Measurement artifacts are common in hemodynamic recordings such as cardiac output and blood pressure. Manual artifact removal is cumbersome for large datasets, and automatic processing using algorithms may reduce workload and provide more reproducible outcomes. This paper presents an artifact removal algorithm which is more aggressive compared to a previously described method. The algorithm was evaluated on cardiac output (CO) and mean arterial pressure (MAP) recordings from 23 subjects measured by two different devices (LiDCO and Nexfin), and compared to the previously described method as a reference. Precision, recall and F-score was determined by agreement with manual inspection by an expert. Based on the total of all measurements from CO and MAP by LiDCO and CO and MAP by Nexfin, precision was 86%, 79%, 79% and 68% respectively (87%, 62%, 76% and 58% for the reference method), recall was 97%, 94%, 89% and 97% (31%, 6%, 28% and 6% for reference), F-score was 91%, 85%, 84% and 80% (46%, 10%, 41% and 10% for reference). The proposed algorithm offers an improved performance in removing true artifacts, in some cases a reduced ability to preserve true measurements, but an improved overall accuracy.

BackgroundOnvision is a new technology for needle tip detection and tracking in ultrasound-guided regional anesthesia. The system consists of a piezoelectric sensor close to the needle tip and an electronic console integrated in the ultrasound system. The needle tip is visualized by a green circle on the ultrasound screen. The aim of the study was to investigate the effect of the new needle tip tracking technology on in-plane infraclavicular plexus blocks.MethodsThe study was a randomized, controlled, observer blinded cross-over trial in 26 healthy volunteers. Two specialists in anesthesiology performed an ultrasound-guided infraclavicular lateral sagittal brachial plexus block with and without needle tip tracking. Primary outcome was procedure time, measured from insertion of the needle until local anesthesia injection was completed. Secondary outcome measures included the number of hand movements and path lengths (assessed by hand motion analysis), block success rate, onset time and duration, discomfort experienced by the volunteers, and the anesthesiologists’ confidence as to whether their block would be successful or not.ResultsMean (SD) procedure time was 183.0 (56.1) s with and 206.8 (56.2) s without needle tip tracking (p=0.16). There were no significant differences in any of the secondary outcomes. Two volunteers’ experienced Horner syndrome after blocks without needle tip tracking. No other adverse events occurred during the study.ConclusionOur study on needle tip tracking for infraclavicular blocks did not reveal any significant differences between active needle tip tracking and the control procedures, neither for primary outcome nor secondary outcome measurements.Trial registration numberNCT03631914

Background In women presenting for caesarean section under spinal anesthesia, continuous measurement of circulatory aspects, such as blood pressure and cardiac output, is often needed. At present, invasive techniques are used almost exclusively. Reliable non-invasive monitoring would be welcome, as it could be safer, less uncomfortable, and quick and easy to apply. We aimed to evaluate whether a non-invasive, finger plethysmographic device, the ccNexFin monitor, can replace invasively measured blood pressure in the radial artery, and whether cardiac output measurements from this device can be used interchangeably with measurements from the mini-invasive LiDCO monitor currently in use at our institution. Methods Simultaneous invasive measurements were compared to ccNexFin in 23 healthy women during elective caesarean section under spinal anesthesia. We used Bland Altman statistics to assess agreement, and polar plot methodology to judge trending abilities with pre-defined limits. Results Mean arterial and systolic pressures showed biases (invasive – ccNexFin) of − 4.3 and 12.2 mmHg, with limits of agreement of − 15.9 – 7.4 and − 11.1 – 35.6, respectively. The ccNexFin trending abilities were within the suggested limits for mean pressure but insufficient for systolic pressure compared to invasive measurements. Cardiac output had a small bias of 0.2 L/min, but wide limits of agreement of − 2.6 – 3.0. The ccNexFin trending abilities compared to the invasive estimated values (LiDCO) were unsatisfactory. Conclusions We consider the ccNexFin monitor to have sufficient accuracy in measuring mean arterial pressure. The limits of agreement for systolic measurements were wider, and the trending ability compared to invasive measurements was outside the recommended limit. The ccNexFin is not reliable for cardiac output measurements or trend in pregnant women for caesarean delivery under spinal anesthesia. Trial registration Registered May 23, 2013, at ClinicalTrials.gov under number NCT01861132.

Background: In women presenting for caesarean section under spinal anaesthesia, continuous measurement of circulatory aspects, such as blood pressure and cardiac output, is often needed. At present, invasive techniques are used almost exclusively. Reliable non-invasive monitors would be welcome, as they could be safer and less uncomfortable, while easy and quick to apply. We aimed to evaluate whether a non-invasive, finger plethysmographic device, the ccNexFin monitor, can replace invasively measured blood pressure in the radial artery, and whether cardiac output measurements from this device can be used interchangeably with measurements from the mini-invasive LiDCO monitor, currently in use at our institution. Methods: Simultaneous invasive measurements were compared with ccNexFin in 23 healthy women during elective caesarean section under spinal anaesthesia. We used Bland Altman statistics for assessing agreement, and polar plot methodology for judging trending abilities with pre-defined limits. Results: Mean arterial and systolic pressures showed biases (invasive – ccNexFin) of -4.3 and 12.2 mmHg, with limits of agreement of -15.9 – 7.4 and -11.1 – 35.6, respectively. The ccNexFin trending abilities were within suggested limits for mean pressure, but insufficient for systolic pressure compared with invasive measurements. Cardiac output had a small bias of 0.2 L/min, but wide limits of agreement of -2.6 – 3.0. The ccNexFin trending abilities compared with the invasive estimated values (LiDCO) were unsatisfactory. Conclusions: We consider the ccNexFin monitor to have sufficient accuracy in measuring mean arterial pressures. The limits of agreement for systolic measurements were wider, and the trending ability, compared with invasive measurements, was outside the recommended limit. The ccNexFin is not reliable for cardiac output measurements or trend in pregnant women for caesarean delivery under spinal anaesthesia.