentanil with propofol group. In contrast, loss of pain response occurred at 4.4 μg.ml−1 in the propofol group, and 2.7 μg.ml−1 in the remifentanil with propofol group, with correspondingly lower bispectral index values. Judicious use of analgesia in total intravenous anaesthesia can have a propofol-sparing effect and potentially minimise the suppression of brain electrical activity.