Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2014
Clinical TrialAnalysis of plethysmographic waveform changes induced by beach chair positioning under general anesthesia.
During shoulder surgery, patients typically are placed in the beach chair position. In rare cases, this positioning has resulted in devastating outcomes of postoperative cerebral ischemia (Cullen and Kirby in APSF Newsl 22(2):25-27, 2007; Munis in APSF Newsl 22(4):82-83, 2008). This study presents a method to noninvasively and continuously hemodynamically monitor patients during beach chair positioning by using the photoplethysmograph signal recorded from a commercial pulse oximeter. ⋯ The PPG was more accurate at monitoring the change to beach chair position than blood pressure or heart rate. With vasoactive drugs, pulse-associated PPG oscillations decreased only with phenylephrine while respiration-associated oscillations did not change. Frequency domain analysis of the PPG signal may be a better tool than traditional noninvasive hemodynamic parameters at monitoring patients during beach chair position surgery.
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J Clin Monit Comput · Dec 2014
Clinical TrialNon-invasive cardiac output evaluation in postoperative cardiac surgery patients, using a new prolonged expiration-based technique.
The gold standard methods to measure cardiac output (CO) are invasive and expose the patient to high risks of various complications. The aim of this study is to assess an innovative non-invasive method for CO monitoring in mechanically ventilated patients after cardiac surgery and its agreement with values obtained by thermodilution technique. Continuous monitoring of respiratory gas concentrations and airflow allows the estimation of CO through a newly developed algorithm derived from a modified version of the Fick equation. ⋯ COK shows a mean percentage error of 34 %. In stable mechanically ventilated patients, undergone cardiac surgery, the proposed method is reliable if compared to the thermodilution. Considering the non-invasivity of the technique, further evaluations of its performances are encouraged.
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J Clin Monit Comput · Dec 2014
Lessons learned from closed loops in engineering: towards a multivariable approach regulating depth of anaesthesia.
In this paper is presented a brief state of art regarding the multivariable formulation for controlling the depth of anaesthesia by means of two intravenously administrated drugs, i.e. propofol and remifentanil. In a feasibility study of determining a suitable variable to quantify analgesia levels in patients undergoing cardiac surgery, the bispectral index and an electromyogram-based surrogate variable are proposed as the controlled variables. The study is carried on in the context of implementing a multivariable predictive control algorithm. The simulation results show that such a paradigm is feasible, although it does not guarantee perfect knowledge of the analgesia level-in other words, the variable is not validated against typical evaluations of the pain levels (e.g. clinical scores).
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J Clin Monit Comput · Dec 2014
Individualizing propofol dosage: a multivariate linear model approach.
In the last decades propofol became established as an intravenous agent for the induction and maintenance of both sedation and general anesthesia procedures. In order to achieve the desired clinical effects appropriate infusion rate strategies must be designed. Moreover, it is important to avoid or minimize associated side effects namely adverse cardiorespiratory effects and delayed recovery. ⋯ The results obtained in the test set comprising a broad range of characteristics are satisfactory since the models are able to predict bolus, infusion rates and the effect-site concentrations comparable to those of TCI. Furthermore, comparisons of the effect-site concentrations for dosages predicted by the proposed Linear model and the Marsh model for the same target concentration is achieved using Schnider model and a factorial design on the factors (patients characteristics). The results indicate that the Linear model predicts a dosage profile that is faster in leading to an effect-site concentration closer to the desired target concentration.
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J Clin Monit Comput · Dec 2014
Dead space reduction by Kolobow's endotracheal tube does not justify the waiving of volume monitoring in small, ventilated lungs.
In ventilated preterm infants the flow sensor contributes significantly to the total apparatus dead space, which may impair gas exchange. The aim of the study was to quantify to which extent a dead space reduced Kolobow tube (KB) without flow sensor improves the gas exchange compared with a conventional ventilator circuit with flow sensor [Babylog 8000 (BL)]. In a cross-over trial in 14 tracheotomized, surfactant-depleted (saline lavage) and mechanically ventilated newborn piglets (age <12 h; body weight 705-1200 g) BL and KB was applied alternately for 15 min and blood gases were recorded. ⋯ Furthermore, median paO2 was increased by 4 mmHg (p < 0.05) and O2 saturation was increased by 2.5 % (p < 0.05). No significant changes were seen in the circulatory parameters. In very small, ventilated lungs the use of KB improved the gas exchange; however, the improvement was moderate and does not justify the waiving of volume monitoring.