Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2019
Low temperature increases capillary blood refill time following mechanical fingertip compression of healthy volunteers: prospective cohort study.
Capillary refill time has been accepted as a method to manually assess a patient's peripheral blood perfusion. Recently, temperature has been reported to affect capillary refill time and therefore temperature may interfere with accurate bedside peripheral blood perfusion evaluation. We applied a new method of analysis that uses standard hospital pulse oximetry equipment and measured blood refill time in order to test whether lowered fingertip temperature alters peripheral blood perfusion. ⋯ A generalized linear mixed-effects model revealed that lower temperature (OR 0.63 [95% CI 0.61-0.65], p < 0.001) rather than age (OR 1.00 [0.99-1.01], p = 0.395) was the independent factor most associated with increased blood refill time. Lowered fingertip temperatures significantly increase blood refill time which then returns to baseline when the fingertip is rewarmed. In our limited number of population, we did not find an association with age after the adjustment for the fingertip temperature.
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J Clin Monit Comput · Apr 2019
Suppression of pupillary unrest by general anesthesia and propofol sedation.
The pupil undergoes irregular oscillations when exposed to light. These oscillations, known as pupillary unrest in ambient light, originate from oscillatory activity within the Edinger-Westphal nucleus in the midbrain. The midbrain and upper pons also contain nuclei known to be very sensitive to the effects of anesthetics that play a central role in maintaining wakefulness. ⋯ Pupillary unrest is caused by oscillatory activity within the midbrain that is affected by the state of wakefulness or by hypnotics directly. Increased sedation and general anesthesia reduce and then abolish pupillary unrest as wakefulness decreases. We speculate that midbrain nuclei responsible for wakefulness and pupillary unrest are either communicating or share a similar sensitivity to the effects of commonly used anesthetics.
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J Clin Monit Comput · Apr 2019
Assessing the correct inflation of the endotracheal tube cuff: a larger pilot balloon increases the sensitivity of the 'finger-pressure' technique, but it remains poorly reliable in clinical practice.
The pilot balloon palpation (or 'finger-pressure') method is still widely used to assess the endotracheal tube cuff inflation, despite consistent evidence of its poor sensitivity in recognizing cuff overinflation. It was recently speculated that this may be related to the lower wall tension (due to the smaller radius) of the pilot balloon as compared with the cuff, according to Laplace's law. To verify this hypothesis and, secondarily, to assess whether the use of a 'large' pilot balloon (identical to the cuff) increases the reliability of this technique, 62 anesthetists (41 experienced anesthesiologists and 21 residents) were asked to estimate the pressure of a cuff inflated to 88 mmHg into a simulated trachea by feeling both a usual and a modified 'large' pilot balloon. ⋯ Moreover, 89% of participants (85% of experienced anesthesiologists and 95% of residents) believed that pressure was higher in the 'large' balloon than in the normal one. However, only 32% of participants (51% of experienced anesthesiologists and none of residents) recognized slight overinflation (40 mmHg) after feeling the 'large' balloon. The pilot balloon size affects the sensitivity of the 'finger-pressure' technique, but it remains poorly reliable with a larger pilot balloon.
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J Clin Monit Comput · Apr 2019
Measurement of blood-oxygen saturation using a photoacoustic technique in the rabbit hypoxemia model.
The golden standard method to obtain accurate blood oxygen saturation is blood gas analysis that needs invasive procedure of blood sampling. Photoacoustic technique enables us to measure real-time blood oxygen saturation without invasive procedure. The aim of this study is to use the photoacoustic technique, an optical method, for accurately determining oxygen saturation in vivo. ⋯ The oxygen saturation calculated using calibration curves 1 and 2 showed strong correlations with the reference standard in regression analysis (R = 0.965, 0.964, respectively). The Bland-Altman analysis revealed better agreement and precision with calibration curve 2, whereas there was significant underestimation of values obtained using calibration curve 1. Photoacoustic measurement of oxygen saturation using calibration curve 2 provided an accurate estimate of oxygen saturation, which was similar to that obtained using a portable blood-gas analyzer.
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J Clin Monit Comput · Apr 2019
Influence of tetanic stimulation on the staircase phenomenon and the acceleromyographic time-course of neuromuscular block: a randomized controlled trial.
During neuromuscular monitoring, repeated electrical stimulation evokes muscle responses of increasing magnitude ('staircase phenomenon', SP). We aimed to evaluate whether SP affects time course and twitches' values of an acceleromyographic assessed neuromuscular block with or without previous tetanic stimulation. Fifty adult patients were randomized to receive a 50 Hz tetanic stimulus (S group) or not (C group) before monitor calibration. ⋯ TOFr showed no differences between groups at any time point. T1 at maximum recovery showed a stronger correlation with post-stabilization T1 compared to baseline. (ρ = 0.80 and ρ = 0.85, for C and S groups.) Standard calibration does not ensure twitch baseline stabilization and prolongs onset time of neuromuscular block. TOF ratio is not influenced by SP.